Acinetobacter baumannii polypeptides

Abstract

The invention relates to Acinetobacter baumannii immunogenic polypeptides or immunogenic fragments thereof and antibodies capable of binding said polypeptides or fragments. The invention further relates to compositions comprising one or more immunogenic polypeptides or immunogenic fragments thereof, compositions comprising one or more antibodies capable of binding said polypeptides or fragments, and methods of treating or preventing A. baumannii infection.

Description

[0001] POLYPEPTIDES

[0002] FIELD OF THE INVENTION

[0003] The invention relates to Acinetobacter baumannii immunogenic polypeptides or immunogenic fragments thereof and antibodies capable of binding said polypeptides or fragments. The invention further relates to compositions comprising one or more immunogenic polypeptides or immunogenic fragments thereof, compositions comprising one or more antibodies capable of binding said polypeptides or fragments, and methods of treating or preventing A. baumannii infection.

[0004] BACKGROUND TO THE INVENTION

[0005] The World Health Organisation (WHO) has identified antimicrobial resistance (AMR) as a considerable threat to human health, responsible for an estimated 4.95 million deaths worldwide in 2019. A priority pathogen for the development of new antimicrobials is the Gramnegative bacteria Acinetobacter baumannii (A. baumannii), which causes a wide range of infections including pneumonia, septicaemia, urinary tract, and skin / soft tissue infections. Since the 1970s incidence of A. baumannii infections has increased rapidly, and this pathogen is now estimated to cause over 300,000 deaths / year globally, with reported mortality rates of 30 to 70%. A. baumannii infections are especially problematic in Asia, causing 25,000 deaths / year in Thailand alone. More than 80% of strains are multidrug-resistant (MDR), with resistance rates to colistin, the antibiotic of last resort, of 11 .2%.

[0006] A potential approach for treatment of MDR A. baumannii infection is monoclonal antibody (mAb) therapy targeting specific antigens to promote immune clearance of the pathogen. Antibody therapies have recently been developed for treatment of Bacillus anthracis (raxibacumab, obiltoxaximab) and Clostridium difficile (bezlotoxumab). The extensive range of monoclonal therapies now in routine use for oncological and autoimmune conditions means there is considerable manufacturing expertise to assist the rapid development of an effective clinical product targeting A. baumannii. Furthermore, resistance to an antibody therapy is much less likely to develop than to novel antibiotics.

[0007] Despite the potential advantages of an antibody therapy, there are no monoclonal antibody candidates in advanced development for MDR A. baumannii infections. This is partially due to the significant difficulties in identifying suitable target antigens for an antibody therapy, a problem that has also hindered development of an effective vaccine.

[0008] The extracellular polysaccharide capsule is surface exposed, present in high quantities and is an effective antigen target in mouse models of A. baumannii infection (Russo, et al. 2013, Infect Immun 81 , 915-22) and for vaccines for other bacterial pathogens. However, there is considerable genetic variation between infecting A. baumannii strains, resulting in over 100 capsular serotypes (termed KL types), many of which cause human disease. For example, over 30 KL types were present in 191 Thai A. baumannii clinical isolates, with the most common KL type found in only 16% of strains. This level of KL variation precludes using capsular antigen as a target for an antibody therapy as each KL type would need a separate antibody.

[0009] An alternative target is subcapsular protein antigens that are conserved amongst infecting A. baumannii strains. However, A. baumannii has an extensive pangenome and a high proportion of surface proteins are either not present in many A. baumannii strains or show substantial allelic variation between strains. Furthermore, the capsule partially inhibits access of the immune response to subcapsular antigens. Subcapsular protein antigen candidates identified as targets for novel antibody therapies or active vaccines for MDR A. baumannii include outer membrane proteins OmpA (Yeganeh et al. 2021 , J Immunol Methods 499, 113169), BamA (Vieira de Araujo et al. 2021 , Microbes Infect23, 104801), Omp22 (Huang etal. 2016, Sci Rep 6), Omp34 (Naghipour Erami et al. 2021 , Microb Pathog 161 , 105291), and iron-regulated outer membrane proteins (Goel & Kapil, 2001 , BMC Microbiol 1 , 16), and the outer membrane nuclease NucAB (Garg et al., 2016, Int J Med Microbiol 306, 1-9).

[0010] However, there remains an urgent and unmet need for effective therapeutics for the prevention and / or treatment of A. baumannii infections, in particular by multiple-drug resistant strains.

[0011] SUMMARY OF THE INVENTION

[0012] The present inventors have developed a novel approach to rapidly identify multiple protein antigen therapeutic targets for AMR bacterial pathogens that could be targets for monoclonal antibody therapies. The inventors have identified Acinetobacter baumannii polypeptides that are surprisingly immunogenic. Furthermore, antibodies against said polypeptides recognised multiple clinical A. baumannii strains, were protective in an in vivo animal model, and / or improved antibiotic efficacy even against resistant A. baumannii strains. Thus, the present invention relates to the identification of novel antigens and antibodies for inducing effective protection against A. baumannii challenge and / or treatment of A. baumannii infection, for example by passive and / or active immunisation.

