AU2012227280B2 - Human cytomegalovirus immunotherapy - Google Patents

Abstract

An isolated protein construct comprises a polyepitope derived from multiple human cytomegalovirus protein antigen epitopes conjugated to an extracellular domain of glycoprotein B, which isolated protein is capable of eliciting a cytotoxic T 5 lymphocyte immune response as well as a neutralizing antibody response to human cytomegalovirus. Also provided are pharmaceutical compositions comprising the isolated protein or an adenoviral expression construct for delivery and expression of a nucleic acid encoding the isolated protein for prophylactic and/or therapeutic treatment of human cytomegalovirus infection, particularly in humans. 14 I P4H P4 CLV) 1~4i-1 c oo 0 C,) 0 >I Dhus~Of > Cy ca r34 a.( rN Cy p H0C -0 E-.C P, , H 0.o H *0 w. 1 0 .

Description

TITLE

HUMAN CYTOMEGALOVIRUS IMMUNOTHERAPY FIELD OF THE INVENTION THIS INVENTION relates to an isolated protein and encoding nucleic acid suitable for use in Human Cytomegalovirus immunotherapy. In particular, the invention relates to a recombinant protein which includes a polyepitope derived from multiple antigen epitopes conjugated to an extracellular domain of glycoprotein B, which, when used in immunotherapy is capable of eliciting a cytotoxic T-lymphocyte immune response as well as a neutralizing antibody response to Human Cytomegalovirus, without being limited thereto.

BACKGROUND OF THE INVENTION

Human cytomegalovirus (HCMV) belongs to the herpesvirus group and is found universally throughout all geographic locations and socioeconomic groups. While it infects between 5 0 and 8 5 % of adults, for most healthy persons who acquire primary HCMV after birth, there are no long-term consequences.

However, there are clinical situations where HCMV infection is a significant cause of morbidity and mortality. For example, HCMV infection carries significant health risks to a foetus in utero, to people who work with children, and to individuals having a compromised immune system, eg. those infected with HTV-1 or having undergone organ transplantation (Britt, 1996, Trends Microbio 4 34; Plotkin, 1999, Pediatr Infect Dis J 18 313).

Epidemiological studies have shown that 80 to 90% of developing unborn babies who acquire congenital HCMV infection display a variable pattern of pathological sequelae within the first few years of life that may include hearing loss, vision impairment and mental retardation.

Accordingly, there is a need for an effective vaccine to provide such a reduction in HCMV load within the population. To this end, there have been a number of such attempts using either attenuated HCMV strains or subunit vaccines (as reviewed by Britt, 1996, supra·, Plotkin, 1999, supra).

Initial vaccines were based on immunisation using attenuated strains of HCMV, eg., the Towne and AD-169 strains (Elek & Stem, 1974, Lancet 1 1-5,1974;

Neff et al., 1979, Proc Soc Exp Biol Med 160 32). The issue of whether a HCMV vaccine should invoke both humoral and cellular arms of the immune system is of considerable interest and although both attenuated viruses were shown to elicit these responses, neither vaccine prevented foetal infection in pregnant women experiencing a primary HCMV infection. Furthermore, vaccinated normal volunteers showed limited protection from vital challenge using the HCMV Toledo strain (Quinnan etal, 1984, Ann Intern Med 101478; Alder etal, 1998, Pediatr Infect Dis J. 17 200).

Subsequent vaccine development has included subunit vaccines which are based on single HCMV antigen formulations, eg. by using the full-length glycoprotein B (gB) polypeptide in combination with MF59 adjuvant (Chiron), or alternatively, a recombinant full-length gB polyepitope protein expressed using a viral vector (Pass et al., 1999, J Infect Dis 180 970; Alder et al., 1999, J Infect Dis 180 843). Additionally, a canarypox virus expressing a full length recombinant HCMV pp65 polyepitope has been tested in a clinical trial and shown to elicit a strong CTL and antibody response to this antigen (Gyulai et al, Proceedings of the Seventh International Cytomegalovirus Workshop, Brighton, UK, March 7-9,1999, abstract). However, vaccine formulations based on one or more full-length HCMV antigens are likely to present a number of limitations in that normal cellular processing is interrupted, thereby affecting epitope presentation. For example, the expression of HCMV proteins such as pp65 can inhibit proteasomal processing of IE-1 through an associated kinase activity (Gilbert et al., 1996, Nature 383, 720).

An alternative approach for producing CTL responses, as described in WO 03/000720, has been to combine a plurality of epitopes ftom various antigens to form a polyepitope construct and thereby avoid the use of full-length antigens altogether.

SUMMARY OF THE INVENTION

The present invention broadly relates to an isolated protein suitable for use in Human Cytomegalovirus immunotherapy.

In a particular form, the isolated protein comprises a HCMV polyepitope amino acid sequence including a plurality of epitopes from two or more different HCMV antigens and an extracellular Human Cytomegalovirus-encoded glycoprotein B. · '

The recombinant protein is suitably capable of eliciting both a cytotoxic T-lymphocyte immune response and a humoral immune response (preferably a neutralizing antibody response) to HCMV in a human. : - ' -

In a first aspect of the invention, there is provided an isolated protein comprising a Human Cytomegalovirus polyepitope amino acid sequence and an . amino acid sequence of an extracellular domain of Human Cytomegalovirus : glycoprotein B.

Suitably, the Human Cytomegalovirus polyepitope comprises a plurality of epitopes capable of elicting a cytotoxic T-lymphocyte (CTL) response.

The extracellular domain of Human Cytomegalovirus glycoprotein B may be the entire extracellular domain or a fragment thereof, which comprises one or more B cell epitopes capable of eliciting a neutralizing antibody response.

Suitably, the Human Cytomegalovirus polyepitope comprises epitopes which are selected to provide broad interracial coverage of the human population. In one embodiment, the Human Cytomegalovirus polyepitope comprises a plurality of CTL epitopes restricted by the HLA class I specificities HLA-A1, -A2, -A3, -All, -A23, -A24, -A26, -A29, - A30, -B7, -B8, -B27, - B35, -B38, -B40, -B41, -B44, -B51, -B57 and-B58.

Preferably, according to this embodiment the epitopes are selected from HCMV antigenic proteins selected from the group consisting of: gB, gH, pp28, pp50, pp65, pp 150, IE-1 and IE-2.

In a preferred embodiment, the Human Cytomegalovirus polyepitope further comprises one or more MHC class II restricted CTL epitopes.

In a particular embodiment, the Human Cytomegalovirus polyepitope comprises a plurality of CTL epitopes selected from Table 1 (SEQ ID NOS: 6-52).

In a preferred form, the Human Cytomegalovirus polyepitope has an amino acid sequence as set forth in FIG. 1 (SEQ ID NO:5).

In embodiments relating to recombinant protein expression in a host cell in vitro, the extracellular domain of Human Cytomegalovirus glycoprotein B includes one or more amino acid substitutions, deletions or additions that remove one or more proteolytic cleavage sites therein. A non-limiting example is one or more furin proteolytic processing sites in the extracellular domain of Human Cytomegalovirus glycoprotein B.

Even more preferably, the isolated protein further comprises a cytoplasmic domain of glycoprotein B contiguous with the extracellular domain of Human Cytomegalovirus glycoprotein B.

In another particular embodiment, the isolated protein still further comprises a secretion signal amino acid sequence, preferably at the N-terminus of the extracellular domain of Human Cytomegalovirus glycoprotein B.

In particularly preferred embodiments, the isolated protein of this aspect comprises an amino acid sequence as set forth in FIG. 11A (SEQ ID NO:l) or FIG. 12A (SEQ ID NO:2).

In a second aspect, the invention provides an isolated nucleic acid encoding the isolated protein of the first aspect.

In particular embodiments, the isolated nucleic acid may comprise a nucleotide sequence set forth in FIG. 1 IB (SEQ ID NO: 3 ) or FIG. 12B (SEQ ID NO: 4), or a fragment thereof.

In a third aspect, the invention provides a genetic construct comprising the isolated nucleic acid of the second aspect.

Preferably, the genetic construct is an expression construct wherein said isolated nucleic acid of the second aspect is operably linked to one or more regulatory sequences present in an expression vector.

In embodiments relating to expression constructs for administration to an animal, the expression vector is preferably a viral vector such as an adenovirus-based expression vector or a pox virus vector, although without limitation thereto.

More preferably, the expression vector is preferably an adenovirus-based expression vector.

Still more preferably, the adenovirus-based expression vector is an Ad5/F35 vector.

In another embodiment, the expression construct comprises an expression vector suitable for production of the isolated protein in vitro as a recombinant protein for subsequent purification. :

In a fourth aspect, the invention provides a host cell comprising the expression construct of the third aspect.

In one embodiment, the host cell is a cell isolated from an animal to which the expression construct has been administered.

In another embodiment, the host cell has been transfected, transformed or otherwise introduced with the expression construct in vitro, for the purpose of subsequent purification of the isolated protein of the first aspect.

In a fifth aspect, the present invention provides a pharmaceutical composition comprising an isolated protein of the first aspect, an isolated nucleic acid of the second aspect, or an expression construct of the third aspect and a pharmaceutically-acceptable carrier, diluent or excipient. .

