AU2015200057B2

AU2015200057B2 - Monovalent, bivalent and trivalent anti human respiratory syncytial virus (hRSV) Nanobody constructs for the prevention and/or treatment of respiratory tract infections

Info

Publication number: AU2015200057B2
Application number: AU2015200057A
Authority: AU
Inventors: Erik Depla; Stephanie Staelens; Catelijne Stortelers
Original assignee: Ablynx NV
Current assignee: Ablynx NV
Priority date: 2009-06-05
Filing date: 2015-01-07
Publication date: 2017-02-02
Anticipated expiration: 2030-06-07
Also published as: AU2015200057B9; AU2015200057A1

Abstract

Abstract Amino acid sequences are provided that are directed against and/or that can specifically bind protein F of hRSV, as well as to compounds or constructs, and in particular proteins and polypeptides, that comprise or essentially consist of one or more such amino acid sequences. The amino acid sequences, polypeptides and therapeutic compounds and compositions provided by the invention show an improved stability, less immunogenicity and/or improved affinity and/or avidity for protein F of hRSV. The invention also relates to the uses of such amino acid sequences, polypeptides, compounds or constructs for prophylactic and/or therapeutic purposes.

Description

Monovalent, bivalent and trivalent anti human respiratory syncytial virus (hRSV) Nanobody constructs for the prevention and/or treatment of respiratory tract infections

The present application is a divisional application of Australian Application No. 2010255638, which is incorporated in its entirety herein by reference.

FIELD OF THE INVENTION

The present invention relates to amino acid sequences that are directed against/and or that can specifically bind (as defined herein) protein F of hRSV, as well as to compounds or constructs, and in particular proteins and polypeptides, that comprise or essentially consist of one or more such amino acid sequences (also referred to herein as "amino acid sequence(s) of the invention", "compound(s) of the invention", "construct(s) of the invention" and "poiypeptide(s) of the invention", respectively).

The invention also relates to nucleic acids encoding such amino acid sequences and polypeptides (also referred to herein as "nucleic acid(s) of the invention" or "nucleotide sequence(s) of the invention")·, to methods for preparing such amino acid sequences and polypeptides; to host cells expressing or capable of expressing such amino acid sequences or polypeptides; to compositions, and in particular to pharmaceutical compositions, that comprise such amino acid sequences, polypeptides, compounds or constructs, nucleic acids and/or host cells; and to uses of such amino acid sequences, polypeptides, compounds or constructs, nucleic acids, host cells and/or compositions, in particular for prophylactic and/or therapeutic purposes, such as the prophylactic and/or therapeutic purposes mentioned herein.

Other aspects, embodiments, advantages and applications of the invention will become dear from the further description herein.

BACKGROUND ART

Human respiratory syncytial virus (hRSV) is a member of the Paramyxoviridae family and is an enveloped virus with two main surface glycoproteins that make the spikes of the virus particle. One of these glycoproteins (protein G) is the attachment protein that mediates binding of the virus to the cell surface. The other glycoprotein (protein F or fusion) mediates fusion of the viral and cell membranes, allowing the entry of the viral nucSeocapsid into the cell cytoplasm. Inhibition of the steps mediated by either G or F glycoproteins blocks the initial stages of the infectious cycle and neutralizes virus infectivity. Therefore, antibodies directed against either G or F, and which inhibit their respective activities, may neutralize virus infectivity and may protect against a hRSV infection. The F protein is highly conserved and forms trimeric spikes that undergo conformational changes upon activation. hRSV is the leading cause of severe lower respiratory tract infections (bronchiolitis and pneumonia) in infants and very young children and causes annual epidemics during the winter months. The virus also causes a substantial disease burden among the elderly and adults with underlying cardiopulmonary disorders and/or immunosuppressive conditions are also at risk of severe hRSV disease. The immune response does not prevent re-infections.

There is no vaccine available to prevent hRSV infections. The only drug product available in the market is a humanized monoclonai antibody (Synagis®) directed against one of the viral glycoproteins (protein F) which is used prophylacticaily in children that are at a very high risk of suffering a severe hRSV infection. The restricted use of Synagis® is due, at least in part, to the high cost of this product. There is clearly a need for improved and/or cheaper prophylactic and/or therapeutic agents for the prevention and or treatment of infections by hRSV.

SUMMARY OF THE INVENTION

The present invention provides amino acid sequences (also referred to as "amino acid sequence(s) of the invention"), polypeptides (also referred to as “polypeptide(s) of the invention") and therapeutic compounds and compositions that are directed against protein F of hRSV and that have improved prophylactic, therapeutic and/or pharmacological properties, in addition to other advantageous properties (such as, for example, improved ease of preparation and/or reduced costs of goods), compared to the prior art amino acid sequences and antibodies. These improved and advantageous properties will become dear from the further description herein. Without being limiting, the amino acid sequences, polypeptides and therapeutic compounds and compositions provided by the invention may show an improved stability, less immunogenicity, improved binding to protein F of hRSV, improved affinity and/or avidity for protein F of hRSV, improved efficacy and/or potency for neutralizing hRSV (as defined herein), an increased selectivity for protein F of hRSV and/or they may be capable of partially or preferably totally blocking the interaction of protein F of hRSV with the target host cell and/or its membrane. They may be capabie of neutralizing hRSV by modulating, inhibiting and/or preventing hRSV infectivity, by modulating, inhibiting and/or preventing hRSV fusion with (the cell membrane of) the target host cell, and/or by modulating, inhibiting and/or prevent hRSV entry in the target host cell (as defined herein). They may be cross reactive with and/or capable of neutralizing different strains of hRSV and/or different hRSV escape mutants.

In a first aspect, the present invention provides a number of stretches of amino acid residues (as defined herein) that are particularly suited for binding to a specific epitope on protein F of hRSV. These stretches of amino add residues may be present in, and/or may be incorporated into, an amino add sequence of the invention, in particular in such a way that they form (part of) the antigen binding site of the amino acid sequence of the invention. The resulting amino acid sequences will be capable of binding a specific epitope on protein F of hRSV that lies in, forms part of, or overlaps with (i.e. in the primary or tertiary structure) or is in close proximity to (i.e. in the primary or tertiary structure) antigenic site li on protein F of hRSV (i.e. amino acid residues 250-275 of protein F of hRSV).

Accordingly, in one aspect, the present invention provides amino acid sequences that comprise at least a stretch of amino add residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the present invention provides amino acid sequences that comprise two or more stretches of amino add residues in which one stretch is chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at ieast one stretch is chosen from: c) SEQ ID NO: 98; d) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a), and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Even more preferably, the amino acid sequences of the invention comprise three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence com prising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; or the second stretch of amino acid residues is chosen from the group consisting of: C) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering}; and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and the third stretch of amino acid residues is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of HRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Amino acid sequences comprising one or more of these specific stretches of amino acid residues have shown improved properties such as e.g. improved binding characteristics (suitably measured and/or expressed as a KD-value (actual or apparent), a KA-vaiue {actual or apparent), a k0„-rate and/or a ko!rrate, or alternatively as an iC5!> value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV.

The amino acid sequence of the invention may in particular be a domain antibody (or an amino add sequence that is suitable for use as a domain antibody), a single domain antibody (or an amino acid sequence that is suitable for use as a single domain antibody), a "dAb" (or an amino acid sequence that is suitable for use as a dAb) or a Nanobody® (as defined herein, and including but not limited to a VHH sequence); other single variable domains, or any suitable fragment of any one thereof.

In this respect, the amino acid sequences of the invention may essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDRl to CDR3, respectively), in which CDR2 is chosen from: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference.

These preferred complementarity determining regions (CDR2 sequences) are also referred to as "CDR2(s) of the invention

Preferably, the amino acid sequences of the invention may essentially consist of 4 framework regions (FR1 to FRA, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from the group consisting of: a) SEQ ID NO: 102; or b) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ. ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and at least one of CDR1 or CDR3 is chosen from: CDR1 chosen from the group consisting of: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino add sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3,2 or 1 amino acid difference; or and/or CDR3 chosen from the group consisting of; e) SEQ ID NO: 121; or fj a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance} and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3,2 or 1 amino acid difference.

Even more preferably, the amino add sequences of the invention may essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: CDRl is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino add sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR2 is chosen from the group consisting of: c) SEQ ID NO: 102; or d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEO.ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference. in a specific aspect, the amino acid sequence or Nanobody® of the invention comprises at least SEQ. ID NO: 102. Preferably, the amino acid sequence or Nanobody* of the invention comprises SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

The present invention also provides a number humanized amino acid sequences that are particularly suited for binding protein F of hRSV. The amino acid sequences of the present invention show reduced immunogenicity upon administration to a human subject. In addition, the amino acid sequences of the present invention show other improved properties such as e.g. improved binding characteristics (suitably measured and/or expressed as a KD-vaiue (actuai or apparent), a IQ-vaiue (actual or apparent), a kon-rate and/or a kofrrate, or alternatively as an ICEC value, as further described herein) for protein F of hRSV, improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV compared to their corresponding wild type amino acid sequences (as described in PCT application PCT/EP2009/056975 entitled "Amino acid sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases" filed by Ablynx N.V on 5 June 2009).

Accordingly, in another aspect, the present invention provides amino acid sequences chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence of the invention comprises or essentially consists of SEQ. ID NO: 60-75.

In another aspect, the present invention provides amino acid sequences chosen from the following: a) SEQ ID NO's: 62,65, 67,68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 58,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences of the invention comprise or essentially consists of one of SEQ ID NO's: 62,65,67, 68, 75 and 76.

In yet another aspect, the present invention provides amino acid sequences chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein Fof hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence of the invention comprises or essentially consists of SEQ ID NO: 65. in another preferred aspect, the amino add sequence of the invention comprises or essentially consists of SEQ ID NO: 76.

In another aspect, the present invention provides amino acid sequences chosen from the following: a) SEQ ID NQ's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in a preferred aspect, the amino acid sequence of the invention comprises or essentially consists of SEQ ID NO: 146-153. in another aspect, the present invention provides amino acid sequences chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q} at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; - SEQ ID NO: 152, the amino acid sequence preferably has Glutamic add (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic add (Giu, E) at position 85; (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences of the invention comprise or essentially consist of one of SEQ ID MO's: 146-149 and 151-153.

The present invention provides a number of sequence optimized amino acid sequences and/or Nanobodies® that show increased stability upon storage during stability studies and that are particularly suited for binding protein F of hRSV. The amino acid sequences of the present invention show reduced pyrogiutamate post-translational modification of the N-terminus and hence have increased product stability, in addition, the amino acid sequences of the present invention show other improved properties such as e.g. less immunogenicity, improved binding characteristics (suitably measured and/or expressed as a K0-value (actual or apparent), a KA-value (actual or apparent), a kon-rate and/or a k0f,-rate, or alternatively as an IC5C value, as further described herein) for protein F of hRSV, improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV compared to their corresponding parental amino acid sequences (as described in PCI application PCT/EP2009/056975 entitled "Amino acid sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases" filed by Ablynx N.V on 5 June 2009).

Accordingly, in one aspect of the present invention, amino acid sequences and/or Nanobodies* are provided chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Rabat numbering); and Π) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or i amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of one of SEQ ID NO's: 138-141 and 154-157.

The amino acid sequences and Nanobodies® provided by the invention are preferably in essentially isolated form (as defined herein), or form part of a protein or polypeptide of the invention (also referred to as “polypeptide of the invention" or "protein of the invention"), which may comprise or essentially consist of one or more amino acid sequences or Nanobodies® of the invention and which may optionally further comprise one or more further amino acid sequences or Nanobodies'1' (all optionally linked via Gne or more suitable linkers).

Accordingly, in another aspect, the invention also relates to a protein or polypeptide (also referred to herein as a "polypeptide of the invention", respectively) that comprises or essentially consists of one or more amino acid sequences and/or Nanobodies®' of the invention (or suitable fragments thereof)

For example, and without limitation, the one or more amino acid sequences and/or Nanobodtes® of the invention may be used as a binding unit in such a protein or polypeptide, so as to provide a monovalent, multivalent or muitiparatopic polypeptide of the invention, respectively, ali as described herein. The present invention thus also relates to a polypeptide which is a monovalent construct comprising or essentially consisting of an amino acid sequence or a Nanobody® of the invention. The present invention thus also relates to a polypeptide which is a multivalent polypeptide, such as e.g. a bivalent or trivaient polypeptide. The present invention also relates to a polypeptide which is a multiparatopic polypeptide, such ase.g. a bisparatopicortriparatopic polypeptide. in 3 preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® of the invention (as described above).

In one aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two {preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies6 chosen from amino acid sequences that comprise at least a stretch of amino add residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

In another aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies- chosen from amino acid sequences that comprise two or more stretches of amino acid residues in which one stretch is chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and at least one stretch is chosen from: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO; 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO; 121, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a), and b) should always be present in the amino acid sequence that forms part of the multivalent polypeptide and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Preferred muitivalent (such as bivalent or trivalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® chosen from amino acid sequences that comprise three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; or the second stretch of amino acid residues is chosen from the group consisting of: c) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position S (position 54 determined according to Kabat numbering); and it) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and the third stretch of amino add residues is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Multivalent (such as bivalent ortrivaierttj polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® that essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 3mino acid difference.

Multivalent (such as bivalent or trivalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® that essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from the group consisting of: a) SEG ID NO: 102; or b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SBQ ID NO: 102, provided that: I) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Rabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one of CDR1 or CDR3 is chosen from: CDR1 chosen from the group consisting of: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; or and/or CDR3 chosen from the group consisting of; e) SEQ iD NO: 121; or f) a stretch of amino acid residues that has no more than 3, preferably r.o more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amine acid difference.

Preferably, multivalent (such ss bivalent or trivalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® that essentiaily consist of 4-framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: CDR1 is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as denned herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR2 is chosen from the group consisting of: c) SEQ ID NO: 102; or d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino add difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferabiy no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino add difference. in a specific aspect, the multivalent (such as bivaient or trivalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies* that comprise at least SEQ ID NO: 102, preferably that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

In another aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies0 chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferabiy no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined accordingto Kabai numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies® chosen from the group consisting of SEQ iD NO's: 60-76.

In another aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical} amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NC's: 62, 65,67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65,67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined accordingto Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies8 chosen from the group consisting of SEQ ID NO's; 62,65, 67, 68, 75 and 76. in another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: 1} the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference. in another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies® chosen from the group consisting of SEQ ID NO's: 65 and 76. in another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ. ID NO's: 50-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and it) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three Identical amino acid sequences or Nanobodies^ chosen from the group consisting of SEQ SD NO's: 60-76.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a) SEQ ID NO’s: 62., 65, 67, 68,75 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 62, 65, 67,68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies® chosen from the group consisting of SEQ ID NQ's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amine acid difference with one of SEQ ID NO s: 65 and 75, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Glri, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino add sequences or Nanobodies® chosen from the group consisting of SEQ ID NO's: 65 and 76. A preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO: 62. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO: 65. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO: 76. in another aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of 5EQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proiine (Pro, P} at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies'5' chosen from the group consisting of SEQ ID NO's: 146-153.

In another aspect, the invention provides a multivalent, preferably a bivalent ortrivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies* chosen from the following; a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's; 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Giutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO; 146, the amino add sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO; 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino add sequence preferably has Arginine (Arg, R) at position 83, Glutamic 3cid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO; 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; - SEQ ID NO: 152, the amino add sequence preferably has Glutamic add (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino add sequences or Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-14-9 and 151-153.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies*1 chosen from the following: a) SEQ ID NO's: 146-153; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino add sequences or Nanobodies* chosen from the group consisting of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino add sequences that have no more than 3, preferably no more than 2. more preferably no more than I amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine {Leu, L) at position 108 and in addition Arginine (Arg. R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: ~ SEQ ID NO: 146, the amino acid sequence preferably has Giutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, Rj at position 83, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; - SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino add difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-149 and 151-153.

In another aspect, the invention provides a multivalent, preferably a bivalent ortrivaient polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody6 chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 2nd 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least one amino acid sequence or Nanobody6 chosen from the group consisting of SEQ ID NO's: 138-141 and 154-157. tn another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody8' chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: I) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is a trivalent polypeptide that comprises or essentially consists of at least one amino acid sequence or Nanobody chosen from the group consisting of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 77-79 and 158; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than I amino acid difference with one of SEQ, (D NO's: 77-79 and 158, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, l) at position 78, an Arginine (Arg, R) at position S3 and/or a Glutamic acid (Giu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3,2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise or essentially consist of one of SEQ ID NO's: 77-79 and 153.

In another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 78 and 79; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 78 and 79, provided that: i) the amino add sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and/or a Glutamic acid (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino add difference.

Preferred trivalent polypeptides of the invention comprise or essentially consist of SEQ ID NO: 78 or 79.

In another specific aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 77. (n another specific aspect, the polypeptide of the invention essentially consists of the amino add sequence of SEQ ID NO: 78. In another specific aspect, the polypeptide of the invention essentially consists of the amino add sequence of SEQ ID NO: 79. In another specific aspect the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 158. in another preferred aspect, the invention provides a trivaient polypeptide chosen from the following poiypeptides: a) SEQ. ID NO's: 15S-161; b) poiypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 159-lSl, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proiine (Pro, P) at position 14-, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L} at position 108 (said positions determined according to Rabat numbering); and ill) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference.

Preferred trivaient poiypeptides of the invention comprise or essentially consist of one of SEQ !D NO's: 159-161.

In another preferred aspect, the invention provides a trivaient polypeptide chosen from the following polypeptides: a) SEQ ID NO’s: 159-161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 159-161, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic add (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the polypeptide has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 159, the amino acid sequence or Nanobody® encompassed in said polypeptide preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 160, the amino acid sequence or Nanobody® encompassed in said polypeptide preferably has Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 161, the amino acid sequence or Nanobody* encompassed in said polypeptide preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and is) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the poiypeptide has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise or essentially consist of SEQ ID NO: 159-161.

In another preferred aspect, the invention provides a trivaient polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 142-145 and 162-155; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 142-145 and 1S2-165, provided that: r) the first amino acid sequence or Nanobooy® encompassed in said poiypeptide has an Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3,2 or 1 amino acid difference.

Preferred trivaient polypeptides of the invention comprise or essentially consist of one of SEQ ID NO's: 142-145 and 162-165.

Polypeptides with these sequences show advantageous properties for use as prophylactic, therapeutic and/or pharmacologically active agents such as e.g. improved stability, less immunogenidty, improved binding characteristics (suitably measured and/or expressed as a K5>-value (actual or apparent), a K*-value (actual or apparent), a k0fi-rate and/or a karate, or alternatively as an ICjo value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV.

The invention further relates to compounds or constructs, and in particular proteins or polypeptides (also referred to herein as a ''compound(s) of the invention"} that comprise or essentially consist of one or more amino acid sequences, Nanobodies® and/or polypeptides of the invention (or suitable fragments thereof),, and optionally further comprise one or more other groups, residues, moieties or binding units. As will become dear to the skilled person from the further disclosure herein, such further groups, residues, moieties, binding units or amino acid sequences may or may not provide further functionality to the amino acid sequence, Nanobody® or polypeptide of the invention (and/or to the compound or construct in which it is present) and may or may not modify the properties of the amino acid sequence, Nanobody® and/or polypeptide of the invention. it is also within the scope of the invention to use parts, fragments, analogs, mutants, variants, alleles and/or derivatives of the amino acid sequences and/or polypeptides of the invention, and/or to use proteins or polypeptides comprising or essentially consisting of one or more of such parts, fragments, analogs, mutants, variants, alleles and/or derivatives, as long as these are suitable for the uses envisaged herein. Such parts, fragments, analogs, mutants, variants, alleles and/or derivatives will usually contain (at least part of) a functional antigen-binding site for binding against antigenic site IS on protein F of hRSV; and more preferably will be capable of specific binding to antigenic site H on protein F of hRSV, and even more preferably capable of binding to antigenic site li on protein F of hRSV with an affinity {suitably measured and/or expressed as a K0-value {actual or apparent), a KA-value (actual or apparent), a kori-rate and/or a kotrrate, or alternatively as an 1C30 value, as further described herein) that is as defined herein, Such parts, fragments, analogs, mutants, variants, alleles and/or derivatives will usually also have a hRSV neutralization efficacy and/or potency as defined herein, Some non-limiting examples of such parts, fragments, analogs, mutants, variants, alleles, derivatives, proteins and/or polypeptides will become dear from the further description herein. Additions! fragments or polypeptides of the invention may also be provided by suitably combining {i.e. by linking or genetic fusion) one or more {smaller} parts or fragments as described herein.

The invention also relates to nucleic acids or nucleotide sequences that encode an amino acid sequence of the invention, a Nanobody® of the invention and/or a polypeptide of the invention (or a suitable fragment thereof). Such a nucleic add will also be referred to herein as "nucleic acidfs) of the invention" and may for example be in the form of a genetic construct, as further described herein. Accordingly, the present invention also relates to a nucleic acid or nucleotide sequence that is in the form of a genetic construct.

The invention further relates to a host or host cell that expresses (or that under suitable circumstances is capable of expressing) an amino acid sequence of the invention, a Nanobody* of the invention, a polypeptide of the invention and/or a compound or construct of the invention; and/or that contains a nucleic acid of the invention. Some preferred but non-limiting examples of such hosts or host ceils will become clear from the further description herein.

The invention further relates to a product or composition containing or comprising at least one amino acid sequence of the invention (or a suitable fragment thereof), at least one Nanobody*' of the invention, at least one polypeptide of the invention, at least one compound or construct of the invention, at least one monovalent construct of the invention and/or at least one nucleic acid of the invention, and optionally one or more further components of such compositions known per se, i.e. depending on the intended use of the composition. Such a product or composition may for example be a pharmaceutical composition (as described herein) or a veterinary composition. Some preferred but non-limiting examples of such products or compositions will become clear from the further description herein.

The invention further relates to methods for preparing the amino acid sequences, IManobodies®’, polypeptides, nucieic acids, host cells, products and compositions described herein.

The invention further relates to applications and uses of the amino acid sequences, Nanobodies®', polypeptides, compounds, nucleic acids, host cells, products and compositions described herein, as well as to methods for the prevention and/or treatment of respiratory track infection caused by hRSV. Some preferred but non-iimiiing applications and uses will become clear from the further description herein.

The amino acid sequences, Nanobodies®', polypeptides, compounds and compositions of the present invention can generally be used to block the interaction of protein F of hRSV with the target host cell and/or its membrane, to neutralize hRSV (different hRSV strains and/or escape mutants), to moduiate, inhibit and/or prevent hRSV infectivity (of different hRSV strains and/or escape mutants), to modulate, inhibit and/or prevent fusion (of different hRSV strains and/or escape mutants) with (the cel! membrane of) the target host cell and/or to modulate, inhibit and/or prevent hRSV entry in the target host cel! (of different hRSV strains and/or escape mutants).

As such, the amino acid sequences, Nanobodies*, polypeptides, compounds and compositions of the present invention can be used for the prevention and/or treatment of diseases and disorders associated with hRSV infection. Examples of such diseases and disorders associated with hRSV infection will be dear to the skilled person based on the disclosure herein, and for example include the following diseases and disorders: respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma.

Accordingly, the present invention also relates to a method for the prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma caused by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino acid sequence of the invention, Nanobody® of the invention, polypeptide of the invention, compound or construct of the invention or monovalent construct of the invention, or a composition of the invention.

The invention aiso relates to the use of an amino acid sequence of the invention, a Nanobody® of the invention, a polypeptide of the invention, a compound or construct of the invention or a monovalent construct of the invention in the preparation of a pharmaceutical composition for the prevention and/or treatment of respiratory iiiness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the iung}, pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma; and/or for use in one or more of the methods described herein.

The invention aiso relates to an amino acid sequence of the invention, a Nanobody® of the invention, a polypeptide of the invention, a compound or construct of the invention or monovalent construct of the invention for prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis {inflammation of the small airways in the iung), pneumonia, dyspnea, cough, {recurrent) wheezing and/or asthma.

Other applications and uses of the amino acid sequences, Nanobodies®, polypeptides and compounds and compositions of the invention will become dear to the skilled person from the further disclosure herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1: Competition ELISA: Synagis® Fab competes with purified RSV binding Nanobodies® and Numax Fab for binding to Fim- protein as described in Example 8. Nanobody® 202A5 is sn irrelevant Nanobody® binding HA of influenza.

Fig. 2: Binding of monovalent, bivalent and trivalent Nanobodies® to FTf/- protein as described in Example 10. rig. 3A and B: Potency (RSV neutralization) of monovalent, bivalent and trivalent constructs to neutralize Long and B-l RSV strains as described in Example 11.

Fig. 4: Neutralization assay of RSV Long and the escape mutants R7C2/1; R7C2/11 and R7.936/4 by the monovalent Nanobodies® 7B2 (A), 15H8, (B) NC41 (C) at a concentration range from about 2 μΜ to 6 nM and the trivalent Nanobodies® RSV 400 (D), RSV404 (E), RSV 407 (F) and RSV 403 (G) at a concentration range of about 20 nM to 100 pM. Curve fitting was only done for data of monovalent Nanobodies®.

Fig. 5: Neutralization of RSV Long and RSV B-l strains by trivalent NC41 Nanobody®1 with different linker lengths as described in Example 15.

Fig. 6: Schematic overview of the humanized residues introduced in selected NC41 variants. Dots indicate the presence of the wildtype residue; letters correspond to the humanized residue. Numbering is according to Kabat

Fig. 7: Alignment of preferred humanized Nanobodv® sequences of the invention.

Fig. 8: Neutralization of hRSV Long strain and B-l strain by monovalent and trivaient humanized NC41 variants. In Figure 8A, neutralization by two of the trivaient humanized NC41 variants (RSV414 and RSV426) is compared with their corresponding monovalent Nanobodies®.

Figure 88 shows the neutralization by the trivaient NC41 variants (RSV414, RSV426 and RSV427).

Fig. 8: Neutralization of hRSV Long (A) and B-l (B) strains by RSV407 and RSV434.

Fig, 3.0: Efficacy testing (prophylactic) of RSV4Q7 in cotton rat model as described in Example 21. Rats were intranasslly administered with various concentrations of RSV407 (day -1) 24 hours prior to RSV infection (day 0). The virus titer (left, mean ± sem, n=6) and viral RNA level (right) was determined in iung Savages at the peak level of viremia, being day 4 after infection (*= P<0.05 in two tailed student's t-test versus untreated).

Fig. 12: Efficacy testing (therapeutic) of RSV434 in cotton rat model as described in Example 21. Rats were infected with RSV on day 0 and treated with 0,1,2.4 or 20 mg/kg of RSV4S4 at day 2 and 3 by intranasal instillation (n=6). The virus titer in nasal (A) and lung iavages (B) was determined at the peak level of viremia (day 4 after infection). The horizontal lines show the detection limits.

DETAILED DESCRIPTION OF THE INVENTION

In the present description, examples and claims: a) Unless indicated or defined otherwise, all terms used have their usual meaning in the art, which will be dear to the skilled person. Reference is for example made to the standard handbooks mentioned in paragraph a) on page 46 of WO 08/020079. b) Unless indicated otherwise, the terms "immunoglobulin sequence", "sequence", "nucleotide sequence" and "nucleic acid" are as described in paragraph b) on page 46 of WO 08/020079. c) Unless indicated otherwise, all methods, steps, techniques and manipulations that are not specifically described in detail can be performed and have been performed in a manner known per se, as will be clear to the skilled person. Reference is for example again made to the standard handbooks and the general background art mentioned herein and to the further references cited therein; as well as to for exampie the following reviews Presta, Adv. Drug Deliv. Rev. 2006, 58 (5-6): 640-56; Levin and Weiss, Mol. Biosyst 2006, 2(1): 4S-57; Irving et ak, j. Immunol. Methods, 2001, 248(1-2), 31-45; Schmitz et al., Placenta, 2000, 21 SuppL A, 5106-12, Gonzales etak. Tumour Biol., 2005, 26(1), 31-43, which describe techniques for protein engineering, such as affinity maturation and other techniques for improving the specificity and other desired properties of proteins such as immunoglobulins. d) Amino acid residues will be indicated according to the standard three-letter or one-letter amino acid code. Reference is made to Table A-2 on page 48 of WO 08/020079. e) When a nucleotide sequence or amino acid sequence is said to "comprise" another nucleotide sequence or amino acid sequence, respectively', or to "essentially consist of' another nucleotide sequence or amino acid sequence, this has the meaning given in paragraph i) on pages 51-52 of WO 08/020079. f) The term "in essentially isolated form" has the meaning given to it in paragraph j) on pages 52 and 53 of WO 08/020079. g) The terms "domain" and "binding domain" have the meanings given to it in paragraph k) on page 53 of WO 08/020079. h) The terms "antigenic determinant" and "epitope", which may aiso be used interchangeably herein, have the meanings given to it in paragraph I) on page 53 of WO 08/020079. i} As further described in paragraph m) on page 53 of WO 0S/G20G79, an amino acid sequence (such as a Nanobodv®, an antibody, a polypeptide of the invention, or generally an antigen binding protein or polypeptide or a fragment thereof) that can (specifically) bind to, that has affinity for and/or that has specificity for a specific antigenic determinant, epitope, antigen or protein (or for at least one part, fragment or epitope thereof) is said to be “against" or "directed against" said antigenic determinant, epitope, antigen or protein. j) The term "specificity" has the meaning given to it in paragraph n) on pages 53-56 of WO 08/020079; and as mentioned therein refers to the number of different types of antigens or antigenic determinants to which a particular antigen-binding molecule or antigen-binding protein (such as a Nanobody® or a polypeptide of the invention) molecule can bind. The specificity of an antigen-binding protein can be determined based on affinity and/or avidity, as described on pages 53-55 of WO 08/020079 (incorporated herein by reference), which also describes some preferred techniques for measuring binding between an antigen-binding molecule (such as a Nanobody® or polypeptide of the invention) and the pertinent antigen. Typically, antigen-binding proteins (such as the amino acid sequences, Nanobodies® and/or polypeptides of the invention) will bind to their antigen with a dissociation constant (KD) of 10° to 10'12 moies/liter or less, and preferably 10" to 10'u moles/liter or less and mors preferably 10*s to 10'12 moles/liter (i.e. with an association constant (KA) of 105 to 101? liter/ moles or more, and preferably 10' to 1012 liter/moles or more and more preferably 10s to 101' liter/moles). Any KQ value greater than 101 mol/iiter (or any KA value lower than 104 M'1) liters/mol is generally considered to indicate non-specific binding. Preferably, a monovalent immunoglobulin sequence of the invention wilt bind to the desired antigen with an affinity less than 500 nM, preferably less than 200 nM, more preferably less than 10 nM, such as e.g. between 10 and 5 nM. Specific binding of an antigen-binding protein to an antigen or antigenic determinant can be determined in any suitable manner known per se, including, for example. 5catchard analysis and/or competitive binding assays, such as radioimmunoassays (RIA), enzyme immunoassays (EIA) and sandwich competition assays, and the different variants thereof known per se in the art; as well as the other techniques mentioned herein. As will be clear to the skilled person, and as described on pages 53-56 of WO 08/020079, the dissociation constant may be the actual or apparent dissociation constant. Methods for determining the dissociation constant wiii be clear to the skilled person, and for example include the techniques mentioned on pages 53-56 of WO 08/020079. k) The half-life of an amino acid sequence, compound or polypeptide of the invention can generally be defined as described in paragraph o) on page 57 of WO 08/020079 and as mentioned therein refers to the time taken for the serum concentration of the amino acid sequence, compound or polypeptide to be reduced by 50%, in vivo, for example due to degradation of the amino acid sequence, compound or polypeptide and/or clearance or sequestration of the amino acid sequence, compound or polypeptide by natural mechanisms. The in vivo half-life of an amino acid sequence, compound or poiypeptrde of the invention car, be determined in any manner known per se, such as by pharmacokinetic analysis. Suitable techniques will be clear to the person skilled in the art, and may for example generally be as described in paragraph o) on page 57 of WO 08/02007S. As aiso mentioned in paragraph o) on page 57 of WO 08/020079, the half-life can be expressed using parameters such as the tl/2-aipha, tl/2-beta and the area under the curve (AUC). Reference is for example made to the Experimental Part below, as well as to the standard handbooks, such as Kenneth, A et al: Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists and Peters et ai, Pharmacokinetic analysis: A Practical Approach (1996). Reference is aiso made to "Pharmacokinetics", M Gibaldi & D Perron, published by Marcel Dekker, 2nd Rev. edition (1982). The terms "increase in half-life" or "increased half-life" as also as defined in paragraph o) on page 57 of WO 08/020079 and in particular refer to an increase in the tl/2-beta, either with or without an increase in the tl/2-aipha and/or the AUC or both. l) In respect of a target or antigen, the term "interaction site" on the target or antigen means a site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen that is a site for binding to a receptor or other binding partner, a catalytic site, a cleavage site, a site for allosteric interaction, a site involved in multimerisation (such as homomerizaiion or heterodimerization) of the target or antigen; or any other site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen that is involved in a biological action or mechanism of the target or antigen. More generally, an "interaction site" can be any site, epitope, antigenic determinant, part, domain or stretch of amino acid residues on the target or antigen to which an amino acid sequence or polypeptide of the invention can bind such that the target or antigen (and/or any pathway, interaction, signalling, biological mechanism or biological effect in which the target or antigen is involved) is modulated (as defined herein), m) An amino acid sequence or polypeptide is said to be “specific fod’ a first target or antigen compared to a second target or antigen when is binds to the first antigen with an affinity (as described above, and suitably expressed as a K0 value, KA value, KCff rate and/or rate) that is at least 10 times, such as at least 100 times, and preferably at least 1000 times, and up to 10000 times or more better than the affinity with which said amino acid sequence or polypeptide binds to the second target or antigen. For example, amino acid sequence or polypeptide may bind to the first target or antigen with a KD value that is at least 10 times less, such as at least 100 times less, and preferably at least 1000 times less, such as 10.000 times less or even less than that, than the with which said amino acid sequence or polypeptide binds to the second target or antigen. Preferably, when an amino acid sequence or polypeptide is "specific for" a first target or antigen compared to a second target or antigen, it is directed against (as defined herein) said first target or antigen, but not directed against said second target or antigen. n) The terms “{cross)-blocl<”, "(cross)-blocked" and "(cross)-blocking" are used interchangeably herein to mean the ability of an amino acid sequence or other binding agent (such as a polypeptide of the invention) to interfere with the binding of other amino add sequences or binding agents of the invention to a given target. The extend to which an amino acid sequence or other binding agents of the invention is able to interfere with the binding of another to the target, and therefore whether it can be said to cross-block according to the invention, can be determined using competition binding assays. One particularly suitable quantitative cross-blocking assay uses a Biacore machine which can measure the extent of interactions using surface plasmon resonance technology. Another suitable quantitative cross-blocking assay uses an ELlSA-based approach to measure competition between amino acid sequences or other binding agents in terms of their binding to the target.

The following generally describes a suitable Biacore assay for determining whether an amino acid sequence or other binding agent cross-blocks or is capable of cross-blocking according to the invention, it will be appreciated that the assay can be used with any of the amino acid sequences or other binding agents described herein. The Biacore machine (for example the Biacore 3000) is operated in line with the manufacturer's recommendations. Thus in one crossblocking assay, the target protein is coupied to a CMS Biacore chip using standard amine coupling chemistry to generate a surface that is coated with the target. Typically 200-800 resonance units of the target would be coupled to the chip (an amount that gives easily measurable levels of binding but that is readiiy saturable by the concentrations of test reagent being used). Two test amino acid sequences (termed A* and B*) to be assessed for their ability to cross- block each other are mixed at a one to one molar ratio of binding sites in a suitable buffer to create the test mixture. When calculating the concentrations on a binding site basis the moiecuiar weight of an amino acid sequence is assumed to be the total molecular weight of the amino acid sequence divided by the number of target binding sites on that amino acid sequence. The concentration of each amino acid sequence in the test mix should be high enough to readily saturate the binding sites for that amino acid sequence on the target molecules captured on the Biacore chip. The amino acid sequences in the mixture are at the same molar concentration (on a binding basis) and that concentration would typically be between i.00 and 1.5 micromoiar (on a binding site basis). Separate solutions containing A* alone and Bw alone are also prepared. A* and B* in these solutions should be in the same buffer and at the same concentration as in the test mix. The test mixture is passed over the target-coated Biacore chip and the tota! amount of binding recorded. The chip is then treated in such a way as to remove the bound amino acid sequences without damaging the chip-bound target. Typically this is done by treating the chip with 30 mM HCi for 60 seconds. The solution of A* alone is then passed over the target-coated surface and the amount of binding recorded. The chip is again treated to remove ali of the bound amino add sequences without damaging the chip-bound target. The solution of B* atone is then passed over the target-coated surface and the amount of binding recorded. The maximum theoretical binding of the mixture of A* and B* is next calculated, and is the sum of the binding of each amino acid sequence when passed over the target surface alone, if the actual recorded binding of the mixture is less than this theoretical maximum then the two amino acid sequences are cross-blocking each other. Thus, in general, a cross-blocking amino acid sequence or other binding agent according to the invention is one which will bind to the target in the above Biacore cross-blocking assay such that during the assay and in the presence of a second amino acid sequence or other binding agent of the invention the recorded binding is between 80% and 0.1% (e.g. 80% to 4%) of the maximum theoretical binding, specifically between 75% and 0.1% (e.g, 75% to 4%) of the maximum theoretical binding, and more specifically between 70% and 0.1% (e.g. 70% to 4%) of maximum theoretical binding (as just defined above) of the two amino acid sequences or binding agents in combination, The Biacore assay described above is a primary assay used to determine if amino add sequences or other binding agents cross-block each other according to the invention. On rare occasions particular amino acid sequences or other binding agents may not bind to a target coupled via amine chemistry' to a CMS Biacore chip (this usually occurs when the relevant binding site on the target is masked or destroyed by the coupling to the chip), in such cases cross-blocking can be determined using a tagged version of the target, for example a N-terminal His-tagged version, in this particular format, an anti-His amino acid sequence would be coupled to the Biacore chip and then the His-tagged target would be passed over the surface of the chip and captured by the anti-His amino acid sequence. The cross blocking analysis would be carried out essentially as described above, except that after each chip regeneration cycle, new His-tagged target would be loaded back onto the anti-His amino acid sequence coated surface. In addition to the example given using N-terminal His-tagged target, C-terminal His-tagged target could alternatively be used. Furthermore, various other tags and tag binding protein combinations that are known in the art could be used for such a cross-blocking analysis (e.g. HA tag with anti-HA antibodies; FLAG tag with anti-FLAG antibodies; biotin tag with streptavidin).

The following generally describes an ELISA assay for determining whether an amino acid sequence or other binding agent directed against a target cross-biocks or is capable of crossblocking as defined herein, it will be appreciated that the assay can be used with any of the amino acid sequences (or other binding agents such as polypeptides of the invention) described herein. The general principal of the assay is to have an amino acid sequence or binding agent that is directed against the target coated onto the wells of an ELISA plate. An excess amount of a second, potentially cross-blocking, anti-target amino acid sequence is added in solution (i.e. not bound to the ELISA plate). A limited amount of the target Is then added to the wells. The coated amino acid sequence and the amino acid sequence in solution compete for binding of the limited number of target molecules. The plate is washed to remove excess target that has not been bound by the coated amino acid sequence and to also remove the second, solution phase amino add sequence as well as any complexes formed between the second, solution phase amino acid sequence and target. The amount of bound target is then measured using a reagent that is appropriate to detect the target. An amino acid sequence in solution that is able to cross-block the coated amino acid sequence will be able to cause a decrease in the number of target molecules that the coated amino acid sequence can bind relative to the number of target molecules that the coated amino acid sequence can bind in the absence of the second, solution phase, amino acid sequence. In the instance where the first amino acid sequence, e.g. an Ab-X, is chosen to be the immobilized amino acid sequence, it is coated onto the wells of the ELISA plate, after which the plates are blocked with a suitable blocking solution to minimize non-specific binding of reagents that are subsequently added. An excess amount of the second amino acid sequence, i.e. Ab-Y, is then added to the ELISA plate such that the moles of Ab-Y target binding sites per well are at least 10 fold higher than the moles of Ab-X target binding sites that were used, per well, during the coating of the EL15A plate. Target is then added such that the moles of target added per well are at least 25-fold lower than the moles of Ab-X target binding sites that were used for coating each well. Following a suitable incubation period the ELISA plate is washed and a reagent for detecting the target is added to measure the amount of target specifically bound by the coated antitarget amino acid sequence (in this case Ab-X}. The background signal for the assay is defined as the signal obtained in wells with the coated amino acid sequence (in this case Ab-X), second solution phase amino acid sequence (in this case Ab-Y), target buffer only (i.e. without target) and target detection reagents. The positive control signal for the assay is defined as the signal obtained in wells with the coated amino acid sequence (in this case Ab-X), second solution phase amino acid sequence buffer only (i.e. without second solution phase amino acid sequence), target and target detection reagents. The ELISA assay may be rurt in such a manner so as to have the positive control signal be at least 6 times the background signal. To avoid any artefacts (e.g. significantly different affinities between Ab-X and Ab-Y for the target) resulting from the choice of which amino acid sequence to use as the coating amino acid sequence and which to use as the second (competitor) amino acid sequence, the cross-blocking assay may to be run in two formats: 1) format 1 is where Ab-X is the amino acid sequence that is coated onto the ELISA plate and Ab-Y is the competitor amino acid sequence that is in solution and 2) format 2 is where Ab-Y is the amino acid sequence that is coated onto the ELISA plate and Ab-X is the competitor amino acid sequence that is in solution. Ab-X and Ab-Y are defined as crossblocking if, either in format 1 or in format 2, the solution phase anti-target amine acid sequence is able to cause a reduction of between 60% and 100%, specifically between 70% and 100%, and more specifically between 80% and 100%, of the target detection signal (i.e. the amount of target bound by the coated amino acid sequence) as compared to the target detection signal obtained in the absence of the solution phase anti- target amino acid sequence (i.e. the positive control wells). o) An amino acid sequence is said to be "cross-reactive" for two different antigens or antigenic determinants (such as e.g. serum albumin from two different species of mammal, such as e.g. human serum albumin and cyno serum albumin, such as e.g. protein F of different strains of hRSV, such as e.g. protein F of different escape mutants of hRSV) if it is specific for (as defined herein) both these different antigens or antigenic determinants. p) As further described herein, the total number of amino acid residues in a Nanobody® can be in the region of 110-120, is preferably 112-115, and is most preferably 113. it should however be noted that parts, fragments, analogs or derivatives (as further described herein) of a Nanobody® are not particularly limited as to their length and/or size, as long as such parts, fragments, analogs or derivatives meet the further requirements outlined herein and are also preferably suitable for the purposes described herein. q) As further described in paragraph q) on pages 58 and 59 of WO 08/020079 (incorporated herein by reference), the amino acid residues of a Nanobody® are numbered according to the general numbering for V*H domains given by Kabat et al. ("Sequence of proteins of immunological interest", US Public Health Services, NfH Bethesda, MD, Publication No, 91), as applied to VHH domains from Camelids in the article of Riechmann and Muyldermans, J. Immunol. Methods 2000 Jun 23; 240 (1-2): 185-195 (see for example Figure 2 of this publication), and accordingly FR1 of a Nanobody* comprises the amino acid residues at positions 1-30, CDR1 of a Nanobody* comprises the amino acid residues at positions 31-35, FR2 of a Nanobody® comprises the amino acids at positions 36-49, CDR2 of a Nanobody® comprises the amino acid residues at positions 50-65, FR3 of a Nanobody* comprises the amino acid residues at positions 66-94, CDR3 of a Nanobody®' comprises the amino acid residues at positions 95-102, and FR4of a Nanobody® comprises the amino acid residues at positions 103-113. r) In the context of the present invention "target host cel! (of a virus)" generally refers to a particular cell, which is or is derived from a living subject and which is susceptible to infection by said virus. s) The term "infectivity of a virus", as used herein, refers to the proportion of living subjects that, when exposed to said virus, actually become infected by said virus. t) The term "neutralization of a virus", as used herein, refers to the modulation and/or reduction and/or prevention and/or inhibition of the Infectivity (as defined herein) of a virus by binding of a neutralizing compound to the virion, as measured using a suitable in vitro, cellular or In vivo assay (such as e.g. the microneutralization assay described by Anderson et al. 1985 (J. Clin. Microbiol. 22:1050-1052) and 1988 (J. Virol. 62: 4232-4238), modifications of these assays such as e.g. described in Example 6; a plaque reduction assay as for example described by Johnson et al. 1997 (J. Inf. Dis. 176:1215-1224), and modifications thereof and those mentioned herein). In particular, "neutralizing (a virus)" or "to neutralize (a virus)" may mean either modulating, reducing, preventing or inhibiting the infectivity (as defined herein) of a virus as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) infectivity {as defined herein) of a virus, in the same assay under the same conditions but without the presence of the amino acid sequence, Nanobody* or polypeptide of the invention. u) The term "potency of an amino acid sequence of the invention", "potency of a Nanobody® of the invention", "potency of a polypeptide of the invention", snd/or "potency of compound or construct of the invention”, as used herein, refers to the capacity of said amino acid sequence of the invention, Nanobody® of the invention, polypeptide of the invention, and/or compound or construct of the invention to neutralize a particular virus (such as e.g, hRSV}, to modulate, inhibit and/or prevent infectivity of a virus, to modulate, inhibit and/or prevent fusion of a virus with (the cell membrane of) the target host cell, and/or to modulate, inhibit and/or prevent entry of a virus into the target host cell (as defined herein). The potency may be measured by any suitabie assay known in the art or described herein, such as e.g. the micro-neutralization assays as described in the Example section and/or the assays mentioned in point t) above. vl The term "virus attachment", as used herein, is attachment of a virus (e.g. hRSV) to a target host cell directly (for example by interacting with a viral receptor) or indirectly (for example by mediating the interaction of one or more other proteins or molecules to a viral receptor). w) The term "virus fusion", as used herein, is fusion of a virus (e.g. hRSV) to a target host cell directly (for example by interacting with membrane compounds of the target host cell) or indirectiv (for example by mediating the interaction of one or more other proteins or molecules with membrane compounds of the target host ceil). x) The term "viral entry·" used herein encompasses any viral-mediated biological pathway that is needed to accomplish virion attachment to a target host celi and/or viral fusion with a target host cell. y) A "stretch of amino acid residues" means two or more amino acid residues that are adjacent to each other or in close proximity to each other, i.e. in the primary or tertiary structure of the amino acid sequence. In the context of the present invention, the "stretch of amino acid residues" will be (at ieast partially) responsible for the binding of the amino acid sequence, Nanobody®, polypeptide, compound or construct of the invention to antigenic site II on protein F of hRSV. z) When comparing two stretches of amino acid residues (or two CDR sequences), the term "amino acid difference" refers to an insertion, deletion or substitution of a single amino acid residue on a position of the stretch of amino acid residues (or CDR sequence) specified in b), d) or f), compared to the stretch of amino acid residues (or CDR sequence) of respectively a), c) or e) ; it being understood that the stretch of amino acid residues (or CDR sequence) of b), d) and f) can contain one, two or maximal three such amino acid differences compared to the stretch of amino acid residues of respectively a), c) or e).

The "amino acid difference" can be any one, two or maximal three substitutions, deletions and/or insertions, or any combination thereof, that either improve the properties of the amino acid sequence of the invention or that at least do not detract too much from the desired properties or from the balance or combination of desired properties of the amino acid sequence of the invention. In this respect, the resuiting amino acid sequence of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the amino acid sequence comprising the one or more stretches of amino acid residues without the one, two or maximal three substitutions, deletions and/or insertions, said affinity as measured by surface plasmon resonance; and/or the resulting amino acid sequence of the invention should at least have a potency that is the same, about the same or higher compared to the amino acid sequence comprising the one or more stretches of amino acid residues without the one, two or maximal three substitutions, deletions and/or insertions. The skilled person will generally be able to determine and select suitable substitutions, deletions and/or insertions, or suitable combinations thereof, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible substitutions, deletions or insertions and determining their influence on the properties of the amino acid sequences thus obtained For example, and depending on the host organism used to express the amino acid sequence of the invention, such deletions and/or substitutions may be designed in such a way that one or more sites for post-translational modification (such as one or more glycosylation sites) are removed, as will be within the ability of the person skilled in the art. in a preferred aspect of the invention, the "amino acid difference" is an amino acid substitution. The amino acid substitution may be any one, two or maxima! three substitutions that either improve the properties of the amino acid sequence of the invention or that at least do not detract too much from the desired properties or from the balance or combination of desired properties of the amino acid sequence of the invention, in this respect, the resulting amino acid sequence of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the amino acid sequence comprising the one or more stretches of amino acid residues without t'he one, two or maxima! three substitutions, said affinity as measured by surface plasmon resonance; and/or the resulting amino acid sequence of the invention should at least have a potency that is the same, about the same or higher compared to the amino acid sequence comprising the one or more stretches of amino acid residues without the one, two or maximal three substitutions, deletions and/or insertions. The skilled person will generally be able to determine and select suitable substitutions, based on the disclosure herein and optionally after a limited degree of routine experimentation. which may for example involve introducing a limited number of possible substitutions and determining their influence on the properties of the Nanobodies® thus obtained.

The amino acid substitution in the one or more stretches of amino acid residues may be a conservative amino acid substitution. "Conservative" amino acid substitutions are generally amino acid substitutions in which an amino acid residue is replaced with another amino acid residue of similar chemical structure and which has little or essentially no influence on the function, activity or other biological properties of the resulting amino acid sequence. Such conservative amino acid substitutions are well known in the art, for example from WO 04/037999, G8-A-3 357 758, WO 98/49185, WO 00/46383 and WO 01/09300; and (preferred} types and/or combinations of such substitutions may be selected on the basis of the pertinent teachings from WO 04/037999 as weil as WO 98/49185 and from the further references cited therein.

Such conservative substitutions preferably are substitutions in which one amino add within the following groups (a) - (e) is substituted by another amino acid residue within the same group: (a) small aliphatic, nonpolar or slightly polar residues: Ala, Ser,. Thr, Pro and Gly; (b) polar, negatively charged residues and their (uncharged) amides: Asp, Asn, Giu and Gin; (c) polar, positively charged residues: His, Arg and Lys; (d) large aliphatic, nonpoiar residues: Met, Leu, iie, Vai and Cys; and (e) aromatic residues: Phe, Tyr and Trp.

Particularly preferred conservative substitutions are as follows: Ala into Gly or into Ser; Arg into Lys; Asn into Gin or into His; Asp into Giu; Cys into Ser; Gin into Asn; Giu into Asp; Gly into Ala or into Pro; His into Asn or into Gin; lie into Leu or into Val; Leu into lie or into Val; Lys into Arg, into Gin or into Giu; Met into Leu, into Tyr or into lie; Phe into Met, into Leu or into Tyr; Ser into Thr; Thr into Ser; Trp into Tyr; Tyr into Trp; and/or Phe into Val, into lie or into Leu. The amino acid substitution in the one or more stretches of amino add residues may provide the amino add sequence with increased affinity for binding to protein F of hRSV. This may be done by techniques such as random or site-directed mutagenesis and/or other techniques for affinity maturation known per se, such as e.g. described in WO 09/004065, WO 05/003345, WO 06/023144, EP527809, EP397834.

Without being limiting, rules (partly or fully followed) for substitutions of amino acid residues in the CDRs may be as follows (i.e. substitution with amino acids with similar side chain chemistries): K is substituted by R; R is substituted by K; A is substituted by S or T; S is substituted by A or T; T is substituted by A or S; 1 is substituted by L or V; L is substituted by I or V; V is substituted by I or L; F is substituted by Y; Y is substituted by F; N is substituted by 0; 0 is substituted by N; Q, is substituted by E; E is substituted by Q.; G is substituted by A; M is substituted by L; H, C, W and P are kept constant.

Furthermore, and also without being iimiting, the rules (partly or fully followed) for substitutions of amino acid residues in the CDRs may be alternatively as follows for substitutions at positions 27 to 35 and positions 50 to 53 (using Kabat numbering system), wherein for positions 27 to 35:

Original amino acid residue in position 27 (Kabat numbering used) is substituted by F; G; R; S; 2 out of F, G, R, S; 3 out of F, G, R, S; or all of them, preferably all of them;

Original amino acid residue in position 23 (Kabat numbering used) is substituted by A;!; S; T; 2 out of A, i, S, T; 3 out of A, I, S, T; or all of them, preferably all of them;

Original amino acid residue in position 29 (Kabat numbering used) is substituted by F; G; L; S; 2 out of F, G, L, S; 3 out of F, G, L, S; or ail of them, preferably all of them;

Original amino acid residue in position 30 (Kabat numbering used) is substituted by D; G; S; T; 2 out of D, G, S, T; 3 out of D, G, S, T; or ail of them, preferably all of them;

Original amino add residue in position 31 (Kabat numbering used) is substituted by D; i; N; 5; T; 2 out of D, I, N, S, T; 3 out of D, I, N, S, T; oral! of them, preferably all of them;

Original amino acid residue in position 32 (Kabat numbering used) is substituted by D; l\|;Y; 2 out of D, N, Y; or all of them, preferably all of them;

Original amino acid residue in position 33 (Kabat numbering used) is substituted by A; G; T; V; 2 out of A, G, T, V; 3 out of A, G, T, V; or ail of them, preferably all of them;

Original amino acid residue in position 34 (Kabat numbering used) is substituted by I; M; or all of them, preferably ali of them;

Original amino acid residue in position 35 (Kabat numbering used) is substituted by A; G; S; 2 out of A, G, S; or all of them, preferably ail of them; and positions 50 to 58 if original amino acid sequence has an amino acid sequence in position 52a (Kabat numbering used),

Original amino acid residue in position 50 (Kabat numbering used) is substituted by A; C; 6; 5; T; 2 out of A, C, G, S, T; 3 out of A, C, G, S, I; 4 out of A, C, G, S, T; or all of them, preferably ail of them;

Original amino acid residue in position 51 (Kabat numbering used) is substituted by I; Original amino acid residue in position 52 (Kabat numbering used) is substituted by N; R; S; T; 2 out of N, R, S, T; 3 out of N, R, S, T; or all of them, preferably ai! of them;

Original amino acid residue in position 52a (Kabat numbering used) is substituted by R; S; I; W; 2 out of R, S, T, W; 3 out of R, S, T, W; or aii of them, preferably ali of them;

Original amino add residue in position 53 (Kabat numbering used) is substituted by D; G; N; S; T; 2 out of D, G, N, S, 7; 3 out of D, G, N, S, 7; 4 out of D, 6, N, S, 7; or ail of them, preferably ali of them;

Original amino acid residue in position 54 (Kabat numbering used) is substituted by D; G; or aii of them, preferably ali of them;

Original amino acid residue in position 55 (Kabat numbering used) is substituted by D; G; S; 2 out of D, 6, S; or ali of them, preferably ali of them;

Original amino acid residue in position 56 (Kabat numbering used) is substituted by I; N; R; S; 7; 2 out of I, N, R, S, 7; 3 out of t, N, R, S, 7; 4 out of!, N, R, S, 7; or all of them, preferably all of them;

Original amino acid residue in position 57 (Kabat numbering used) is substituted by 7; Original amino acid residue in position 58 (Kabat numbering used) is substituted by D; H; N; S; Y; 2 out of D, Η, N, S, Y; 3 out of D, Η, N, S, Y; 4 out of D, Η, N, S, Y; or aii of them, preferably ali of them; and wherein for positions 50 to 58 if original amino acid sequence has notan amino acid sequence in position 52a (Kabat numbering used),

Original amino acid residue in position 50 (Rabat numbering used) is substituted by A; G; R; S; 7; 2 out of A, G, R, S, 7; 3 out of A, G, R, S, 7; 4 out of A, G, R, S, 7; or all of them, preferably all of them;

Original amino acid residue in position 51 (Kabat numbering used) is substituted by l; Original amino acid residue in position 52 (Kabat numbering used) is substituted by N; S; T; 2 out of N, 5,7; or aii of them, preferably all of them;

Original amino acid residue in position 53 (Kabat numbering used) is substituted by N; R; S; 7; Y; 2 out of N, R, S, 7, Y; 3 out of N, R, S, 7, Y; 4 out of N, R, S, 7, Y; or all of them, preferably all of them;

Original amino add residue in position 54 (Kabat numbering used) is substituted by D; G; R; S; 2 out of D, G, R, S; 3 out of D, G, R, S; or all of them, preferably all of them;

Original amino add residue in position 55 (Kabat numbering used) is substituted by G;

Original amino add residue in position 55 (Kabat numbering used) is substituted by G; W; R; S; T; 2 out of D, H, R, S, T; 3 out of D, N, R, S, T; 4 out of D, N, R, S, I; or alt of them, preferably all of them;

Original amino add residue in position 57 (Kabat numbering used) is substituted by T;

Original amino add residue in position 58 (Kabat numbering used) is substituted by D; N; T; Y; 2 out of D, N, T, Y; 3 out of D, N, T, Y; or ail of them, preferably ail of them, after which one or more of the potentially useful substitutions (or combinations thereof) thus determined can be introduced into said CDR sequence (in any manner known per se, as further described herein) and the resulting amino acid sequence(s) can be tested for affinity for protein F of hRSV, and/or for other desired properties such as e.g, improved binding characteristics (suitably measured and/or expressed as a Revalue (actual or apparent), a K4-value (actual or apparent), a k0(rrate and/or a li^-rate, or alternatively as an !CS0 value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV. !n this way, by means of a limited degree of trial and error, other suitable substitutions in the CDRs (or suitable combinations thereof) can be determined by the skilled person based on the disclosure herein. The amino acid sequences comprising a stretch of amino acid residues that has one, two or maximal three substitutions, insertions or deletions, and nucleic add sequencesencoding the same, can be provided in any manner known per se, for example using one or more of the techniques mentioned on pages 103 and 104 of WO 08/020079.

The resulting amino add sequences of the invention should preferably bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a KD-vaiue (actual or apparent), a KA-value (actual or apparent), a kcn-rate and/or a ko;rrate, or alternatively as an ICS0 value, as further described herein) that is as defined herein; and/or neutralize hRSV with an efficacy and/or potency that is as defined herein. aa) When comparing two amino acid sequences, the term "amino add difference" refers to an insertion, deletion or substitution of a single amino acid residue on a position of the first amino acid sequence, compared to the second amino acid sequence; it being understood that two amino acid sequences can contain one, two or maximal three such amino add differences.

The "amino acid difference" can be any one, any two or maximal any three substitutions, deletions or insertions in the amino acid sequence, i.e. in one or more of the framework regions or in one or more of the CDRs (which may be in a CDR of the invention (i.e. in CDR2) or in another CDR (i.e. in CDR1, CDR2 or CDR3)), or anv combination thereof, that either improve the properties of the amino acid sequence of the invention or that at least do not detract toe much from the desired properties or from the balance or combination of desired properties of the amino acid sequence of the invention, in this respect, the resulting amino acid sequence of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the amino acid sequence without the one, two or maximal three substitutions, deletions or insertions, said affinity as measured by surface plasmon resonance; and/or the resulting amino acid sequence of the invention should at least have a potency that is the same, about the same or higher compared to the amino acid sequence without the one, two or maximal three substitutions, deletions and/or insertions. The skilled person will generally be able to determine and select suitable substitutions, deletions or insertions, or suitable combinations thereof, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible substitutions, deletions or insertions and determining their influence on the properties of the amino add sequence thus obtained.

In one aspect of the invention, the "amino acid difference" is an amino acid substitution. The amino acid substitution may be any one, two or maximal three substitutions in one or more of the framework regions or in one or more of the CORs (which may be in a CDR of the invention (i.e. in CDR2) or in another CDR (i.e. in CDRi, CDR2 or CDR3)), or any combination thereof, that either improve the properties of the amino acid sequence of the invention or that at (east do not detract too much from the desired properties or from the balance or combination of desired properties of the amino acid sequence of the invention, in this respect, the resulting amino acid sequence of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the amino acid sequence without the one, two or maxima) three substitutions, said affinity as measured by surface piasmon resonance; and/or the resulting amino add sequence of the invention should at least have a potency that is the same, about the same or higher compared to the amino acid sequence without the one, two or maximal three substitutions. The skilled person will generally be able to determine and select suitable substitutions, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible substitutions and determining their influence on the properties of the amino acid sequences thus obtained.

As indicated above, the substitutions, insertions or deletions can be in one or more of the framework regions and/or in one or more of the CDR's. As discussed above (see point z) above J, the amino acid substitution in one or more of the CDRscan be any substitution such as 3 "conservative substitution" {as defined herein), it may be driven by certain rules (as defined herein), and/or it may induce improved properties to the resulting amino acid sequences. When such substitutions, insertions or deletions are made in one or more of the framework regions, they may be made at one or more of the Hallmark residues (as e.g. defined in WO 08/020079; Tables A-3 to A-S) and/or at one or more of the other positions in the framework residues, although substitutions, insertions or deletions at the Hallmark residues are generally less preferred {unless these are suitable humanizing substitutions as described herein). By means of non-limiting examples, a substitution may for example be a conservative substitution {as described herein) and/or an amino acid residue may be replaced by another amino acid residue that naturally occurs at the same position in another VHH domain {see WO 08/020079, Tables A-5 to A-8), although the invention is generally not limited thereto.

Substitutions, insertions or deletions made {preferably) in one or more of the framework regions may be humanizing substitution (i.e. replacing one or more amino acid residues in the amino acid sequence of a naturally occurring VKh sequence (and in particular in the framework sequences) by one or more of the amino add residues that occur at the corresponding posttion(s) in a Vf! domain from a conventional 4-chain antibody from a human being). Some preferred, but non-limiting humanizing substitutions (and suitable combinations thereof) will become clear to the skilled person based on the disclosure herein. Potentially useful humanizing substitutions can be ascertained by comparing the sequence of the framework regions of one of the amino acid sequence of the invention defined in a) with the corresponding framework sequence of one or more closely related human V* sequences, after which one or more of the potentially useful humanizing substitutions (or combinations thereof) thus determined can be introduced into said amino acid sequence of the invention defined in a) (in any manner known per se, as further described herein) and the resulting humanized amino acid sequence can be tested for affinity for protein F of hRSV, for stability, for ease and ievei of expression, and/or for other desired properties defined herein. In this way, by means of a limited degree of trial and error, other suitable humanizing substitutions (or suitable combinations thereof) can be determined by the skilled person based on the disclosure herein.

The humanizing substitutions should be chosen such that the resulting humanized amino acid sequence and/or Nanobody® still retains the favourable properties of Nanobodies® as defined herein. A skilled person will generally be able to determine and select suitable humanizing substitutions or suitable combinations of humanizing substitutions, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible humanizing substitutions and determining their influence on the properties of the Nanobodies® thus obtained.

Generally, as a result of humanization, the amino acid sequence and/or Nanobody® of the invention may become more "human-like", while still retaining the favorable properties of the Nanobodies& of the invention as described herein. As a result, such humanized amino acid sequence and/or Nanobody*·' may have several advantages, such as a reduced immunogenicity, compared to the corresponding naturally occurring VKn domain. Again, based on the disclosure herein and optionally after a limited degree of routine experimentation, the skilled person wiii be able to select humanizing substitutions or suitable combinations of humanizing substitutions which optimize or achieve a desired or suitable balance between the favourable properties provided by the humanizing substitutions on the one hand and the favourable properties of naturally occurring VHh domains on the other hand.

The amino acid sequences and/or Nanobodies® of the invention may be suitably humanized at any framework residue(s), such as at one or more Hallmark residues (as defined herein) or at one or more other framework residues (i.e. non-Haltmark residues) or any suitable combination thereof. One preferred humanizing substitution for Nanobodies® of the "P,R,$-103 group" or the "KERE group" (as defined in WO 08/020079) is Q108 into L108.

Depending on the host organism used to express the amino acid sequence, Nanobodv* or polypeptide of the invention, such deletions and/or substitutions may also be designed in such a way that one or more sites for post-transiationai modification (such as one or more glycosytation sites) are removed, as will be within the ability of the person skilled in the art. Alternatively, substitutions or insertions may be designed so as to introduce one or more sites for attachment of functional groups (as described herein), for example to allow' site-specific pegylation (again as described herein).

As can be seen from the data on the VHh entropy and VHh variability given in Tables A-5 - A-S of WO 08/020079, some amino acid residues in the framework regions are more conserved than others. Generally, although the invention in its broadest sense is not limited thereto, any substitutions, deletions or insertions are preferably made at positions that are less conserved. Also, generally, amino acid substitutions are preferred over amino acid deletions or insertions. Any amino acid substitutions applied to the polypeptides described herein may also be based on the analysis of the frequencies of amino acid variations between homologous proteins of different species developed by Schulz et al., Principles of Protein Structure, Springer-Veriag, 1978, on the analyses of structure forming potentials developed by Chou and Fasman, Biochemistry 13:211,1974 and Adv. EnzymoL, 47:45-149,1978, and on the analysis of hydrophobicity patterns in proteins developed by Eisenberg et ai., Proc. Natl. Acad. Sci. USA 81:140-144,1384; Kyte & Doolittle; J Moiec. Biol 157:105-132,1981, and Goldman ei si.,

Ann. Rev. Biophys. Chem. 15:321-353,1986, ail incorporated herein in their entirety by reference. Information on the primary, secondary and tertiary structure of Nanobodies* is given in the description herein and in the general background art cited above. Also, for this purpose, the crystal structure of a νΗίι domain from a llama is for example given by Desmyter et aL, Nature Structural Biology, Vol. 3, 9, S03 (1996); Spinelli et al., Natural Structural Biology (1996); 3, 752-757; and Decanniere et a!., Structure, Voi. 7,4, 361 (1999). Further information about some of the amino acid residues that in conventional V„ domains form the VH/VL interface and potential cameiizing substitutions on these positions can be found in the prior art cited above.

The amino acid sequences and/or Nanobodies® with one, two or maximal three substitutions, insertions or deletions, and nucleic add sequences encoding the same, can be provided in any manner known perse, for example using one or more of the techniques mentioned on pages 103 and 104 of WO 08/020079.

The resulting amino acid sequences and/or Nanobodies® of the invention should preferably bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a KD-value (actual or apparent), a iv.-value (actual or apparent), a kor-rate and/or a karate, or aiternativeiy as an IC50 value, as further described herein) that is as defined herein; and/or neutralize hRSV with an efficacy and/or potency that is as defined herein, bb) When comparing two polypeptides, the term "amino acid difference” refers to an insertion, deletion or substitution of a single amino acid residue on a position of the first polypeptide, compared to the second polypeptide; it being understood that two polypeptides can contain one, two or maximal three such amino acid differences.