[0013] In one aspect, the invention provides an Acinetobacter baumannii immunogenic polypeptide comprising SEQ ID NO: 8, SEQ ID NO: 6, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 9, SEQ ID NO: 32 or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof. In some embodiments, the invention provides an A baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7,

[0014] SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID

[0015] NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20,

[0016] SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID

[0017] NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0018] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, or SEQ ID NO: 33 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0019] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , or SEQ ID NO: 33or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0020] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 33 ora sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0021] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, or SEQ ID NO: 33 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0022] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0023] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0024] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 8, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0025] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof. In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0026] The invention further provides a polynucleotide encoding one or more A. baumannii immunogenic polypeptides according to the invention.

[0027] The invention provides a vector comprising one or more polynucleotides according to the invention.

[0028] The invention provides an inhibitor which is capable of binding to an A. baumannii immunogenic polypeptide according to the invention.

[0029] In some embodiments, the inhibitor is an antibody.

[0030] The invention provides an immunogenic composition comprising one or more A. baumannii immunogenic polypeptides according to the invention.

[0031] The invention provides an immunogenic composition comprising one or more polynucleotides or one or more vectors according to the invention.

[0032] The invention provides a composition comprising one or more inhibitors according to the invention.

[0033] In some embodiments, the composition further comprises a pharmaceutically acceptable carrier, diluent or excipient. In some embodiments, the composition is a pharmaceutical composition.

[0034] The invention provides a vaccine comprising one or more A. baumannii immunogenic polypeptides according to the invention.

[0035] The invention provides a vaccine comprising a polynucleotide or a vector according to the invention.

[0036] The invention provides a method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an A. baumannii immunogenic polypeptide, a polynucleotide, a vector, an immunogenic composition, a vaccine, an inhibitor or a composition according to the invention.

[0037] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an A. baumannii immunogenic polypeptide, a polynucleotide, a vector, an immunogenic composition, a vaccine, an inhibitor, or a composition according to the invention.

[0038] The invention provides an A baumannii immunogenic polypeptide, a polynucleotide, a vector, an immunogenic composition, a vaccine, an inhibitor or a composition according to the invention for use in a method of treating or preventing an A. baumannii infection in a subject.

[0039] In some embodiments, the method further comprises administering an antibiotic to the subject.

[0040] The subject may be infected with an antibiotic resistant A. baumannii. The subject may be infected with a multidrug resistant (MDR) A. baumannii.

[0041] DESCRIPTION OF THE FIGURES

[0042] Figure 1 - Selection of sequences for A. baumannii protein microarray. (A) 1381 core CDSs represented on the Thai strain AB1615; outer track CDS, middle track contigs, inner track location of conserved CDSs amongst 220 Thai and reference genomes. (B) Cellular localisation of proteins predicted using PSORT (v3.0) using A. baumannii strain MDR-TJ homologue protein sequences. (C) Volcano plot of combined RNAseq data using Salmon quantification and Sleuth analysis; combined highly conserved, differentially expressed genes (strains AB1 , AB1516 & NPRC-AB20) with a Iog2fold expression > 0.6 and a p value < 0.05 (blue = downregulated in human sera compared to LB, red = upregulated, black = no change).

[0043] (D) Volcano plot of CDSs included on protein microarray (blue = included, red = excluded).

[0044] (E) Overview of project pipeline from microarray construction and probing to identification of antigen targets and testing protective efficacy of polyclonal rabbit antibodies against selected antigens.

[0045] Figure 2 - Identification of antigenic A. baumannii proteins. Sera obtained from mice receiving three sub-lethal infections of either the same A. baumannii strain (single strain sera) or three different A. baumannii strains (multi-strain sera A: AB55 + NPRC-AB20 + AB1615- 09, multi-strain sera B: AB3879 + AB1492-09 + AB1615-09) were used for whole cell ELISAs and to probe the A. baumannii protein microarray. (A) CDs (means, error bars = SDs, n=3) for whole cell ELISAs for the A. baumannii strains AB5075 and its unencapsulated wza mutant probed with 1 :100 sera from immunised mice. (B) Results of probing the microarray with mouse sera represented as a heat map of mean IgG MFIs for each mouse immunisation group. (C) Mean (SDs) number of proteins promoting a significant IgG response when assessed by probing the microarray with sera from the different immunisation groups; left panel data presented separately for each immunisation strain(s), right panel pooled results for single versus multistrain immunisation groups. (D) Principal component analysis of microarray data showing separation of the results for the two multistrain immunisation groups. (E) Mean MFI for the top antigens identified by probing the microarray with sera from immunised mice. Black columns, combined data for single strain immunised mice, grey columns combined data for multi-strain immunised mice. Data were analysed using unpaired Student’s t-tests (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant) in panels A (versus PBS control mice) and C (single versus multi-strain results).