Preferably, the pharmaceutical composition is an lmmunotherapeutic composition suitable for use in the prophylactic or therapeutic treatment of a disease or condition associated with HCMV infection in an animal.

More preferably, the immunotherapeutic composition is a vaccine for eliciting a protective immune response against HCMV.

In a sixth aspect, the invention provides a method of prophylactically or therapeutically treating a Human Cytomegalovirus infection in an animal including the step of administering to the animal an isolated protein of the first aspect, an isolated nucleic acid of the second aspect, or an expression construct of the third aspect.

Preferably, the method includes the step of inducing both cytotoxic T-lymphocyte (CTL) and humoral responses in said animal.

In seventh aspect, the invention provides a method of expanding human CMV-specific CTLs for adoptive immunotherapy, including the steps of: (i) contacting one or more cells isolated from an animal with the isolated protein of the first aspect; and (ii) culturing said one or more cells to thereby expand HCMV-specific CTLs from said one or more cells.

In an eighth aspect, the invention provides a method of adoptive immunotherapy including the step of administering said HCMV-specific CTLs . produced at step (ii) of the seventh aspect to an animal to thereby prophylactically or therapeutically treat a Human Cytomegalovirus infection of said animal. '

In a ninth aspect, the invention provides use of the isolated protein of the first aspect or the expression construct of the third aspect in the manufacture of a medicament for prophylactically or therapeutically treating a Human Cytomegalovirus infection in an animal. .

Preferably, according to the aforementioned aspects the animal is a mammal. . More preferably, the animal is a primate.

Even more preferably, the animal is a human.

Throughout this specification, unless otherwise indicated, “comprise”, . “comprises” and “comprising” are used inclusively rather than exclusively, so that a stated integer or group of integers may include one or more other non-stated integers or groups of integers. BRIEF DESCRIPTION OF THE FIGURES In order that the present invention may be more readily understood and placed into practical effect, preferred embodiments of the invention will be described, by way of example only, with reference to the accompanying figures. FIG. 1: Schematic representation of synthesis of AdCMVpoly construct. FIG. 2: Data showing that the recombinant protein is efficiently recognized by the gB-specific monoclonal antibody. FIG. 3: Data showing that the gB-specific antibody efficiently captures the recombinant protein. FIG. 4: Representative data from two different human donors showing activation of multiple epitope-specific CTL activation following incubation with the recombinant protein.

FIG. 5: SDS-PAGE gel of resolved gB-CMV polyepitope protein and HCMV virus extract showing the molecular weight of the recombinant protein. FIG. 6: Data showing that the Human Cytomegalovirus polyepitope is highly efficient in recalling multiple CTL responses which were specific for the epitopes restricted by the HLA alleles expressed by each donor. FIG. 7: Studies showing moderate levels of T cell responses to selected epitopes following immunization with three different vectors. FIG. 8: Studies showing enhanced T cell responses following a single immunization with 1010 PFU/mice. FIG. 9: Analysis of gB-specific antibody response in serum samples from mice immunized with AdSig-gB-CMVpoly, AdgBCMV poly, control adenovirus or medium alone using ELISA assay. FIG. 10: (A) Data from mice immunized with Sig-gB-CMVpoly construct showing gB-specific antibody response and (B) test of serum samples, shows . significant neutralizing activity in mice immunized with Sig-gBCMVpoly when compared to control mice (mock immunized with control adenovirus). FIG. 11: (A) Amino acid sequence of an isolated protein for adenoviral expression in an animal; and (B) encoding nucleotide sequence. FIG. 12: (A) Ammo acid sequence of an isolated protein for recombinant protein expression in a host cell in vitro', and (B) encoding nucleotide sequence. BRIEF DESCRIPTION OF THE SEQUENCE LISTING SEQ ID NO:l: Amino acid sequence of an isolated protein for adenoviral expression in an animal (FIG 11 A). SEQ ID NO:2: Amino acid sequence of an isolated protein for recombinant protein expression in a host cell in vitro (FIG. 12A). SEQ ID NO:3: Nucleotide sequence encoding SEQ ID NO:l (FIG. 1 IB). SEQ ID NO:4: Nucleotide sequence encoding SEQ ID NO:2 (FIG. 12B). SE ID NO:5: Amino acid sequence of a HCMV polyepitope (FIG. 1). SEQ ID NOS:6-50: Amino acid sequences of HLA Class I-restricted CTL epitopes used in HCMV polyepitope (Table 1). SEQIDNO:51 & 52: Amino acid sequences of HLA Class II-restricted CTL epitopes used in HCMV polyepitope (respectively HELLVLVKKAQL and DDYSNTHSTRYV in Table 1). SEQ ID NOS: 53-55: Nucleotide sequences of gB oligonucleotides (Table 5). SEQ ID NOS: 55-79: Nucleotide sequences ofHCMVpolyepitope oligonucleotides (Table 5). SEQ ID NOS: 80-89: Nucleotide sequences of oligonucleotides for the construction of expression vectors for production of protein in mammalian cells (Table 6).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides an isolated protein comprising a Human Cytomegalovirus (HCMV) polyepitope which includes a plurality of cytotoxic T- . lymphocyte (CTL) epitopes from two or more different HCMV-derived antigenic , proteins together with an extracellular domain ofHCMV glycoprotein B for eliciting a humoral (e.g. neutralizing antibody) immune response.

More particularly, the invention provides an isolated protein, pharmaceutical compositions and methods for treatment of HCMV-associated diseases and conditions that stimulate both CTL and humoral (e.g, neutralizing antibody) responses. A particular feature of the present invention is that the isolated protein of the invention is a single, contiguous construct comprising a HCMV polyepitope sequence that elicits a strong CTL response and an extracellular domain of a gB . glycoprotein that elicits a neutralizing antibody response. .

This single, contiguous construct and a nucleic acid encoding same, is expected to be more convenient and useful for the preparation of immunotherapeutic compositions administrable to primates, particularly humans, for the treatment of diseases and conditions associated with HCMV infection.

This efficacy is unexpected given the expectation that a single, contiguous protein comprising an extracellular domain of glycoprotein B and a HCMV polytope in a highly artificial context might undergo incorrect folding and cellular processing, resulting in inadequate or faulty antigen presentation. Indeed the present inventors have surprisingly shown that each of the polyepitope and glycoprotein B components are efficiently processed by human cells for display to the immune system and that strong T cell responses are induced when HLA class I transgenic mice are immunised with this vaccine.

Significantly and suprisingly, the gB extracellular domain in the context of this single, contiguous protein, elicited a neutralizing antibody response notwithstanding the high probability that incorrect folding may have compromised the immunogenicity of the B cell epitopes present in the gB extracellular domain.

In one aspect, the invention provides an isolated protein comprising a Human Cytomegalovirus polyepitope HCMV polyepitope") amino acid sequence and an amino acid sequence of an extracellular domain of Human Cytomegalovirus glycoprotein B ("HCMV gB").

The isolated protein may be herein referred to as “gB-CMVpolyepitope" or more specifically “Sig-gB-CMVpolyepitope ’’ in cases where an N-terminal signal peptide sequence is present.

The N-terminal signal sequence may be a native gB signal sequence (e.g. residues 2-30 of gB) or atPA signal sequence.

For the purposes of this invention, by "isolated" is meant material that has been removed from its natural state or otherwise been subjected to human manipulation. Isolated material may be substantially or essentially free from components that normally accompany it in its natural state, or may be manipulated so as to be in an artificial state together with components that normally accompany it in its natural state.

By “protein ” is meant an amino acid polymer comprising natural and/or nonnatural amino acids, D- or L- amino acids as are well known in the art. A “peptide " is a protein having no more than fifty (50) amino acids. A "polypeptide" is a protein having more than fifty (50) amino acids.

The HCMV polyepitope preferably comprises a plurality of HCMV CTL epitopes derived from a plurality of different HCMV protein antigens.

In particular embodiments, the plurality of different HCMV protein antigens are selected from the group consisting of: gB, gH, pp28, pp50, pp65, pp 150, IE-1 and IE-2.

Preferably, the HCMV polyepitope comprises one or more HCMV CTL epitopes derived from each of gB, gH, pp28, pp50, pp65, pp 150, IE-1 and IE-2.

Each of the HCMV antigens were selected according to their particular properties. The viral glycoproteins gB and gH were chosen because they appear to be involved in virus attachment, whereas the IE-1 and IE-2 proteins are expressed during viral replication. IE-1 and IE-2 are considered to be important for viral reactivation and to play a role in HCMV-induced pathology. The phosphoproteins (pp28, pp50, PP65, and pp 150) are all tegument proteins. The present inventors reason that by priming the immune response to these antigens, viral replication may be controlled at the level of attachment, replication, assembly and reactivation from the latent phase, all of which are all crucial stages of HCMV infection.

The epitopes were selected to cover the HLA-A1, -A2, -A3,-All, -A23, -A24, -A26, -A29, - A30, -B7, -B8, -B27, - B35, -B38, -B40, -B41, -B44, -B5.1, -B57, -B58 specificities which are predicted to provide ca. 97 to 98 % coverage of the US human population.