The "amino acid difference" can be any one, any two or maximal three substitutions, deletions or insertions in the polypeptide, i.e. in one or more of the framework regions or in one or more of the CDRs (which may be in a CDR of the invention (i.e. in CDR2) or in another CDR (i.e. in CDR1, CDR2 or CDR3)), or any combination thereof, that either improve the properties of the polypeptide of the invention or that at least do not detract too much from the desired properties or from the balance or combination of desired properties of the polypeptide of the invention, in this respect, the resulting polypeptide of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the polypeptide without the one, two or maximal three substitutions, deletions or insertions, said affinity as measured by surface plasmon resonance; and/or the resulting polypeptide of the invention should at least have a potency that is the same, about the same or higher compared to the polypeptide without the one, two or maximal three substitutions, deletions and/or insertions. The resulting polypeptide should preferably bind to protein F of hRSV with an affinity {suitably measured and/or expressed as a Revalue (actual or apparent), a KA-value {actual or apparent), a kon-rate and/or a ko;rrate, or alternatively as an ICS0 value, as further described herein) that is as defined herein; and/or neutralize hRSV with an efficacy and/or potency that is as defined herein. The skilled person will generally be able to determine and select suitable substitutions, deletions or insertions, or suitable combinations thereof, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible substitutions, deletions or insertions and determining their influence on the properties of the polypeptide thus obtained.

In one aspect of the invention, the "amino add difference" is an amino acid substitution. The amino acid substitution may be any one, any two or maximal any three substitutions in the framework regions or in one or more of the CDRs (which may be in a CDR of the invention (i.e. present in CDR2) or in another CDR (i.e. in CDR1, CDR2 or CDR3)}, or any combination thereof, that either improve the properties of the polypeptide of the invention or that at least do not detract too much from the desired properties or from the balance or combination of desired properties of the polypeptide of the invention. In this respect, the resulting polypeptide of the invention should at least bind protein F of hRSV with the same, about the same, or a higher affinity compared to the polypeptide without the one, two or maximal three substitutions, deletions or insertions, said affinity as measured by surface p'asmon resonance; and/or the resulting polypeptide of the invention should at least have a potency that is the same, about the same or higher compared to the polypeptide without the one, two or maximal three substitutions, deletions and/or insertions. The resulting polypeptide should preferably bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a KD-value (actual or apparent), a IVvalue (actual or apparent), a k^-rate and/or a karate, or alternatively as an iC50 value, as further described herein) that is as defined herein; and/or neutralize hRSV with an efficacy and/or potency that is as defined herein. The skilled person will generally be able to determine and select suitable substitutions, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible substitutions and determining their influence on the properties of polypeptides thus obtained.

As indicated above, the substitutions, insertions or deletions can be in one or more of the framework regions and/or in one or more of the CDR's. As discussed above (see point z)), the substitutions, insertions or deletions in the CDR's may be any possible substitutions, insertions or deletions such as "conservative substitution" (as defined herein), it may be driven by certain rules (as defined herein), and/or it may induce improved properties to the resulting polypeptides.

When such substitutions, insertions or deletions are made in one or more of the framework regions, they may be made at one or more of the Kalimark residues (as e.g. defined in WO 08/020079; Tables A-3 to A-8) and/or at one or more of the other positions in the framework residues, although substitutions, insertions or deletions at the Hallmark residues are generally less preferred (unless these are suitable humanizing substitutions as described herein). By means of non-limiting examples, a substitution may for example be a conservative substitution (as described herein) and/or an amino acid residue may be replaced by another amino acid residue that naturaliy occurs at the same position in another VHri domain (see WO 08/020079, Tables A-5 to A-8), although the invention is generally not limited thereto.

Substitutions, insertions or deletions made (preferably) in one or more of the framework regions may be humanizing substitution. Some preferred, but non-limiting humanizing substitutions (and suitable combinations thereof) will become clear to the skilled person based on the disclosure herein. Potentially useful humanizing substitutions can be ascertained by comparing the sequence of the framework regions of one of the amino add sequences encompassed in the polypeptide of the invention defined in a) with the corresponding framework sequence of one or more closeiy related human VM sequences, after which one or more of the potentially useful humanizing substitutions (or combinations thereof) thus determined can be introduced into said polypeptide of the invention defined in a) {in any manner known per se, as further described herein) and the resulting polypeptide sequence can be tested for affinity for protein F of hRSV, for stability, for ease and level of expression, and/or for other desired properties defined herein. In this way, by means of a 'limited degree of trial and error, other suitable humanizing substitutions (or suitable combinations thereof) can be determined by the skilled person based on the disclosure herein.

The humanizing substitutions should be chosen such that the resulting humanized poiypeptide sequences still retain the favourable properties of Nanobodies® encompassed in the polypeptide as defined herein. A skilled person wili generally be able to determine and select suitable humanizing substitutions or suitable combinations of humanizing substitutions, based on the disclosure herein and optionally after a limited degree of routine experimentation, which may for example involve introducing a limited number of possible humanizing substitutions and determining their influence on the properties of the Nanobodies® encompassed in the polypeptide thus obtained.

Generally, as a result of humanization, the poiypeptide of the invention may become more "human-like", while still retaining the favorable properties of the Nanobodies® of the invention encompassed in the polypeptide as described herein. As a result, such humanized polypeptides may have several advantages, such as a reduced immunogenicity, compared to the polypeptides that encompass corresponding naturally occurring VFF domains. Again, based on the disclosure herein and optionally after a limited degree of routine experimentation, the skilled person will be able to select humanizing substitutions or suitable combinations of humanizing substitutions which optimize or achieve a desired or suitable balance between the favourable properties provided by the humanizing substitutions on the one hand and the favourable properties of naturally occurring VHH domains on the other hand.

Polypeptides of the invention may be suitably humanized at any framework residue(s), such as at one or more Hallmark residues {as defined herein) or at one or more other framework residues (i.e. non-Hallmark residues) or any suitable combination thereof. One preferred humanizing substitution for Nanobodies® of the "P,R,S-103 group" or the "KERE group" is Q10S into L108.

Depending on the host organism used to express the polypeptide of the invention, such deletions and/or substitutions may also be designed in such a way that one or more sites for post-translational modification (such as one or more glycosylation sites) are removed, as will be within the ability of the person skilled in the art. Alternatively, substitutions or insertions may be designed so as to introduce one or more sites for attachment of functional groups (as described herein), for example to allow site-specific pegylation (again as described herein).

As can be seen from the data on the VHh entropy and VHH variability given in Tables A-5 - A-8 of WO 08/020079, some amino acid residues in the framework regions are more conserved than others. Generally, although the invention in its broadest sense is not limited thereto, any substitutions, deletions or insertions are preferably made at positions that are less conserved. Also, generally, amino acid substitutions are preferred over amino acid deletions or insertions. Any amino acid substitutions applied to the poiypeptides described herein may aiso be based on the analysis of the frequencies of amino acid variations between homologous proteins of different species developed by Schulz et a!., Principles of Protein Structure, Springer-Veriag, 1978, on the analyses of structure forming potentials developed by Chou and Fasman, Biochemistry 13: 211,1974 and Adv. Enzymol., 47:45-149,1S78, and on the analysis of hydrophobicity patterns in proteins developed by Eisenberg et al., Proc. Natl. Acad. Sci. USA 81:140-144,1984; Kyte & Doolittle; J Molec. Biol. 157:105-132,198 1, and Goldman et al., Ann. Rev. Biophys. Chem. 15: 321-353,1986, all incorporated herein in their entirety by reference. Information on the primary, secondary and tertiary structure of Nanobodies® is given in the description herein and in the general background art cited above. Also, for this purpose, the crystal structure of a Vhh domain from a llama is for example given by Desmyter et a!., Nature Structural Biology, Vol. 3, 9,803 (1996); Spinelli et al., Natural Structural Biology (1996); 3,752-757; arid Decanniere et al., Structure, Vol. 7,4, 361 (1999). Further information about some of the amino acid residues that in. conventional VH domains form the Vh/Vi interface and potential camelizing substitutions on these positions can be found in the prior art cited above.

The polypeptides with one, two or maximal three substitutions, insertions or deletions, and nucleic acid sequences encoding the same, can be provided in any manner known per se, for example using one or more of the techniques mentioned on pages 103 and 104 of WO 08/020079.

The resulting polypeptides of the invention should preferably bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a l<D-value (actual or apparent), a Revalue (actual or apparent), s k0:,-rate and/or a kofrrate, or alternatively as an ICH value, as further described herein) that is as defined herein; and/or neutralize hRSV with an efficacy and/or potency that is as defined herein. cc) The figures, sequence listing and the experimental part/examples are only given to further illustrate the invention and should not be interpreted or construed as limiting the scope of the invention and/or of the appended claims in anyway, unless explicitly indicated otherwise herein.

For binding to its epitope on protein F of hRSV, an amino acid sequence will usually contain within Sts amino acid sequence one or more amino acid residues or one or more stretches of amino acid residues (as defined herein; i.e. with each "stretch" comprising two or more amino acid residues that are adjacent to each other or in close proximity to each other, i.e. in the primary or tertiary structure of the amino acid sequence) via which the amino acid sequence of the invention can bind to its epitope on protein F of hRSV. These amino acid residues or stretches of amino acid residues thus form the "site" for binding to the epitope on protein F of hRSV (also referred to herein as the "antigen binding site"; as further defined herein).

The present invention provides a number of stretches of amino acid residues (as defined herein) that are particularly suited for binding to antigenic site II on protein F of hRSV (for a description of antigenic sites in the hRSV F protein reference is made to Lopez et al. 1998, J. virol. 72: 6922-6928). These stretches of amino acid residues may be present in, and/or may be incorporated into, an amino acid sequence of the invention, in particular in such a way that they form (part of) the antigen binding site of the amino acid sequence of the invention. The resulting amino acid sequences will bind a specific epitope on protein F of hRSV that lies in, forms part of, or overlaps with (i.e. in the primary or tertiary' structure) or is in dose proximity to (i.e. in the primary or tertiary structure) antigenic site II on protein F of hRSV. Also, the resulting amino acid sequences of the invention will preferably be such that they can compete with Synagis4* for binding to protein F of hRSV; and/or such that they can bind to the same epitope or binding site on protein F of hRSV as Synagis®, or to an epitope dose to said binding site and/or overlapping with said binding site.

The present invention provides a stretch of amino add residues (SEQ ID NO: 102) that is particularly suited for binding to protein F of hRSV. This stretch of amino acid residues (or variants of SEQ ID NO: 102 as defined herein) may be present in, and/or may be incorporated into, an amino acid sequence of the invention, in particular in such a way that they form (part of) the antigen binding site of the amino add sequence of the invention. The stretch of amino acid residues has been generated as CDR2 sequence of a heavy chain antibody or VhH sequence (NC41; SEQ ID NO: 5) that was raised against protein F of hRSV and that was further modified in a library approach to generate humanized NC41 Nanobodies® (as described in the Example section). More in particular, the glycine (Sly, G) residue at position 6 of the CDR2 of NC41 was substituted into an Aspartic acid (Asp, D) residue. Surprisingly, improved binding characteristics (suitably measured and/or expressed as a K&-value (actual or apparent), a KA-value (actual or apparent), a kon-rate and/or a koF-rate, or alternatively as an ICS0 value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV have been observed for amino acid sequences that comprise this stretch of amino acid residues (SEQ ID NO: 102). This stretch of amino acid residues (or variants of SEQ ID NO: 102, as defined herein) are also referred to herein as "CDR2 sequences of the invention",

Accordingly, in one aspect, the present invention provides amino acid sequences that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that i) said stretch of amino add residues has an Aspartic acid (Asp, D) at position 5 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference. in a preferred aspect, the present invention provides amino acid sequences that comprise two or more stretches of amino add residues in which one stretch is chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino 3cid residues that has no more than 3, preferably no more than 2. more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and at least one stretch is chosen from: c) SEQ (D NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of 3mino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more chan 2, more preferably no more than 1 amino add difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a) and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Even more preferably, the amino acid sequences of the invention comprise three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has nc more than 3, preferably no more than 2, more preferably no more than i amino acid difference with SEQ. ID NO: 98, provided that the amino acid sequence comprising said stretch of amine acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino add difference; the second stretch of amino acid residues is chosen from the group consisting of: c) SEQ, ID NO: 102; d} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 5 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and the third stretch of amino acid residues is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Amino acid sequences comprising one or more of the above specified stretches of amino acid residues show improved properties such as e.g. improved binding characteristics (suitably measured and/or expressed as a Κο-value (actual or apparent), a KA-value (actual or apparent), a kon-rate and/or a karate, or alternatively as an 1C» value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV,

More in particular, the amino acid sequences of the invention comprising one or more of the above specified stretches of amino acid residues can bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a Kp-value (actual or apparent}, a KA-value (actual or apparent), a k^-rate and/or a k^-rate, or alternatively as an IC50 value, as further described herein) preferably such that they: bind to protein F of hRSV with a dissociation constant (Kp) σί 1000 nM to 1 nM or iess, preferably 100 nM to 1 nM or iess, more preferably 15 nM to 1 nM or even 10 nM to 1 nM or less; and/or such that they: bind to protein F of hRSV with a k0P-rate of between 104 ΜΎ* to about 10' M'V4, preferably between 10s M'V1 and 107 M'V1, more preferably about 10c M'V1 or more; and/or such that they: bind to protein F of hRSV with a kc<F rate between 10’2 s'1 (tyj=0.69 s} and 1G'4 s’* (providing a near irreversible complex with a ty? of multiple days), preferably between lO'" s‘l arid 10”4 s'1, or lower;

Some preferred IC50 values for binding of the amino acid sequences of the invention to protein F of hRSV will become ciear from the further description and examples herein,

Assays to determine the IC50 include competition assays such as competition ELISA (e.g. competition with Synagis*5 or its Fab fragment) or more preferably neutralization assays such as the microneutralization assay described by Anderson et al. (1985, J. Clin, Microbiol. 22:1050-1052; 1988, J. Virol. 52:4232-4238), modifications of this assay such as e.g. described in Example G, or a piaque reduction assay as for example described by Johnson et si. (1997, J. Inf. Dis. 176:1215-1224), and modifications thereof.

For example, in a competition assay with the Fab fragment of Synagis®, the amino acid sequences of the invention may have IC50 values between 1 nM and 100 nM, preferably between 10 nMand 50 nM, or less.

For example, in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) the amino acid sequences of the invention may have IC50 values between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less, it should be noted that the invention is not limited as to the origin of the amino acid sequence of the invention (or of the nucleotide sequence of the invention used to express it), nor as to the way that the amino acid sequence or nucleotide sequence of the invention is (or has been) generated or obtained. Thus, the amino acid sequences of the invention may be naturally occurring amino acid sequences (from any suitable species} or synthetic or semi-synthetic amino acid sequences. it should be noted that the invention in its broadest sense is not limited to a specific structural roie or function that these stretches of amino acid residues may have in the amino acid sequence of the invention, as long as these stretches of amino acid residues allow the amino acid sequence of the invention to bind to antigenic site 1! on protein F of hRSV with a certain affinity and/or potency (as defined herein). Thus, generally, the invention in its broadest sense comprises any amino acid sequence that is capable of binding to antigenic site I! on protein F of hRSV and that comprises one or more stretches of amino acid residues as defined herein (and in particular s suitable combination of two or more such stretches of amino acid residues) that are suitably linked to each other via one or more further amino acid sequences, such that the entire amino acid sequence forms a binding domain and/or binding unit that is capable of binding to antigenic site fi on protein F of hRSV.

Such an amino acid sequence may, for example, be a suitable "protein scaffold" that comprises at least one stretch of amino acid residues as defined herein (l.e, as part of its antigen binding site). Suitable scaffolds for presenting amino acid sequences will be clear to the skilied person, and for example comprise, without limitation, to binding scaffolds based on or derived from immunoglobulins, protein scaffolds derived from protein A domains (such as Affibodies™}, tendamistat, fibronectin, llpocalin, CTLA-4, T-ceit receptors, designed ankyrin repeats, avimers and PD2 domains (Binz et al. 2005, Nat. Biotech. 23:1257), and binding moieties based on DNA or RNA including but not limited to DNA or RNA aptamers (Ulrich et al. 2006, Comb. Chem. High Throughput Screen 9(8): 619-32).

Again, any amino acid sequence of the invention that comprises one or more of the stretches of amino acid sequences as defined herein for the amino acid sequences of the invention is preferably such that it can specifically bind (as defined herein) to protein F of hRSV, and more in particular such that it can bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a Ku-value (actual or apparent), a KA-value (actual or apparent), a koirrate and/or a k0(r rate, or alternatively as an ICSQ value, as further described herein), that is as defined herein. Any amino acid sequence of the invention that comprises one or more of the stretches of amino acid residues as denned herein for the amino acid sequences of the invention is preferably such that it can neutralize hRSV with a potency (as measured in a suitable assay as defined herein) that is as defined herein.

Furthermore, it will afso be clear to the skilled person that it may be possible to "graft" one or more of the CDR's defined herein for the amino acid sequences of the invention onto other "scaffolds", including but not limited to human scaffolds or non-immunoglobulin scaffolds. Suitable scaffolds and techniques for such CDR grafting will be clear to the skilled person and are well known in the art, see for example US 7,180,370, WO 01/27160, EP 0 605 522, EP 0 460 157, US 7,054,297, Nicaise et al., Protein Science {2004), 13:1882-1891; Ewert et a 1., Methods, 2004 Oct; 34{2):184-199; Kettleborough et at., Protein Eng. 1991 Oct; 4(7): 773-783; O'Brien and Jones, Methods Mol. Biol. 2003: 207:81-100; and Skerra, J. Mol. Recognit. 2000:13:167-187, and Saerens et al., J. Mol. Bioi. 2005 Sep 23;352{3):597-607, and the further references cited therein. For example, techniques known per se for grafting mouse or rat COR's onto human frameworks and scaffolds can be used in an analogous manner to provide chimeric proteins comprising one or more of the CDR sequences defined herein for the amino acid sequences of the invention and one or more human framework regions or sequences.

In one specific, but non-limiting aspect, the amino acid sequence of the invention may be an amino acid sequence that comprises an immunogiobutin fold or an amino add sequence that, under suitable conditions (such as physiological conditions) is capable of forming an immunoglobulin fold (i.e. by folding). Reference is inter alia made to the review by Haiaby et ai. (1999,1. Protein Eng. 12: 563-71). Preferably, when properly folded so as to form an immunogiobutin fold, the stretches or amino acid residues may be capable of property forming the antigen binding site for binding the specific antigenic site If on protein F of hRSV; and more preferably capable of binding to antigenic site II on protein F of hRSV with an affinity (suitably measured and/or expressed as a KD-vaiue factual or apparent), a Revalue (actual or apparent), a kB[,-rate and/or a k0{f-rate, or alternatively as an ICS3 value, as further described herein) that is as defined herein. in another specific, but non-limiting aspect, the amino acid sequences of the invention are immunoglobulin sequences, in particular, but without limitation, the amino acid sequences of the invention may be amino acid sequences that essentially consist of 4 framework regions (FR1 to FR4 respectively) and 3 complementarity determining regions (CDR1 to CDR3 respectively); or any suitable fragment of such an amino acid sequence that still binds antigenic site !i on protein F of hRSV.

In such an amino add sequence of the invention, the framework sequences may be any suitable framework sequences, and examples of suitable framework sequences will be dear to the skilled person, for example on the basis the standard handbooks and the further disclosure and prior art mentioned herein.

The framework sequences are preferably (a suitable combination of) immunoglobulin framework sequences or framework sequences that have been derived from immunoglobulin framework sequences (for example, by humanization or camelization). For example, the framework sequences may be framework sequences derived from a tight chain variable domain (e.g. a Vr sequence) and/or from a heavy chain variable domain (e.g. a VK-sequence). When the amino acid sequence of the invention is a heavy chain variable domain sequence, it may be a heavy chain variable domain sequence that is derived from a conventional four-chain antibody (such as, without limitation, a VH sequence that is derived from a human antibody) or be a so-called VHH-sequence {as defined herein) that is derived from a so-called "heavy chain antibody" {as defined herein), in one particularly preferred aspect, the framework sequences are either framework sequences that have been derived from a VHH-sequence (in which said framework sequences may optionally have been partiaiiy orfuily humanized) or are conventional VH sequences that have been camelized (as defined herein).

For a general description of heavy chain antibodies and the variable domains thereof, reference is inter alia made to the prior arc cited herein, as well as to the prior art mentioned on page 59 of WO Q8/020C7S and to the fist of references mentioned on pages 41-43 of the international application WO 06/040153, which prior art and references are incorporated herein by reference.

The framework sequences may preferably be such that the amino acid sequence of the invention is a domain antibody (or an amino acid sequence that is suitable for use as a domain antibody); is a single domain antibody (or an amino add sequence that is suitable for use as a single domain antibody); is a "dAb" (or an amino add sequence that is suitable for use as a dAb); or is a Nanobody* (including but not limited to VH^ sequence). Again, suitable framework sequences will be dear to the skilled person, for example on the basis the standard handbooks and the further disclosure and prior art mentioned herein.

In particular, the framework sequences present in the amino acid sequences of the invention may contain one or more of Hallmark residues (as defined in WO 08/020079 (Tables A-3 to A-8)), such that the amino add sequence of the invention is a Nanobody®'. Some preferred, but non-limiting examples of (suitable combinations of) such framework sequences will become dear from the further disclosure herein (see e.g. Table A-6). Generally, Nanobodies® (in particular VHH sequences and partially humanized Nanobodies®) can in particular be characterized by the presence of one or more "Hallmark residues" in one or more of the framework sequences (as e.g, further described in WO 08/020079, page 61, line 24 to page 98, line 3),

As already described herein, the amino acid sequence and structure of a Nanobody® can be considered - without however being limited thereto - to be comprised of four framework regions or "PR's", which are referred to in the art and herein as "Framework region 1" or "FR1"; as "Framework region 2" or "FR2"; as "Framework region 3" or "FR3"; and as "Framework region 4" or "FR4", respectively; which framework regions are interrupted by three complementary determining regions or "CDR's", which are referred to in the art as "Complementarity Determining Region l"or "CDR1"; as "Complementarity Determining Region 2" or "CDR2"; and as "Complementarity Determining Region 3” or"CDR3", respectively. Some preferred framework sequences and CDR's {and combinations thereof) that are present in the Nanobodies* of the invention are as described herein.

Thus, generally, a Nanobody® can be defined as an amino acid sequence with the {general) structure FR1 - CDR1 - FR2 - CDR2 - FR3 - CDR3 - FR4 in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDRX to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and in which one or more of the Hatlmark residues are as further defined herein.

In this respect, the amino acid sequences of the invention may essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ JO NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 {position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

These preferred complementarity determining regions (CDR2 sequences) are also referred to as "CDR2(sj of the invention".

Preferably, the amino acid sequences of the invention may essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from the group consisting of: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than I amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic add (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein f of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one of CDR1 or CDR3 is chosen from: CDR1 chosen from the group consisting of: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and/or CDR3 chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Even more preferabiy, the amino acid sequences of the invention may essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: CDR1 is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferabiy no more than 2, more preferabiy no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hflSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; or and CDR2 is chosen from the group consisting of. c) SEO, iD NO; 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID MO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 5 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

In a specific aspect, the amino acid sequence or Nanobody® of the invention comprises at ieast SEQ ID NO: 102.

In another specific aspect, the amino acid sequence or Nanobody* of the invention comprises at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no mors than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; c) SEQ ID NO: 121; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ iD NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference.

Preferably, the amino acid sequence or Nanobody® of the invention comprises at least SEQ ID NO: 102 and at least two stretches of amino acid residues {CDR sequences) in which one stretch is chosen from the group consisting of the stretches of amino acid residues defined in a) and b) and in which the other stretch is chosen from the group consisting of the stretches of amino acid residues defined in c) and d). in another specific aspect, the amino acid sequence or Nanobody® of the invention comprises at least SEQ iD NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

Preferably, the amino acid sequence or Nanobody® of the invention comprises SEQ ID NO: 98, SEQ ID NO; 102 and SEQ ID NO: 121.

Preferred combinations of CDR1, CDR2, and CDR3 sequences are also shown in Tabie A-6.

The amino acid sequences of the invention may essentially consists of a heavy chain variable domain sequence that is derived from a conventional four-chain antibody or may essentially consist of a heavy chain variable domain sequence that is derived from heavy chain antibody. The amino acid sequences of the invention may essentially consists of a domain antibody (or an amino acid sequence that is suitable for use as a domain antibody), of a single domain antibody (or an amino acid sequence that is suitable for use as a single domain antibody), of a “dAb11 (or an amino acid sequence that is suitable for use as a dAb) or of a Nanobody®.

For a general description of (single) domain antibodies, reference is also made to the prior art cited above, as wet! as to EP 0 368 684. For the term "dAb's", reference is for example made to Ward st al. (1989, Nature 341:544-6), to Holt et al., 2003, Trends Biotechnol. 21:484-490; as weli as to for example WO 06/030220, WO 06/003388 and other published patent applications of Domantis Ltd., it should also be noted that, although less preferred in the context of the present invention because they are not of mammalian origin, single domain antibodies or single variable domains can be derived from certain species of shark (for example, the so-called "IgNAR domains", see for example WO 05/18629).

In particular, the amino acid sequence of the invention may essentially consist of or may be a Nanobody® (as defined herein) or a suitable fragment thereof. [Note: Nanobody% Nanobodies6 and Nanoclone p are registered trademarks of Ablynx N. V.} A Nanobody® can be defined as an amino acid sequence with the (general) structure FR1 - CDP.l - FR2 - CDK2 - FR3 - CDR3 - FR4 in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and in which one or more of the Baltmark residues are as defined in WO 08/020079 (Tables A-3 to A-8).

More in particular, a Nanobody® can be an amino acid sequence with the (general) structure FR1 - CDR1 - FR2 - CDR2 - FR3 - CDR3 - FR4 in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3, respectively, and which: i) have at least 80% amino acid identity with at least one of the amino acid sequences of SEQ !D NO's: 60-76,138-141 and 146-157 (see Table A-4), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded, in this respect, reference is also made to Table A-6, which lists the framework 1 sequences (SEQ ID NO's: 81-97 and 166), framework 2 sequences (SEQ ID NO's: 99-100), framework 3 sequences (SEQ ID NO's: 103-120 and 167-168) and framework 4 sequences (SEQ ID NO's: 123 and 169) of the Nanobodies® of SEQ ID NO's: 60-76,138-141 and 146-157 (see Table A-4); and in which: it) preferably one or more of the amino acid residues at positions 11, 37, 44, 45, 47, S3, 84, 103,104 and 108 according to the Rabat numbering are chosen from the Hallmark residues mentioned in Table A-3 to Table A-8 of WO 08/020079.

For a further general description of Nanobodres®, reference is made to the prior art cited herein, such as e.g. described in WO 08/020079 {page 16),

Such Nanobodies® may be derived in any suitable manner and from any suitable source, and may for example be naturally occurring sequences (i.e. from a suitable species of Cametid) or synthetic or semi-synthetic amino acid sequences.

Again, such Nanobodies® may be derived in any suitable manner and from any suitable source, and may for example be naturally occurring νΗμsequences (i.e. from a suitable species of Camelid) or synthetic or semi-synthetic amino acid sequences, including but not limited to "humanized" {as defined herein) Nanobodies®, "camelized" (as defined herein) immunoglobulin sequences (and in particular camelized heavy chain variable dpmain sequences), as well as Nanobodtes* that have been obtained by techniques such as affinity maturation (for example, starting from synthetic, random or naturally occurring immunoglobulin sequences), CDR grafting, veneering, combining fragments derived from different immunoglobulin sequences, PCR assembly using overlapping primers, and similar techniques for engineering immunoglobulin sequences well known to the skilled person; or any suitable combination of any of the foregoing as further described herein. Also, when a Nanobody* comprises a VttH sequence, said Nanobody® may be suitably humanized, as further described herein, so as to provide one or more further (partially or fully) humanized Nanobodies* of the invention. Similarly, when a Nanobody® comprises a synthetic or semi-synthetic sequence (such as a partiaily humanized sequence), said Nanobody® may optionally be further suitably humanized, again as described herein, again so as to provide one or more further (partially or fully) humanized Nanobodies* of the invention.

In particular, humanized Nanobodies* may be amino acid sequences that are as generally defined for Nanobodies® in the previous paragraphs, but in which at least one amino acid residue is present (and in particular, in at least one of the framework residues) that is and/or that corresponds to a humanizing substitution (as defined herein). Some preferred, but non-iimiting humanizing substitutions (and suitable combinations thereof) will become clear to the skilled person based on the disclosure herein, in addition, or alternatively, other potentially useful humanizing substitutions can be ascertained by comparing the sequence of the framework regions of a naturally occurring sequence with the corresponding framework sequence of one or more closely related human VV? sequences, after which one or more of the potentially useful humanizing substitutions (or combinations thereof) thus determined can be introduced into said VHH sequence (in any manner known per se, as further described herein) and the resulting humanized Vm, sequences can be tested for affinity for the target, for stability, for ease and ieve) of expression, and/or for other desired properties. In this way, by means of a limited degree of trial and error, other suitable humanizing substitutions (or suitable combinations thereof) can be determined by the skilled person based on the disclosure herein. Also, based on the foregoing, (the framework regions of) a Nsnobody® may be partially humanized or fully humanized.

In this respect, some preferred Nanobcdies® of the invention are Nanobodies® which specifically bind (as further defined herein) protein F of hRSV and which: i) are a humanized variant of the amino acid sequence with SBQ iD NO: 5 (see Table A-l); and/or ii) have at least 80% amino acid identity with at least one of the amino acid sequences of SHQ ID NO: 5 (see Table A-l) and/or at least one of the amino acid sequences of SEQ ID NO's: 60-76, 138-141 and 146-157 (see Table A-4), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded; and in which:

Hi) preferably one or more of the amino acid residues at positions 11, 37, 44,45,47, 83, 84, 103, 104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table A-3 to Table A-8 of WO 08/020079.

The present invention provides a number of humanized and/or sequence optimized amino acid sequences and/or Nanobodies® that are particularly suited for binding protein F of hRSV. Therefore, in one aspect of the present invention, amino acid sequences and/or Nanobodies® are provided chosen from the following: 3} SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amine acid sequence without the 3,2 or 1 amino acid difference. in a preferred aspect, the amino acid sequence and/or Nanobody* of the invention comprises or essentially consists of one of SEQ ID NO's: 60-76. in another aspect, the present invention provides amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68,75 and 76; b} amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequences and/or Nanobodies® are chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 75; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Preferred amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of one of SEQ ID NO's: 62, 65, 67, 68,75 and 76. in yet another aspect, the present invention provides amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 75; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: ί) the amino acid sequence has an Aspartic acid {Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, Lj at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequences and/or Nanobodies* are chosen from the foliowing: a) SEQ ID NO's;: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one ofSEQ !D NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and Π) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Preferably, the amino acid sequence and/or Nanoboay* of the invention comprises or essentially consists of SEQ ID NO: 65. In another preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ ID NO: 76. In another preferred aspect, the amino add sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ. ID NO: 76.

The present invention also provides a number of humanized and/or sequence optimized amino acid sequences and/or Nanobodies0 that are chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one ofSEQ !D NO's: 146-153, provided that: 1) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of one of SEQ ID NO's: 146-153. in another aspect, the present invention provides amino add sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than i amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (leu, L) at position 10S; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and/or Gfutamine (Gin, Q) at position 105; ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. !n a preferred aspect, the amino acid sequences and/or Nanobodies® are chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino add sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, 0} at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic add (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; - SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic add (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of one of SEQ ID NO's: 146-149 and 151-153.

The amino acid sequences and/or Nanobodies® of the present invention show reduced immunogenicity upon administration to a human subject. In addition, the amino acid sequences and/or Nanobodies® of the present invention show improved binding characteristics (suitably measured and/or expressed as a K0-vaiue {actual or apparent), a KA-value (actual or apparent), a karate and/or a karate, or alternatively as an ICSo value, as further described herein) for protein F of hRSV compared to their corresponding parental amino acid sequences (as described in PCT application PCT/EP2009/056975 entitled "Amino add sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases" filed by Ablynx N.V on 5 June 2009).

During the production of the Nanobodies of the invention, a high level of pyre glutamate {pGlu} on the amino terminus was detected by RP-HPLC. Levels of more than 15% pGIti were detected following fermentation and the level of pGlu were steadily increasing upon storage during stability studies. Such a modification ieads to heterogeneity of the final product and needs to be avoided. The controi/preveniion of pGlu formation is therefore critical to keep therapeutic proteins within their set specifications. Specific liquid formulations and/or storage conditions are needed for proteins with an N-terminal Glutamic acid thus minimizing the formation of pyro-Glutamic acid.

In the present invention, the possibility of pGlu post-transiational modification of the N-terminus was eliminated by changing the N-terminal Giutamic acid (£) (HOOC-{CH2}2 -protein) into an Aspartic acid ¢0) [H00C-CH2 -protein) which lead to increased product stability. Accordingly, tne present invention also relates to amino acid sequences and Nanobodies as described above wherein the Glutamic add at position 1 (said position determined according to Kabat numbering) is changed into an Aspartic acid.

The present invention provides a number of sequence optimized amino acid sequences and/or Nanobodies* that show increased stability upon storage during stability studies. Therefore, in one aspect of the present invention, amino acid sequences and/or Nanobotiies® are provided chosen from the following: a} SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i) the amino add sequence has a Aspartic add (Asp, D) at position 1 (said position determined according to Kabat numbering); and is) the amino add sequence binds protein F of bRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in a preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of one of SEQ ID NO's: 138-141 and 154-157.

In another aspect, the amino acid sequences and/or Nanobodies* of the invention comprise or essentially consist of SEQ ID NO: 5, wherein position 1 (Giu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies* of the invention comprise or essentially consist of SEQ ID NO: 62, wherein position 1 (Glu) has been changed Into Asp. in another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 65, wherein position 1 (Giu) has been changed into Asp,

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 76, wherein position 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of one of SEQ ID NO's: 146-153, wherein position 1 (Giu) has been changed into Asp.

Preferably, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ ID NO: IBS. tn another preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ ID NO: 139. In another preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ ID NO: 140. in another preferred aspect, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consists of SEQ ID NO: 141. in another preferred aspect, the amino acid sequence and/or Nanobody* of the invention comprises or essentially consists of one of SEQ ID NO's: 154-157.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaiSLeu, A!al4Pro, Serl9Arg, lie20Leu, Glu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGIn, GlnlOSLeu and Giy54Asp, in another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three, four, five, six, seven, eight or nine) amino add residues have been mutated selected from the following: VaiSLeu,

Alal4Pro, Glu44Gly, Giy78Leu, AlaSSArg, Asp85Glu, ArglOSGIn, GlnlOSLeu and GiyS4Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Atal4Pro, Serl9Arg, !le20Leu and GlnlOSLeu. in another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three, four, five, six or seven) amtno acid residues have been mutated selected from the following: A!al4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSBGlu, ArglOSGIn and Glnl08Leu.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO; 5, wherein one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: ValSLeu, Alal4Prc, Serl9R, lle20Leu, Glu44Giy, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGiu, ArglOSGln, Glnl08Leu and 6iy54Asp, and wherein position 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: ValSLeu, AlalAPro, Giu44Gly, Gly7SLeu, A!a83Arg, AspSSGiu, ArglOSGln, GlnlOSLeu and Gly54Asp, and wherein position 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three or four) amino add residues have been mutated selected from the following: Aial4Pro, Serl9Arg, llelOLeu and Ginl08Leu, and wherein position 1 (Giu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies1® of the invention comprise or essentially consist of SEQ ID NO: 5, wherein one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, ile20Leu, AlaB3Arg, AspSSGiu, ArglOSGin and GinlOSLeu, and wherein position 1 (Giu) has been changed into Asp.

Preferably, the amino acid sequence and/or Nanobody® of the invention comprises or essentially consist of SEQ ID NO: 5, wherein following amino acid residues have been mutated:

ValSLeu, Alal4Pro, Glu44Gly, Gly78Leu, AlaSBArg, AspSSGiu, ArglOSGln and Ginl08Leu;

Ala83Arg, AspSSGiu, ArglOSGln and GlnlOSLeu;

Gly78Leu, AlaSBArg, AspSSGiu and ArglOSGln;

ValSLeu, A!al4Pro, 6lu44Gly, Gly73Leu, AlaS3Arg, Asp856lu, ArglOSGln, Glnl08Leu and

Giy54Asp;

AlaSBArg, Asp85Giu, ArglOSGln, GlnlOSLeu and Gly54Asp;

Gly7SLeu, Aia83Arg, Asp85Glu, ArglOSGln and Gly54Asp;

Gly54Asp;

Alal4Pro, Serl9Arg, He20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, IIe20Leu, Glnl08Leu and Aia83Arg;

Alal4Pro, Serl9Arg, lie20Leu, Glnl08Leu and AspSSGiu;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Lsu and Argl.05Gln;

Alal4Pro, Serl9Arg, lle20Leu, Ginl08Leu, AlaS3Arg and AspSSGiu;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AlaSBArg and ArglOSGln;

Alal4Pro, Serl9Arg, lls20Leu, Glnl08Leu, AspSSGiu and ArglOSGln;

Alal4Pro, SerlSArg, lle20Leu, Glnl08Leu, AlaS3Arg, Asp85Glu and ArglOSGln;

GlulAsp;

GiulAsp, Val5Leu, Atal4Pro, Glu44Gly, Gly78Leu, Aia83Arg, AspSSGIu, ArglOSGln and Glnl08Leu;

GiulAsp, AlaS3Arg, Asp85Glu, ArglOSGln and GlnlOSLeu;

GiulAsp, Gly78Leu, Ala83Arg, AspSSGIu and Argl05Gln;

GiulAsp, ValSLeu, Alal4Pro, Giu44Giy, Giy78Leur AlaSBArg, AspSSGIu, Argl05Gln, GlnlOSLeu and Gly54Asp;

GiulAsp, Aia83Arg, Asp85Glu, ArglOSGln, Glnl08Leu and Gly54Asp;

GiulAsp, Gly78leu, AlaS3Arg, AspSSGIu, ArglOSGln and Gly54Asp;

GiulAsp and Gly54Asp;

GiulAsp, Alsl4Pro, SerlSArg, ISe20Leu and GlnlOSLeu;

GiulAsp, Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and Ata83Arg;

GiulAsp, A!al4Pro, SerlSArg, lie20Leu, Ginl08Leu and AspSSGIu;

GiulAsp, Alal4Pro, Serl9Arg, !le20Leu, Glnl08Leu and ArglOSGln;

GiulAsp, A!al4Pro, SerlSArg, lle20Leu, Glnl08Leu, AlaS3Arg and AspSSGIu;

GiulAsp, Aial4Pro, 5erl9Arg, lie20Leu, GlnlOSLeu, ASaSBArg and ArglOSGln;

GiulAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AspSSGIu and ArglOSGln; or GiulAsp, Aial4Pro, Serl9Arg, Ue20Leu, GlnlOSLeu, Aia83Arg, AspSSGIu and ArglOSGln.

The amino add sequences and/or Nanobodies® of the present invention show improved properties such as e.g. improved stability, less immunogenicity, improved binding characteristics (suitably measured and/or expressed as a KD-value (actual or apparent), a K-value (actual or apparent), a Iwrate and/or a kofrrate, or alternatively as an IC;o value, as further described herein), improved affinity and/or improved avidity for protein F of hRSV and/or improved efficacy and/or potency for neutralizing hRSV compared to their corresponding wild type amino acid sequences (as described in PCI application PCT/EP2009/056975 entitled "Amino add sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases" filed by Ablynx N.V on 5 june 2009).

More in particular, the amino acid sequences and/or Nanobodies® of the invention can bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a Kr,-value (actual or apparent), a KA-value (actual or apparent), a ke,,-rate and/or a kofrrate, or alternatively as an IC^ value, as further described herein) preferably such that they: bind to protein F of hRSV with a dissociation constant (Kc) of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or !ess, more preferably 15 nM to 1 nM or even 10 nM to 1 nM or iess; and/or such that they: bind to protein F of hRSV with a iwrate of between 104 ivT's'1 to about 10' M'V1, preferably between 10’ IVT's'1 and 107 M’V1. more preferably about 10° M_is' or mors; and/or such that they: bind to protein F of hRSV with a k0ff rate between IQ'4 s'4 (ti/v=0.69 s) and 10" s'4 (providing a near irreversible complex with a t1/7 of multiple days), preferably between 10 "’ s'1 and 10J s'3, or lower;

Some preferred ICS0 values for binding of the amino acid sequences of the invention to protein F of hRSV will become clear from the further description and examples herein.

Assays to determine the IC50 include competition assays such as competition ELISA (e.g. competition with Synagis® or its Fab fragment) or more preferably neutralization assays such as the microneutralization assay described by Anderson et a!. (1985, J. Clin. Microbiol. 22:1050-1052; 1988, j. Virol. 62: 4232-4238), modifications of this assay such as e.g. described in Example 6, or a plaque reduction assay as for example described by Johnson et ai. (1997, J. Inf. Dis. 176:1215-1224), and modifications thereof.

For example, in a competition assay with the Fab fragment of Synagis®, the amino acid sequences of the invention may have IC50 values between 1 nM and 100 nM, preferably between 10 nM and 50 nM, or less.

For example, In a microneutralization assay on hRSV Long (such as e.g. described in Example 6) the amino acid sequences of the invention may have IC50 values between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

The amino acid sequences and Nanobodies® provided by the invention are preferably in essentially isolated form (as defined herein), or form part of a polypeptide of the invention (also referred to as "polypeptide of the invention" or "construct of the invention"; both are used interchangeably), which may comprise or essentially consist of one or more amino acid sequences or Nanobodies® of the invention and which may optionally further comprise one or more further amino acid sequences or Nanobodies® (all optionally linked via one or more suitable linkers).

Accordingly, in another aspect, the invention relates to a polypeptide (also referred to herein as a "polypeptide of the invention"} that comprises or essentially consists of one or more amino acid sequences or Nanobodies® of the invention (or suitable fragments thereof).

The process of designing/selecting and/or preparing a polypeptide of the invention, starting from an amino acid sequence or Nanobody® of the invention, is also referred to herein as "formatting” said amino acid sequence or Na nobody® of the invention; and an amino acid sequence or Nanobody® of the invention that is made part of a polypeptide of the invention is said to be "formatted" or to be "in the format of said polypeptide of the invention. Examples of ways in which an amino acid sequence or Nanobody® of the Invention can be formatted and examples of such formats will bs clear to the skilled person based on the disclosure herein; and such formatted amino acid sequences or Nanobodies® form a further aspect of the invention.

For example, and without limitation, the one or more amino acid sequences or Nanobodies® of the invention may be used as a binding unit in such a polypeptide, which may optionally contain one or more further amino acid sequences that can serve as a binding unit (i,e. against the same or another epitope on protein F of hRSV and/or against one or more other antigens, proteins or targets than protein F of hRSV), so as to provide a monovaient, multivalent, muitiparatopic or multispecific polypeptide of the invention, respectively, all as described herein. The present invention thus also relates to a polypeptide which is a monovalent polypeptide or construct comprising or essentially consisting of an amino add sequence or Nanobody® of the invention. The present invention thus also reiates to a polypeptide which is a multivalent polypeptide or construct, such as e.g. a bivalent or trivaient polypeptide or construct. The present invention also relates to a polypeptide which is a multispecific polypeptide or construct, such as e.g. a bispecific or trispecific polypeptide or construct. The present invention aiso relates to a polypeptide which is a muitiparatopic polypeptide or construct, such as e.g. a bisparatopic or triparatopic polypeptide or construct.

Accordingly, in a preferred, but non-limiting aspect, the amino acid sequence or Nanobody* of the invention comprises at least one further amino acid sequence or Nanobody®, so as to provide a polypeptide of the invention that comprises at least two, such as two, three, four, five or more amino acid sequences or Nanobodies®, in which said amino acid sequences or Nanobodies® may optionally be linked via one or more linker sequences (as defined herein). Polypeptides of the invention that comprise two or more amino acid sequences or Nanobodies®, of which at least one, and preferably alt, is/are an amino acid sequence or Nanobody® of the invention, will aiso be referred to herein as "multivalent" polypeptides of the invention, and the amino acid sequences or Nanobodies® present in such polypeptides will also be referred to herein as being in a "multivalent format". For example a "bivalent" polypeptide of the invention comprises two amino acid sequences and/or Nanobodies®, optionally linked via a linker sequence, whereas a "trivaient" polypeptide of the invention comprises three amino acid sequences and/or Nanobodies®, optionally linked via two linker sequences; etc.; in which at least one of the amino acid sequences and/or Nanobodies® present in the polypeptide, and up to all of the amino acid sequences and/or Nanobodies8 present in the polypeptide, is/are a amino add sequences and/or Nanobodies® of the invention.

In a multivalent polypeptide of the invention, the two or more amino acid sequences or Nanobodies® may be the same or different, and may be directed against the same antigen or antigenic determinant (for example against the same part(s) or epitope(s) or against different parts or epitopes) or may alternatively be directed against different antigens or antigenic determinants; or any suitable combination thereof. For example, a bivalent polypeptide of the invention may comprise (a) two identical amino acid sequences or Nanobodies®; (b) a first amino acid sequence or Nanobody® directed against a first antigenic determinant of a protein or antigen and a second amino acid sequence or Nanobody® directed against the same antigenic determinant of said protein or antigen which is different from the first amino acid sequence or Nanobody®; tc) a first amino acid sequence or Nanobody® directed against a first antigenic determinant of a protein or antigen and a second amino acid sequence or Nanobody® directed against another antigenic determinant of said protein or antigen; or (d> a first amino acid sequence or Nanobody* directed against a first protein or antigen and a second amino acid sequence or Nanobody® directed against a second protein or antigen (i.e. different from said first antigen). Similarly, a trivaSent poiypeptide of the invention may, for example and without being limited thereto, comprise (a) three identical amino acid sequences or Nanobodies®; (b) two identical amino acid sequences or Nanobody* against a first antigenic determinant of an antigen and a third amino acid sequence or Nanobody® directed against a different antigenic determinant of the same antigen; {c) two identical amino acid sequences or Nanobodies® against a first antigenic determinant of an antigen and a third amino acid sequence or Nanobody® directed against a second antigen different from said first antigen; (d) a first amino add sequence or Nanobody®' directed against a first antigenic determinant of a first antigen, a second amino acid sequence or Nanobody* directed against a second antigenic determinant of said first antigen and a third amino acid sequence or Nanobody® directed against a second antigen different from said first antigen; or (e) a first amino acid sequence or Nanobody* directed against a first antigen, a second amino acid sequence or Nanobody® directed against a second antigen different from said first antigen, and a third amino add sequence or Nanobody* directed against a third antigen different from said first and second antigen.

In a preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino add sequences or Nanobodies® of the invention (as described above).

In one aspect, the invention provides a multivalent, preferably a bivalent or trivaient poiypeptide comprising or essentially consisting of at least two {preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® chosen from amino add sequences that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 {position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference, in another aspect, the invention provides a multivalent, preferably a bivalent ortrivaient polypeptide comprising or essentially consisting of at ieast two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies6 chosen from amino add sequences that comprise two or more stretches of amino acid residues in which one stretch is chosen from the following; a) SEQ iD NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEO, ID NO; 102. provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or i amino acid difference; and at ieast one stretch is chosen from: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino add difference; e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference, such that the stretch of amino acid residues that corresponds to one of a), and b) should always be present in the amino acid sequence that forms part of the multivalent polypeptide and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Preferred multivalent (such as bivalent or trsvalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Manobodies^ chosen from amino acid sequences that comprise three or more stretches of amino add residues, in which the first stretch of amino acid residues is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 98, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; the second stretch of amino acid residues is chosen from the group consisting of: c) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and the third stretch of amino acid residues is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference. in yet another aspect, the invention provides a multivalent, preferably a bivaient ortrivalent polypeptide comprising or essentially consisting of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies*' that essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDRl to CDR3, respectively), in which CDR2 is chosen from: aj SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position S4 determined according to Rabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. in yet another aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® that essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDRl to CDR3, respectively), in which CDR2 is chosen from the group consisting of: a) SEQ ID NO: 102; or b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ !D NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and H) the amino acid sequence comprising said stretch of amino acid residues binds protein f of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino add difference; and at least one of CDR1 or CDP3 is chosen from; CDR1 chosen from the group consisting of; c) SEQ fD NO: 98; d) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of nP.SV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared ίο the amino add sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; CDR3 chosen from the group consisting of: e) SEQ ID NO: 121; or f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino add difference.

Preferably, multivalent (such as bivalent or trivalent) polypeptides may comprise or essentiaily consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodles® that essentially consist of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: CDR1 is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F ofhRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and CDR2 is chosen from the group consisting of: c) SEQ ID NO: 102; or d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; fj a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. in a specific aspect, the multivalent (such as bivalent ortrivalent) polypeptides may comprise or essentially consist of at least two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies® that comprise at least SEQ ID NO: 102. in another specific aspect, the muitivalent (such as bivalent or trivaient) polypeptides may comprise or essentially consist of si least two (preferably identical) or at ieast three (preferably identical) amino acid sequences or Nanobodies® that comprise at least SEQ ID NO: 102 and at ieast one stretch of amino acid residues (CDR sequence) chosen from: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 121; f) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface pSasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference.

Preferred muitivalent (such as bivalent or trivaient) polypeptides may comprise or essentially consist of at ieast two (preferably identical) or at least three (preferably identical) amino acid sequences or Nanobodies* that comprise at least SEQ ID NO: 102 and at least two stretches of amino acid residues (CDR sequences) in which one stretch is chosen from the group consisting of the stretches of amino acid residues defined in c) and d) and in which the other stretch is chosen from the group consisting of the stretches of amino acid residues defined in e) and f).

In a specific aspect, the multivalent (such as bivalent or trivaient) polypeptides may comprise or essentially consist of at ieast two (preferably identical) or at least three (preferably identical) amino add sequences or Nanobodies®' that comprise at ieast SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ ID NO: 121; or amino acid sequences or Nanobodies* that comprise at least SEQ. ID NO: 98, SEQ ID NO; 102 and SEQ ID NO: 121. in another preferred aspect, the invention provides a multivalent, preferably a trivalent poiypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies® of the invention {as described above), in another preferred aspect, the invention provides a bivalent poiypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® of the invention {as described above). In another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of three (preferably identical) amino add sequences or Nanobodies® of the invention (as described above).

The invention also provides a multivalent, preferably a bivalent or trivalent poiypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino add sequences or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent poiypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® chosen from the foiiowing: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance} and/or the amino acid sequence has the same, about the same, ora higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two {preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 62,65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 3. amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino add sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a leucine (Leu, L) at position 7S and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein} compared to the amino acid sequence without the 3.. 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a muitivaient, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical} amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the poiypeptide of the invention comprises or essentially consists of at ieast two identical amino acid sequences or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

The invention also provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at ieast two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-153; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 146-153. in another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentiatiy consisting of at least two (preferably identical) amino acid sequences or Nanobodies6 chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108; and in addition Arginine (Arg, PO at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105; ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® chosen from the following; a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in. addition Arginine (Arg, R) at position 83, Giutamic add (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with; - SEQ !D NO: 146, the amino add sequence preferably has Glutamine (Gin, Q) at position 105; - SEO. ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, 0.} at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, O) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Giutamic acid (Gtu, E) at position 85 and Giutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid seauence preferably has Arginine (Arg, R) at position 83; - SEQ. ID NQ: 152, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Giutamic add (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or 3 higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentially consists of at least two identical amino acid sequences or Nanobodies® chosen from SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO; 5, in which one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Afal4Pro, Serl9R, He20Leu, Glu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and Gly54Asp.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaISLeu, Atal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin, Glnl08Leu and Giy54Asp. in another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent poiypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the foliowing: Alal4Pro, Serl9Arg, He2QLeu and GlnlOSLeu.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies* that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Prc, SerlQArg, He20Leu, Ata83Arg, Asp85Glu, Argl05Gin and GlnlOSLeu.

In another preferred aspect, the invention provides a muitivaieni, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which following amino acid residues have been mutated:

VaJ5Leu, Ala 14Pro, Glu44Gly, Gly7SLeu, Aia83Arg, AspS5Glu, Argl05Gln and GlnlOSLeu;

AlaS3Arg, AspSSGiu, ArglOSGin and GlnlOSLeu;

Sly78Leu, A!aS3Arg, Asp85Glu and ArglOSGin;

VaISLeu, Alal4Pro, Giu44Giy, Gly78Leu, Aia83Arg, Asp85Giu, ArglOSGin, GlnlOSLeu arid

Gly54Asp;

AlaSSArg, AspSSGiu, ArglOSGin, GlnlOSLeu and Giy54Asp;

Gly7SLeu, AlaSSArg, Asp85Glu, ArglOSGin and Gly54Asp;

Giy54Asp; A!al4Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

Aial4Pro, Serl9Arg, Ile20leu, Glnl08Leu and AlaS3Arg;

Alal4Pro, Serl9Arg, Ile20leu, Glnl08Leu and AspSSGiu;

Ala 14Pro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGin;

Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Ala83Arg and Asp85Glu;

Alal4Pro, Serl9Arg, He20Leu, Ginl08Leu, Ala83Arg and Argl05Gln;

Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu, Asp85Glu and ArglOSGin; or

Alal4Pro, Serl9Arg, lie20Leu, Glnl08leu, Ala83Arg, Asp85Glu and Argl05Gln. in another preferred aspect, the invention provides a multivalent, preferably a trivalent poiypeptide comprising or essentially consisting of at ieast three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 60-76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 50-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Qj at position 105 (said position determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies2 chosen from one of SEQ ID NO's: 60-75. in another preferred aspect, the invention provides a multivalent, preferably a trivaient polypeptide comprising or essentially consisting of at least three (preferably identical) amino add sequences or Nanobodies5, chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67,68,75 and 76, provided that: I) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, Lj at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent, preferably a trivaient polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a) SEQ ID NO's: 62, 65,67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67,68,75 and 76, provided that: i) the amino acid sequence has a Glutamine {Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R} at position 83 (said positions determined according to Kabat numbering}; and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the poiypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies®' chosen from one of SEQ ID NO's; 62, 65,67, 68,75 and 76.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical} amino acid sequences or Nanobodies® chosen from the following: a) SEQ tD NO's: 65 and 76; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance} and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies* chosen from the following; a) SEQ ID NO's: 65 and 76; b) amino acid sequences that nave no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Lsu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 65 and 76.

The invention also provides a multivalent, preferably a trivaient polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies'5 chosen from the following: a) SEQ ID NO's: 146-153; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii} the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino add sequence has the same, a bout the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least three identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a multivaient, preferably a trivaient polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 145-149 and 251-153, provided that: i) the amino add sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 10S; and in addition Arginine (Arg, R) at position S3, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105; ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the invention provides a multivalent, preferably a trivalent poiypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies®' chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ, ID NG's: 146-149 and 151-153, provided that: i] the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, ft) at position 83, Glutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, G) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEG iD NO; 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO; 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO; 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; - SEO. ID NO: 152, the amino acid sequence preferably has Glutamic acid (G!u, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamic acid (Glu, E) at position 85: (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmor, resonance) and/or the amino acid sequence has the same, about the same, or s higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentially consists of at ieast three identical amino acid sequences or Nanobodies® chosen from SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentiaily consisting of at least three (preferably identical) amino acid sequences or Nanobodies*1 that comprise or essentiaily consist of SEQ ID NO: 5, in which one or mors (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Aial4Pro, Serl9R, lle2QLeu, Giu44Giy, Ala74Ser, Gly78Leu, AlaS3Arg, Asp85Glu, ArgiOSSIn, GlnlOSLeu and Gly54Asc.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent poiypeptide comprising or essentially consisting of at ieast three (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VatSLeu, Alal4Pro, Glu44Giy, Gly7SLeu, AiaS3Arg, Asp85Giu, ArglOSGin, Ginl08Leu and Gly54Asp.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, SerlSArg, ISe20Leu and GinlOSLeu.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino acid sequences or Nanobodres® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: A!al4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSSGiu, ArglOSGin and GinlOSLeu.

In another preferred aspect, the invention provides a multivalent, preferably a trivalent polypeptide comprising or essentially consisting of at least three (preferably identical) amino add sequences or Nanobodies4, that comprise or essentially consist of SEQ ID NO: 5, in which following amino acid residues have been mutated:

Val5Leu, Alal4Pro, Giu44Gly, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin and Glnl08Leu;

Ala83Arg, AspSSGiu, ArglOSGin and GinlOSLeu;

Gly78Leu, A!a83Arg, AspSSGiu and Argl05G!n;

VaISLeu, Alal4Pro, Glu44Gly, Giy78Leu, Aia83Arg, AspSSGiu. ArglOSGin, GinlOSLeu and

Giy54Asp;

Ala83Arg, AspSSGiu, ArglOSGin, GinlOSLeu and Gly54Asp; - Giy78Leu, Aia83Arg, AspSSGiu, ArglOSGin and Gly54Asp;

Giy54Asp;

Aial4Pro. Serl9Arg, lle20Leu and GinlOSLeu;

Atal4Pro, Serl9Arg, lleZOLeu, GinlOSLeu and Aia83Arg;

Aial4Pro, Serl9Arg, tle20Leu, Glnl08Leu and AspSSGiu ;

Atal4Pro, Serl9Arg, Me20Leu, GinlOSLeu and ArglOSGin;

Alal4Pro, Serl9Arg, lie20Leu, GinlOSLeu, AlaSBArg and AspSSGiu; A!al4Pro, Serl9Arg, He20Leu, GinlOSLeu, Ala83Arg and ArglOSGin;

Alal4Pro, Serl9Arg, lie20Leu, GinlOSLeu, AspSSGiu and Argl056ln; or

Alal4Pro, SerlSArg, lie20Leu, G!nl08Leu, Ala83Arg, Asp85Giu and ArglOSGin.

The invention also provides a multivaient, preferably a bivalent or trivalent polypeptide as described above in which the Glutamic acid at position 1 has been changed into an Aspartic acid.

In this respect, the invention provides a multivaient, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody* chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higner potency {as defined herein) compared to the amino acid sequence without the 2, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least one amino acid sequence or Nanobody® chosen from one of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a multivaient, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivaient polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ. tD NO: 62, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivaient, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEO. ID NO: 65, in which the Glutamic acid at position 1 has been changed into Aspartic acid. in another preferred aspect, the invention provides a multivaient, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody^that comprises or essentially consists of SEQ ID NO: 75, in which the Giutamic add at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 147, in which the Giutamic acid at position 1 has been changed into Aspartic acid. in another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody®that comprises or essentially consists of SEQ ID NO: 14S, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivaient or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or ®hat comprises or essentially consists of SEQ ID NO: 153, in which the Glutamic add at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight, nine, ten, eieven or twelve) amino acid residues have been mutated selected from the following: Va!5Leu, Alsl4Pre, Serl9R, lieZOLeu, Giu44Gly, Ala74Ser. Gly78Leu, AiaSBArg, AspSSGiu, Argl05Gln, Glnl08Leu and Gly54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaISLeu, Aial4Pro, G!u44Gly, Giy78Leu, Afa83Arg, Asp85Glu, ArglQSGln, GinlOSLeu and Gly54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivalent or trivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nancbody®that comprises or essentially consists of SEQ ID NO: S, in which one or more (such as two, three or four} amino acid residues have been mutated selected from the following: A!al4Pro, SerlSArg, lle20Leu and GinlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivaient or trivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSSGiu, Argl05Gln and Ginl08Leu, and wherein the Glutamic add at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent, preferably a bivaient or trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GlulAsp, VaSLeu, Aial4Pro, Glu44Gly, Giy78Leu, AiaESArg, AspSSGlu, ArglOSGIn and Gin 103 Leu;

GlulAsp, Ala83Arg, Asp85Glu, ArglOSGIn and GlnlOSLeu;

GlulAsp, Giy78Leu, Ala83Arg, Asp85Glu and ArglOSGIn;

GlulAsp, VaISLeu, Aial4Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGIn, G!nl08Leu and Gly54Asp;

GlulAsp, Aia83Arg, AspSSGlu, ArglOSGIn, GlnlOSLeu and GiyS4Asp;

GlulAsp, Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gin and Gly54Asp;

GlulAsp and Gly54Asp;

GlulAsp, Alal4Pro, Serl9Arg, lie20Leu and GinlOBLeu;

GlulAsp, Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu and AlaSSArg;

GlulAsp, Aial4Pro, Serl9Arg, ile20leu, GinlOSLeu and Asp85Glu;

GlulAsp, A'al4Pro, Serl9Arg, lie20Leu, Ginl08Leu and ArglOSGIn;

GlulAsp, Alal4Pro, Serl9Arg, ile20Leu, Glnl08Leu, Aia83Arg and AspSSGlu:

GlulAsp, Aial4Pro, Serl9Arg, !le20Leu, GlnlOSLeu, AlaBBArg and ArglOSGIn;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AspSSGlu and Argl05Gin; or GlulAsp, Alal4Pro, SerlSArg, lie20Leu, GlnlOSLeu, Ala83Arg, Asp85Giu and ArglOSGIn.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: r) the amino acid sequence has a Glutamine (Gin, Qj at position 10S (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention is a bivalent polypeptide and comprises or essentially consists of two identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

In another preferred aspect, the invention provides a bivaient polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a} SEa ID NO's: 62, 65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or 3 higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67, 68,75 and 76, provided that; t) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or e higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention is a bivalent polypeptide and comprises or essentially consists of two identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3., preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L] at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies*1 chosen from the following: a) SEO. ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hR5V with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is a bivalent polypeptide and comprises or essentially consists of two identical amino acid sequences or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

The invention also provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ to NO's: 146-153; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 146-153, provided that; i) the amino acid sequence has a Proline {Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering}; and ii} the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency fas defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is a bivaient polypeptide and comprises or essentially consists of two identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 146-153. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies* chosen from the following; a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 ant! 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105; ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the invention a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies* chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino add sequences that have no more than B, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ iD NO's: 145-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, RJ at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: -- SEO. ID NO: 145, the amino add sequence preferably has Glutamine (Gin, 0,} at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Giutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Giutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; - SEQ iD NO: 152, the amino acid sequence preferably has Giutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamic acid (Giu, E) at position 85; (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentially consists of two amino acid sequences or Nanobodies® chosen from SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve} amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, $erl9R, ile20Leu, Giu44Gly, Aia74Ser, Gty78Leu, AiaSBArg, AspSSGiu, ArglOSGIn, GinlOSLeu and Gly54Asp.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nancbodiss® that comprise or essentially consist of SEQ. ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: Va!5Leu, Alal4Pro, G!u44Gly, Giy78Leu, Ala83Arg, AspSSGIu, ArglOSGIn, GinlOSLeu and Gly54Asp.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Sarl9Arg, !le20Leu and GinlOSLeu.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, 3erl9Arg, lle20Leu, A!aS3Arg, AspSSGIu, ArglOSGIn and GinlOSLeu. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of two (preferably identical) amino acid sequences or Nanobodies* that comprise or essentially consist of SEQ ID NO: 5, in which following amino acid residues have been mutated:

VaISLeu, Alal4Pro, Glu44Gly, Giy78Leu, Ala83Arg, Asp85Glu, ArglOSGIn and GinlOSLeu;

Ala83Arg, Asp85Glu, ArglOSGIn and GinlOSLeu;

Gly78Leu, Aia83Arg, Asp85Glu and ArglOSGIn;

VaISLeu, Alal4Pro, Glu446ly, Gly78Leu, Ala83Arg, Asp85G!u, Argl05Gin, GinlOSLeu and

Gly54Asp;

Ala83Arg, Asp85Giu, ArglOSGIn, Glnl08Leu and Giy54Asp; G!y78Leu, Ala83Arg, AspSSGIu, ArglOSGIn and GiyS4Asp;

Gly54Asp; - Alal4Pro, Serl9Arg, lle2GLeu and Glnl08Leu;

Alai4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Ala83Arg;

Alal4Pro, Serl9Arg, !le20Leu, GinlOSLeu and Asp85Glu ;

Alal4Pro, Serl9Arg, ile20Lsu, GinlOSLeu and ArglOSGIn; A!al4Pro, Serl9Arg, ile20Leu, GinlOSLeu, AlaBBArg and AspSSGiu;

Alal4Pro, Serl9Arg, lie20Leu, Ginl08Leu, Ala83Arg and Argl05Gln;

Alai4Pro, Seri9Arg, lie20Leu, GlnlOSLeu, Asp85Glu and ArglOSGln; or Aial4Pro, Serl9Arg, lle2QLeu, Glnl08Leu, Ala83Arg, AspSSGIu and ArglOSGln.

The invention also provides a bivalent polypeptide as described above in which the Glutamic, acid at position 1 has been changed into an Aspartic acid.

