WO2009150419A1

WO2009150419A1 - Fructose biphosphate aldolase (fba) in neisseria

Info

Publication number: WO2009150419A1
Application number: PCT/GB2009/001452
Authority: WO
Inventors: David Patrick James Turner; Karl Graham Wooldridge
Original assignee: The University Of Nottingham
Priority date: 2008-06-12
Filing date: 2009-06-10
Publication date: 2009-12-17
Also published as: GB0810742D0

Abstract

The invention relates to antigenic polypeptides expressed by the bacteria Neisseria meningitidis (meningococcus) and Neisseria gonorrhoeae (gonococcus), vaccines comprising the antigenic polypeptides and therapeutic antibodies directed to the antigenic polypeptides.

Description

FRUCTOSE BIPHOSPHATE ALDOLASE (FBA) IN NEISSERIA

Field of the Invention

The invention relates to antigenic polypeptides expressed by bacteria, vaccines comprising the antigenic polypeptides and therapeutic antibodies directed to the antigenic polypeptides.

Background to the Invention

House keeping enzymes are ubiquitous in all cells and perform key roles in essential metabolic pathways. The old idea that one protein can only perform one function has now been dramatically changed with the concept of 'moonlighting proteins', which can perform multiple functions unrelated to their well known function in the cytoplasmic environment. Glycolytic enzymes are a good example of this phenomenon.

In addition to their cytoplasmic location, several glycolytic enzymes have been reported on the surface of a number of bacterial cells, and shown to possess diverse, non- glycolytic (moonlighting) biological functions. The export of such proteins to the cell surface has mostly been described via non-classical secretion pathways. Once on the surface of bacterial cells, these proteins have been reported to act as putative virulence factors. Recently, enolase (EC 4.2.1.11) was described as a surface-localised protein in Neisseria meningitidis, where it acts as a plasminogen receptor recruiting plasminogen onto the bacterial surface (Knaust et al. J Bacteriol; 189: 3246-55, 2007). Glyceraldehyde 3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) has also been reported on the meningococcal surface but no function has so far been described.

In Streptococcus pneumoniae, fructose bisphosphate aldolase (FBA; a type Il zinc- dependent enzyme involved in glycolysis) was shown to be present on the surface of the bacterial cell. Furthermore, FBA was demonstrated to be immunogenic in humans and capable of eliciting a protective immune response (Ling et al. Clin Exp Immunol 2004; 138: 290-8, 2004). Moreover, FBA has been shown to be expressed in Streptococcus suis, and has been demonstrated to be localised to the cell wall and is immunogenic.

There remains, however, a need for agents that are useful in the prevention and treatment of other bacterial infections, in particular those caused by Gram-negative bacteria, such as infections due to Neisseria meningitidis (the 'meningococcus') and Neisseria gonorrhoeae (the 'gonococcus').

In most cells, FBA (EC 4.1.2.13) performs a critical step in glycolysis (Embden Meyerhof Parnas pathway; EMP), and is consequently predicted to be an essential enzyme in eukaryotic and prokaryotic cells. However, the genome sequence of N. meningitidis lacks one of the enzymes in the EMP pathway (phosphofructokinase; EC 2.7.1.11), and the EMP pathway was shown to be non-functional and consequently does not contribute to pyruvate synthesis. Glucose is instead metabolised via the Entner Douderoff pathway and the Pentose Phosphate pathways.

Two types of FBA are recognised, designated type I and type II, respectively. The type I enzymes are typically found in higher eukaryotic organisms, whereas the type Il enzymes are usually present in bacteria and yeast cells. In E. coli, and a few other bacteria, type Mike enzymes have also been reported. Although performing the same function, structurally and mechanistically, the type I and Il enzymes are very different, for example the type I and type Il enzymes share little or no identity at the sequence level.

The FBA (type II) homologue in the N. meningitidis (meningococcus) genome was identified by homology searches and has been partially characterised. The present inventors have identified this protein as being a potentially important target for the development of vaccines that are protective against, inter alia, pathogenic Neisseria.

Statements of the Invention

According to a first aspect of the invention there is provided an antigenic polypeptide, or variant thereof, encoded by an isolated nucleic acid sequence selected from the group consisting of: i) a nucleic acid sequence as shown in Figure 1 ; ii) a nucleic acid sequence which hybridises to the sequence identified in (i) above; and iii) a nucleic acid sequence that is degenerate as a result of the genetic code to the nucleic acid sequence defined in (i) or (ii) for use as a medicament. In an embodiment of the invention the antigenic polypeptide, or variant thereof, is encoded by an isolated nucleic acid sequence as shown in Figure 2.

In a preferred aspect of the invention the medicament is a vaccine.

The nucleic acid encoding the antigenic polypeptide of the first aspect of the invention may anneal under stringent hybridisation conditions to the nucleic acid sequence shown in Figure 1 or to its complementary strand.

Hybridization of a nucleic acid molecule occurs when two complementary nucleic acid molecules undergo an amount of hydrogen bonding to each other. The stringency of hybridization can vary according to the environmental conditions surrounding the nucleic acids, the nature of the hybridization method, and the composition and length of the nucleic acid molecules used. Calculations regarding hybridization conditions required for attaining particular degrees of stringency are discussed in Sambrook et al., Molecular Cloning: A Laboratory Manual (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 2001); and Tijssen, Laboratory Techniques in Biochemistry and Molecular Biology — Hybridization with Nucleic Acid Probes Part J, Chapter 2 (Elsevier, New York, 1993). The T_m is the temperature at which 50% of a given strand of a nucleic acid molecule is hybridized to its complementary strand. The following is an exemplary set of hybridization conditions and is not limiting:

Very High Stringency (allows sequences that share at least 90% identity to hybridize) Hybridization: 5x SSC at 65⁰C for 16 hours

Wash twice: 2x SSC at room temperature (RT) for 15 minutes each

Wash twice: 0.5x SSC at 65°C for 20 minutes each

High Stringency (allows sequences that share at least 80% identity to hybridize) Hybridization: 5x-6x SSC at 65°C-70°C for 16-20 hours

Wash twice: 2x SSC at RT for 5-20 minutes each

Wash twice: 1x SSC at 55°C-70°C for 30 minutes each

Low Stringency (allows sequences that share at least 50% identity to hybridize) Hybridization: 6x SSC at RT to 55°C for 16-20 hours

Wash at least twice: 2x-3x SSC at RT to 55°C for 20-30 minutes each. The nucleic acid encoding the antigenic polypeptide of the first aspect of the invention may comprise the sequence set out in Figure 1 or a sequence which is at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, for example 98%, or 99%, identical to the nucleic acid sequence set out in Figure 1 at the nucleic acid residue level. The nucleic acid encoding the antigenic polypeptide of the first aspect of the invention may comprise the sequence set out in Figure 2.