However, it will be appreciated by a skilled person that epitope selected may be tailored to fit any population, irrespective of race. This percentage of individuals is expected to respond to at least one epitope in the array.

In a preferred form, also included are two HLA class Π-restricted epitopes (SEQ ID NOS: 51 & 52).

Other criteria for inclusion within the polyepitope include those (i) having minimal or no sequence variants; (ii) selected from HLAs having minimal subtypes; (iii) having a high frequency of CTL responses in healthy HCMV seropositives; and (iv) based on epitope hydrophobic properties, wherein the novel sequential order of individual epitopes are arranged such that hydrophobicity is uniform distributed along the length of the polyepitope to assist inter cellular mobility. A non-limiting example of HCMV CTL epitopes useful in a HCMV polyepitope according to the invention is provided in Table 1 (SEQ ID NOS: 6-52). A preferred HCMV polyepitope sequence is set forth in SEQ ID NO:5 (FIG. 1).

However, it will also be appreciated that other HCMV CTL epitopes may be used, such as described in International Application WO 03/000720.

Furthermore, it will be appreciated that the particular number and order of the constituent CTL epitopes may readily be altered while retaining broad HLA Class I and/or Class Π restriction and immunogenicity.

The HCMV polyepitope set forth in SEQ ID NO:5 and FIG. 1 consists of a plurality of CTL epitopes, in that there are no additional amino acid residues flanking each CTL epitope. .

However, it will be appreciated by the skilled person that additional amino acids may be included without adversely affecting HCMV polyepitope immunogenicity.

For example, the HCMV polyepitope may "consist essentially of' a plurality of HCMV CTL epitopes.

By "consist essentially of' is meant that no more than 1, 2 or 3 additional amino acids are present at an N- and/or C-terminus of one or more of the HCMV CTL epitopes.

Preferably, in embodiments where there are additional residues, the additional amino acids present in the polyepitope are amino acids that do not naturally flank the constituent epitopes present in native HCMV protein antigens.

In addition to the HCMV polyepitope, the isolated gB-CMV polyepitope protein of the invention further comprises a gB extracellular domain, or a fragment of the extracellular domain, comprising one or more B epitopes capable of eliciting a neutralizing antibody response.

Substantially the entire extracellular domain of gB is found within or . corresponds to residues 31-700 of gB.

The native gB signal sequence is residues 2-30 of gB,

In embodiments where the isolated protein is to be produced in a host cell in vitro, the extracellular domain of Human Cytomegalovirus glycoprotein B preferably includes one or more amino acid substitutions, deletions or additions that remove one or more proteolytic cleavage sites therein. A non-limiting example is one or more furin proteolytic processing sites in the extracellular domain of Human Cytomegalovirus glycoprotein B.

In particular embodiments, the one or more amino acid substitutions, deletions or additions are selected from the group consisting of: Arg433 to GI11433,

Arg435 to ΤΙ1Γ435 and Arg436 to Gln436. .

In embodiments relating to recombinant protein expression in a host cell in vitro, the isolated protein may further comprise a gB intracellular domain contiguous with the gB extracellular domain.

In this regard, the isolated protein of the invention may be a Sig-gB-CMV polyepitope protein which comprises a secretion signal sequence. . . .

In one embodiment, a native, gB secretion signal sequence may be included . at the N-terminus of a gB-HCMVpolyepitope construct resulting in increased activity compared to a construct without the signal sequence.

In another embodiment particularly suited to recombinant protein expression in a host cell in vitro, a tPA signal sequence may be included at the N-terminus of a. gB-HCMVpolyepitope construct in place of a native gB signal sequence.

It will also be appreciated that the isolated protein described herein may be subjected to further modifications, variations and/or derivitizations without departing from the inventive concept.

Variantions in amino acid sequence may be the result of naturally occurring sequence variation in a gB and/or HCMV polyepitope and/or signal peptide sequence. .

Alternatively, the invention contemplates isolated proteins which vary from those exemplified herein such as by addition, deletion or substitution of amino acid residues in the gB and/or HCMV polyepitope and/or signal peptide sequences exemplified herein.

It is well understood in the art that some amino acids may be changed to others with broadly similar properties without changing the nature of the activity of the isolated protein (conservative substitutions).

Typically, conservative substitutions are made so that amino acid properties such as charge, hydrophilicity, hydrophobicity and/or side chain size or “bulkiness” are retained or at least minimally altered.

Generally, although not exclusively, amino acid substitutions which are likely to produce the greatest changes in protein structure and/or function are those in which a hydrophilic residue is substituted for, or by, a hydrophobic residue a cysteine or proline is substituted for, or by, any other residue; a residue having a positive charge is substituted for, or by, a negative charge or a residue having a bulky side chain is substituted for, or by, one having a smaller side chain)or no side chain.

Introduction of amino acid substitutions may be readily achieved during peptide synthesis or during synthesis, of an encoding nucleic acid. Other techniques include chemical mutagenesis of an isolated protein or mutagenesis of an encoding nucleic acid. . .

Non-limiting examples of nucleic acid mutagenesis methods are provided in Chapter 9 of CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, Ausubel et al., supra, Stemmer, 1994, Proc. Natl. Acad. Sci. USA 91 10747, Shafikhani etal., 1997, Biotechniques 23 304 , Jenkins et al, 1995, EMBO J. 14 4276-4287 and Zaccolo et al., 1996, J. Mol. Biol. 255 589.

More particularly, site-directed mutagensis may be performed using a commercially available kit, for example QuickChange™ Site-Directed Mutagenesis Kit from Stratagene. .

Random mutagenesis kits are also commercially available, such as the Diversify™ random mutagenesis kit (Clontech).

Generally, the invention contemplates protein variants having at least 75%, preferably at least 80%, more preferably at least 85% or even more preferably at least 90, 91, 92, 93, 94, 95,96,97, 98 or 99% amino acid sequence identity with SEQ ID NO:l, SEQ ID NO:2, or with the constituent gB and/or HCMV polytope (such as SEQ ID NO :5) or signal peptide sequences therein.

Such levels of sequence identity may readily be determined by sequence analysis algorithms such as ClustalW or BlastP as are well understood in the art.

As used herein, "derivative ” proteins of the invention have been altered, for example by conjugation, fusion with! additional protein sequences, by complexing with other chemical moieties or by post-translational modification techniques as would be understood in the art. «Additions” of amino acids may include fusion with amino acid sequences of other proteins such as "fusion partners" or "epitope tags" which assist recombinant protein purification and/or identification.

Well known examples of fusion partners include, but are not limited to, glutathione-S-transferase (GST), Fc portion of human IgG, maltose binding protein (MBP) and hexahistidine (HIS6), which are particularly useful for isolation of the fusion polypeptide by affinity chromatography. For the purposes of fusion protein purification by affinity chromatography, relevant matrices for affinity chromatography are glutathione-, amylose-, and nickel- or cobalt-conjugated resins - respectively. Many such matrices. are available in “kit” form, such as the QIAexpress™ system (Qiagen) useful with (HIS6) fusion partners and the,Pharmacia GST purification system.

Another fusion partner well known in the art is green fluorescent protein (GFP). This fusion partner serves as a fluorescent “tag” which allows the fusion protein of the invention to be identified by fluorescence microscopy or by flow cytometry. The GFP tag is useful when assessing subcellular localization of the fusion polypeptide of the invention, or for isolating cells which express the fusion polypeptide of the invention. Flow cytometric methods such as fluorescence activated cell sorting (FACS) are particularly useful in this latter application.

Preferably, the fusion partners also have protease cleavage sites, such as for Factor Xa or Thrombin, which allow the relevant protease to partially digest the . fusion protein of the invention and thereby liberate the recombinant protein of the invention therefrom. The liberated protein can then be isolated from the fusion partner by subsequent chromatographic separation.

Fusion partners according to the invention also include within their scope “epitope tags”, which are usually short sequences for which a specific antibody is available. Well-known examples of epitope tags for which specific monoclonal antibodies are readily available include c-myc, influenza virus haemagglutinin and FLAG tags.

Other derivatives contemplated by the invention include, but are not limited to, modification to side chains, incorporation of unnatural ammo acids and/or their derivatives during peptide, polypeptide or protein synthesis and the use of crosslinkers and other methods which impose conformational constraints on the isolated protein of the invention. Examples of side chain modifications contemplated by the present invention include modifications of amino groups such as by acylation with acetic anhydride; acylation of amino groups with succinic anhydride said tetrahydrophthalic anhydride; amidination with methylacetimidate; caxbamoylation of amino groups with cyanate; pyridoxylation of lysine with pyridoxal-5-phosphate followed by reduction with NaBHj; reductive alkylation by reaction with an aldehyde followed by reduction with NaBfLi; and trinitrobenzylation of amino groups with 2, 4, 6-trinitrobenzene sulfonic acid (TNBS).

The carboxyl group may be modified by carbodiimide activation via O-acylisourea formation followed by subsequent derivitization, by way of example, to a corresponding amide.

The guanidine group of arginine residues may be modified by formation of heterocyclic condensation products with reagents such as 2,3-butanedione, phenylglyoxal and glyoxal. . .