[0046] Figure 3 - Preliminary rabbit antibody recognition of selected antigens using clinical isolates. (A) Immunoblots of purified protein antigens probed with respective rabbit IgG antibodies. The predicted molecular weights are indicated by the black arrows. (B) ODs (means, error bars = SDs, n=3) for whole cell ELISAs for clinical A. baumannii strains probed with 1 :100 antibody to the selected antigens. KL; K locus capsule type. Data were analysed using ANOVA with Dunnett’s multiple-comparison test (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant) comparing to the no sera control. (C) Fluorescent microscopy showing IgG deposition (green) of indicated antibodies on A. baumannii strain AB5075 WT and its unencapsulated wza mutant derivative. DNA is stained by DAPI (blue).

[0047] Figure 4 - Passive immunisation with rabbit IgG to the selected antigens is protective in a mouse model of A. baumannii septicaemia. (A-l) Mice were passively immunised by intraperitoneal inoculation of indicated 50 pg rabbit polyclonal IgG or PBS 4 h before intraperitoneal inoculation with 3-6 x 106CFU / mouse of strain AB3879 suspended in PBS with 5% porcine mucin. (J) Mice were passively immunised with either PBS, 50 pg individual rabbit polyclonal IgG, or with a combination of 25 pg a-Ag1 + 25 pg a-Ag11 , followed by infection as in (A). All data are presented as mean (SDs, n > 6) bacterial CFUs in the indicated target organs 18-20 hours after infection and were analysed using Kruskal-Wallis one-way analysis of variance (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant).

[0048] Figure 5 - In vitro flow cytometry assays of the effects of IgG to protective antigens on opsonisation and complement recognition of A. baumannii strains AB3879 (left panels) and AB98 (right panels). (A) and (B) Mean (SDs, n=4) percent of bacteria positive for IgG after incubation with 2° antibody alone or with antibody to A. baumannii antigens. (C) and (D) Mean (SDs, n=4) C3b / iC3b deposition index (% positive x median fluorescent intensity of bacteria staining positive for C3b / iC3b) after incubation in normal human serum (NHS) or NHS plus antibody. (E) and (F) Bacterial association with fresh human neutrophils represented as the mean (SDs, n=3) phagocytosis index (% positive neutrophils x median fluorescent intensity of neutrophils staining positive for FAMSE-labelled A. baumannii) after incubation with NHS or NHS plus antibody. (G) and (H) Mean (SDs, n=4) C5b-8 / C5b-9 deposition index (% positive x median fluorescent intensity of bacteria staining positive for C5b-8 / C5b-9) after incubation in NHS or NHS plus antibody. For all panels, representative flow cytometry plots show IgG binding, C3b / iC3b or C5b-8 / C5b-9 deposition, or neutrophil association for A baumannii AB3879 or AB98 incubated with a-Ag7 (blue) compared to 2° antibody alone (black dotted) or NHS only controls (black solid). Data for all panels were analysed using ANOVA with Dunnett’s multiple-comparison test (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant) to compare to 2° antibody controls (A and B) or compared to NHS only controls (C to H). KL = K locus capsule type.

[0049] Figure 6 - In vitro flow cytometry assays of the effects of IgG to less protective antigens on opsonisation and complement recognition of A. baumannii strains AB3879 (left panels) and AB98 (right panels). (A) and (B) Mean (SDs, n=3) percent of bacteria positive for IgG after incubation with 2° antibody alone or with antibody to A. baumannii antigens. (C) and (D) Mean (SDs, n=3) C3b / iC3b deposition index (% positive x median fluorescent intensity of bacteria staining positive for C3b / iC3b) after incubation in normal human serum (NHS) or NHS plus antibody. Data for all panels were analysed using ANOVA with Dunnett’s multiplecomparison test (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant) to compare to 2° antibody controls (A and B) or compared to NHS only controls (C and D). KL = K locus capsule type.

[0050] Figure 7 - Passive protection by rabbit IgG to the selected antigens in a mouse model of A. baumannii septicaemia requires C3b / iC3b opsonisation and neutrophils. (A & B) Mice were depleted of macrophages, neutrophils or complement using clodronate, a-Ly6G, or cobra venom factor (CVF), respectively, 24 or 48 h prior to passive immunization by intraperitoneal inoculation of 50 pg of rabbit polyclonal IgG or PBS. 4 h post-immunization mice were infected intraperitoneally with 3-6 x 106 CFU / mouse of strain AB3879 suspended in PBS with 5% porcine mucin. Data are presented as mean (SDs, n > 6) bacterial CFUs in the indicated target organs 18-20 hours after infection and were analysed using Kruskal-Wallis one-way analysis of variance (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant).