In this respect, the invention also provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody8' chosen from the foliowing: a) SEQ ID MO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one o? SEQ ID NQ's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kaoat numbering); and ii} the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least one amino acid sequence or Nanobody® chosen from one of SEQ. ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody0 that comprises or essentially consists of SEQ ID NO: 5, in which the Glutamic add at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NQ: 52, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 55, in which the Glutamic acid at position 1 has been changed into Aspartic add.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at ieast one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 75, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 147, in which the Glutamic acid at position 1 has been changed into Aspartic add. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 149, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 153, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, l!e20Leu, Glu44Gly, Ala74Ser, Gly78Leu, AiaS3Arg, Asp85Glu, Argl05Gln, GlnlOSLeu and Gly54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at ieast one amino add sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaISLeu, Aial4Pro, Glu44Gly, Gly78Leu, Aia83Arg, AspS5Glu, Argl05Gln, GlnlOSLeu and Gly54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody* that comprises or essentially consists of SEQ iD NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following:: Alal4Pro, Serl9Arg, lie20Leu and GlnlOSLeu, and wherein the Giutamic acid at position i has been changed into Aspartic add. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody* that comprises or essentially consists of StQ (0 NO: 5, in which one or more {such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, He20Leu, AlaSBArg, Asp85G!u, ArglCSGtn and GlnlOSLeu, and wherein the Glutamic add at position 1 has been changed into Aspartic add. in another preferred aspect, the invention provides a bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GiulAsp, ValSLeu, Alal4Pro, Giu44Gly, Giy78Leu, Aia83Arg. Asp85Glu, ArglOSGin and

GlnlOSLeu;

GiulAsp, AlaSBArg, Asp85Giu, ArglOSGin and GlnlOSLeu;

GlulAsp, Gly78Leu, AlaSBArg, AspSSGIu and ArglOSGin;

GlulAsp, VaISLeu, Alal4Pro, Glu44Gly, Giy78Leu, Ala83Arg, Asp85G!u, Argl05Gln, GlnlOSLeu and G!y54Asp;

GlulAsp, AiaSBArg, Asp85Glu, ArglOSGin, Glnl08leu and Giy54Asp;

GiulAsp, Giy7SLeu, Ata83Arg, Asp85Glu, Argl05Gln and Gly54Asp;

GlulAsp and Giy54Asp;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

GlulAsp, A!al4Pro, SerlSArg, He20Leu, GlnlOSLeu and AiaSBArg;

GlulAsp, Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu and AspSSGIu;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGin;

GlulAsp, Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Ala83Arg and AspS5Glu;

GlulAsp, Aial4Pro, Serl9Arg, Ile20leu, GlnlOSLeu, Ala83Arg and ArglOSGin;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AspSSGIu and Argl05Gln; or

GlulAsp, Alal4Pro, Serl9Arg, l!e20Leu, GlnlOSLeu, AlaS3Arg, AspSSGIu and ArglOSGin.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentialiy consisting of three (preferably identical) amino acid sequences or Nanobodtes® chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency {as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention is a trivalent polypeptide and comprises or essentially consists of three identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO’s: 60-76.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies'8, chosen from the following; a) SEQ, ID NO's: 62, 65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, provided that: 1) the amino acid sequence has a Giutamine (Gin, Q) at position 105, a Leucine (leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ tD NO's: 62, 65, 67, 68,75 and 76, provided that: ί) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position SB (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to t'ne amino acid sequence without the 3,2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention is a trivaient poiypeptide and comprises or essentially consists of three identica! amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

In another preferred aspect, the invention provides a trivaient poiypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies'1' chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3. 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: (} the amino acid sequence has an Aspartic acid {Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in another preferred aspect, the polypeptide of the invention is a trivalent polypeptide and comprises or essentially consists of three identical amino acid sequences or Nanobodies® chosen from one of SEQ ID NO's: 55 and 76.

The invention also provides a trivalent polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position IS, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared το the amino acid sequence without the 3,2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is a trivalent polypeptide and comprises or essentially consists of three identical amino acid sequences or Nanobodies5 chosen from one of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L} at position 20 and/or Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, £) at position 85 and/cr Glutamine (Gin, Q) at position 105; ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nancbodies® chosen from the following: a) SEQ ID WO's: 145-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-14S and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, ft) at position S3, Giutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Giutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; - SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85; - SEQ ID NO: 153, the amino add sequence preferably has Arginine {Arg, R) at position S3 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity' {said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

Preferred polypeptides of the invention comprises or essentially consists of three amino acid sequences or Nsnobodies® chosen from SEQ ID NO's: 146-349 and 151Ί53. in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Aiel4Pro, Serl9R, lle20Leu, Glu44Gly, Aia74Ser, Giy78teu, Ala83Arg, AspSSGiu, ArglOSGIn, GlhlOBLeu and Gly54Asp. in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies* that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Glu44Gly, Gly78L.su, Ata83Arg, AspSSGiu, ArglOSGIn, GlnlOSLeu and Gly54Asp. in another preferred aspect, the invention provides a trivaient polypeptide comprising or essenttaiiy consisting of three (preferably identical) amino acid sequences or Nanobodies®1 that comprise or essentially consist of SEQ ID NO: S, In which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: ASal4Pro, Ser29Arg, lle2GLeu and GlnlOSLeu,

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Ala83Arg, Asp85Glu, Argl05Gin and GlnlOSLeu.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of three (preferably identical) amino acid sequences or Nanobodies-' that comprise or essentially consist of SEQ ID NO: 5, In which following amino acid residues have been mutated:

ValSLeu, Alal4Pro, Glu44Giy, Giy73Leu, Aia83Arg, Asp856iu, ArglOSGin and GlnlOSLeu;

AlaBSArg, Asp85Giu, Argl05Gln and GlnlOBLeu;

Gly78Leu, Ata83Arg, Asp85Glu and ArglOSGin;

ValSLeu, Alal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin, Glnl08Leu and

Gly54Asp;

Ala83Arg, Asp85Glu, ArglOSGin, Glnl08Leu and Gly54Asp;

Gty78Leu, Ala83Arg, Asp85Glu, ArglOSGin and Gly54Asp;

Gry54Asp;

Aial4Pro, Serl9Arg, lle20Leu and GlnlOBLeu; ASsl4Pro, Serl9Arg, lie20Leu, GlnlOBLeu and A!a83Arg;

Aial4Pro, Serl9Arg, lie2GLeu, GlnlOBLeu and AspSSGiu ;

Aial4Pro, Serl9Arg, He20Leu, Glnl08Leu and ArglOSGin;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu, A!a83Arg and AspSSGiu; ASal4Prc, Serl9Arg, Ile20leu, GinlOSLeu, ASa83Arg and ArglOSGin;

Aial4Pro, Serl9Arg, lle20Leu, GinlOSLeu, AspSSGiu and ArglOSGin; or

Afal4Pro, 5erl9Arg, lle20Leu, GinlOSLeu, AlaS3Arg, AspSSGiu and ArglOSGin. A preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO; 52. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies* with SEQ ID NO: 65. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies^ with SEQ ID NO: 75. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO: 75. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies*1 with SEQ ID NO: 147. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies* with SEQ ID NO: 149. Another preferred multivalent polypeptide of the invention comprises or essentially consists of three amino acid sequences or Nanobodies® with SEQ ID NO: 153.

The invention also provides a trivalent polypeptide as described above in which the Glutamic acid at position 1 has been changed into an Aspartic acid.

In this respect, the invention also provides a trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; bj amine add sequences that have no more than 3r preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: t) the amino acid sequence has a Aspartic acid {Asp, D) at position 1 (said position determined according to Kabat numbering); and ii} the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprises or essentially consists of at least one amino acid sequence or Manobody® chosen from one of SEQ !D NO's: 138-141 and 154-157. in another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of at least one amino add sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 62, in which the Glutamic add at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of at ieast one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 65, in which the Glutamic acid at position 1 has been changed into Aspartic add.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of at ieast one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic add.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 75, in which the Glutamic acid at position 1 has been changed into Aspartic acid. in another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 147, in which the Glutamic acid at position 1 has been changed into Aspartic acid. in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentiaiiy consisting of at ieast one amino acid sequence or Nano body® that comprises or essentially consists of SEQ ID NO: 149, in which the Giutamic acid at position i has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentiaiiy consisting of at least one amino acid sequence or Nanobody® that comprises or essentiaiiy consists of SEQ ID NO: 153, in which the Giutamic acid at position 1 has been changed into Aspartic add. in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentiaiiy consisting of at (east one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Atal4Pro, 5erl9R, !le20Leu, Glu446ly, Aia74Ser, Giy78Leu, AtaS3Arg, Asp85Giu, ArglOBGIn,

GtnlOSLeu and Giy54Asp, and wherein the Giutamic acid at position 1 has been changed into Aspartic acid, in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of at (east one amino acid sequence or Nanobody® that comprises or essentiaiiy consists of SEQ ID NO: 5, in which one or more (such as tv/o, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, G!u44GSy, Gly78Leu, AtaS3Arg, Asp85Giu, ArglOoGln, 6inl08Leu and G!yS4Asp, and wherein the Giutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentiaiiy consists of SEQ ID NO: 5, in which one or mere (such as two, three or four) amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, iie20Leu and GlnlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivaient poiypeptide comprising or essentiaiiy consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, A!a83Arg, Asp85Glu, ArglOSGln and GlnlOSLeu, and wherein the Glutamic add at position 1 has been changed into Aspartic acid. tn another preferred aspect, the invention provides a trivaient poiypeotide comprising or essentially consisting of at least one amino acid sequence or Nanobody® that comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GiulAsp, Val5Leu, Aial4Pro, Giu44Gly, Giy78leu, AiaSBArg, Asp85Giu, ArglOSGin and Glnl08Leu;

GiulAsp, AlaSBArg, AspSSGIu, ArglOSGin and GlnlOSLsu;

GiulAsp, Giy78Leu, Aia83Arg, AspSSGIu and ArglOSGin;

GiulAsp, VaISLeu, A!al4Prc, Glu44Gly, Gly78Leu, AiaSBArg, Asp85Glu, ArglOSGin, GinlOSLeu and Giy54Asp;

GiulAsp, AiaS3Arg, AspSSGIu, ArglOSGin, GinlOSLeu and Gly54Asp:

GiulAsp, Giy78Leu, Ala83Arg, Asp85Giu, ArglOSGin and Gly54Asp;

GiulAsp and Gly54Asp;

GiulAsp, Aiai4Pro, SerlOArg, Iie20leu and GinlOSLeu:

GiulAsp, Aial4Pro, Serl9Arg, lle20Leu, GinlOSLeu and AiaS3Arg;

GiulAsp, Alal4Pro, Serl9Arg, He20Leu, GinlOSLeu and Asp85Glu;

GiulAsp, Aial4Pro, Serl9Arg, lie20Leu, GinlOSLeu and ArglOSGin;

GlulAsp, Alal4Pro, Serl9Arg, lie20Leu, Ginl08Leu, AiaSBArg and A$p85Giu;

GiulAsp, Aial4Pro, Serl9Arg, Iie20Leu, 6lnl08Leu, Ala83Arg and ArglOSGin;

GlulAsp, Aia!4Pro, Serl9Arg, ile20Leu, Glnl08Leu, Asp85Giu and ArglOSGin; or GiulAsp, Aial4Pro, Serl9Arg, i!e20Leu, GinlOSLeu, AiaS3Arg, AspSSGiu and ArglOSGin.

In another preferred aspect, the invention provides a trivaient polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 77-79 and 158; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 77-79 and 158, provided that: i) the amino acid sequences or Nanobodies® encompassed in said polypeptide have a Glutamine [Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and/or a Glutamic acid (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the poiypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the invention provides a trivalent polypeptide chosen from the following poiypeptidss: a) SEQ ID NO's: 77-73 and 158; b) poiypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 77-79 and 158, provided that: i) the amino acid sequence or Nanobody* encompassed in said polypeptide has a Glutamine {Gin, Q) at position 105, a Leucine {Leu, L) at position 78, an Arginine (Arg, R) at position 83 and a Glutamic acid (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F ofhRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance} and/or the polypeptide has the same, about the same, or a higher potency {as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise or essentially consist of one of SEQ ID NO's; 77-79 and 158.

In another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO: 78 and 79; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 78 and 75, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid {Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and/or a Glutamic acid {Giu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference. in a preferred aspect, the invention provides a trivalent poiypeptide chosen from the following poiypeptides: a) SEQ ID NO: 78 and 79; or b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 78 and 79, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has an

Aspartic add (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and a Giutamic acid (Giu, E) at position 85 {said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference, A preferred trivalent polypeptide of the invention comprises or essentially consists of SEQ. ID NO: 78. Another preferred trivalent polypeptide of the invention comprises or essentially consists of SEQ ID NO: 79.

In another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 159-161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's; 159-161, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proiine (Pro, P) at position 14, Arginine {Arg, R) at position 19, leucine (Leu, L) at position 20 and/or Leucine {Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Preferred trivaieni polypeptides of the invention comprise or essentially consist of one of SEQ ID NO's: 159-161.

In another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides; a) SEQ ID NO's: 159-161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 159-161, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine {Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108; ana in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the poiypeptide without the 3, 2 or i amino acid difference, in another preferred aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 159*161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than I amino acid difference with one of SEQ ID NO's: 159-161, provided that: i} the amino acid sequence or Nanobody® encompassed in said poiypeptide has a Praline {Pro, P) at position 14, Arginine (Arg, R) at position IS, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position S3, Glutamic acid (G!u, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the polypeptide has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 159, the amino acid sequence or Nanobody® encompassed in said poiypeptide preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 160, the amino acid sequence or Nanobody® encompassed in said poiypeptide preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 161, the amino acid sequence or Nanobody® encompassed in said poiypeptide preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Giu, Ξ) at position 85; (said positions determined according to Rabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the poiypeptide without the 3,2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise or essentialiy consist of one of SEQ ID NO's: 159-161.

In another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentialiy consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) NanobodyVNanobodies® that form(s) part of SEQ !D NO: 53, one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, ile2QLeu, Glu44Gly, Aia74Ser, Gly78leu, AiaSBArg, AspSSGIu, ArglOSGln, GlnlOSLeu and Glv54Asp. in another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in at! three) Nanobody®/Nanobodiesa' that form(s) part of SEQID NO: 53, one or more (such as two, three, four, five, ξϊκ, seven, eight or nine) amino acid residues have been mutated selected from the following: Val5Leu, Alal4Pro, Giu44Gty, Gly78Leu, AiaSBArg, Asp85Giu, ArglQ5Gin, GlnlOSLeu and Gly54Asp.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably In all three) Nanobody®/Nanobodies* that form(s) part of SEQ ID NO: 53, one or more (such as two, three or four) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lie20Leu and GlnlOSLeu. in another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ail three) Nanobody'VNanobGdies® that form(s) part of SEQ ID NO: S3, one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Aia83Arg, AspSSGIu, Argl056ln and GlnlOSLeu.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: S3, in which in at least one (preferably in two, more preferably in ali three) NanobodyV^anobodies® that form(s) part of SEQID NO: 53, following amino acid residues have been mutated:

VaISLeu, Alal4Pro, Glu44Gly, G!y78Leu, AlaS3Arg, Asp85Giu, Argl05Gln and GlnlOSLeu;

AiaSBArg, AspSSGIu, ArglOSGln and GlnlOSLeu;

Gly78Leu, Ala83Arg, Asp85Glu and ArglOSGln;

VaISLeu, Aial4Pro, G!u44Giy, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGln, GlnlOSLeu and

Gly54Asp;

AiaSBArg, Asp85Glu, Argl05Gln, GlnlOSLeu and Gly54Asp;

Gly78Leu, AiaSBArg, AspSSGIu, ArglOSGln and Gly54Asp; 6iy54Asp;

Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu and Ala83Arg;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Asp85Glu ;

Alal4Prc, Serl9Arg, lle20Leu, GlnlOSLeu and Argl05Gln;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu, AiaSBArg and AspSSGIu;

Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AtaSBArg and ArglOSGln;

Alal4Pro, Serl9Arg, lie20Leu, Glnl08Leu, AspSSGiu and Argl05Gln; or Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AiaS3Arg, AspS5Glu and ArglOSGln.

In another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ !D NO: 77. in another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ. ID NO: 78. in another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 79. In another preferred aspect, the poiypeptide of the invention essentially consists of one of SEQ ID NO's: 158-161.

During the production of the polypeptides of the invention, a high level of pyro glutamate (pGlu) on the amino terminus was detected by RP-HPLC. Levels or more than 15% pGiu were detected following fermentation and the levels of pGlu were steadily increasing upon storage during stability studies. Such a modification leads to heterogeneity of the final product and needs to be avoided. The control/prevention of pGlu formation is therefore critical to keep therapeutic proteins within their set specifications. Specific liquid formulations and/or storage conditions are needed for proteins with an N-terminal Glutamic acid thus minimizing the formation of pyro-Gtuiamic acid. in the present invention, the possibility of pGlu post-translational modification of the N-terminus was eliminated by changing the N-terminal Glutamic acid (E) [HOOC-(CH2)2 --protein] into an Aspartic add (D) [HOOC-CH2 -protein] which lead to increased product stability. Accordingly, the present invention also relates to polypeptides as described above wherein the Glutamic acid at position 1 is changed into an Aspartic acid.

The present invention provides a number of sequence optimized polypeptides that show increased stability upon storage during stability studies. Accordingly, the Invention provides a trivalent polypeptide as described above, wherein the first amino acid (Glutamic acid) has been changed into Aspartic acid.

In one aspect, the invention provides a trivalent polypeptide chosen from the following polypeptides: a) SEQ ID NO's: 142-145 and 162-165; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 142-145 and 152-165, provided that: i) the first amino acid sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid (Asp, D) at position 1; and ii) the polypeptide binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein} compared to the polypeptide without the 3,2 or 1 amino acid difference. A preferred trivalent polypeptide of the invention comprises or essentially consists of SEQ ID NO: 142. Another preferred trivalent polypeptide of the invention comprises or essentially consists of SEO ID NO: 143. Another preferred trivalent polypeptide of the invention comprises or essentially consists of SEQ. ID NO: 144 . Another preferred trivalent polypeptide of the invention comprises or essentially consists of SEO ID NO: 145. Another preferred trivalent polypeptide of the invention comprises or essentially consists of one of SEQ ID NO's: 162-165. in another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of SEO. ID NO: S3, in which the Glutamic acid at position 1 has been changed into Aspartic acid (GlulAsp). in another preferred aspect, the invention provides s trivalent polypeptide comprising or essentially consisting of SEQ. ID NO: 77, in which the Glutamic acid at position 1 has been changed into Aspartic acid (GiulAsp).

In another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of SEQ ID NO: 78, in which the Giutamic acid at position 1 has been changed into Aspartic acid (GlulAsp}.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 79, in which the Giutamic acid at position 1 has been changed into Aspartic acid (GlulAsp).

In another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of SEQ ID NO: 158, in which the Giutamic acid at position 1 has been changed into Aspartic add (GlulAsp).

In another preferred aspect, the invention provides a trivaient poiypeptide comprising or essentially consisting of SEQ ID NO: 159, in which the Glutamic acid at position 1 has been changed into Aspartic acid (GlulAsp). in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of SEQ !D NQ: 160, in which the Glutamic acid at position 1 has been changed into Aspartic acid (GlulAsp). in another preferred aspect, the invention provides a trivalent poiypeptide comprising or essentially consisting of SEQ ID NO: 161, in which the Glutamic acid at position 1 has been changed into Aspartic acid (GlulAsp). in another preferred aspect, the invention provides a trivaient polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ail three) Nanobody®/NanobodiesE that form(s) part of SEQ ID NQ: 53, one or more (such as two, three, four, five, six, seven, eight, nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaiSLeu, Alsl4Pro, Serl9R, !ie20Leu, 6lu44Giy, Aia74Ser, Gly78Leu, AiaSBArg, AspSSGiu, Argl05G'm, GinlOSLeu and Giy54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid (GiulAsp). in another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at ieastone (preferably in two, more preferably in all three) Nanobody*/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more {such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaiSLeu, Aial4Pro, Glu446ly, Gly78Leu, AiaSBArg, Asp85Glu, Argl05Gin, GlrtlQ8Leu and Gly54Asp, and wherein the Glutamic acid at position I has beer, changed into Aspartic acid (GlulAspj.

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, SerlSArg, lle20Leu and Gtnl08Leu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid (GiulAsp).

In another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody^/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Aia83Arg, AspS5Glu, ArglOSGin and GinlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic add (GiulAsp). in another preferred aspect, the invention provides a trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ail three) Nanobody®/Nanobodies® thatform(s) part of SEQ ID NO: 53, following amino acid residues have been mutated:

GluiAsp

GiulAsp, VaiSLeu, Atal4Pro, Giu44Gly, Giy78Leu, AiaSBArg, AspSSGiu, ArglOSGIn and

Glnl08Leu;

GiulAsp, Ala83Arg, AspSSGiu, Argl05Gln and GlnlG8Leu;

GiulAsp, Giy78Leu, Ala83Arg, Asp85Gtu and Argl05Gln;

GiulAsp, Va!5Leu, Alal4Pro, Glu446iy, Gly78Leu, Ala83Arg, AspSSGiu, Argl05Gln, GinlOSLeu and Gly54Asp;

GluiAsp, Ala83Arg, Asp85Giu, ArglOBGln, GinlOSLeu and Gly54Asp;

GlulAsp, G!y78Leu, AiaSBArg, AspSSGlu, ArglOSGln and Giy54Asp;

GiulAsp and Gly54Asp;

GlulAsp, Ala 14Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

GlulAsp, A!sl4Pro, Serl9Arg, lie20Leu, GlnlOSLeu and AiaSBArg;

GiulAsp, Alal4Pro, SerlSArg, lie2GLeu, Glnl08Leu and AspSSGlu;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGln;

GlulAsp, Ala 14Pro, 5erl9Arg, lieZOLeu. GlnlOSLeu, Ala83Arg and AspSSGlu;

GiulAsp, Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu, AiaSBArg and ArglOSGln;

GiulAsp, Alal4Pro, Serl9Arg, !ie20Leu, GlnlOSLeu, AspSSGlu and ArglOSGln; or GlulAsp, Alal4Pro, Serl9Arg, ile20Leu, GlnlOSLeu, AiaSBArg, AspSSGlu and ArglOSGln.

In another preferred aspect, the poiypeptide of the invention essentially consists of tne amino acid sequence of SEQ ID NO: 142. In another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 143. In another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 144. tn another preferred aspect, the polypeptide of the invention essentially consists of the amino acid sequence of SEQ ID NO: 145. In another preferred aspect, the poiypeptide of the invention essentially consists of one of SEQ ID NO's: 162-165.

Polypeptides with the amino acid sequences and poiypeptide sequences as described above have shown advantageous properties for use as prophylactic, therapeutic and/or pharmacologically active agents such as e.g. improved stability, less immunogenicity, improved binding characteristics (suitably measured and/or expressed as a KD-vaiue (actual or apparent), a KA-value (actual or apparent), a kor-rate and/or a kofrrate, or alternatively as an ICS0 value, as further described herein), improved affinity and/or improved avidity for protein r of HRSV and/or improved efficacy and/or potency for neutralizing hRSV.

More in particular, these polypeptides and compounds of the invention can bind to protein F of hRSV with an affinity (suitably measured and/or expressed as a Kp-value (actual or apparent), a KA-value (actual or apparent), a k0!,-rate and/or a k0jrrate, or alternatively as an IC50 value, as further described herein) preferably such that they: bind to protein F of hRSV with a dissociation constant (Ko) of 100 nM to 0.1 nM or less, preferably 10 nM to 0.1 nM or less, more preferably 1 nM to 0.1 nM or less; and/or such that they: bind to protein F of hRSV with a kon-rate of between 104 M'*s'* to about 107 M'V‘, preferably between 105 ΜΎ1 and 10' M‘V\ more preferably about ΙΟ" M 's'- or more; and/or such that they: bind to protein F of hRSV with a k0« rate between 10? s'1 it 1/2=0-69 s) and 1C··4 s' (providing a near irreversible compiex with a t1/2 of multipie days}, preferably between 10'3 s ' and 1C4 s ', more preferably between 5xl0'3 s'1 and 10-4 s’", or lower;

Some preferred ICSO values for binding of the polypeptides of the invention to protein F of hRSV will become dear from the further description and examples herein.

Assays to determine the IC50 include competition assays such as competition ELISA (e.g. competition with Synagis6 or its Fab fragment) or more preferably neutralization assays such as the microneutraiization assay described by Anderson et a!.(l985, J. Ciin. Microbiol. 22:1050-1052), modification of this assay as described in example 6, or a piaque reduction assay as described by Johnson et al. (1997, J. Inf. Dis. 176:1215-1224), and modifications thereof.

For example, in a competition assay with. Synagis'1', the polypeptides of the invention may have ICSO values between 1 nM and 100 nM, preferably between 10 nM and 50 nM, or iess.

For example, in a microneutraiization assay of RSV strain Long (such as e.g. described in Example 6) the polypeptides of the invention may have IC50 values between 10 pM and 1000 pM, preferably between 10 pM and 250 pM, more preferably between 50 pM and 200 pM or iess. In a microneutraiization assay, the polypeptides of the invention may have ICSO values that are at least the same and preferably better, at least ten times better, preferably twenty times better, more preferably fifty times better, even more preferably sixty, seventy, eighty or more times better compared to the ICSO value obtained with Synagisw.

The invention also relates to a monovalent polypeptide or construct (also referred to as "monovalent polypeptide of the invention" or "monovalent construct of the invention"), comprising or essentially consisting of one amino acid sequence or Nanobody® of the invention. Preferred monovalent constructs of the invention comprise or essentially consist of one of SEQ ID NO's: 60-76, such as one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, such as e.g. SEQ ID NO's: 65 or 75; one of SEQ ID NO's: 138-141; one of SEQ ID NO's: 146-153; or one of SEQ ID NO's: 154-157. Such a monovalent constructs, as well as the amino acid sequences and Nanobodies® of the invention can be used for the preparation of a polypeptide of the invention, such as e.g. the multivalent polypeptides of the invention described above.

The polypeptides of the invention can generally be prepared by a method which comprises at least the step of suitably linking the amino acid sequence. Nanobody® or monovalent construct of the invention to one or more further amino acid sequences, Nanobodies® or monovalent constructs of the invention, optionally via the one or more suitable linkers, so as to provide the polypeptide of the invention. Polypeptides of the invention can also be prepared by a method which generally comprises at least the steps of providing a nucieic add that encodes a polypeptide of the invention, expressing said nucleic acid in a suitable manner, and recovering the expressed polypeptide of the invention. Such methods can be performed in a manner known per se, which will be dear to the skilled person, for example on the basis of the methods and techniques further described herein. A method for preparing multivalent, multiparatopic and/or multispecific amino acids or polypeptides of the invention may comprise at least the steps of linking two or more monovalent amino acid sequences or monovalent constructs of the invention and for example one or more linkers together in a suitable manner. The monovalent constructs (and linkers) can be coupled by any method known in the art and as further described herein. Preferred techniques include the linking of the nucleic acid sequences that encode the monovalent constructs (and linkers) to prepare a genetic construct that expresses the multivalent, multiparatopic and/or multispecific amino add sequence or polypeptide. Techniques for Sinking amino acid sequences or nucieic acid sequences will be clear to the skilled person, and reference is again made to the standard handbooks, such as Sambrook et ai. and Ausube! et ai., mentioned above, as well as the Examples below.

Accordingly, the present invention also relates to the use of an amino acid sequence, a Nanobody® or a monovalent construct of the invention in preparing a multivalent polypeptide of the invention. The method for the preparation of a multivalent polypeptide will comprise the linking of an amino acid sequence, a Nanobody® or a monovalent construct of the invention to at least one further amino add sequence, Nanobody® or monovalent construct of the invention, optionally via one or more linkers. The amino add sequence, Nanobody® or monovalent construct is then used as a binding domain or binding unit in providing and/or preparing the multivalent polypeptide comprising two (e.g. in a bivalent polypeptide), three (e.g. in a trivaient polypeptide) or more (e.g. in a multivalent polypeptide) binding units, In this respect, the amino acid sequence, Nanobody® and monovalent construct may be used as a binding domain or binding unit in providing and/or preparing a multivalent and preferably bivalent or trivaient polypeptide of the invention comprising two, three or more binding units. Preferably, the binding domains or binding units are linked via a linker such that the multivalent polypeptide preferably exhibits intramolecular binding compared to intermolecuiar binding. Also preferably the multivalent polypeptide can simultaneously bind both or all three binding sites on the F protein of RSV.

Accordingly, the present invention also relates to the use of an amino acid sequence or a Nanobody* of the invention (as described above) in preparing a multivalent polypeptide. The method for the preparation of the multivalent polypeptide will comprise the finking of the amino acid sequence or Nanobody* of the invention to at least one further amino acid sequences or Nanobody® of the invention, optionally via one or more linkers.

In a preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-75, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position X05 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hP.SV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide. Trie method for the preparation of the rnultivaieni polypeptide will comprise the linking of said amine acid sequence to at least one further amino acid sequences, optionally via one or more iinkers.

In a preferred aspect, the amino acid sequence used in preparing a multivalent poiypeptide comprises or essentially consists of one of SEQ ID NO's: 60-75.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or a Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the multivalent poiypeptide will comprise the linking of said amino add sequence to at ieast one further amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; or b; amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than i amino acid difference with one of SEQ ID NO's: 52,55,67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, LI at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 orl amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the multivalent poiypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing a multivalent polypeptide comprises or essentially consists of one of SEQ ID NO: 62,55, 67,68, 75 and 76.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Giutamine (Gin, Q.) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, ft) at position 83 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the multivalent polypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 55 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's:: 55 and 76, provided that: t) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q} at position 105, a Leucine (Leu, L) at position 7S and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the multivalent polypeptide will comprise the iinking of said amino acid sequence to at least one further amino acid sequences, optionally via one or more tinkers. in a preferred aspect, the amino acid sequence used in preparing a multivalent polypeptide comprises or essentially consists of SEQ ID NO: 65. In another preferred aspect, the amino add sequence used in preparing a multivalent polypeptide comprises or essentially consists of SEQ ID NO: 76.

In a preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined accordingto Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in preparing a multivaient poiypeptide. The method for the preparation of the multivalent polypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing a multivalent poiypeptide comprises or essentially consists of one of SEQ ID NO's: 146-153. in another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline {Pro, P) at position 14, Arginine {Arg, R) at position 19, Leucine {Leu, L) at position 20 and/or Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the multivalent polypeptide will comprise the linking of said amino acid sequence to at ieast one further amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino add sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149. the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic add (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ iD NO; 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; - SEQ ID NO: 152, the amino acid sequence Dreferably has Glutamic add (Giu, E) at position 85; - SEQ ID NO; 153, the amino add sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino add difference. in preparing a multivalent polypeptide. The method for the preparation cf the multivalent poiypeptide wili comprise the linking of said amino acid sequence to at least one further amino acid sequences, optionaiiy via one or more linkers. in a preferred aspect, the amino acid sequence used in preparing a multivalent poiypeptide comprises or essentially consists of one of SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ iD NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the foilowing; Va!5Leu, Aial4Pro, SerlSR, !le20Leu, Glu44Giy, Aia74Ser, Gly78Leu, A!a83Arg, Asp85Glu, ArglOSGIn, Ginl08Leu and Gly54Asp, in preparing a multivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: ValSLeu, Aial4Pro, Giu44Gly, Giy78Leu, Ala83Arg, Asp85Giu, ArglOSGIn, Glnl08Leu and Gly54Asp, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Aial4Prc, SerlSArg, iie20Leu and Ginl08Leu, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention reiates to the use of ar. amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: AialAPro, Serl9Arg, ile20Leu, Ala83Arg, AspS5Glu, ArglOSGIn and Glnl08Leu, in preparing a multivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ, ID NO: 5, in which following amino acid residues have been mutated:

ValSLeu, Alal4Pro, Glu44Gly, Giy78Leu, AlaB3Arg, Asp85Glu, Argl05Gin and GinlOSLeu;

AiaS3Arg, Asp85Glu, ArglOSGIn and Glnl08Leu; G!y7SLeu, AlaS3Arg, AspSSGIu and ArglOSGIn;

ValSLeu, ASal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, Asp85Giu, ArglQ5Gln, GinlOSLeu and

Giy54Asp;

AlaSSArg, AspSSGIu, ArglOSGIn, Glnl08Leu and Gly54Asp;

Gly78Leu, AiaS3Arg, AspSSGIu, ArglOSGIn and Giy54Asp;

Gly54Asp;

Alal4Pro, SerlSArg, lie20Leu and GinlOSLeu;

AialAPro, Serl9Arg, fie20Leu, GinlOSLeu and AlaS3Arg;

Alal4Pro, SerlOArg, lle20Leu, GinlOSLeu and AspSSGIu;

Alal4Pro, SerlOArg, S!e20Leu, GinlOSLeu and ArglOSGIn; A!al4Pro, Serl9Arg, ile20Leu, GinlOSLeu, Ala83Arg and Asp85Giu;

Aial4Pro, Serl9Arg, !le20Leu, Ginl08Leu, Ala83Arg and Argl05Gln;

Alal4Pro, Serl9Arg, ile20Leu, GinlOSLeu, AspSSGIu and Argl05Gln; or

AialAPro, Serl9Arg, lle20Leu, Glnl08Leu, AiaS3Arg, Asp85Glu and ArglOSGIn, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the above wherein the amino acid (Glutamic acid) at position I has been changed into Aspartic acid, in preparing a muitivaient polypeptide.

In this respect, the present invention relates to the use of an amino acid sequence chosen from the following: a} SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. id NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide. The method for the preparation of the muitivaient polypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequences, optionally via one or more Sinkers. in a preferred aspect, the amino acid sequence used in preparing a muitivaient polypeptide comprises or essentially consists of SEQ ID NO: 138. In another preferred aspect, the amino acid sequence used in preparing a muitivaient polypeptide comprises or essentially consists of SEQ ID NO: 139. In another preferred aspect, the amino acid sequence used in preparing a multivalent polypeptide comprises or essentially consists of SEQ ID NO: 140. In another preferred aspect, the amino acid sequence used in preparing a multivalent polypeptide comprises or essentially consists of SEQ ID NO: 141. in another preferred aspect, the amino acid sequence used in preparing a multivalent polypeptide comprises or essentially consists of one of SEQ ID NO's; 154-157.

In another preferred aspect, the present invention relates to the use of an amino add sequence that comprises or essentially consists of SEQ ID NO: 5, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a muitivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 62, In which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID WO: 65, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 76, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 75, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino add sequence that comprises or essentially consists of SEQ ID NO: 147, in which Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ !D NO: 149, in which Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ tD NO: 153, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaiSLeu, Aial4Pro, Serl9R, lle20Leu, Glu44Gly, A!a74Ser, Gly78Leu, AlaS3Arg, AspSSGiu, Argl05Gln, GlnlOSLeu and Giy54Asp, and wherein Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: VaiSLeu, Alal4Pro, Glu44Giy, Gly78Leu, A(a83Arg, AspSSGiu, ArglOSGIn, GlnlOSLeu and Gly54Asp, and wherein Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed info Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four, five, six or seven} amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, He20Leu, Ala83Arg, AspSSGiu, ArglOSGIn and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GlulAsp, Val5Leu, Alal4Pro, Glu44Gly, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGIn and

Glnl08Leu;

GlulAsp, Ala83Arg, AspSSGiu, ArglOSGIn and GlnlOSLeu;

GlulAsp, Gly78Leu, Ata83Arg, AspSSGiu and ArglOSGIn;

GlulAsp, Val5Leu, Alal4Pro, Glu44Giy, Giy78leu, Aia83Arg, Asp85Giu, Argl05Gln, GinlOSLeu and Gly54Asp;

GlulAsp, A!a83Arg, AspSSGiu, ArglOSGIn, GlnlOSLeu and Gly54Asp;

GlulAsp, Giy78Leu, Ala83Arg, AspSSGiu, ArglOSGIn and Gly54Asp;

GlulAsp and Gly54Asp;

GlulAsp, Alsl4Rro, Serl9Arg, lte20Leu and GlnlOSLeu;

GlulAsp, Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu and Ala83Arg;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and AspSSGiu;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGIn;

GlulAsp, Alal4Pro, Serl9Arg, HeZOLeu, GlnlOSLeu, Ala83Arg and Asp85Glu;

GlulAsp, Atal4Pro, Serl9Arg, ISe20Leu, Glnl08Leu, Ala83Arg and ArglOSGIn;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AspSSGiu and Argl05Gln; or

GlulAsp, Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu, A!a83Arg, AspSSGiu and ArglOSGIn, in preparing a multivalent polypeptide.

The present invention also relates to the use of two amino acid sequences and/or Nanobodies* of the invention (as described above) in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of the amino acid sequences and/or Nanobodies® of the invention, optionally via a linker.

Accordingly, in a preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference, in preparing a bivaient polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino acid sequences to each other, optionally via a linker.

In a preferred aspect, the two amino add sequences used in preparing the bivalent polypeptide comprise or essentially consist of one of SEQ ID NO’s: 60-76. in another preferred aspect, the present invention relates to the use of two (preferably identical) amino add sequences chosen from the following: a) SEQ ID NO's: 62,65,67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 62,65, 67,68,75 and 76, provided that; i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or a Arginine (Arg, R) at position 83 (said positions determined according to kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivaient polypeptide wiii comprise the linking of said amino acid sequences to each other, optionally via a linker.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ fD NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3. preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine {Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and an Arginine (Arg, R) at position 83 {said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide wiH comprise the Sinking of said amino acid sequences to each other, optionally via a linker.

In a preferred aspect, the two amino acid sequences used in preparing s bivalent polypeptide comprise or essentially consist of one of SEQ ID NO's: 62, 65, 67, 68,75 and 76. in another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no mors than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amine acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino acid sequences to each other, optionally via a linker.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's:: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino add difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino acid sequences to each other, optionally via a linker.

In another preferred aspect, the present invention relates to the use of two (preferably identical) aminD acid sequences chosen from the following; a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: t) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 13, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequence, optionally via one or more linkers. in a preferred aspect, the amino acid sequences used in preparing a bivalent polypeptide comprises or essentially consists of one of SEQ, ID NO's: 146-153.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ iD NO's: 146-149 and 151-153, provided that; i) the amino acid sequence has a Protine (Pro, P) at position 14, Arginine (Arg, R) at position 19, leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 103; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 35 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino add sequence to at feast one further amino acid sequence, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Gtu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ iD NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position S3, Glutamic acid (Gilt, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ. ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; ~ SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Giutamic acid (Glu, Ξ) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or e higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino acid sequence to at ieast one further amino acid sequences, optionally via one or more linkers, in a preferred aspect, the amino acid sequences used in preparing a bivalent polypeptide comprises or essentially consists of one ofSEQiD NO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaBLeu, Ala!4Pro, Serl9R, lle20Leu, Giu44Gly, Ala74Ser, G!y78Leu, A!a83Arg, Asp85Giu, ArglOSGln, GinlOSLeu and Gly54Asp, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: ValBLeu, Aial4Pro, 6lu44Gly, Gly78Leu, Ala83Arg, Asp85G!u, Argl05Gln, GinlOSLeu and Gly54Asp, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: A!al4Pro, Serl9Arg, lle20Leu and GinlOSLeu, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of two {preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven} amino add residues have been mutated selected from the following: AiaMPro, Serl9Arg, He20Leu, Ala83Arg, AspSSGlu, ArglOSGIn and Glnl08Leu, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of two (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which following amino add residues have been mutated:

VaiSLeu, Alal4Pro, Giu44Gly, Gly78Leu, Ala83Arg, AspSSGlu, ArglOSGIn and GinlOSLeu; A!a83Arg, Asp85Glu, ArglOSGIn and Ginl08Leu;

Gly78Leu, AiaS3Arg, AspSSGlu and ArglOSGIn;

Val5Leu, Alal4Pro, Glu44Giy, Gly7SLeu, Ala83Arg, Asp85Giu, ArglOSGIn, Ginl08Leu and

Giy54Asp;

Ala83Arg, AspSSGlu, ArglOSGIn, Glnl08Leu and Gly54Asp;

Gly78Leu, AlaSBArg, AspSSGlu, Argl05Gln and Gly54Asp; or

Glv54Asp;

Alal4Pro, SerlSArg, lie20Leu and GlnlOSLeu;

Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and AlaSBArg;

Alal4Pro, Serl9Arg, Sle20Leu, Ginl08Leu and Asp85Glu;

Alal4Pro, Serl9Arg, lle20Leu, GinlOSLeu and ArglOSGIn;

Alal4Pro, SerlSArg, ile20Leu, GlnlOSLeu, Aia83Arg and Asp85Glu;

Ala 14Pro, Serl9Arg, ilelOLeu, GinlOSLeu, Ala83Arg and ArglOSGIn;

Aial4Pro, SerlSArg, ile20Leu, GlnlOSLeu, AspSSGlu and ArglQ5Gln; or

Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AlaSSArg, AspS5Glu and Argl05Gln, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the above wherein the amino acid (Glutamic acid) at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In this respect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i} the amino acid sequence has a Aspartic acid {Asp, D) at position 1 {said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide. The method for the preparation of the bivalent polypeptide will comprise the linking of said amino add sequence to at least one further amino acid sequences, optionally via one or more linkers,

In a preferred aspect, the amino acid sequence used in preparing a bivaient polypeptide comprises or essentially consists of SEQ. ID NO: 138. in another preferred aspect, the amino acid sequence used in preparing a bivalent polypeptide comprises or essentially consists of SEC* ID NO: 139. In another preferred aspect, the amino acid sequence used in preparing a bivalent polypeptide comprises or essentially consists of SEQ ID NO; 140. In another preferred aspect, the amino acid sequence used in preparing a bivalent polypeptide comprises or essentially consists of SEQ ID NO: 141. In another preferred aspect, the amino acid sequence used in preparing a bivaient polypeptide comprises or essentially consists of SEQ ID NO: 154-157.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ SD NO: 5, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 62, in which Glutamic add at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 65, in which Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent poiypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid seq uence that comprises or essentially consists of SEQ ID NO: 76, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 75, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino add sequence that comprises or essentially consists of SEQ ID NO: 147, in which Glutamic acid at positron 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 149, in which Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino add sequence that comprises or essentially consists of SEQ ID NO: 153, in which Glutamic acid at position 1 has been changed into Aspartic add, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino add residues have been mutated selected from the following: VaISLeu, A!al4Pro, Serl9R, lle20Leu, G!u44Gly, Aia74Ser, Gly7SLeu, Ala83Arg, Asp85Giu, ArglOSGin, G!nl08Leu and Gly54Asp, and wherein Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that com arises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: Val5Leu, Aial4Prc, Giu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gin, GlnlOSLeu and Giy54Asp, and wherein Glutamic add at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, Ue20Leu and GinlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lie20Leu, Ala83Arg, Asp85Giu, ArglOSGin and GinlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

GlulAsp;

GiulAsp, Va!5Leu, Alai4Pro, Giu44Giy, Gly78Leu, AlaS3Arg, Asp85Glu, ArglQ5Gin and GinlOSLeu;

GlulAsp, Ala83Arg, AspSSGIu, ArglOSGln and GinlOSLeu;

GlulAsp, Gly78Leu, Ala83Arg, AspSSGIu and ArglOSGln;

GlulAsp, ValSLeu, AlalAPro, Giu44Gty, Gly78Leu, Aia83Arg, AspSSGIu, ArglOSGln, GinlOSLeu and Giy54Asp;

GlulAsp, Ala83Arg, Asp85Glu, ArglOSGln, Glnl08Leu and GlySAAsp;

GlulAsp, Giy78Leu, Ala83Arg, Asp85Glu, Argl056in and Giy54Asp;

GlulAsp and Gly54Asp;

GlulAsp, Alsl4Pro, SerlSArg, lle2GLeu and GinlOSLeu;

GlulAsp, Aisl4Prc, Serl9Arg, lie20Leu, GinlOSLeu and Aia83Arg;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GinlOSLeu and Asp85Glu;

GlulAsp, Alal4Prc, Serl9Arg, lle20Leu, GinlOSLeu and ArglOSGln;

GlulAsp, Alal4Pro, Serl9Arg, He20Leu, Glnl08leu, Aia83Arg and AspSSGIu;

GlulAsp, A!al4Pro, Serl9Arg, lle20Leu, GinlOSLeu, A!a83Arg and ArglOSGln;

GlulAsp, AlalAPro, Serl9Arg, lle2DLeu, GinlOSLeu, Asp85Glu and ArglOSGln; or GlulAsp, Alal4Pro, Serl9Arg, lte20Leu, GinlOSLeu, Ala83Arg, AspSSGIu and ArglOSGin, in preparing a bivalent polypeptide.

The present invention also relates to the use of three amino add sequences and/or Nanobodies'* of the invention (as described above) in preparing a trivalent polypeptide. The method for the preparation of the divalent polypeptide will comprise the linking of the amino add sequences and/or Nanobodies® of the invention, optionally via one or two iinkers.

In a preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 60-76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hR5V with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a trivatent poiypeptide, The method for the preparation of the trivaient polypeptide will comprise the linking of said amino acid sequences to each other, optionally via one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparing the trivaient poiypeptide comprise or essentially consist of one of SEQ ID NO's: 60-76.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 62,65,67, SS, 75 and 75; b) amino acid sequences that have no more than 3, preferably no more than 2, mors preferably no more than 1 amino acid difference with one of SEQ. !D NO's: 62, 65, 67, 68,73 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and/or a Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein f of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivaient polypeptide. The method for the preparation of the trivaient polypeptide will comprise the linking of said amino acid sequences to each other, optionally via one or two linkers.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a} SEQ ID NO's: 62, 65, 67,6S, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 62,65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a trivalent polypeptide. The method for the preparation of the trivalent polypeptide will comprise the linking of said amino acid sequence to each other, optionally vis one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparing a trivalent polypeptide comprise or essentially consist of one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO’s: 65 and 76; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 3. amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: t) the ammo add sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q} at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivalent polypeptide. The method for the preparation of the trivalent polypeptide will comprise the Sinking of said amino acid sequences to each other, optionally via one or two linkers.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's:: 65 and 76, provided that: i) the amino acid sequence has an Aspartic add (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg. R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasrnon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a trivalent polypeptide. The method for the preparation of the trivalent polypeptide will comprise the linking of said amino acid sequences to each other, optionally via one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparing the trivalent polypeptide comprise or essentially consist of SEQ ID NO: 65. In another preferred aspect, the three amino acid sequences used in preparing the trivalent polypeptide comprise or essentially consist of SEQ ID NO: 76. in another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proiine (Pro, P} at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (leu, L) at position 103 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference. in preparing a trivalent polypeptide. Hie method for the preparation of the trivalent polypeptide will comprise the linking of said amino acid sequence to at least one further amino add sequence, optionally via one or two linkers. in a preferred aspect, the amino add sequences used in preparing a trivaieni polypeptide comprise or essentially consist of one of SEQ ID NO's: 146-153. in another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino add sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or

Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein f of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivaient polypeptide. The method for the preparation of the trivalent polypeptide wifi comprise the linking of said amino acid sequence to at least one further amino acid sequence, optionally via one or two linkers. in another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences chosen from the following: a) SEQ ID NO's; 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and/or Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino add sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic add (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R} at position 83; - SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino add sequence preferably has Arginine (Arg, R) at position 83 and Glutamic add (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference. in preparing a trivaient polypeptide. The method for the preparation of the trivalent polypeptide will comprise the linking of said amino acid sequence to at least one further amino acid sequence, optionally via one or two linkers.

In a preferred aspect, the amino acid sequences used in preparing a trivaient polypeptide comprises or essentially consists of one of SEQ. ID NO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences that comprises or essentially consists of SEQ !D NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: ValSLeu, ASal4Pro, Serl9Arg, lie20Leu, Glu44G!y, Aia74Ser, G!y78Leu, AiaS3Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Gly54Asp, in preparing a trivaient polypeptide. in another preferred aspect, the present invention relates to the use of three (preferably identical) amino add sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine) amino acid residues have been mutated selected from the following: Val5Leu, Aial4Pro, Glu44Gly, Gly78Leu, AlaSBArg, Asp85Glu, ArglOSGIn, GlnlOSLeu and Gly54Asp, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: A!al4Pro, Serl9Arg, !le20Leu and GlnlOSLeu, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSSGIu, ArglOSGIn and Ginl08Leu, in preparing a trivaient polypeptide. in another preferred aspect, the present invention relates to the use of three (preferably identical) amino acid sequences thar comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

Val5Leu, Alal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGln and GlnlOSLeu;

Aia83Arg, AspSSGiu, ArglOSGln and GlnlOSLeu;

Giy78Leu, Ala83Arg, Asp856Su and Argl05Gln;

VaiSLeu, Alal4Pro, 61u44Gly, Giy78Leu, Ala83Arg, AspSSGiu, ArglOSGln, Glnl08Leu and G!y54Asp;

Ala83Arg, AspSSGiu, ArglOSGln, GlnlOSLeu and Gly54Asp;

Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGln and GiyS4Asp;

Giy54Asp;

Alal4Pro, Serl9Arg, lleZOLeu and GlnlOSLeu;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu and Ala83Arg; A!al4Pro, Serl9Arg, HeZOLeu, GlnlOSLeu and AspSSGiu;

Aial4Pro, Serl9Arg, lle20Leu, Glnl08Leu and ArglOSGln; A!al4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Als83Arg and AspSSGiu;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AiaS3Arg and ArglOSGln;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AspSSGiu and Argl05Gln;

Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Aia83Arg, Asp85Glu and ArglOSGln, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 62 in preparing SEQ ID NO: 77. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 62 to at least two further amino acid sequences with SEQ ID NO: 62, via a 15GS (SEQ ID NO: 128) iinker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 65 in preparing SEQ ID NO: 7S. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 65 to at least two further amino acid sequences with SEQ ID NO: 65, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 76 in preparing SEQ ID NO: 79. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 76 to at least two further amino acid sequences with SEQ ID NO: 76, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 75 in preparing SEQ ID NO: 158. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino add sequence with SEQ ID NO: 75 to at least two further amino acid sequences with SEQ ID NO: 75, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 147 in preparing SEQ ID NO: 159. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 147 to at least two further amino acid sequences with SEQ ID NO: 147, via a 15G5 (SEQ ID NO: 128} tinker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 149 in preparing SEQ ID NO: 160. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 149 to at least two further amino acid sequences with SEQ ID NO: 149, via a 15GS (SEQ ID NO: 128) linker. in another preferred aspect, the present invention relates to the use of SEQ !D NO: 155 in preparing SEQ ID NO: 161. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 153 to at least two further amino acid sequences with SEQ ID NO: 153, via a 15GS (SEQ ID NO: 123} linker.

In another preferred aspect, the present invention relates to the use of an amino acid sequence chosen from the above wherein the amino acid (Glutamic acid) at position 1 has been changed into Aspartic acid, in preparing a trivalent polypeptide. in this respect, the present invention relates to the use of an amino acid sequence chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a trivalent polypeptide. The method for the preparation of the trivalent polypeptide will comprise the linking of said amino acid sequence to at least two further amino acid sequences, optionally via one or more linkers. in a preferred aspect, the amino acid sequence used in preparing a trivalent poiypepttde comprises or essentially consists of SEQ ID NO: 138. In another preferred aspect, the amino acid sequence used in preparing a trivaient polypeptide comprises or essentially consists of SEQ ID NO: 139. In another preferred aspect, the amino acid sequence used in preparing a trivaient polypeptide comprises or essentially consists of SEQ ID NO: 140. In another preferred aspect, the amino acid sequence used in preparing a trivaient polypeptide comprises or essentially consists of SEQ. ID NO: 141. in another preferred aspect, the amino acid sequence used in preparing a trivaient polypeptide comprises or essentially consists of one of SEQ ID NQ's: 154-157. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide, in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 62, in which Glutamic add at position 1 has been changed into Aspartic add, in preparing a trivaient polypeptide,

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEO, ID NO: 65, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 76, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 75, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 147, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 149, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 153, in which Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lle20Leu, Giu44Gly, Ala74Ser,

Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin, Ginl08Leu and Gly54Asp, and wherein Giutamicacid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four, five, six, seven, eight or nine} amino acid residues have been mutated selected from the following: Val5leu, Aial4Pro, Glu44Gly, Giy78Leu, Aia83Arg, Asp856lu, ArglOSGin, GlnlOSLeu and Gly54Asp, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: AialAPro, Serl9Arg, ileZOLeu and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide.

In another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: S, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Prc, Serl9Arg, lie20Leu, Ala83Arg, Asp85Glu, Argl05Gln and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a trivaient polypeptide. in another preferred aspect, the present invention relates to the use of an amino acid sequence that comprises or essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GlulAsp, VaISLeu, Aial4Pro, Glu44Gly, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGin and

Glnl08Leu;

GlulAsp, Ala83Arg, Asp85Glu, Argl05Gln and GlnlOSLeu;

GlulAsp, Giy78Leu, Aia83Arg, AspSSGIu and ArglOSGin;

GlulAsp, VaISLeu, Aial4Pro, Glu44Giy, Gly78leu, AlaSSArg, AspSSGIu, ArglOSGin, GlnlOSLeu and Gly54Asp;

GlulAsp, Ala83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and Gly54Asp;

GlulAsp, Gly78Leu, AlaS3Arg, Asp85Giu, ArglOSGin and GlyS4Asp;

GlulAsp and Gly54Asp;

GlulAsp, Alal4Pro, Serl9Arg, lle2QLeu and GlnlOSLeu;

GlulAsp, Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu and AiaSSArg;

GiulAsp, Alai4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and Asp85Giu;

GlulAsp, Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu and Argl05Gln;

GiulAsp, Alal4Pro, Serl9Arg, Ile20Lsu, GinlOSLeu, Aia83Arg and AspS5Giu;

GluiAsp, Alal4Pro, Serl9Arg, IIe20Leu, GinlOSLeu, AiaS3Arg and Argl05Gln;

GiulAsp, Aial4Pro, Serl9Arg, He20Leu, GinlOSLeu, AspS5Glu and Argl05Gln; or GluiAsp, Alal4Pro, SerlSArg, lle20Leu, Glnl08Leu, Ala83Arg, Asp85Glu and ArglOSGln, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use of SEQ ID NQ: 13S in preparing SEQ ID NO: 142. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 138 to at least two further amino acid sequences (preferably SEQ ID NO: 5), via a 15GS (SEQ ID NQ: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 139 in preparing SEQ ID NO: 143. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 139 to at least two further amino add sequences (preferably SEQ ID NO: 62), via a 15GS (SEQ ID NQ: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 140 in preparing SEQ ID NO: 144. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 140 to at least two further amino acid sequences (preferably SEQ ID NO: 65), via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NQ: 154 in preparing SEQ ID NO: 162. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NQ: 154 to at least two further amino add sequences (preferably SEQ ID NO: 75), via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use of SEQ ID NQ; 155 in preparing SEQ ID NO: 163. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 155 to at least two further amino acid sequences (preferably SEQ ID NO: 147), vis a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention reiates to the use of SEO. ID NO: 156 in preparing SEQ ID NO: 164. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 156 to at least two further amino acid sequences (preferably SEQ ID NO: 149), via a 15GS (SEQ ID NO: 128) Sinker.

In another preferred aspect, the present invention relates to the use of SEQ ID NO: 157 in preparing SEQ. ID NO: 165. The method for the preparation of the multivalent polypeptide will comprise the linking of an amino acid sequence with SEQ ID NO: 157 to at ieast two further amino acid sequences (preferably SEQ ID NO: 153), via a 15GS (SEQ ID NO: 128) linker.

Polypeptides of the invention that contain at least two amino acid sequences and/or Nanobodies®', in which at least one amino acid sequence or Nanobody® is directed against a first antigen (i.e. against protein F of hRSV) and at least one amino acid sequence or Nanobociy® is directed against a second antigen (i.e. different from protein F of hRSV), wit! also be referred to as "multispecific" polypeptides of the invention, and the amino acid sequences or Nanobodies® present in such polypeptides will also be referred to herein as being in a "multispecific format". Thus, for example, a "bispecific" polypeptide of the invention is a polypeptide that comprises at least one amino acid sequence or Nanobody® of the invention directed against a first antigen (i.e. protein F of hRSV) and at least one further amino acid sequence or Nanobody* directed against a second antigen (i.e. different from protein F of hRSV), whereas a "trispedfic" polypeptide of the invention is e polypeptide that comprises at least one amino acid sequence or Nanobody* of the invention directed against a first antigen (i.e. protein F of hRSV), at least one further amino acid sequence or Nanobody* directed against a second antigen (i.e. different from protein F of hRSV} and at least one further amino acid sequence or Nanobody® directed against a third antigen (i.e. different from both protein F of hRSV and the second antigen); etc,

Accordingly, in its simplest form, a bispecific polypeptide of the invention is a bivaient polypeptide of the invention (as defined herein), comprising a first amino acid sequence or Nanobody® of the invention directed against protein F of hRSV, and a second amino acid sequence or Nanobody® directed against a second antigen, in which said first and second amino acid sequence or Nanobody® may optionally be linked via a linker sequence (as defined herein); whereas a trispecific polypeptide of the invention in its simplest form is a trivalent polypeptide of the invention (as defined herein), comprising a first amino acid sequence or Nanobody^ of the invention directed against protein F of hRSV, a second amino acid sequence or Nanobody® directed against a second antigen and a third amino acid sequence or Nanobody® directed against a third antigen, in which said first, second and third amino acid sequence or Nanobody8 may optionally be linked via one or more, and in particular two, linker sequences. m a specific aspect, the polypeptide of the invention is a trivalent, bispecific polypeptide. A trivalent, bispecific polypeptide of the invention in its simplest form may be a trivalent polypeptide of the invention (as defined herein), comprising two identical amino acid sequences or Nanobodies® against protein F of hRSV and a third amino acid sequence or Nanobody® directed against another antigen, in which said first, second and third amino acid sequence or Nanobody® may optionally be linked via one or more, and in particular two, linker sequences. A preferred, but non-iimitine example of a multispecific polypeptide of the invention comprises at least one amino acid sequence or Nanobody1' of the invention and at least one Nanobody® that provides for an increased half-life. Some preferred, but non-limiting examples of such Nanobodies® include Nanobodies® directed against serum proteins, such as human serum albumin, thyroxine-binding protein, (human} transferrin, fibrinogen, an immunoglobulin such as IgG, tgE or IgM, or one of the other serum proteins listed in WO 04/003019.

For example, for experiments in mice, Nanobodies® against mouse serum albumin (MSA) can be used, whereas for pharmaceutical use, Nanobodies® against human serum albumin can be used.

Another embodiment of the present invention is a polypeptide construct as described above wherein said at least one (human) serum protein is any of (human) serum albumin, (human) serum immunoglobulins, (human) thyroxine-binding protein, (human) transferrin, (human) fibrinogen, etc.

Accordingly, in a specific aspect, the polypeptide of the invention is a bispecific polypeptide comprising a first amino acid sequence or Nanobody® of the invention against protein F of hRSV and a second amino add sequence or Nanobody® directed against (human) serum albumin, in which said first and second amino add sequence or Nanobodv® may optionally be linked via a linker sequence.

In another specific aspect, the polypeptide of the invention is a trivalent, bispecific polypeptide, comprising two identical amino add sequences or Nanobodies® of the invention against protein F of hRSV and a third amino add sequence or Nanobody® directed against (human) serum albumin, in which said first, second and third amino add sequence or Nanobodv® may optionally be linked via one or more, and in particular two, linker sequences. in another specific aspect, the polypeptide of the invention is a tetravaient, bispecific polypeptide, comprising three identical amino acid sequences or Nanobodies® of the invention against protein F of hRSV and a fourth amino acid sequence or Nanobody® directed against (human) serum albumin, in which said first, second, third and fourth amino acid sequence or Nanobody® may optionally be linked via one or more, and in particular two or three, linker sequences.

According to a specific, but non-limiting aspect of the invention, the polypeptides of the invention contain, besides the one or more amino acid sequences or Nanobodies® of the invention, at least one Nanobody® against human serum albumin. These Nanobodies® against human serum albumin may be as generally described in the applications by Abtynx N.V. cited above (see for example WO 04/062551), Some particularly preferred Nanobodies® that provide for increased half-life and that can be used in the polypeptides of the invention include the Nanobodies® ALB-1 to ALB-10 disclosed in WO G6/1227S7 (see Tables II and III) of which ALB-8 (SEQ ID NO: 62 in WO 06/122787) is particularly preferred.

In another aspect, the invention relates to a compound or construct, and in particular a protein or polypeptide (also referred to herein as a "compound of the invention") that comprises or essentially consists of one or more amino acid sequences, Nanobodies® and/or polypeptides of the invention (or suitable fragments thereof), and optionally further comprises one or more other groups, residues, moieties or binding units, As will become clear to the skilled person from the further disclosure herein, such further groups, residues, moieties, binding units or amino acid sequences may or may not provide further functionality to the amino acid sequence, Nanobody8 or polypeptide of the invention (and/or to the compound, construct or polypeptide in which it is present) and may or may not modify the properties of the amino acid sequence, Nanobody® and/or polypeptide of the invention.

Such groups, residues, moieties or binding units may for example be chemical groups, residues, moieties, which may or may not by themselves be biologically and/or pharmacologically active. For example, and without limitation, such groups may be linked to the one or more amino add sequences, Nanobodies® and/or polypeptides of the invention so as to provide a ''derivative'" of an amino acid sequence. Nanobody® and/or polypeptide of the invention, as further described herein. ASso within the scope of the present invention are compounds or constructs that comprise or essentially consist of one or more derivates as described herein, and optionally further comprise one or more other groups, residues, moieties or binding units, optionally linked vis one or more linkers. Preferably, said one or more other groups, residues, moieties or binding units are amino acid sequences.

In the compounds, constructs or polypeptides described above, the one or more amino acid sequences, Nanobodies* and/or polypeptides of the invention and the one or more groups, residues, moieties or binding units may be linked directly to each other and/or via one or more suitable linkers or spacers. For example, when the one or more groups, residues, moieties or binding units are amino acid sequences, the linkers may also be amino acid sequences, so that the resulting compound, construct or polypeptide is a fusion (protein) or fusion (polypeptide). A compound or construct of the invention may comprises an amino acid sequence. Nanobody® or polypeptide of the invention, which is fused at its amino terminal end, at its carboxy terminal end, or both at its amino terminal end and at its carboxy terminal end to at least one further amino acid sequence, i.e. so as to provide a fusion protein comprising said amino acid sequence, Nanobody® or polypeptide of the invention and the one or more further amino acid sequences.

The one or more further amino acid sequence may be any suitable and/or desired amino acid sequences. The further amino acid sequences may or may not change, alter or otherwise influence the (biological) properties of the amino add sequence, Nanobody® or polypeptide of the invention, and may or may not add further functionality to the amino acid sequence, Nanobody* or the polypeptide of the invention. Preferably, the further amino acid sequence is such that it confers one or more desired properties or functionalities to the amino acid sequence, Nanobody® or the polypeptide of the invention.

Example of such amino add sequences will be dear to the skilled person, and may generally comprise all amino acid sequences that are used in peptide fusions based on conventionai antibodies and fragments thereof (including but not limited to ScFv's and single domain antibodies). Reference is for example made to the review by Holtigerand Hudson, Nature Biotechnology, 23, 9,1126-1136 (2005).

For example, such an amino acid sequence may be an amino acid sequence that increases the half-life, the solubility, or the absorption, reduces the immunogenicity or the toxicity, eliminates or attenuates undesirable side effects, and/or confers other advantageous properties to and/or reduces the undesired properties of the compounds of the invention, compared to the amino acid sequence. Nanobody® or poiypeptide of the invention per se. Some non-limiting examples of such amino acid sequences are serum proteins, such as human serum albumin (see for example WO 00/27435) or haptenic molecules (for example haptens that are recognized by circulating antibodies, see for example WO 98/22141).

The further amino acid sequence may also provide a second binding site, which binding site may be directed against any desired protein, poiypeptide, antigen, antigenic determinant or epitope (including but not limited to the same protein, polypeptide, antigen, antigenic determinant or epitope against which the amino acid sequence or Nanobody® of the invention is directed, or a different protein, polypeptide, antigen, antigenic determinant or epitope). For example, the further amino acid sequence may provide a second binding site that is directed against a serum protein {such as, for example, human serum albumin or another serum protein such as IgG), so as to provide increased half-life in serum. Such amino acid sequences for example include Nanobodies®, as well as the small peptides and binding proteins described in WO 91/01743, WO 01/45746 and WO 02/076485 and the dAb's described in WO 03/002609 and WO 04/003019. Reference is aiso made to Harmsen et a!., Vaccine. 23 (41); 4926-42, 2005, as well as to EP 0 368 684, as well as to WO 08/028977, WO 08/043821, WO 08/043822 by Ablynx N.V. and WO 08/068280.

Such amino acid sequences may in particular be directed against serum albumin (and more in particular human serum albumin) and/or against IgG (and more in particular human IgG). For example, such amino acid sequences may be amino acid sequences that are directed against (human) serum albumin and amino acid sequences that can bind to amino acid residues on (human) serum albumin that are not involved in binding of serum albumin to FcRn (see for example WO 05/0122787) and/or amino acid sequences that are capable of binding to amino acid residues on serum albumin that do not form part of domain 111 of serum albumin (see again for example WO 06/0122787); amino acid sequences that have or can provide an increased half-life (see for example WO 08/028977); amino acid sequences against human serum albumin that are cross-reactive with serum albumin from at least one species of mammal, and in particular with at least one species of primate {such as, without limitation, monkeys from the genus Macaco {such as, and in particular, cynomoigus monkeys {Macaco fascicularis) and/or rhesus monkeys {Macaco mulatto)) and baboon {Papio ursinus), reference is again made to WO 08/028977); amino acid sequences that can bind to serum albumin in a pH independent manner (see for example WO 08/043821) and/or amine acid sequences that are conditional binders (see for example WO 08/043822).

According to another embodiment, the one or more further amino acid sequences may comprise one or more parts, fragments or domains of conventional 4-chain antibodies (and in particular human antibodies) and/or of heavy chain antibodies. For example, although usually less preferred, an amino acid sequence. Nanobody® or polypeptide of the invention may be linked to a conventional (preferably human) Vt; or VL domain or to a natural or synthetic analog of a VH or VL domain, again optionally via a linker sequence (including but not limited to other (single) domain antibodies, such as the dAb's described by Ward et al.).

Accordingly, in the compound or construct of the invention, said one or more other groups, residues, moieties or binding units may be chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino acid sequences that are suitable for use as a dAb, or Nanobodies®.

In one specific aspect of the invention, the compound, construct or polypeptide of the invention comprising at least one amino acid sequence, Nanobody® or polypeptide of the invention may have an increased half-life, compared to the corresponding amine acid sequence, Nanobody® or polypeptide of the invention. Some preferred, but non-limiting examples of such compounds, constructs and polypeptides will become dear to the skilled person based on the further disclosure herein, and for example comprise amino add sequences. Nanobodies® or polypeptides of the invention that have been chemically modified to increase the half-life thereof (for example, by means of pegylatson); or compounds of the invention that comprise at least one amino acid sequence, Nanobody® or polypeptide of the invention that is linked to at least one moiety (and in particular at least one amino acid sequence) that increases the half-life of the amino acid sequence, Nanobody® or polypeptide of the invention. Examples of compounds of the invention that comprise such half-life extending moieties will become clear to the skilled person based on the further disclosure herein; and for example include, without limitation, compounds in which the one or more amino acid sequences. Nanobodies® or polypeptides of the invention are suitable linked to one or more serum proteins or fragments thereof (such as serum albumin or suitable fragments thereof) or to one or more binding units that can bind to serum proteins (such as, for example, Nanobodies® or (single) domain antibodies that can bind to serum proteins such as serum albumin, serum immunoglobulins such as IgG, or transferrine); compounds in which an amino acid sequence, Nanobody* or poiypeptide of the invention is linked to an Fc portion (such as a human Fc) or a suitable part or fragment thereof; or compounds in which the one or more amino acid sequences, Nanobodies® or polypeptides of the Invention are suitable linked to one or more small proteins or peptides that can bind to serum proteins (such as, without limitation, the proteins and peptides described in WO 91/01743, WO 01/45746, WO 02/076489).