Sulfydryl groups may be modified by methods such as performic acid oxidation to cysteic acid; formation of mercurial derivatives using 4-chloromercuriphenylsulfonic acid, 4-chloromercuribenzoate; 2-chloromercuri-4-nitrophenol, phenylmercury chloride, and other mercurials; formation of a mixed disulfides with other thiol compounds; reaction with maleimide, maleic anhydride or other substituted maleimide; carboxymethylation with iodoacetic acid or iodoacetamide; and caxbamoylation with cyanate at alkaline pH.

Tryptophan residues may be modified, for example, by alkylation of the indole ring with 2-hydroxy-5-nitrobenzyl bromide or sulfonyl halides or by oxidation with N-bromosuccinimide.

Tyrosine residues may be modified by nitration with tetranitromethane to form a 3-nitrotyrosine derivative.

The imidazole ring of a histidine residue may be modified by alkylation with iodoacetic acid derivatives.

Examples of incorporating unnatural amino acids and derivatives during peptide synthesis include but are not limited to, use of 4-amino butyric acid, 6-aminohexanoic acid, 4-amino-3-hydroxy-5-phenylpentanoic acid, 4-amino-3-hydroxy-6-methylheptanoic acid, t-butylglycine, norleucine, norvaline, phenylglycine, ornithine, sarcosine, 2-thienyl alanine and/or D-isomers of amino acids.

Typically, proteins may be produced by recombinant DNA technology or by chemical synthesis, inclusive of solid phase and solution phase synthesis. Such methods are well known in the art, although reference is made to examples of chemical synthesis techniques as provided in Chapter 9 of SYNTHETIC VACCINES Ed. Nicholson (Blackwell Scientific Publications) and Chapter 15 of CURRENT PROTOCOLS IN PROTEIN SCIENCE Eds. Coligan et al., (John Wiley & Sons, Inc. NY US A 1995-2001).

Recombinant proteins may be conveniently prepared by a person skilled in the art using standard protocols as for example described in Sambrook et al., MOLECULAR CLONING. A Laboratory Manual (Cold Spring Harbor Press, 1989), in particular Sections 16 and 17; CURRENT PROTOCOLS IN MOLECULAR BIOLOGY Eds. Ausubel et al, (John Wiley & Sons, Inc. NY USA 1995-2001), in particular Chapters 10 and 16; and CURRENT PROTOCOLS IN PROTEIN SCIENCE Eds. Coligan et al., (John1 Wiley & Sons, Inc. NY USA 1995-2001, in particular Chapters 1, 5 and 6.

In another aspect, the invention provides an isolated nucleic acid encoding the aforementioned isolated protein of the invention.

The isolated nucleic acid of the invention may be useful for recombinant protein expression in vivo in an animal, or in a host cell for the purposes of subsequent recombinant protein purification.

An example of a nucleotide sequence of an isolated nucleic acid encoding an isolated protein of the invention for adenoviral expression in an animal is provided in FIG. 11B (SEQ IDNO:3)

An example of a nucleotide sequence of an isolated nucleic acid encoding an isolated protein of the invention for recombinant protein expression in a host cell in vitro is provided in FIG. 12B (SEQ ID NO:4).

It will be appreciated by persons skilled in the art that advantage maybe taken of degeneracy in the genetic code to alter an encoding nucleotide sequence of an amino acid sequence.

In a particular example, a nucleotide sequence may be engineered according to codon preference or usage in an organism or cell type to thereby optimize encoded protein translation and expression in that organism or cell type.

The term “nucleic acid” as used herein designates single-or double-stranded mRNA, RNA, cRNA and DNA, said DNA inclusive of cDNA and genomic DNA.

Nucleic acids may comprise genetically-encoded bases such as adenine, guanine, cytosine, thymine and uracil, or modified bases such as inosine, methylinosine and methyladenosine, thiouridine and methylcytosine, although without limitation thereto.

The term "recombinanf ’ as used herein means artificially produced through human manipulation of genetic material, such as involving techniques generally falling within the scope of “recombinant DNA technology” as is well understood in the art.. , A “polynucleotide ” is a nucleic acid having eighty (80) or more contiguous nucleotides, while an “oligonucleotide” has less than eighty (80) contiguous nucleotides. A “probe” may be a single or double-stranded oligonucleotide or polynucleotide, suitably labelled for the purpose of detecting complementary sequences in Northern or Southern blotting, for example. A “primer" is usually a single-stranded oligonucleotide, preferably having 15-50 contiguous nucleotides, which is capable of annealing to a complementary nucleic acid “template” and being extended in a template-dependent fashion by the action of a DNA polymerase such as Taq polymerase, RNA-dependent DNA polymerase or SequenaseTM,

An “amplification product” refers to a nucleic acid product generated by nucleic acid amplification techniques.

Also contemplated according to the present invention are isolated nucleic acids that encode variants and/or derivatives of the isolated protein as hereinbefore described.

Typically, such isolated nucleic acids that encode variant proteins of the invention will hybridize with SEQ ID NO:3 or SEQ ID NO:4 under high stringency wash conditions. .

High stringency conditions include and encompass:. (i) from at least about 31% v/v to at least about 50% v/v formamide and from at least about 0.01 M to at least about 0.15 M salt for hybridisation at 42°C, and at least about 0.01 M to at least about 0.15 M salt for washing at 42°C; (ii) 1% BSA, 1 mM EDI A, 0.5 M NaHP04 (pH 7.2), 7% SDS for hybridization at 65°C, and (a) 0.1 x SSC, 0.1% SDS; or (b) 0.5% BSA, ImM EDTA, 40 mM NaHP04 (pH 7.2), 1% SDS for washing at a temperature in excess of 65 °G for about one hour; and (iii) 0.2 x SSC, 0.1 % SDS for washing at or above 68°C for about 20 minutes.

As hereinbefore described, the invention provides a genetic construct comprising an isolated nucleic acid of the invention.

The genetic construct may facilitate propagation, cloning and/or expression of the isolated nucleic acid.

In a preferred form, the genetic construct is an expression construct comprising an isolated nucleic acid of the invention operably linked to one or more regulatory sequences present in an expression vector.

An ‘'’'expression vector” may be either a self-replicating extra-chromosomal vector such as a plasmid, or a vector that integrates into a host genome. Suitably, the expression vector provides said one or more regulatory nucleotide sequences. By “operably linked" is meant that said regulatory nucleotide sequence(s) is/are positioned relative to the recombinant nucleic acid of the invention to initiate, regulate or otherwise control transcription.

Regulatory nucleotide sequences will generally be appropriate for the host cell used for expression. Numerous types of appropriate expression vectors and suitable regulatory sequences are known in the art for a variety of host cells.

Typically, said one or more regulatory nucleotide sequences may include, but are not limited to, promoter sequences, leader or signal sequences, ribosomal binding sites, transcriptional start and termination sequences, translational start and termination sequences, and silencer, enhancer or activator sequences.

With regard to promoters, constitutive promoters (such as CMV, SV40, vaccinia, HTLV1 and human elongation factor promoters) and inducible/repressible promoters (such as tei-repressible promoters and IPTG-, metallothionin- of ecdysone-inducible promoters) are well known in the art and are contemplated by the invention. It will also be appreciated that promoters may be hybrid promoters that combine elements of more than one promoter, such as but not limited to the SRa promoter which is a hybrid between elements of HTLV 1 and SV40 promoters.

Preferably, said expression construct also includes one or more selectable markers suitable for the purposes of selection of transformed bacteria (such as bla, kanR and tetR) or transformed mammalian cells (such as hygromycin, G418 and puromycin).

Expression constructs may be transfected, transformed or otherwise introduced into host cells by any of a number of well known techniques including, but not limited to, transformation by heat shock, electroporation, DEAE-Dextran transfection, microinjection, liposome-mediated transfection, calcium phosphate precipitation, protoplast fusion, microparticle bombardment, viral transformation and the like.

The expression vector may also include a fusion partner (as hereinbefore described and typically provided by the expression vector) so that the recombinant protein of the invention is expressed as a fusion polypeptide with said fusion partner. The main advantage of fusion partners is that they assist identification and/or purification of said fusion polypeptide.

In embodiments relating to production of a recombinant gB-CMV polyepitope protein or Sig-gB polyepitope protein, the recombinant protein may be prepared by a procedure including the steps of: (i) preparing an expression construct which comprises an isolated nucleic acid encoding the gB-CMV polyepitope protein or Sig-gB polyepitope protein, operably linked to one or more regulatory nucleotide sequences; (ii) transfecting, transforming or otherwise introducing the expression construct into a suitable host cell; (ίϋ) expressing the recombinant protein in said host cell; and (iv) purifying the recombinant protein.

The conditions appropriate for protein expression will vary with the choice of expression vector and the host cell. This is easily ascertained by one skilled in the art through routine experimentation.

Suitable host cells for expression may be prokaryotic or eukaryotic, such as Escherichia coli (DH5a for example;, yeast cells, Sf9 cells utilized with a baculovirus expression system, mammalian cell lines such as human embryonic kidney (HEK) 293 cells, CHO cells, COS cells, CV1 cells, Jurkat and NIH3T3 cells although without limitation thereto.