"Identity", as known in the art, is the relationship between two or more polypeptide sequences or two or more polynucleotide sequences, as determined by comparing the sequences. In the art, identity also means the degree of sequence relatedness between polypeptide or polynucleotide sequences, as the case may be, as determined by the match between strings of such sequences. Identity can be readily calculated (Computational Molecular Biology, Lesk, A.M. ed., Oxford University Press, New York, 1988; Biocomputing: Informatics and Genome Projects, Smith, D.W., ed., Academic Press, New York, 1993; Computer Analysis of Sequence Data, Part I, Griffin, A.M., AND Griffin, H. G., eds., Humana Press, New Jersey, 1994; Sequence Analysis in Molecular Biology, von Heinje, G., Academic Press, 1987; and Sequence Analysis Primer, Gribskov, M. and Devereux, J., eds., M Stockton Press, New York, 1991). While there exist a number of methods to measure identity between two polynucleotide or two polypeptide sequences, the term is well-known to skilled artisans (Sequence Analysis in Molecular Biology, von Heinje, G., Academic Press, 1987; Sequence Analysis Primer, Gribskov, M. and Devereux, J., eds., M Stockton Press, New York, 1991 ; and Carillo, H., and Lipman, D., SIAM J. Applied Math., 48: 1073 (1988). Methods commonly employed to determine identity between sequences include, but are not limited to those disclosed in Carillo, H., and Lipman, D., SIAM J. Applied Math., 48: 1073 (1988). Preferred methods to determine identity are designed to give the largest match between the sequences tested. Methods to determine identity are codified in computer programs. Preferred computer program methods to determine identity between two sequences include, but are not limited to BLASTP, BLASTN, and FASTA (Atschul, S.F. et al., J. Molec. Biol. 215: 403 (1990)).

The nucleic acid encoding the antigenic polypeptide of the first aspect of the invention may comprise of a fragment of a sequence according to the first aspect which is at least 30 bases long, for example, 40, 50, 60, 70, 80 or 90 bases in length.

The nucleic acid sequence encoding the antigenic polypeptide of the first aspect of the invention may be genomic DNA, complementary DNA (cDNA) or RNA₁ for example messenger RNA (mRNA).

Preferably, the antigenic polypeptide of the first aspect of the invention is expressed by a pathogenic organism, for example, a bacterium. The bacterium may be a Gram-positive or Gram-negative bacterium. Preferably the bacterium is a Gram-negative bacterium for example a bacterium from the genus Neisseria. The bacterium may be Neisseria meningitidis (meningococcus) or Neisseria gonorrhoeae (gonococcus).

In a preferred embodiment of the invention, the antigenic polypeptide of the first aspect of the invention is associated with infective pathogenicity of an organism as defined herein.

In a further preferred aspect of the invention the antigenic polypeptide comprises the amino acid sequence shown in Figure 1 or a variant sequence thereof.

The terms "polypeptide", "peptide" and "protein" are used interchangeably herein to refer to polymers of amino acids of any length. The polymer may be linear or branched, it may comprise modified amino acids or amino acid analogs, and it may be interrupted by non- amino acids. The terms also encompass an amino acid polymer that has been modified naturally or by intervention; for example, disulfide bond formation, glycosylation, lipidation, acetylation, phosphorylation, or any other manipulation or modification, such as conjugation with a labelling component.

The term "variant" as used herein includes polypeptides that may differ in amino acid sequence by one or more substitutions, additions, deletions, truncations which may be present in any combination. Among preferred variants are those that vary from a reference polypeptide by conservative amino acid substitutions. Such substitutions are those that substitute a given amino acid by another amino acid of like characteristics. The following non-limiting list of amino acids are considered conservative (similar) replacements: a) alanine, serine, and threonine; b) glutamic acid and asparatic acid; c) asparagine and glutamine d) arginine and lysine; e) isoleucine, leucine, methionine and valine and f) phenylalanine, tyrosine and tryptophan.

Amino acid substitutions can range from changing or modifying one or more amino acids to complete redesign of a region, such as the variable region. Amino acid substitutions are preferably conservative substitutions that do not deleteriously affect folding or functional properties of the peptide. Groups of functionally related amino acids within which conservative substitutions may be made are glycine/alanine; valine/isoleucine/leucine; asparagine/glutamine; asvariantic acid/glutamic acid; serine/threonine/methionine; lysine/arginine; and phenylalanine/tryosine/tryptophan. Polypeptides of this invention may be in glycosylated or unglycosylated form, may be modified post-translationally (e.g., acetylation, and phosphorylation) or may be modified synthetically (e.g., the attachment of a labeling group).

As used herein, the term "polypeptide" means, in general terms, a plurality of amino acid residues joined together by peptide bonds. It is used interchangeably and means the same as peptide, protein, oligopeptide, or oligomer. The term "polypeptide" is also intended to include fragments, analogues and derivatives of a polypeptide wherein the fragment, analogue or derivative retains essentially the same biological activity or function as a reference protein. The term "polypeptide" also includes peptidomimetics and structural analogues of the described sequences, and those modified either naturally (e.g. post-translational modification) or chemically, including, but not exclusively, phosphorylation, glycosylation, sulfonylatlon and/or hydroxylation.

A "variant thereof of an antigenic polypeptide according to the invention may thus include a fragment or subunit of the antigenic polypeptide wherein the fragment or subunit is sufficient to induce an antigenic response in a recipient. Thus the present invention encompasses an antigenic polypeptide comprising an amino acid sequence as represented in Figure 1 or a fragment thereof or a variant polypeptide wherein said variant is modified by addition, deletion or substitution of at least one amino acid residue of the amino acid sequence presented in Figure 1 and wherein said variant polypeptide is sufficient to induce an antigenic response in a recipient. As used herein "a fragment of a polypeptide comprising the amino acid sequence as shown in Figure 1" includes fragments that contain between 1 and 50 amino acids, for example between 1 and 30 amino acids such as between 10 and 30 amino acids. In one embodiment the variant is an antigenic polypeptide comprising the amino acid sequence as represented in Figure 2.