The at least one amino acid sequence, Nanobody® or polypeptide may aiso be linked to one or more (preferably human) Q<1, 0,2 and/or 03 domains, optionally via a linker sequence. For instance, an amino acid sequence, Nanobody® or polypeptide linked to a suitable CHl domain could for example be used - together with suitable light chains - to generate antibody fragments/structures analogous to conventional Fab fragments or F(ab')j fragments, but in which one or (in case of an r(abJ)2 fragment) one or both of the conventional νμ domains have been replaced by an amino add sequence, Nanobody® or polypeptide of the invention. Aiso, two amirso acid sequences or Nanobodies® could be linked to a CK3 domain (optionally via a linker) to provide a construct with increased half-life in vivo.

According to one specific aspect, one or more amino acid sequences, Nanobodies® or polypeptides of the invention may be linked (optionally via a suitable linker or hinge region) to one or more constant domains (for example, 2 or 3 constant domains that can be used as part of/to form an Fc portion), to an Fc portion and/or to one or more antibody parts, fragments or domains that confer one or more effector functions to the amino add sequence. Nanobody® or polypeptide of the invention and/or may confer the ability to bind to one or more Fc receptors. For example, for this purpose, and without being limited thereto, the one or more further amino acid sequences may comprise one or more Ch2 and/or CH3 domains of an antibody, such as from a heavy chain antibody (as described herein) and more preferably from a conventional human 4-chain antibody; and/or may form (part of) and Fc region, for example from !g6 (e.g. from igGl, ig62, lgG3 or lgG4), from igE or from another human Ig such as IgA, igD or IgM. For example, WO 94/04678 describes heavy chain antibodies comprising a Cametid domain or a humanized derivative thereof (i.e. a Nanobody®}, in which the Camelidae CH2 and/or CH3 domain have been replaced by human 0*2 and Ctt3 domains, so as to provide an immunoglobuiin that consists of 2 heavy chains each comprising a Nanobody® and human CK2 and CH3 domains (but no CH1 domain), which immunoglobulin has the effector function provided by the C(t2 and C„3 domains and which immunoglobulin can function without the presence of any light chains. Other amino acid sequences that can be suitably linked to the amino acid sequences, Nanobodies® or polypeptides of the invention so as to provide an effector function will be clear to the skilled person, and may be chosen on the basis of the desired effector function(s). Reference is for example made to WO 04/058820, WO 99/42077, WO 02/056910 and WO 05/017148, as well as the review by Holiiger and Hudson, supra; and to WO 09/068628. Coupling of an amino acid sequence, Nanobody® or polypeptide of the invention to an Fc portion may also lead to an increased half-life, compared to the corresponding amino acid sequence, Nanobody®' or polypeptide of the invention. For some applications, the use of an Fc portion and/or of constant domains (i.e. CH2 and/or Ch3 domains) that confer increased half-life without any biologically significant effector function may also be suitable or even preferred. Other suitable constructs comprising one or more amino acid sequences, Nanobodies*' or polypeptides and one or more constant domains with increased haif-iife in vivo will be dear to the skilled person, and may for example comprise amino acid sequences, Nanobodies®' or polypeptides linked to a CK3 domain, optionally via a linker sequence. Generally, any fusion protein or derivatives with increased half-life will preferably have a molecular weight of more than 50 kD, the cut-off value for renal absorption.

In another specific, but non-iimiting, aspect, in order to form a compound of the invention, one or more amino acid sequences, Nanobodies4' or polypeptides of the invention may be linked (optionally via a suitable linker or hinge region) to naturally occurring, synthetic or semisynthetic constant domains (or analogs, variants, mutants, parts or fragments thereof) that have a reduced (or essentially no) tendency to self-associate into dimers (i.e. compared to constant domains that naturally occur in conventional 4-chain antibodies). Such monomeric (i.e. not self-associating) Fc chain variants, or fragments thereof, will be dear to the skilled person. For example, Helm et si,, i Siol Chern 1996 2717494, describe monomeric Fc chain variants that can be used in the poiypeptide chains of the invention.

Also, such monomeric Fc chain variants are preferably such that they are still capable of binding to the complement or the relevant rc receptor(s) (depending on the Fc portion from which they are derived), and/or such that they still have some or all of the effector functions of the Fc portion from which they are derived (or at a reduced leve! still suitable for the intended use). Alternatively, in such a polypeptide chain of the invention, the monomeric Fc chain may be used to confer increased half-life upon the poiypeptide chain, in which case the monomeric Fc chain may aiso have no or essentially no effector functions.

Generally, the amino acid sequences, Nanobodies® or polypeptides of the invention (or compounds, constructs or comprising the same) with increased half-life preferably have a half-life that is at least 1.5 times, preferably at least 2 times, such as at least 5 times, for example at least 10 times or more than 20 times, greater than the half-life of the corresponding amino acid sequence, Nanobody® or poiypeptide of the invention per se. For example, the amino acid sequences, Nanobodies®, compounds, constructs or polypeptides of the invention with increased half-iife may have a half-iife that is increased with more than 1 hours, preferably more than 2 hours, more preferably more than 6 hours, such as more than 12 hours, or even more than 24, 48 or 72 hours, compared to the corresponding amino acid sequence, Nanobody® or polypeptide of the invention perse. in a preferred, but non-iimiting aspect of the invention, such amino acid sequences, Nanobodies®, compound, constructs or polypeptides of the invention exhibit a serum haif-life in human of at least about 12 hours, preferably at least 24 hours, more preferably at least 4S hours, even more preferably at least 72 hours or more. For example, compounds or polypeptides of the invention may have a half-life of at least 5 days (such as about 5 to 10 days), at preferably at least 9 days (such as about 9 to 14 days), more preferably at least about 10 days (such as about 10 to 15 days), or at least about 11 days (such as about 11 to 16 days), more preferably at least about 12 days (such as about 12 to IS days or more), or more than 14 days (such as about 14 to 19 days).

The further amino add sequences may also form a signal sequence or leader sequence that directs secretion of the amino acid sequence, Nanobody® or the polypeptide of the invention from a host cell upon synthesis (for example to provide a pre-, pro- or prepro- form of the polypeptide of the invention, depending on the host cel! used to express the polypeptide of the Invention).

The further amino acid sequence may also form a sequence or signal that allows the amino acid sequence, Nanobody's or poiypeptide of the invention to be directed towards and/or to penetrate or enter into specific organs, tissues, ceils, or parts or compartments of celis, 3nd/or that allows the amino acid sequence, Nanobody® or polypeptide of the invention to penetrate or cross a biological barrier such as a cell membrane, a cell layer such as a layer of epithelial cells. Suitable examples of such amino acid sequences will be clear to the skilled person, and for example include, but are not limited to, the "Peptrans'’ vectors mentioned above, the sequences described by Cardinale et al. and the amino acid sequences and antibody fragments known per se that can be used to express or produce the Nanobodies® and polypeptides of the invention as so-called "intrabodies", for example as described in WO 94/02610, WO 95/22618, US 7,004,940, WO 03/014960, WO 99/07414; WO 05/01690; EP 1512 696; and in Cattaneo, A. & Biocca, S. (1997) intracellular Antibodies: Development and Applications. Landes and Springer-Verlag; and in Kontermann,

Methods 34, (2004), 163-170, and the further references described therein.

Such a protein, polypeptide, compound or construct may also be in essentially isolated form (as defined herein).

The compounds or polypeptides of the invention can generally be prepared by a method which comprises at least the step of suitably linking the one or more amino acid sequences, Nanobodies®, monovalent constructs and/or polypeptides of the invention to the one or more further groups, residues, moieties or binding units, optionally via the one or more suitable linkers, so as to provide the compound or poiypeptide of the invention. Polypeptides of the invention can also be prepared by a method which generally comprises at least the steps of providing a nucleic acid that encodes a polypeptide of the invention, expressing said nucleic acid in a suitable manner, and recovering the expressed polypeptide of the invention. Such methods can be performed in a manner known perse, which will be dear to the skilled person, for example on the basis of the methods and techniques further described herein.

Suitable spacers or linkers for use in multivalent and/or multispecific polypeptides or constructs will be dear to the skilled person, and may generally be any linker or spacer used in the art to link amino add sequences. Preferably, said linker or spacer is suitable for use in constructing proteins or polypeptides that are intended for pharmaceutical use.

Some particularly preferred spacers include the spacers and linkers that are used in the art to link antibody fragments or antibody domains. These include the linkers mentioned in the genera! background art cited above, as well as for example linkers that are used in the art to construct atabodies or ScFv fragments (in this respect, however, its should be noted that, whereas in diabodies and in ScFv fragments, the linker sequence used should have a length, a degree of flexibility and other properties that allow the pertinent and VL domains to come together to form the complete antigen-binding site, there is no particular limitation on the length or the flexibility of the linker used in the polypeptide of the invention, since each amino acid sequence or Nanobody4' by itself forms a complete antigen-binding site).

For example, a linker may be a suitable amino acid sequence, and in particular amino acid sequences of between 1 and 50, preferably between i and 30, such as between 1 and 10 amino acid residues. Some preferred examples of such amino acid sequences include giy-ser linkers, for example of the type {g!y*serv)„ such as (for example (glyjser)3 or (gly3ser2)j, as described in WO 99/42077, hinge-like regions such as the hinge regions of naturally occurring heavy chain antibodies or similar sequences (such as described in WO 94/04678).

Some other particularly preferred linkers are poly-alanine (such as AAA), as well as the linkers mentioned in Table A-7, of which GS15 is particularly preferred.

Other suitable linkers generally comprise organic compounds or polymers, in particular those suitable for use in proteins for pharmaceutical use. For instance, poiy(ethylenegiycol) moieties have been used to link antibody domains, see for example WO 04/081026. it is encompassed within the scope of the invention that the length, the degree of flexibility and/or other properties of the linker(s) used (although not critical, as it usually is for linkers used in ScFv fragments) may have some influence on the properties of the final polypeptide of the invention, including but not limited to the affinity, specificity or avidity for protein F of hRSV, or for one or more of the other antigens. Based on the disclosure herein, the skilled person will be able to determine the optimal iinker(s) for use in a specific polypeptide of the invention, optionally after some limited routine experiments. it is also within the scope of the invention that the iinker(s) used confer one or more other favourable properties or functionality to the polypeptides of the invention, and/or provide one or more sites for the formation of derivatives and/or for the attachment of functional groups (e.g. as described herein for the derivatives of the amino acid sequences, Nanobodies®, compounds and polypeptides of the invention). For example, linkers containing one or more charged amino acid residues can provide improved hydrophilic properties, whereas linkers that form or contain small epitopes or tags can be used for the purposes of detection, identification and/or purification. Again, based on the disclosure herein, the skilled person will be able to determine the optimal linkers for use in a specific polypeptide of the invention, optionally after some limited routine experiments.

Finally, when two or more linkers are used in the polypeptides of the invention, these linkers may be the same or different. Again, based on the disclosure herein, the skilled person will be able to determine the optimal linkers for use in a specific polypeptide of the invention, optionally after some limited routine experiments.

Usually, for ease of expression and production, a polypeptide of the invention will be a linear polypeptide. However, the invention in its broadest sense is not limited thereto. For example, when a polypeptide of the invention comprises three of more amino add sequences or Nanobodies®, it is possible to link them by use of a linker with three or more "arms", which each "arm" being linked to an amino acid sequence or Nanobody®, so as to provide a "star-shaped" construct. It is also possible, although usually less preferred, to use circular constructs.

As will also be clear from the disclosure herein, it is also within the scope of the invention to use parts or fragments, or combinations of two or more parts or fragments, of the amino acid sequences, Nanobodies8’ or polypeptides of the invention as defined herein, and in particular parts or fragments of the amino acid sequences of SEQ ID NO's: 60-76,138-141 and 146-157 or the polypeptides of SEQ ID NO's: 77-79,142-145 and 158-165. Thus, according to one embodiment of the invention, the term "amino acid sequence of the invention", "Nanobody® of the invention" and "polypeptide of the invention" in its broadest sense also covers such parts or fragments.

Generally, such parts or fragments of the amino acid sequences, Nanobodies® or polypeptides of the invention (including variants thereof as defined herein) have amino add sequences in which, compared to the amino acid sequence of the corresponding full iength amino acid sequence or Nanobody® of the invention, one or more of the amino acid residues at the N-terminal end, one or more amino acid residues at the C-terminal end, one or more contiguous internal amino acid residues, or any combination thereof, have been deleted and/or removed.

The parts or fragments are preferably such that they can bind to antigenic site It on protein F of hRSV, with an affinity (suitably measured and/or expressed as a KP-value (actual or apparent), a KA-value (actual or apparent), a kDll-rate and/or a kofrrate, or alternatively as an ICS0 value, as further described herein) that is as defined herein.

In particular, amino acid sequences, Nanobodies®, polypeptides and parts or fragments are preferably such that they: bind to protein F of hRSV with a dissociation constant (K0) of 1000 nIVt to 1 nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less: and/or such that they: bind to protein F of hRSV with a kor-rate of between 104 M'V1 to about 107 M'V*1, preferably between 10s M'V1 and 107 M'V1, more preferably about 10” M'V1 or more; and/or such that they: bind to protein F of hRSV with a k0# rate between IQ'4 s"1 (tyi*0.69 s} and lO'4 s'" (providing a near irreversible complex with a b/i of multiple days), preferably between I0's s'1 and IQ"1 s'J, or lower.

The affinity of the parts or fragments against protein F of hRSV, can be determined in a manner known per se, for example using the assay described herein.

Such parts or fragments will usually also have a hRSV neutraiitation efficacy and/or potency as defined herein.

Any part or fragment is preferably such that it comprises at least 10 contiguous amino acid residues, preferably at least 20 contiguous amino acid residues, more preferably at ieast 30 contiguous amino acid residues, such as at ieast 40 contiguous amino acid residues, of the amino acid sequence of the corresponding full length amino add sequence. Nanobody® or polypeptide of the invention.

Aiso, any part or fragment is such preferably that it comprises at ieast one of the CDR’s (and preferably at least CDR3 or part thereof} and at ieast one other CDR (La. CDR1 or CDR2) or at least part thereof, preferably connected by suitable framework sequence(s) or at ieast part thereof. More preferably, any part or fragment is such that it comprises at least one of the CDR's (and preferably at ieast CDR3 or part thereof) and at least part of the two remaining CDR's, again preferably connected by suitable framework sequence(s) or at ieast part thereof.

According to another particularly preferred, but non-limiting embodiment, such a part or fragment comprises at least CDR3, such as FR3, CDR3 and FR4 of the corresponding full length Nanobody® of the invention, i.e. as for example described in the international application WO 03/050531 (Lasters et a!.).

As already mentioned above, it is also possible to combine two or more of such parts or fragments (i.e. from the same or different amino acid sequences or Nanobodies* of the invention}, i.e. to provide further parts or fragments (as defined herein) of an amino acid sequence, a Nanobody® or a polypeptide of the invention. It is for example also possible to combine one or more parts or fragments of an amino add sequence, a Nanobody® or a polypeptide of the invention with one or more parts or fragments of a human VH domain.

According to one preferred embodiment, the parts or fragments have a degree of sequence identity of at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, such as at least 90%, 95% or 99% or more with one of the amino acid sequences or Nanobodies® of SEQ, ID NO's: 50-76,138-141 and 145-157 or with one of the polypeptides of SEQ SD NO's: 77-79,142-145 and 158-165.

The parts and fragments, and nucleic acid sequences encoding the same, can be provided and optionally combined in any manner known perse. For example, such parts or fragments can be obtained by inserting a stop codon in a nucleic acid that encodes a full-sized amino acid sequence, Nanobody® or polypeptide of the invention, and then expressing the nucleic acid thus obtained in a manner known per se (e.g. as described herein). Alternatively, nucleic acids encoding such parts or fragments can be obtained by suitably restricting a nucieic acid that encodes a full-sized amino acid sequence, Nanobody® or polypeptide of the invention or by synthesizing such a nucleic acid in a manner known per se. Parts or fragments may also be provided using techniques for peptide synthesis known per se.

The invention in its broadest sense aiso comprises derivatives of the amino acid sequences, Nanobodies®, compounds or polypeptides of the invention. Such derivatives can generally be obtained by modification, and in particular by chemical and/or biological (e.g. enzymaticai) modification, of the amino acid sequences, Nanobodies®, compounds or polypeptides of the invention and/or of one or more of the amino acid residues that form the amino acid sequences, Nanobodies*, compounds or polypeptides of the invention.

Examples of such modifications, as well as examples of amino acid residues within the amino acid sequence, Nanobody® sequence, compound or polypeptide sequences that can be modified in such a manner (E.e. either on the protein backbone but preferably on a side chain), methods and techniques that can be used to introduce such modifications and the potential uses and advantages of such modifications will be clear to the skilled person.

For example, such a modification may involve the introduction (e.g. by covalent linking or in an other suitable manner) of one or more functional groups, residues or moieties into or onto the amino acid sequence, Nanobody*’, compound or polypeptide of the invention, and in particular of one or more functional groups, residues or moieties that confer one or more desired properties or functionalities to the amino add sequence, Nanobody®, compound or polypeptide of the invention. Example of such functional groups will be clear to the skilled person.

For example, such modification may comprise the introduction (e.g. by covalent binding or in any other suitable manner) of one or more functional groups that that increase the half-life, the solubility and/or the absorption of the amino acid sequence, Nanobody®, compound or polypeptide of the invention, that reduce the immunogenicity and/or the toxicity of the amino acid sequence, Nanobody6, compound or polypeptide of the invention, that eliminate or attenuate any undesirable side effects of the amino acid sequence, Nanobody*, compound or polypeptide of the invention, and/or that confer other advantageous properties to and/or reduce the undesired properties of the amino acid sequence, Nanobody®, compound or poiypeptide of the invention; or any combination of two or more of the foregoing. Examples of such functional groups and of techniques for introducing them will be clear to the skilled person, and can generally comprise aii functional groups and techniques mentioned in the general background art cited hereinabove as well as the functional groups and techniques known per se for the modification of pharmaceutical proteins, and in particular for the modification of antibodies or antibody fragments (including ScFv's and single domain antibodies), for which reference is for example made to Remington's Pharmaceutical Sciences, 16th ed„ Mack Publishing Co., Easton, PA (1980). Such functional groups may for example be linked directly (for example covalently) to an amino acid sequence, Nanobody®, compound or polypeptide of the invention, or optionally via a suitable linker or spacer, as will again be clear to the skilled person.

One of the most widely used techniques for increasing the half-life and/or reducing the immunogenicity of pharmaceutical proteins comprises attachment of a suitable pharmacologically acceptable polymer, such as poly(ethyleneglycol) (PEG) or derivatives thereof (such as methoxypoly(ethylenegiycoi) or mPEG). Generally, any suitable form of pegyiation can be used, such as the pegyiation used in the art for antibodies and antibody fragments (including but not limited to (single) domain antibodies and ScFv's); reference is made to for example Chapman, Nat. Biotechno!., 54, 531-545 (2002); by Veronese and Harris, Adv. Drug Deliv, Rev. 54,453-456 (2003), by Harris and Chess, Nat. Rev. Drug. Discov., 2, (2003) and in WO 04/060965. Various reagents for pegyiation of proteins are also commercially available, for example from Nektar Therapeutics, USA.

Preferably, site-directed pegyiation is used, in particular via a cysteine-residue (see for example Yang et al., Protein Engineering, 16,10, 751-770 (2003). For example, for this purpose, PEG may be attached to a cysteine residue that naturally occurs in an amino acid sequence, Nanobody®, compound or poiypeptide of the invention, an amino acid sequence, Nanobody®, compound or polypeptide of the invention may be modified so as to suitably introduce one or more cysteine residues for attachment of PEG, or an amino acid sequence comprising one or more cysteine residues for attachment of PEG may be fused to the N- and/or C-terminus of an amino acid sequence, Nanobody'*', compound or polypeptide of the invention, all using techniques of protein engineering known per se to the skilled person.

Preferably, forthe amino acid sequences. Nanobodies®·, compounds or polypeptides of the invention of the invention, a PEG is used with a molecular weight of more than 5000, such as more than 10,000 and less than 200,000, such as less than 100,000; for example in the range of 20,000-80,000.

Another, usually less preferred modification comprises N-linked or O-linked glycosyiation, usually as part of co-translational and/or post-translational modification, depending on the host ceil used for expressing the amino acid sequence, Nanobody®, compound or polypeptide of the invention.

Yet another modification may comprise the introduction of one or more detectable labels or other signal-generating groups or moieties, depending on the intended use of the labelled amino acid sequence, Nanobody®, compound or polypeptide of the invention. Suitable labels and techniques for attaching, using and detecting them will be clear to the skilled person, and for example include, but are not limited to, fluorescent labels (such as fluorescein, isothiocyanate, rhodamine, phycoerythrin, phycocyanin, ailophycocyanin, o-phthaldehyde, and fluorescamine and fluorescent metals such as ls2Eu or others metals from the lanthanide series}, phosphorescent labels, chemiluminescent labels or bioiuminescent labels (such as luminal, isoluminol, tberomatic acridinium ester, imidazoie, acridinium salts, oxalate ester, dioxetane or GFP and its analogs}, radio-isotopes (such as "H, i?sl, 3iP, 35S, 34C, 5lCr, 5bCI, 57Co, ssCo, 5SFe, and 7:Se), metals, metals chelates or metallic cations (for example metallic cations such as """Tc, 1HI, mln, i31l, S7Ru, 67Cu, 6'Ga, and 6&Ga or other metals or metallic cations that are particularly suited for use in in vivo, in vitro or in situ diagnosis and imaging, such as (S57Gd, ssMn, ib2Dy, 54Cr, and S6Fe), as well as chromophores and enzymes (such as malate dehydrogenase, staphylococcal nuclease, delta-V-steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, biotlnavidin peroxidase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, β-galactosidase, ribonuclease, urease, catalase, glucose-Vl-phosphate dehydrogenase, glucoamylase and acetylcholine esterase). Other suitable labels will be clear to the skilled person, and for example include moieties that can be detected using NMR or ESR spectroscopy.

Such labelled amino acid sequences, Nanobodies®, compounds or polypeptides of the invention may for example be used for in vitro, in vivo or in situ assays (including immunoassays known per se such as ELISA, RIA, EIA and other "sandwich assays", etc.) as well as in vivo diagnostic and imaging purposes, depending on the choice of the specific label.

As will be dear to the skilled person, another modification may involve the introduction of a chelating group, for example to chelate one of the metals or metallic cations referred to above. Suitable chelating groups for example include, without limitation, diethyi-enetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA).

Yet another modification may comprise the introduction of a functional group that is one part of a specific binding pair, such as the biotsn-{strept)avidin binding pair. Such a functional group may be used to link the amino add sequence, Nanobody®, compound or polypeptide of the invention to another protein, polypeptide or chemical compound that is bound to the other half of the binding pair, i.e. through formation of the binding pair. For example, an amino acid sequence, Nanobody®, compound or polypeptide of the invention may be conjugated to biotin, and linked to another protein, polypeptide, compound or carrier conjugated to avidin or streptavidin. For example, such a conjugated amino acid sequence, Nanobody*, compound or polypeptide of the invention may be used as a reporter, for example in a diagnostic system where a detectable signal-producing agent is conjugated to avidin or streptavidin. Such binding pairs may for example also be used to bind the amino acid sequence. Nanobody*, compound or polypeptide of the invention to a carrier, including carriers suitable for pharmaceutical purposes. One non-limiting example are the liposomal formulations described by Cao and Suresh, Journal of Drug Targeting, S, 4, 257 (2000). Such binding pairs may also be used to iink a therapeutically active agent to the amino acid sequence, Nancbody®, compound or polypeptide of the invention.

Other potential chemical and enzvmaticai modifications will be clear to the skilled person. Such modifications may also be introduced for research purposes (e.g. to study function-activity relationships). Reference is for example made to Lundblad and Bradshaw, Biotechnol. App!.

Biochem., 25,143-151 (1997).

Preferably, the derivatives are such that they bind to protein F of hRSV, with an affinity (suitably measured and/or expressed as a KD-value (actual or apparent), a KA-vaiue (actual or apparent), a kon-rate and/or a karate, or alternatively as an IC6S vaiue, as further described herein) that is as defined herein (i.e. as defined for the amino acid sequences, Nanobodies*, polypeptides or compounds per se). Such derivatives wifi usually also have a hRSV neutralization efficacy and/or potency as defined herein.

As mentioned above, the invention also relates to proteins or polypeptides that essentially consist of or comprise at least one amino acid sequence, Nanobody*, compound or polypeptide of the invention. By "essentially consist of' is meant that the amino add sequence of the protein or polypeptide of the invention either is exactly the same as the amino acid sequence, Nanobody*, compound or polypeptide of the invention or corresponds to the amino acid sequence, Nanobody®, compound or polypeptide of the invention which has a limited number of amino acid residues, such as 1-20 amino acid residues, for example 1-10 amino acid residues and preferably 1-6 amino acid residues, such as 1,2, 3, 4,5 or 6 amino acid residues, added at the amino terminal end, at the carboxy terminal end, or at both the amino terminal end and the carboxy terminal end of the amino acid sequence. Nanobody®, compound or poiypeptide.

Said amino acid residues may or may not change, alter or otherwise influence the (biological) properties of the amino acid sequence, Nanobody®, compound or polypeptide of the invention and may or may not add further functionality to the amino acid sequence, Nanobody®, compound or poiypeptide. For example, such amino acid residues: a) can comprise an N-terminai Met residue, for example as result of expression in a heteroiogous host cell or host organism. b) may form a signal sequence or leader seauence that directs secretion of the amino acid sequence, Nanobody®, compound or polypeptide from a host cell upon synthesis. Suitable secretory' leader peptides will be clear to the skilled person, and may be as further described herein. Usually, such a leader sequence will be linked to the N-terminus of the amino acid sequence, Nanobody®, compound or polypeptide, although the invention in its broadest sense is not limited thereto; c) may form a sequence or signal that allows the amino acid sequence, Nanobcdy®, compound or polypeptide to be directed towards and/or to penetrate or enter into specific organs, tissues, cells, or parts or compartments of cells, and/or that allows the amino acid sequence,

Nanobody®, compound or polypeptide to penetrate or cross a biological barrier such as a ceii membrane, a cell layer such as a layer of epithelial cells, a tumor including solid tumors, or the biood-brain-barrier. Examples of such amino acid sequences wit! be ciear to the skilled person. Some non-limiting examples are the small peptide vectors ("Pep-trans vectors") described in WO 03/026700 and in Temsamani et alv Expert Opin. Biol, Then, 1, 773 (2001); Tems3mani and Vidal, Drug Discov. Today, 9,1012 (004) and Rousselle, J. Pharmacol. Exp. Ther., 296,124-131 (2001), and the membrane translocator sequence described by Zhao et ai., Apoprosis, 8. 631-637 (2003). C-termmal and N-termina! amino acid sequences for intracellular targeting of antibody fragments are for example described by Cardinale et a!., Methods, 34,171 (2004). Other suitable techniques for intracellular targeting involve the expression and/cr use of so-called "intrabodies" comprising a amino acid sequence, Nanobody8, compound or polypeptide of the invention, as mentioned below; d) may form a "tag", for example an amino acid sequence or residue that allows or facilitates the purification of the amino acid sequence, Nanobody®, compound or polypeptide, for example using affinity techniques directed against said sequence or residue. Thereafter, said sequence or residue may be removed (e.g. by chemical or enzymaticai cleavage) to provide the amino acid sequence, Nanobody®, compound or polypeptide (for this purpose, the tag may optionally be linked to the amino acid sequence. Nanobody®, compound or poiypeptide sequence via a cleavable linker sequence or contain a cleavabie motif). Some preferred, but non-limiting examples of such residues are multiple histidine residues, giutatione residues and a myc-tag SUCh as AAAEQKUSEEDLNGAA (SEQ iD NO: 111); e) may be one or more amino acid residues that have been functionalized and/or that can serve as a site for attachment of functional groups. Suitable amino acid residues and functional groups will be dear to the skilled person and include, but are not limited to, the amino acid residues and functional groups mentioned herein for the derivatives of the amino acid sequences, Nanobodies1®, compounds or polypeptides of the invention.

The invention further relates to methods for preparing the amino acid sequences, Nanobodies*, polypeptides, compounds, nucleic acids, host celis, products and compositions described herein.

The amino acid sequences, Nanobodies6, poiypeptides, compounds and nucleic acids of the invention can be prepared in a manner known per se, as will be ciearto the skilled person from the further description herein. For example, the amino acid sequences, Nanobodies*' and poiypeptides of the invention can be prepared in any manner known per se for the preparation of antibodies and in particular for the preparation of antibody fragments (including but not limited to (single) domain antibodies and ScFv fragments). Some preferred, but non-limiting methods for preparing the amino acid sequences, Nanobodies6, polypeptides and nucleic acids include the methods and techniques described herein.

The method for producing an amino add sequence of the invention, a Nanobody® of the invention, a polypeptide of the invention, or a monovalent construct of the invention may comprise the following steps: - the expression, in a suitable hostceli or host organism (also referred to herein as a "host of the invention") or in another suitable expression system of a nucleic acid that encodes said amino acid sequence, Nanobody® or polypeptide of the invention (also referred to herein as a "nucleic add of the invention"), optionally followed by: - isolating and/or purifying the amino add sequence, Nanobody® or polypeptide of the invention thus obtained.

In particuiar, such a method may comprise the steps of: - cultivating and/or maintaining a host of the invention under conditions that are such that said host of the invention expresses and/or produces at least one amino acid sequence, Nanobody® and/or polypeptide of the invention; optionally followed by: - isolating and/or purifying the amino acid sequence, Nanobody*' or polypeptide of the invention thus obtained.

Accordingly, the present invention also relates to a nucleic add or nucleotide sequence that encodes an amino add sequence, a Nanobody* , a polypeptide or a monovalent construct of the invention {also referred to as "nucleic acid of the invention" or "nucleotide sequence of the invention"). A nucleic acid of the invention can be in the form of single or double stranded ONA or RNA, and is preferably in the form of double stranded DNA. For example, the nucleotide sequences of the invention may be genomic DNA, cDNA or synthetic DNA (such as DNA with a codon usage that has been specifically adapted for expression in the intended host cel! or host organism).

According to one embodiment of the invention, the nucleic acid of the invention is in essentially isolated from, as defined herein. The nucleic add of the invention may aiso be in the form of, be present in and/or be part of a vector, such as for example a plasmid, cosmtd or YAC, which again may be in essentially isolated form.

The nucleic acids of the invention can be prepared or obtained in a manner known per se, based on the information on the amino acid sequences, Nanobodies4' and/or polypeptides of the invention given herein, and/or can be isolated from a suitable natural source. Also, as will be clear to the skilled person, to prepare a nucleic acid of the invention, also several nucleotide sequences, such as at least one nucleotide sequence encoding an amino acid sequence or Nanobodye and for example nucleic acids encoding one or more linkers can oe linked together in a suitable manner.

Techniques for generating the nucleic adds of the invention wiii be dear to the skilled person and may for instance include, but are not limited to, automated DNA synthesis; site-directed mutagenesis; combining two or more naturally occurring and/or synthetic sequences {or two or more parts thereof), introduction of mutations that iead to the expression of a truncated expression product; introduction of one or more restriction sites {s.g. to create cassettes and/or regions that may easily be digested and/or ligated using suitable restriction enzymes), and/or the introduction of mutations by means of a PCR reaction using one or more "mismatched" primers. These and other techniques will be clear to the skilled person, and reference is again made to the standard handbooks, such as Sambrook et al. and Ausubel et a!., mentioned above, as well as the Examples below.

The nucleic acid of the invention may also be in the form of, be present in and/or be part of a genetic construct, as will be clear to the person skilled in the art. Such genetic constructs generally comprise at least one nucleic acid of the invention that is optionally linked to one or more elements of genetic constructs known per se, such as for example one or more suitable regulatory elements (such as a suitable promoters), enhancer(s), terminator(s), etc.) and the further elements of genetic constructs referred to herein. Such genetic constructs comprising at least one nucleic add of the invention will aiso be referred to herein as "genetic constructs of the invention".

The genetic constructs of the invention may be DNA or RNA, and are preferably double-stranded DMA. The genetic constructs of the invention may also be in a form suitable for transformation of the intended host cell or host organism, in a form suitable for integration into the genomic DNA of the intended host cell or in a form suitable for independent replication, maintenance and/or inheritance in the intended host organism. For instance, the genetic constructs of the invention may be in the form of a vector, such as for example a plasmid, cosmid, YAC, a viral vector or transposon. In particular, the vector may be an egression vector, i,e. a vector tnat can provide for expression in vitro and/or in vivo {e.g. in a suitable host ceii, host organism and/or expression system),

In a preferred but non-limiting embodiment, a genetic construct of the invention comprises a) at least one nucleic acid of the invention; operably connected to b) one or more regulatory elements, such as a promoter and optionally a suitable terminator; and optionally also c) one or more further elements of genetic constructs known per se; in which the terms "regulatory element", "promoter", "terminator" and "operably connected" have their usual meaning in the art (asfurtner described herein); and in which said "further elements" present in the genetic constructs may for example be 3'- or S'-UTP. sequences, leader sequences, selection markers, expression markers/reporter genes, and/or elements that may facilitate or increase (the efficiency of) transformation or integration. These and other suitable elements for such genetic constructs will be dear to the skilled person, and may for Instance depend upon the type of construct used; the intended host cell or host organism; the manner in which the nucleotide sequences of the invention of interest are to be expressed (e.g. via constitutive, transient or inducible expression); and/or the transformation technique to be used. For example, regulatory sequences, promoters and terminators known per se for the expression and production of antibodies and antibody fragments (including but not iimited to (single) domain antibodies and ScFv fragments) may be used in an essentially analogous manner.

Preferably, in the genetic constructs of the invention, said at least one nucleic acid of the invention and said regulatory elements, and optionally said one or more further elements, are "operably linked" to each other, by which is generally meant that they are in a functional relationship with each other. For instance, a promoter is considered "operably linked" to a coding sequence if said promoter is able to initiate or otherwise control/regulate the transcription and/or the expression of a coding sequence (in which said coding sequence should be understood as being "under the control of" said promoter). Generally, when two nucleotide sequences are operably linked, they will be in the same orientation and usually also in the same reading frame. They will usually also be essentially contiguous, although this may aiso not be required.

Preferably, the regulatory and further elements of the genetic constructs of the invention are such that they are capable of providing their intended biological function in the intended host cell or host organism.

For instance, a promoter, enhancer or terminator should be "operable" in the intended host cell or host organism, by which is meant that (for example) said promoter should be capable of initiating or otherwise controiling/reguiating the transcription and/or the expression of a nucleotide sequence - e.g. a coding sequence - to which it is operably linked (as defined herein).

Some particularly preferred promoters include, but are not limited to, promoters known per se for the expression in the host cells mentioned herein; and in particular promoters for the expression in the bacteria! cells, such as those mentioned herein and/or those used in the Examples. A selection marker shouid be such that it allows * i.e. under appropriate selection conditions -host cells and/or host organisms that have been (successfully) transformed with the nucleotide sequence of the invention to be distinguished from host cells/organisms that have not been (successfully) transformed. Some preferred, but non-iimiting examples of such markers are genes that provide resistance against antibiotics (such as kanamycin or ampiciliin), genes that provide for temperature resistance, or genes that allow the host cell or host organism to be maintained in the absence of certain factors, compounds and/or (food) components in the medium that are essential for survival of the ηοη-transformed cells or organisms. A ieader sequence shouid be such that - in the intended host ceil or host organism - it allows for the desired post-fransiational modifications and/or such that it directs the transcribed mRNAto a desired part or organelle of a ceil. A ieader sequence may also allow for secretion of the expression product from said ceil. As such, the ieader sequence may be any pro-, pre-, or prepro-sequence operable in the host ceil or host organism. Leader sequences may not be required for expression in a bacteria! ceil. For example, leader sequences known per se for the expression and production of antibodies and antibody fragments (including but not limited to single domain antibodies and ScFv fragments) may be used in an essentially analogous manner.

An expression marker or reporter gene should be such that - in the host ceil or host organism - it allows for detection of the expression of (a gene or nucleotide sequence present on) the genetic construct. An expression marker may optionally aiso allow for the localisation of the expressed product, e.g. in a specific part or organelle of a ceil and/or in (a) specific cell(s), tissue(s), organ(s) or part(s) of a multicellular organism. Such reporter genes may also be expressed as a protein fusion with the amino acid sequence, Nanobody® or polypeptide of the invention. Some preferred, but non-iimiting examples include fluorescent proteins such as GFP.

Some preferred, but non-iimiting examples of suitable promoters, terminator and further elements include those that can be used for the expression in the host cells mentioned herein; and in particular those that are suitable for expression in bacterial cells, such as those mentioned herein and/or those used in the Examples below. For some (further) non-limiting examples of the promoters, selection markers, leader sequences, expression markers and further elements that may be present/used in the genetic constructs of the invention - such as terminators, transcriptional and/or translational enhancers and/or integration factors - reference is made to the general handbooks such as Sambrook et al. and Ausubel et al. mentioned above, as well as to the examples that are given in WO 95/07463, WO 96/23810, WO 95/07463, WO 95/21191, WO 97/11094, WO 97/42320, WO 98/06737, WO 98/21355, US-A-7,207,410, US-A- 5,693,432 and EP 1085 089. Other examples will be clear to the skilled person. Reference is also made to the general background an cited above and the further references cited herein,

The genetic constructs of the invention may generally be provided by suitably linking the nucleotide sequence(s) of the invention to the one or more further elements described above, for example using the techniques described in the genera! handbooks such as Sambrook er al. and Ausubel et a!., mentioned above.

Often, the genetic constructs of the invention will be obtained by inserting a nucleotide sequence of the invention in a suitable (expression) vector known per se. Some preferred, but nonlimiting examples of suitable expression vectors are those used in the Examples below, as well as those mentioned herein.

The nucleic acids of the invention and/or the genetic constructs of the invention may be used to transform a host ceil or host organism, i.e. for expression and/or production of the amino acid sequence, Nanobody® or polypeptide of the invention. Suitable hosts or host cells wiil be dear to the skilled person, and may for example be any suitable fungal, prokaryotic or eukaryotic ceil or ceil iine or any suitable fungal, prokaryotic or eukaryotic organism, for example: - a bacterial strain, including but not limited to gram-negative strains such as strains of Escherichia coli; of Proteus, for example of Proteus mirabiiis; of Pseudomonas, for example of Pseudomonas fiuorescens; and gram-positive strains such as strains of Bacillus, for example of Bacillus subtilis or of Bacillus brevis; of Streptomyces, for example of Streptomyces lividans; of Staphylococcus, for example of Staphylococcus carnosus; and of Lactococcus, for example of Lactococcus lactis; - a fungal cell, including but not limited to cells from species of Trichoderma, for example from Trichoderma reesei·, of Neurospora, for example from Neurospora crassa; of Sordaria, for example from Sordaria macrospora·, of Aspergillus, for example from Aspergillus niger or from Aspergillus sojae; or from other filamentous fungi; - a yeast ceil, including but not limited to ceils from species of Saccharomyces, for example of Saccharomyces cerevisiae; of Schizosaccharomyces, for example of Schizosaccbarornyces pombe; of Pichia, for exam pie of Pichia pastoris or of Pichia methanolica; of Hansenula, for example of

Honsenuia potymorpha; of Kiuyveromyces, for example of Kiuyveromyces lactis; ot Arxuia, for example of Arxuia adeninivorans; of Yorrowia, for example of Yarrowia lipolytica; - an amphibian cell or cell iine, such as Xenopus oocytes; - an insect-derived ceil or cell line, such as cells/cell lines derived from iepidoptera, including but not limited to Spodoptera SF9 and Sf21 cells or cells/cell lines derived from Drosophila, such as Schneider and Kc cells; - a plant or plant cell, for example in tobacco plants; and/or - a mammalian cell or ceil line, for example a cell or cell line derived from a human, a cell or a cell line from mammals including but not limited to CHO-celis, BHK-cells (for example BHK-21 cells) and human cells or cell lines such as HeLa, COS (for example COS-7) and PER.C6 cells; as well as all other hosts or host cells known per se for the expression and production of antibodies and antibody fragments (including but not iimited to (single) domain antibodies and ScFv fragments), which will be clear to the skilled person. Reference is also made to the general background art cited hereinabove, as well as to for example WO 94/29457; WO 96/34103; WO 99/42077; Frenken et a!., (1998), supra; Riechmann and Muyldermans, (1999), supra; van der Linden, (2000), supra;

Thomassen et al., (2002), supra; Joosten et a!., (2003), supra; Joosten et at., (2005), supra; and the further references cited herein.

The amino acid sequences, Nanobodies® and polypeptides of the invention can also be introduced and expressed in one or more cells, tissues or organs of a multicellular organism, for example for prophylactic and/or therapeutic purposes (e.g. as a gene therapy). For this purpose, the nucleotide sequences of the invention may be introduced into the cells or tissues in any suitable way, for example as such (e.g. using liposomes) or after they have been inserted into a suitable gens therapy vector (for example derived from retroviruses such as adenovirus, or parvoviruses such as adeno-associated virus). As will also be clear to the skilled person, such gene therapy may be performed in vivo and/or in situ in the body of a patient by administering a nucleic acid of the invention or a suitable gene therapy vector encoding the same to the patient or to specific ceils or a specific tissue or organ of the patient; or suitable ceils (often taken from the body of the patient to be treated, such as explanted lymphocytes, bone marrow aspirates or tissue biopsies) may be treated in vitro with a nucleotide sequence of the invention and then be suitably (re-)introduced into the body of the patient. All this can be performed using gene therapy vectors, techniques and delivery systems which are well known to the skilled person, and for example described in Culver, K, W., "Gene Therapy", 1994, p. xii, Mary Ann Liebert, inc., Publishers, New York, N.Y); Giordano, Nature F Medicine 2 (1996), 534-539; Schaper, Circ. Res. 79 (1996), 911-919; Anderson, Science 256 (1992),808-813; Verma, Nature 389 (1994),239.: Isner, Lancet 348 ¢1996),370-374; Muhlhauser, Circ. Res. 77 (1995),1077-1086; Onodera, Blood 91; (1998),30- 36; Verma, Gene Ther. 5 (1998),692-699,-

Nabei, Ann. N.Y. Acad. Sci.; 811 {1997}.. 289*292; Verzeletti, Hum. Gene Trier. 9 (1998), 2243-51; Wang, Nature Medicine 2 (1996).714-716; WO 94/29469; WO 97/00957. US 5,580,859; US 5,5895466; or Schaper, Current Opinion in Biotechnology 7 (1996), 635-640. For example, in situ expression of ScFv fragments (Afanasieva et at., GeneTher., 10,1850-1859 (2003)) and of diabodies (Blanco et a!., J. Immunol, 171,1070-1077 (2003)) has been described in the art.

For expression of the amino acid sequences, Nanobodies'* or polypeptides in a cell, they may also be expressed as so-called "intrabodies", as for example described in WO 94/02610, WO 95/22618 and US-A-7004940; WO 03/014960; in Cattaneo, A. & Siocca, S. (1997) intracellular Antibodies: Development and Applications. Landes and Springer-VerSag; and in Kontermann,

Methods 34, (2004), 163-170.

The amino acid sequences, Nanobodies® and polypeptides of the invention can for example also be produced in the milk of transgenic mammals, for example in the milk of rabbits, cows, goats or sheep (see for example US 6,741,957, US 6,304,489 and US 6,849,992 for general techniques for introducing transgenes into mammals), in plants or parts of plants including but not limited to their leaves, flowers, fruits, seed, roots or turners (for example in tobacco, maize, soybean or alfalfa) or in for example pupae of the silkworm Bombix mori.

Furthermore, the amino arid sequences, Nanobodies® and polypeptides of the invention can aiso be expressed and/or produced in cell-free expression systems, and suitable examples of such systems will be clear to the skilled person. Some preferred, but non-iimiting examples include expression in the wheat germ system; in rabbit reticulocyte lysates; or in the £. cotiZubay system.

As mentioned above, one of the advantages of the use of Nanobodies® is that the polypeptides based thereon can be prepared through expression in a suitable bacterial system, arid suitable bacteria! expression systems, vectors, host celts, regulatory elements, etc., will be clear to the skilled person, for example from the references cited above. It should however be noted that the invention in its broadest sense is not limited to expression in bacterial systems.

Preferably, in tlie invention, an (in vivo or in vitro) expression system, such as a bacteria! expression system, is used that provides the polypeptides of the invention in a form that is suitable for pharmaceutical use, and such expression systems will again be clear to the skilled person. As also will be dear to the skilled person, polypeptides of the invention suitable for pharmaceutical use can be prepared using techniques for peptide synthesis.

For production on industrial scale, preferred heterologous hosts for the (industrial) production of Nanobodies® or Nanobody®-containing protein therapeutics include strains of £ coli, Pichia pastoriSj S. cerevisiae that are suitable for large scale expression/production/fermentation, and in particular for large scale pharmaceutical expression/productlon/fermentation. Suitable examples of such strains will be ciear to the skilled person. Such strains and production/expression systems are aiso made available by companies such as Biovitrum (Uppsala, Sweden}.

Alternatively, mammalian cell lines, in particular Chinese hamster ovary (CHO) cells, can be used for large scale expression/production/fermentation, and in particular for large scale pharmaceutical expression/production/fermentation. Again, such expression/production systems are also made available by some of the companies mentioned above.

The choice of the specific expression system would depend in part on the requirement for certain post-translational modifications, more specifically giycosyiation. The production of a Nanobodye-containing recombinant protein for which giycosyiation is desired or required would necessitate the use of mammalian expression hosts that have the ability to giycosyiate the expressed protein, in this respect, it will be clear to the skilled person that the giycosyiation pattern obtained (i.e. the kind, number and position of residues attached} will depend on the cell or cell line that is used for the expression. Preferably, either a human cell or cell line is used (i.e, leading to a protein that essentially has a human giycosyiation pattern) or another mammalian cell line is used that can provide a giycosyiation pattern that is essentially and/or functionally the same as human giycosyiation or at least mimics human giycosyiation. Generally, prokaryotic hosts such as E. coli do not have the ability to glycosylate proteins, and the use of lower eukaryotes such as yeast usually leads to a giycosyiation pattern that differs from human giycosyiation. Nevertheless, it should be understood that all the foregoing host cells and expression systems can be used in the invention, depending on the desired amino acid sequence, Nanobody® or polypeptide to be obtained.

Thus, according to one non-limiting embodiment of the invention, the amino add sequence, Nanobodv® or polypeptide of the invention is glycosylated. According to another non-limiting embodiment of the invention, the amino acid sequence, Nanobody® or polypeptide of the invention is non-glycosylated.

According to one preferred, but non-limiting embodiment of the invention, the amino acid sequence, Nanobody® or polypeptide of the invention is produced in a bacterial cell, in particular a bacterial cell suitable for large scale pharmaceutical production, such as cells of the strains mentioned above.

According to another preferred, but non-limiting embodiment of the invention, the amino add sequence, Nanobody® or polypeptide of the invention Is produced in a yeast cell in particular a yeast ceil suitable for large scale pharmaceutical production, such as cells of the species mentioned above.

According to yet another preferred, but non-iimiting embodiment of the invention, the amino acid sequence, Nanobodv® or polypeptide of the invention is produced in a mammalian cell, in particular in a human cell or in a cell of a human cell line, and more in particular in a human cell or in a celi of a human cell line that is suitable for large scale pharmaceutical production, such as the cell lines mentioned hereinabove.

When expression In a host cell is used to produce the amino acid sequences, Nanobodies® and the polypeptides of the invention, the amino acid sequences, Nanobodies® and polypeptides of the invention can be produced either intraceliuliarly (e.g. in the cytosol, in the pertplasma or in inclusion bodies) and then isolated from the host ceiis and optionally further purified; or can be produced extracellulariy (e.g. in the medium in which the host ceils are cultured) and then isolated from the culture medium and optionally further purified. When eukaryotic host cells are used, extracellular production is usually preferred since this considerably facilitates the further isolation and downstream processing of the amino acid sequences, Nanobodies®, polypeptides and proteins obtained. Bacterial cells such as the strains of E. coii mentioned above normally do not secrete proteins extracelfulariy, except for a few classes of proteins such as toxins and hemolysin, and secretory production in E. coii refers to the translocation of proteins across the inner membrane to the periplasmic space. Periplasmic production provides several advantages over cytosolic production. For example, the N-terminal amino acid sequence of the secreted product can be identical to the naturai gene product after cleavage of the secretion signal sequence by a specific signal peptidase. Also, there appears to be much less protease activity in the periplasm than in the cytoplasm. In addition, protein purification is simpler due to fewer contaminating proteins in the periplasm. Another advantage is that correct disulfide bonds may form because the periplasm provides a more oxidative environment than the cytoplasm. Proteins overexpressed in E. coii are often found in insoluble aggregates, so-called inclusion bodies. These inclusion bodies may be located in the cytosol or in the periplasm; the recovery of biologically active proteins from these inclusion bodies requires a denaturation/refoiding process. Many recombinant proteins, including therapeutic proteins, are recovered from inclusion bodies. Alternatively, as will be clear to the skilled person, recombinant strains of bacteria that have been genetically modified so as to secrete a desired protein, and in particular an amino acid sequence, Nanobody® or a polypeptide of the invention, can be used.

Thus, according to one non-limiting embodiment of the invention, the amino acid sequence, Nanobody® or polypeptide of the invention is an amino add sequence, Nanobody® or polypeptide that has been produced intraceliularly and that has been isolated from the host ceil, and in particular from a bacterial ceil or from an inclusion body in a bacterial celi. According to another non-limiting embodiment of the invention, the amino acid sequence, Nanobody® or polypeptide of the invention is an amino acid sequence, Nanobody® or polypeptide that has been produced extracellularly, and that has been isolated from the medium in which the host cell is cultivated.

Some preferred, but non-iimiting promoters for use with these host cells include. for expression in E. coli: lac promoter {and derivatives thereof such as the lacUV5 promoter); arabinose promoter; left- (PL) and rightward (PR) promoter of phage lambda; promoter of the trp operon; hybrid lac/trp promoters (tac and trc);T7-promoter (more specifically that of 17-phage gene 10) and other T-phage promoters; promoter of the TnlO tetracycline resistance gene; engineered variants of the above promoters that include one or more copies of an extraneous regulatory operator sequence; for expression in S. cerevisiae: constitutive: ADH1 (alcohol dehydrogenase 1), ENO (enolase), CYC1 (cytochrome c iso-1), GAPDH (glyceraldehydes-3-phosphate dehydrogenase), PGKl (phosphogiycerate kinase), PYK1 (pyruvate kinase); regulated; GAL1,1Q,7 (gaiactose metabolic enzymes), ADH2 (aicohoi dehydrogenase 2), PH05 (acid phosphatase), CUP1 (copper metaiiotnionain); heterologous: CaMV (cauliflower mosaic virus 35$ promoter); for expression in Pichia pastoris: the AOX1 promoter (aicohoi oxidase I); for expression in mammalian celts: human cytomegalovirus (hCMV) immediate early enhancer/promoter; human cytomegalovirus (hCMV) immediate early promoter variant that contains two tetracycline operator sequences such that the promoter can be regulated by the Tet repressor; Herpes Simplex Virus thymidine kinase (TK) promoter; Rous Sarcoma Virus long terminal repeat (RSVITR) enhancer/promoter; elongation factor la (hEF-la) promoter from human, chimpanzee, mouse or rat; the SV40 early promoter; HIV-1 long terminal repeat promoter; β-actin promoter;

Some preferred, but non-limiting vectors for use with these host cells include; vectors for expression in mammalian cells: pMAMneo (Ciontech), pcDNA3 (Invitrogen), pMClneo (Stratagene), pSGS (Stratagene), EBO-pSV2-neo (ATCC 37593), pBPV-1 (8-2) (ATCC 37110), pdBPV-MMTneo ¢342-12) (ATCC 37224), pRSVgpt (ATCC37199), pRSVnec (ATCC37198), pSV2-dhfr (ATCC 37146), pUCTag (ATCC 37460) and 1ZD35 (ATCC 37565), as well as viral-based expression systems, such as those based on adenovirus; vectors for expression in bacterial cells: pET vectors (Novagen) and pQE vectors (Qiagen); vectors for expression in yeast or other fungal cells: pYES2 (Invitrogen) and Pichia expression vectors (Invitrogen); vectors for expression in insect cells: pBlueBacll (Invitrogen) and other bacuiovirus vectors vectors for expression in plants or plant cells: for example vectors based on cauliflower mosaic virus or tobacco mosaic virus, suitable strains of Agrobacterium, or Ti-plasmid based vectors.

Some preferred, but non-limiting secretory sequences for use with these host cells include: for use in bacterial cells such as E. coli: PelB, Bia, OmpA, OmpC, OmpF, OmpT, Stli, PhoA, PhoE, MalE, Lpp, LamB, and the like; TAT signal peptide, hemolysin C-terminal secretion signal; for use in yeast: a-mating factor prepro-sequence, phosphatase (phol), irwertase (Sue), etc.; for use in mammalian ceils: indigenous signal in case the target protein is of eukaryotic origin; murine Ig κ-chain V-J2-C signal peptide; etc.

Suitable techniques for transforming a host or host ceil of the invention will be dear to the skilled person and may depend on the intended host cell/host organism and the genetic construct to be used. Reference is again made to the handbooks and patent applications mentioned above.

After transformation, a step for detecting and selecting those host cells or host organisms that have been successfully transformed with the nucleotide sequence/genetic construct of the invention may be performed. This may for instance be a selection step based on a selectable marker present in the genetic construct of the invention or a step involving the detection of the amino acid sequence of the invention, e.g, using specific antibodies,

The transformed host cell (which may be in the form or a stable cell line) or host organisms (which may be in the form of a stable mutant line or strain) form further aspects of the present invention.

Preferably, these host cells or host organisms are such that they express, or are (at least) capable of expressing (e.g. under suitable conditions), an amino acid sequence, Nanobody“ or poiypeptide of the invention (and in case of a host organism: in at least one cell, part, tissue or organ thereof). The invention also includes further generations, progeny and/or offspring of the host cell or host organism of the invention, that may for instance be obtained by cell division or by sexual or asexual reproduction.

To produce/obtain expression of the amino acid sequences, Nanobodies® or polypeptides of the invention, the transformed host cell or transformed host organism may generally be kept, maintained and/or cultured under conditions such that the (desired) amino acid sequence,

Nanobody® or polypeptide of the invention is expressed/produced. Suitable conditions will be dear to the skilled person and will usually depend upon the host cell/host organism used, as well as on the regulatory elements that control the expression of the (relevant) nucleotide sequence of the invention. Again, reference is made to the handbooks and patent applications mentioned above in the paragraphs on the genetic constructs of the invention.

Generally, suitable conditions may include the use of a suitable medium, the presence of a suitable source of food and/or suitable nutrients, the use of a suitable temperature, and optionally the presence of a suitable inducing factor or compound (e.g. when the nucleotide sequences of the invention are under the control of an inducible promoter); all of which may be selected by the skilled person. Again, under such conditions, the amino acid sequences of the invention may be expressed in a constitutive manner, in a transient manner, or only when suitably induced.

It will also be clear to the skilled person that the amino acid sequence, Nanobody® or poiypeptide of the invention may (first) be generated in an immature form (as mentioned above), which may then be subjected to post-transSationBl modification, depending on the host cell/host organism used. Also, the amino acid sequence, Nanobody® or poiypeptide of the invention may be glycosylated, again depending on the hostceil/host organism used.

The amino acid sequence, Nanobody®1 or poiypeptide of the invention may then be isolated from the host ceii/host organism and/or from the medium in which said host cell or host organism was cultivated, using protein isolation and/or purification techniques known per $e, such as (preparative) chromatography and/or electrophoresis techniques, differential precipitation techniques, affinity techniques (e.g. using a specific, cieavable amino acid sequence fused with the amino acid sequence, Nanobody® or polypeptide of the invention) and/or preparative immunological techniques (i.e. using antibodies against the amino acid sequence to be isolated).

The invention further relates to a product or composition containing or comprising at least one amino acid sequence of the invention (or a suitable fragment thereof), at least one Nanobody® of the invention, at least one poiypeptide of the invention, at least one compound or construct of the invention, at least one monovalent construct of the invention and/or at least one nucieic acid of the invention, and optionally one or more further components of such compositions known per se, i.e. depending on the intended use of the composition. Such a product or composition may for example be a pharmaceutical composition (as described herein], a veterinary composition or a product or composition for diagnostic use (as also described herein). Some preferred but non-limiting examples of such products or compositions will become dear from the further description herein.

Generally, for pharmaceutical use, the amino acid sequences. Nanobodies* and polypeptides of the invention may be formulated as a pharmaceutical preparation or compositions comprising at ieast one amino acid sequence, Nanobody®’ or polypeptide of the invention and at least one pharmaceutically acceptable carrier, diluent or excipient and/or adjuvant, and optionally one or more further pharmaceutically active polypeptides and/or compounds. By means of non-limiting examples, such a formulation may be in a form suitable for oral administration, for parenteral administration (such as by intravenous, intramuscular or subcutaneous injection or intravenous infusion), for topicai administration, for administration by inhalation, by a skin patch, by an implant, by a suppository, etc.. Such suitable administration forms - which may be solid, semi-solid or liquid, depending on the manner of administration - as well as methods and carriers for use in the preparation thereof, will be clear to the skilled person, and are further described herein.

Thus, in a further aspect, the invention relates to a pharmaceutical composition that contains at least one amino acid of the invention, at least one Nanobody®' of the invention, at least one compound or construct of the invention or at least one polypeptide of the invention and at ieast one suitable carrier, diluent or excipient (i.e. suitable for pharmaceutical use), and optionally one or more further active substances.

Generally, the amino acid sequences, Nanobodies*5, compounds, constructs and polypeptides of the invention can be formulated and administered in any suitable manner known per ss, for which reference is for example made to the general background art cited above {and in particular to WO 04/041862, WO 04/041863, WO 04/041865, WO 04/041867 and WO 08/020079) as well as to the standard handbooks, such as Remington's Pharmaceutical Sciences, I8,f! Ed., Mack Publishing Company, USA (1990), Remington, the Science and Practice of Pharmacy, 21st Edition, Uppincott Williams and Wilkins (2005); or the Handbook of Therapeutic Antibodies (S. Dubet, Ed.), Wiley, Weinheim, 2007 (see for example pages 252-255).

For example, the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention may be formulated and administered in any manner known per se for conventional antibodies and antibody fragments (including ScFv's and diabodies) and other pharmaceutically active proteins. Such formulations and methods for preparing the same will be dear to the skilled person, and for example include preparations suitable for parenteral administration (for example intravenous, intraperitoneal, subcutaneous, intramuscular, intraluminal, intra-arterial or intrathecal administration) or for topical (i.e. transdermal or intradermal) administration.

Preparations for parenteral administration may for example be sterile solutions, suspensions, dispersions or emulsions that are suitable for infusion or injection. Suitable carriers or diluents for such preparations for example include, without limitation, those mentioned on page 143 of W0 08/020079, Usually, aqueous solutions or suspensions will be preferred.

The amino acid sequences. Nanobodies®, compounds, constructs and polypeptides of the invention can also be administered using gene therapy methods of delivery. See, e.g., U.S. Patent No, 5,399,346, which is incorporated by reference in its entirety. Using a gene therapy method of delivery, primary cells transfected with the gene encoding an amino acid sequence, Nanobody® or polypeptide of the invention can additionally be transfected with tissue specific promoters to target specific organs, tissue, grafts, tumors, or cells and can additionally be transfected with signal and stabilization sequences for subcellulariy localized expression.

Thus, the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention may be systemicaliy administered, e,g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet, For oral therapeutic administration, the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention may be combined with one or more excipients and used in the form of ingestibie tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of the amino acid sequence, Nanobody®, compound, construct or polypeptide of the invention. Their percentage in the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of a given unit dosage form. The amount of the amino acid sequence, Nanobody®, compound, construct or polypeptide of the invention in such therapeutically useful compositions is such that an effective dosage level will be obtained.

The tablets, troches, pills, capsules, and the like may also contain binders, excipients, disintegrating agents, lubricants and sweetening or flavouring agents, for example those mentioned on pages 143-144 of WO 08/020079. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical fonri of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention may be incorporated into sustained-release preparations and devices.

Preparations and formulations for oral administration may also be provided with an enteric coating that will allow the constructs of the invention to resist the gastric environment and pass into the intestines. More generally, preparations and formulations for oral administration may be suitably formulated for delivery into any desired part of the gastrointestinal tract. In addition, suitable suppositories may be used for delivery into the gastrointestinal tract.

The amino acid sequences. Nanobodies®, compounds, constructs and polypeptides of the invention may also be administered intravenously or intraperitoneally by infusion or injection, as further described on pages 144 and 145 of WO 08/020079.

For topical administration, the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention may be applied in pure form, i.e., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid, as further described on page 145 of WO 08/020079.

Generally, the concentration of the amino acid sequences, Nanobodies®, compounds, constructs and polypeptides of the invention in a liquid composition, such as a lotion, will be from about 0.1-25 wt-%, preferably from about 0.5-10 wt-%. The concentration in a semi-solid or solid composition such as a gel or a powder will be about 0.1-5 wt-%, preferably about 0.5-2.5 wt-%.

In a preferred aspect, the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention and/or compositions comprising the same are administered to the pulmonary tissue. In the context of the present invention, "pulmonary tissue" is for the purposes of this invention equivalent with lung tissue or lung. The lung comprises 2 distinct zones: a conducting and a respiratory zone, within which the airway and vascular compartments lie (see e.g. "Pulmonary Drug Delivery", Edited by Karoiine Bechtold-Peters and Henrik Luessen, 2007, ISBN 978-3-87193-322-6 pages 16-28).

For pulmonary delivery, the amino acid sequences, Nanobodies*', compounds, constructs and polypeptides of the invention may be applied in pure form, i.e., when they are liquids or a dry powder. However, it will be preferred to administer them to the pulmonary tissue as composition or formulation comprising an amino acid sequence, Nanohody®, compound, construct and/or polypeptide of the invention and a carrier suitable for pulmonary delivery. Accordingly the present invention also relates to a pharmaceutical composition comprising the amino acid sequence. Nanobody®, compound, construct and/or polypeptide of the invention and a carrier suitable for pulmonary delivery. Carriers suitable for pulmonary delivery' are known in the art.

The amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention may also be administered as micro- or nanoparticles of pure drugs with particle sizes and distributions favorable for pulmonary delivery.

Accordingly the present invention also relaxes to a pharmaceutical device suitable for the pulmonary delivery of the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention and suitable in the use of a composition comprising the same. This device may be an inhaler for liquids (e.g. a suspension of fine solid particles or droplets) comprising the amino acid sequence, Nanobody*, compound, constructs and/or poiypeptide of the invention. Preferably this device is an aerosol comprising the amino acid sequence, Nanobody®, compound, construct and/or polypeptide of the invention, The device may also be a dry powder inhaler comprising the amino acid sequence, Nanobody®, compound, construct and/or poiypeptide of the invention in the form of a dry powder. in a preferred method, the administration to the pulmonary tissue is performed by inhaling the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention and/or the composition comprising the same in an aerosol cloud. According to the invention, inhaling of the aerosol cioud can be performed by an inhaler device. The device should generate from a formulation comprising the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention (and/or composition comprisingthe same) an aerosol cloud of the desired particle size (distribution) at the appropriate moment of the mammal's inhalation cycle, containing the right dose of the amino acid sequences, Nanobodiesw, compounds, constructs and/or polypeptides of the invention ("Pulmonary drug delivery", Bechtold-Peters and Luessen, eds., ISBN 978-3-871S3-322-6, page 125).

In the context of the present invention, "aerosol“ denotes a suspension of fine solid particles or liquid droplets (or combination thereof) in a gas wherein for the purposes of this invention the particles and/or droplets comprise the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention.

The device should generate from the formulation an aerosol cloud of the desired particle size (distribution) at the appropriate moment of the mammal's inhalation cycle, containing the right dose of amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention. The following 4 requirements (formulation, particle size, time and dose) should be considered ("Pulmonary Drug Delivery", Bechtold-Peters and Luessen, eds., supra, pages 125 and 125):

The formulations that are used in the devices may vary from aqueous solutions or suspensions used in nebulizers to the propellant-based solutions or suspensions used in metered dose inhaler or even specially engineered powder mixtures for the dry' powder inhalers. At! these different formulations require different principles for aerosol generation, which emphasizes the mutual dependency of device and formulation;

Since the site of deposition of aerosol particles depends on their (aerodynamic) size and velocity, the desired particle size of the aerosol cloud varies depending on the desired site of deposition in the lung, which is related to the therapeutic goal of the administration;

As the aerosol cloud can be tuned to be released at different moments during the inhalation cycle generated by the mamma!, it is preferred that for the agents of the invention (to be deposited in the peripheral parts of the iung) the aerosol is released at the start of the inhalation cycle;

Doses may vary considerably and may e.g. vary e.g. for a human from a few microgram to several hundreds of microgram or even milligrams, e.g. about up to about 10 to 100 milligrams.

Various inhalation systems are e.g. described on pages 12S to 148 in the review ("Pulmonary Drug Delivery", Bechtold-Peters and Luessen, eds., supra) and include, but are not limited to, nebulizers, metered dose inhalers, metered dose iiquid inhalers, and dry powder inhalers. Devices taking into account optimized and individualized breathing pattern for controlled inhalation manoeuvres may also be used (see AKITA® technology on page 157 of "Pulmonary Drug Delivery'", Bechtold-Peters and Luessen, eds., supra).

However, not only the device is important to pulmonary delivery of the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention but also the right formulation is critical to achieve an effective deiivery. This can be in principle achieved by using one of the following approaches:

Administration of aqueous solutions or suspensions comprising the amino acid sequences, Nanobodies1', compounds, constructs and/or polypeptides of the invention (e.g. nasal drops) into the nasal cavities;

Nebuiisatron of aqueous solutions or suspensions comprising the amino acid sequences, Nanobodies®, comnounds, constructs and/or polypeptides of the invention;

Atomization by means of iiquefied propellants; and Dispersion of dry powders.

Hence formulations of the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention have to be adopted and adjusted to the chosen inhalation device. Appropriate formulations, i.e. the excipients in addition to the amino acid sequences, Nanobodies®, compounds, constructs and/or polypeptides of the invention, are e.g. described in chapter IV of "Pulmonary Drug Delivery", Bechtoid-Peters and Luessen, eds., supra, tn this respect, reference is also made to US provisional application No. US 61/303,447 entitled "Methods and compositions for the preparation of aerosols" filed by Ablynx N.V. on 12 February 2010.