Preferably, the host cell is a human embryonic kidney (HEK) 293 cell stably transfected with an expression construct of the invention comprising one or more regulatory sequences (e.g. a promoter) operable in a mammalian cell..

In embodiments relating to expression constructs for administration to amrnals such as primates and particularly humans, the expression construct of the invention is suitable for use as a DNA vaccine.

In particular forms, the expression construct of the invention may be a construct that utilizes an expression and delivery vector of viral origin, such as pox viruses and adenoviruses.

When used as a vaccine delivery system, expression constructs of viral origin may be administered to an animal in the form of VLPs or as a "naked" nucleic acid construct.

In one particular embodiment, the expression construct according to this embodiment comprises a vaccinia virus promoter, such as the p7.5 promoter present in a plasmid vector. For example, production of a TK- recombinant vaccinia virus using marker rescue recombination as provided in Khanna et al., 1992. J Exp Med. 176 169.

In a more preferred embodiment, the invention provides an adenovixus-based expression construct for use in a vaccine delivery system. Adenovirus-based constructs are capable of infecting a broad spectrum of mammalian and human cells, including both quiescent and proliferating cell types.

Such adenovirus-based expression constructs may comprise a constitutive or inducible/repressible promoter such as by way of a tetracycline inducible/repressible system. A preferred form of the adenovirus-based expression construct is derived from a replication-incompetent A5 adenovirus lacking at least an El gene. A particularly preferred form is the Ad5/F35 adenovirus-based expression construct and vaccine delivery system is provided in detail hereinafter. Reference is also made to Yotdna et al., 2001, Gene Therapy 8 930, in relation to the Ad5/F35 embodiment of adenovirus expression vectors.

Pharmaceutical compositions and therapeutic uses

It will be appreciated that the isolated protein of the invention, isolated nucleic acids and expression constructs encoding same may be useful in therapeutic and/or prophylactic treatment of a Human Cytomegalovirus-associated disease and/or condition in an animal.

Preferably, the animal is a primate, such as a human.

In humans, HCMV infection can cause a mononucleosis-like syndrome with prolonged fever, and/or a mild hepatitis. In certain high-risk groups, disease can be more severe, such as during infection of the unborn baby during pregnancy, in people who work with children, and in immunocompromised persons, such as the aged, organ transplant recipients and persons infected with human immunodeficiency virus (HIV).

The invention therefore provides pharmaceutical compositions and/or methods of prophylactic or therapeutic treatment of HCMV infection, preferanly in human.

Such pharmaceutical compositions and methods are suitable for delivery of the isolated protein in recombinant form, or encoded by an expression construct (preferably in a viral delivery vector).

Suitably, pharmaceutical compositions further comprise apharmaceutically-acceptable carrier, diluent or excipient.

By “pharmaceutically-acceptable carrier, diluent or excipient” is meant a solid or liquid filler, diluent or encapsulating substance that may be safely used in systemic administration. Depending upon the particular route of administration, a variety of carriers, well known in the art may be used. These carriers may be selected from a group including sugars, starches, cellulose and its derivatives, malt, gelatine, talc, calcium sulfate, vegetable oils, synthetic oils, polyols, alginic acid, phosphate buffered solutions, emulsifiers, isotonic; saline and salts such as mineral acid salts including hydrochlorides, bromides and sulfates, organic acids such as acetates, propionates and malonates and pyrogen-free water. A useful reference describing pharmaceutically acceptable carriers, diluents and excipients is Remington’s Pharmaceutical Sciences (Mack Publishing Co. N.J. USA, 1991) which is incorporated herein by reference.

Any safe route of administration may be employed for providing a patient with the composition of the invention. For example, oral, rectal, parenteral, sublingual, buccal, intravenous, intra-articular, intra-muscular, intra-dermal, subcutaneous, inhalational, intraocular, intraperitoneal, intracerebroventricular and transdermal administration may be employed.

Dosage forms include tablets, dispersions, suspensions, injections, solutions, syrups, troches, capsules, suppositories, aerosols, transdermal patches and the like. These dosage forms may also include injecting or implanting controlled releasing devices designed specifically for this purpose or other forms of implants modified to act additionally in this fashion. Controlled release of the therapeutic agent may be effected by coating the same, for example, with hydrophobic polymers including acrylic resins, waxes, higher aliphatic alcohols, polylactic andpolyglycolic acids and certain cellulose derivatives such as hydroxypropylmethyl cellulose. In addition, the controlled release may be effected by using other polymer matrices, liposomes and/or microspheres.

In a particular embodiment relating to adenoviral delivery and expression for therapeutic purposes, the invention provides a pharmaceutical composition comprising an expression construct that encodes a Sig-gB-CMV polytope protein.

Preferred pharmaceutical compositions are "immunotherapeutic or immunogenic compositions" that provide prophylactic and/or therapeutic treatment of HCMV responsive to such immunotherapy, without necessarily eliciting a protective immune response.

In a preferred form, the immunotherapeutic composition may be a vaccine for eliciting a protective immune response in a human subject against HCMV wherein the vaccine comprises the isolated protein of the first aspect or the expression construct of the third aspect in combination with a pharmaceutically-acceptable carrier, diluent or excipient.

In embodiments relating to administration of a vaccine in the form of an expression construct, the invention provides a nucleic acid vaccine, inclusive of DNA vaccines as are understood in the art.

In this regard, the invention also provides a vaccine that comprises an expression construct that utilizes a viral vector such as an adenoviral vector or pox virus-derived vector as hereinbefore described.

Any suitable procedure is contemplated for producing such vaccines. Exemplary procedures include, eg., those described in New Generation Vaccines (1997, Levine et al., Marcel Dekker, Inc. New York, Basel, Hong Kong) which is incorporated herein by reference.

The immunotherapeutic compositions and vaccines of the invention may include an “immunologically-acceptable carrier, diluent or excipient".

The immunologically-acceptable carrier, diluent or excipient" includes within its scope water, bicarbonate buffer, phosphate buffered saline or saline and/or an adjuvant as is well known in the art. Suitable adjuvants include, but are not limited to: surface active substances such as hexadecylamine, octadecylamine, octadecyl amino acid esters, lysolecithin, dimethyldioctadecylammonium bromide, N,N-dicoctadecyl-N', N'bis(2-hydroxyethyl-propanediamine), methoxyhexadecylglycerol, and pluronic polyols; polyamines such as pyran, dextransulfate, poly IC carbopol; peptides such as muramyl dipeptide and derivatives, dimethylglycine, tuftsin; oil emulsions; and mineral gels such as aluminum phosphate, aluminum hydroxide or alum; lymphokines, QuilA and immune stimulating complexes (ISCOMS).

In a preferred form, immunotherapeutic compositions and vaccines of the invention comprise the isolated protein of the invention formulated in ISCOMS.

Generally, with regard to pharmacuetical compostions, immunotherapeutic compositons and/or vaccines, any safe route of administration may be employed for providing a patient with the composition! of the invention. For example, oral, rectal, parenteral, sublingual, buccal, intravenous, intra-articular, intra-muscular, intradermal, subcutaneous, inhalational, intraocular, intraperitoneal, intracerebroventricular, transdermal and the like may be employed. Intra-muscular and subcutaneous injection is appropriate, for example, for administration of immunogenic compositions, proteinacious vaccines and DNA vaccines.

With regard to methods of treatment of HCMV infection and/or a disease or condition associated with, or resultant from HCMV infection, the invention contemplates adoptive immunotherapy.

Preferably, although not exclusively, the invention contemplated adoptive immunotherapy using autologous CTLs produced in vitro.

Current methods for expanding HCMV CTLs are very difficult and are often based on either using a HCMV lysate or individual peptide epitopes. The isolated protein of the invention is expected to be more advantageous than either of these prior art approaches by facilitating expansion of broadly focussed T cell responses.

In one embodiment, the invention provides a method of autologous adoptive immunotherapy in a human including the steps of: (A) contacting one or more cells isolated from a human with an isolated gB-CMV polyepitope protein or a Sig-gB-CMV polyepitope protein; (B) culturing said one or more cells to thereby expand HCMV-specific CTL from said one or more cells; and (C) administering said HCMV-specific CTLs to said human to thereby prophylactically or therapeutically treat a Human Cytomegalovirus infection of said animal.

In order that the invention may be readily understood and put into practical effect, particular embodiments will now be described by way of the following nonlimiting examples. . EXAMPLES Example 1 HCMV adenoviral expression Constructs

Construction of a gB vector with and without a signal sequence HCMV encoded glycoprotein B (gB) was amplified from ADI 69 virus stock by PCR using gene specific primers (pgBSIGF, pgBNOSIGF and pgBR) as shown in Table 5. The 5’ primer included a Bam HI restriction site followed by a Kozak sequence and start codon. The 3’ primer included a Hind III restriction site. Two constructs were made, the first coding from the start methionine at position 2 to valine at position 700 thereby incorporating the signal sequence and the second coding from the alanine at position 31 to valine at position 700 with the deletion of the signal sequence. Following amplification, the DNA was gel purified, cloned into pBluescript 11 KS+ phagemid (Stratagene) and confirmed by DNA sequence analysis.