According to a second aspect of the invention there is provided a vector comprising a nucleic acid sequence encoding a polypeptide according to the first aspect of the invention. The vector of the second aspect of the invention may be a plasmid, cosmid, phage or virus based vector. The vector may include a transcription control sequence (promoter sequence) which mediates cell specific expression, for example, a cell specific, inducible or constitutive promoter sequence. The vector may be an expression vector adapted for prokaryotic or eukaryotic gene expression, for example, the vector may include one or more selectable markers and/or autonomous replication sequences which facilitate the maintenance of the vector in either a eukaryotic cell or prokaryotic host (Sambrook et al (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbour Laboratory, Cold Spring Harbour, NY and references therein; Marston, F (1987) DNA Cloning Techniques: A Practical Approach VoI III IRL Press, Oxford UK; DNA Cloning: F M Ausubel et al, Current Protocols in Molecular Biology, John Wiley & Sons, Inc. (1994). Vectors which are maintained autonomously are referred to as episomal vectors.

Promoter is an art-recognised term and may include enhancer elements which are cis acting nucleic acid sequences often found 5' to the transcription initiation site of a gene (enhancers can also be found 3' to a gene sequence or even located in intronic sequences and is therefore position independent). Enhancer activity is responsive to trans acting transcription factors (polypeptides e.g. phosphorylated polypeptides) which have been shown to bind specifically to enhancer elements. The binding/activity of transcription factors (please see Eukaryotic Transcription Factors, by David S Latchman, Academic Press Ltd, San Diego) is responsive to a number of environmental cues which include intermediary metabolites (eg glucose, lipids), environmental effectors (eg light, heat,).

Promoter elements also include so called TATA box and RNA polymerase initiation selection (RIS) sequences which function to select a site of transcription initiation. These sequences also bind polypeptides which function, inter alia, to facilitate transcription initiation selection by RNA polymerase.

The vector of the second aspect of the invention may include a transcription termination or polyadenylation sequences. This may also include an internal ribosome entry sites (IRES) or Shine-Dalgamo (bacterial ribosome binding) site. The vector may include a nucleic acid sequence that is arranged in a bicistronic or multi-cistronic expression cassette. According to a third aspect of the invention there is provided a method for the production of a recombinant antigenic polypeptide according to any previous aspect of the invention comprising:

(i) providing a cell transformed/transfected with a vector according to the second aspect of the invention; (ii) growing said cell in conditions suitable for the production of said polypeptides; and (iii) purifying said polypeptide from said cell, or its growth environment.

In a preferred aspect of the method of the third aspect, the vector encodes, and thus said recombinant polypeptide is provided with, an affinity tag and/or a secretion signal to facilitate purification of said polypeptide.

According to a fourth aspect of the invention there is provided a cell or cell-line transformed or transfected with the vector according to the second aspect of the invention.

In a preferred embodiment of the invention said cell is a prokaryotic celi, for example, a bacterium such as E. coli. Alternatively said cell is a eukaryotic cell, for example a yeast or other fungal cell, insect, amphibian, or mammalian cell, for example, COS, CHO cells, Bowes Melanoma and other suitable human cells, or plant cell.

According to a fifth aspect of the invention there is provided a vaccine comprising at least one antigenic polypeptide, or variant thereof, according to the first aspect of the invention. Preferably said vaccine further comprises an adjuvant/carrier.

The vaccine may comprise an antigenic polypeptide, or variant thereof, encoded by an isolated nucleic acid sequence selected from the group consisting of: i) a nucleic acid sequence as shown in Figure 1; ii) a nucleic acid sequence which hybridises to the sequence identified in (i) above; and iii) a nucleic acid sequence that is degenerate as a result of the genetic code to the nucleic acid sequence defined in (i) or (ii).

In one embodiment of the invention the vaccine comprises an antigenic polypeptide, or variant thereof, encoded by an isolated nucleic acid sequence as shown in Figure 2. The vaccine according to the fifth aspect may be a subunit vaccine in which the immunogenic part of the vaccine is a fragment or subunit of the antigenic polypeptide according to the first aspect of the invention.

An adjuvant is a substance or procedure that augments specific immune responses to antigens by modulating the activity of immune cells. Examples of adjuvants include, by example only, Freunds adjuvant, squalene, phosphate adjuvants and aluminium salts (e.g. aluminium hydroxide or aluminium phosphate). Others may include muramyl dipeptides, liposomes. A carrier is an immunogenic molecule which, when bound to a second molecule, augments immune responses to the latter. Some antigens are not intrinsically immunogenic yet may be capable of generating antibody responses when associated with a foreign protein molecule such as keyhole-limpet haemocyanin or tetanus toxoid. Such antigens contain B-cell epitopes but no T cell epitopes. The protein moiety of such a conjugate (the "carrier" protein) provides T-cell epitopes which stimulate helper T-cells that in turn stimulate antigen-specific B-cells to differentiate into plasma cells and produce antibody against the antigen. Helper T-cells can also stimulate other immune cells such as cytotoxic T-cells, and a carrier can fulfil an analogous role in generating cell-mediated immunity as well as antibodies.

In yet a further aspect of the invention there is provided a method to immunise an animal against a pathogenic microbe comprising administering to said animal at least one polypeptide, or variant thereof, according to the first aspect of the invention. Preferably, the polypeptide is in the form of a vaccine according to the fifth aspect of the invention.

In a preferred method of the invention the animal is human.

Preferably, the antigenic polypeptide of the first aspect, or the vaccine of the fifth aspect, of the invention can be delivered by direct injection either intravenously, intramuscularly, subcutaneously. Further still, the vaccine or antigenic polypeptide, may be taken orally. The polypeptide or vaccine may be administered in a pharmaceutically acceptable carrier, such as the various aqueous and lipid media, such as sterile saline, utilized for preparing injectables to be administered intramuscularly and subcutaneously. Conventional suspending and dispersing agents can be employed. Other means of administration, such as implants, for example a sustained low dose releasing bio- observable pellet, will be apparent to the skilled artisan. The vaccine may be against a bacterial species of the genus Neisseria for example Neisseria meningitidis (meningococcus) or Neisseria gonorrhoeae.

The vaccine may be against the bacterial species Neisseria meningitidis.

The vaccine may be against the bacterial species Neisseria gonorrhoeae.

The vaccine may be against the bacterial species Neisseria meningitidis (meningococcus) and Neisseria gonorrhoeae (gonococcus).

It will also be apparent that vaccines or antigenic polypeptides are effective at preventing or alleviating conditions in animals other than humans, for example and not by way of limitation, companion animals (e.g. domestic animals such as cats and dogs), livestock (e.g. cattle, sheep, pigs) and horses.

According to a further aspect of the invention there is provided an agent that binds to at least one antigenic polypeptide, or variant thereof, according to the invention. Preferably the agent is an antagonist. Preferably the agent inhibits the activity of said antigenic polypeptide. As used herein the term "inhibits" refers to a species which retards, blocks or prevents an interaction. Typically, inhibition does not result in 100% blockage but rather reduces the amount and/or speed of interaction.