The amount of the amino acid sequences. Nanobodies®, compounds, constructs and polypeptides of the invention required for use in treatment will vary not only with the particular amino acid sequence. Nanobody®, compounds, constructs or poiypeptide selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or clinician. Also the dosage of the amino acid sequences. Nanobodies®, compounds, constructs and polypeptides of the invention varies depending on the target host ceil, tumor, tissue, graft, or organ.

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.q„ into a number of discrete loosely spaced administrations; such as multiple inhalations from an insufflator or by application of a plurality of drops into the eye.

An administration regimen could include long-term, daily treatment. By "long-term" is meant at least two weeks and preferably, several weeks, months, or years of duration. Necessary modifications in this dosage range may be determined by one of ordinary skill in the art using only routine experimentation given the teachings herein. See Remington's Pharmaceutical Sciences {Martin, E.W., ed. 4), Mack Publishing Co., Easton, PA. The dosage can also be adjusted by the individual physician in the event of any complication.

The invention further relates to applications and uses of the amino acid sequences, Nanobodies®, polypeptides, compounds, nucleic acids, host cells, products and compositions described herein, as well as to methods for the prevention and/or treatment respiratory track infection caused by hRSV. Some preferred but non-limiting applications and uses will become clear from the further description herein.

The amino acid sequences, Nanobodies®, polypeptides, compounds and compositions of the present invention can generally be used to block the interaction of protein F of hRSV with the target host ceil and/or its membrane, to neutralize hRSV (different hRSV strains and/or escape mutants), to modulate, inhibit and/or prevent hRSV infectiviry (of different hRSV strains and/or escape mutants}, to modulate, inhibit and/or prevent fusion (of different hRSV strains and/or escape mutants) with (the cell membrane of) the target host cell and/or to modulate, inhibit and/or prevent hRSV entry in the target host cell (of different hRSV strains and/or escape mutants).

In one aspect, the amino acid sequences, Nanobodies®, polypeptides, compounds and compositions of the present invention can block the interaction of protein F of hRSV with the target host ceil and/or its membrane by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to the interaction of protein f of hRSV with the target host cell and/or its membrane under the same conditions but without the presence of the amino acid sequence, Nanobody® or polypeptide of the invention, measured in any suitable manner known per se, for example using one of the assays described herein.

In another aspect, the amino acid sequences, Nanobodies5', polypeptides, compounds and compositions of the present invention neutralize hRSV infectivity by at least 1%, preferably at least 5%, such as at least 10% or at ieast 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to, the neutralization of hRSV under the same conditions but without the presence of the amino acid sequence, Nanobody® or polypeptide of the invention, measured in any suitable manner known per se, for example using one of the assays described herein,

In the context of the present invention, "modulating" or "to modulate" generally means either reducing, preventing or inhibiting viral infectivity, fusion and/or viral entry and/or reducing, preventing or inhibiting the biological pathways that are mediated by protein F of hRSV, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, "modulating" or "to modulate" may mean either reducing, preventing or inhibiting viral infectivity, fusion and/or viral entry and/or reducing, preventing or inhibiting the biological pathways that are mediated by protein F of hRSV as measured using a suitable in vitro, cellular or in vivo assay {such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral infectivity, fusion and/or viral entry and/or normal (i.e. naturally occurring) the biological pathways that are mediated by protein F of hRSV in the same assay under the same conditions but without the presence of the amino acid sequence, Nanobody® or polypeptide of the invention. in one aspect, the amino acid sequences, Nanobodies®, polypeptides, compounds and compositions of the present invention may modulate, inhibit and/or prevent hRSV infectivity by at least 1%, preferably at ieast 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to the infectivity under the same conditions but without the presence of the amino acid sequence, Nanobody8 or polypeptide of the invention, measured in any suitable manner known per se, for example using one of the assays described herein.

The term "viral entry" used herein encompasses any viral-mediated biological pathway that is needed to accomplish virion attachment to a target host cel! and/or vira! fusion with a target nost ceil. It is encompassed in the present invention that viral entry, which may be any viral-mediated biological pathway that is needed to accomplish virion attachment to a target host cell and/or viral fusion with a target host cell, can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, Nanobodies®, polypeptides and/or compounds of the invention, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), in particular, viral entry, which can be mediated by protein F of hRSV, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences, Nanobodies®, polypeptides and/or compounds of the invention to protein F of hRSV, as measured using a suitable in vitro, cellular or in vivo assay {such as those mentioned herein), by at ieast 1%, preferably at least 5%, such as at least 10% or at ieast 25%, for example by at least 50%, at ieast 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral entry (as defined herein), which can be mediated by protein F of hRSV, in the same assay under the same conditions but without the presence of the amino acid sequence. Nanobody®, polypeptide and/or compound of the invention. Thus, it is also encompassed that that viral attachment and/or viral fusion can be modulated and/or reduced and/or prevented and/or inhibited by specific binding of the amino acid sequences, Nanobodies®, polypeptides and/or compounds of the invention to protein F of hRSV, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein). In particular, viral attachment and/or viral fusion, which can be mediated by protein F of hRSV, can be modulated, reduced, prevented or inhibited by specific binding of the amino acid sequences,

Nanobodies'5', polypeptides and/or compounds of the invention to protein F of hRSV, as measured using a suitable in vitro, cellular or in vivo assay (such as those mentioned herein), by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to normal (i.e. naturally occurring) viral attachment and/or viral fusion, which can be mediated by protein F of hRSV in the same assay under the same conditions but without the presence of the amino acid sequence, Nanobody®, polypeptide and/or compound of the invention.

In this respect, the amino acid sequences. Nanobodies®, polypeptides, compounds and compositions of the present invention may modulate, inhibit and/or prevent hRSV entry in the target host cell by at ieast 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at least 50%, at least 60%, at least 70%, at least 80%, or 90% or more, compared to the entry in the target host cell under the same conditions but without the presence of the amino acid sequence, Nanobody* or polypeptide of the invention, for example using one of the assays described herein.

The amino add sequences, Nanobodies®, polypeptides, compounds and compositions of the present invention may also modulate, inhibit and/or prevent fusion of hRSV with (the ceil membrane of) the target host cell by at least 1%, preferably at least 5%, such as at least 10% or at least 25%, for example by at ieast 50%, at ieast 60%, at least 70%, at least 80%, or 90% or more, compared to fusion of hRSV with (the cell membrane of) the target host cell under the same conditions but without the presence of the amino acid sequence, Nanobody® or polypeptide of the invention, measured in any suitable manner known per se, for example using one of the assays described herein.

The multivalent (such as bivalent ortrivalent) polypeptides of the invention have shown improved affinity and/or improved cross-reactivity for different genotypes, subtypes, viral escape mutants and/or strains of hRSV compared to the monovalent amino acid sequence or Nanobody®, in one aspect, the multivalent (such as bivalent or trivaient) polypeptides of the invention may bind different strains of RSV (such as e.g. Long, A-2 and/or B-l). In yet another aspect, the multivalent (such as bivalent or trivaient) polypeptides of the invention may bind different escape mutants of hRSV (such as e.g. described in Lopes et al. 1998, J. Virol, 72: 6922-6928) and/or escape mutants specific for antigen site 11, antigen site IV-VI or the combination of both antigenic sites.

Accordingly, the invention also relates to the use of a multivalent (e.g. trivaient, bivalent) polypeptide of the invention, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization of different strains of a hRSV, In a preferred aspect, a bivalent humanized and/or sequence optimized NC41 Nanobody® (such as e.g. a bivalent polypeptide comprising two Nanobodies® selected from SEQ. ID NO's: 60-76,138-141 and 146-157) is used, in another preferred aspect, a trivaient humanized and/or sequence optimized NC41 Nanobody£ (such as e.g. a trivaient polypeptide comprising three Nanobodies® selected from SEQ ID NO's: 60-76,138-141 and 146-157) Is used. In another preferred aspect, one of SEQ 10 NO's: 77-79,142-145 and 158-165 is used.

The invention also relates to the use of a multivalent (e.g. trivalent, bivalent) polypeptide of the invention, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization of one or more escape mutants of a hRSV. In a preferred aspect, a bivalent humanized NC41 Nanobody® (such as e.g. a bivalent polypeptide comprising two Nanobodies* selected from SEQ ID NO's: 60-76,138-141 and 146-157) is used, in another preferred aspect, a trivalent humanized NC41 Nanobody® (such as e.g. a trivalent polypeptide comprising three Nanobodies® selected from SEQ ID NO's: 50-76,138-141 and 146-157) is used. In another preferred aspect, one of SEQ ID NO's: 77-79,142-145 and 158-165 is used.

The invention also relates to a method for the prevention and/or treatment of at least one viral disease, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of an amino acid sequence of the invention, of a Nanobody^’ of the invention, of a polypeptide of the invention, of a compound or construct of the invention and/or of a pharmaceutical composition comprising the same.

As such, the amino acid sequences, Nanobodies®, polypeptides, compounds and compositions of the present invention can be used for the prevention and/or treatment of diseases and disorders associated with hRSV infection. Examples of such diseases and disorders associated with hRSV infection will be clear to the skilled person based on the disclosure herein, and for example include the following diseases and disorders: respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma.

Accordingly, the present invention aiso relates to a method for the prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma caused by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino acid sequence of the invention, Nanobody® of the invention, polypeptide of the invention, compound or construct of the invention or monovalent construct of the invention, or a composition of the invention.

The invention also relates to the use of an amino acid sequence of the invention, a Nanobody® of the invention, a polypeptide of the invention, a compound or construct of the invention or monovalent construct of the invention in the preparation of a pharmaceutical composition for prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the smalt airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma; and/or for use in one or more of the methods described herein.

The invention also relates to an amino acid sequence of the invention, a Nanobody® of the invention, a polypeptide of the invention, a compound or construct of the invention or monovalent construct of the invention for prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the smell airways in the iungj, pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma.

In the context of the present invention, the term "prevention and/or treatment" not only comprises preventing and/or treating the disease, but also generally comprises preventing the onset of the disease, slowing or reversing the progress of disease, preventing or slowing the onset of one or more symptoms associated with the disease, reducing and/or alleviating one or more symptoms associated with the disease, reducing the severity and/or the duration of the disease and/or of any symptoms associated therewith and/or preventing a further increase in the severity of the disease and/or of any symptoms associated therewith, preventing, reducing or reversing any physiological damage caused by the disease, and generally any pharmacoiogicai action that is beneficial to the patient being treated.

The subject to be treated may be any warm-blooded animal, but is in particular a mamma!, and more in particular a human being. As will be dear to the skilled person, the subject to be treated will in particular be a person suffering from, or at risk of, the diseases and disorders mentioned herein.

More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by HRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a multivalent (e.g. trivalent or bivalent) polypeptide or compound of the invention, and/or of a pharmaceutical composition comprising the same. More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a bivalent compound or polypeptide of the invention. More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a bivalent humanized and/or sequence optimized NC41 Nanobody* (such as e.g. a bivalent polypeptide comprising two Nanobodies® selected from SEQ ID NO's: 60-76,138-141 and 146-157). More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a trivalent compound or polypeptide of the invention. More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a trivaient humanized NC41 Nanobody® (such as e.g. a trivalenf polypeptide comprising three Nanobodies® selected from SEO. ID NO's: 60-75,138-141 and 146-157). More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of one of SEQ. ID NO's: 77-79,142-145 and 158-155.

More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV said method comprising administering to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of an amino acid sequence of the invention, of a Nanobody® of the invention, of a polypeptide of the invention, and/or of a pharmaceutical composition comprising the same.

In another aspect, the invention relates to a method for immunotherapy, and in particular for passive immunotherapy, which method comprises administering, to a subject suffering from or at risk of the diseases and disorders mentioned herein, a pharmaceutically active amount of an amino add sequence of the invention, of a Nanobody® of the invention, of a polypeptide of the invention, of a compound or construct of the invention and/or of a pharmaceutical composition comprising the same.

In the above methods, the amino acid sequences, Nanobodies®, compounds or constructs and/or polypeptides of the invention and/or the compositions comprising the same can be administered in any suitable manner, depending on the specific pharmaceutical formulation or composition to be used. Thus, the amino acid sequences, Nanobodres® and/or polypeptides of the invention and/or the compositions comprising the same can for example be administered oraliy, intraperitoneally (e.g. intravenously, subcutaneously, intramuscularly, or via any other route of administration that circumvents the gastrointestinal tract), intranasaliy, transdermaliy, topically, by means of a suppository, by inhalation, again depending on the specific pharmaceutical formulation or composition to be used. The clinician will be able to select a suitable route of administration and a suitable pharmaceutical formulation or composition to be used in such administration, depending on the disease or disorder to be prevented or treated and other factors well known to the clinician.

Thus, in general, the amino add sequences, Nanobodies®, compounds or constructs and polypeptides according to the invention and/or the compositions comprising the same can be administered in any suitable manner; for example but not limited thereto, the amino add sequences. Nanobodies'®, compounds or constructs and polypeptides according to the invention and compositions comprising the same can be administered intranasaliy and/or by inhalation and/or by any other suitable form of pulmonary delivery; methods for pulmonary delivery and/or intranasal delivery and/or delivery by inhalation of a Nanobody®, amino acid sequence, compound or construct and/or polypeptide of the invention will be known to the skilled person and are e.g. described in the handbook "Drug Delivery: Principles and Applications" (2005) by Binghe Wang,Teruna Siahaan and Richard Soltero (Eds. Wiley interscience (John Wiley & Sorts)); in the International application WO 08/049B97 of Ablynx N.V. entitled "Intranasal delivery of polypeptides and proteins"; in "Pharmacology PreTest1M Self-Assessment and Review" (11th Edition) by Rosenfeld G.C., Loose-Mitchell D.S.; and in "Pharmacology" (3rd Edition) by Uppincott Williams & Wilkins, New York; Shlafer M. McGraw-Hill Medical Publishing Division, New York; Yang K.Y., Graff L.R., Caughey A.B. Blueprints Pharmacology, Blackwell Publishing.

Accordingly, the present invention also relates to a method for administering an effective amount of a amino acid sequence, Nanobody®, compound or construct and/or polypeptide of the invention and/or a composition comprising the same, wherein said method comprises the step of administering the amino acid sequence, Nanobody®, compound or construct and/or polypeptide and/or composition comprising the same to the pulmonary' tissue. In such method, the amino acid sequence, Nanobody®, compound or construct and/or polypeptide and/or a composition comprising the same can be administered by any method know in the art for pulmonary delivery' such as e.g. by use of an inhaler or intranasal delivery device or aerosol. in a preferred aspect of the invention, the amino add sequence, Nanobody®, compound or construct and/or polypeptide will bind and/or neutralize virus present in the pulmonary tissue. Preferably in such method for pulmonary delivery.· at least 5%, preferably at ieast 10%, 20%, 30%, 40%, more preferably at least 50%, 60%, 70%, and even more preferably at least 80% or more of the amino add sequence, Nanobodv®, compound or construct and/or polypeptide of the invention is stable in the pulmonary' tissue for at least 24 hours, preferably at least 48 hours more preferably at least 72 hours.

It has been surprisingly found that the amino acid sequences, Nanobodies®', compounds or constructs and/or polypeptides of the invention have a long lasting stability in the pulmonary tissue. E.g. it has been found that a Nanobody* directed against hRSV remains functional in the lung for at least 48 hours (see PCT/EP2009/056975 entitled Amino acid sequences directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases filed by Ablynx N.V. on 5 June 2009). Thus, embodiments of the invention with treatment intervals such as once a day, once every 2nd, 3rd, 4"', 5th, 6th or once every week are thought to be possible taken the estimated long lasting stability of the amino acid sequences, Nanobodies®, compounds or constructs and/or polypeptides of the invention.

Accordingly, the invention relates to a method for delivering an amino acid sequence, Nanobody®-', compound or construct and/or polypeptide of the invention to the pulmonary tissue of a subject without being inactivated, said method comprising the step of pulmonary administering said amino acid sequence, Nanobody®, compound or construct and/or polypeptide of the invention to said subject.

The invention also relates to a method for the prevention and/or treatment of hRSV infection, said method comprising administering to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of an amino acid sequence of the invention, of a Nanobody8 of the invention, of a polypeptide of the invention, of a compound or construct of the invention and/or of a pharmaceutical composition comprising the same.

More in particular, the invention relates to a method for the prevention and/or treatment of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the iungj, pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of an amino acid sequence of the invention, of a Nanobody® of the invention, of a polypeptide of the invention, of a compound or construct of the invention and/or of a pharmaceutical composition comprising the same.

More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of a multivalent (e.g. trivalent, bivalent) polypeptide or compound of the invention, and/or of a pharmaceutical composition comprising the same. More in particular, the present invention may relate to a method for the prevention and/or treatment of Infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of a bivalent compound or polypeptide of the invention. More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of a bivalent humanized NC41 Nanobody® (such as e.g. a bivalent polypeptide comprising two Nanobodies® selected from SEG10 NO's: 60-76,138-141 and 146-157). More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of a irivaient compound or polypeptide of the Invention. More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of a trivalent humanized NC41 Nanobody® (such as e.g. a trivalent polypeptide comprising three Nanobodies® selected from SEG ID NO's: 60-76,138-141 and 146-157). More in particular, the present invention may relate to a method for the prevention and/or treatment of infection by hRSV, said method comprising administering, to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of one ofSEQ ID NO's: 77-79,142-145 and 158-165.

Also for example but not limited thereto, the amino acid sequences, Nanobodies®', compounds or constructs, and polypeptides according to the invention and compositions comprising the same, can be administered intramuscularly and/or by any suitable form of delivery to the brain, such as any suitable form of delivery which allows said amino acid sequences, Nanobodies®, polypeptides, compounds or constructs and compositions comprising the same to be transported across the blood-brain-barrier. Such methods for intramuscular delivery and/or any suitable form of delivery to the brain of a Nanobody®, amino acid sequence and/or polypeptide of the invention will be known to the skilled person and are e.g. described in the handbook "Drug Delivery': Principles and Applications" (2005) by Binghe Wang, Teruna Siahaan and Richard Soltero (Eds. Wiiey Interscience (John Wiley & Sons)); in "Pharmacology PreTest™ Self-Assessment and Review" (ll111 Edition) by Rosenfeld G.C., Loose-Mitchell D.S.; and in "Pharmacology" (3ro Edition) by Lippincott Williams & Wilkins, New York; Shlafer M. McGraw-Hill Medicat Publishing Division, New York; Yang K.Y., Graff L.R., Caughey A.B. Blueprints Pharmacology, Blackwell Publishing.

The amino acid sequences, Nanobodies®, compounds or constructs and/or polypeptides of the invention and/or the compositions comprising the same are administered according to a regime of treatment that is suitable for preventing and/or treating the disease or disorder to be prevented or treated. The clinician will generally be able to determine a suitable treatment regimen, depending on factors such as the disease or disorder to be prevented or treated, the severity' of the disease to be treated and/or the severity of the symptoms thereof, the specific amino acid sequence, Nanobody®, compound or construct or polypeptide of the invention to be used, the specific route of administration and pharmaceutical formulation or composition to be used, the age, gender, weight, diet, general condition of the patient, and similar factors well known to the clinician.

Generally, the treatment regimen will comprise the administration of one or more amino acid sequences, Nanobodies®, compounds or constructs and/or polypeptides of the invention, or of one or more compositions comprising the same, in one or more pharmaceutically effective amounts or doses. The specific amount(s) or doses to administered can be determined by the clinician, again based on the factors cited above.

Generally, for the prevention and/or treatment of the diseases and disorders mentioned herein and depending on the specific disease or disorder to be treated, the patency of the specific amino acid sequence, Nanobody®, compound or construct and polypeptide of the invention to be used, the specific route of administration and the specific pharmaceutical formulation or composition used, the amino acid sequences, Nanobodies®, compounds or constructs and polypeptides of the invention will generally be administered in an amount between 1 gram and 1 microgram per kg body weight per day, preferably between 0.1 gram and 10 microgram per kg body weight per day, most preferably between 0.01 gram and 100 microgram per kg body weight per day such as about 0.1, 0.5, 1, 2, 5 or 10 milligram per kg body weight per day, either continuously (e,g. by infusion), as a single daily dose or as multiple divided doses during the day. Amino add sequences. Nanobodies4', compounds or constructs and polypeptides of the invention that contain a half-life extending moiety may be administered in an amount between 1 milligram and 100 milligram per kg body weight, preferably between 1 milligram and 50 milligram per kg body weight, such as about 10,15,20 or 30 milligram per kg body weight once or twice a month. The clinician will generally be able to determine a suitable daily dose, depending on the factors mentioned herein. It will also be dear that in specific cases, the clinician may choose to deviate from these amounts, for example on the basis of the factors cited above and his expert judgment. Generally, some guidance on the amounts to be administered can be obtained from the amounts usually administered for comparable conventional antibodies or antibody fragments against the same target administered via essentially the same route, taking into account however differences in affinity/avidity, efficacy, biodistribution, half-life and similar factors well known to the skilled person.

When the ammo acid sequence, Nanobody®, compound or construct and/or polypeptide and/or a composition comprising the same is administered to the pulmonary tissue the treatment regime may be once or twice daily, preferably once daiiy, or once every 2, 3, 4, 5, 5, or 7 days.

Usually, in the above method, a single amino acid sequence, Nanobody®, compound or construct, or polypeptide of the invention will be used, it is however within the scope of the invention to use two or more amino acid sequences, Nanobodies®, compounds or constructs and/or polypeptides of the invention in combination.

The Nanobodies®, amino acid sequences, compounds or constructs and polypeptides of the invention may also be used in combination with one or more further pharmaceutically active compounds or principles, i.e. as a combined treatment regimen, which may or may not lead to a synergistic effect. Again, the clinician will be able to select such further compounds or principles, as well as a suitable combined treatment regimen, based on the factors cited above and his expert judgement.

In particular, the amino acid sequences, Nanobodies*5, compounds or constructs, and polypeptides of the invention may be used in combination with other pharmaceutically active compounds or principles that are or can be used for the prevention and/or treatment of the diseases and disorders cited herein, as a result of which a synergistic effect may or may not be obtained, Examples of such compounds and principles, as well as routes, methods and pharmaceutical formulations or compositions for administering them will be clear to the clinician.

When two or more substances or principles are to be used as part of a combined treatment regimen, they can be administered via the same route of administration or via different routes of administration, at essentially the same time or at different times (e.g. essentially simultaneously, consecutively, or according to an alternating regime). When the substances or principles are to be administered simultaneously via the same route of administration, they may be administered as different pharmaceutical formulations or compositions or part of a combined pharmaceutical formulation or composition, as will be clear to the skilled person.

Also, when two or more active substances or principles are to be used as part of a combined treatment regimen, each of the substances or principles may be administered in the same amount and according to the same regimen as used when the compound or principle is used on its own, and such combined use may or may not lead to a synergistic effect. However, when the combined use of the two or more active substances or principles leads to a synergistic effect, it may also be possible to reduce the amount of one, more or all of the substances or principles to be administered, while still achieving the desired therapeutic action. This may for example be useful for avoiding, limiting or reducing any unwanted side-effects that are associated with the use of one or more of the substances or principles when they are used in their usual amounts, while still obtaining the desired pharmaceutical or therapeutic effect.

The effectiveness of the treatment regimen used according to the invention may be determined and/or followed in any manner known per se for the disease or disorder involved, as will be dear to the clinician. The clinician will also be able, where appropriate and on a case-by-cass basis, to change or modify a particular treatment regimen, so as to achieve the desired therapeutic effect, to avoid, limit or reduce unwanted side-effects, and/or to achieve an appropriate balance between achieving the desired therapeutic effect on the one hand and avoiding, limiting or reducing undesired side effects on the other hand.

Generally, the treatment regimen will be followed until the desired therapeutic effect is achieved and/or for as long as the desired therapeutic effect is to be maintained. Again, this can be determined by the ciinician.

In another aspect, the invention relates to the use of an amino acid sequence, Nanobody®, compound or construct, or polypeptide of the invention in the preparation of a pharmaceutical composition for prevention and/or treatment of at least one viral disease; and/or for use in one or more of the methods of treatment mentioned herein.

The subject to be treated may be any warm-blooded animal, but is in particular a mammal, and more in particular a human being. As will be clear to the skilled person, the subject to be treated will in particular be a person suffering from, or at risk of, the diseases and disorders mentioned herein.

The invention also relates to the use of an amino acid sequence. Nanobody®, compound or construct or polypeptide of the invention in the preparation of a pharmaceutical composition for the prevention and/or treatment of at least one disease or disorder that can be prevented and/or treated by administering an amino acid sequence. Nanobody®, compound or construct or polypeptide of the invention to a patient.

More in particular, the invention relates to the use of an amino acid sequence, Nanobody®, compound or construct or polypeptide of the invention in the preparation of a pharmaceutical composition for the prevention and/or treatment of viral diseases, and in particular for the prevention and treatment of one or more of the diseases and disorders listed herein.

Again, in such a pharmaceutical composition, the one or more amino acid sequences, Nanobodies®, compounds or constructs or polypeptides of the invention may also be suitably combined with one or more other active principles, such as those mentioned herein.

Further uses of the amino acid sequences, Nanobodies®, polypeptides, nucleic acids, genetic constructs and hosts and host ceils of the invention will be dear to the skilled person based on the disclosure herein. For example, and without limitation, the amino acid sequences of the invention can be linked to a suitable carrier or solid support so as to provide a medium than can be used in a manner known per se to purify an envelope protein of a virus from compositions and preparations comprising the same. Derivatives of the amino acid sequences of the invention that comprise a suitable detectable label can also be used as markers to determine (qualitatively or quantitatively) the presence of an envelope protein of a virus in a composition or preparation or as a marker to selectively detect the presence of an envelope protein of a virus on the surface of a cel! or tissue (for example, in combination with suitable cell sorting techniques).

The invention will now be further described by means of the following non-limiting preferred aspects, examples and figures:

The entire contents of all of the references (including literature references, issued patents, published patent applications, and co-pena'ing patent applications) cited throughout this application are hereby expressly incorporated by reference, in particular for the teaching that is referenced hereinabove.

ASPECTS

Aspect A-l. Amine add sequence that is directed against and/or specifically binds protein F of hRSV and that comprises at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i} said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering}; and is) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect A-2. Amino acid sequence according to aspect A-l, that comprises two or more stretches of amino acid residues in which one stretch is chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino 3Cid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one stretch is chosen from: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid t residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a) and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Aspect A-3. Amino acid sequence according to aspect A-l or A-2, that comprises three or more stretches of amino acid residues, in which the first stretch of amino acid residues is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3.2 or 1 amino acid difference; the second stretch of amino acid residues is chosen from the group consisting of: c) 5EQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and iij the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and the third stretch of amino acid residues is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3.2 or 1 amino acid difference.

Aspect A-4. Amino add sequence according to any of aspects A-l to A-3, that specifically binds antigenic site li on protein F of hRSV and/or that competes with Synagis® for binding protein F of hRSV.

Aspect A-5. Amino acid sequence according to any of aspects A-l to A-4, that is a naturally occurring amino acid sequence (from any suitable species) or a synthetic or semisynthetic amino add sequence.

Aspect A-5. Amino acid sequence according to any of aspects A-lto A-5, that comprises an immunoglobulin fold or that under suitable conditions is capable of forming an immunoglobulin fold.

Aspect A-7. Amino acid sequence according to any of aspects A-l to A-6, that is an immunoglobulin sequence.

Aspect A-S. Amino acid sequence according to any of aspects A-i to A-7, that is a naturally occurring immunoglobulin sequence (from any suitable species) or a synthetic or semi-synthetic immunoglobulin sequence.

Aspect A-9. Amino acid sequence according to any of aspects A-l to A-8, that is a humanized immunoglobulin sequence, a camelized immunoglobulin sequence or an immunoglobulin sequence that has been obtained by techniques such as affinity maturation.

Aspect A-10. Amino acid sequence according to any of aspects A-l to A-9, that essentially consists of a heavy chain variable domain sequence (e.g. a VH-sequence).

Aspect A-li. Amino acid sequence according to any of aspects A-l to A-10, that essentially consists of a heavy chain variable domain sequence that is derived from a conventional four-chain antibody or that essentially consist of a heavy chain variable domain sequence that is derived from heavy chain antibody.

Aspect A-12. Amino acid sequence according to any of aspects A-l to A-ll, that essentially consists of a domain antibody {or an amino acid sequence that is suitable for use as a domain antibody), of a single domain antibody (or an amino acid sequence that is suitable for use as a singie domain antibody), of a "dAb" (or an amino acid sequence that is suitable for use as a dAb) or of a Nanobody® (including but not limited to a VH(,· sequence).

Aspect A-13. Amino acid sequence according to any of aspects A-l to A-12, that essentially consist of 4 framework regions (FRl to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from: a} SEa ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ (D NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect A-14. Amino acid sequence according to aspect A-13, that essentially consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity' determining regions (CDR1 to CDR3, respectively), in which CDR2 is chosen from the group consisting of: a) SEQ ID NO: 102; or b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and Π) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and at least one of CDR1 or CDR3 is chosen from: CDR1 chosen from the group consisting of: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ !D NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein r of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and/or CDR3 chosen from the group consisting of: e) SEQ ID NO; 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference.

Aspect A-15. Amino acid sequence according to any of aspects A-13 or A-14, that consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: CDR1 is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO; 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and CDR2 is chosen from the group consisting of: c| SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEO. ID NO: 102, provided that: i) said stretch of amino add residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kab3t numbering); and iil the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3. preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect A-16. Amino acid sequence according to any of aspects A-l to A-15, that comprises at least SEQ ID NO: 102.

Aspect A-17. Amino acid sequence according to aspect A-16, that comprises at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from: 3} SEQ tD NO: 98: b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with. SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino 3Cid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect A-18. Amino acid sequence according to any of aspects A-1S or A-17, that comprises at least SEQ ID NO: 102 and a CDR1 sequence chosen from: a) SEQ ID NO: 98; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or I amino acid difference; and a CDR3 sequence chosen from: c) SEQ ID NO: 121; and d} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID MO; 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect A-19. Amino acid sequence according to any of aspects A-16 to A-13, that comprises at least SEQ ID NO; 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO; 98 and SEQ ID NO; 121.

Aspect A-20. Amino acid sequence according to any of aspects A-15 to A-19, that comprises SEQ !D NO: 98, SEQ ID NO; 102 and SEQ ID NO: 121.

Aspect A-21. Amino acid sequence according to any of aspects A-l to A-20, that essentially consists of a Nanobody® that; a) has at least 80% amino acid identity with at least one of the amino acid sequences of SEQ ID NO's: 60-76,138-141 and 146-157, in which for the purposes of determining the degree of amino acid identity, the amino actd residues that form the CDR sequences are disregarded; and in which: b] preferably one or more of the amino acid residues at positions 11, 37,44,45,47, 83,84,103,104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table A-3 to Table A-8 of WO 08/020079.

Aspect A-22. Amino acid sequence according to any of aspects A-l to A-21, that essentially consists of a humanized Nanobody®.

Aspect A-23. Amino acid sequence according to aspect A-22, that essentially consists of a humanized Nanobody® which can bind (as further defined herein) to protein F of hRSV and which: i) is a humanized variant of the amino acid sequences of StQ ID NO: 5 (see Tabie A-l); and/or iij has at least 80% amino acid identity with the amino acid sequences of SEQ ID NO: 5 {see Table A-l) and/or at least one of the amino acid sequences of SEQ ID NO's: 50-76,138-141 and 146-157 (see Table A-4), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded; and in which: iii) preferably one or more of the amino acid residues at positions 11, 37,44,45,47, 83,84,103,104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table A-3 to Tabie A-8 of WO 08/020079.

Aspect A-24. Amino acid sequence according to any of aspects A-l to A-23, that is in essentially isolated form.

Aspect A-25. Amino acid sequence according to any of aspects A-i to A-24, for administration το a subject, wherein said amino acid sequence does not naturally occur in said subject.

Aspect A-26. Amino acid sequence according to any of aspects A-l to A-25, that can specifically bind to protein F of hRSV with a dissociation constant (Ko) of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect A-27. Amino acid sequence according to any of aspects A-l to A-26, that can specifically bind to protein F of hRSV with a kOP-rate of between 10'1 M'V" to about 107 M'V', preferably between 10s M'V1 and 107 M'V1, more preferably about 106 NT's*1 or more.

Aspect A-28. Amino acid sequence according to any of aspects A-l to A-27, that can specifically bind to protein F of hRSV with a koH rate between 10'2 s'1 (1-,/7=0.69 si and 10"4 s'1 {providing a near irreversible complex with a tI/2 of multiple days), preferably between 10's s"1 and iO"4 s'1, or lower.

Aspect A-29. Amino acid sequence according to any of aspects A-l to A-28, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) with an [C50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

Aspect 8-1. Nanobody® that is directed against and/or that specifically binds protein F of hRSV, in which CDR2 is chosen from: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that; i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference.

Aspect B-2. Nanobody® according to aspect B-l, in which CDR2 is chosen from the group consisting of: a) SEQ ID NO; 102; or b) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position G (position 54 determined according to Rabat numbering); anti ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one of CDR1 or CDR3 is chosen from: CDRI chosen from the group consisting of: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein} compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and/or CDR3 chosen from the group consisting of; e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino add difference.

Aspect 8-3. Nanobody® according to any of aspects B-l or B-2, in which: CDRI is chosen from the group consisting of: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and CDR2 is chosen from the group consisting of: c) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ (D NO: 102,, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and is) the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino act'd residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference; and CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; f} a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect B-4. Nano body® according to any of aspects B-i to B-3, that comprises at least SEQ ID NO: 102.

Aspect B-5. Nanobody® according to aspect B-4, that comprises at least SEQ ID NO: 102 and at least one CDR sequence chosen from: a) SEQ ID NO: 98; b) a stretch or amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ, ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; C) SEQ !D NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference,

Aspect B-6. Nanobody® according to any of aspects B-4 or B-5, that comprises at ieast SEQ iD NO: 102 and a CDR1 sequence chosen from: a) SEQ iD NO: 98; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and a CDR3 sequence chosen from: c) SEQ ID NO: 121; and dj a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hftSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect B-7. Nanobody® according to any of aspects B-4 to B-6, that comprises at least SEQ ID NO: 102 and at least one CDR sequence chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

Aspect B-S. Nanobody'®' according to any of aspects B-4 to B-7, that comprises SEQ ID NO: 98, SEQ, ID NO: 102 and SEQ ID NO: 121.

Aspect B-9. Nanobody® according to any of aspects B-i to B-S, that is in essentially isolated form.

Aspect B-10. Nanobody® according to any of aspects B-l to B-9, that can specifically bind to protein F of hRSV with a dissociation constant (KE) of 1000 r.M to 1 nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or iess.

Aspect B-ll. Nanobody8 according to any of aspects B-l to B-10, that can specifically bind to protein F of hRSV with a kos-rate of between 10f’ ΜΎ1 to about 107 M'V% preferably between 103 M'Y1 and 107 M'V1, more preferably about 10G M'V or more.

Aspect B-12, Nanobody5, according to any of aspects B-l to B-ll, that can specifically bind to protein F of hRSV with a ko;( rate between ΙΟ"' s'1 (1^=0.69 s) and IQ'4 s'1 (providing a near irreversible complex with a ti/2 of multiple days), preferably between 10‘3 s*1 and 10~ s'1, or lower.

Aspect B-13. Nanobody® according to any of aspects B-l to B-12, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) with an IC50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

Aspect B-14. Nano body® according to any of aspects B-l to B-13, that is a naturally occurring

Nanobody® (from any suitable species) or a synthetic or semi-synthetic Nanobodv®.

Aspect B-15. Nanobody® according to any of aspects B-l to B-14, that is a VHi, sequence, a partially humanized Vkh sequence, a fully humanized VHh sequence, a cametized heavy chain variable domain or a Nanobody® that has been obtained by techniques such as affinity maturation.

Aspect B-16. Nanobody0 according to any of aspects B-l to B-15, which is a partially humanized

Nanobody®.

Aspect B-17, Nanobody® according to any of aspects 8-1 to 8-16, which is a fully humanized Nanobody®,

Aspect B-18. Nanobody® according to any of aspects B-l to B-17, that essentially consists of a humanized Nanobody® which can bind (as further defined herein) to protein F of b.RSV and which: i) is a humanized variant of the amino acid sequences of SEQ ID NO: 5 (see Table A-l); and/or it) has at least 80% amino acid identity with the amino acid sequences of SEQ ID NO: 5 (see Table A-l) and/or at least one of the amino acid sequences of SEQ ID NO's: 60-76,138-141 and 146-157 (see Table A-4), in which for the purposes of determining the degree of amino acid identity, the amino acid residues that form the CDR sequences are disregarded; and in which: iii) preferably one or more of the amino acid residues at positions 11,37,44,45,47, 83, 84,103,104 and 108 according to the Kabat numbering are chosen from the Hallmark residues mentioned in Table A-3 to Table A-S of WO 08/020079.

Aspect C-l: Amino acid sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i} the amino acid sequence has a Giutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) trie amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or i amino acid difference.

Aspect C-2: Amino acid sequence according to aspect C-l, that comprises or essentially consists of one of SEQ ID NO's: 60-76.

Aspect C-3: Amino acid sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 62,65, 67, 68,75 and 75; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Giutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and i!) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect C-4: Amino add sequence according to aspect C-3, hat is chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine {Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect C-5: Amino acid sequence according to any of aspects C-3 or C-4, that comprises or essentiaiiy consists of one of SEQ ID NO's: 62,65,67, 68, 75 and 76.

Aspect C-6: Amino add sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D} at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect C-7: Amino acid sequence according to aspect C-6, that is chosen from the following: a) SEQ ID NO's:: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic add (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an

Arginine {Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the ammo acid sequence without the 3,2 or 1 amino acid difference.

Aspect C-S: Amino acid sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following: a; SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of 5EQ !D NO's: 146-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine [Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering): and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect C-S: Amino acid sequence according to aspect C-S, that comprises or essentially consists of one of SEQ ID NO's: 146-153.

Aspect C-10: Amino acid sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following; a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Protine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) ax position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, £) at position 85 and/or Giutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect C-ll: Amino acid sequence according to aspect C-10, that is chosen from the following; a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that nave no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with; SEQ ID NO: 146, the amino acid sequence preferably has Giutamine (Gin, Q) at position 105; SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic add (Glu, E) at position 85 and Giutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; SEQ ID NO: 152, the amino add sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino add sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3,2 or 1 amino acid difference.

Aspect C-12: Amino acid sequence according to any of aspects C-10 or C-12, that comprises or essentially consists of one of SEQ ID NO's: 146-149 and 151-153.

Aspect C-13: Amino add sequence comprising or essentiaily consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lie20Leu, Gtu44Gly, Ala74Ser, Gly7SLeu, A!a83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and GSy54D,

Aspect C-14: Amino acid sequence according to aspect C-13, comprising or essentially consisting of SEQ !D NO: 5, in which two or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, Iie20leu, Glu446iy, Ala74Ser, G!y78Leu, AlaS3Arg, AspS5Glu, ArglOSGin, GlnlOSLeu and Gly54D.

Aspect C-15: Amino acid sequence according to aspect C-14, comprising or essentially consisting of SEQ ID NO: 5, in which three or more amino acid residues have been mutated selected from the following: ValSLeu, Aial4Pro, Serl9R, !le20Leu, Glu446ly, Ala74Ser, Gly78Leu, AiaS3Arg, Asp85Glu, Argl05Gln, Ginl08Leu and Gly54D.

Aspect C-16: Amino add sequence according to aspect C-15, comprising or essentially consisting of SEQ ID NO: 5, in which four or more amino acid residues have been mutated selected from the following: ValSLeu, Aial4Pro, Serl9R, !)e20Leu, Glu44Giy, Aia74Ser, Giy78Leu, AiaSBArg, AspSSGtu, Argl05Gln, GlnlOSLeu and Gly54D.

Aspect C-17: Amino acid sequence according to aspect C-16, comprising or essentially consisting of SEQ ID NO: 5, in which five or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Aia745er, G!y78Leu, Ala83Arg, Asp85Giu, Argl05Gln, GlnlOSLeu and Gly54D.

Aspect C-18*. Amino acid sequence according to aspect C-17, comprising or essentially consisting of SEQ ID NO: 5, in which six or more amino acid residues have been mutated selected from the following: Va!5Leu, Aial4Pro, Serl9R, He20Leu, 6iu44Gly, Als74Ser, 6iy78Leu, Ala83Arg, Asp85Glu, ArglOSGIn, Glnl08Leu and Gly54D.

Aspect C-19: Amino acid sequence according to aspect C-18, comprising or essentially consisting of SEQ ID NO: 5, in which seven or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, Me20Leu, Glu44Gly, Aia74Ser, Gly78Leu, AlaSBArg, Asp85Glu, ArglOSGin, GlnlOSLeu and Gly54D.

Aspect C-20: Amino acid sequence according 10 aspect C-19, comprising or essentially consisting of 5EO. ID NO: 5, in which eight or more amino acid residues have been mutated selected from the following: VaISLeu, Aial4Pro, Serl9R, 5ie20Leu, Giu44Giy, Aia74Ser, Gly78Leu, AiaSBArg, Asp85Giu, ArglOSGin, Glnl08Leu and Gly54D.

Aspect C-21: Amino acid sequence according to aspect C-20, comprising or essentially consisting of SEQ ID NO: 5, in which nine or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Ala74Ser, Gly78leu, Aia83Arg, A.sp85Glu, ArglOSGin, GlnlOSLeu and Gly54D.

Aspect C-22: Amino acid sequence according to aspect C-21, comprising or essentially consisting of SEQ ID NO: 5, in which ten or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, !le20Leu, Giu44Giy, Ala74Ser, Gly78Leu, AlaSBArg, Asp85Glu, ArglOSGin, GinlOSLeu and Gly54D.

Aspect C-23: Amino acid sequence according to aspect C-22, comprising or essentially consisting of SEQ ID NO: 5, in which foliowing amino acid residues have been mutated: Val5Leu, A!al4Pro, Serl9R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGin, GinlOSLeu and Gly54D.

Aspect C-24: Amino acid sequence according to aspect C-1B, comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Serl9R, (le20Leu, Aia74Ser, Gly78Leu, Ala83Arg, AspSSGIu, ArglQ5Gln and Giy54D.

Aspect 025: Amine acid sequence according to aspect C-13, comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the fallowing: Gly78Leu, Ala83Arg, AspSSGIu, Argl05Gln and Gly54D.

Aspect 026; Amino acid sequence according to aspect 025, comprising or essentially consisting of SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, AIa83Arg, AspSSGIu, ArglOSGin and GlyS4D.

Aspect 027: Amino acid sequence comprising or essentially consisting of SEQ !D NO: 5, in which one or more amino acid residues have been mutated selected from the following: Ala'MPro, SerlSArg, !le2QLeu and GlnlOSLeu,

Aspect' 028: Amino add sequence comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Alal4Pro, SerlSArg, He20Leu, Aia83Arg, AspSSGIu, Argl05Gin and GlnlOSLeu.

Aspect C-29: Amino acid sequence according to aspect C-8, comprising or essentially consisting of SEQ ID NO: 5, wherein following amino acid residues have been mutated: - VaISLeu, Alal4Pro,. Giu44Gly, Giy?8leu, Ala83Arg, AspSSGIu, ArglOSGin and GlnlOSLeu;

AlaS3Arg, Asp85Glu, ArglOSGin and GlnlOSLeu;

Gly78Leu, Aia83Arg, AspSSGIu and ArglOSGin; - VaISLeu, Aial4Pro, Glu44Gly, Giy78Leu, Aia83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and GlyS4Asp; - Ala83Arg, Asp85Glu, ArglOSGin, GlnlOSLeu and Gly54Asp; - Gly78Leu, Ala83Arg, AspS5Giu, ArglOSGin and Gly54Asp;

Gly54Asp; A!al4Pro, Serl9Arg, lle20Leu and GlnlOSLeu; - Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Ala83Arg;

Aial4Pro, Serl9Arg, lie20Leu, Glnl08Leu and Asp85Glu;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu and Argl05Gln; - Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, AiaS3Arg and Asp85Glu;

Aial4Pro, Serl9Arg, ile20Leu, GlnlOSLeu, Aia83Arg and ArglOSGin;

Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AspSSGIu and ArglOSGin; or

Alal4Pro, Serl9Arg, iie20leu, G1nl08Leu, Ala83Arg, Asp85Giu and Arg 105Gin.

Aspect C-30: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 62.

Aspect C-31: Amino acid sequence comprising or essentially consisting of SEQ. iD NO: 65.

Aspect C-32: Amino add sequence comprising or essentially consisting of SEQ ID NO: 76.

Aspect C-33: Amino add sequence comprising or essentially consisting of any of SEQ ID NO's: 146- 153:76

Aspect C-34: Amino acid sequence according to any of aspects C-l to C-33, that can specifically bind to protein F of hRSV with a dissociation constant (KD) of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect C-35: Amino acid sequence according to any of aspects C-l to C-34, that can specifically bind to protein F of hRSV with a k„„-rate of between 104 M’V4 to about 107 M'V1, preferably between 10s M'V1 and 107 M'V1, more preferably about 106 M'YJ or more.

Aspect C-36: Amino add sequence according to any of aspects C-l to C-35, that can specifically bind to protein F of hRSV with a k0ff rate between 10'* s"‘ (t^=0.69 s) and 10J s'1 (providing a near irreversible complex with a of multiple days), preferably between 10'* s'1 and 10‘4 s'1, or lower.

Aspect C*37: Amino acid sequence according to any of aspects C-l to C-35, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) with an IC50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

Aspect C-38: Amino add sequence according to any of aspects C-l to C-37, that specifically binds antigenic site il on protein F of hRSV and/or that competes with Synagis® for binding protein F of hRSV.

Aspect D-i: Nanobody® that is directed against and/or specifically binds protein F of hR5V, chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine {Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect D-2: Nanobody® according to aspect D-l, that comprises or essentialiy consists of one of SEQ ID NO's: 60-76.

Aspect D-3: Nanobody® that is directed against and/or specifically binds protein r of hRSV chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68,75 and 76; b) amine add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Giutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position. 83 {said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect D-4: Nanobody® according to any of aspect D-3, that is chosen from the fotiowing: a) SEQ ID NO's: 62, 65, 67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ (D NO's: 62, 65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, 8} at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect D-5: Nanobody4' according to any of aspects D-3 or D-4, that comprises or essentially consists of one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76.

Aspect D-6: Nanobody® that is directed against and/or specifically binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, l) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect D-7: Nanobody'8 according to any of aspect D-6, that is chosen from the following: a) SEQ ID NO's:: 65 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q} at position 105, a Leucine (Leu, LJ at position 78 and an Arginine (Arg, R) at position S3 {said positions determined according to Rabat numbering); and the amino acid sequence binds protein - of hR.SV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect D-8: Nanobody*1 that is directed against and/or specifically binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Praline {Pro, p) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect D-9: Nanobody according to aspect D-8, that comprises or essentially consists of one of SEQ ID NO's: 146-153.

Aspect D-10: Nanobody that is directed against and/or specificaliy binds protein F of hRSV chosen from the following: a) SEQ ID NO's: 145-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a ProSine (Pro, P) at position 14, Arginine (Arg, R) at position IS, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R} at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference,

Aspect D-ll: Nanobody according to aspect D-1D, that is chosen from the following: a) SEQ 10 NO’s: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ ID NO; 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ ID NO: 147, the amino add sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ. ID NO: 151, the amino acid sequence preferably has Arginine {Arg, R) at position 83; SEO ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; SEO ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamic add {Glu, E) at position 85; {said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect D-12: Nanobody according to any of aspects D-10 or D-U, that comprises or essentially consists of one of SEQ. ID NO's: 146*149 and 151-153.

Aspect D-13: Nano body® comprising oressentialiy consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Va'5Leu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Aia74Ser, Gly78Leu, Aia83Arg, Asp85Glu, Argl05Gln, Glnl08Leu and Gly54D.

Aspect D-14: Nanobody® according to aspect D-13, comprising or essentially consisting of SEQ ID NO: 5, in which two or more amino acid residues have been mutated selected from the following: Val5Leu, Alal4Pro, Serl9R, lie20Leu, Giu44Giy, Aia74Ser, Gly78Leu, ASa83Arg, Asp85Glu, ArglOSGIn, GinlOSLeu and Gly54D.

Aspect D-15: Nanobody* according to aspect D-14, comprising or essentially consisting of SEQ ID NO: 5, in which three or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, iie20Leu, Glu44Giy, Ala74Ser, Giy78Leu, Ala83Arg, AspSSGlu, Argl05Gln, GinlOSLeu and Gly54D.

Aspect D-16: NanobodyE according to aspect D-150, comprising or essentially consisting of SEQ ID NO: 5, in which four or more amino acid residues have been mutated selected from the following: Va!5Leu, A!al4Pro, Serl9R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGIn, GinlOSLeu and G!y54D,

Aspect D-17: Nanobody® according to aspect D-16, comprising or essentially consisting of SEQ ID NO: 5, in which five or more amino acid residues have been mutated selected from the foliowing: Val5Leu, Alal4Pro, Serl9R, He20Leu, Giu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin, Ginl08Leu and Giy54D.

Aspect D-1S: Nanobody® according to aspect D-17, comprising or essentially consisting of SEQ !D NO: 5, in which six or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, SerI9R, Iie20leu, Giu44Gty, Ala74Ser, Giy78Leu, Aia83Argr Asp85Glu, Argl05Gin, GlnlOSLeu and Gly54D.

Aspect D-19: Nanobody® according to aspect D-1S, comprising or essentially consisting of SEQ ID NO: 5, in which seven or more amino acid residues have been mutated selected from the following: VaISLeu, Aial4Pro, Serl9R, Sle20Leu, Glu44Gly, Ala74Ser. Gly78Leu, Ala83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and Gty54D.

Aspect D-20: Nanobody® according to aspect D-19, comprising or essentially consisting of SEQ ID NO: 5, in which eight or more amino acid residues have been mutated selected from the following: Val5Leu, AiaX4Pro, Serl9R, lle20Leu, Glu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and Giy54D.

Aspect D-21: Nanobody® according to aspect D-20, comprising or essentially consisting of SEQ ID NO: 5, in which nine or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, !ie20Leu, Glu44Gly, Aia74Ser, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin, GlnlOSLeu and Gly54D,

Aspect D-22: Nanobody® according to aspect D-21, comprising or essentially consisting of SEQ ID NO: 5, in which ten or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, !le20Leu, Glu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, AspSSGiu, Argl05Gln, GlnlOSLeu and GlyS4D.

Aspect D-23: Nanobody® according to aspect D-22, comprising or essentially consisting of SEQ ID NO: 5, in which following amino acid residues have been mutated: VaISLeu, Alal4Pro, SerlSR, lie20Leu, 6iu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gln, GlnlOSLeu and Giy54D.

Aspect D-24: Nanobody® according to aspect D-l?>, comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Serl9R, !le20Leu, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGiu, ArglOSGin and Gly54D.

Aspect D-25: Nanobody® according to aspect D-S, comprising or essentially consisting of SEQ, ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Gly7SLeu, Ala83Argf AspSSGiu, Argl05Gln and Gly54D.

Aspect D-26: Nanobody® according to aspect D-2G, comprising or essentially consisting or SEQ iD NO: 5, in which following amino acid residues have bean mutated: Gly78Leu, AiaSBArg, Asp85Glu, ArglOSGIn and Gly54D.

Aspect D-27: Nanobody3' comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, lle20Leu and GlnlOSLeu.

Aspect P-28: Nanobody® comprising or essentially consisting of SEQ. ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Alal4Prc, Serl9Arg, lie2GLeu, AlaS3Arg, AspSSGiu, ArglOSGin and GlnlOSLeu.

Aspect D-29; Nanobody® according to aspect D-13, comprising or essentially consisting of SEQ ID NO: 5, wherein following amino acid residues have been mutated: - VaISLeu, Alal4Prc, Giu44Giy, Giy78leu, AiaS3Arg, AspSSGiu, ArglOSGin and Glnl08Leu;

Ala83Arg, AspSSGiu, Argl05Gln and GlnlOSLeu;

Gly78Leu, AlaSBArg, Asp85GSu and Argl05Gln; - VaISLeu, Alal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin, Glnl08Leu and Gly54Asp;

Ala83Arg, AspSSGiu, Argl05Gln, Glnl08Leu and Gly54Asp; - Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gln and Giy54Asp; - Gly54Asp;

Aial4Pro, Serl9Arg, lle20Leu and Glnl08Leu; - AiaI4Pro, Serl9Arg, lle20Leu, 6inl08leu and Ala83Arg;

Aiai4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Asp85Giu; - Aial4Pro, Serl9Arg, lle20Leu, GinlOSLeu and ArglOSGin;

Alal4Pro, Serl9Arg, ile20Leu, Ginl08Leu, AtaSBArg and AspSSGIu;

Atal4Pro, Serl9Arg, lle20Leu, GinlOSLeu, Ala83Arg and ArglOSGin;

Alal4Pro, Serl9Arg, lle20Leu, GinlOSLeu, Asp85Glu and ArglOSGin; or

Alal4Pro, SerlSArg, lle20Leu, Glnl08Leu, Aia83Arg, Asp85Glu and ArglOSGin.

Aspect D-30: Nanobody® comprising or essentially consisting of SEQ ID NO: 62.

Aspect D-31: Nanobody® comprising or essentially consisting of SEQ ID NO: 65.

Aspect D-32: Nanobody® comprising or essentially consisting of SEQ ID NO: 76.

Aspect D-33: Nanobody® comprising or essentially consisting of any of SEQ ID NO's: 148-153.

Aspect D-34: Nanobody® according to any of aspects D-l to D-33, that can specifically bind to protein F- of hRSV with a dissociation constant (Kt>) of 1000 nM to 1 nM or iess, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect D-35: Nanobody® according to any of aspects D-l to D-34, that can specifically bind to protein F of hRSV with a k0„-rste of between IQ4 M'YYo about 107 M'Y1, preferably between 105 Μ'V1 and 107 M'V", more preferably about 10e M'Y" or more.

Aspect D-36: Nanobody®· according to any of aspects D-l to D-35, that can specifically bind to protein F of hRSV with a koff rate between Iff7 s'" {t2/?=0,69 s} and ΙΟ17' {providing 3 near irreversible complex with a ti/; of multiple days}, preferably between Iff3 s’1 and Iff4 s'", or lower.

Aspect D-37: Nanobody® according to any of aspects D-l to D-36, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) with an 1C50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

Aspect D-38: Nanobody® according to any of aspects D-l to D-37, that specifically binds antigenic site li on protein F of hRSV and/or that competes with Synagis*’ for binding protein F of hRSV.

Aspect W-I: Amino acid sequence according to any of aspects A-l to A-29 and C-l to C-38, that is directed against and/or specifically binds protein F of hRSV, wherein the amino acid sequence has Aspartic acid (Asp, D) at position 1 {said position determined according to Kabat numbering).

Aspect W-2: Amino acid sequence that is directed against and/or specifically binds protein F of hRSV chosen from the following: 3} SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect W-3: Amino add sequence according to aspect W-2, that comprises or essentially consists of one of SEQ ID NO's: 138-141 and 154-157.

Aspect W-4: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-5: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 52, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-6: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 65, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-7: Amino acid sequence comprising or essentially consisting of SEQ !D NO; 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-8: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 75, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-9: Amino acid sequence comprising or essentially consisting of SEQ ID NO; 14-7, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-1C: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 149, in which the Giutamic add at position 1 has been changed into Aspartic acid.

Aspect W-ll: Amino add sequence comprising or essentially consisting of SEQ ID NO: 153, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-12: Amino acid sequence comprising or essentially consisting of SEQ ID NO; 5, in which one or mors amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, SerlSR, Ile20leu, Glu44G!y, Ala74Ser, Giy78Ueu, Aia83Arg, AspSSGiu, Argl05Gin, Glnl08Leu and Giy54D, and wherein the Glutamic add at position 1 has been changed into Aspartic acid.

Aspect W-13: Amino acid sequence according to aspect W-12, comprising or essentially consisting of SEQ ID NO: 5, in which two or more amino add residues have been mutated selected from the following: Va!5Leu, Alal4Pro, Serl9R, lle20Leu, Glu44Gly, Ala74Ser, Giy78Leu, Ala83Arg, AspSSGiu, Argl05Gln. GinlOSLeu and Giy54D, and wherein the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-14: Amino acid sequence according to aspect W-13, comprising or essentially consisting of SEQ ID NO: 5, in which three or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lle20Leu, Glu44Gly, Aia74Ser, Gly7SLeu, Ala83Arg, AspSSGiu, ArglOSGln, GinlOSLeu and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-15: Amino acid sequence according to aspect W-14, comprising or essentially consisting of SEQ ID NO: 5, in which four or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, !le20Leu, Giu44Giy, Ala74Ser, Gty78Leu, AiaSBArg, Asp85Glu( ArglOSGln, GinlOBLeu and Giy54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-16: Amino acid sequence according to aspect W-15, comprising or essentially consisting of SEQ ID NO: 5, in which five or more amino add residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, He20Leu, Glu44Gly, Aia74Ser, Gly78Leu, Ala83Arg, AspSSGIu, ArglOSGln, Glnl08Leu and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-17: Amino acid sequence according to aspect W-16, comprising or essentially consisting of SEO ID NO: 5, in which six or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Gtu, ArglOSGln, Glnl08Leu and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-18: Amino acid sequence according to aspect W-17, comprising or essentially consisting of SEQ ID NO: 5, in which seven or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, $erl9R, He20Leu, Giu44Gly, Aia74Ser, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGln, GlnlOSLeu and 6!y54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-19: Amino acid sequence according to aspect W-18, comprising or essentially consisting of SEQ ID NO: 3, in which eight or more amino acid residues have been mutated selected from the following: ValSLeu, Alal4Pro, Serl9R, lle2GLeu, Glu44Gty, Ala74Ser, Gly78leu, AiaSBArg, AspSSGIu, ArglOSGln, GlnlOSLeu and Giy54D, and wherein the Glutamic add at position 1 has been changed into Asoartic acid.

Aspect W-20: Amino acid sequence according to aspect W-19, comprising or essentially consisting of SEQ ID NO: 5, in which nine or more amino acid residues have been mutated selected from the following: Vat5Leu, Alal4Pro, Serl9R, lle20Leu, Giu44Giy, Aia74Ser, Giy78leu, Ala23Arg, Asp85Glu, ArglOSGln, GlnlOSLeu and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-21: Amino acid sequence according to aspect W-20, comprising or essentialiy consisting of SEG ID NO: 5, in which ten or more amino add residues have been mutated selected from the following: VaISLeu. Alal4Pro, Serl9R, Ile20leu, GkiMGiy, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGin, GinlOSLeu and Gly54Df and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-22: Amino acid sequence according to aspect W-21, comprising or essentialiy consisting of SEG !D NO: 5, in which following amino acid residues have been mutated: ValSLeu, Alal4Pro, Serl9R, lle20Leu, Giu44Giy, Ala745er, Giy78Leu, Ala83Arg, AspSBGIu, ArglOSGin, G!nl08Leu and GiySAD, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-23: Amino acid sequence according to aspect W-12, comprising or essentialiy consisting of SEG ID NO: 5, in which one or more amino add residues have been mutated selected from the following: Serl9R, lle20Leu, Ala74Ser, G!y78Leu, Aia83Arg, AspSSGlu, ArglOSGin and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-24: Amino acid sequence according to aspect W-12, comprising or essentially consisting of SEG ID NO: 5, in which one or more amino add residues have been mutated selected from the following: Gly78l.au, Ala83Arg, AspBSGiu, ArglOSGin and Gly54D, and wherein the giutamic add at position 1 has been changed into Aspartic acid.

Aspect W-25: Amino acid sequence according to aspect W-24, comprising or essentially consisting of SEG ID NO: 5, in which following amino acid residues have been mutated: Giy78Leu, A!a83Arg, Asp85G!u, Argl05Gln and Giy54D, and wherein the glutamic acid at position 1 has been changed into Aspartic acid.

Aspect W-26: Amino acid sequence comprising or essentially consisting of SEG ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, Ue20Leu and 6inl08leu, and wherein the Giutamic add at position 1 has been changed into Aspartic add.

Aspect W-27: Amino acid sequence comprising or essentially consisting of SEG ID NO: 5, in which one or more amino acid residues have been mutated selected from the following:

Aial4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSSGlu, ArglOSGin and GinlOSLeu, and wherein the Glutamic add at position 1 has been changed into Aspartic acid.

Aspect W-28: Amino acid sequence according to aspect W-2 or W-3, comprising or essentially consisting of SEQ ID NO: 5, wherein following amino acid residues have been mutated:

GiulAsp, ValSLeu, Aial4Pro, Glu44Giy, G!y78Leu, AiaSBArg, AspSSGlu, ArglOSGin and Glnl08Leu;

GiulAsp, AlaS3Arg, Asp85Giu, Argi05Gin and GinlOSLeu;

GiulAsp, Gly78Leu, Aia83Arg, AspSSGlu and Argl05Gin;

GiulAsp, VaiSLeu, Alal4Pro, Giu44Gly, 6!y7SLeu, A!a83Arg, Asp85Giu, ArglOSGin, GinlOSLeu and Gly54Asp; - GiulAsp, Ala83Arg, Asp85Glu, ArglOSGin, Glnl08Leu and Giy54Asp;

GiulAsp, Gly78Leu, AiaSBArg, AspSSGlu, ArglOSGin and Gly54Asp;

GiulAsp and Gly54Asp;

GiulAsp, Aial4Pro, Serl9Arg, He20Leu and GinlOSLeu;

GiulAsp, Alal4Pro, Serl9Arg, He20Leu, GinlOSLeu and AiaSSArg;

GiulAsp, Alal4Pro, Serl9Arg, lle20Leu, GinlOSLeu and AspSSGiu;

GiulAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu and ArglOSGin;

GiulAsp, Alal4Pro, Serl9Arg, ile20Leu, GinlOSLeu, Ala83Arg and Asp85Glu; GiulAsp, Alal4Pro, SerlSArg, ile20Leu, GinlOSLeu, Aia83Arg and ArglOSGin; GiulAsp, Aial4Pro, SerlSArg, lle20Leu, GinlOSLeu, AspSSGiu and ArglOSGin; or GiulAsp, Atal4Pro, SerlSArg, ile20Leu, GinlOSLeu, Aia83Arg, Asp85Glu and ArglOSGin.

Aspect W-29: Amino acid sequence comprising or essentially consisting of SEQ. ID NO: 138,

Aspect W-30: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 139.

Aspect W-31: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 140.

Aspect W-32: Amino acid sequence comprising or essentially consisting of SEQ ID NO: 141.

Aspect W-33: Amino add sequence comprising or essentially consisting of any of SEQ ID NO's: 154-157.

Aspect W-34: Amino acid sequence according to any of aspects W-l to W-33, that can specifically bind to protein F of hRSV with a dissociation constant (KD) of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect W-35: Amino acid sequence according to any of aspects W-l to W-34, that can specifically bind to protein F of hRSV with a kc„-rate of between 104 M'V to about 10' M's1, preferably between 10s M'V* and 107 M’*s Λ more preferably about 106 NTs'1 or more.

Aspect W-3S: Amino acid sequence according to any of aspects W-l to W-35, that can specifically bind to protein F of hRSV with a karate between 10" s'* (ΐι/2=0.59 s) and 10“' s'* (providing a near irreversible complex with a t1/: of multiple days), preferably between 10‘3 s'1 and 10-4 s'1, or lower.

Aspect W-37: Amino acid sequence according to any of aspects W-l to W-35, that can neutralize hRSV {for example, as measured in a microneutraiization assay on hRSV/ Long (such as e.g, described in Example 6) with an 1C50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nfVI, or less.

Aspect W-38: Amino acid sequence according to any of aspects W-I to W-37, that specifically binds antigenic site IS on protein F of hRSV and/or that competes with Synagis® for binding protein f of hRSV.

Aspect X-l: Nanobody that is directed against and/or specifically binds protein F of hRSV according to any of aspects B-l to B-18 and D-l to D-38, wherein the Nanobody has Aspartic add (Asp, D) at position 1 {said position determined according to Rabat numbering).

Aspect X-2: Nanobody* that is directed against and/or specifically binds protein F of hRSV, chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i} the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Rabat numbering); and ii) the amino acid sequence binds protein f of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid seauence without the 3, 2 or 1 amino acid difference.

Aspect X-3: Nanobody® according to aspect X-2, that comprises or essentially consists of one of SEQ ID NO’s; 138-141 and 154-157.

Aspect X-4: Nanobody® comprising or essentially consisting of SEQ ID NO: 5, in which Giutamic add at position 1 has been changed into Aspartic acid.

Aspect X-5: Nanobody® comprising or essentially consisting of SEQ ID NO: 52, in which Glutamic acid at position i has been changed into Aspartic acid.

Aspect X-6: Nanobody® comprising or essentially consisting of SEQ ID NO: 65, in which Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-7: Nanobodv® comprising or essentially consisting of SEQ iD NO: 75, in which Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-8: Nanobody® comprising or essentially consisting of SEQ ID NO: 75, in which Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-9: Nanobody® comprising or essentially consisting of SEQ ID NO: 147, in which Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-10: Nanobody® comprising or essentially consisting of SEQ ID NO: 149, in which Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-ll: Nanobody6' comprising or essentially consisting of SEQ ID NO: 153, in which Glutamic acid at position 1 has been changed into Aspartic add.

Aspect X-12: Nanobody6 comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: VaiSLeu, Aial4Pro, SerlSR, lle20Leu, Giu44Gly, Ala74Ssr, Giy78Leu, AiaSSArg, Asp85Giu, ArglOSGin, Glnl08Leu and Gly54D, and wherein Glutamic acid at position ί has been changed into Aspartic acid.

Aspect X-13: Nanobody® according to aspect ΧΊ2, comprising or essentially consisting of SEQ ID NO: 5, in which two or more amino acid residues have been mutated selected from the following: Val5Leu, A!al4Pro, Serl9R, ISe20Leu, Giu44Gly, Ala74Ser, Giy78Leu, Aia83Arg, Asp856iu, ArglOSGin, GlnlOSLeu and Gly54D, and wherein Glutamic add at position 1 has been changed into Aspartic acid.

Aspect X-14: Nanobody® according to aspect X-13, comprising or essentially consisting of SEQ ID NO; 5, in which three or more amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, He20Leu, Glu44Gly, Ala74Ser, Giy78Leu, Ala83Arg, Asp85Glu, Argi05Gln, GlnlOSLeu and Gly54D, and wherein Giutamic acid at position I has been changed into Aspartic acid.