Recombinant CMVpolyepitope construction

The epitopes have been combined'using ‘Polytope’ technology as described in WO 03/000720. The amino acid sequence of the 38 contiguous HLA class I-restricted CTL epitopes of Table 1 was translated to the nucleotide sequence using human universal codon usage. Fifteen oligonucleotides (HCMVla-12 in the range of 102-107 mer as defined in Table 5) overlapping by 20 base pairs and representing the polyepitope DNA sequence, were annealed together by using Splicing by Overlap

Extension and stepwise asymmetric PCR (as schematically represented in FIG. 1). Briefly, polyepitope sequence specific primers HCMV la and HCMV lc were annealed, extended and amplified by PCR for 5 cycles in a 20pL reaction volume containing Elongase enzyme mix (Invitrogen, Australia) PCR buffers and dNTPs. At the end of 5 cycles, the PCR program was paused at 72C, 2pL of reaction was transferred to a new 20pL reaction and subjected to a further 5 cycles with primer HCMV 2 and the polyepitope sequence specific forward primer. This stepwise PCR was repeated until all oligonucleotides were joined. In the final step, 2pL of the last reaction was amplified for 25 cycles using polyepitope sequence specific forward and reverse primers.

The nucleic acid sequence of the final fragment coded for an EcoR I restriction site, a start codon, 38 contiguous minimal CMV CTL epitopes, followed by a Hind III restriction site. The full-length gel purified PCR fragment was cloned into the EcoR I/Hind III site of pBluescript IIKS+ phagemid and was confirmed by DNA sequence analysis.

An additional 8 contiguous HLA class I restricted CTL epitopes were added to the above construct using Splicing by Overlap Extension and stepwise asymmetric PCR involving oligonucleotides extPl to extP3 as described above. The final PCR fragment was cloned into the Cla I/Xho I site of pBluescript IIKS+ phagemid and confirmed by DNA sequence analysis. The original construct encoding the 38 contiguous HLA class I restricted CTL epitopes was then re-cloned into the Eco RI/Hmd III restriction sites of this construct, resulting in a final construct containing 46 CTL epitopes.

The final CMV polyepitope was coded for an Eco RI restriction site, a Kozak sequence, 38 contiguous HLA class I restricted CTL epitopes, a Hind III site, a CM site, 8 additional epitopes and a Xho I restriction site.

Construction of gB-CAfVpolytope vectors

The recombinant CMV polytope construct insert was excised from the pBluescript IIKS+phagemid using the Eco Rl/Xho I restriction enzymes, cloned into the gB pBluescript vectors and confirmed by DNA sequence analysis. The final constructs are shown below and summarized in Table 2.

Construction of recombinant AdSF35 vectors

The adenovirus-based expression vector AD5/F35 allows highly efficient transduction of professional antigen presenting cells in vitro and in vivo. The assembly and production of the recombinant Ad5F35-based adenovirus was completed in three stages using a highly efficient, ligation-based protocol (Mizuguchi & Kay, 1998, Hum.Gene Ther., 9 2577;:Mizuguchi & Kay, 1999, Hum.Gene Ther., 10 2013) of the Adeno-X System (CLONTECH, Palo Alto, CA) (FIG. 1).

Firstly, inserts were excised from each of four constructs (1, 2, 4 and 5 in Table 2) in pBluescript IIKS+ phagemid using Xba I/Kpn I restriction enzymes and cloned into the pShuttle expression vector which contains a stop codon following the cloning sites in the three open reading frames. Following amplification in E. coli, the expression cassette from pShuttle was excised using I-Ceu 1/ ΡΙ-Sec I restriction enzymes and cloned into an Ad5F35 expression vector. The recombinant Ad5F35 vector was transfected into human embryonic kidney (HEK) 293 cells and recombinant adenovirus (referred to as AdCMVpoly) was harvested from the transfected cells by successive freeze-thawing cycles.

Example 2

Antigenicity Studies with Recombinant Protein

Immunogenicity testing of recombinant protein by ELISA

In the first set of experiments, the antigenicity of the recombinant protein using standard ELISA assay was tested. Ninety-six well micro-titre plates were coated with serially diluted (1:5 0 to 1:102,400) concentrated recombinant protein. These plates were then incubated with anti-gB monoclonal antibody (2F12,1:8000, Abeam, UK) followed by incubation with secondary antibody (HRP-conjugated antimouse Ig, 1:10,000). After extensive washing, the TMB chromogen substrate was added and the OD was read by ELISA reader. Data in Table 3 and in FIG. 2 shows that the recombinant protein is efficiently recognized by the gB-specific monoclonal antibody.

In subsequent experiments, capture ELISA was used to assess the reactivity of the recombinant protein with gB-specific antibody. Ninety-six well micro-titre plates were coated with gB-specific antibody (l-M-12) at dilutions 1:500 (Well 1-3) or 1.1500 (well 4-9) or buffer alone (well 10-12). In each well, recombinant gB-CMV polyepitope protein was added at a dilution of 1:1000 and incubated at 37 °C for 1 h. In the next step, serially diluted rabbit polyclonal antibody specific for gB was added in each well (Wells 1-3: 1:200, 1:400; 1:800 and Wells 4-9: 1:200, 1:400, 1:800, 1:1600,1:3200,1:6400 and 1:12800); In wells 9-12, only coating buffer was added. After incubation at 37 °C for 1 h, the plates were washed and secondary antibody (HRP-conj ugated anti-rabbit Ig; 1:10,000) was added. Following extensive washing, the TMB chromogen substrate was added and OD was read by ELISA reader. The data m Table 4 and FIG. 3 shows that the gB-specific antibody efficiently captures the recombinant protein.

Immunogenicity testing of recombinant HCMVpolyepitope protein by CTL assay

The immunogenicity of the recombinant HCMV polyepitope protein by stimulating human T cells was tested. Briefly, PBMC from healthy seropositive donors were stimulated with the recombinant protein and on day 10 these T cells were tested for a HCMV epitope-specific CTL response. Representative data from two different donors are presented in FIG. 4. Both donors showed activation of multiple epitope-specific CTL activation following incubation with recombinant protein.

Example 3

Recombinant protein production in mammalian cells Synthesis of tPA signal sequence A tPA secretion signal sequence or ‘Sig’ was attached to the gB-CMV- polyepitope construct using the following method. Oligonucleotides TPAS-F and TPAS-R (see Table 3) incorporating a tPA signal sequence with kozak sequences were annealed, extended and the DNA fragment was inserted into into pGEM-T (Promega, USA) vector. E.coli DH5a (Invitrogen, USA) was transformed using the ligated products and screened by PCR for the positive clones containing the inserted fragment. The positive colonies were amplified and the plasmids pGEM-tPA were extracted, purified, identified by restriction endonuclease cleavage and the inserted tPA DNA fragment was confirmed by DNA sequencing. The plasmid pGEM-tPA and mammalian expression vector pCEP4 (Invitrogen, USA) were cleaved by Κρη I and Nhe I restriction endonucleases and ligated using T4 DNA ligase. The transformation, amplification and plasmid purification were carried as above, and expression vector pCEP4-tPAS was obtained. By attaching the secretion signal sequence or ‘Sig’ to the gB-CMV-polyepitope construct, increased activity over the construct without the signal sequence was found.

The mutagenesis of gB furin site A plasmid pBluscript II-AgB which contains a 2100-bp fragment of gB extracellular domain (nucleotide [nt] 81703 to 83805 of the HCMV sequence accession No: NC-001347) was constructed as described above. In order to remove the furin proteolytic processing site, three site-specific point mutations were introduced in the AgB by using primers gBmutPl and gBmutP2, resulting three amino acid changes as follows: Arg433 to GI11433, Arg435 to Thr435 and Arg436 to GI11436.

Removal of native gB signal sequence

In order to remove the gB native signal sequence and facilitate the cloning manipulation, two primers were designed to include both Xba I and Nhe I restriction site in NHEGB-F and Sac II and EcoR I restriction sites in PETGB-R. A 640-bp DNA fragment of gB was amplified by PCR with primers PETGB-R and NHEGB-F using plasmid pBluscript Π-AgB as template. The purified fragment and plasmid vector pET-26b(+) (Novagen, USA) were cleaved by Xba I and EcoR I and ligated. The transformation, amplification and plasmid purification were carried out as described above and the resulting plasmid pET-26b(+)-agB was obtained. The inserted fragment was sequence confirmed. A 1400-bp DNA fragment was cleaved from plasmid pBluscript II-AgB by SacII and Hindlll and was inserted into the SacII and Hindlll sites of vector pET-26b(+)-agB to produced the plasmid of pET-26b(+)-PgB.

Fusion of extracellular domain and cytoplasmic domain of gB

For construction of the ygB encoding the extracellular domain (residues Seri to Val676) and the C-terminal cytoplasmic domain (residues Lys753 to Vals82), the cytoplasmic portion of gB was amplified from AD 169 DNA with primers GBTAIL-F and GBTAIL-R, the PCR fragment was purified and cleaved by Hind HI and Not I restriction enzymes and inserted into the corresponding sites in plasmid pET-26b(+)-PgB. The transformation, amplification and plasmid purification were carried as previously described and the resulting plasmid pET-26b(+)-ygB was obtained. The inserted cytoplasmic portion of gB was sequence confirmed by DNA sequencing.