Preferably the agent is an antibody or active binding fragment thereof. The antibody, or active binding fragment, may be a polyclonal antibody or a monoclonal antibody. Preferably the antibody, or active binding fragment, is a monoclonal antibody.

Antibodies or immunoglobulins (Ig) are a class of structurally related proteins consisting of two pairs of polypeptide chains, one pair of light (L) (low molecular weight) chain (K or λ), and one pair of heavy (H) chains (γ, α, μ, δ and ε), all four linked together by disulphide bonds. Both H and L chains have regions that contribute to the binding of antigen and that are highly variable from one Ig molecule to another. In addition, H and L chains contain regions that are non-variable or constant. The L chains consist of two domains. The carboxy-terminal domain is essentially identical among L chains of a given type and is referred to as the "constant" (C) region. The amino terminal domain varies from L chain to L chain and contributes to the binding site of the antibody. Because of its variability, it is referred to as the "variable" (V) region. The variable region contains complementarity-determining regions or CDR's which form an antigen binding pocket. The binding pockets comprise H and L variable regions which contribute to antigen recognition. It is possible to create single variable regions, so called single chain antibody variable region fragments (scFv's). If a hybridoma exists for a specific monoclonal antibody it is well within the knowledge of the skilled person to isolate scFv's from mRNA extracted from said hybridoma via RT PCR. Alternatively, phage display screening can be undertaken to identify clones expressing scFv's. Alternatively said fragments are "domain antibody fragments". Domain antibodies are the smallest binding part of an antibody (approximately 13 kDa). Examples of this technology is disclosed in US6, 248, 516, US6, 291 , 158, US6.127, 197 and EP0368684 which are all incorporated by reference in their entirety.

In a preferred embodiment of the invention said antibody fragment is a single chain antibody variable region fragment.

In a further preferred embodiment of the invention said antibody is a humanised or chimeric antibody.

A chimeric antibody is produced by recombinant methods to contain the variable region of an antibody with an invariant or constant region of a human antibody. A humanised antibody is produced by recombinant methods to combine the complementarity determining regions (CDRs) of an antibody with both the constant (C) regions and the framework regions from the variable (V) regions of a human antibody. Chimeric antibodies are recombinant antibodies in which all of the V-regions of a mouse or rat antibody are combined with human antibody C-regions. Humanised antibodies are recombinant hybrid antibodies which fuse the complimentarity-determining regions from a rodent antibody V-region with the framework regions from the human antibody V- regions. The C-regions from the human antibody are also used. The complimentarity- determining regions (CDRs) are the regions within the N-terminal domain of both the heavy and light chain of the antibody to where the majority of the variation of the V- region is restricted. These regions form loops at the surface of the antibody molecule. These loops provide the binding surface between the antibody and antigen.

In a further preferred aspect of the invention said antibody is a chimeric antibody produced by recombinant methods to contain the variable region of said antibody with an invariant or constant region of a human antibody. In a further preferred aspect of the invention, said antibody is humanised by recombinant methods to combine the complimentarity-determining regions of said antibody with both the constant (C) regions and the framework regions from the variable (V) regions of a human antibody.

Preferably said antibody is provided with a marker including a conventional label or tag, for example a radioactive and/or fluorescent and/or epitope label or tag.

Preferably said humanised monoclonal antibody to said polypeptide is produced as a fusion polypeptide in an expression vector suitably adapted for transfection or transformation of prokaryotic or eukaryotic cells.

Antibodies from non-human animals provoke an immune response to the foreign antibody and its removal from the circulation. Both chimeric and humanised antibodies have reduced antigenicity when injected to a human subject because there is a reduced amount of rodent (i.e. foreign) antibody within the recombinant hybrid antibody, while the human antibody regions do not illicit an immune response. This results in a weaker immune response and a decrease in the clearance of the antibody. This is clearly desirable when using therapeutic antibodies in the treatment of human diseases. Humanised antibodies are designed to have less "foreign" antibody regions and are therefore thought to be less immunogenic than chimeric antibodies.

In another aspect of the invention there is provided a vector comprising a nucleic acid sequence encoding the humanised or chimeric antibodies according to the invention.

In a yet further aspect of the invention, there is provided a cell or cell line which comprises the vector encoding the humanised or chimeric antibody according to the invention. The cell or cell line may be transformed or transfected with the vector encoding the humanised or chimeric antibody according to the invention. -

In a yet further aspect of the invention there is provided a hybridoma cell line which produces a monoclonal antibody as hereinbefore described.

In a further aspect of the invention there is provided a method of producing monoclonal antibodies according to the invention using hybridoma cell lines according to the invention.

In a yet further aspect of the invention there is provided a method for the production of the humanised or chimeric antibody according to the invention comprising:

(i) providing a cell transformed or transfected with a vector which comprises a nucleic acid molecule encoding the humanised or chimeric antibody according to the invention; (ii) growing said cell in conditions suitable for the production of said antibody; and purifying said antibody from said cell, or its growth environment.

In a further aspect of the invention there is provided a method for preparing a hybridoma cell-line according to the invention comprising the steps of: i) immunising an immunocompetent mammal with an immunogen comprising at least one polypeptide having an amino acid sequence as represented in Figure 1 , or a fragment thereof; ii) fusing lymphocytes of the immunised immunocompetent mammal with myeloma cells to form hybridoma ceJIs; iii) screening monoclonal antibodies produced by the hybridoma cells of step

(ii) for binding activity to the amino acid sequences of (i); iv) culturing the hybridoma cells to proliferate and/or to secrete said monoclonal antibody; and v) recovering the monoclonal antibody from the culture supernatant.

In one embodiment, the polypeptide in method step (i) has an amino acid sequence as represented in Figure 2, or a fragment thereof.

The immunocompetent mammal may be a mouse, rat or rabbit.