Aspect X-iS: Nanobody® according to aspect X-14, comprising or essentially consisting of SEQ ID NO: S, in which four or more amino acid residues have been mutated selected from the following: VaiSLeu, A!al4Pro, SerlSR, ile20Leu, Giu44Gly, Aia74Ser, 5ly78Leu, Ala83Arg, Asp85Glu, ArglOSGin, Ginl08Leu and GlyS4D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-16: Nanobody® according to aspect X-15, comprising or essentially consisting of SEQ ID NO: 5, in which five or more amino acid residues have been mutated selected from the following: Va!5Leu, Alal4Pro, Serl9R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ata83Arg, Asp8561u, Argl05Gln, Glnl08Leu and Giy54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-17: Nanobody* according to aspect X-16, comprising or essentially consisting of SEQ ID NO: 5, in which six or more amino acid residues Have been mutated selected from the following: VaiSLeu, Aial4Pro, Serl9R, lle20Leu, Glu44Giy, Aia74Ser, Giv78Leu, AiaSBArg, Asp85Glu, ArglOSGin, GlnlOSLeu and Gly54D, and wherein Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-18: Nanobody®' according to aspect X-17, comprising or essentially consisting of SEQ ID NO: 5, in which seven or more amino acid residues have been mutated selected from the following: VaiSLeu, A!al4Pro, Serl9R, ile20Leu, Giu44Giy, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin, Glnl08Leu and GivS4D, and wherein Giutamic acid at position i has been changed into Aspartic acid.

Aspect X-19: Nano body* according to aspect X-18, comprising or essentially consisting of SEQ ID NO: 5, in which eight or more amino acid residues nave been mutated selected from the following: VaiSLeu, ASslAPro, SsrlSR, lle20Leu, Glu44Giy, Ala74$er, Giv7SLeu, AiaBBArg, Asp85Glu, ArglOSGin, GlnlOSLeu and Gly54D, and wherein Giutamic add at position 1 has been changed into Aspartic acid.

Aspect X-2C: Nanobody® according to aspect X-19, comprising or essentially consisting of SEQ ID NO: 5, in which nine or more amino acid residues have been mutated selected from the following: VaiSLeu, Aial4Pro, SerlSR, Iie20leu, Glu44Giy, Aia74Ser, Giy78Leu, AiaSBArg, AspSSGIu, ArglOSGin, Glnl08Leu and Giy54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-21: Nanobody* according to aspect X-20, comprising or essentially consisting of SEQ ID NO: 5, in which ten or more amino acid residues have been mutated selected from the following: VaiSLeu, Aial4Pro, SerlSR, l!e20Leu, Glu44Gly, Als74Ser, Gly78Leu, AiaSBArg, AspSSGiu, ArglOSGin, GlnlOSLeu and Gly54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-22: Nanobody® according to aspect X-21, comprising or essentialiy consisting of SEQ ID NO: 5, in which following amino acid residues have been mutated: VaiSLeu, Aial4Pro, Serl9R, He20Leu, Gtu44Gly, A!a74Ser, Giy78Leu, Aia83Arg, AspSSGiu, ArglOSGin, Ginl08Leu and GSy54D, and wherein Glutamic acid at position 1 has been changed into Aspartic add.

Aspect X-23: Nanobody® according το aspect X-12, comprising or essentially consisting of SEQ ID NO: 5, in whtch one or more amino acid residues have been mutated selected from the following: Serl9R, He20Leu, Aia74Ser, Giy78Leu, AlaS3Arg, AspSSGiu, ArglOSGin and Giy54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-24: Nanobody® according to aspect X-12, comprising or essentially consisting of SEQ iD NO: 5, in which one or more amino acid residues have been mutated selected from the following: Gly78Leu, Aia83Arg, AspSSGiu, ArglOSGin and Gly54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-25: Nanobody® according to aspect X-24, comprising or essentially consisting of SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, Ai383Arg, Asp85Giu, Argl05Gln and Giy54D, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-26: Nanobody® comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Alal4Pro. SerlOArg, i!e2QLeu and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-27: Nanobody** comprising or essentially consisting of SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, !ie20Leu, Ala83Arg, AspSSGiu, ArglOSGin and GlnlOSLeu, and wherein Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect X-28: Nanobody® according to aspecrX-2, comprising or essentially consisting of SEQ ID NO: 5, wherein following amino acid residues have been mutated:

GlulAsp, ValSLeu, Alal4Pro, Giu44Gly, G!y78Leu, Ala83Arg, AspSSGiu, ArglOSGin and GlnlOSLeu;

GlulAsp, Aia83Arg, Asp85Glu, ArglOSGin and GlnlOSLeu;

GlulAsp, Gly78Leu, Aia83Arg, AspSSGiu and ArglOSGin; - GlulAsp, ValSLeu, Alal4Pro, Glu44Giy, Giy78Leu, Ala83Arg, AspSSGiu, ArglOSGin, GlnlOSLeu and Gly54Asp;

GluIAsp, ASaS3Arg, AspSSGiu, ArglOSGin, Gtnl08leu and Gly54Asp; - GluIAsp, Giy78Leu, Ala83Arg, Asp85Glu, ArglOSGin and Gly54Asp;

GluIAsp and Giy54Asp;

GluIAsp, Aial4Pro, SerlSArg, lle20Leu and GlnlOSLeu;

GluIAsp, Alal4Prc, SsrlSArg, lls20Leu, GlnlOSLeu and Ala83Arg; - GluIAsp, Alal4Pro, Serl9Arg, ile20Leu, GlnlOSLeu and AspSSGiu;

GluIAsp, AlalAPro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGIn;

GiulAsp, AlslAPro, Serl9Arg, lle20Leu, GlnlOSLeu, AlaS3Arg and Asp8SGIu; GluIAsp, Alal4Pro, Serl9Arg, lleZOLeu, Glnl08Leu, Ala83Arg and Argl05Gln; GluIAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, AspSSGiu and ArglOSGin; or GluIAsp, Aial4Prc, Serl9Arg, Ue20Leu, GlnlOSLeu, Ala83Arg, AspSSGiu and Argl05Gin.

Aspect X-2S: Nanobody® comprising or essentially consisting of SEQ ID MO: 138.

Aspect X-3G: Nanobody8 comprising or essentially consisting of SEQ ID NO: 139.

Aspect X-31: Nanobody® comprising or essentially consisting of SEQ ID NO: 140.

Aspect X-32: Nanobody® comprising or essentially consisting of SEQ ID NO: 141.

Aspect X-33: Nanobody® comprising or essentially consisting of any of SEQ ID NO's: 154-157.

Aspect X-34: Nanobody* according to any of aspects X-l to X-33, that can specifically bind to protein F of hRSV with a dissociation constant (KD) of 1000 nM to 1 nM or iess, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect X-35: Nanobody® according to any of aspects X-l to X-34, that can specifically bind to protein F of hRSV with a k^-rate of between 10* MV1 to about 107 M' s'1, preferably between 105 M’V1 and 107 mV1, more preferably about 10° ΜV1 or more.

Aspect X-36: Nanobodv® according to any of aspects X-l to X-35, that can specifically bind to protein F of hRSV with a rate between 103 s'1 (tj/j=0.69 s) and 10"1 s'1 (providing a near irreversible complex with a tyj of multipie days), preferably between 10'3 s'* and 10"* s'", or tower.

Aspect X-37: Nanobody® according to any of aspects X-i to X-36, that can neutralize hRSV {for example, as measured in a microneutralization assay on hRSV Long {such as e.g. described in Example 6) with an IC50 value between 100 nM and 1000 nM, preferably between 100 nM and 500 nM, or less.

Aspect X-38: Nanobody* according to any of aspects X-i to X-37, that specifically binds antigenic site II on protein F of hRSV and/or that competes with Svnagis® for binding protein F of hRSV.

Aspect E-l: Polypeptide that comprises or essentially consists of one or more amino acid sequences according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 and/or one or more IManobodies® according to any of aspects B-l το B-18, D-l ίο B-38 and X-2 to X-38, and optionally further comprises one or more other amino acid binding units, optionally linked via one or more peptidic linkers.

Aspect E-2: Polypeptide according to aspect E-l, in which said one or more other binding units are immunoglobulin sequences.

Aspect E-3: Polypeptide according to any of aspects E-l or E-2, in which said one or more other binding units are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino acid sequences that are suitable for use as a dAb, or Nanobodies®.

Aspect E-4: Polypeptide according to any of aspects E-l to E-3, in which said one or more amino add sequences are immunoglobulin sequences.

Aspect E-5: Polypeptide according to any of aspects E-l to E-4, in which said one or more amino acid sequences are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino add sequences that are suitable for use as a dAb, or Nanobodies®.

Aspect E-6: Polypeptide according to any of aspects E-i to E-5, that comprises or essentially consists of one or more Nanobodies® according to any of aspects ΒΊ to 8-18, D-l to D-8 and X-l to X-3S and in which said one or more other binding units are Nano bodies®'.

Aspect E-7: Polypeptide according to any of aspects E-l to E-6, which is a multivalent construct.

Aspect E-8: Multivalent poiypeptide according to aspect E-7, that comprises or essentially consists of at least two amino add sequences according to any of aspects A-l to A-29 and C-l to C-38 and/or Nanobodies® according to any of aspects B-l to B-18 and D-l to D-38 and/or at least one amino add sequence according to any of aspects W-l to VV-38 and/or at least one Nanobody® according to any of aspects X-l to X-38.

Aspect E-9: Multivalent polypeptide according to aspect E-8, wherein said at least two amino acid sequences and/or Nanobodies4' are identical.

Aspect E-10: Multivalent polypeptide according to any of aspects E-7 to E-9, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 102, provided that: i) said stretch of amino add residues has an Aspartic acid {Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-ll: Multivalent polypeptide according to any of aspects E-7 to E-IQ, comprising or essentially consisting of at least two amino acid sequences and/or Manobodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one stretch is chosen from: c) SEQ ID NO: 9S; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 121; and f) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the ammo acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino add residues that corresponds to one of a) and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Aspect E-12; Multivalent polypeptide according to any of aspects E-7 to E-ll, comprising or essentially consisting of at ieast two amino acid sequences and/or Nanoboa'iesK that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: SS; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; a second stretch of amino acid residues chosen from the group consisting of: c) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEO. ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino add difference; and a third stretch of amino acid residues chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-13; Multivalent polypeptide according to any of aspects E-7 to E-12, comprising or essentially consisting of at least two amino add sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102.

Aspect E-14: Multivalent polypeptide according to any of aspects E-7 to E-13, comprising or essentially consisting of at least two amino add sequences and/or Nanobodies* that comprise at least SEQ ID NO: 102 and at least one stretch of amir.o add residues (CDR sequence) chosen from: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-1S: Multivalent polypeptide according to any of aspects E-7 to E-14, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and a CDR1 sequence chosen from: a) SEQ, ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein E of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and a CDR3 sequence chosen from: c) SEQ ID NO: 121; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-16: Multivalent polypeptide according to any of aspects E-7 to E-15, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® that comprise at least SEQ iD NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ ID NO; 121.

Aspect E-17: Multivalent polypeptide according to any of aspects E-7 to E-16, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies®' that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

Aspect E-18: Multivalent polypeptide according to any of aspect E-8 to E-17, wherein said at least two amino acid sequences and/or Nanobodies® are identical.

Aspect E-19: Multivalent polypeptide according to any of aspects E-7 to E-9, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® chosen from the following: 3} SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NOfs: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency fas defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-20: Multivalent polypeptide according to aspect E-19, wherein said at least two amino add sequences and/or Nanobodies® are identical.

Aspect EE-21; Multivalent polypeptide according to aspect E-20, that comprises or essentially consists of at least two identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 60-76,

Aspect E-22: Multivalent polypeptide according to any of aspects E-7 to E-9, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67,68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 205, a leucine (Leu, L} at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity'as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3,2 or 1 amino acid difference.

Aspect E-23: Multivalent polypeptide according to aspect E-22, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodiss* chosen from the foliowing: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67,68, 75 and 76, provided that: ij the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-24: Multivalent polypeptide according to any of aspects E-22 or E-23, wherein said at least two amino acid sequences and/or Nanobodies® are identical

Aspect E-25; Multivalent polypeptide according to aspect E-24, that comprises or essentially consists of at least two identical amino acid sequences and/or Nanobodies* chosen from one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

Aspect E-26: Multivalent polypeptide according to any of aspects t-7 to E-9, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: t) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a

Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein! compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect £-27: Multivalent polypeptide according to aspect E-26, comprising or essentially consisting of at ieast two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-2S: Multivalent polypeptide according to any of aspects E-26 or E-27, wherein said at least two amino acid sequences and/or Nanobodies® are identical.

Aspect E-29: Multivalent polypeptide according to aspect E-28. that comprises or essentially consists of at least two identical amino acid sequences and/or Nanobodies® chosen from SEC- ID NO's: 65 and 76.

Aspect E-30: Multivalent polypeptide according to any of aspects E-7 to E-S, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® chosen from the following: a] SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2. more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: i) the amino add sequence has a Proiine (Prc, P) at position 14, Arginine (Arg, R) at position 19, Leucine {Leu, L) at position 20 and Leucine (Leu, L) at position 10S (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-31: Multivalent polypeptide according to aspect E-30, wherein said at least two amino add sequences and/or Nanobodies® are identical.

Aspect E-32: Multivalent polypeptide according to aspect E-31, that comprises or essentially consists of at least two identical amino add sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 146-153.

Aspect E-33: Multivalent polypeptide according to any of aspects E-7 to E-9, comprising or essentially consisting of at (east two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that; i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and is) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-34: Multivalent polypeptide according to aspect E-33, comprising or essentiaiiy consisting of at least two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151Ί53, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Giutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ. ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Giutamine (Gin, Q) at position IDS; SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Giutamine (Gin, Q) at position 105; - SEQ ID NO: 14S, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; SEQ ID NO; 253, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Giutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-35: Multivalent polypeptide according to any of aspects E-33 or E-34, wherein said at ieasi two amino acid sequences and/or Nanobodies® are identical.

Aspect E-36: Multivalent polypeptide according to aspect E-35, that comprises or essentially consists of at least two identical amino acid sequences and/or Nanobodies* chosen from one of SEQ ID NO’s; 62, 65,67, 68, 75,76,147,149 and 153.

Aspect E-37; Multivalent polypeptide comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven, or twelve) amino add residues have been mutated selected from the following; Va!5Leu, Alal4Pro, SerlSR, lie2QLeu, Glu44Gly, A!a74Ser, Giy78Leu, AlaSBArg, AspSSGiu, ArglOSGln, GlnlOSLeu and Gly54Asp.

Aspect E-38: Multivalent polypeptide according to aspect E-37, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid residues have been mutated: Val5Leu, Alal4Pro, Serl9R, lle20Leu, Glu44Gly, ASa74$er, G!y78leu, Ala83Arg, AspSSGiu, ArglOSGln, GlnlOSLeu and Gly54D.

Aspect E-39: Multivalent polypeptide according to aspect E-37, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following; Serl9R, !ie20Leu, Ala74Ser, Gly78Leu, Ala83Arg, A$p85Glu, ArglOSGin and Giy54Q.

Aspect E-40: Multivalent polypeptide according to aspect £-37, comprising or essentially consisting of at least two amino add sequences and/or Nanobodies® with SEQ ID NO: S, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following; Gly78Leu, AlaSSArg, AspSSGIu, ArglOSGin and 6lv54D.

Aspect E-41: Multivalent polypeptide according to aspect E-40, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, m which following amino acid residues have been mutated; Gly7SLeu, Aia83Arg, Asp85Glu, ArglOSGin and Gly54D.

Aspect E-42: Multivalent polypeptide comprising or essentially consisting of at least two amino add sequences and/or Nanobodies® with 5EQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Aial4Prc, Serl9Arg, lie20Leu and GlnlOSLeu.

Aspect c-43: Multivalent polypeptide comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies® with SEQ, ID NO: 5, in which one or snore (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, He20leu, Aia83Arg, AspS5Glu, ArglOSGin and GlnlOSLeu.

Aspect E-44: Multivalent polypeptide according to aspect £-37, comprising or essentially consisting of at least two amino acid sequences and/or Nanobodies1® with SEQ ID NO: 5, in which following amino add residues have been mutated:

ValSLeu, Alal4Pro, Glu44Giy, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin and GlnlOSLeu;

Ala83Arg, Asp85Glu, ArglOSGin and GlnlOSLeu; G!y78Leu, Ala83Arg, AspSSGIu and ArglOSGin;

ValSLeu, Alal4Pro, Glu44Gly, Gly78Leu, ASa83Arg, AspSSGIu, ArglOSGin, GlnlOSLeu and G!y54Asp;

Ala83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Giv54Asp;

Gly78Leu, Aia83Arg, Asp8SGiu, ArglOSGIn and Gly34Asp;

Gty54Asp; - Alal4Pro, Serl9Arg, l!e20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, t)e20Leu, GlnlOSLeu and ASaSBArg;

Algl4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and AspSSGIu;

Alal4Pro, SerlSArg, lle2QLeu, GlnlOSLeu and ArglOSGIn; - Alal4Pro, Serl9Arg, lleZOLeu, GlnlOSLeu, Ala83Arg and AspS5GSu; - Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, AiaSSArg and ArglOSGIn;

Alal4Pro, Sert9Arg, !le2QLeu, GlnlOSLeu, AspSSGIu and ArglOSGIn; or - Alal4Prc, Serl9Arg, lle20Leu, GlnlOSLeu, AiaSSArg, Asp856lu and ArglOSGIn,

Aspect E-45: Multivalent polypeptide according to aspect E-7, that comprises or essentially consists of at least three amino acid sequences according to any of aspects A-l to A-29, C-l to C-3S and W-l to VV-38 and/or Nanobodtes® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38.

Aspect E-46: Multivalent polypeptide according to aspect E-45, wherein said at ieast three amino acid sequences and/or Nanobodies0 are identical.

Aspect E-47: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at least three amino add sequences and/or Nanobodies'5' that comprise at least a stretch of amino acid residues chosen from the following: aj SEQ !D NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Rabat numbering); and ii) the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, ora higher potency (asdefined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference.

Aspect E-48: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NG: 102; b} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than i amino acid difference with SEQ. ID NO: 202, provided that: i) said stretch of amino acid residues has an Aspartic acid {Asp, 0) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) 3nd/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one stretch is chosen from; c) SEQ ID NO; 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ iD NO; 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino add residues without the 3, 2 or 1 amino acid difference; e) SEQ ID NO: 122; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino add residues that corresponds to one of a) and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Aspect E-49: Multivalent polypeptide according to any of aspects E-4S or E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies* that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 98; and b} a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEO ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F ofhRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; a second stretch of amino acid residues chosen from the group consisting of: c) SEQ ID NO: 102; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; and a third stretch of amino acid residues chosen from the group consisting of: e} SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein f of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance} and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-5G: Multivalent polypeptide according to any of aspects E-45 to E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102.

Aspect E-51: Multivalent polypeptide according to any of aspects E-45 to E-46, comprising or essentially consisting of at feast three amino acid sequences and/or Nanobodies41 that comprise at least SEQ ID NO: 102 and at least one stretch of amino acid residues {CDR sequence} chosen from: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO; 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmor. resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-52: Multivalent polypeptide according to any of aspects E-45 to E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies* that comprises at least SEQ ID NO: 102 and a CDR1 sequence chosen from: e) SEQ ID NO: 9S; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ !D NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference: and a CDR3 sequence chosen from: c) SEQ iD NO: 121; and d) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of HRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-53: Multivalent polypeptide according to any of aspects E-45 to E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and at ieast one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

Aspect E-54: Multivalent polypeptide according to any of aspects E-45 to E-46, comprising or essentially consisting of at ieast three amino acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

Aspect E-55: Multivalent polypeptide according to any of aspect £-47 to E-53, wherein said at ieast three amino acid sequences and/or Nanobodies® are identical.

Aspect E-56: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at ieast three amino acid sequences and/o' Nanobodies6' chosen from the following: a) SEQ ID NO's: 60-76: b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Giutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect £-57: Multivalent polypeptide according to aspect E-56, wherein said at least three amino add sequences and/or Nanobodies® are identical.

Aspect E-5S: Multivalent polypeptide according to aspect E-57, that comprises or essentially consists of at least three identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

Aspect E-59: Multivalent polypeptide according to any of aspects E-45 or E-45, comprising or essentially consisting of at ieast three amino acid sequences and/or Nanobodies® chosen from the following: a} SEQ ID NO's: 62, 65,67, 68, 75 and 76; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 62, 65, 67, 68,75 and 76, provided that: i} the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amine acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-60: Multivalent polypeptide according to aspect E-59, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 62, 65,67, 58, 75 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEO, ID NO's: 62, 65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Giutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference.

Aspect E'6i: Multivalent polypeptide according to any of aspects E-59 or E-60, wherein said at least three amino acid sequences and/or Nanobodies* are identical.

Aspect E-62: Multivalent polypeptide according to aspect E-61, that comprises or essentially consists of at least three identical amino acid sequences and/or Nanobodies® chosen from one of SEQ iD NO's: 62,65, 67, 68, 75 and 76.

Aspect E-63: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodses® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid {Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 76 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-64: Multivalent polypeptide according to aspect E-63, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO’s: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine {Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-5S: Multivalent polypeptide according to any of aspects E-63 or E-64, wherein said at least three amino acid sequences and/or Nanobodies® are identical.

Aspect E-66: Multivalent polypeptide according to aspect E-65, that comprises or essentially consists of at least three identical amino acid sequences and/or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

Aspect E-57: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: ij the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-6S; Multivalent polypeptide according to aspect E-67, wherein said at least three amino acid sequences and/or Nanobodies® are identical.

Aspect E-69: Multivalent polypeptide according to aspect E-68, that comprises or essentially consists of at least three identical amino acid sequences and/or Nanobodies8 chosen from one of SEQ ID NO's: 146-153.

Aspect E-70: Multivalent polypeptide according to any of aspects E-45 or E-46, comprising or essentially consisting of at least three amino add sequences and/or Nanobodies* chosen from the following: a) SEQ ID NO's: 146-149 and 151-1S3; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and IS 1-153, provided that: i} the amino acid sequence has a Proline (Pro, P) at position 14, Arginine {Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-71: Multivalent polypeptide according to aspect E-70, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NQ's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, t) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ ID NO; 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; - SEQ ID NO; 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position S3, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; SEQ, ID NO: 152, the amino add sequence preferably has Glutamic acid (Glu, E) at position 85; SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-72: Multivalent polypeptide according to any of aspects E-70 or E-71, wherein said at least three amino acid sequences and/or Nanobodies® are identical.

Aspect E-73: Multivalent polypeptide according to aspect E-72, that comprises or essentially consists of at least three identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68, 75,76,147,149 and 153.

Aspect E-74: Multivalent polypeptide comprising or essentially consisting of at least three amino acid sequences and/or Nanobcdies® with SEQ ID NO: 3, in which one or more (such as two, three, four, five, si>:, seven, eight or nine, ten, eleven, or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alai4Pro, Serl9R, lle20Leu, Giu44Gly, Ala74Ser, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGIn, Ginl08Leu and Gly54Asp.

Aspect E-75: Multivalent polypeptide according to aspect E-74, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid residues have been mutated: VaISLeu, Alal4Pro, Serl9P,, lle20Leu, Giu44GSy, A!a74Ser, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGIn, Glnl08Leu and Gly54D.

Aspect E-76: Multivalent polypeptide according to aspect E-74, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ. ID NO: 5, in which one or more {such as two, three, four, five, six, seven or eight amino acid residues have been mutated selected from the following: Serl9R, !ie20Leu, Ala74Ser, Gly78Leu, AiaSBArg, Asp85Giu, Argl05Gin and GlyS4D.

Aspect E-77: Multivalent polypeptide according to aspect E-74, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Giy78Leu, AiaSBArg, AspSSGiu, ArglOSGln and Gly54D.

Aspect E-78; Multivalent polypeptide according to aspect E-77, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: S, in which following amino acid residues have been mutated: Giy78leu, AlaSBArg, AspSSGiu, Argl05G!n and Gly54D.

Aspect E-79: Multivalent polypeptide comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more {such as two, three or four) amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, lie20Leu and GlnlOSLeu.

Aspect E-SO: Multivalent polypeptide comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Ala83Arg, Asp85G!u, ArglOSGln and Glnl08Leu.

Aspect E-81: Multivalent polypeptide according to aspect E-74, comprising or essentially consisting of at least three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid residues have been mutated: - VaISLeu, Atal4Pro, Giu44Gly, Giy78Leu, Ala83Arg, AspSSGiu, ArglOSGln and GlnlOSLeu; - AlaS3Arg, AspSSGiu, ArglOSGln and GlnlOSLeu; 6ly78Leu, Aia83Arg, Asp85Glu and Argl05Gln;

ValBLeu, A!al4Pro, Giu44Gly, Giy78Leu, Aia83Arg, AspSBGiu, ArglOBGIn, Glnl08Leu and Gly54Asp;

Ala83Arg, Asp85Glu, ArglOBGIn, GlrtlOSLeu and Gly54Asp;

Gly78Leu, AiaS3Arg, Asp85Glu, ArglOBGIn and Giy54Asp;

Giy54Asp;

Alal4Pro, Serl9Arg, ile20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, lle2GLeu, Glnl08Leu and AiaSBArg;

Aial4Pro, Serl9Arg, lte20Leu, Glni08Leu and AspSBGiu;

Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu and ArglOBGIn;

Alal4Pro, Serl9Arg, lle20Leu, 6lnl08leu, AiaE3Arg and AspSBGiu;

Alal4Pro, Serl9Arg, ISe20Leu, GlnlOSLeu, Ala83Arg and ArglOBGIn;

Alal4Pro, Serl9Arg; He20Leu, GlnlOSLeu, AspSBGiu and ArglOBGIn; or Alal4Pro, Serl9Arg, iie20Leu, GlnlOSLeu, A!aS3Arg, Asp85Giu and ArglOBGIn.

Aspect E-S2: Multivalent polypeptide according to any of aspects E-7 to £-9, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® chosen from the following: a) SEQ ID NO's: 138-141 and 154-IS?; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: ±38-141, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering}; and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

Aspect E-83: Multivalent polypeptide according to aspect E-S2, that comprises or essentially consists of at least one amino acid sequence and/or Nanobody® chosen from one of SEQ ID NO's: 138-141 and 154-157.

Aspect E-84: Multivalent poiypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-85: Multivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 62, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-S6: Multivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: S5, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-S7: Multivalent poiypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-88: Multivalent poiypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 75, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-89: Multivalent poiypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 147, in which the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-90: Multivaient polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 149, in which the Giutamic acid at oosition 1 has been changed into Aspartic acid.

Aspect E-91: Multivaient polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody* with SEQ ID NO: 15S, in which the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-92: Multivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: ValSLeu, Aiaj.4Pro, SerlSR, He20Leu, Glu44Gty, Ala74Ser, Gly7SLeu, Ala83Arg, AspBSGiu, ArglOSGln, GinlOSLeu and 6iy54Asp, and wherein the Glutamic add at position 1 has been changed into Aspartic acid.

Aspect E-9S: Multivalent polypeptide according to aspect E-92, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody®’ with SEQ ID NO: 5, in which following amino acid residues have been mutated: VaISLeu, Aial4Pro, Serl9R, He20Leu, Giu44Gly, Aia74Ser, Gly78Leu, A!aS3Arg, AspBSGiu, Argl05Gin.. GinlOSLeu and GlyS4D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-94: Multivalent polypeptide according to aspect E-92, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody14 with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino add residues have been mutated selected from the following: Serl9R, !le20leu, A!a74Ser,

Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGin and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-95: Multivalent polypeptide according to aspect E-92, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody* with SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Giy78leu, AlaSSArg, AspSSGlu, ArglOSGin and Gly54D, and wherein the Glutamic add at position 1 has been changed into Aspartic acid.

Aspect E-96: Multivalent polypeptide according to aspect E-95, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody6 with SEQ ID NO: 5, in which following amino acid residues have been mutated: Giy78Leu, Ala83Arg, Asp85Glu, ArglOSGin and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-97: Multivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more (such as two, three or four) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu and Ginl08Leu, and wherein the Giutamic acid at position 1 has been changed into Aspartic acid.

Aspect E-98: Multivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody0 with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven} amino add residues have been mutated selected from the following: A!al4Pro, Serl9Arg, lle20Leu, AlaSBArg, AspSSGIu, ArglGSGIn and GinlOSLeu, and wherein the Glutamic acid at position i has been changed into Aspartic acid.

Aspect t-99: Multivalent polypeptide according to aspect E-92, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which following amino add residues have been mutated:

GiulAsp;

GluIAsp, Val5Leu, A!al4Pro, Giu44Giy, Giy78Leu, A!aS3Arg, AspSSGIu,

ArglOSGin and GlnlOSLeu;

GluIAsp, AlaSBArg, AspSSGIu, Argl05Gln and GlnlOSleu;

GiulAsp, Giy78Leu, A!a83Arg, AspS5Glu and ArglOSGin;

GluIAsp. VaiSLeu, Aial4Pro, Giu44Gly, G!v78Leu, AiaSBArg, AspSSGIu, ArglOSGin, Glnl08Leu and GtyS4Asp;

GiulAsp, AiaSBArg, Asp85GSu, ArglOSGin, Glnl08Leu and Giy54Asp;

GiulAsp, Gly7SLeu, AlaS3Arg, AspSSGIu, Argl05Gin and Giy54Asp;

GiulAsp and Gly54Asp;

GiulAsp, Atal4Pro, Serl9Arg, !ie20Leu and GlnlOSleu;

GiulAsp, Aial4Pro, Serl9Arg, lie20Leu, GinlOSLeu and Ais83Arg;

GiulAsp, Aial4Pro, Serl9Arg, lle20Leu, GinlOSLeu and AspSSGIu ;

GiulAsp, Alal4Pro, Serl9Arg, Ile20leu, GinlOSLeu and ArglOSGin; - GiulAsp, Aial4Prc, Serl9Arg, lle20Leu, GinlOSLeu, Ala83Arg and AspSSGIu; GiulAsp, Alal4Pro, SerlSArg, lie20Leu, GinlOSLeu, Ala83Arg, ArglOSGin; GiulAsp, Alal4Pro, SerlSArg, !ie20Leu, GinlOSLeu, Asp85Glu and ArglOSGin; or GiulAsp, Alal4Pro, Serl9Arg, ile20Leu, GinlOSLeu, Aia83Arg, Asp85Giu and ArglOSGin.

Aspect E-1Q0: Bivalent polypeptide according to aspect E-7, that comprises or essentially consists of two amino acid sequences according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 and/or Nanobodies* according to any of aspects B-i to B-18, D-i to D-38 and X-x to X-38.

Aspect E-101: Bivalent polypeptide according to aspect E-100, wherein said two amino acid sequences and/or Nanobodies® are identical.

Aspect ΕΊ02: Bivalent poivpeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least a stretch or amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEC. ID NO: 102, provided that: i} said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and iij the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference.

Aspect E-103; Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with SEQ ID NO: 102, provided that: i) said stretch of amino add residues has an Aspartic add (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one stretch is chosen from: c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV' with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; e} SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no mare than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino add residues binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a) and b) should always be present in the amino acid sequence of the invention and such that the second stretch of amino acid residues is chosen from one of c), d), e) and f).

Aspect €-104: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino add residues chosen from the following: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferabty no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference; a second stretch of amino acid residues chosen from the group consisting of: c) SEQ ID NO: 102; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Rabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and a third stretch of amino add residues chosen from the group consisting of: e) SEQ ID NO: 121; f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferabty no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-10S: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least SEQ iD NO: 102.

Aspect E-106: Bivalent poiypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from: a) SEQ ID NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-107: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and a CDR1 sequence chosen from: a) SEQ ID NO: 98; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than i amino acid difference with SEQ ID NO: 98, provided that the amino add sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface pissmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and a CDR3 sequence chosen from: c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ. ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/orthe amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-10S: Bivaient polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

Aspect E-109: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

Aspect E-110: Bivalent polypeptide according to any of aspect E-102 to E-109, wherein said at least two amino acid sequences and/or Nanobodies® are identical.

Aspecl E-lll: Bivalent polypeptide according to any or aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 50-75; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 50-76, provided that i) the amino add sequence has a Glutamine join, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-112: Bivalent polypeptide according to aspect E-lll, wherein said two amino add sequences and/or Nanobodies® are identical.

Aspect £-113: Bivalent polypeptide according to aspect E-112, that comprises or essentially consists of two identical amino acid sequences and/or Nanobodies'” cbosen from one of SEQ ID NO's: 60-75.

Aspect E-114: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies'’·’ chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q} at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-13.5: Bivalent poiypeptide according to aspect E-II4, comprising or essentially consisting of two amino add sequences and/or Nanobodies®' chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68,7S and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67, 68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ti) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by suiface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-116: Bivalent poiypeptide according to any of aspects E-114 or E-115, wherein said two amino acid sequences and/or Nanobodies® are identical.

Aspect E-117: Bivalent poiypeptide according to aspect E-116, that comprises or essentially consists of two identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

Aspect £-118: Bivalent poiypeptide according to any of aspects E-100 or £-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-I19: Bivalent poiypeptide according to aspect E-11S, comprising or essentially consisting of two amino acid sequences and/or Nanobodies6, chosen from tne following: a) SEQ. ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino add sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

Aspect E-120: Bivalent polypeptide according to any of aspects E-11S or Ε-1Ί9, wherein said two amino acid sequences and/or Nanobodiess are identical,

Aspect E-121: Bivalent polypeptide according to aspect E-120, that comprises or essentially consists of two identical amino acid sequences and/or Nanobodies* chosen from SEQ ID NO's: 65 and 76.

Aspect E-222: Bivalent poiypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-153, provided that: ij the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 10S (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface Qlasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-123: Bivalent polypeptide according to aspect E-122, wherein said two amino acid sequences and/or Nanobodies® are identical.

Aspect E-124: Bivalent poiypeptide according to aspect E-123, that comprises or essentially consists of two identical amino acid sequences and/or Nanobodies®· chosen from one of SEQ ID NO's: 146-153.

Aspect E-125: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® chosen from the following; a) SEQ ID NO's; 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 146-149 and 151-153, provided that: i) the amino acid sequence has a ProSine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same. or δ higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-126: Bivalent polypeptide according to aspect E-125, comprising or essentially consisting of two amino acid sequences and/or Nanobodies®' chosen from the following: a) SEQ ID NO's: 145-149 and 151-153; bj amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine {Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine {Leu, L) at position 108 and in addition Arginine (Arg, R) at position S3, Glutamic acid {Giu, E) at position 85 and/or Glutamine {Gin, (¾ at position 105 so that when the amino acid sequence h2s no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with:

StQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; SEQ SD NO: 14S, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 14S, the amino acid sequence preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, Ej at position 85 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position S3; SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85; SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference.

Aspect E-127: Bivalent polypeptide according to any of aspects E-125 or E-126, wherein said two amino acid sequences and/or Nanobodies® are identical.

Aspect E-12S: Bivalent polypeptide according to aspect E-127, that comprises or essentially consists of two identical amino acid sequences and/or Nanobodies* chosen from one of SEQ ID NO's: 62, 65, 57, 68, 75, 76,147,149 and 153.

Asoect E-129: Bivalent polypeptide comprising or essentially consisting of two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Va!5Leu, Alal4Prc, Serl9R, lle20Leu, 6iu44Giy, Ala74Ser, Gly78leu, AiaBSArg, Asp85Giu, ArglGSGin, GlnlOBLeu and Giy54Asp.

Aspect E-130: Bivalent polypeptide according to aspect E-129, comprising or essentially consisting of two amino acid sequences and/or Nanobodies* with SEQ ID NO: 5, in which foiiowing amino acid residues have been mutated: VaiBLeu, Alal4Pro, 5erl9R, Ile20leu, Giu44Giy, Aia74Ser, Gly78i_eu, AiaBSArg, Asp85Giu, ArglGSGin, GinlOSLeu and G!y54D.

Aspect E-131: Bivalent polypeptide according to aspect E-129, comprising or essentially consisting of two amino acid sequences and/or Nanobodtes® with SEQ ID NO: 5, in which one or more (two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the foiiowing: Serl9R, lte20Leu, Ala74Ser, Gly7SLeu,

AlaSBArg, Asp85Glu, ArglGSGin and GSy54D.

Aspect E-132: Bivalent polypeptide according to aspect E-129, comprising or essentially consisting of two amino acid sequences and/or Nanobodies* with SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino add residues have been mutated selected from the following: Glv78Leu, AlaSBArg, AspSSGIu, ArglOSGin and Gly54D.

Aspect E-133: Bivalent polypeptide according to aspect E-132, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, AiaSSArg, AspSSGiu, ArglOSGln and Gly54D.

Aspect ΕΊ34: Bivalent polypeptide comprising or essentially consisting of two amino acid sequences and/or Nanobodies®' with SEQ ID NO: 3, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: ASal4Pro, SerlSArg, lle20Leu and GlnlOSLeu.

Aspect E-135: Bivalent polypeptide comprising or essentially consisting of two amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Aial4Pro, Serl9Arg, !!e20Leu, Aia83Arg, AspS5Giu, ArglG5Gln and GlnlOSLeu.

Aspect E-136: Bivalent polypeptide according to aspect E-129, comprising or essentially consisting of two amino acid sequences and/or Nanobodies® with SEQ ID NG: 5, in which following amino acid residues have been mutated: - VaISLeu, Aia!4Pro, Glu44Gly, Gly78Leu, AiaS3Arg, AspBSGiu, Argl05Gin and GlnlOSLeu;

AtaSBArg, AspSSGiu, ArglOSGln and Glnl08Leu:

Giy7SLeu, AlaSSArg, Asp85Glu and Argl05Gln; - VaISLeu, Alal4Pro, GluMGly, 6iy78Leu, Ala83Arg, Asp85Giu, Argl05Gtn, G!nl08Leu and Gly54Asp;

Aia83Arg, Asp85Giu, Argl05Gin, Glnl08Leu and Gly54Asp; - Gly78Leu, Aia83Arg, Asp85Giu, Argl05Gln and Gly54Asp;

GiyS4Asp;

Aial4Pro, Serl9Arg, lie20Leu and Glnl08Leu;

AlalAPro, Serl9Arg, lle20Leu, Ginl08Leu and Ala83Arg; - Aial4Pro, Serl9Arg, lle20Leu, Glnl08Leu and AspSSGiu;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu and ArglOSGln; - Alal4Pro, Serl9Arg, lie20Leu, Glnl08Leu, Ala83Arg and Asp85Glu; - Atal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AiaSBArg and Argl05Gin;

Aial4Prc, Serl9Arg, lie20Leu, GlnlOBLeu, AspSSGiu and ArglQ5Gin; or Alal4Prc, Serl9Arg, ile20Leu, Ginl08Leu, Aia83Arg, AspSSGiu and ArglOSGln.

Aspect E-137: Bivalent polypeptide according to any of aspects E-100 or E-101, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® chosen from the following: a} SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 138-141 and 154-157, provided that: i) the amino add sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and tl) the amino acid sequence binds protein E of hRSV with the same, about the same, ora higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-13S: Bivalent polypeptide according to aspect E-137, that comprises or essentially consists of at (east one amino add sequence and/or Nanobody* chosen from one of SEQ ID NO's: 138-141 and 154-157.

Aspect £-139: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody1® with SEQ ID NO: S, in which the Glutamic acid at position 1 is changed into Aspartic add.

Aspect E-140: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO; $2, in which the Glutamic acid at position 1 is changed into Aspartic add.

Aspect E-141: Bivalent polypeptide comprising or essentialiy consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 65, in which the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-142: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 76, in which the Glutamic add at position 1 is changed into Aspartic acid.

Aspect E-143: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ. ID NO: 75, in which the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-144: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 147, in which the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect £-145: Bivaient polypeptide comprising or essentially consisting of at least one amino add sequence and/or Nanobody^ with SEQ ID NO: 149, in which the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-146: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody®1 with SEQ ID NO: 153, in which the Giutamic acid at position 1 is changed into Aspartic acid,

Aspect E-147: Bivaient polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobodv® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven ortweive) amino add residues have been mutated selected from the following: Val5Leu, Alal4Pro, Seri9R, lie20Leu, Glu44Gly, Aia74Ser, Giy78Leu, Ala83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Gly54Asp, wherein the Giutamic acid at position 1 is changed into Aspartic acid.

Aspect E-148: Bivaient polypeptide according to aspect E-147, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which foliowing amino acid residues have been mutated: VaISLeu, Alal4Pro, Serl9R, !le20Leu, Glu44Giy, Ala74Ser, Gly78Leu, AiaSBArg, Asp85Glu, Argl05Gln, GlnlOSLeu and Gly54D, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect £-149: Bivalent polypeptide according to aspect £-147, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, lle20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGln and Gly54D, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-150: Bivalent polypeptide according to aspect E-147, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody8 with SEQ. ID NO: S, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Gty78Leu, AlaSSArg, Asp85Giu, ArglOSGln and Gly54D, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-151: Bivalent polypeptide according to aspect E-150, comprising or essentially consisting of 3t least one amino acid sequence and/or Nanobody* with SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, Ala33Arg, AspSSGlu, Argl05Gln and Gly54D, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-152: Bivalent polypeptide comprising or essentially consisting of at ieast one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, !le20Leu and Glnl08L.su, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-153: Bivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, tle20Leu, AlaS3Arg, AspS5Glu, ArglOSGln and GinlOSLeu, wherein the Glutamic acid at position 1 is changed into Aspartic acid.

Aspect E-154: Bivalent polypeptide according to aspect E-147, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ iD NO: 5, in which following amino acid residues have been mutated:

GlulAsp; - GlulAsp, VaISLeu, AiaUPro, Glu44Gly, Gly78Leu, Aia83Arg, Asp85Glu, Argl05GSn and GinlOSLeu - GlulAsp, Aia83Arg, Asp85Glu, Argl05Gln and GlnlOSLeu;

GlalAsp, Giv78L8u, AlaSBArg, AspSSGiu and ArglOSGIn;

GlulAsp, Val5Leu, AialAPro, G!u44Giy, Giv78Leu, AiaSSArg, Asp85Giu, Argl05Gln, Glnl08leu and Gly54Asp; - GiulAsp, AiaSSArg, AspSSGiu, Argl05Gln, Ginl08Leu and Giy54Asp; - GlulAsp, GSy78Leu, AiaSSArg, AspSSGiu, ArglOSGIn and Giy54Asp; - GiulAsp and Gly54Asp;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

GlulAsp, Alal4Pro, Serl9Arg, Iie20leu, GinlOSLeu and A!a83Arg; - GlulAsp, Alal4Pro, SerI9Arg, Ile20leii, GinlOSLeu and AspS5Glu;

GlulAsp, AialAPro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGIn; - GlulAsp, Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Aia83Arg and Asp85Giu; - GlulAsp, Alal4Pro, Ssfl9Arg, lie20Leu, GinlOSLeu, Ala83Arg and ArglOSGIn; - GlulAsp, AialAPro, Serl9Arg, Iie20leu, GinlOSLeu, AspSSGiu and ArglOSGIn; or - GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, A!a83Arg, Asp85Glu and

ArglOSGIn.

Aspect E-15S: Trivalent polypeptide according to aspect E-7, that comprises or essentially consists of three amino acid sequences according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 and/or Nanobodies® according to any of aspects B-l to B-18, D-l to D-38 and X-lto X-3S.

Aspect E-156: Trivalent polypeptide according to aspect E-155, wherein said three amino acid sequences and/or Nanobodies® are identical.

Aspect E-157: Trivalent polypeptide according to any of aspects E-155 or E-155, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino add residues chosen from the following: a) SEQ ID NO; 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3,2 or 1 amino acid difference.

Aspect E-158: Trivaient polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 102; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amirio acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and at least one stretch is chosen from; c) SEQ ID NO: 98; d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino add residues has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; ε) SEQ ID NO: 121; and f) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference. such that the stretch of amino acid residues that corresponds to one of a) and b) should always be present in the amino add sequence of the invention and such that the second stretch of amino acid residues is chosen from one of cj, d), ej and f).

Aspect E-1S9: Trivaient polypeptide according to any of aspects Ε-1Ξ5 or £-156, comprising or essentially consisting of three amino acid sequences and/or NanoDodies® that comprise at least a stretch of amino acid residues chosen from the following: a) SEQ ID NO: 9B; and b) a stretch of amino add residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino add sequence comprising said stretch of amino add residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; a second stretch of amino acid residues chosen from the group consisting of: c) SEQ iD NO: 102; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising sate streten στ amino aaa residues dious protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino add sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and δ third stretch of amino acid residues chosen from the group consisting of: e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-160: Trivalent polypeptide according to any of aspects ΕΊ55 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® that comprise at least SEQ, ID NO: 102.

Aspect ΕΊ61: Trivalent polypeptide according to any of aspects E-155 or E-15S, comprising or essentially consisting of three amino acid sequences and/or Nanobodies* that comprise at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from: a) SEQ iD NO: 98; b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; c) SEQ ID NO; 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO; 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance} and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino add difference.

Aspect E-1S2: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies0 that comprises at least SEQ ID NO; 102 and a CDR1 sequence chosen from: a) SEQ ID NO: 98; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; and a CDR3 sequence chosen from: c) SEQ ID NO: 121; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference.

Aspect E-163: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102 and at least one stretch of amino acid residues (CDR sequence) chosen from SEQ. ID NO: 98 and SEO. ID NO: 121.

Aspect E-164: Trivalent polypeptide according to any of aspects E-155 or E-15S, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

Aspect E-165: Trivalent polypeptide according to any of aspect E-157 to E-164, wherein said at feast three amino acid sequences and/or Nanobodies® are identical.

Aspect E-156: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabst numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

Aspect E-167: Trivalent polypeptide according to aspect E-166, wherein said three amino acid sequences and/or Nanobodies® are identical.

Aspect E-168: Trivalent polypeptide according to aspect E-157, that comprises or essentially consists of three identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

Aspect E-169: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the following: a} SEQ ID NO's: 62, 65, 67, 68,75 and 76: b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance} and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-170: Trivalent polypeptide according to aspect E-169, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 62, 65,67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 62, 65, 67, 68,75 and 76, provided that; i} the amino add sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-171: Trivalent polypeptide according to any of aspects E-16S or E-170, wherein said three amino acid sequences and/or Nanobodies® are identical.

Aspect E-172: Trivaient polypeptide according to aspect E-171, that comprises or essentially consists of three identical amino acid sequences and/or Nanobodies* chosen from one of SEQ ID NO's: 62, 65, 67,68,75 and 76.

Aspect E-173: Trivaient polypeptide according to any of aspects E-155 or ΕΊ56, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D} at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and if) the amino acid sequence binds orotein F of nRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-174: Trivaient polypeptide according to aspect E-173, comprising or essentially consisting of three amino acid sequences and/or Nanobodies®' chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and H) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/orthe amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference.

Aspect E-17S: Trivaleni polypeptide according to any of aspects E-173 or Ε-Γ74, wherein said three amino add sequences and/or Nanobodies® are identical.

Aspect E-176: Trivaient polypeptide according to aspect £-175, that comprises or essentially consists of three identical amino acid sequences and/or Nanobodies® chosen from $EO. ID NO's: 65 and 76,

Aspect E-177: Trivaient polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the fo I lowing: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 145-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position IS, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/orthe amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference.

Aspect E-178: Trivaient polypeptide according to aspect E-177, wherein said three amino acid sequences and/or Nanobodies® are identical.

Aspect E-179: Trivaient polypeptide according to aspect E-178, that comprises or essentially consists of three identical amino acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 146-153.

Aspect E-180: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of three add sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position IS, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (3s defined herein) compared to the amino acid sequence without the 3, 2 or l amino acid difference.

Aspect E-181: Trivalent polypeptide according to aspect E-180, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with: SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ iD NO: 147, the amino add sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q} at position 105; - SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85 and Giuiamine (Gin, Q) at position 105; SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, 8] at position 83, Glutamic acid {Glu, E) at position 85 and Glutamine {Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine {Arg, R) at position 83; SEQ ID NO: 152, the amino acid sequence preferably has Glutamic acid (Glu, E) at position 85; - SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg. R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3,2 or 1 amino acid difference.

Aspect E-1S2: Trivalent polypeptide according to any of aspects E-18G or E-1S1, wherein said three amino acid sequences and/or Nanobodies® are identical.

Aspect E-183; Trivalent polypeptide according to aspect E-182, that comprises or essentially consists of three identical amino add sequences and/or Nanobodies®' chosen from one Of SEQ ID NO's: 62, 65, 67, 68, 75, 76, 147,149 and 153.

Aspect E-184: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, lle20Leu, G!u44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gin, GinlOSleu and Gly54Asp.

Aspect E-185: Trivalent polypeptide according to aspect E-184, comprising or essentially consisting of three amino add sequences and/or Nanobodies® with SEQ ID NO: 5, in which following amino add residues have been mutated: Val5leu, Alal4Pro, Serl9R, lle20Leu, Giu44Gly, A!a?4Ser, Giy78Leu, AtaSBArg, AspSSGiu, ArglOSGln, GlnlQ8Leu and Gly54D.

Aspect E-186: Trivaient polypeptide according to aspect £-184, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: 5erl9R, lle20Leu, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGiu, Argl05Gin and Giy54D.

Aspect E-1.87: Trivaient polypeptide according to aspect E-184, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: G!y78leu, Ala83Arg, AspSSGiu, ArglOSGln and Giy54D.

Aspect E-188: Trivaient polypeptide according to aspect E-187, comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ. ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGln and Gly54D.

Aspect E-189: Trivaient polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, SerlSArg, lle20Leu and Glnl08Leu.

Aspect E-190: Trivaient polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQSD NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, Ala83Arg, AspSSGiu, Argl05Gin and Glnl08Leu.

Aspect E-191; Trivaient polypeptide according to aspect E-184, comprising or essentially consisting of three amino acid sequences and/or Nanobodies6 with SEQ ID NO: 5, in which following amino acid residues have been mutated: - ValSLeu, Alal4Pro, Glu44Gly, Gly78Leu, Ala83Arg, AspSSGIu, Argl05Gln and Glnl08Leu;

AlaS3Arg, Asp85Glu, Argl05Gln and GlnlOSLeu; G!y78Leu, Aia83Arg, AspS5G!u and ArglOSGln; - VaISLeu, Aial4Pro, Glu44Giy, Gly78Leur Ala83Arg, AspSSGIu, ArglOSGln, Glnl08Leu and Gly54Asp; - AlaS3Arg, AspSSGIu, ArglOSGln, GlnlOSLeu and Gly54Asp; - Gly78Leu, AlaS3Arg, Asp85Glu, ArglOSGln and GlyS4Asp; - Gly54Asp;

Aial4Pro, SerlSArg, lle20Leu and GlnlOSLeu;

Alal4Pro, SarlSArg, Ha20Leu, GlnlOSLeu and AlsSSArg;

Alal4Pro, SerlSArg, !le20Leu, GlnlOSLeu and AspSSGIu;

Alal4Pro, Serl9Arg, !le20Leu, Glnl08Leu and ArglOSGln; - Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, AlaSSArg and Asp85Glu; - Alal4Pro, SerlSArg, lie20Leu, GlnlOSLeu, AiaS3Arg and Argl05Gln; - Aial4Pro, Serl9Arg, !le20Leu, GlnlOSLeu, AspSSGIu and Argl05Gln; or Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Ala83Arg, AspSSGIu and ArglOSGln.

Aspect E-192: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies®’ with SEQ ID NO: 62.

Aspect E-193: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies3 with SEQ ID NO: 65.

Aspect E-194: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 76.

Aspect ΕΊ95: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies* with SEQ ID NO: 75.

Aspect E-196: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 147.

Aspect E-197: Trivaient polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 14S.

Aspect E-198: Trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies® with SEQ ID NO: 153.

Aspect E-199: Trivalent polypeptide according to any of aspects E-155 or E-156, comprising or essentially consisting of at ieast one amino acid sequence and/or Nanobodv® chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NG's: 138-141 and 154-157, provided that: ij the amino acid sequence has a Aspartic acid (Asp, D) at position 1 (said position determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

Aspect E-200: Trivalent polypeptide according to aspect E-199, that comprises or essentially consists of at least one amino acid sequence and/or Nanobody® chosen from one of SEQ ID NO's: 138-141 and 154-157.

Aspect E-2G1: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-202: Trivalent polypeptide comprising or essentially consisting of at ieast one amino add sequence and/or Nanobody® with SEQ ID NO: 62, in which the Giutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-203: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody4 with SEQ ID NO; 65, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-204: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 76, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect Ξ-205: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 75, in which the Glutamic acid at position X as been changed into Aspartic acid.

Aspect E-206; Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 147, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-207: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 149, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-208: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ !D NO: 153, in which the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E*20S: Trivalent polypeptide comprising or essentially consisting of at least one amino acid sequence and/or Nanobody* with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Alal4Pro, Serl9R, lle20Leu, Giu44Gly, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Giy54Asp, and wherein the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-210: Trivalent polypeptide according to aspect E-209, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, In which following amino acid residues have been mutated: Val5Leu, Alal4Pro, Serl9R, lie20Leu, Glu44Giy, Ala74Ser, Giy78Leu, AlaSBArg, AspSSGlu, Argl05Gin, GinlOSLeu and Gly54D, and wherein the Glutamic acid at position I as been changed into Aspartic acid.

Aspect E-211; Trivalent polypeptide according to aspect E-209, comprising or essentially consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more {such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, lie20Leu, Aia74Ser,

Giy78Leu, A!a83Arg, AspSSGlu, ArglOSGln and Gly54D, and wherein the Glutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-212: Trivalent polypeptide according to aspect E-209, comprising or essentialiy consisting of at ieast one amino acid sequence and/or Nanobody* with SEQ ID NO: 5, in which one or more {such as two, three, four or five) amino acid residues have been mutated selected from the following: Gly7SLeu, AlaSBArg, Asp85Glu, ArglOSGln and GiyS4D, and wherein the Giutamic acid at position 2 as been changed into Aspartic acid.

Aspect £-213: Trivalent polypeptide according to aspect E-212, comprising or essentialiy consisting of at least one amino acid sequence and/or Nanobody® with SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, Ala83Arg, AspSSGlu, ArglOSGln and GlyS4D, and wherein the 6lutamic acid at position 1 as been changed into Aspartic acid.

Aspect E-214: Trivalent polypeptide according to aspect E-209, comprising or essentialiy consisting of at ieast one amino acid sequence and/or Nanobodv& with SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GiulAsp, Val5Leu, Alal4Pro, Giu44Giy, G!y78Leu, AlaSBArg, Asp85Giu,

Argl056in and GinlOSLeu;

GlulAsp, Ala83Arg, Asp85Glu, ArglOSGln and GinlOSLeu;

GlulAsp, Gty78Leu, AlaS3Arg, Asp85Glu and Argl05Gln;

GiulAsp, VaISLeu, A!al4Pro, Glu44Gly, Gly78Leu, AlaS3Arg, AspSSGlu,

Argl05Gln, GinlOSLeu and Gly54Asp;

GlulAsp, Ala83Arg, Asp85G)u, ArglOSGln, GinlOSLeu and Gly54Asp;

GlulAsp, Giy78Leu, AlaSSArg, Asp85Glu, ArglOSGIn and Giy54Asp;

GlulAsp and Giy54Asp;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu;

GlulAsp, Alal4Pro, SerlSArg, IIe20Leu, GlnlOSLeu and AlaSSArg;

GlulAsp, A!al4Pro, Serl9Arg, Sle20Leu, GlnlOSLeu and AspSSGIu;

GlulAsp, Aial4Pro, Serl9Arg, lle20Leii, GlnlOSLeu and Argl05Gln;

GlulAsp, Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu, AiaBBArg and AspSSGIu; - GlulAsp, Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu, AlaSSArg and Argl05Gin; - GlulAsp., Ala!.4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, AspSSGIu and Argl05G‘m; or GlulAsp, Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu, AlaSSArg, AspSSGIu and Argl05Gln.

Aspect E-215: Trivalent polypeptide that is directed against and/or specifically binds protein F of hRSV, chosen from the following polypeptides: a) SEa ID NO's: 77-79 and 158; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 77-79 and 158, provided that: i) the amino acid sequences or Nanoboaies® encompassed in said polypeptide have a Glutamine (Gin, 0,} at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position S3 and/or a Glutamic add (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii} the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance} and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino add difference,

Aspect E-216: Trivalent polypeptide according to aspect E-215, chosen from the following polypeptides: a) SEQ ID NO's: 77-79 and 158; b) polypeptides that have no more than 3, preferably no more than 2. more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 77-79 and 158, provided that: Π the amine acid sequence or Nanobody*' encompassed in said polypeptide has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and a Glutamic acid (Giu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Aspect E-217: Trivalent polypeptide that is directed against and/or specifically binds protein F of hRSV, chosen from the following polypeptides: a) SEQ ID NO: 78 and 79; b) polypeptides that have no more than 3, preferably no mors than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 7S and 79, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at Dosition 83 and/or a Glutamic acid (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as denned herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Aspect E-218: Trivalent polypeptide according to aspect E-217, chosen from the following polypeptides: a) SEQ ID NO: 78 and 79; or b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 78 and 79, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78, an Arginine (Arg, R) at position S3 and a Glutamic add (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino add difference.

Aspect E-219: Trivaient polypeptide that is directed against and/or specifically binds protein r of hRSV, chosen from the following polypeptides: 3) SEQ ID NO's: 159*161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 159-161, provided that: i) the amino add sequence or Nanobody6 encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3,2 or 1 amino acid difference.

Aspect E-220: Trivaient polypeptide according to aspect E-219, chosen from the following polypeptides: a) SEQ ID NO's: 159-161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 159-161, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic add (Glu, E) at position 85 and/or

Glutamine {Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Aspect E-221: Trivaient poiypeptide according to any of aspects E-219 or E-220, chosen from the following polypeptides: a) SEQ ID NO's: 159-161; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NOV. 155-161, provided that: i) the amino acid sequence or Nanobody® encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic add (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the polypeptide has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ ID NO: 159, the amino acid sequence or Nanobody6, encompassed in said polypeptide preferably has Arginine (Arg, R) at position 83 and Giutamine (Gin, Q) at position 105; SEQ ID NO: 160, the amino acid sequence or Nanobody® encompassed in said poiypeptide preferably has Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and Glutamine (Gin, Q) at position 10S; - SEQ ID NO: 161, the amino acid sequence or Nanobody® encompassed in said poiypeptide preferably has Arginine (Arg, R) at position 83 and Glutamic add (Giu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Aspect E-222: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, AialAPro, Serl9R, !!e20Leu, Glu44G!y, Ala74Ser, Giv78Leu, AlaSsArg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Gly54Asp.

Aspect E-223: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ali three) NanobodyVNanobodies® that form(s) part of SEQ ID NO: 53, following amino 3cio residues have been mutated: VaISLeu, AialAPro, Serl9R, lle20Leu, Giu44Giy, Ala74Ser, Giy78Leu, Ala83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and 6ly54D.

Aspect E-224: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody®/Nanobodles® that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six, seven or sight) amino acid residues have been mutated selected from the following: SerlSR, lle20Leu, A!a74Ser, Gly78Leu, Ala83Arg, AspSSGIu, Argl05Gln and Gly54D.

Aspect E-225: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody®/Nanobodies® thatform(s) part of SEQ ID NO: 53, one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu, ArglOSGIn and Gly54D.

Aspect E-226: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in alt three) Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, following amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Giu, Argl05Gln and Gty54D.

Aspect E-227: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ali three) l\lanohodys/Nanobodiese' that form(s) part of SEQ ID NO: 53, one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lie20Leu and GlnlOSLeu.

Aspect E-228: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ail three) Nanobody*/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, )le20Leu, AiaSBArg, AspS5Giu, ArglOSGIn and GlnlOSLeu,

Aspect £-229: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO; 53, in which in at least one (preferably in two, more preferably in ali three) Nsnobody^/Nanobodles® that form(s) part of SEQ ID NO: 53, following amine acid residues have been mutated: - VaISLeu, Ala!4Pro, Glu44Giy, Gly78Leu, AlaS3Arg, AspSSGIu, ArglOSGIn and GlnlOSLeu;

Ala83Arg, AspSSGiu, Argl05Gln and GlnlOSLeu; - Gly78Leu, Ala83Arg, AspSSGiu and Argl05Gln; - VaISLeu, Alal4Pro, Glu44Gly, Gly78Leu, Aia83Arg, AspSSGiu, Argl05G'm, GlnlOSLeu and Gly54Asp; - Ala83Arg, AspSSGiu, ArglOSGIn, GlnlOSLeu and Gly54Asp; - Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGIn and Gly54Asp;

Gly54Asp;

Aial4Pro, SerlSArg, He20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, lle20leu, GlnlOSLeu and AlaS3Arg; - Alal4Pro, Serl9Arg, Ile20leu, GlnlOSLeu and Asp85Glu;

Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and Argl05Gln; - Alal4Pro, Serl9Arg, lie20Leu, Glnl08Leu, Ala83Arg and Asp85Glu; - Alal4Pro, Serl9Arg, !le20Leu, Glnl08Leu, Ala83Arg and ArglOSGIn;

Alal4Pro, SerlSArg, lle20Leu, Ginl08Leu, Asp85Glu and Argl05Gtn; or - Aial4Pro, Serl9Arg, Ile20leu, Glnl08Leu, Ala83Arg, AspSSGiu and ArglOSGIn.

Aspect £-230: Trivalent polypeptide comprising or essentially consist of SEQ ID NO: 77.

Aspect E-231: Trivalent polypeptide comprising or essentially consist of SEQ ID NO: 78.

Aspect E-232: Trivalent polypeptide comprising or essentially consist of SEQ ID NO: 79.

Aspect E-233: Trivalent polypeptide comprising or essentially consist of one of SEQ ID NO’s: 159-151.

Aspect E-234: Trivalent polypeptide that is directed against and/or specifically binds protein F of hRSV, chosen from the following polypeptides: a) SEQ ID NO's: 142-145 and 162-155; h} polypeptides that have no more than 3, preferably no more tnar, 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 142-145 and 152-165, provided that: i) the first amino acid sequence or Nanobody® encompassed in said polypeptide has an Aspartic acid (Asp, D) at position 1; and ii} the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, ora higher potency (as defined herein) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

Aspect E-235: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which the first Glutamic acid has been changed into Aspartic acid.

Aspect E-236: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 77, in which the first Glutamic acid has been changed into Aspartic acid.

Aspect E-237: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 78, in which the first Giutamic acid has been changed into Aspartic acid.

Aspect E-238: Trivalent polypeptide comprising or essentially consisting of 5EQ ID NO: 79, in which the first Glutamic acid has been changed into Aspartic acid.

Aspect E-239: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 158, in which the first Giutamic acid has been changed into Aspartic acid.

Aspect E-240: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 159, in which the first Glutamic acid has been changed into Aspartic acid.

Aspect E-241: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 160, in which tne first Glutamic acid has been changed into Aspartic acid.

Aspect E-242: Trivalent polypeptide comprising or essentially consisting of SEQ (D NO: 161, in which the first Giutamic acid has been changed into Aspartic acid.

Aspect E-243: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably iri si! three) Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or mors (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: ValSleu, Aial4Pro, Ssrl9R, ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, AiaSBArg, Asp85Glu, ArglOSGin, GlnlOSLeu and Giy54A$p, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-244: Trivalent polypeptide comprising or essentially consisting of SEQ !D NO: 53, in which in at least one (preferably in two, more preferably in ait three} Nanobobya/NartobodiesB that form(s) part of SEQ ID NO: 53, following amino acid residues have been mutated: VaiSLeu, Alal4Pro, Serl9R, He20Leu, Glu44Giy, Aia74Ser, Gly78Leu, Ala83Arg, AspSSGlu, ArglOSGIn, GlnlOSLeu and Giy54D, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect £-245: Trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at ieast one (preferably in two, more preferably in ail three) Nanobody®/Nanobodies!S that form{s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,

Asp85Glu, ArglOSGin and Gly54D, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-246: Trivaient polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) NanobodyVNanobodies* that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGIn and Gly54D, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-247: Trivaient polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanabody®/Nanobodies® that form(s) part of SEQ ID NO: 53, following ammo acid residues have been mutated: Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGin and 6iy54D, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-248: Trivaient polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody'VNanobodies2 that form(s) part of SEQ ID NO: 53, one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Atsl4Pro, SerlSArg, Iie20leu and GlnlOSLeu, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-249: Trivaient poiypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) NanobodyVNanobodies® that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lie20Leu, Ala83Arg, AspSSGIu, ArglQ5Gin and Glnl08Leu, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-250: Trivaient polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in ai! three) Nanobody®/Nanobodies® thatform(s) part of SEQ ID NO: 53, following amino acid residues have been mutated: - VatSLeu, Alai4Pro, Gtu44Giy, Giy78Leu, Ata83Arg, AspSSGiu, Argl05Gin and GlnlOSLeu; - Ala83Arg, AspSSGiu, ArglOSGin and Glnl08Leu; - Giy78Leu, Aia83Arg, Asp85Glu and ArglOSGin; - Val5Leu, Alal4Pro, Glu44Glv, Gly78Leu, Ala83Arg, Asp85Glu, Argl05Gln, GiniOSleu and Gly54Asp;

AlaSBArg, Asp85Glu, ArglOSGin, GlnlOSLeu and Gly54Asp; GIy78Leu, Ala83Arg, Asp85Glu. Argl05G!n and Gly54Asp;

Gly54A.sp;

Alal4Pro, Serl9Arg, ile20Leu and GlnlOSLeu; - Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu and Ala83Arg;

Aiai4Pro, Serl9Arg, tie20Leu, Glnl08Leu and AspSSGiu;

Alal4Pro, Ser!9Arg. lle20Leu, GlnlOSLeu, ArglOSGin; - Alal4Pro, Serl9Arg. Ile20Leu, GlnlOSLeu, AlaSBArg and AspS5Glu;

Alal4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, Ala83Arg and ArglOSGin;

Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, Asp85Glu and Argl05G!n; or - Aial4Pro, Serl9Arg, lie20Leu, GlnlOSLeu, Ala83Arg, AspSSGiu and ArglOSGin, and wherein the first Glutamic acid has been changed into Aspartic acid.

Aspect E-251: Trivalent polypeptide comprising or essentially consist of SEQ ID NO: 142.

Aspect E-252: Trivalent polypeptide comprising or essentially consist of SEO. ID NO: 143.

Aspect E-253: Trivalent polypeptide comprising or essentially consist of SEQ ID NO: 144.

Aspect E-254: Trivalent polypeptide comprising or essentially consist of SEO ID NO: 145.