His taggedpolytope2 andfusion with ygB synthesis

The plasmid containing the 1320-bp synthetic DNA fragment covering 46 T-cell epitopes was constructed as described above. The primers of CMVP-F (with a terminal Not I site) and Polyhistop 2 (with terminal 6XHis tag, stop codon and Xho I site) were used to amplify the 1320bp DNA fragment by PCR. The PCR fragment was purified and cleaved by Notl and Xhol, and then subcloned into pBluscript H to obtain pBluscript II-Apoly2. The insert was confirmed by DNA sequencing. The pBluscript II-Apoly2 was cut with Notl and Xhol and the fragment was subcloned into the plasmid pET-26b(+)-ygB to obtain the plasmid pET-26b(+)-ygB-Apoly2.

Assembly of the full length mammalian expression vector A 3840bp DNA fragment encoding gB extracellular domain linked to cytoplasmic domain and CMV polyepitope was cleaved from plasmid pET-26b(+)-PgB-Apoly2 by Nhe I and Xho I restriction enzymes, purified and ligated with vector pCEP4-tPAS digested by Nhe I and Xho I. The transformation, amplification and plasmid purification were carried out as previously described and the resulting expression plasmid pCEP4-tPAS-ygB-Apoly2 was obtained. The full sequence of the inserted 3.8 kb fragment was confirmed by DNA sequencing.

Stable transfection of293E cells

Stable transfection of pCEP4-tPAS-ygB-Apoly2 was achieved by using Effectene (Qaigen) according to the manufacture’s instruction. Apopulation of stable transfection was obtained by selection with hygromycin B over a period of 2 weeks. Clonal cell lines were isolated by plating one cell per well in 96-well plates in DMEM containing 10 % FCS and 150 pg/ml of hygromycin.

Production of recombinant protein A positive cloned 293E cell line was expanded to grow to confluency in 125ml flasks in DMEM containing 10% FCS and 150pg/ml of hygromycin B. The medum was discarded and cells washed with PBS. FreeStyle 293 expression media (Invitrogen, USA) were added to the cells to grow for additional 5 days. After harvest of the supernatant, the medium was cleared of detached cells and debris by . centrifugation at 110,000 g. The supemantant was concentrated 100 times by Centricon Plus-80 (Millipore) and stored in -80 C°.

To confirm the integrity of the recombinant protein, concentrated gB-CMV polyepitope protein and HCMV virus extract was resolved on SDS-PAGE gel and then transferred to a nitrocellulose membrane. This membrane was probed with gB-specific monoclonal antibody (2F12, 1:8000, Abeam, UK). Confirmatory data in FIG. 5 shows the expected molecular weight of the recombinant protein.

Example 4

Preclinical testing of CMV polyepitope vaccine

The adenoviral HCMV polyepitope vaccine was used to restimulate a secondary CTL response in vitro from PBMC obtained from healthy HCMV seropositive individuals. The resulting polyclonal cultures were used as effectors against autologous PHA blasts sensitized with HCMV peptide epitopes.

Data in FIG. 6 clearly shows that the HCMV polyepitope was highly efficient in recalling multiple CTL responses which were specific for the epitopes restricted by the HLA alleles expressed by each donor. For instance, the HCMV polyepitope stimulated a strong T cell response to the epitopes VTE (pp50, HLA A1 -restricted), ELR and QIK (both I-E-1, HLA B 8-restricted) and IPS (HLA B3 5-restricted, pp65) from donor TC (HLA Al, All, B8, B35). Another donor who was HLA A2-positive showed strong reactivation of NLV-specific (HLA A2-restricted, pp65) CTL response. Similarly, multiple epitope-specific CTL responses were also detected from other donors.

Significantly, these results demonstrate that the covalent linking of gB to the HCMV polyepitope did not influence endogenous processing and presentation of CTL epitopes.

Example 5

In vivo assessment of the immunogenicity of a HCMV polyepitope vaccine

The immunogenicity of each HCMV polyepitope vaccine in vivo was assessed. HEA A2/Kb transgenic mice were immunized intra-peritoneally with recombinant adenovirus HCMV polyepitope vaccine (CMVpoly, gBCMVpoly or Sig-gB-CMVpoly) using standard procedures. A first set of immunizations were carried out using lxlO9 PFU/mouse. Specific T cell reactivity towards HLA-A2-restricted epitopes was assayed on peptide-pulsed targets by enumeration of IFNy-secreting CD8 cells by the ELISPOT method [peptides: NLV (pp65), VLE (IE-1), RIF (pp65), IIY (IE-2), VLA (IE-1) and AVG (gB), all restricted through HLA-A2j]. These studies showed moderate levels of T cell responses to these epitopes following immunization with three different vectors (FIG. 7).

To determine whether the level of T cell responses could be further enhanced by immunizing mice with higher dose of a HCMV polyepitope vaccine, a group of HLA A2/Kb mice were immunized with Sig-gB-CMVpoly at 1010 PFU/mouse. Indeed and surprisingly, a single immunization with 1010 PFU/mice significantly enhanced the T cell responses (FIG. 8). These responses were ca. 3-10 times higher than those seen in mice immunized with 109 PFU.

Example 6

Induction of gB-specific neutralizing antibody response IE-l/IE-2 HCMVNeutralisation Assay

Reagents MRC5 fibroblasts; DMEM-0, DMEM-10; 100% MeOH; PBS-5% FCS; mouse anti-CMV monoclonal antibody Cat.# MAB810 lmg/mL, Ig2a Chemicon International (Silenus); Sheep anti-mouse Ig Fraction affinity isolated Horse Radish Peroxidase conjugated. Product code DAH Cat.# 985033020 2mL Chemicon Australia Pty Ltd (Silenus) 96 well plates; Peroxidase Block (DakoCytomation, S2001) [0.03% H2O2 and NaNs make yourself in PBS], DAB+ Chromagen (Dakocytomation, K3467)

Neutralisation of HCMV with mouse serum and infection ofMRC5 fibroblasts

Plate MRC5 into 96 well culture plates (2), (should be 80-90% confluent for virus addition). Grow MRC5 cells in DMEM-10, split prior to assay and give 100pL ofalxlO5 cells/mL suspension in DMEM-10 to wells of a 96 well flat bottom plate to promote an even monolayer of cells. Culture overnight to ensure attachment. Observe culture and when monolayer is ,80-90% confluent proceed with assay. Prepare dilutions of sera in a 96 well “U” bottom plate with DMEM-0, remember to change tips between dilutions, ranging from 1/4,1/8,1 /16 to 1/512 for final range of 1/8,1/16,1/32 to 1/1024 leaving 25pL of the dilution in each well

Add 25pL of HCMV Adi 69 too each serum or control well of the 96 well “U” bottom plate.

Incubate the plate at 37°C for 2 hours.

Aspirate all culture media from the MRC5 culture plate wells. Transfer 25pL of virus-serum suspension to corresponding wells of the MRC5 culture plate. Infect for 2 hours, rocking the plate gently every 15 min for the first hour, at 37°C and 7%C02.

Following incubation aspirate all the innoculum from the wells and wash five times with DMEM-10 then add 200pL of DMEM-10 to each well and return to culture at 37°C and 7%C02 for a further 12 to 16 hours. IE-1/IE-2 detection by Horse Radish Peroxidase Staining

Remove all media from culture wells.Wash wells twice with PBS-5%. Fix cells with ice cold 100% MeOH (100pL 20-30 minutes). Wash cells twice in PBS-5%. Add 1 drop of Peroxidase Block (DakoCytomation, S2001) and leave for 5-10 minutes. Wash cells twice in PBS-5% at room temperature. Add 25pL of 1/400 anti-ffi-l/IE-2 mAb (freshly diluted in PBS) and incubate for 1-2 hours at room temperature. Wash wells three times with PBS-5% (gently with wash bottle is OK)

Add 50pL of 1/200 Sheep antilmouse Ig-HRP (freshly diluted in PBS) and incubate ovemight/2hours.Wash wells three times with PBS-5%.

Add 20pL of DAB+ Substrate Solution too each well and incubate until color develops. Wash wells three times with PBS. Add 100pL PBS too each well.

Determination of Neutralising titer

The 50%-inhibition endpoint calculated using the Reed-Miinch method was considered the neutralizing titer (NT) NT=reciprocal sera dilution [>50% inhibition] x [(/o inhibition greater than 50% - 50%)/(% inhibition greater than 50% - % inhibition less than 50%)]

View and count (Positive nuclei in five fields for each of the three replicates - only where MRC5 layer is not disrupted) with inverted microscope.

Plot average number of nuclei versus the inverse titre.

Determine the 50% positive nuclei value for the virus alone (no serum) and draw a horizontal line (50% NeutLine).

Determine the 50% neutralizing titer for each of the serum samples by finding the intersection of the serum plot and the 50%NeutLine.