The production of monoclonal antibodies using hybridoma cells is well-known in the art. The methods used to produce monoclonal antibodies are disclosed by Kohler and Milstein in Nature 256, 495-497 (1975) and also by Donillard and Hoffman, "Basic Facts about Hybridomas" in Compendium of Immunology V.ll ed. by Schwartz, 1981 , which are incorporated by reference. A further aspect of the invention provides a pharmaceutical composition comprising an effective amount of at least one antigenic polypeptide, vaccine or agent according to the invention. When administered, the pharmaceutical compositions and formulations of the present invention are administered in pharmaceutically acceptable preparations. Such preparations may routinely contain pharmaceutically acceptable concentrations of salt, buffering agents, preservatives, compatible carriers, supplementary immune potentiating agents such as adjuvants and cytokines and optionally other therapeutic agents. The compositions and formulations of the invention can be administered by any conventional route, including injection or by gradual infusion over time. The administration may, for example, be oral, intravenous, intraperitoneal, intramuscular, intracavity, subcutaneous, or transdermal. When antibodies are used therapeutically, one particular route of administration is by pulmonary aerosol. Techniques for preparing aerosol delivery systems containing antibodies are well known to those of skill in the art. Generally, such systems should utilize components which will not significantly impair the biological properties of the antibodies, such as the paratope binding capacity (see, for example, Sciarra and Cutie, "Aerosols," in Remington's Pharmaceutical Sciences, 18th edition, 1990, pp 1694-1712; incorporated by reference). Those of skill in the art can readily determine the various parameters and conditions for producing antibody aerosols without resort to undue experimentation.

The compositions and formulations of the invention are typically administered in effective amounts. An "effective amount" is that amount of a composition that alone, or together with further doses, produces the desired response.

When administered, the pharmaceutical preparations and formulations of the invention are applied in pharmaceutically-acceptable amounts and in pharmaceutically-acceptable compositions. The term "pharmaceutically acceptable" means a non-toxic material that does not interfere with the effectiveness of the biological activity of the active ingredients. Such preparations may routinely contain salts, buffering agents, preservatives, compatible carriers, and optionally other therapeutic agents. When used in medicine, the salts should be pharmaceutically acceptable, but non-pharmaceutically acceptable salts may conveniently be used to prepare pharmaceutically-acceptable salts thereof and are not excluded from the scope of the invention. Such pharmacologically and pharmaceutically-acceptable salts include, but are not limited to, those prepared from the following acids: hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, maleic, acetic, salicylic, citric, formic, malonic, succinic, and the like. Also, pharmaceutically- acceptable salts can be prepared as alkaline metal or alkaline earth salts, such as sodium, potassium or calcium salts.

Pharmaceutical compositions and formulations may be combined if desired, with a pharmaceutically-acceptable carrier. The term "pharmaceutically-acceptable carrier" as used herein means one or more compatible solid or liquid fillers, diluents or encapsulating substances which are suitable for administration into a human. The term "carrier" denotes an organic or inorganic ingredient, natural or synthetic, with which the active ingredient is combined to facilitate the application. The components of the pharmaceutical compositions also are capable of being co-mingled with the molecules of the present invention, and with each other, in a manner such that there is no interaction which would substantially impair the desired pharmaceutical efficacy.

In a further aspect of the invention there is provided the use of an antigenic polypeptide according to the first aspect of the invention in the manufacture of a medicament for the treatment or prophylaxis of a bacterial infection or a bacteria related disorder.

Preferably, the bacterial infection is caused by a bacterial pathogen derived from a bacterial species for example a gram negative bacterium. The bacterium may be of the genus Neisseria for example Neisseria meningitidis (meningococcus) or Neisseria gonorrhoeae (gonόcoccus).

In a preferred embodiment the bacterial infection is a meningococcal infection.

The bacteria-related disorder may be a meningococcal disease including, for example, meningitis (meningococcal meningitis), septicaemia and septic shock.

The bacteria-related disorder may be gonorrhoea.

Preferably the bacteria-related disorder is meningitis.

A further aspect of the invention there is provided the use of antibodies according to the invention in the manufacture of a medicament for the treatment of a bacterial infection.

In a further aspect of the invention there is provided a method of treating a patient comprising administering to the patient an antigenic polypeptide according to the first aspect of the invention, or a vaccine according to the fifth aspect of the invention, or an antibody according to the invention. Preferably the method is for the treatment of a meningococcal infection for example meningitis.

The present invention also provides the use of an antigenic polypeptide, or variant thereof, in the identification of agents which modulate the activity of said polypeptide wherein the polypeptide, or variant thereof, is encoded by an isolated nucleic acid sequence selected from the group consisting of: i) a nucleic acid sequence as shown in Figure 1 ; ii) a nucleic acid sequence which hybridises to the sequence identified in (i) above; and iii) a nucleic acid sequence that is degenerate as a result of the genetic code to the nucleic acid sequence defined in (i) or (ii).

In a preferred use according to the invention the polypeptide, or variant thereof, is encoded by an isolated nucleic acid sequence as shown in Figure 2.

According to a further aspect of the invention there is provided a kit comprising an agent specifically reactive with a polypeptide encoded by a nucleic acid sequence as represented in Figure 1 , or a fragment or variant thereof as defined herein, or an agent specifically reactive with a polypeptide comprising an amino acid sequence as represented in any of Figure 1 , or a fragment or variant thereof as defined herein.

In a preferred embodiment of the invention said kit further comprises an oligonucleotide or antibody specifically reactive with said nucleic acid molecule or said polypeptide.

Preferably said kit comprises a thermostable DNA polymerase and components required for conducting the amplification of nucleic acid. Preferably said kit includes a set of instructions for conducting said polymerase chain reaction and control nucleic acid.

In an alternative preferred embodiment of the invention said kit comprises an antibody specifically reactive with a polypeptide comprising an amino acid sequence as represented in Figure 1 , or a fragment or variant thereof as defined herein. According to a further aspect of the invention there is provided a method to screen for an agent that modulates the activity of a polypeptide encoded by a nucleic acid molecule selected from the group consisting of: i) a nucleic acid sequence as shown in Figure 1 ; ii) a nucleic acid sequence which hybridises to the sequence identified in (i) above; and iii) a nucleic acid sequence that is degenerate as a result of the genetic code to the nucleic acid sequence defined in (i) or (ii); wherein the method comprises a) forming a preparation comprising a polypeptide, or sequence variant thereof, and at least one agent to be tested; b) determining the activity of said agent with respect to the activity of said polypeptide.

The amino acid sequence represented in Figure 1 can be used for the structure-based design of molecules which modulate (e.g. inhibit) the activity of the polypeptide. Such structure based design is also known as "rational drug design". The proteins can be three-dimensional^jy analysed by, for example, X-ray crystallography, nuclear magnetic resonance or homology modelling, all of which are well-known methods. The use of structural information in molecular modelling software systems is also encompassed by the invention. Such computer-assisted modelling and drug design may utilise information such as chemical conformational analysis, electrostatic potential of the molecules, protein folding etc. One particular method of the invention may comprise analysing the three-dimensional structure of the protein of Figure 1 for likely binding sites of targets, synthesising a new molecule that incorporates a predictive reactive site, and assaying the new molecule as described above.