Aspect E-255: Trivalent polypeptide comprising or essentially consist of one of SEQ ID NO's: 162-165

Aspect E-256: Polypeptide according to any of aspects E-l to E-255, that can specifically bind to protein F of hRSV with a dissociation constant (KD) of 100 nM to 0.1 nM or less, preferably 10 nM to 0.1 nM or less, more preferably 1 nM to 0.1 nM or less.

Aspect E-257: Polypeptide according to any of aspects E-I to E-256, that can specifically bind to protein F of hRSV with a kon-rate of between 104 M'V1 to about 107 wrV:, preferably between 10s M'V1 and 10' Μ’Υ1, more preferably about 106 M'V: or more.

Aspect E-258: Polypeptide according to any of aspects E-l to E-257, that can specifically bind to protein F of hRSV with a k9ft rate between 10V s'- (ti/j=0.S9 s) and 10-4 s'J (providing a near irreversible complex with a ti/2 of multiple days), preferably between 1G'3 s'* and 10'4 s'1, more preferably between 5xl0-i s’' and ID'4 s'-, or lower.

Aspect E-259: Polypeptide y according to any of aspects E-l to E-258, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6) with an IC5C value between 10 pM and 1000 pM, preferably between 10 pM and 250 pM, more preferably between 50 pM and 200 pM or less.

Aspect E-260: Polypeptide according to any of aspects E-l to E-259, that can neutralize hRSV (for example, as measured in a microneutralization assay on hRSV Long (such as e.g. described in Example 6} with an IC50 value that is at least the same and preferably better, at ieast ten times better, preferably twenty times better, more preferably fifty times better, even more preferably sixty, seventy, eighty or more times better compared to the (C50 value obtained with Synagfs®.

Aspect E-261: Polypeptide according to any of aspects E-l to E-260, which is a multispedfic construct.

Aspect F-l: Monovalent construct, comprising or essentially consisting of one amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-3S and/or one Nanobody® according to any of aspects B-l to B-18, D-i to D-38 and ΧΊ to X-38.

Aspect F-2: Monovalent construct according to aspect F-l, in which said amino acid sequence is chosen from the group consisting of domain antibodies, amino add sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino acid sequences that are suitable for use as a bAb, or Nanobodies®.

Aspect F-3: Monovalent construct, comprising or essentially consisting of one Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38.

Aspect F-4: Monovalent construct, that is chosen from the group consisting of SEQ ID NO's: 60- 76, SEQ ID NO's: 138-141 and SEQ ID NO's: 146-157.

Aspect F-5: Use ora monovalent construct according to any of aspects F-i to F-4, in preparing a multivalent polypeptide according to any of aspects E-i to E-261.

Aspect F-6: Use of a monovalent construct according to aspect F-5, wherein the monovalent construct is used as a binding domain or binding unit in preparing a multivalent construct comprising two or more binding units.

Aspect F-7: Use of a monovalent construct according to any of aspects F-5 or F-6, m preparing a multivalent polypeptide that preferably exhibits intramolecular binding compared to intermoiecular binding.

Aspect F-8: Use of a monovalent construct according to any of aspects F-5 to F-7, as a binding domain or binding unit in preparing a multivalent construct, wherein the binding domains or binding units are linked via a linker such that the multivalent polypeptide preferably exhibits intramolecular binding compared to intermoiecular binding and/or the multivalent polypeptide can simultaneously bind all binding site on protein F of hRSV.

Aspect F-9: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct is chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's; 60-76, provided that; i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabai numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-10: Use of a monovalent construct according to aspect F-9, wherein the monovalent construct essentially consists of one of SEQ ID NO's: 60-76.

Aspect F-ll; Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovaient construct is chosen from the following: a) SEQ ID NO's: 62, 65,67, 68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65, 67,68,75 and 76, provided that: i) the amino acid sequence has a Giutamine {Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or a Arginine (Arg, R) at position S3 {said positions determined according to Rabat numbering}; and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-12: Use of a monovaient construct according to aspect F-ll, wherein the monovaient construct is chosen from the following: a) SEQ !D NO's: 62, 65, 67, 68, 75 and 76; or b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Rabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein} compared to the amino acid sequence without the 3, 2 or i amino acid difference, in preparing a multivalent polypeptide.

Aspect F-13: Use of a monovalent construct according to aspect F-ll or F-12, wherein the monovalent essentially consists of one of SEQ !D NO: 62, 65, 67, 68, 75 and 76.

Aspect F-14: Use of a monovatent construct according to any of aspects F-5 to F-8, wherein the monovalent construct is chosen from the following: a) SEQ ID NO's; 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and ?S, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-15: Use of a monovaient construct according aspect F-14, wherein the monovalent construct is chosen from the following: a) SEQ ID NO';; 65 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and an Arginine (Arg, R) at position S3 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface ptasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or i amino acid difference, in preparing a multivalent polypeptide.

Aspect F-16: Use of a monovalent construct essentially consisting of SEQ ID NO: $2 in preparing a multivalent polypeptide.

Aspect F-17: Use of a monovalent construct essentially consisting of SEQ ID NO: 65 in preparing a multivalent polypeptide.

Aspect F-1S: Use of a monovalent construct essentially consisting of SEQ ID NO: 76 in preparing a multivalent polypeptide.

Aspect F-19: Use of a monovalent construct according to any of aspects F-5 to r-8, wherein the monovalent construct is chosen from the following: 3} SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine {Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and il) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference., in preparing a multivalent polypeptide.

Aspect F-20: Use of a monovalent construct according to aspect F-19, wherein the monovaient construct essentially consists of one of SEQ ID NO's: 146-153.

Aspect F-21: Use of a monovalent construct according to any of aspects F-S to F-8, wherein the monovalent construct is chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108; and in addition Arginine (Arg, R) at position 83, Glutamic acid (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-22: Use of a monovalent construct according to aspect F-21, wherein the monovalent construct is chosen from the following: a) SEQ ID NO's; 146-149 and 151-153; p) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, l) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: - SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; - SEQ ID NO: 148, the amino add sequence preferably has Glutamic acid (Glu, E} at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 149, the amino acid sequence preferably has Arginine {Arg, R) at position S3, Glutamic acid (Glu, Ξ) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; SEQ ID NO: 152, the amino acid sequence oreferabiy has Glutamic acid (Giu, E) at position 85; SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R} at position 83 and Glutamic acid (Glu, Ξ) at position 85; (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, aDOut the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher patency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-23: Use of a monovalent construct according to aspect F-21 or F-22, wherein the monovalent essentially consists of one of SEQ ID NO: 145-149 and 151-153.

Aspect F-24: Use of a monovaient construct according to any of aspects F-5 to F-S, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or tv/elve) amino acid residues have been mutated selected from the following; VaBLeu, Afal4Pro, Serl9R, lle20Leu, G!u44Gly, Als74Ser, Gly78Leu, Ala83Arg, AspSSGlu, ArglOSGIn, Gtnl08Leu and Gly54Asp, in preparing a multivalent polypeptide.

Aspect F-25: Use of a monovalent construct according to aspects F-24, wherein the monovaient construct essentially consists of SEQ ID NO; 5, in which following amino acid residues have been mutated: VaBLeu, Alal4Pro, Serl9R, Ile20leu, Glu44Gly, Ala74Ser, Gly78leu, Ala83Arg, Asp85Glu, ArglOSGIn, Glnl08Leu and Gly54D, in preparing a multivalent polypeptide.

Aspect F-26: Use of a monovalent construct according to aspects F-24, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, tle20Leu, Ala74Ser, Gly78Leu, Ala83Arg, AspSSGIu, Argl05Gln and Gly54D, in preparing a multivalent polypeptide.

Aspect F-27: Use of a monovalent construct according to aspects F-24, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: Giy78Leu, Ala83Arg, AspS56!u, ArglOSGin and 6iy54D, in preparing a multivalent polypeptide.

Aspect F'28: Use of a monovalent construct according to aspects F-27, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly78Leu, AiaSBArg, AspSSGIu, ArglOSGin and Giy54D, in preparing a multivalent polypeptide.

Aspect F-2S: Use of a monovalent construct according to any of aspects F-5 to F-S, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Aial4Pro, Sarl9Arg, lle20Leu and Glnl08Leu, in preparing a multivalent polypeptide,

Aspect F-30: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, !le20Leu, Ala83Arg, Asp85Glu, ArglOSGin and GlnlOSLeu, in preparing a multivalent polypeptide.

Aspect F-31: Use of a monovalent construct according to aspects F-24, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

Va!5Leu, Alsl4Pro, Glu44Gly, 6ly78Leu, Ala83Arg, Asp85Glu, ArglOSGin and GlnlOSLeu;

AiaSSArg, AspSSGiu, Argl05Gln and Ginl08Leu;

Gly78Leu, Aia83Arg, Asp85Glu and ArglOSGIn; - Va!5Leu, Aiai4Pro, Glu44Gly, Gly78Leu, AlaSSArg, AspSSGiu, ArglOSGIn, Glnl08Leu and Gly54Asp;

Ala83Arg, Asp85Giu, ArglOSGIn, Ginl08Leu and Gly54Asp;

Gly78Leu, A!a83Arg, Asp85Glu, ArglOSGIn and Gly54Asp; - Gly54Asp;

Alal4Pro, Serl9Arg, He20Leu and Gin 108Leu; - Alal4Pro, Serl9Arg, iie20Leu, GlnlOSLeu and Aia83Arg;

Alal4Pro, Serl9Arg, lle20Leu, Ginl08Leu and Asp85Glu;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu and ArglOSGIn;

Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu, Aia83Arg and Asp85Giu;

Alal4Pro, Serl9Arg, Ile20Leu, Glnl08Leu, A!a83Arg and ArglOSGIn;

Alal4Pro, SerlSArg, ile20Leu, Glnl08Leu, Asp85Glu and ArglOSGIn; or - Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AlaSSArg, AspSSGiu and ArglOSGIn, in preparing a multivalent polypeptide.

Aspect F-32: Use cif a monovalent construct according to any of aspects F-S to F-S, wherein the monovalent construct is chosen from the following; a) 5EQ ID NO's; 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that; i) the amino acid sequence has a Aspartic acid (Gin, Q) at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino add sequence without the 3, 2 or 1 amino acid difference, in preparing a multivalent polypeptide.

Aspect F-33: Use of a monovalent construct according to aspect F-32, wherein the monovalent construct essentially consists of one of SEQ ID NO's: 138-141 and 154-157.

Aspect F-34: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivaient polypeptide.

Aspect F-35: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ. ID NO: 62, in which the Glutamic acid at position I has been changed into Aspartic acid, in preparing ε multivaient polypeptide.

Aspect F-36: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 65, in which the Glutamic acid at position 1 has been changed into Aspartic add, in preparing a multivaient polypeptide.

Aspect F-37: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect f-38: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 75, in which the Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-39: Use of a monovalent construct according to any of aspects F-5 to F-E, wherein the monovalent construct essentially consists of SEQ ID NO: 147, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-40: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 149, in which the Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivaient polypeptide.

Aspect F-41: Use of a monovalent construct according to any of aspects F-S to F-S, wherein the monovalent construct essentially consists of SEQ ID NO: 153, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-42: Use of a monovalent construct according to any of aspects F-5 to F-S, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, AiaMPro, SerlSR, Iie20leu, Giu44Giy, A!a74Ser, Gly78Lsu, AiaSSArg, AspSSGiu, ArglOSGin, GlnlOSLeu and Giv54Asp, and wherein the Glutamic add at position 1 has been changed into Aspartic add, in preparing a multivalent polypeptide.

Aspect F-43: Use of a monovalent construct according to aspects F-42, wherein the monovaient construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: Val5Leu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGIu, Argl05GSn, GlnlOSLeu and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-44: Use of a monovaient construct according to aspects F-42, wherein the monovaient construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, l!e20Leu, Ala74Ser, 61y7SLeu, Ala83Arg, AspSSGiu, Argl05Gln and Gly54D, and wherein the Giutamicacid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-45: Use of a monovalent construct according to aspects F-42, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, or five} amino acid residues have been mutated selected from the following: Giy78Leu, Ala83Arg, Asp85Giu, ArglOSGin and Giy54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-4£: Use of a monovalent construct according to aspects F-42, wherein the monovalent-construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: Giy78Leu, AlaSBArg, AspSSGiu, ArglOSGin and Giy54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-47: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, iie20Leu and GinlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-48: Use of a monovalent construct according to any of aspects F-5 to F-8, wherein the monovalent construct essentially consistsof SEQ. ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lie20Leu, AiaS3Arg, AspSSGiu, ArglOSGin and GinlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a multivalent polypeptide.

Aspect F-49: Use of a monovalent construct according to aspects F-42, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp;

GiulAsp, ValSLeu, Alal4Pro, Gtu44Gly, Giy78leu, A!a83Arg, Asp85Giu,

ArglOSGin and GinlOSLeu;

GlulAsp, AlaSBArg, AspSSGiu, ArglOSGin and GinlOSLeu;

GlulAsp, Giy78Leu, Ata83Arg, AspSSGiu and ArglOSGin;

GlulAsp, ValSLeu, Aial4Pro, Giu44G!y, G!y78Leu, Ala83Arg, Asp85Giu,

ArglOSGin, GinlOSLeu and Giy54Asp;

GlulAsp, Aia83Arg, AspSSGiu, ArglOSGin, GinlOSLeu and Giy54Asp;

GlulAsp, Gly78Leu, Aia83Arg, Asp85Glu, ArglOSGin and Gly54Asp;

GlulAsp and Gly54Asp; - GlulAsp, Aial4Pro, Serl9Arg, l!e20Leu and GlnlOSLeu;

GlulAsp, Alal4Pro, Serl9Arg, !le20Leui GlnlOSLeu and Ala83Arg;

GlulAsp, Atal4Pro, 5erI9Arg, He20Leu, GlnlOSLeu and Asp85Glu ; - GlulAsp, A!al4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and ArglOSGIn; - GlulAsp, A!al4Pro, SerlSArg, lie20Leu, Ginl08Leu, AlaS3Arg and AspSSGIu; - GlulAsp, Aial4Pro, Serl9Arg, He20Leu, GlnlOSLeu, AlaS3Arg and ArglOSGtn; - GlulAsp, Aial4Pro, Serl9Arg, lle20Leu, Glnl08Leu, Asp85Glu and ArglOSGln; or - GlulAsp, Alal4Pro, Serl9Arg, !le20Leu, GlnlOSLeu, AfaSSArg, AspSSGIu and

Argl05Gln, in preparing a multivalent construct

Aspect F-50: Use of two monovalent constructs according to any of aspects F-l to F-4 in preparing a bivalent polypeptide.

Aspect F-Sl: Use of two monovalent constructs according to aspect F-50, in preparing a bivalent construct that preferably exhibits intramolecular binding compared to intermolecular binding.

Aspect F-52: Use of two monovalent constructs according to any of aspects F-50 to F-51, as a binding domain or binding unit in preparing a bivalent polypeptide, wherein the binding domains or binding units are linked via a linker such that the bivalent polypeptide preferably exhibits intramolecular binding compared to intermoiecuiar binding and/or the bivalent polypeptide can simultaneously bind both binding site on protein F of hRSV.

Aspect F-53: Use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ 10 NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance} and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-54: Use of two monovalent constructs according to aspect F-53, wherein the two monovalent constructs are identical.

Aspect r-55: Use of two monovalent constructs according to aspects F-53 or r-54, wherein the two monovalent constructs essentially consist of one of SEQ ID NO's: 60-76.

Aspect F-56: Use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO’s: 62, 65, 67,68,75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 62, 65, 67, 68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or a Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-S7: Use of two monovalent constructs according to aspect F-56, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 62,65, 67, 68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62,65, 67,68,75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine {Leu, L) at position 78 and an Arginine {Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino add difference, in preparing a bivalent polypeptide.

Aspect F·08: Use of two monovalent constructs according to aspects F-5S or F-57, wherein the two monovalent constructs are identical.

Aspect F-59; Use of two monovalent constructs according to aspect F-58, wherein the two monovalent constructs essentially consist of one ofSEQ ID NO's: 62,65,67, 68, 75 and 76.

Aspect F-6G: Use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent constructs are chosen from the following: a) SEQ10 NO's: 65 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and it) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-61: Use of two monovalent constructs according to aspect F-60, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's; 65 and 76, provided that: i} the amino acid sequence has an Aspartic acid {Asp, D} at position 54, a Giutamine {Glr., Q) at position 105, a Leucine {Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to If a bat numbering); and ti) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as denned herein} compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-62; Use of two monovaient constructs according to aspects F-60 or F-61, wherein the two monovalent constructs are identical.

Aspect F-63: Use of two monovalent constructs essentially consisting of 5EQ ID NO: 62 in preparing a bivalent polypeptide.

Aspect F-64: Use of two monovalent constructs essentially consisting of SEQ ID NO: 65 in preparing a bivalent polypeptide.

Aspect F-65: Use of two monovalent constructs essentially consisting of SEQ ID NO: 76 in preparing a bivalent polypeptide.

Aspect F-66: Use of two monovalent constructs according to any of aspects F-SO to F-52, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino add difference with one of SEQ ID NO's: 146-153, provided that: i} the amino add sequence has a Proiine (Pro, ?) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, Lj at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, ir* preparing a bivaient poiypeptide.

Aspect F-67: Use of two monovaient constructs according to aspect F-66, wherein the two monovaient constructs are identical.

Aspect F-68: Use of two monovaient constructs according to aspects F-66 or F-67, wherein the two monovalent constructs essentially consist of one of SEQ ID NQ's: 146-153.

Aspect F-69: Use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ. ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic add (Giu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent poiypeptide.

Aspect F-70: Use of two monovalent constructs according to aspect F-69, wherein the monovalent constructs are chosen from the following: a) SEQ iD NO's: 146-149 and 151-153; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ iD NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proiine {Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ iD NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q.) at position 105; SEQ. ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position S3 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 148, the amino acid sequence preferably has Glutamic acid (Glu, E} at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 149, the amino acid sequence preferably has Arginine (Arg, R) at position S3, Glutamic acid (Giu, E} at position 85 and Giutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R} at position 83; - SEQ ID NO: 152, the amino add sequence preferably has Glutamic add (Glu, E) at position 85; SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabat numbering); and ii) the amino add sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino add sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect P-71: Use of two monovalent constructs according to aspects F-69 or F-70, wherein the two monovalent constructs are identical.

Aspect F-72: Use of two monovalent constructs according to aspect F-71, wherein the two monovalent constructs essentially consist of one of SEQ ID NO's: 146-149 and 151-153.

Aspect F-73: Use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovaient construct essentially consists of SEQ ID MO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated seiected from the following: VaISLeu, AlslAPro, Serl9R, Ile20leu, Giu44G!y, Ala74Ser, Gly78Leu, AlaSSArg, AspSSGiu, ArglOSGln, GlnlOSLeu and Giy54Asp, in preparing a bivalent polypeptide.

Aspect F-74: Use of two monovalent constructs according to aspects F-73, wherein the monovaient construct essentially consists of SECl ID NO: 5, in which following amino acid residues have been mutated; Va!5Leu, A!al4Pro, Serl9R, He20Leu, Glu44Gly, Aia74Ser, Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin, Ginl08Leu and Gly54D, in preparing a bivalent polypeptide.

Aspect F-75: Use of two monovalent constructs according to aspects F-73, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated seiected from the following: Serl9R, iie20Leu, Ala74Ser, Giy78Leu,

Aia83Arg, AspSSGiu, ArglOSGln and Gly54D, in preparing a bivaient polypeptide.

Aspect F-76: Use of two monovalent constructs according to aspects F-73, wherein the monovaient construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated seiected from the following: Giy78Leu, Aia83Arg, AspS5G!u, Argl05G!n and Gly54D, in preparing a bivaient polypeptide.

Aspect F-77: Use of two monovaient constructs according to aspects F-75, wherein the

monovalent construct essentially consists of SEQ ID NO: 5, in which following aminD acid residues have been mutated: Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGln and Gly54D, in preparing a bivalent polypeptide.

Aspect F-7S: Use of two monovalent constructs according to any of aspects F-50 to F~52, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more {such as two, three or four) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu and GlnlOSLeu, in preparing a bivalent polypeptide.

Aspect F-79; use of two monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 5, In which one or more (such as two, three, four, five, six or seven) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, !le2QLeu, AlaSSArg, AspSSGiu, ArglOSGln and GlnlOSLeu, in preparing a bivalent polypeptide.

Aspect F-80: Use of two monovalent constructs according to aspects F-73, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: - Val5leu, Alal4Pro, Glu44Gly, Gly78Leu, AlaSSArg, AspSSGiu, ArglOSGln and GlnlOSLeu;

AlaSSArg, Asp85Glu, Argl05Gln and Glnl08Leu;

Gty78Leu, Aia83Arg, Asp85Giu and ArglOSGln; - VaISLeu, A!al4Pro, Glu44Gly, G!y78Leu, Ala83Arg, AspSSGiu, ArglOSGln, Glnl08leu and Gly54Asp;

Aia83Arg, Asp85Glu, ArglOSGln, Ginl08Leu and Gly54Asp;

Gly78Leu, AlaSSArg, Asp85Glu, ArglOSGln and Glv54Asp;

Gly54Asp;

Aial4Pro, Serl9Arg, lle20Leu and Ginl08Leu; - Alal4Pro, Serl9Arg, He20Leu, Glnl08Leu and Ala83Arg; - Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Asp85Glu;

Alal4Pro, SerlSArg, lle20Leu, GlnlOSLeu and Argl05Gln; - Aial4Pro, SerlSArg, He20Leu, GlnlOSLeu, Ala83Arg and Asp85Glu;

Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Ala83Arg and Argl05Gin;

Aial4Pro, SerlSArg, lie20Leu, GlnlOSLeu, Asp85Glu and Argl05G!n; or - Aial4Pro, SerlSArg, 11520160, GlnlOSLeu, AlaSSArg, Asp85GIu and Argl05Gln, in preparing a bivalent polypeptide.

Aspect F-81: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct is chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 138-141 and 154-157, provided that: i} the amino acid sequence has a Aspartic acid {Asp, D) at position 1 (said position determined according to Kabat numbering}: and fi) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-82: Use of a monovalent constructs according to aspect F-81, wherein the monovaient construct essentially consist of one of SEQ ID NO's: 138-141 and 154-157.

Aspect F-83: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ, ID NO: 5, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-84: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovaient construct essentially consists of SEQ ID NO: 52, in which the Giutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-85: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 65, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-86: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-S7: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 75, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-88: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 147, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing 3 bivalent polypeptide.

Aspect F-8S: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 149, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-9C: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 153, in which the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect r-91: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Prc, SerlSR, lle20Leu, Glu44Gly, Ala74Ser, Giy78Leu, Ala83Arg, Asp85Glu, ArglOSGln, GinlOSLeu and Gly54Asp, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-92; Use of a monovalent constructs according to aspects F-91, wherein the monovalent construct essentially consists of SECt ID NO: 5, in which following amino acid residues have been mutated: VaISLeu, ASal4Pro, Serl9R, !le20Leu, Glu44Gly, AIa74Ser, Gly78Leu, Ala83Arg, Asp85Giu, ArglOSGIn, Glnl08Leu and Giy54D, and wherein the Glutamic acid at position i has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-S3: Use of a monovalent constructs according to aspects F-91, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, lie20Leu, Ala74Ser, Gly78Leu, Aia83Arg, AspSSGlu, ArglOSGin and G!y54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent poiypeptide.

Aspect F-94: Use of a monovalent constructs according to aspects F-91, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more {such as two, three, four or five) amino add residues have been mutated selected from the following: Giy78Leu, Ala83Arg, AspSSGIu, Argl05Gln and G!y54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-95: Use of a monovalent constructs according to aspects F-94, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: Giy78Leu, Ala83Arg, Asp85Glu, ArglQSGin and Gly54D, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-96: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: S, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the following: Atal4Pro, Serl9Arg, IteZQLeu and GinlOSLeu, and wherein the Glutamic add at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-S7: Use of a monovalent constructs according to any of aspects F-50 to F-52, wherein the monovalent construct essentially consists of SEQ ID NO: S, in which one or more (such as two, three, four, five, six or seven} amino acid residues have been mutated selected from the following: Alal4Prc, Serl9Arg, lie20Leu, Aia83Arg, AspSSGIu, ArglOSGin and GlnlOSLeu, and wherein the Glutamic acid at position 1 has been changed into Aspartic acid, in preparing a bivalent polypeptide.

Aspect F-98: Use of a monovalent constructs according to aspects F-91, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

GlulAsp; - GlulAsp, VaISLeu, A!al4Pro, Giu44Gly, Giy78Leu, AiaSBArg, AspSSGIu, ArglOSGIn and Glnl08leu;

GlulAsp, Aia83Arg, Asp85Glu, ArglOSGIn and GlnlOSLeu; ~ GlulAsp, G!y78Leu, AlaS3Arg, Asp85Glu and ArglOSGIn;

GlulAsp, VaISLeu, Alal4Pro, Glu44Gly, Gly78Leu, AiaSBArg, Asp85Glu, ArglOSGIn, Glnl08Leu and Gly54Asp; - GlulAsp, AiaSBArg, AspSSGIu, ArglOSGin, GlnlOSLeu and Gly54Asp; - GlulAsp, Giy78Leu, Aia83Arg, AspSSGIu, Argl05Gin and Gly54Asp;

GlulAsp and Gly54Asp;

GlulAsp, Alal4PiO, Serl9Arg, !le20Leu and GlnlOSLeu;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and Ala83Arg;

GlulAsp, A!al4Pro, SerlSArg, !le20Leu, GlnlOSLeu and AspSSGIu; - GlulAsp, Aial4Pro, SerlSArg, He20Leu, GlnlOSLeu and ArglOSGin;

GlulAsp, Alal4Prc, Serl9Arg, Ue20leu, Glnl08Leu, AiaSBArg and Asp85Glu; GlulAsp, Alal4Pro, Serl9Arg, He20Leu, GlnlOSLeu, AiaSBArg and ArglOSGin; GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AspSSGIu, ArglOSGin; or - GlulAsp, A!al4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, AiaSBArg, Asp85Glu and ArglOSGin, in preparing a bivalent polypeptide.

Aspect F-99: Use of three monovalent constructs according to any of aspects F-l to F-4 in preparing a trivalent polypeptide.

Aspect F-100: Use of three monovalent constructs according to aspect F-99, in preparing a trivalent construct that preferably exhibits intramolecular binding compared to Intermolecular binding.

Aspect F-101; Use of three monovalent construct according to any of aspects F-99 to F-10G, as a binding domain or binding unit in preparing a trivalent polypeptide, wherein the binding domains or binding units are linked via a linker such that the trivalent polypeptide preferably exhibits intramolecular binding compared to intermolecular binding and/or the trivalent polypeptide can simultaneously bind all three binding site on protein F of hR5V.

Aspect F-102: Use of three monovalent constructs according to any of aspects F-99 to F-101, wherein the monovalent constructs are chosen from the following: aj SEQ ID NO's: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivalent polypeptide.

Aspect F-103: Use of three monovalent constructs according to aspect F-102, wherein the three monovalent constructs are identical.

Aspect F-104: Use of three monovalent constructs according to aspects F-102 or F-103, wherein the three monovalent constructs essentially consist of one of SEQ ID NO's: 60-76.

Aspect F-105: Use of three monovalent constructs according to any of aspects F-99 to F-101, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; b) amino add sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 62,65, 67,68, 75 and 76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, b Leucine (Leu, L) at position 78 and/or a Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface piastnon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a bivalent polypeptide.

Aspect F-106: Use of three monovalent constructs according to aspect F-105, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO’s: 62, 65,67,68, 75 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 62, 65,67, 68,75 and 75, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivalent polypeptide.

Aspect F-1G7: Use of three monovalent constructs according to aspects F-105 or F-106, wherein the three monovalent constructs are identical.

Aspect F-108: Use of three monovalent constructs according to aspect F-107, wherein the three monovalent constructs essentially consist of one of SEQ ID NO's: 62, 65,67, 68,75 and 76.

Aspect F-109: Use of three monovalent constructs according to any of aspects F-9S to F-101, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 65 and 76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and/or an Arginine (Arg, R) at position S3 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino add difference, in preparing a trivalent polypeptide.

Aspect F-110: Use of three monovalent constructs according to aspect F-109, wherein the monovalent consmicts are cnosen from the following: a) SEQ ID NO's: :65 and 75; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 65 and 76, provided that: i) the amino acid sequence has an Aspartic acid (Asp, D) at position 54, a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78 and an Arginine (Arg, R) at position 83 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivalent polypeptide.

Aspect F-lli: Use of three monovalent constructs according to aspects F-109 or F-llO, wherein the three monovalent constructs are identical.

Aspect F-112: Use of three monovalent constructs essentially consisting of SEQ ID NO: 62 in preparing a trivaient polypeptide.

Aspect F-112: Use of three monovalent constructs essentially consisting of SEQ 10 WO: 65 in preparing a trivaient polypeptide.

Aspect F-114: Use of three monovalent constructs essentially consisting of SEQ ID WO: 76 In preparing a trivaient polypeptide.

Aspect F-115: Use of three monovalent constructs according to any of aspects F-99 to F-1G1, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 146-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ !D NO's: 146-153, provided that: i) the amino acid sequence has a Proiine {Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine {Leu, L) at position 108 (said positions determined according to Rabat numbering); and ii) the amino acid sequence binds protein F of HRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3,2 or 1 amino acid difference, in preparing a trivaient polypeptide.

Aspect F-115: Use of three monovalent constructs according to aspect F-115, wherein the three monovalent constructs are identical.

Aspect F-H7: Use of three monovalent constructs according to aspects F-115 or F-116, wherein the three monovalent constructs essentially consist of one of SEQ ID NO's: 146-153.

Aspect F-118: Use of three monovalent constructs according to any of aspects F-9S to F-101, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b} amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-149 and 151-153, provided that: i) the amino acid sequence has a Proline {Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R) at position 83, Glutamic acid {Glu, £} at position 85 and/or Glutamine {Gin, Q) at position 105 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured oy surface plasmon resonance) and/or the amino acid sequence has the same, about the same, ora higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivaient polypeptide.

Aspect F-11S: Use of three monovalent constructs according to aspect F-118, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 146-149 and 151-153; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 146-14S and 151-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 and in addition Arginine (Arg, R} at position 83, Giutamic acid (Glu, E) at position 85 and/or Glutamine (Gin, Q) at position 105 so that when the amino acid sequence has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with: SEQ ID NO: 146, the amino acid sequence preferably has Glutamine (Gin, Q) at position 105; - SEQ ID NO: 147, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 148, the amino add sequence preferably has Glutamic acid (Gin, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 14S, the amino acid sequence preferably has Arginine {Arg., R) at position 83, Glutamic acid (Glu, E) at position 85 and Glutamine (Gin, Q) at position 105; SEQ ID NO: 151, the amino acid sequence preferably has Arginine (Arg, R) at position 83; SEQ ID NO: 152. the amino acid sequence preferably has Glutamic acid (Giu, E) at position 85; SEQ ID NO: 153, the amino acid sequence preferably has Arginine (Arg, R) at position 83 and Glutamic acid (Glu, E) at position 85; (said positions determined according to Kabaf numbering}; and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance} and/or the amino acid sequence has the same, about the same, or a higher potency (as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivalent polypeptide.

Aspect F-120: Use of three monovalent constructs according to aspects F-118 or F-119, wherein the three monovalent constructs are identical.

Aspect F-121: Use of three monovalent constructs according to aspect F-120, wherein the three monovalent constructs essentially consist of one of SEQ ID NO's: 145-149 and 151-153.

Aspect F-122: Use of three monovalent constructs according to any of aspects F-9S to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Aial4Pro, Serl9R, lle20Leu, Giu446iy, Ala74Ser, Gly78Leu, AlaSBArg, Asp85Glu, ArglOSGIn, Glnl08Leu and Giy54Asp, in preparing a trivalent polypeptide.

Aspect F-123: Use of three monovalent constructs according to aspects F-122, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: VaiSLeu, Alal4Pro, Serl9R, lle20Leu, Giu44Gly; Aia74Ser, Glv78Leu, AiaSBArg, AspSSGiu, Argl05Gln, GlnlOSLeu and Gly54D, in preparing a trivalent polypeptide.

Aspect F-124: Use of three monovalent constructs according to aspects F-122, wherein the monovaient construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, Ue20leu, Aia74Ser, Giy78Leu,

AlaS3Arg, AspSSGiu, ArglOSGin and Giy54D, in preparing a trivaient poiypeptioe.

Aspect F-125: Use of three monovalent constructs according to aspects F-122, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino add residues have been mutated selected from the following: Gly78Leu, Ala83Arg, AspSSGiu, ArglOSGin and Gly54D, in preparing a trivalent polypeptide.

Aspect F-126: Use of three monovaient constructs according to aspects F-125, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino add residues have been mutated: G!y78Leu, Ala83Arg, Asp85Giu, ArglG5Gln and Gly54D, in preparing a trivalent polypeptide.

Aspect F-127: Use of three monovalent constructs according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu and Glnl08Leu, in preparing a trivalent polypeptide.

Aspect F-12S: Use of three monovalent constructs according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino acid residues have been mutated selected from the following: Alal4Pro, Serl9Arg, ile20Leu, Ala83Arg, AspSSGiu, ArglOSGin and GlnlOSLeu, in preparing a trivalent polypeptide.

Aspect F-129: Use of three monovalent constructs according to aspects F-122, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated:

Va!5Leu, Alal4Pro, Giu44Gly, Gly78Leu, Ala83Arg, AspSSGIu, ArglOSGIn and GlnlOSLeu;

AiaSSArg, AspSSGIu, ArglOSGIn and Glnl08Leu;

Gly7SLeu, Aia83Arg, AspSSGIu and ArglOSGIn; - VaISLeu, AlaUPro, Glu446ly, Gly78Leu, ASaB3Arg, Asp85Glu, ArglOSGIn, GlnlOSLeu and Gly54Asp;

Ala83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Giy54Asp; G!y78Leu, AiaSSArg, AspSSGIu, ArglOSGIn and Gly54Asp;

Gly54Asp; - Alal4Pro, Serl9Arg, lie20Leu and GlnlOSLeu;

Alal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and AiaSSArg; AJal4Pro, Serl9Arg, lie20Leu, Glnl08Leu and Asp85G!u ;

Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu and Argl05Gin; - A!al4Pro, SerlSArg, lie20Leu, GlnlOSLeu, AiaSSArg and AspSSGIu;

Aial4Pro, SerlSArg, lle20Leu, Glnl08Leu, Aia83Arg and Argl05Gln; - ASal4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Asp85Glu and ArglQ5Gln; - Aial4Pro, Serl9Arg, lle20Leu, GlnlOSLeu, Ala83Arg, Asp85Giu and ArglOSGIn, in preparing a trivaient poiypeptide.

Aspect F-130: Use of an amino acid sequence with SEQ. ID NO: 62 in preparing a trivaient polypeptide with SEQ ID NO: 77, wherein an amino acid sequence with SEQ ID NO: 62 is linked to at least two further amino acid sequences with SEQ ID NO: 62, via a 15GS linker.

Aspect F-131: Use of an amino acid sequence with SEQ ID NO: 65 in preparing a trivaient polypeptide with SEQ ID NO: 78, wherein an amino acid sequence with SEQ ID NO: 65 is linked to at least two further amino acid sequences with SEQ ID NO: 65, via a 15GS linker.

Aspect F-132: Use of an amino acid sequence with SEQ ID NO: 76 in preparing a trivaient polypeptide with SEQ ID NO: 79, wherein an amino acid sequence with SEQ ID NO: 76 is linked to at least two further amino acid sequences with SEQ iD NO: 76, via a 15G5 linker.

Aspect F-133: Use of an amino acid sequence with SEQ ID NO: 75 in preparing a trivaient polypeptide with SEO. ID NO: 158, wherein an amino acid sequence with SEQ ID NO: 75 is linked to at ieast two further amino acid sequences with SEQ ID NO: 75, via a 15GS linker.

Aspect F-134: Use of an amine acid sequence with SEQ ID NO: 147 in preparing a trivaient polypeptide with SEQ ID NO: 159, wherein an amino acid sequence with SEQ ID NO: 147 is linked to at ieast two further amino acid sequences with SEQ ID NO: 147, via a 15GS linker.

Aspect F-135: Use of an amino acid sequence with SEQ ID NO: 149 in oreparing a trivaient polypeptide with SEQ ID NO: 160, wherein an amino acid sequence with SEQ ID NO: 149 is linked to at least two further amino acid sequences with SEQ ID NO: 149, via a 15GS linker.

Aspect F-136: Use of an amino add sequence with SEQ ID NO: 153 in preparing a trivaient poiypeptide with SEQ ID NO: 161, wherein an amino acid sequence with SEQ ID NO: 153 is linked to at least two further amino acid sequences with SEQ ID NO: 153, via a 15GS linker.

Aspect F-137: Use of a monovalent constructs according to any of aspects F-99 to F-101, wherein the monovalent constructs are chosen from the following: a) SEQ ID NO's: 138-141 and 154-157; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO's: 138-141 and 154-157, provided that: i) the amino acid sequence has a Aspartic acid (Asp, D} at position 1 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity {said affinity as measured by surface piasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency {as defined herein) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, in preparing a trivaient polypeptide.

Aspect F-138: Use of a monovalent constructs according to aspect F-137, wherein the monovalent construct essentially consist of one of SEQ ID NO's: 138-141 and 154-157.

Aspect F-139: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ. ID WO: 5, in which the Giutamic acid at position 1 is changed into Aspartic acid, in preparing a trivaient polypeptide.

Aspect F-140: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 62, in which the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivaient polypeptide.

Aspect F-141: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ iD WO: 65, in which the Giutamic acid at position 1 is changed into Aspartic acid, in preparing a trivaient poiypeptide.

Aspect F-142: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent consxruct essentially consists of SEQ iD WO: 76, in which the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivaient polypeptide.

Aspect F-143: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ iD WO: 75, in which the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivaient polypeptide.

Aspect F-144: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 147, in which the Glutamic acid at position 1 Is changed into Aspartic acid, in preparing a trivaient poiypeptide.

Aspect F-145: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovaient construct essentially consists of SEQ ID NO: 149, in which the Glutamic acid at position 1 is changed into Aspartic add, in preparing a trivaient polypeptide.

Aspect F-146: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEG ID NO: 153, in which the Glutamic acid at position 1 is changed into Asoartic acid, in preparing a trivalent polypeptide.

Aspect F-147: Use of a monovalent construct according to any of aspects F-99 to F-lCl, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: VaISLeu, Alal4Pro, Serl9R, lie20Leu, Glu44Gly, Aia74Ser, Giy7BLeu, AiaSSArg, AspSSGIu, ArglOSGIn, GlnlOSteu and Gly54Asp, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent polypeptide.

Aspect F-148: Use of a monovalent construct according to aspects F-147, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: ValSleu, Alal4Pro. Serl9R, He20Leu, 3lu44Gfy, Ala74Ser, Gly78leu, Ata83Arg, AspSSGIu, ArglOSGIn, GlnlOSLeu and Gly54D, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent construct.

Aspect F-149: Use of a monovalent construct according to aspects F-147, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven or eight) amino acid residues have been mutated selected from the following: Serl9R, He20Leu, Ala74Ser, Gly78leu, Ala83Arg, AspSSGIu, Argl05Gln and Gly54D, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent polypeptide.

Aspect F-15Q; use of a monovalent construct according to aspects F-147, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three, four or five) amino acid residues have been mutated selected from the following: G!y78leu, Aia83Arg, Asp85Glu, ArglOSGIn and GlyS4D, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent polypeptide.

Aspect F-isi; Use of amonovalent construct according to aspects F-150, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino acid residues have been mutated: Gly7SLeu, AiaS3Arg, AspSSGlu, ArglOSGin and Giy54D, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent polypeptide.

Aspect F-152: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which one or more (such as two, three or four) amino acid residues have been mutated selected from the foiiowing: Alal4Pro, Serl9Arg, lle20Leu and GinlOSLeu, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent poiypeptide.

Aspect F-153: Use of a monovalent construct according to any of aspects F-99 to F-101, wherein the monovalent construct essentially consists of SEQ. ID NO: 5, in which one or more (such as two, three, four, five, six or seven) amino add residues have been mutated selected from the following: Alal4Pro, Serl9Arg, lle20Leu, AlaSSArg, AspS5Glu, ArglOSGin and GinlOSLeu, and wherein the Glutamic acid at position 1 is changed into Aspartic acid, in preparing a trivalent polypeptide.

Aspect F-154: Use of a monovalent construct according to aspects F-147, wherein the monovalent construct essentially consists of SEQ ID NO: 5, in which following amino add residues have been mutated:

GlulAsp; - GiulAsp, ValSLeu, Alal4Pro, Glu44G!y, Giy78Leu, AlaSSArg, Asp85Glu, ArglOSGin and GinlOSLeu;

GlulAsp, AlaS3Arg, AspSSGlu, ArglOSGin and GinlOSLeu;

GlulAsp, 6ly78Leu, A!a8SArg, AspSSGlu and ArglOSGin;

GlulAsp, ValSLeu, Alal4Pro, Glu44Gly, Gly78Leu, AlaSSArg, AspSSGlu, ArglOSGin, GinlOSLeu and Gly54Asp; - GlulAsp, Ala83Arg, AspSSGlu, Argl05Gln, Ginl08Leu and Gly54Asp; - GlulAsp, Giy78Leu, AlaSSArg, Asp85Glu, ArglOSGin and Gly54Asp;

GiulAsp and Gly54Asp;

GlulAsp, Alal4Pro, SerlSArg, lie20Leu and 6lnl08Leu; - GlulAsp, Alal4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Ala83Arg; - GlulAsp, ASal4Pro, Serl9Arg, Ile20Leu, Glnl08Leu and Asp85Glu; - GlulAsp, Aial4Pro, Serl9Arg, lle20Leu, Glnl08Leu and Argl05Gin;

GlulAsp, Alal4Pro, Serl9Arg, lle20Leu; Ginl08Leu, Aia83Arg and AspS5Glu; - GlulAsp, Atal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, Aia83Arg and ArglOSGIn; - GlulAsp, Aial4Pro, Serl9Arg, Ile20leu, Glnl08leu, AspSSGiu and ArglOSGIn; or - GlulAsp, AIal4Pro, Serl9Arg, lle20Leu, Glnl08Leu, Ala83Arg, Asp85Glu and Argl05Gln, in preparing a trivaient construct

Aspect F-15S: Use of an amino acid sequence with SEQ ID NO: 138 in preparing a trivaient polypeptide with SEQ ID NO: 142, wherein an amino acid sequence with SEQ ID NO; 138 is linked to at least two further amino acid sequences with SEQ ID NO: 5, via a 15GS linker.

Aspect F-156: Use of an amino add sequence with SEQ ID NO: 139 in preparing a trivaient polypeptide with SEQ ID NO: 143, wherein an amino acid sequence with SEQ ID NO: 139 is linked to at least two further amino acid sequences with SEQ ID NO: 62, via a 15GS linker.

Aspect F-157: Use of an amino acid sequence with SEQ ID NO: 140 in preparing a trivaient polypeptide with SEQ ID NO; 144, wherein an amino acid sequence with SEQ ID NO: 140 is linked to at least two further amino acid sequences with SEQ ID NO: 65, via a 15GS linker.

Aspect F-158: Use of an amino acid sequence with SEQ ID NO: 141 in preparing a trivaient polypeptide with SEQ ID NO: 145, wherein an amino acid sequence with SEQ ID NO: 141 is linked to at least two further amino add sequences with SEQ ID NO: 76, via a 15GS linker,

Aspect F-159; Use of an amino add sequence with SEQ ID NO: 154 in preparing a trivaient polypeptide with SEQ ID NO; 162, wherein an amino acid sequence with SEQ ID NO; 154 is linked to at least two further amino acid sequences with SEQ iD NO: 75, via a 15GS linker.

Aspect F-16Q: Use of an amino acid sequence with SEQ iD WO: 155 in preparing a trivaient poiypeptide with SEQ ID NO: 163, wherein an amino acid sequence with SEQ ID NO: 155 is linked to at least two further amino acid sequences with SEQ ID NO: 147, via a 15GS linker.

Aspect F-161: Use of an amino acid sequence with SEQ ID NO: 156 in preparing a trivaient polypeptide with SEQ ID NO: 164, wherein an amino acid sequence with SEQ ID NO: 156 is iinked to at ieast two further amino acid sequences with SEQ ID NO: 149, via a 15GS linker.

Aspect F-162: Use of an amino acid sequence with SEQ ID NO: 157 in preparing a trivaient polypeptide with SEQ ID NO: 165, wherein an amino acid sequence with SEQ ID NO: 157 is linked to at least two further amino acid sequences with SEQ ID NO: 153, via a 15GS linker.

Aspect E-262: Polypeptide according to any of aspects E-l to E-261, which has an increased half-iife, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se or Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 per se, respectively.

Aspect E-263: Polypeptide according to aspects E-262, in which one or more other binding units provide the polypeptide with increased half-life, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-i to C-38 and W-l to W-38 per se or Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 perse, respectively.

Aspect E-264: Polypeptide according to aspects E-262 or E-263, in which said one or more other binding units that provide the polypeptide with increased half-life is chosen from the group consisting of serum proteins or fragments thereof, binding units that can bind to serum proteins, an Fc portion, and small proteins or peptides that can bind to serum proteins.

Aspect E-265: Polypeptide according to any of aspects E-262 to E-264, in which said one or more other binding units that provide the poiypeptide with increased half-iife is chosen from the group consisting of human serum albumin or fragments thereof.

Aspect E-266: Polypeptide according to any of aspects E-262 to E-265, in which said one or more other binding units that provides the polypeptide with increased half-life are chosen from the group consisting of binding units that can bind to serum albumin (such as human serum albumin) ora serum immunoglobulin (such as IgG).

Aspect E-267: Polypeptide according to any of aspects E-262 to E-266, in which said one or more other binding units that provides the polypeptide with increased half-life are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino acid sequences that are suitable for use as a dAb, or Nanobodies® that can bind to serum albumin (such as human serum albumin) ora serum immunoglobulin (such as IgG).

Aspect E-268: Polypeptide according to any of aspects E-2S2 to E-267, in which said one or more other binding units that provides the polypeptide with increased half-life is a Nanobody® that can bind to serum albumin (such as human serum albumin) or a serum immunoglobulin (such as igG).

Aspect E-269: Polypeptide according to any of aspects E-262 to E-268, that has a serum half-life that is at least 1.5 times, preferably at least 2 times, such as at least 5 times, for example at least 1C- times or more than 20 times, greater than the half-life of the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se or Nanobody® according to any of aspects 8-1 to B-18, D-1 to D-38 and X-l to X-38 per se, respectively.

Aspect E-270: Polypeptide according to any of aspects E-262 to E-269, that has a serum half-life that is increased with more than 1 hours, preferably more than 2 hours, more preferably more than 6 hours, such as more than 12 hours, or even more than 24, 48 or 72 hours, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se or Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 per se, respectively.

Aspect £-271: Polypeptide according to any of aspects E-262 to E-270, that has a serum half-life in human of at least about 12 hours, preferably at least 24 hours, more preferably at ieast4S hours, even more preferably at least 72 hours or more; for example, of at least 5 days {such as about 5 to 10 days), preferably at least 9 days (such as about 9 to 14 days), more preferably at least about 10 days {such as about 10 to 15 days), or at least about 11 days (such as about 11 to 16 days), more preferably at least about 12 days {such as about 12 to 18 days or more), or more than 14 days (such as about 14 to 19 days).

Aspect G-l: Compound or construct that comprises or essentially consists of one or more amino acid sequences according to any of aspects A-i to A-29, C-l to C-3S and W-l to W-3S and/or one or more Nanobodies*' according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 and/or one or more polypeptides according to any of aspects E-l to E-271, and optionally further comprises one or more other groups, residues, moieties or binding units, optionally linked via one or more Sinkers.

Aspect G-2: Compound or construct according to aspect G-l, in which said one or more other groups, residues, moieties or binding units are amino acid sequences.

Aspect G-3: Compound or construct according to any of aspects G-l or G-2, in which said one or more linkers, if present, are one or more amino acid sequences.

Aspect G-4: Compound or construct according to any of aspects G-l to G-3, in which said one or more other groups, residues, moieties or binding units are immunoglobulin sequences.

Aspect G-5: Compound or construct according to any of aspects G-l to G-4, in which said one or more other groups, residues, moieties or binding units are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's”, amino acid sequences that are suitable for use as a dAb, or Nanobodies®.

Aspect G-6: Compound or construct according to any of aspects G-l to G-5, in which said one or more amino acid sequences of the invention are immunoglobulin sequences.

Aspect S-7: Compound or construct according to any of aspects G-l to G-6, in which said one or more amino acid sequences of the invention are chosen from the group consisting of domain antibodies, amino add sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb's", amino acid sequences that are suitable for use as a dAb, or Nanobodies®.

Aspect G-8: Compound or construct according to any of aspects G-l to G-7, that comprises or essentially consists of one or more Nanobodies® according to any of aspects E-l to B-18, D-i to D-38 and X-l to X-38, and in which said one or more other groups, residues, moieties or binding units are Nanobodies®.

Aspect G-9: Compound or construct according to any of aspects G-i to 6-8, which is a multivalent construct.

Aspect G-10: Compound or construct according to any of aspects G-l to G-9, which is a multispecific construct.

Aspect G-ll: Compound or construct according to any of aspects G-l to G-10, which has an increased half-life, compared to the corresponding amino acid sequence according to any of aspects A-l to A-28, C-l to C-38 and W-l to W-38 per se or Nanobody® according to any of aspects B-l to B-18, 0-1 to D-38 and X-i to X-38 per se, or polypeptide according to any of aspects E-l to E-271 per se, respectively.

Aspect G-12: Compound or construct according to any of aspects G-l to G-ll, in which said one or more other groups, residues, moieties or binding units provide the compound or construct with increased half-life, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se or Nanobody* according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 per se, or polypeptide according to any of aspects E-l to E-271 per se, respectively.

Aspect G-13: Compound or construct according to aspect G-12, in which said one or more other groups, residues, moieties or binding units that provide the compound or construct with increased half-life is chosen from the group consisting of serum proteins or fragments thereof, binding units that can bind to serum proteins, an Fc portion, and small proteins or peptides that can bind to serum proteins.

Aspect G-14: Compound or construct according to any of aspects G-12 or G-13, in which said one or more other groups, residues, moieties or binding units that provide the compound or construct with increased half-life is chosen from the group consisting of human serum albumin or fragments thereof.

Aspect G-15: Compound or construct according to any of aspects G-12 to G-14, in which said one or more other groups, residues, moieties or binding units that provide the compound or construct with increased half-life are chosen from the group consisting of binding units that can bind to serum albumin (such as human serum albumin) or a serum immunoglobulin (such as igG),

Aspect G-16: Compound or construct according to any of aspects G-12 to G-15, in which said one or more other groups, residues, moieties or binding units that provides the compound or construct with increased haif-life are chosen from the group consisting of domain antibodies, amino acid sequences that are suitable for use as a domain antibody, single domain antibodies, amino acid sequences that are suitable for use as a single domain antibody, "dAb"'s, amino acid sequences that are suitable for use as a dAb, or Nanobodies* that can bind to serum albumin (such as human serum albumin) or a serum immunoglobulin (such as IgG).

Aspect G-17: Compound or construct according to any of aspects G-12 to G-16, in which said one or more other groups, residues, moieties or binding units that provides the compound or construct with increased half-iife is a Nanobody*’ that can bind to serum albumin (such as human serum albumin) or a serum immunoglobulin (such as IgG).

Aspect G-18: Compound or construct according to any of aspects G-ll to G-17, that has a serum half-life that is at least 1.5 times, preferably at least 2 times, such as at least 5 times, for example at least 10 times or more than 20 times, greater than the half-life of the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se or Nanobody®' according to any of aspects B-l to B-18, D-1 to D-30 and X-l to X-38 per se, or polypeptide according to any ot aspects t-ι to t-271 per se, respectively.

Aspect G-19: Compound or construct according to any of aspects G-ll to G-18, that has a serum half-life that is increased with more than 1 hours, preferably more than 2 hours, more preferably more than 6 hours, such as more than 12 hours, or even more than 24,48 or 72 hours, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-i to W-3S per se or Nanobody® according to any of aspects B-l to B-18, D-I to D-38 and X-l to X-38 per se, or polypeptide according to any of aspects E-l to E-271 per se, respectively,

Aspect G-20: Compound or construct according to any of aspects G-ll to 6-19, that has a serum half-life in human of at least about 12 hours, preferably at least 24 hours, more preferably at ieast 48 hours, even more preferably at least 72 hours or more; for example, of at ieast 5 days {such as about 5 to 10 days), preferably at least 9 days {such as about 9 to 14 days), more preferably at least about 10 days (such as about 10 to 15 days), or at least about 11 days {such as about 11 to 16 days), more preferably at least about 12 days {such as about 12 to 18 days or more), or more than 14 days (such as about 14 to IS days).

Aspect M-l: Nucleic acid or nucieotide sequence, that encodes an amino acid sequence according to any of aspects ΑΊ to A-2S, C-l to C-30 and W-l to W-38, a Nanobody® according to any of aspects B-l to B-1S, D-l to D-30 and X-l to X-38, a polypeptide according to any of aspects E-l to E-271, a compound or construct according to any of aspects G~1 to G-20, that is such that it can be obtained by expression of a nucleic add or nucleotide sequence encoding the same, or a monovaient construct according to any of aspects F-l to F-4.

Aspect M-2: Nucleic acid or nucleotide sequence according to aspect M-l, that is in the form of a genetic construct.

Aspect M-3: Use of a nucleic acid or nucleotide sequence according to aspect M-l, that encodes a monovalent construct according to any of aspects F-l to F-4, for the preparation of a genetic construct that encodes a multivalent polypeptide according to any of aspects E-l to E-271.

Aspect M-4: Use of a nucleic acid or nucleotide sequence according to aspect M-2, wherein the genetic construct encodes a multivalent (such as a bivalent) construct.

Aspect N-l: Host or host cell that expresses, or that under suitable circumstances is capable of expressing, an amino add sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, a Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38, a polypeptide according to any of aspects E-l to E-271, a compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nucleic acid or nucleotide sequence encoding the same, or a monovalent construct according to any of aspects f-l to F-4; and/or that comprises a nucieic acid or nucleotide sequence according to aspects M-l or M-2.

Aspect 0-1: Composition, comprising at least one amino add sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, Nanobody® according to any of aspects B-l to B-18, D-l to D-3S and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovaient construct according to any of aspects F-l to F-4, or nucleic acid or nucleotide sequence according to aspects M-l or M-2.

Aspect 0-2: Composition according to aspect 0-1, which is a pharmaceutical composition.

Aspect 0-3: Composition according to aspects 0-1 or 0-2, which is a pharmaceutical composition, that further comprises at least one pharmaceutically acceptable carrier, diluent or excipient and/or adjuvant, and that optionally comprises one or more further pharmaceutically active polypeptides and/or compounds.

Aspect P-1: Method for producing an amino acid sequence according to any of aspects A-l to A- 29, C-i to C-38 and W-l to W-38, a Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38, a polypeptide according to any of aspects E-l to E-271, a compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nucleic acid or nucleotide sequence encoding the same, or a monovalent construct according to any of aspects F-l to F-4, or a composition according to any of aspects 0-1 to 0-3,said method at least comprising the steps of: a) expressing, in a suitable host celi or host organism or in another suitable expression system, a nucleic acid or nucleotide sequence according to aspects M-l or M-2, optionally followed by: b) isolating and/or purifying the amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, the Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38, the polypeptide according to any of aspects E-l to E-271. the compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nudeic acid or nucleotide sequence encoding the same, or the monovalent construct according to any of aspects F-l to F-4, thus obtained.

Aspect P-2: Method for producing an amino acid sequence according to any of aspects A-l to A- 29, C-l to C-38 and W-l to W-38, a Nano body* according to any of aspects B-l to 6-18, D-l to D-38 and X-l to X-38, a polypeptide according to any of aspects E-l to K-271, a compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nucleic acid or nucleotide sequence encoding the same, or a monovalent construct according to any of aspects F-l to F-4, or a composition according to any of aspects 0-1 to 0-3, said method at least comprising the steps of: a) cultivating and/or maintaining a host or host cell according to aspect N-l under conditions that are such that said host or host celi expresses and/or produces at least one amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-3S, a polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nucleic acid or nucleotide sequence encoding the same, or monovalent construct according to any of aspects F-l to F-4, or composition according to any of aspects 0-1 to 0-3, optionally followed by: b) isolating and/or purifying the amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, the Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-3S, the polypeptide according to any of aspects E-l to E-271, the compound or construct according to any of aspects G-l to G-20, that is such that it can be obtained by expression of a nucleic acid or nucleotide sequence encoding the same, or the monovalent construct according to any of aspects F-l to F-4, or the composition according to aspects o-i to 0-3, thus obtained.

Aspect P-3: Method for preparing a bivalent or trivalent polypeptide according to any of aspects E-7 to E-261, said method comprising at least the steps of linking two or more monovalent amino acid sequences or monovalent construct according to any of aspects F-l to F-4 and for example one or more linkers.

Aspect P-4: Method according to aspect P-3, comprising the steps of: a) linking two or more nucleic acid sequences according to aspect lvi-1, encoding a monovalent construct according to any of aspects F-l to F-4 (and also for example nucleic acids encoding one or more linkers and further one or more further elements of genetic constructs known per se) to obtain a genetic construct according to aspect M-2; b} expressing, in a suitable host cell or host organism or in another suitable expression system, the genetic construct obtained in a) optionally followed by: c} isolating and/or purifying the bivalent or trivalent polypeptide according to any of aspects E-7 to E-261, thus obtained.

Aspect Q*l: Method for screening amino acid sequences directed against protein F of hRSV, said method comprising at least the steps of: a. providing a set, collection or library of nucleic acid sequences encoding amino acid sequences; b. screening said set, collection or library of nucleic acid sequences for nucieic acid sequences that encode an amino acid sequence that can bind to and/or has affinity for an envelope protein of a virus and that is cross-blocked or is cross blocking a Nanobody® of the invention, e.g. one of SEQ ID NO's: 60-76,138-141 and 146-157 (Table A-4), or a polypeptide or construct comprising at least one Nanobody® of the invention, e.g. a polypeptide or construct comprising at least one of SEQ )D NO: 77-99,142-145 and 158-165 (see Table A-5); and c. isolating said nucleic add sequence, followed by expressing said amino acid sequence.

Aspect R-l: Method for the prevention and/or treatment of hRSV infection, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino acid sequence according to any of aspects A-l to A-29, C-l to C-30 and W-l to W-3S, Nanobody*1 according to any of aspects B-l to B-18, ΟΙ to D-38 and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovalent construct according to any of aspects F-l to F-4 and/or composition according to aspects 0-2 to 0-3.

Aspect R-2: Method for the prevention and/or treatment of at least one of respiratory itiness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-2 to W-3S, Nanobody0 according to any of aspects B-l to B-1S,D-1 to D-38 and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovalent construct according to any of aspects F-l to F-4 and/or composition according to aspects 0-1 to 0-3.

Aspect 8-3: Method for the prevention and/or treatment of at least one disease or disorder that can be prevented and/or treated by administering, to a subject in need thereof, an amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, a Nanobody® according to any of aspects B-l to B-18,0-1 to D-38 and X-l to X-38, a polypeptide according to any of aspects E-l to E-271, a compound or construct according to any of aspects G-l to G-20, a monovalent construct according to any of aspects F-l to F-4 and/or a composition according to aspects 0-1 to 0-3, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino add sequence according to any of aspecis A-l to A-29, C-l to C-38 and W-l to W-38, Nanobody® according to any of aspects B-l to B-18, ΟΙ to D-38 and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovalent construct according to any of aspects F-l to F-4 and/or composition according to aspects 0-1 to 0-3.

Aspect R-4: Method for immunotherapy, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of at least one amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, Nanobody* according to any of aspects B-l to B-1S,D-1 to D-38 and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovalent construct according to any of aspects E-l to f-4 and/or composition according to aspects 0-1 to 0-3.

Aspect R-5: Use of an amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, a Nanobody® according to any of aspects B-l to 6-18, D-l to D-3S and X-l to X-38, a polypeptide according to any of aspects E-l to E-271, a compound or construct according to any of aspects G-l to G-20, a monovalent construct according to any of aspects F-l to F-4 and/or composition according to aspects 0-1 to 0-3 in the preparation of a pharmaceutical composition for prevention and/or treatment of hRSV infection; and/or for use in one or more of the methods according ίο aspects R-l to R-4.

Aspect R-6: Amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38, polypeptide according to any of aspects E-l to E-271, compound or construct according to any of aspects G-l to G-20, monovalent construct according to any of aspects F-l to F-4 and/or composition according to aspects 0-1 to 0-3 for prevention and/or treatment of at least one of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma.

Aspect S-l: Part or fragment of an amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38, a Nanobody* according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38, and/or a polypeptide according to any of aspects E-l to E-271.

Aspect S-2: Part or fragment according to aspect S-l, that can specifically bind to antigenic il on protein F of hRSV and/or competes with Synagis® for binding protein F of hRSV.

Aspect S-3: Part of fragment according to any of aspects S-l to S-2, that can specifically bind to protein F of hRSV with a dissociation constant (K0) of 1000 nM to I nM or less, preferably 100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

Aspect S-4: Part or fragment according to any of aspects S-2 to S-3, that can specifically bind to protein F of hRSV with a kon-rate of between 104 M'Y" to about 107 M'J$'v preferably between 105 M'V1 and 10' M'V*, more preferably about 106 M'V1 or more.

Aspect S-5: Part or fragment according to any of aspects S-2 to S-4, that can specifically bind to protein F of hRSV with a k0(f rate between 10'J s'1 (t1/2=0.69 s) and 1Q~ s'~ (providing a near irreversible complex with a ti/2 of multiple days), preferably between 101 s'* and IG'4 s1, or lower.

Aspect S-6: Compound or construct, that comprises or essentially consists of one or more parts or fragments according to any of aspects S-l to S-5, and optionally further comprises one or more other groups, residues, moieties or binding units, optionally linked via one or more linkers.

Aspect S-7; Compound or construct according to aspect S-6, in which said one or more other groups, residues, moieties or binding units are amino acid sequences.

Aspect S-8: Compound or construct according to aspects S-5 or S-7, in which said one or more linkers, if present, are one or more amino acid sequences.

Aspect S-9; Nucleic acid or nucleotide sequence, that encodes a part or fragment according to any of aspects S-l to S-5 or a compound or construct according to any of aspects S-6 to S-8.

Aspect S-10: Composition, comprising at least one part or fragment according to any of aspects S-1 to S-5, compound or construct according to any of aspects S-6 to S-8, or nucleic acid or nucleotide sequence according to aspect S-9.

Aspect T-l: Derivative of an amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 or of a Nanobody® according to any of aspects B-l to B-18, D-l to D-3S and X-l to X-38.

Aspect T-2: Derivative according to aspect T-l, that can specifically bind to antigenic site II on protein F of hRSV and/or compete with Synagis® for binding protein F of hRSV.

Aspect T-3: Derivative according to any of aspects T-l to T-2, that can specifically bind to protein F of hRSV with a kor,-rate of between 104 μΎ* to about 10' M'Y\ preferably between 10s MY1 and 107 M‘V', more preferably about 10° M'V" or more.

Aspect T-4: Derivative according to any of aspects T-2 to T-2, that can specifically bind to protein F of hRSV with a k^-rate of between 104 Μ'Ύ to about 107 M'Y', preferably between 105 Μ Y1 and 107 IViY'1, more preferably about IC6 M'Y1 or more.

Aspect T-5: Derivative according to any of aspects T-2 to T-4, that can specifically bind to protein F of nRSV with a koS rate between 10'2 s'1 (t1/2=0.69 s) and 10"’ s'' (providing a near irreversible complex with a tyi of multiple days}, preferably between IQ'3 s'4 and 1G'4 s‘l, or lower,

Aspect T-6: Derivative of a compound or construct according to any of aspects 6-1 to G-20or a polypeptide according to any of aspects E-l to E-271.

Aspect T-7: Derivative according to aspect T-S, that can specifically bind to antigenic site II on protein F of hRSV and/or compete with Synagis® for binding protein F of hRSV.

Aspect T-S: Derivative according to any of aspects T-6 to T-7, that can specifically bind to protein F of hRSV with a dissociation constant (K[>) of 100 nsVt to 0.1 nM or less, preferably 10 nM to 0.1 nM or less, more preferably 1 nM to 0,1 nM or less.

Aspect T-9: Derivative according to any of aspects T-6 to T-S, that can specifically bind to protein F of hRSV with a k0„-rate of between 104 M‘Y" to about 107 M'Y1, preferably between 10’ M'Y1 and 107 M'Y1, more preferably about ID6 M'Y1 or more.

Aspect T-10: Derivative according to any of aspects T-6 to T-9, that can specifically bind to protein F of hRSV with a kaff rate between 10'2 s'1 (ti/2=0.69 s) and 10'4 s'1 {providing a near irreversible complex with a tj# of multiple days}, preferably between 103 s'1 and ίο-s'1, more preferably between 5xl0'3 s'" and 10"4 s‘J, or lower.

Aspect T-ll: Derivative according to any of aspects T-6 to T-10, that can neutralize bRSV, e.g. in a microneutralization assay of RSV strain Long (such as e.g. described in Example 6), with an iC50 value between 10 pM and 1000 pM, preferably between 10 pM and 250 pM, more preferably between 50 pM and 200 pM or less.

Aspect T-12: Derivative according to any of aspects T-6 to T-ll, that can neutralize hRSV, e.g. in a microneutralization assay of RSV strain tong (such as e.g. described in Example 6), with an IC50 value that is at least the same and preferably better, at least ten times better, preferably twenty times better, more preferably fifty times better, even more preferably sixty, seventy, eighty or more times better compared to the IC50 value obtained with Synagis®.

Aspect T-13; Derivative according to any of aspects T-l to T-12, that has a serum half-iife that is at least 1.5 times, preferably at least 2 times, such as at least 5 times, for example at least 10 times or more than 20 times, greater than the half-life of the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-l to W-38 per se. Nanobody® according to any of aspects 8-1 to B-18, D-l to D-38 and X-l tc X-38 per se, polypeptide according to any of aspects E-l to E-261, compound or construct according to any of aspects G-l to G-20 per se, or monovalent construct according to any of aspects F-l to F-4 per se, respectively.