Results

Having previously established the best immunizing dose for the induction of T cell response, the ability of the vaccine comprising the construct Sig-gB-CMVpoly to induce gB-specific antibody response was subsequently assessed. Serum samples from HLA A2/Kb mice immunized with Sig-gB-CMVpoly were collected three weeks after single immunization and tested for gB-specific antibody response by immunoblotting. Serum samples from mock immunized mice were used as a control. FIG. 9 shows the analysis of gB-specific antibody response in serum samples from mice immunized with Adsig-gB-CMVpoly, AdgBCMV poly, control adenovirus or medium alone using ELISA assay. HCMV virus lysates were resolved on SDS-PAGE gel and then transferred on to nitrocellulose sheets. These sheets were cut into strips and incubated with serum samples from mice or a gB-specific monoclonal antibody (as apositive control). The data in FIG. 10A clearly shows that 4/6 mice immunized with the Sig-gB-CMVpoly construct showed gB-specific antibody response.

More importantly, as shown in FIG. 1 OB, serum samples showed significant neutralizing activity in 15 mice immunized with Sig-gB-CMVpoly when compared to 4 control mice (mock immunized with control adenovirus).

These observations clearly show that covalent linking of gB with the polyepitope sequence does not impair the immunogenicity of the individual components of the vaccine. Of particular interest was the ability of the covalently-linked gB to induce neutralizing antibodies which suggests that this chimeric construct is able to maintain the tertiary structure of gB and thus allows the presentation of this protein to the humoral arm of the immune system. It is also imperative to point out that covalent linking of gB does not impede the presentation of CD8+ T cell epitopes from the polyepitope sequence (see FIGS 7 & 8).

The present inventors further hypothesize that an immunogenic component of a vaccine exclusively for use in transplant patients could be based solely on epitope-related technology, i.e. it is contemplated that constructs without conjugated gB would be sufficient to provide protection against the adverse outcomes of HCMV infection, as protection against disease rather than virus transmission is required.

It will be appreciated that the vaccines comprising the HCMV constructs of the present invention overcome two very important limitations of previous vaccines. Specifically, the new constructs are capable of inducing T cell responses to multiple antigens and are capable of inducing antibody response which shows neutralization of the virus within the same formulation. No vaccine thus far has achieved these two objectives within a single formulation. Such singly formulated vaccines provide substantial commercial advantages over the prior art.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.

All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference in their entirety.

Table 1. List of HCMV epitopes included in the polyepitope

Table 2.

Table 3.

Table 4.

Table 5, Oligonucleotides used for construction of CMV vaccine vectors for adenoviral expression

Table 6. Oligonucleotide sequences for the construction of expression vectors for protein production in mammalian cells

Claims (39)

1. An isolated protein comprising a Human Cytomegalovirus (HCMV) polyepitope amino acid sequence that comprises a plurality of epitopes capable of eliciting a cytotoxic T-lymphocyte (CTL) response, the epitopes derived from gH, pp28, pp50, pp65, pp 150, IE-1 and/or IE-2 HCMV antigens; and an amino acid sequence of an extracellular domain of Human Cytomegalovirus glycoprotein B, or a fragment that comprises at least 75% thereof and comprises one or more B cell epitopes capable of eliciting a neutralizing antibody response.

2. The isolated protein of Claim 1, wherein the epitopes capable of eliciting a cytotoxic T-lymphocyte (CTL) response provide interracial coverage of the human population.

3. The isolated protein of Claim 2, wherein the epitopes are restricted by the HLA class I specificities HLA-A1, -A2, -A3, -All, -A23, -A24, -A26, -A29, - A30, -B7, -B8, -B27, - B35, -B38, -B40, -B41, -B44, -B51, -B57 and -B58.

4. The isolated protein of Claim 1, wherein the polyepitope further comprises one or more HLA class Π-restricted CTL epitopes.

5. The isolated protein of Claim 4, wherein the epitopes have an amino acid sequence selected from the group consisting of the amino acid sequences set forth in SEQ ID NOS: 6-52.

6. The isolated protein of Claim 5, wherein the polyepitope comprises each of the amino acid sequences set forth in SEQ ID NOS: 6-52.

7. The isolated protein of Claim 6, wherein the polyepitope has an amino acid sequence is set forth in SEQ ID NO:5.

8. The isolated protein of Claim 1, comprising said extracellular domain of Human Cytomegalovirus glycoprotein B.

9. The isolated protein of Claim 1, comprising said fragment of the extracellular domain.

10. The isolated protein of Claim 8 or Claim 9, wherein the extracellular domain or fragment thereof is within amino acid residues 31-700 of gB.

11. The isolated protein of Claim 1, wherein the extracellular domain of Human Cytomegalovirus glycoprotein B, or the fragment thereof, includes one or more amino acid substitutions, deletions or additions that remove one or more furin proteolytic cleavage sites normally present in said extracellular domain or said fragment.

12. The isolated protein of Claim 11, comprising a plurality of amino acid substitutions which remove said furin proteolytic cleavage site.

13. The isolated protein of Claim 12, wherein the plurality of amino acid substitutions are Arg433 to GI11433, Arg435 to Thr435 and Arg^ to GI11436.

14. The isolated protein of Claim 13, further comprising a cytoplasmic domain of glycoprotein B contiguous with said extracellular domain or said fragment thereof.

15. The isolated protein of Claim 14, further comprising a secretion signal amino acid sequence at the N-terminus of said extracellular domain or said fragment thereof.

16. The isolated protein of Claim 15, wherein the a secretion signal amino acid sequence is a native gB secretion signal amino acid sequence or a tPA secretion signal amino acid sequence.

17. An isolated protein comprising: (I) a Human Cytomegalovirus polyepitope amino acid sequence having an amino acid sequence set forth in SEQ ID NO:5; (II) an amino acid sequence of an extracellular domain of Human Cytomegalovirus glycoprotein B which comprises one or more B cell epitopes capable of eliciting a neutralizing antibody response, wherein there are one or more amino acid substitutions selected from the group consisting of: Arg433 to GI11433, Arg435 to Thr435 and Arg436 to Gln43f,; (III) a cytoplasmic domain of glycoprotein B contiguous with said extracellular domain; and (IV) a secretion signal amino acid sequence at the N-terminus of said extracellular domain.

18. An isolated nucleic acid encoding the isolated protein of Claim 1 or Claim 17.

19. The isolated nucleic acid of Claim 18, comprising a nucleotide sequence set forth in SEQ ID NO:3 or SEQ ID NO:4.

20. An expression construct comprising the isolated nucleic acid of Claim 18 operably linked to one or more regulatory sequences in an expression vector.

21. The expression construct of Claim 20 which is suitable for administration to an animal.

22. The expression construct of Claim 21, wherein the expressi on vector i s a viral vector.

23. The expression construct of Claim 22, wherein the viral vector is an adenovirus-based vector or a pox virus vector.

24. The expression construct of Claim 23, wherein the expression vector is an adenovirus-based expression vector.

25. The expression construct of Claim 24, wherein the adenovirus-based expression vector is an Ad5/F35 vector.

26. The expression construct of Claim 20, suitable for recombinant production of the isolated protein in vitro.

27. A host cell comprising the expression construct of Claim 20.

28. The host cell of Claim 27, which is a cell isolated from an animal to which the expression construct has been administered.

29. The host cell of Claim 27, wherein the host cell has been transfected with the expression construct in vitro.

30. The host cell of Claim 28 or Claim 29, which is a mammalian host cell.

31. A pharmaceutical composition comprising the isolated protein of Claim 1 or Claim 17 or the expression construct of Claim 20 and a pharmaceutically-acceptable carrier, diluent or excipient.

2. The pharmaceutical composition of Claim 31 which is an immunotherapeutic composition suitable for use in the prophylactic or therapeutic treatment of a disease or condition associated with HCMV infection in an animal.

33. The pharmaceutical composition of Claim 32, wherein the immunotherapeutic composition is a vaccine for eliciting a protective immune response against HCMV.

34. A method of prophylactically or therapeutically treating a Human Cytomegalovirus infection in an animal including the step of administering to the animal the isolated protein of Claim 1 or Claim 17 or the expression construct of Claim 20.

35. The method of Claim 34, which includes the step of inducing both cytotoxic T-lymphocyte (CTL) and a neutralizing antibody response in said animal.

36. Use of the isolated protein of Claim 1 or Claim 17 or the expression construct of Claim 20 in the manufacture of a medicament for prophylactically or therapeutically treating a Human Cytomegalovirus infection in an animal.

37. A method of expanding human CMV-specific CTLs for adoptive immunotherapy, including the steps of: (i) contacting one or more cells isolated from an animal with the i solated protein of Claim 1 or Claim 17; and (ii) culturing said one or more cells to thereby expand HCMV-specific CTL from said one or more cells

38. A method of adoptive immunotherapy including the step of administering the HCMV-specific CTLs produced at step (ii) of Claim 37 to an animal to thereby prophylactically or therapeutically treat a Human Cytomegalovirus infection of said animal.

39. The method of Claim 38, wherein the administered CTLs are autologous CTLs.

40. The method of any one of Claims 34, 35 or 37-39 or the use of Claim 36, wherein the animal is a human.