In a method of the invention said agent may be an antagonist. Agents identified by the screening method of the invention may include, antibodies, small organic molecules, (for example peptides, cyclic peptides), and dominant negative variants of the polypeptides herein disclosed.

As mentioned above, the invention also provides, in certain embodiments, "dominant negative" polypeptides derived from the polypeptides herein disclosed. A dominant negative polypeptide is an inactive variant of a protein, which, by interacting with the cellular machinery, displaces an active protein from its interaction with the cellular machinery or competes with the active protein, thereby reducing the effect of the active protein. For example, a dominant negative receptor which binds a ligand but does not transmit a signal in response to binding of the ligand can reduce the biological effect of expression of the ligand. Likewise, a dominant negative catalytically-inactive kinase which interacts normally with target proteins but does not phosphorylate the target proteins can reduce phosphorylation of the target proteins in response to a cellular signal. Similarly, a dominant negative transcription factor which binds to another transcription factor or to a promoter site in the control region of a gene but does not increase gene transcription can reduce the effect of a normal transcription factor by occupying promoter binding sites without increasing transcription.

It will be apparent to one skilled in the art that modification to the amino acid sequence of polypeptides or agents according to the present invention could enhance the binding and/or stability of the peptide with respect to its target sequence. Modifications include, by example and not by way of limitation, acetylation and amidation. Alternatively or preferably, said modification includes the use of modified amino acids in the production of recombinant or synthetic forms of peptides. It will be apparent to one skilled in the art that modified amino acids include, for example, 4-hydroxyproϊme, 5-hydroxylysine, N⁶- acetyllysine, N⁶-methyllysine, N⁶,N⁶-dimethyllysine, N⁶,N⁶,N⁶-trimethyllysine, cyclohexyalanine, D-amino acids, ornithine. Other modifications include amino acids with a C_2, C₃ or C₄ alkyl R group optionally substituted by 1 , 2 or 3 substituents selected from halo ( eg F, Br, I), hydroxy or Ci-C₄ alkoxy. It will also be apparent to one skilled in the art that polypeptides could be modified by cyclisation. Cyclisation is known in the art, (see Scott et al Chem Biol (2001), 8:801-815; Gellerman et al J. Peptide Res (2001), 57: 277-291 ; Dutta et al J. Peptide Res (2000), 8: 398-412; Ngoka and Gross J Amer Soc Mass Spec (1999), 10:360-363.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

An embodiment of the invention will now be described by way of example only and with reference to the following materials, methods and figures:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows in (a) the nucleic acid sequence of the fba gene from serogroup B strain of Neisseria meningitidis MC58; and (b) the corresponding predicted protein from serogroup B strain of Neisseria meningitidis MC58;

Figure 2 shows in (a) the nucleic acid sequence of the fba gene in Neisseria gonorrhoeae strain FA1090; and (b) the corresponding predicted protein in Neisseria gonorrhoeae strain FA 1090;

Figure 3 is a homology tree showing amino acid conservation in FBA enzymes from meningococcal strains Z2491 (NMA0587), FAM 18, and MC58 (NMB 1869), and FBA from N. gonorrhoeae (gonococcus).

Figure 4 is a Western blot demonstrating the expression and purification of recombinant FBA;

Figure 5 shows the localisation of FBA to the meningococcal outer membrane.

A. Wild-type Neisseria meningitidis strain MC58; B. Isogenic FBA mutant strain. Lane 1 , molecular weight markers; lane 2, periplasmic protein-enriched fraction; lane 3, cytoplasmic protein-enriched fraction; lane 4, cytoplasmic membrane protein-enriched fraction; lane 5, outer membrane protein-enriched fraction; lane 6, secreted protein fraction.

Figure 6 shows a graph of the results of a standard coupled assay showing the enzymic activity of fructose 1 ,6-bisphosphate aldolase. Figure 7 is a histogram showing the association of wild-type meningococci, the FBA (cbbA) null mutant, and pilQ/porA double mutant (control) to human meningothelial cells, demonstrating that FBA is required for efficient adhesion to host cells.

Figure 8 shows a diagrammatic representation of a transgenic mouse model of meningococcal bacteraemia.

EXAMPLES

Fructose bisphosphate aldolase (FBA) in N. meningitidis

FBA is encoded by a 1,065-bp gene, and the predicted 354 amino acid sequence (Fig. 1) shows a high degree of conservation in N. meningitidis (Figure 3). Furthermore, the amino acid sequence of FBA in N. gonorrhoeae (Figure 2) is 99% identical to that in N. meningitidis (Figure 3). Despite being predicted to be part of a non-functional metabolic pathway, the gene is intact and expressed. This suggests that FBA is maintained in the genome for alternative functions. Furthermore, FBA is not predicted to be a phase- variable protein. In the genome sequence of N. meningitidis serogroup B strain MC58, FBA is designated NMB1869. Only one copy of the FBA gene is present in the genome, and homology searches for additional type Il FBA enzymes failed to find any other homologues. Additional searches were performed to determine whether a type I FBA enzyme, similar to that in E. coli or members of the Archeal kingdom, was present in the meningococcal genome but none were found.

The FBA gene from N. meningitidis serogroup B strain MC58 was cloned and over- expressed with a N-terminal His-tag in E. coli, and the ca. 38 kDa recombinant protein was affinity-purified (Figure 4). The fba gene from N. meningitidis strain MC58 was amplified using PCR, and ligated into the pEXP-NT TOPO vector (Invitrogen), which expresses recombinant protein with an N-terminal six-histidine tag under the control of the phage T7 promoter. The protein purification was carried out under denaturing condition using Ni-NTA spin columns (Qiagen) and buffers B, C and E, according to the manufacturer's instructions. All buffers were prepared with same chemical composition (100 mM NaH₂PO₄, 10 mM Tris-CI, and 8 M Urea) but with varying pH. Polyclonal monospecific rabbit serum (anti-FBA serum) was raised against the purified protein for use in localisation experiments. Rabbit monospecific polyclonal antibodies to FBA were raised against the denatured purified protein in a New Zealand White female rabbit. Pre- immune serum was obtained before immunization. The animal was immunized subcutaneously four times at 2-week intervals with c. 20 μg of protein emulsified in Freund's complete (first immunization only) or incomplete adjuvant. After three injections, the animal was test bled, boosted once more and sacrificed 10 days later.

A viable fba knockout (null-mutant) was generated using a mutational construct generated by inverse PCR, and natural transformation and allelic exchange. Growth curves (data not shown) suggest that the fba null-mutant is able to grow at a similar rate to the wild-type strain. This confirms that the type Il FBA enzyme in N. meningitidis is not an essential enzyme, presumably due to the glycolytic pathway being non-functional.