Aspect T-14: Derivative according to any of aspects T-l to T-13, that has a serum half life that is increased with more than 1 hours, preferably more than 2 hours, more preferably more than 6 hours, such as more than 12 hours, or even more than 24,48 or 72 hours, compared to the corresponding amino acid sequence according to any of aspects A-l to A-29, C-l to C-38 and W-i to W-38 per se, Nanobody® according to any of aspects B-l to B-18, D-l to D-38 and X-l to X-38 per se, polypeptide according to any of aspects E-l to E-261, compound or construct according to any of aspects G-1 to G-20 per se, or monovalent construct according to any of aspects F-l to F-4 per se, respectively.

Aspect T-15: Derivative according to any of aspects T-l to T-14, that has a serum half-iife in human of at least about 12 hours, preferably at least 24 hours, more preferably at least 48 hours, even more preferably at least 72 hours or more; for example, at least 5 days (such as about 5 to 10 days), preferably at least 9 days (such as about 9 to 14 days), more preferably at least about 10 days (such as about 10 to 15 days), or at least about 11 days (such as about li to 15 days), more preferably at least about 12 days (such as about 12 to 18 days or more), or more than 14 days (such as about 14 to 19 days).

Aspect T-16: Derivative according to any of aspects T-l to 7-15, that is a pegylated derivative.

Aspect T-17: Compound or construct, that comprises or essentially consists of one or more derivatives according to any of aspects T-l to T-16, and optionally further comprises one or more other groups, residues, moieties or binding units, optionally linked via one or more linkers.

Aspect T-18: Compound or construct according to aspect T-17, in which said one or more other groups, residues, moieties or binding units are amino add sequences.

Aspect 7-19; Compound or construct according to aspects T-17 or T-18, in which said one or more linkers, if present, are one or more amino acid sequences.

Aspect T-20: Nucleic acid or nucleotide sequence, that encodes a derivative according to any of aspects T-l to T-16 or a compound or construct according to any of aspects T-17 to T-19.

Aspect T-21: Composition, comprising at least one derivative according to any of aspects T-l to I-16, compound or construct according to any of aspects T-17 to T-19, or nucleic acid or nucleotide sequence according to aspect T-20.

Aspect U-l: A method for administering an effective amount of an amino acid sequence according to any of claims A-l to A-29, C-l to C-3S and W-l to W-38, a Nanobody* according to any of claims S-l to B-18, D-l to D-38 and X-l to X-3S, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims 6-1 to G-20 and/or a monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same, wherein said method comprises the step of administering the amino acid sequence according to any of claims A-l to A-29,C-l to C-38 and W-l to W-38, the Nanobody® according to any of ctaims B-l to B-18,0-1 to D-33 and X-l to X-38, the polypeptide according to any of claims E-l to E-271, the compound or construct according to any of claims G-l to 6-20 and/or the monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same to the pulmonary tissue.

Aspect U-2: The method according to aspect u-1, wherein the amino 3Cid sequence according to any of claims A-l to A-29, C-l to C-38 and W-l to W-38, the Nanobody® according to any of claims B-l tc 6-18,0-1 to D-38 and X-l to X-3S, the polypeptide according to any of claims E-l to c- 271, the compound or construct according tc any of claims G-l to G-20 and/or the monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same is administered by use of an inhaier, intranasa! delivery device or aerosol.

Aspect U-3: Method according to any of aspects U-1 or U-2, wherein at least 5%, preferably at least 10%, 20%, 30%, 40%, more preferably at ieast 50%, 60%, 70%, and even more preferably at least S0% or more of the amino acid sequence according to any of claims A-l to A-29, C-l to C-38 and W-l to W-38, the Nanobody® according to any of claims B-l to B-18, D-l to 0-38 and X-l to X-38, the polypeptide according to any of claims E-l to E-271, the compound or construct according to any of claims G-l to G-20 and/or the monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same is stable in the pulmonary tissue for at ieast 24 hours, preferably at least 48 hours more preferably at ieast 72 hours.

Aspect u-4: Method according to any of aspects U-1 to U-3, wherein the amino add sequence according to any of claims A-l to A-29,C-l to C-38 and W-l to W-38, the Nanobody® according to any of claims B-l to B-18,D-1 to D-38 and X-l to X-38, the polypeptide according to any of claims E-l to E-271, the compound or construct according to any of claims G-l to G-20 and/or the monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same are applied in pure form, i.e„ when they are liquids or a dry powder.

Aspect U-5: Method according to any of aspects U-1 to U-3, wherein the amino acid sequence according to any of claims A-l to A-29,C-l to C-38 and W-l to W-38, the Nanobody® according to any of claims B-l to 8-18,D-l to D-38 and X-l to X-38, the polypeptide according to any of claims E-l to E-271, the compound or construct according to any of claims G-l to G-20 and/or the monovalent construct according to any of claims F-l to F-4, and/or a composition comprising the same are administered to the pulmonary tissue as composition orformuiation comprising an amino acid sequence according to any of claims A-l to A-29,C-2 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B-18,D-1 to D-38 and X-l to X-3S, a polypeptide according to any of claims E-i to £-271, a compound or construct according to any of claims G-l to G-20 and/or s monovalent construct according to any of claims F-l to F-4, and a carrier suitable for pulmonary delivery.

Aspect U-6: Pharmaceutical composition comprising an amino acid sequence according to any of claims A-l to A-29,C-1 to C-38 and W-l to W-38, a Nanobody®' according to any of claims B-l to to D-38 and X-l to X-38, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4, and a carrier suitable for pulmonary delivery.

Aspect U-7: Pharmaceutical device suitable for the pulmonary delivery of an amino acid sequence according to any of claims A-l to A-29.C-1 to C-38 and W-l to W-38, a Nanobody6 according to any of claims B-l to B-18,D-lto D-38 and X-l to X-38, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4 and/or suitable in the use of a composition comprising the same.

Aspect U-8: Pharmaceutical device according to aspect U-7 that is an inhaler for liquids (e.g. a suspension of fine solid particles or droplets} comprising an amino acid sequence according to any of claims A-l to A-29,C-1 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B-18,D-1 to D-38 and X-l to X-38, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of ciaims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4.

Aspect U-9: Pharmaceutical device according to aspect U-7 that is an aerosol comprising an amino acid sequence according to any of ciaims A-l to A-29,C-1 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B-18,D-1 to D-38 and X-l το X-38, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4.

Aspect U-10: Pharmaceutical device according to aspect U-7 that is a dry powder inhaler comprising an amino acid sequence according to any of claims A-i to A-29,C-1 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B-18,D-1 to D-38 and X-l to X-3S, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims G-l to G-20 and/or a monovalent construct according to any of claims F-2 to F-4 in the form of a dry powder.

Aspect U-ll: Method for the prevention and/or treatment of hRSV infection, said method comprising administering to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of an amino acid sequence according to any of ciaims A-l to A-29,C-1 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B- 18,D-1 to D-38 and X-i to X-33, a polypeptide according to any of claims E-I to E-271, a compound or construct according to any of ciaims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4 and/or of a pharmaceutical composition comprising the same.

Aspect U-12: Method for the prevention and/or treatment of respiratory tiiness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma, said method comprising administering to the pulmonary tissue of a subject in need thereof, a pharmaceutically active amount of an amino acid sequence according to any of claims A-I to A-29,C-1 to C-38 and W-l to W-38, a Nanobody® according to any of claims B-l to B-1S,D-1 to D-38 and X-l to X-3S, a polypeptide according to any of claims E-l to E-271, a compound or construct according to any of claims G-l to G-20 and/or a monovalent construct according to any of claims F-l to F-4, and/or of a pharmaceutical composition comprising the same.

Aspect V-l: Method for the prevention and/or treatment of hRSV infection, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a multivalent polypeptide according to any of aspects E-7 to E-261, and/or of a pharmaceutical composition comprising the same.

Aspect V-2: Use of a multivalent poiypeptide according to any of aspects E-7 to E-252, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization of hRSV.

Aspect V-3: Use of a multivalent poiypeptide according to any of aspects £-7 to E-251, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization of different strains of hRSV.

Aspect V-4: Use of a multivalent polypeptide according to any of aspects E-7 to E-261, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization of one or more escape mutants of a virus,

Aspect V-5: Method or use according to any of aspects V-i to V-4, wherein the multivalent polypeptide is bivalent.

Aspect V-6: Method or use according to any of aspects V-l to V-4, wherein the multivalent polypeptide is trivalent.

Aspect V-7; Method or use according to any of aspects V-i to V-6, wherein said multivalent polypeptide is administered according to any of the methods of claims U-l to U-5 and/or u-11 to u-12.

Aspect V-S: Method for the prevention and/or treatment of infection by hRSV virus, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a multivalent polypeptide according to any of aspects E-7 to E-261 and/or of a pharmaceutical composition comprising the same.

Aspect V-9: Method according to aspect V-S wherein the multivalent compound or construct is selected from Table A-5 {SEQ. ID NO's: 77-99,138-141 and 146-1S7).

Aspect V-10: Method according to any of aspects V-8 or V-9, wherein infection by one or more RSV escape mutants is treated.

Aspect V-ll: Method according to aspect V-10, wherein the escape mutant is an escape mutant specific for antigenic site II.

Aspect V-12: Use of a multivalent compound or construct according to any of aspects E-7 to E-26I, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization one or more different escape mutants of RSV.

Aspect V-13: Use according to claim V-12 wherein the escape mutant is an escape mutant specific for antigenic site I!.

Aspect V-14: Method according to any of aspects V-E or V-9, wherein infection by one or more strains of hRSV is treated.

Aspect V-15: Method according to aspect V-14. wherein the RSV strain is Long.

Aspect V-16: Method according to aspect V-14, wherein the RSV strain is A-2.

Aspect V-17: Method according to aspect V-14, wherein the RSV strain is B-l.

Aspect V-18: Method according to aspect V-14, wherein the multivalent poiypeptide binds and/or neutralizes RSV strain Long and A-2.

Aspect V-19: Method according to aspect V-14, wherein the multivalent polypeptide binds and/or neutralizes RSV strain Long and B-l.

Aspect V-20: Method according to aspect V-14, wherein the multivalent polypeptide binds and/or neutralizes RSV strain B-l and A-2.

Aspect V-21: Method according to aspect V-14, wherein the multivalent polypeptide binds and/or neutralizes RSV strain Long, A-2 and B-l.

Aspect V-22: Use of a multivalent compound or construct according to any of aspects E-7 to E-261, and/or of a pharmaceutical composition comprising the same for binding and/or neutralization different strains of hRSV.

Aspect V-23: Use according to aspect V-22, wherein the strains of RSV are Long and A-2.

Aspect V-24: Use according to aspect V-22, wherein the strains of RSV are Long and B-l.

Aspect V-25: Use according to aspect V-22, wherein the strains of RSV are A.-i and B-l.

Aspect V-25: Use according to aspect V-22, wherein the strains of RSV are Long, A-2 and B-l,

EXAMPLES

Example 1: immunizations

Two llamas (156 and 157) were immunized according to standard protocols with 5 boosts of hRSV rTi/-(membrane anchorless form of the fusion protein, 70 kDa; Corral! T. eta!. 2007, BMC Biotechnol. 7:17). Blood was collected from these animals? days after boost 6 and 10 days after boost 6.

Two llamas (212 and 213) were immunized intramuscularly in the neck with 1 mg of RNA-inactivated RSV strain long A (Hytest, Turku Finland; #8RSV79), followed by 4 boosts of 0.5 mg RSV in a biweekly regimen. Two llamas (206 and 207) were immunized intramuscularly with 1 mg of RNA-inactivated RSV strain iong A, boosted with 0.25 rng of RSV after 2 weeks, followed by 3 boosts with 50 pg of recombinant hRSV FTM-NN (membrane anchorless form of the fusion protein, 70 kDa: Corral et al. 2007; BMC Biotechnol. 7:17} in a biweekly regimen. For aii immunizations the antigens were prepared as oil-PBS emulsions with Stimune as adjuvant. Blood was collected from these animals 4 days and 10 days after the fourth immunization, while also a Lymph node biopsy was taken 4 days after the fourth immunization. For the Nanoclone procedure, 100 mL blood was collected 11 days after the final boost from llamas 206 and 207.

Example 2; Library construction

Peripheral blood mononuclear cells were prepared from blood samples using Ficoll-Hypaque according to the manufacturer's instructions. Next, total RNA was extracted from these cells as well as from the lymph node bow celis and used as starting material for RT-PCR to amplify Nanobody* encoding gene fragments. These fragments were cloned into phagemid vector derived from pUC119 which contains the LacZ promoter, a coiiphage pill protein coding sequence, a resistance gene for ampicilitn or carbeniciliin, a multicloning site and the gen3 leader sequence, in frame with the Nanobody6 coding sequence, the vector codes for a C-terminal c-myc tag and a (His)6 tag. Phage was prepared according to standard methods and stored at 49C for further use, making phage libraries 156,157, 206, 207,212 and 213.

Example 3: Nanobody* selection with the F-protein of hRSV

To identify Nanobodies® recognizing the fusion protein of RSV, libraries 156,157, 206, 207, 212 and 213 were used for selection on FIM.NN (membrane anchorless form of the Long fusion protein, 70 kDa,; Corral T. et al. 2007, BMC Biotechnol. 7:17), The FTtr protein (25 ng/well) was immobilized on Nunc Maxisorp ELISA plates. A control was included with 0 pg/ml FTiV1-. Bound phages were eluted from the FTM- using trypsin and Synagis* (Paiivizumab, Medlmmune, humanized monoclonal antibody/ described in Zhao and Suilender 2005, J. Virol. 79: 3962) in the first and second round of seiections. Remicade (Infliximab, anti-INF; Centocor) was used as a control for Synagis®. A 100 molar excess of Synagis® was used in order to identify Nanobodies® binding specifically at the Synagis®1 binding site on RSV. Outputs from the first round selections, eiuted with Synagis® were used for second round seiections.

In addition, seiections were done using inactivated hRSV strain Long (Hytest #8RSV79) The Ftm-NN protein (25 ng/weli) or RSV (5 to 50 pg/well) was immobilized on Nunc Maxisorp ELISA plates, next to a control with 0 pg/ml antigen. Bound phages were eiuted from the FTM-NN using trypsin, Synagis® (Palivizumab, humanized monoclonal antibody, described in Zhao and Suilender 2005, j. Virol. 79:396), or 101F Fab (WO 06/050280, humanized monoclonal antibody) in the first round of selection. Outputs from the first round seiections eluted with Synagis® or 1G1F Fab were used for second round selections, using either Numax Fab (Motavizumab or MEDI-524, a third-generation humanized monoclonal antibody product evolved from palivizumab; WO 06/050166), Synagis® or 1Q1F Fab for elution. Remicade (infliximab, anti-TNF, see also WO 09/068625) was used as a control for Synagis®, while Omnitarg Fab (anti-Her2; in-house produced) served as control for Numax Fab and 101F Fab. A 100 moiar excess of Synagis®, Numax Fab or 101F Fab was used in order to identify Nanobodies® binding specificatiy to antigenic sites li or iV-VI epitopes on the RSV F-protein. To obtain Nanobodies® specific for the antigenic site IV-VI. second round selections were performed using two biotinylated peptides: at first, a peptide comprising residues 422-436 of the F-Drotein (Long) (Abgent, San Diego, CA) encompassing the 101F binding epitope (Wu et al. 2007, j. Gen. Viroi. 88: 2719-2723), secondly, a peptide mimic of the epitope of Mabl9 (HWSISKPQ-PEG4-K-biotin)(Chargelegue et al. 1998, J. Virol.72: 2040-2056).

Outputs of both rounds of selections were analyzed for enrichment factor (phage present in eluate relative to controls). Based on these parameters the best selections were chosen for further analysis, individual colonies were picked and grown in 96 deep well plates (1 ml volume) and induced by adding 1PTG for Nanobody® expression. Peripiasmic extracts (volume: ~ 80 pi) were prepared according to standard methods.

For testing of selected clones in RSV neutralization assays, periplasmatic extracts from 10 ml cultures were partially purified by using 1MAC PhvTips (Pnynexus Inc, San Jose, CA). In here 800 pi of periplasmatic extracts was loaded onto Phytips 200+ columns prepacked with immobilized metal affinity chromatography resin, followed by elution of His-tagged Nanobodies® in 30 pi of G.1M glycine-HCI/0.15fv1 NaCl (pH3), after which eluates were neutralized with 5 pi of 0.5 M Tris-HC! pH8.5.

Example 4: Nanobody® selection with Ftm-NN of RSV using Nanocione technology

Peripheral blood mononuclear cells (PBMCs) were prepared from blood samples using Ficoll-Hypaque according to the manufacturer's Instructions. Antigen specific B-cells expressing heavy chain antibodies on their surface were isolated from the PBMCs via FACS sorting {for s description of the Nanocione technology reference is made to WO 06/079372). Thereto, FWt- NN protein was labeled with Aiexa Fluor 488 dye (Invitrogen, Carlsbad, CA; cat. nr. A20000) and subsequently desalted to remove residual ηοη-conjugated Aiexa Fluor 488 dye according to the manufacturer's instructions.

Pre-immune (background control) and immune PBMC of a llama were stained with fluorescent dye conjugated IgGl (conventional heavy+light chain immunoglobulins), lgG2-and IgGB (heavy chain immunoglobulin classes) specific mouse monoclonal antibodies, fluorescently labeled DH59B antibody (CD172a) (VMRD, Inc. Pullman, WA; Cat No. DH5SB; Davis et al. 1987, Vet. Immunol. Immunopathol. 15: 337-376) and Aiexa 48S labeled antigen. T0PR03 was included as a iive/dead ceil discriminator dye. IgGl-f 8-lymphocytes, monocytes, neutrophils and dead celts were gated out and therefore rejected from sorting. Antigen-specific (A488-r) |gG2- or !gG3 positive B cells were single cell sorted individually into separate PCR plate welis containing RT-PCR buffer.

For liama 206,1.9 % antigen positive cells of the total amount of igG2/lgG3 positive living cells was obtained (1.0% in pre-immune reference sample), for llama 207 4.2% positive cells were obtained (0.7% in pre-immune reference sample). Heavy chain variable region genes were amplified directly from these B-cells by single-cell RT-PCR and nested PCR. PCR products were subsequently cloned into a TOPO-adapted expression vector derived from pUC119 which contained the LacZ promoter, a resistance gene for ampiciliin or carbenicillin, a multicloning site and the gen3 leader sequence. In frame with the Nanobody* coding sequence, the vector coded for a C-terminal c-myc tag and a (His)6 tag. The cloned constructs were transformed in TOP10 Escherichia coli cells via high throughput electroporation. Single clones were grown in 96 deep well plates (1 ml volume) and induced by adding IPTG for Nanobody® expression. Periplasmic extracts (volume: 80 μΙ) were prepared via osmotic shock and analyzed for binding to FTM- in a binding ELISA. in short, 2 pg/m! of FTM-was immobilized directly on Maxisorp microtiter plates (Nunc). Free binding sites were blocked using 4% Marvel in PBS. Next. 10 μΙ of periplasmic extract containing Nanobody® of the different clones in 100 μΙ 2% Marvel PBST were allowed to bind to the immobilized antigen. After incubation and a wash step. Nanobody® binding was revealed using a rabbit-anti-VHH secondary antibody (for the periplasmic fractions). After a wash step the Nanobodies®' in the periplasmic fractions were detected with a HRP-conjugated goat-anti-rabbit antibody. Binding specificity was determined based on OD values compared to controls having received no Nanobody®.

In total, 8 positive F™- NN binders (4 from llama 206,4 from llama 207) were obtained out of 52 cloned VHHs.

Example 5: Screening for Nanobodies® that bind to antigenic site II or IV-Vi

Peripiasmic extracts containing single Nanobodies® were analyzed for binding to the antigen site II or IV-VI, using an Aiphascreen® assay (Perkin timer; Waltham, MA)(Garcia-Barreno et al. 1989, j. Virol. 63: S25-9B2; Lopeze et a!. 1998, J. Virol. 72: 6922-6928). In this setup FTy- NN is bound simultaneously by Fabs of Synagis® and 101F, allowing detection of Nanobodies® that interfere with binding of each of the respective antigenic sites II and IV-VI. In here, peripiasmic extracts were added to Ftm-NN protein (0.3 nM) and incubated for 15 minutes. Subsequently biotinylated Fab Synagis® (0.3 nM) and Fab 101F conjugated acceptor beads (10 pg/ml) were added and this mixture was incubated for 1 hour. Finally streptavidin-coated donor beads (10 pg/m!) were added and after 1 hour incubation the plate was read on the Envision micropiate reader. Peripiasmic extracts were diluted 25-foid which corresponds roughiy to a final concentration of 40 nM. The assay was validated by titration of the known competitors of Synagis*', mabs 18B2 (Argene, Varilhes, France; 18042 N1902) and 2F7 (Abeam, Cambridge, UK; ab438l2). Also Synagis® Fab, Numax Fab, and 101F Fab were analyzed, with Numax Fab having the lowest IC50 vaiue (8.6 £-11 M) followed by Synagis® Fab (5.97 E-10 M) and 101F Fab (1.12 E-9 M). For the screening of periplasmatic extracts (at 1/25 dilution) both Numax Fab (40 nM) and 101F Fab (40 nM) were used as positive controls, while irrelevant periplasmatic extracts served as negative controls. Clones that interfered with binding to Ftm-NN protein in the Aiphascreen® more than 75% relative to the negative controls were identified as hit. in total 341 hits were identified out of 1856 clones, derived from all 6 llamas but the majority coming from llamas 206 and 207. In addition, out of 8 clones obtained from Nanoclone selections 3 clones showed competition.

The correct antigen site (II or IV-VI) of the competitors was deconvolved by means of 3 competition ELISA with biotinylated Synagis® Fab (2 nM) or biotinylated 101F Fab (3 nM) for binding to Ftm'-NN protein ¢1 pg/ml). In short, the fTM- NN protein was immobilized on Maxisorp microtiter plates (Nunc) and free binding sites were blocked using 4% Marvel in PBS. Periplasmatic extracts were diluted 1/10 and mixed with the biotinylated Fsb prior to binding to the immobilized FrM- NN protein. Control peripiasmic fractions selected against other viral coat proteins were included. The competing antibody was allowed to bind to the immobilized antigen with or without Nanobody®. After incubation and a wash step, detection occurred via Extravidin-HRP conjugated secondary antibodies (Sigma-Aldrich, St. Louis, MO; Cat. No. E2886). Binding specificity was determined based on OD vaiues compared to controls having received no Nanobody®.

All hits were subjected to sequence analysis and classified into families according to their CDR3 sequences (see Table C-4 and A-l in PCT application PCT/EP2009/056975 entitled "Amino add seauencss directed against envelope proteins of a virus and polypeptides comprising the same for the treatment of viral diseases" filed by Ablynx N.V on 5 June 2009).

Example 6: Screening for RSV neutralizing Nanobodies®

From all six hRSV libraries 163 unique sequences (160 identified from phage libraries, 3 derived from Nanocione) were analyzed for RSV Long neutralizing capacity in s micro-neutralization assay as partially purified proteins. Hep2 cells were seeded at a concentration of 1.5 x 10' cells/well into 96-well plates in DMEM medium containing 10% fetal calf serum (FCS) suppiemenced with Penicillin and Streptomycin (100 U/ml and 100 pg/ml, respectively) and incubated for 24 hours at 37“C in a 5% C02 atmosphere. The virus stock used is referred to as hRSV strain long, Long LM-2 and Long M2 (used interchangeably) and is a virus stock derived from ATCC VR-2S of which the sequence of the F protein corresponds to P12568 or M22643. The virus stock has been passaged several times from the ATCC stock. The sequence of the F-protein was confirmed to be identical to P12568 (see example 9). A standard quantity of hRSV strain Long LM-2 was pre-incubated with serial dilutions of a fixed volume of Phytips purified Nanobodies35 (20 pi) in a total volume of 50 pi for 30 minutes at 37SC. The medium of the Hep2 cells was replaced with the premix to allow infection for 2 hours., after which 0.1 ml of assay medium was added. The assay was performed in DMEM medium supplemented with 2.5 % fetal calf serum and Penicillin and Streptomycin (lOOU/ml and 100 pg/ml, respectively). CeSis were incubated for an additional 72 hours at 37eC in a 5% C02 atmospnere. after which cells were washed twice with 0.05% Tween-20 in PBS and once with PBS alone, after which the cells were fixed with 80 % cold acetone (Slgma-Aldrich, St. Louis, MO) in PBS (100 pl/well) for 20 minutes at 4“C and left to dry' completely. Next the presence of the F-protein on the cell surface was detected in an ELISA type assay. Thereto, fixed Hep2 cells were blocked with 2% Bovine Serum Albumin (BSA) solution in PBS for 1 hour at room temperature, than incubated for 1 hour with Synagis® (2 pg/ml). For detection goat Anti-Human IgG, Fey fragment specific-HRP (Jackson ImmunoResearch, West Grove, PA) was used, after which the ELISA was developed according to standard procedures.

In addition to the previously identified RSV neutralizing Nanobodies® 191D3 (SEQ ID NO: 9) and 192C4 {SEQ ID NO: 11), which were included as positive controls in the screening, 5 antigenic site I! clones showed strong RSV Long neutralizing activity: 1E4 (also referred to as 2Q7D1; SEQ ID NO: 1), 7B2 (SEQ ID NO: 2), NC23 (SEQ ID NO: 3), and two members of the same family 15H8 (SEQ ID NO: 4) and NC41 (SEQ ID NO: 5) (Table A-l). None of the antigenic site 1V-VI specific Nanobodies® showed more than very weak neutralizing activity for hRSV Long LM-2 strain.

Example 7: Production of hRSV Nanobodies®

In addition to the previously identified RSV neutralizing Nanobodies® 191D3 {SEQ ID NO: 9) and I91E4 (SEQ ID NO: 10), which were included as positive controls in the screening, five new neutralizing Nanobodies® selected from the screening described above (1E4,7B2,1SH8, NC23 and NC41) as well as 1 antigenic site IV-VI Nanobodies® (15B3; SEQ ID NO: 7) were expressed, purified and further characterised. Thereto the encoding sequences were recloned in an expression vector derived from pUCH9 which contained the LacZ promoter, a resistance gene for kanamycin, a multicloning site and the OmpA signal peptide sequence. In frame with the Nanobody® coding sequence, the vector coded for a C-terminal c-myc tag and a (His)6 tag. expression occurred in E. coli TG-1 cells as c-myc, Hrs6-tagged proteins in a culture volume of 1 L Expression was induced by addition of 1 mM IPTG and allowed to continue for 3 hours at 37£C. After spinning the ceil cultures, periplasmic extracts were prepared by freeze-thawing the peliets and resuspension in dPBS. These extracts were used as starting material for immobilized metal affinity chromatography (IMAC) using Histrap FF crude columns |GE healthcare, Uppsala, Sweden). Nanobodies® were eluted from the column with 250 mM imidazoie and subsequently desalted towards dPBS.

Example 8: Characterization of hRSV Nanobodies®

Binding to F-protein in ELISA

All purified Nanobodies® were shown to bind to the F-protein in a binding ELISA to F7W- NN protein and to hRSV. Results for hRSV binding are shown in Table B-l. In short, 1 pg/ml of FTM- NN or 5 pg/ml hRSV (Hytest Turku, Finland) were immobilized directly on Maxisorp microtiter plates. Free binding sites were blocked with 1% casein. Serial dilutions of purified Nanobodies® were allowed to bind the antigen for 1 hour. Nanobody® binding was revealed using a rabbit-anti-VHH secondary antibody, and final detection with a HRP-conjugated goat-anti-rabbit antibody. Binding specificity was determined based on OD values compared to irrelevant Nanobody® controls.

Binding to F-protein in Biacore

To determine the precise binding affinities of the purified Nanobodies®, a kinetic analysis was performed using Surface Piasmon resonance analysis on the FTnrNN protein. For preincubation of the Sensorchip CMS, 10 pg/ml hRSV F7M- protein was left on for 120 seconds. For immobilization by amine coupling, EDC/NHS was used for activation and ethanolamine HCI for deactivation (Biacore, amine coupling kit), 100 nM Synagis® was added and then 100 nM of the Nanobodies®. Evaluation of the off-raies was performed by fitting a 1:1 interaction model {Langmuir binding model) by Biacore T100 software vl.l. The off-rates and affinity constants are shown in Table B-l.

Competition with SvnaGisft

The ability of purified Nanobodies® to compete with Synagis® Mab or biotinylated Synagis® Fab for binding to FmrNN was determined in competition EUSA following the procedure as essentially described in example 5. Figure 1 shows a representative example of a competition ELISA wherein purified Nanobodies® compete with biotinylated Synagis® Fab for binding to FTM-NN. EC5Q values are summarized in Table B-l.

Example 9: in vitro micro neutralization of distinct hRSV strains

The potency of purified Nanobodies® in neutralization of different type A and B RSV strains was tested by the in vitro micro neutralization assay (see Example δ). Viral stocks of RSV Long LM-2 {Accession No. P1256S; ATCC VR-26), RSV A-2 (ATCC VR-1540; lot nr. 319SS40) and RSV B-l (ATCC VR-1580; tot nr. S271356) were prepared into Hep2 cells and subsequently titrated to determine the optimal infectious dose for use in the micro neutralization assay. Results of neutralization potencies of the different purified Nanobodies® are shown in Table B-l. While all six Nanobodies® that recognize the Synagis® epitope could efficiently neutralize type A strains Long and A-2, they failed to neutralize infection with the B-l strain or did so at concentrations > 1 μΜ, The 101F competitors 15B3 and 191E4 showed very weak neutralization potency on the B-l strain only when administrated at μΜ concentrations.

The sequences of the respective F-proteins of the different RSV strains were verified by means of reverse-transcriptase PCR and subsequent sequence analysis. Briefly, total RNA was isolated from RSV-infected Hep2 cells using RNeasy mini kit (Qiagen, Venlo, Netherlands), after which complementary DNA was prepared using Superscript III reverse transcriptase kit (Invitrogen, Carlsbad, CA). The F-protein of RSV A strains was amplified and sequenced using the primers described in Kimura et al. 2004 (Antiviral Research 61; 165-171). For amplification of the RSV B-I strain F-protein the following primers were used: FBl_outer_for: cttagcagsaaaccgtga (SEQ ID NO: 13); FBl„outer_rev: tgggttgatttgggattg (SEQ ID NO: 14); FBl_seq_1123-for: ggactgatagaggatggta {SEQ ID NO: 15); FBl_seq_1526-rev: gctgacttcacttggtaa (SEQ ID NO: 16). The sequence of RSV B-l strain corresponded to Accession nr P13843, with an additional point mutation Ser540Leu. The sequence for the RSV Long M2 strain corresponded completely to the reported sequence (Accession nr M22643). The sequence for the strain RSV A-2 corresponded to Accession M11486. See also Table A-2.

Example 10: Construction, production and characterization of multivalent hRSV Nanobodies®

Multivalent Nanobody® constructs connected by Gly-Ser linkers of different lengths and composition were generated by means of separate PCR reactions (1 for the N-terminal, 1 for the middle {in case of trivaient) and 1 for the C-terminal Nanobody®' subunit) using different sets of primers encompassing specific restriction sites. Similarly, muttivaient constructs connected by Als-Aia-Ala linker were generated. All constructs were cioned into an expression vector derived from pUC119 which contained the LacZ promoter, a resistance gene for kanamycin, a multicioning site and the OmpA signal peptide sequence. In frame with the Nanobody® coding sequence, the vector coded for a C-terminal c-myc tag and a (His)6 tag. In case a 35 Gly-Ser-iinker was present in the multivalent construct, ar, expression vector was used derived from pUC119 which contained the LacZ promoter, a resistance gene for kanamycin and the OmpA signal peptide sequence. Directly downstream of the signal peptide a multiple cloning site was present for Nanobody® insertion, followed by a 35Gly-Ser linker encoding DNA sequence and a second multiple cloning site for cloning of a second Nanobody®' sequence. In frame with the resulting N3nobody®’-35Gty-5er-Nanobody& coding sequence, the vector coded for a C-terminal c-myt tag and a {His)6 tag. Table B-2 lists the multivalent constructs generated with RSV-specific Nanobodies®, The sequences of the muitivaient constructs are shown in Table A-3.

Multivalent RSV Nanobody® constructs were expressed, purified and further characterized. Production was done in £, coli TGI cells, followed by purification from the peripiasmtc fraction via the His-tag by IMAC and desalting, essentially as described in Example 7. For certain trivaient constructs (e.g, RSV401, RSV404, RSV406) production was done in P. pastoris followed by purification from the medium fraction. All trivaient Nanobodies® were subjected to gei filtration as a final step to remove possible bivalent and monovalent degradation products.

Binding of purified multivalent Nanobodies® to the hRSV F-protein was confirmed in ELISA on both FTy- protein and on hRSV (see Example 8). For the majority of Nanobodies® the formatting into bivalent and trivaient constructs resulted in a clear but limited (up to 10-foid increase) avidity effect, with the exception of multivalents of 7B2 and NC23 which showed similar EC50 values as their monovalent counterparts {as shown for 7B2 in Figure 2).

Example li: Potency of bi- and trivaient constructs to neutralize hRSV

The potency of the Nanobody® constructs was evaluated in the RSV neutralization assay on different RSV strains (see examples 6 and 9). Bivalent Nanobodies® binding antigenic site II showed marked increases in potencies of 100-to 1000-fold (i.e. much higher than the increase in affinity) in neutralization of Long relative to their monovalent counterparts, with IC50 values ranging from 50-380 pM, being better or similar to Numax Fab. On the RSV B-l strains however, the potency increase was much less strong, and none of the dimeric constructs was more potent than Synagis*.

Surprisingly, this could be overcome by the generation of trivalent constructs, as shown in Figure 3. Trivaient constructs with three Nanobodies® binding antigenic site II were at least 1000-fold more potent neutralizers on RSV B-l strains than their monovalent counterparts.

Example 12: Reactivity of monovalent Nanobodies® with escape mutants of the long strain A number of escape mutants, described in Lopez et al. 1998 (J. Virol. 72: 6922-6928), and specific for antigenic site 11 (R47F/4, R47F/7, RAK13/4, R7C2/11, R7C2/1) or 1V-VI (R7.936/1, R7.S36/4, R7.936/5, R7.432/1) or the combination of both (RRA3), were selected for testing their reactivity with 10 monovalent Nanobodies®, Including Nanobody®' 191C7 (SEQ ID NO: Sj previously identified as not binding to antigenic sites II or IV-V1.

This assay was performed according to Lopez et al. 1998 {J. Virol. 72:6922-69281. In brief, each Nanobody® was tested atC.2 pg/ml in ELISA using antigen extracts of HEp-2 cells infected with the different escape mutants. Absorbance results were normalized for reactivity on the reference virus strain (Long wild type) strain as well as on the control Nanobody® 191C7. Results are shown in Table B-3. A reactivity of >75% is indicated as a filled black square, dark hatched squares correspond to a reactivity between 75 and 50%, light hatched squares correspond to a reactivity of 25-50% and iess than 25% reactivity is indicated by a blank square. In general Nanobodies* already identified as antigenic site li binders previously {192C4,191D3,191F2, NC23,15HS, 7B2 and NC41) were found to be sensitive to typical mutations in antigenic site It, while the other Nanobodies® already identified as antigenic site iV-VI binders were indeed sensitive for mutations in these sites.

Example 13: Reactivity of multivalent Nanobodies® with escape mutants of the Long strain

Subsequently a number of multivalent constructs was analyzed on a limited panel of escape viruses to assess binding. This assay was performed according to Lopez et al. 1998 (J. Virol. 72: 5922-6928). In brief, each Nanobodv® was tested at 0.1 pg/ml for monovalent Nanobodies® and at 0.05 pg/ml for bi- and trivalent Nanobodies® in ELISA using antigen extracts of HEp-2 cells infected with the different escape mutants. Absorbance results were normalized for reactivity on the reference virus strain {Long wild type) strain as well as on the control Nanobody® {191E4; SEQ ID NO: 10, in this particular assay). Results are shown in Table B-4. A reactivity of >75% is indicated as a filled black square, dark hatched squares correspond to a reactivity between 75 and 50%, light hatched squares correspond to a reactivity of 25-50% and less than 25% reactivity is indicated by a blank square. Remarkably, multivalent constructs showed improved binding compared to their monovalent counterpart, to the mutant virus R7C2/11. In addition the biparatopic construct RSV403 was not sensitive to any of the mutants.

Example 14: Neutralisation of escape mutants of the Long strain by multivalent Nanobodies®

In examples 12 and 13, the binding of monovalent Nanobodies® to typical antigenic site !i and/or IV-VI RSV escape mutants has been described. Binding of Nanobodies® specifically recognizing these antigenic sites was almost lost or significantly reduced. Formatting of these Nanobodies® into hi- or trivaient constructs partially restored binding activity but not for sli three escape mutant viruses. Binding to the escape mutant R7C2/1 (mutation K272E in antigenic site II) remained below the level of 25% for any bi-or trivaient construct consisting solely of antigenic site I! binding Nanobodies4’. The Nanobodies® 15B3 and 191E4, which are binding to antigenic site IV-VI, were the oniy Nanobodies® (as such or in biparatopic constructs) able to bind this mutant at a level of 75% or more.

More detailed analysis of the data indicated that binding towards R7C2/1 slightly increased when the valency of the Nanobody® was increased. The binding of 7B2 constructs was 0,4.4 and 13% respectively for the monovalent bivalent (RSV106) and trivaient (RSV40D) formats. Such a low level of residual binding is expected to result in very high loss of potency to neutralize RSV.

The neutralizing potency of Nanobodies® was assessed on the same selected set of escape mutants as described in example 13. For this purpose the monovalent Nanobodies® 7B2,15H8 and NC41 were compared to their respective trivaient counterparts, RSV4QQ, RSV 404 and RSV 407. Of note, in example 13 oniy RSV400 was assessed for binding these escape mutants, in addition also the biparatopic trivaient molecule RSV403 (7B2-15B3-7B2) was analyzed for its neutralizing capacity.

The hRSV micro neutralization assay was essentially performed as described in example 6, In brief, Hep2 cells were seeded at a concentration of 1.5 x 104 cells/wel! into 96-well plates in DMEM medium containing 10% fetal calf serum (FCS) supplemented with Penicillin and Streptomycin (100 U/ml and 100 pg/ml, respectively) and incubated for 24 hours at 37°C in a 5% CO? atmosphere. Virai stocks of different viruses were prepared into Hep2 cells and subsequently titrated to determine the optimal infectious dose for use in the micro neutralization assay. A standard quantity of the specific hRSV strain was pre-incubated with serial dilutions of purified Nanobodies® in a total volume of 50 μΙ for 30 minutes at 37sc. The medium of the Hep2 cells was replaced with the premix to allow' infection for 2 hours, after which 0.1 ml of assay medium was added. The assay was performed in DMEM medium supplemented with 2.5 % fetal calf serum and Penicillin and Streptomycin (lOOU/ml and 100 pg/ml, respectively). Cells were incubated for an additional 72 hours at 37°C in a 5% C02 atmosphere, after which cells were washed twice with 0.05% Tween-20 in PBS and once with PBS alone, after which the cells were fixed with 80 % cold acetone (Sigma-Aldrich, St. Louis, MO) in PBS (100 μΙ/well) for 20 minutes at 4°C and left to dry completely. Next the presence of the F-protein on the celi surface was detected in an ELISA type assay. Thereto, fixed Hep2 cells were blocked with 5%

Porcine Serum Albumin solution in PBS for 1 hour at room temperature, than incubated for 1 hour with anti-F-protein poiycionai rabbit serum (Corral et a!. 2007,, BMC Biotechnol. 7:17) orSynagis® (2 pg/ml). For detection goat Anti-rabbit-HRP conjugated antibodies or goat Anti-Human IgG, Fey fragment specific-HRP (Jackson ImmunoResearch, West Grove, PA) was used, after which the EUSA was developed according to standard procedures.

As shown in Figures 4A-C, the monovalent Nanobodies® had almost no neutralizing potential towards the antigenic site 11 escape mutant viruses R7C2/11 and R7C2/1. The potency to neutralize the R7.935/4 antigenic site iV-Vi variant was comparable to the potency to neutralize the wild type Long strain. These data are in line with the binding data of example 12 and the epitope mapping as described for these Nanobodies® in example 5.

The trivalent Nanobody® constructs however, were potently neutralizing al! 3 escape mutants (Figures 4D-G). Maximal inhibition was observed at concentrations as low as about 20 nM while this level of inhibition was not observed for the monovalent Nanobodies® at concentrations up to 2 μΜ. The potent neutralization of R7C2/1, almost equivalent to the neutralization of R7C2/11, is most surprising since example 13 showed a very significant loss of bindmg activity for the trivalent molecule RSV40Q which was expected to result in a very high loss of neutralization potency. The bivalent IgG Synagis ® Paiivizumab, also recognizing antigenic site II was not able to block replication of R7C2/1 or R7C2/11 significantly at concentrations of about 0.2 μΜ. At this concentration an IC50 was not reached while R7.936/4 and wiid type Long virus were neutralized with an IC50 of a few nM (data not shown).

Example 15: Analysis of impact of linker iength on potency of NC41 trivalents

To determine the impact of the (inker length of trivalents of NC41, different constructs with linkers ranging from 3Ala, 9GS, 15GS, to 20GS linkers (RSV408, RSV409, RSV407 and RSV410 resp.) were generated. Ail four NC41 trivalents were able to completely neutralize both RSV B-2 and Long strains (Figure 5). No effect of linker iength was observed in neutralization of RSV Long, as all constructs were equally potent. By contrast, the constructs with 9GS and BAia linkers had increased (C50 values on the B-l strain, indicating that a minimal (inker length of 15GS is required for maxima! potency'. This may be explained by the observation that bivalent NC41 constructs already are very potent neutralizers on Long, while on the 8-1 strain the potency difference between bivalent and trivalent NC41 is much larger (see Example 11). In RSV408 and RSV409 the accessibility of the middle Nanobody® may be less optimal.

Example 16: Humanization of Nanobody® NC41

The sequence of Nanobody® NC41 was aligned to the human germline VH3-23 to allow selection of residues suitable for further humanization of the Nanobody® sequence, in addition, in silico analysis was done to identify residues that are potentially prone to post-transiational modifications, such as Asp isomerisation, and to identify mutations that might improve the chemical stability. The CDR regions and the so-caiied Hallmark residues, which are known to be essential for the stability and potency of Nanobodies* were excluded for modification.

For NC41 in total II positions were selected for mutation to the corresponding human residue: Four mutations were simultaneous introduced (Val5Leu, Alal4Pro, Giu44Gly, GlnlOSLeu), as these residues were not expected to dramatically affect the Nanobody® function {based on data from other Nanobodies®), in this basic variant, seven residues of which it was unknown whether mutation to the human counterpart was allowed (SeilSArg, I!e20!eu, Ala74Ser, Giv78leu, Ala83Arg, Asp856lu, ArglOSGIn) were mutated using a library approach, allowing either the witdtype or the corresponding human amino acid at each posirion. The resulting library', with a theoretical diversity of 128, was generated by gene assembly using overlapping oligonucleotide sequences containing degenerated codon use, and subsequently cloned into an expression vector derived from pUC119 which contained the LacZ promoter, a resistance gene for kanamycin, a multicloning site and the OmpA leader sequence. In frame with the Nanobody®' coding sequence, the vector coded for a C-terminal c-myc tag and a (His)6 tag. Nanobodies* were produced in the periplasm of E. coli (see F.xample 7). Library diversity was confirmed by sequence analysis,

Periplasmic extracts from 368 individual NC41 variants and wildtype NC41 were generated and subjected to a functional screening cascade to identify the best humanized NC41 variant, in terms of both potency and stability, in a first step, RSV binding of humanized NC41 variants to RSV Long was determined in ELISA (Hytest, Turku Finland; #8RSV79)(see Example 8),

Moreover, the positive binders were analyzed for binding to Hep2 cells infected with RSV B-l strain. In here, Hep2 cells were seeded into 96-welts piates and infected with RSV B-l strain, essentially following the procedure described for the neutralization assay (see Example 6). Three days later cells were fixed with ice-cold acetone and plates were used in an ELiSA assay using periplasmic extracts at different dilutions. Nanobody* binding to Hep2-Bl infected cells was detected using anti-VHH rabbit poiycionai antibody, followed by goat Anti-rabbit-HRP conjugated antibodies, after which the ELiSA was developed according to standard procedures.

Additionally, in order to verify if the introduced mutations affected the temperature stability, peripiasmatic extracts of ail binders were heated to 74“C for 2 hours, which is 5°C above the melting temperature of wildtype NC41. The binding to RSV long before and after heating was analyzed in ELISA, and the ratio of binding signal after vs. before heating was taken as measure for temperature stability. finally, the kinetic off-rates of the variants were determined in Biacore assay on the F,m.NN protein, as described in Example 8.

Alt binders were sequenced and ranked according to their capacity to bind the F-protein of RSV. When analyzing the sequences of the strongest binders, a clear preference for GlnlQS (human residue) was observed in all cases. Whereas the Iie2GLeu mutation appeared underrepresented, for all other positions there was no dear preference for either the wild type or the human sequence, with variants containing up to 10 mutations compared to wildtype NC41. Notably, in one variant an additional pointmutation (Gly54Asp) within the CDR2 region was observed. This variant, NC41 variant 6, showed the lowest off-rate of all variants and wildtype NC41, resulting in affinity increase.

Based on the sequence and functional data, 18 variants (Table A-4) were selected for further characterization as purified proteins (Figures 6 and 7). All variants were produced and purified, and potencies for neutralization of RSV Long and B-l were determined in the micro neutralizations assay. While most variants shewed very similar activity to wildtype NC41, several variants showed increased potency on both Long (2-fold) and B-l (6-fold), with the strongest neutralizers being NC41 variants 6, 8,9 17, and 18. Notably, variant 18 was maximally humanized at all 11 positions, with the additional introduction of Asp54 in the CDR2 region. Variant 10 and 11 were more potent in neutralizing B-l strain than NC41, but not on Long strain.

For a select panel of NC41 variants the kinetic binding parameters were determined in Biacore on Ftn. NN protein (Table B-5) as described in Example 8, No significant differences in the calculated data were observed for NC41 and the humanized NC41 variants 6, 8 and 17. It should be noted that the on-rates of all NC41 variants were at the detection limit of the instrument, but the off-rates could be ranked as vOo < vl7<NC41<v08. The impact of the Giy to Asp mutation in CDR2 (position 54) could be clearly demonstrated when comparing vl7 and v!8 as this is the only difference in these maximally humanized variants. Neutralization was tested for both the Long strain and the B-l strain in two independent assays in comparison to the NC41 wild type as shown in table B-5. In both assays NC41vl8 was more potent than NC41 on both viruses and in both assays NC41vl8 was more potent than NC41vl7 on the Long strain. The improved neutralization of NC41vl8 was also observed for the B-l strain in the second assay.

All NC4-1 variants were subjected to heat-induced unfolding to assess the effect of the introduced mutations on the stability of the protein. Thereto the melting temperature (Tm) was determined by stepwise increase in temperature in presence of Sypro Orange, a dye that binds to Trp residues that become exposed upon unfolding of the protein. All variants showed to have increased Tm relative to wildtype NC41 (6S“C), up to 9°C for variant 18.

Example 17: Further sequence optimization of NC41 for expression

The sequence of Nanobody®’ NC41 was further analysed with the aim to optimise expression in Pichia pastoris. NC41 variants 19-26 were designed by combining humanized positions that were shown to be permitted without loss in potency in the micro-neutralization assay {Example 16). Four mutations were simultaneous introduced (A!al4Pro, Serl9Arg, tle20Leu, GlnlOSLeu), while three mutations were both individually and in each possible combination examined (AiaSBArg, Asp85Glu, Argl05Gln)(see Table A-4). Ail constructs were doned into an expression vector and introduced into the Pichia pastoris strain XL-33, after which the number of incorporations in the Pichia genome was assessed by quantitative real-time PCR. From each construct one done with 1-2 copies and one with four or more copies were selected for small scale productions, and expression yield of NC4i variants relative to wild type was estimated by gel electrophoresis on S0S-PA6E gels. NC41 variants 20, 22, 24, 25 and 26 showed the highest expression, with similar expression leveis as wild type NC41 already at low copy number. NC41 variants 22 and 26 were recloned in an expression vector for t, coli for production and purification of Myc-His-tagged Nanobodies (see example 7). The potency of both variants for neutralization of RSV Long was tested in the micro neutralization assay, as described in example 6. Both variants were equally potent as wild type NC41 (IC50of 126 and 310 nM forv22 and v26, respectively).

Example 18: Sequence optimization of RSV407 for chemical stability

During the production of the Nanobodies and polypeptides of the invention, pyro glutamate (pGlu) on the amino terminus was observed {via RP-HPLC). Levels of more than 15% pGlu were detected following fermentation and the level of pGlu was steadily increasing upon storage during stability studies. Therefore, the N-terminal Glutamate (E) was changed into an Aspartate (D). This would eliminate the possibility of pGlu post-translational modification of the N-terminus and hence lead to increased product stability,

The amino acid sequence of the sequence optimized Nanobody'' variant is given in Table A-5 {RSV434; SEQ ID NO: 142) respectively. For the production of this Nanobody* s Pichia expression system was developed based on the commercially available system from Invitrogen using X-33 as a host strain. The system makes use of the AOX1 promoter to drive the production of the Nanobody* and uses the alpha mating secretion peptide for secretion of the Nanobody* into the medium.

The sequence optimized RSV434 was analyzed for expression levels, via RP-HPLC, SE-HPLC and compared to the parental molecule (RSV407) with respect to RSV neutralization.

There was no significant difference in expression levei compared to R.5V407 and both the low and high copy number clones were producing more than Ig/L clarified medium (cell free).

One ml samples were captured on a 1ml MEP Hypercel column, eluted and analyzed via SE-HPLC and RP-HPLC. SE-HPLC analysis showed monomeric material, whereas RP-HPLC analysis, as expected, clearly showed the absence of the pGiu post peak. RSV434 was further purified from the medium, captured on MEP HyperCel! and polished via anion exchange chromatography.

An hRSV micro neutralization assay was essentially performed as described in example 6. Figure 9 shows the neutralization on both RSV Long and B-l strains by both RSV407 and its sequence optimized variant RSV434,

Example 19: Preparation of multivalent constructs of humanized and/or sequence optimized NC41 Nanobodv® NC41 humanized variants of Example 16 were formatted as trivalent constructs using 15GS linkers (sequences are shown in Table A-5). The trivalents were produced and purified as described in Example 10. Figure SA shows the neutralization on both RSV Long and B-l strains of two orths trivalent humanized NC41 variants with their corresponding monovalent Nanobodies®. Figure 8B shows the neutralization on both RSV Long and 8-1 strains of the trivalent NC41 variants. IC50 values for neutralization of RSV Long and S-i strains by the trivalent NC41 variants are shown in Table B-7. Similar as to parental NC41 trivalent (RSV407), trivalents of the humanized NC41 variants were around 60 times more potent neutralizers of Long than Synagis®. On the B-l strain trivalents were more potent neutralizers than Synagis, but here also slightly enhanced compared to the trivalent of parental NC41 RSV407 in following order RSV427>RSV426>RSV414. The increased potency of monovalent variants for B-l thus appeared to have resulted in slightly improved trivalents.

Based on further sequence optimization shown in Examples 17 and 18, a number of additional trivalent constructs (Table B-6) were generated, Ali constructs were cloned in a Picbic pastoris expression vector, transformed into Pichia and subjected to fermentation to test expression levels, stability and potency. Both in small scale shake flask expressions and fermentation RSV440 (variant 26) and RSV441 (variant 22) showed high expression levels.

Example 20: In vitro efficacy of the multivalent constructs

The neutralizing capacity of Nanobody RSV434 and Synagis was evaluated in a plaque reduction assay against 31 RSV/Aand 30 RSV/B dinical isolates. Both anti-RSV compounds as well as Synagis were tested at a single concentration of 40 pg/ml.

Synagis and RSV434 both performed efficiently with respectively 87% and 97% of the strains being reduced in virus titers by at least 100-fold compared to PBS control (Table B-8). In addition, RSV434 showed greater neutralizing capacity compared to Synagis. Tne majority of the RSV strains (84%) were completely inhibited by RSV434 while significantly fewer strains ¢20%) were completely inhibited by Synagis (Table B-8).

Example 21: in vivo efficacy of the multivalent constructs

The cotton rat model is the golden standard model for RSV. In this model, the cotton rats are infected with the RSV/Tracy strain {day 0) and 4 days after infection, viral titers and viral RNA are assessed in lung lavages and nasal washes. In a prophylactic set-up, a significant and dose-dependent decrease in viral load was observed upon intranssal administration of RSV407,24 hours before RSV infection (Figure 10).

In addition, a therapeutic approach was explored in which infected cotton rats were treated with the Nanobodies after 24h or 48h of infection thereby mimicking the situation of RSV infected humans. In both cases significant inhibition of viral replication was observed (Table B-S and Figure 11).

In ail studies performed to date, the Nanobody was delivered intranasaliy as a mimic for pulmonary delivery. Using this route of administration 3-41% of Nanobody was available in the lungs as assessed by ELISA on bronchial lavage taken shortly after administration.

In an attempt to overcome the possible interference of residual Nanobody in the lung lavages, the vira! detection was delayed to day 7 post inoculation, A separate pharmacokinetic study performed in Sprague Dawley rats allowed to estimate the half life of the Nanobody in the lung to be about 10.S. At day 7 which is 5-6 days after the last administration, the Nanobody is sufficiently cleared from the lung to no longer interfere in the assay. The viral load of positive control animals dropped from 10E5 to 10E2 pfu/ml. Nevertheless it was still possible to show a reduction of about 0.6 log by treatment with RSV407 (Table B-9).

As an alternative approach a quantitative PCR was developed to detect viral RNA. Both in prophylactic and therapeutic experiments a significant reduction in RSV RNA was observed (Table 8-9).

Example 22: Generation of RSV escape mutants

In order to identify the critical contact residues with the F-proteln, the generation of RSV Long escape mutants was analysed after culturing RSV Long in presence of Nanobodies at about their respective IC90 concentrations. Both monovaient NC41 (at 5 pg/m!) and its trlvalent RSV407 (at 2.5 ng/m!) were used, as weii as the bispecific trivalent RSV413 (NC41-15B3-NC41) to verify if a construct that recognizes two different epitopes would affect the time frame of viral escape onset. After 12 passages of successive incubation of Long on Hep2 ceils in presence of Nanobodies, viral out growth was observed for the conditions with monovalent NC41 but surprisingly not with the trivalent Nanobodies. Single virus stocks were purified from plaques for repetitive rounds, after which the sequence of the F-protein of the potential escape variant couid be determined. Two distinct escape variants were identified for NC41, NC41/13 with the mutation of N262Y, and NC41/17 containing mutation N276Y.

TABLES

Table A-l: Sequences of monovalent Nanobodies® that bind RSV F protein

Table A-2: F-protein sequences

Table A-3: Amino acid sequences of multivalent constructs that bind hRSV

Table A-3; Continued

Table A-3: Continued

Tabie A-S: Continued

Table A-3: Continued

Table A-4: Sequences of humanised and/or sequence optimised NC4i variants !

................

Table A-4: Continued

Table A-S: Amino acid sequence of multivalent humanized and/or sequence optimized constructs that bind hRSV

Table A-5: Continued

Table A-6: Preferred combinations of CDR sequences

Table A-S: Continued

Tabie A-7: Linker sequences

Table B-l: Characteristics of Nanobodies® that bind hRSV F-protein

Table B-2: Nomenclature for multivalent Nanobody* constructs directed against hRSV F-proteln

Table B-3: Reactivity of monovalent Wanobodies® with antigen extracts of HEp-2 ceils infected with different escape mutants of the Long strain

Table B-4: Reactivity of monovalent and bivalent Nanobodies® with antigen extracts of HEp-2 ceils infected with different escape mutants of the Long strain

Table B-5: Neutralization and kinetic binding parameters in Biacore on F,m-NN protein for selected WC4JL variants

Table B-6: Trivalent humanized and/or sequence optimized variants of NC41

Table B-7: Neutralization of Long and B-l by trivalent NC41 variants

Tabie B-S: Neutralization capacity of RSV434and Synagis in piaque assay against various ctinica! isolates

Table B-9: Overview table of all cotton rat experiments performed showing both the detection of replication competent virus and viral RNA at day 4 post inoculation (in experiment 3 detection at day 7 was also performed)

-= p < 0.05

Claims

1. An isolated polypeptide that comprises or essentially consists of at least one amino acid sequence and/or Nanobody that is directed against and/or specifically binds protein F of hRSV, and optionally further comprises one or more other amino acid binding units, optionally linked via one or more peptidic linkers, wherein the at least one amino acid sequence and/or Nanobody is chosen from the following (A) to (B): (A) an amino acid sequence and/or Nanobody that consists of 4 framework regions (FR1 to FR4, respectively) and 3 complementarity determining regions (CDR1 to CDR3, respectively), in which: - CDR1 is chosen from the group consisting of: a) SEQ ID NO: 98; and b) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 98, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; - CDR2 is chosen from the group consisting of: c) SEQ ID NO: 102; and d) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 102, provided that: i) said stretch of amino acid residues has an Aspartic acid (Asp, D) at position 6 (position 54 determined according to Kabat numbering); and ii) the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; - CDR3 is chosen from the group consisting of: e) SEQ ID NO: 121; and f) a stretch of amino acid residues that has no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with SEQ ID NO: 121, provided that the amino acid sequence comprising said stretch of amino acid residues binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence comprising said stretch of amino acid residues has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the amino acid sequence comprising said stretch of amino acid residues without the 3, 2 or 1 amino acid difference; or (B) an amino acid sequence and/or Nanobody, chosen from the following a) to d): a) SEQ ID NO’s: 60-76; b) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 60-76, provided that: i) the amino acid sequence has a Glutamine (Gin, Q) at position 105 (said position determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference, c) SEQ ID NO’s: 146-153; d) amino acid sequences that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 146-153, provided that: i) the amino acid sequence has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the amino acid sequence binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the amino acid sequence has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the amino acid sequence without the 3, 2 or 1 amino acid difference.

2. An isolated polypeptide that comprises or essentially consists of at least one amino acid sequence and/or Nanobody with SEQ ID NO: 5, in which one or more amino acid residues have been mutated selected from the following: Val5Leu, Ala14Pro, Ser19R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

3. The polypeptide according to claim 2, that comprises or essentially consists of at least one amino acid sequence and/or Nanobody with SEQ ID NO: 5, wherein following amino acid residues have been mutated: - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln; - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp; - Ala83Arg, Asp85Glu, Arg105Gln, Gin 108Leu and Gly54Asp; - Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp; - Gly54Asp; - Ala14Pro, Ser19Arg, lle20Leu and Gln108Leu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu and Ala83Arg; - Ala14Pro, Ser19Arg, Ile20l_eu, Gln108Leu and Asp85Glu; - Ala14Pro, Seri 9Arg, Ile20l_eu, Gln108Leu and Arg105Gln; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg and Asp85Glu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg and Arg105Gln; - Ala14Pro, Seri 9Arg, lle20Leu, Gln108Leu, Asp85Glu and Arg105Gln; or - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg, Asp85Glu and Arg105Gln.

4. The polypeptide according to any one of claims 1 to 3, which is a multivalent polypeptide.

5. The multivalent polypeptide according to claim 4, which is a bivalent or trivalent polypeptide.

6. The trivalent polypeptide according to claim 5, that is directed against and/or specifically binds protein F of hRSV, chosen from the following polypeptides: a) SEQ ID NO’s: 77-79 and 158; b) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 77-79 and 158, provided that: i) the amino acid sequences or Nanobodies encompassed in said polypeptide have a Glutamine (Gin, Q) at position 105, a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at position 83 and/or a Glutamic acid (Glu, E) at position 85 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the polypeptide without the 3, 2 or 1 amino acid difference, c) SEQ ID NO’s: 159-161; or d) polypeptides that have no more than 3, preferably no more than 2, more preferably no more than 1 amino acid difference with one of SEQ ID NO’s: 159-161, provided that: i) the amino acid sequence or Nanobody encompassed in said polypeptide has a Proline (Pro, P) at position 14, Arginine (Arg, R) at position 19, Leucine (Leu, L) at position 20 and Leucine (Leu, L) at position 108 (said positions determined according to Kabat numbering); and ii) the polypeptide binds protein F of hRSV with the same, about the same, or a higher affinity (said affinity as measured by surface plasmon resonance) and/or the polypeptide has the same, about the same, or a higher potency (as determined by microneutralization assay) compared to the polypeptide without the 3, 2 or 1 amino acid difference.

7. Isolated trivalent polypeptide comprising or essentially consisting of three amino acid sequences and/or Nanobodies with SEQ ID NO: 5, in which one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Ala14Pro, Ser19R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

8. The trivalent polypeptide according to claim 7, comprising or essentially consisting of three amino acid sequences and/or Nanobodies with SEQ ID NO: 5, in which following amino acid residues have been mutated: - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln; - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp; - Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp; - Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp; - Gly54Asp; - Ala14Pro, Ser19Arg, lle20Leu and Gln108Leu; - Ala14Pro, Seri 9Arg, lle20Leu, Gln108Leu and Ala83Arg; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu and Asp85Glu; - Ala14Pro, Seri 9Arg, lle20Leu, Gln108Leu and Arg105Gln; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg and Asp85Glu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg and Arg105Gln; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Asp85Glu and Arg105Gln; or - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg, Asp85Glu and Arg105Gln.

9. Isolated trivalent polypeptide comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody/Nanobodies that form(s) part of SEQ ID NO: 53, one or more (such as two, three, four, five, six, seven, eight or nine, ten, eleven or twelve) amino acid residues have been mutated selected from the following: Val5Leu, Ala14Pro, Ser19R, lle20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

10. The trivalent polypeptide according to claim 9, comprising or essentially consisting of SEQ ID NO: 53, in which in at least one (preferably in two, more preferably in all three) Nanobody/Nanobodies that form(s) part of SEQ ID NO: 53, following amino acid residues have been mutated: - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; - Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln; - Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp; - Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp; - Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp; - Gly54Asp; - Ala14Pro, Ser19Arg, lle20Leu and Gln108Leu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu and Ala83Arg; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu and Asp85Glu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu and Arg105Gln; - Ala14Pro, Ser19Arg, Ile20l_eu, Gln108Leu, Ala83Arg and Asp85Glu; - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg and Arg105Gln; - Ala14Pro, Ser19Arg, Ile20l_eu, Gln108Leu, Asp85Glu and Arg105Gln; or - Ala14Pro, Ser19Arg, lle20Leu, Gln108Leu, Ala83Arg, Asp85Glu and Arg105Gln.

11. The trivalent polypeptide according to any one of claims 5 to 10, comprising or essentially consisting of one of SEQ ID NO’s: 77-79 and 158-161.

12. An amino acid sequence that is directed against and/or specifically binds protein F of hRSV, as defined in any one of claims 1 to 11.

13. An isolated monovalent construct, comprising or essentially consisting of one amino acid sequence according to claim 12.

14. Use of the monovalent construct according to claim 13, in preparing a multivalent polypeptide, such as the multivalent polypeptide according to any one of claims 5 to 11.

15. An isolated nucleic acid or isolated nucleotide sequence, that encodes the polypeptide according to any one of claims 1 to 11, the amino acid sequence according to claim 12, or the monovalent construct according to claim 13.

16. Use of the nucleic acid or nucleotide sequence according to claim 15, that encodes the monovalent construct according to claim 13, for the preparation of a genetic construct that encodes the polypeptide according to any one of claims 1 to 11.

17. A host or host cell that expresses, or that under suitable circumstances is capable of expressing the polypeptide according to any one of claims 1 to 11, the amino acid sequence according to claim 12, or the monovalent construct according to claim 13; and/or that comprises the nucleic acid or nucleotide sequence according to claim 15.

18. A composition, comprising the polypeptide according to any one of claims 1 to 11, at least one amino acid sequence according to claim 12, or the monovalent construct according to claim 13, or the nucleic acid or nucleotide sequence according to claim 15.

19. The composition according to claim 18, which is a pharmaceutical composition.

20. A pharmaceutical composition comprising the polypeptide according to any one of claims 1 to 11, the amino acid sequence according to claim 12, or the monovalent construct according to claim 13, and a carrier suitable for pulmonary delivery.

21. A method for producing the polypeptide according to any one of claims 1 to 11, the amino acid sequence according to claim 12, or the monovalent construct according to claim 13, or the composition according to any one of claims 18 to 20, said method at least comprising the steps of: a) expressing, in a suitable host cell or host organism or in another suitable expression system, the nucleic acid or nucleotide sequence according to claim 17, or cultivating and/or maintaining a host or host cell according to claim 19 under conditions that are such that said host or host cell expresses and/or produces the polypeptide according to any one of claims 1 to 11, at least one amino acid sequence according to claim 12, or the monovalent construct according to claim 13, or the composition according to any one of claims 18 to 20, optionally followed by: b) isolating and/or purifying the polypeptide according to any one of claims 1 to 11, the amino acid sequence according to claim 12, or the monovalent construct according to claim 13, thus obtained.

22. A method for preparing the polypeptide according to any one of claims 1 to 11, said method comprising at least the steps of linking two or more monovalent amino acid sequences or the monovalent construct according to claim 13 and for example one or more linkers.

23. A method for the prevention and/or treatment of hRSV infection, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of the polypeptide according to any one of claims 1 to 11, at least one amino acid sequence according to claim 12, or the monovalent construct according to claim 13 and/or the composition according to any one of claims 18 to 20.

24. A method for the prevention and/or treatment of at least one of respiratory illness, upper respiratory tract infection, lower respiratory tract infection, bronchiolitis (inflammation of the small airways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezing and asthma, said method comprising administering, to a subject in need thereof, a pharmaceutically active amount of a polypeptide according to any one of claims 1 to 11, at least one amino acid sequence according to claim 12, or the monovalent construct according to claim 13 and/or the composition according to any one of claims 18 to 20.

25. Use of a polypeptide according to any one of claims 1 to 11, or a monovalent construct according to claim 13 in the manufacture of a medicament for the prevention and/or treatment of at least one of: respiratory illness; upper respiratory tract infection; lower respiratory tract infection; bronchiolitis (inflammation of the small airways in the lung); pneumonia; dyspnea; cough; (recurrent) wheezing; or asthma.

26. Use of a polypeptide according to any one of claims 1 to 11, or a monovalent construct according to claim 13 in the manufacture of a medicament for the prevention and/or treatment of hRSV infection.

27. Pharmaceutical device used for the pulmonary delivery of a polypeptide according to any of claims 1 to 11, or a monovalent construct according to claim 13, or a composition comprising the same.

28. Pharmaceutical device according to claim 27 that is an inhaler for liquids (e.g. a suspension of fine solid particles or droplets), an aerosol or a dry powder inhaler, comprising a polypeptide according to any of claims 1 to 11, or a monovalent construct according to claim 13.