Localisation experiments in our laboratory suggest that FBA is present in the outer- membrane protein fraction (Figure 5). N. meningitidis cells were grown overnight in Mueller Hinton Broth and harvested by centrifugation. The supernatant was filtered using a 0.2 μm Minisart filter. Supernatant (secreted) proteins were concentrated by ultrafiltration using a Vivaspin-2 protein concentrator (30,000-molecular-weight cut off; Vivascience) according to the manufacturer's instructions. The pellet was resuspended in deionised water and the cells were lysed by sonication. Unlysed cells were removed by centrifugation (250 x g for 2 min). The supernatant was collected and centrifuged (11,000 x g for 30 min). The supernatant (cytosolic protein-enriched fraction) was collected. The pellet was resuspended in 25 μl of phosphate buffered saline by vigorous pipetting, 25 μl of 4% Triton X-100 in phosphate buffered saline was added and the mixture was incubated at 37°C for 30 min. Triton-insoluble proteins (outer-membrane- protein-enriched fraction) were pelleted by centrifugation (11,000 x g for 30 min). The supernatant containing Triton-soluble proteins (cytoplasmic-membrane-protein-enriched) was collected. All samples were stored at -20⁰C until required. The fractions were analysed for the presence of FBA using the anti-FBA serum.

Kinetic analysis of the Fructose bisphosphate aldolase (FBA) enzymic activity

Fructose bisphosphate aldolase (FBA) enzymic activity assay methodology A coupled enzymic assay was used to determine the aldolase activity of natively-purified FBA. The assay was performed in 1 ml of 50 mM Tris/HCI supplemented with 0.1 M potassium acetate buffer (pH 8.0) containing 0.1-5 mM fructose 1 , 6-bisphosphate, 0.2 mM NADH and 2 μl 10 mg/ml mixture of glycerol-phosphate dehydrogenase/triosephosphate isomerase at 30 ⁰C. The reagents were added in the order: buffer; fructose 1 , 6-bisphosphate; NADH; coupling enzymes. The reaction was started by the addition of natively-purified FBA enzyme. A decrease in absorbance at 340 nm was recorded as the measure of enzyme activity on an Uvikon 930 spectrophotometer. Activities were calculated using the molar extinction coefficient for NADH as 6220 M^"1cm^'1. One unit of aldolase activity was defined as the amount of enzyme which catalyses oxidation of 2 μmol NADH/min in the assay system. Kinetic parameters were estimated using the Origin Pro 7.5 program.

NADH+ H NAD+

Results

A standard coupled assay to measure the enzymic activity of fructose 1 ,6-bisphosphate aldolase was used. Cleavage of FBP is coupled to α-glycerophosphate dehydrogenase and NAD oxidation. Natively purified FBA was shown to exhibit aldolase activity (Fig. 6).

The FBA mutant exhibits a defect in association to human brain meningothelial cells (HBMECs)

Association assay

Human meningothelial or larynx carcinoma (HEp-2) cells were grown to confluence in DMEM supplemented with 10% heat-inactivated foetal calf serum (FCS; Invitrogen) and 2% antibiotic anti-mycotic solution (Invitrogen) in 24-well tissue culture plates (Costar) at 37°C in an atmosphere of 5% CO₂. Prior to all experiments, mono-layers were transferred to DMEM supplemented with 2% FCS to remove the antibiotics. Meningococci were cultured in MHB for 2 h and monolayers were infected with 1 x 10⁷ CFU of meningococci and were left to associate for 2 h in 5% CO₂ at 37°C. To assess total cell association, monolayers were washed four times with 1 ml 1 *PBS per well. All assays were repeated at least three times. Statistical significance was measured using the Student Mest.

Results Viable counts of bacteria associated with homogenized infected monolayers were used to compare the capacity of the wild type and FBA (cbbA) mutant strain to associate with either HEp-2 (human larynx carcinoma) or meningothelial (primary human cell lines derived from benign meningothelial tumours) cells. A pilQ/porA double mutant strain was used as a control. These experiments showed that FBA-deficient meningococci had a significantly reduced capacity to adhere with meningothelial cells (Fig. 7). Similar results were observed using monolayers of HEp-2 cells. Experiments were repeated on more than three separate occasions, with both cell lines, with consistent results. To confirm that this effect was not due to a reduced growth, the growth rate of both strains was compared by measuring the optical density at 600 nm (OD₆oo) and determining the viable counts of broth cultures sampled during exponential growth in triplicate on three separate occasions. No significant difference between strains was observed (data not shown).

FBA is required for meningococcal bacteraemia in transgenic mice expressing human transferrin

Methodology

Transgenic mice expressing human transferring [Zarantonelfi et af., Infect lmmun 75: 5609-5614, 2007] (BALB/c congenic mice) were used to assess bacteraemia levels provoked by mutants in the meningococcal fba gene that were constructed in different meningococcal genetic lineages. For each mutant, the levels of bacteraemia were compared to the corresponding parent strain. Bacteria were passaged on GCB medium supplemented with Kellogg supplements [Kellogg et al., J Bacteriol 85: 1274-1279, 1963] and kanamycin at 100 mg/ml.

Mice were kept in a biosafety containment facility, in cages with sterile litter, water and food, according to institutional guidelines. The experimental design was approved by the lnstitut Pasteur Review Board. Six-week-old BALB/c females were infected by intraperitoneal challenge with standardized inocula at 10⁷ colony forming units (CFU). Bacterial counts were determined in the blood 2, 6, 24 and 48 h after meningococcal challenge, by plating serial dilutions of blood samples on GCB medium, and are expressed as log₁₀ CFU/ml of blood. Results were expressed as means of 5 mice ±SD per time point and per strain.

Results

Regardless of the genetic background of the meningococcal strain, FBA mutant strains were unable to efficiently establish bacteraemia in the mouse model. At all time points, the level of bacteraemia established by the FBA mutant strains was significantly lower than that of the respective wild-type strains (Fig. 8).

ELISA assay for anti-FBA IgM response during natural infection

Paired sera were obtained from eight patients (age range 2-8 years) with confirmed meningococcal infection. Paired sera consisted of an acute serum obtained on admission to hospital and a convalescent serum obtained between 9 and 40 days later. As a control, we used paired sera from a 10-year-old child vaccinated using anti- meningococcal A&C plain capsular polysaccharide vaccine (serum being obtained before vaccination and 16 days post-vaccination). Sera were obtained routinely to confirm diagnosis or to assess immune response after vaccination. Patients, or their legal representatives, expressed written agreement for the use of the sera for additional research (excluding genomic research).

An ELISA plate was coated with purified FBA (10 μg/ml; 100 μl per well) and sera were used at 1:100 final dilution. IgM response was detected using a HPRO- conjugated goat anti-human IgM (Invitrogen) at 1 :5000 final dilution. Absorbance was measured at 492 nm. Each serum was tested in triplicate and results were expressed as mean ±SD.

Results

A FBA-specific IgM response was detected in the convalescent serum sample in 6 of the 8 patients with confirmed meningococcal infection. For these patients, the FBA-specific IgM titre in the convalescent serum sample was 1.6 - 2.5 higher than in the acute serum sample (Table 1). This suggests that FBA is immunogenic in humans following natural meningococcal infection.

Table 1. ELISA assay for anti-FBA IgM response during natural infection

to

Claims

1. An antigenic polypeptide, or variant thereof, encoded by an isolated nucleic acid sequence selected from the group consisting of: i) a nucleic acid sequence as shown in Figure 1 ; ii) a nucleic acid sequence which hybridises to the sequence identified in (i) above; and iii) a nucleic acid sequence that is degenerate as a result of the genetic code to the nucleic acid sequence defined in (i) or (ii) for use as a medicament.

2. An antigenic polypeptide, or variant thereof, as claimed in claim 1 wherein the polypeptide is encoded by an isolated nucleic acid sequence as shown in Figure 1.

3. An antigenic polypeptide, or variant thereof, as claimed in claim 1 wherein the polypeptide is encoded by an isolated nucleic acid sequence as shown in Figure 2.

4. An antigenic polypeptide as claimed in any one preceding claim wherein the medicament is a vaccine.

5. An antigenic polypeptide as claimed in any preceding claim wherein the nucleic acid encoding the antigenic polypeptide anneals under stringent hybridisation conditions to the nucleic acid sequence shown in Figure 1 or to its complementary strand.

6. An antigenic polypeptide as claimed in claim 1 wherein the antigenic polypeptide comprises the amino acid sequence shown in Figure 1 or a variant sequence thereof.

7. An antigenic polypeptide as claimed in claim 6 wherein the antigenic polypeptide comprises the amino acid sequence shown in Figure 2.

8. A vector comprising a nucleic acid sequence encoding an antigenic polypeptide as claimed in any one of claims 1 to 7.

9. A method for the production of a recombinant antigenic polypeptide as claimed in any one of claims 1 to 7 comprising: (i) providing a cell transformed/transfected with a vector according to claim 8;

(ii) growing said cell in conditions suitable for the production of said polypeptides; and (iii) purifying said polypeptide from said cell, or its growth environment.

10. A cell or cell-line transformed or transfected with a vector according to claim 8.

11. A vaccine comprising at least one antigenic polypeptide, or variant thereof, as claimed in any one of claims 1 to 7.

12. A vaccine as claimed in claim 11 wherein the vaccine further comprises a carrier and/or adjuvant.

13. A vaccine as claimed in claim 11 or 12 wherein the vaccine is a subunit vaccine in which the immunogenic part of the vaccine is a fragment or subunit of the antigenic polypeptide according to any one of claims 1 to 7.

14. A method to immunise an animal against a pathogenic microbe comprising administering to said animal at least one antigenic polypeptide, or part thereof, according to any one of claims 1 to 7.

15. A method as claimed in claim 14 wherein the polypeptide is in the form of a vaccine according to any one of claims 11 to 13.

16. A pharmaceutical composition comprising an effective amount of at least one of the antigenic polypeptides as claimed in any one of claims 1 to 7, or a vaccine as claimed in any one of claims 11 to 13, in combination with a pharmaceutically acceptable carrier or diluent.

17. An antibody, or active binding fragment thereof, which binds at least one antigenic polypeptide, or variant thereof, according to any one of claims 1 to 7.

18. An antibody as claimed in claim 17 wherein the antibody is a monoclonal antibody.

19. A hybridoma cell line which produces a monoclonal antibody as claimed in claim

20. An antibody as claimed in claim 17 or 18 wherein the antibody is a chimeric antibody.

21. An antibody as claimed in claim 17 or 18 wherein the antibody is a humanised antibody comprising the complimentarity-determining regions of said antibody with both the constant (C) regions and the framework regions from the variable (V) regions of a human antibody.

22. A vector comprising a nucleic acid sequence encoding a chimeric antibody according to claim 20 or a humanised antibody according to claim 21.

23. A cell or cell line transformed or transfected with the vector of claim 22.

24. A method for the production of a humanised or chimeric antibody comprising: i) providing a cell transformed or transfected with a vector according to claim 22; Ji) growing said cell in conditions suitable for the production of said antibody; and purifying said antibody from said cell, or its growth environment.

25. A method for preparing a hybridoma cell-line comprising the steps of: i) immunising an immunocompetent mammal with an immunogen comprising at least one polypeptide having an amino acid sequence as represented in Figure 1 , or a fragment thereof; ii) fusing lymphocytes of the immunised immunocompetent mammal with myeloma cells to form hybridoma cells; iii) screening monoclonal antibodies produced by the hybridoma cells of step

26. Use of an antigenic polypeptide as claimed in any one of claims 1 to 7 in the manufacture of a medicament for the treatment or prophylaxis of a bacterial infection or a bacteria-related disorder.

27. Use as claimed in claim 26 wherein the bacterial infection is caused by a bacterial pathogen belonging to a bacterial species of the genus Neisseria.

28. Use as claimed in claim 27 wherein the bacterial infection is caused by Neisseria meningitidis (meningococcus) or Neisseria gonorrhoeae (gonococcus).

29. Use as claimed in claim 28 wherein the bacterial infection is caused by Neisseria meningitidis (meningococcus).

30. Use as claimed in any one of claims 26 to 29 wherein the bacteria related disorder is a meningococcal-associated disorder.

31. Use as claimed in claim 30 wherein the meningococcal-associated disorder is meningitis (meningococcal meningitis) or septicaemia.

32. Use as claimed in any one of claims 26 to 28 wherein the bacterial infection is caused by Neisseria gonorrhoeae (gonococcus).

33. Use as claimed in claim 32 wherein the bacterial infection or bacteria-related disorder is gonorrhoea.

34. Use of an antibody as claimed in claim 17 or 18 in the manufacture of a medicament for the treatment of a bacterial infection.

35. A method of treating a bacterial infection or bacteria-related disorder in a patient comprising administering to the patient an antigenic polypeptide as claimed in any one of claims 1 to 7, or a vaccine as claimed in any one of claims 11 to 13, or an antibody as claimed in claim 17 or 18.