[0051] Figure 8 - Effect of antibiotics in combination with rabbit IgG to selected antigens against clinical isolates. (A-C) Growth of colistin resistant A. baumannii strain AB3879 at 37°C for 24 h in the presence of normal human serum (NHS) with or without addition of 1 pg / ml colistin (col) and / or 140 pg / ml purified IgG to indicated antigens.

[0052] Figure 9 - Antibody responses to candidate protein PilP (ABUW_0293) selected from > 30% responders, (a) ELISA data showing IgG levels against purified PilP protein in Acinetobacter-infected patients (ACB) during the first week of admission, healthy controls (HC) and other bacterial infected patients (OTH). (b) ELISA data showing IgG responses against purified PilP protein using paired plasma samples from 16 Aci netobacter-'mi ected patients collected at the first week of admission (Wk 0) and two weeks after admission (Wk 2).

[0053] Figure 10 - Ag13 polyclonal rabbit antibody recognition. ELISA data (ODs = means, error bars = SD, n = 3) showing rabbit polyclonal a-Ag13 IgG recognition of (a) clinical A. baumannii isolates representing several K locus capsule types (KL) and sequence types (ST), and IgG recognition of (b) purified protein antigen. Data were analysed using ANOVA with Dunnett’s multiple-comparison test (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant) comparing to the 2° only control.

[0054] Figure 11 - Passive immunisation with rabbit IgG to Ag13 in a mouse model of A. baumannii infection. Mice were passively immunised by intraperitoneal inoculation of 100 pg rabbit polyclonal IgG or PBS 4 h before intraperitoneal inoculation with 3-6 x 106CFU / mouse of A. baumannii strain AB3879 suspended in PBS with 5% porcine mucin. Dot plots represent bacterial CFU in the indicated target organs from individual mice (bars = means (n = 6), error bars = SDs) 20 h after infection. Data were analysed using Kruskal-Wallis oneway analysis of variance compared to PBS controls (*p < 0.05, **p < 0.01 , ***p < 0.001 , ****p < 0.0001 , ns; not significant).

[0055] Figure 12 - Passive immunisation with rabbit IgG to Ag4 is protective in a mouse model of A. baumannii septicaemia. 6 mice per group were injected intraperitoneally with 100 ul PBS or 100 ul purified rabbit IgG a-Ag4 @ 1mg / ml (i.e. 100 ug each), followed 4h later with intraperitoneal injections of 7.09E+06 CFU / mouse of strain AB3879 + 5% mucin. Mice were culled ~20 h post infection and the number of CFUs determined in target organs. Data were analysed using Kruskal-Wallis one-way analysis of variance compared to PBS controls (**p < 0.01).

[0056] DETAILED DESCRIPTION OF THE INVENTION

[0057] IMMUNOGENIC POLYPEPTIDE

[0058] The invention provides an Acinetobacter baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0059] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0060] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0061] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0062] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0063] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0064] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0065] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0066] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof. In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0067] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO:

[0068] 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0069] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO:

[0070] 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0071] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0072] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0073] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0074] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO:

[0075] 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0076] The invention provides an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO:

[0077] 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, or SEQ ID NO: 31 , or a sequence having at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% identity thereto, or an immunogenic fragment thereof.

[0078] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, or SEQ ID NO: 22, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0079] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 1 , or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0080] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, or SEQ ID NO: 32, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0081] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, SEQ ID NO: 6, or SEQ ID NO: 8, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0082] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0083] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0084] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 8, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0085] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0086] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 5, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0087] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 32, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0088] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 1 , or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0089] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 3, or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 84%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0090] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0091] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO:

[0092] 22, or a sequence having at least 85% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0093] The invention provides an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO:

[0094] 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0095] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0096] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0097] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0098] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0099] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0100] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0101] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0102] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto. In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0103] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0104] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0105] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0106] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0107] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0108] In some embodiments, the A. baumannii immunogenic polypeptide comprises SEQ ID NO:

[0109] 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0110] The invention provides an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO:

[0111] 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33 or a sequence having at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% identity thereto. In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 1 , or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0112] In some embodiments, the A baumannii immunogenic polypeptide comprises SEQ ID NO: 3, or a sequence having at least 80% (suitably, at least 84%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0113] In some embodiments, the A. baumannii immunogenic polypeptide consists essentially of SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO:

[0114] 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0115] In some embodiments, the A. baumannii immunogenic polypeptide consists of SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO:

[0116] 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0117] In some embodiments, the A. baumannii immunogenic polypeptide consists of SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0118] In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0119] In some embodiments, the A. baumannii immunogenic polypeptide consists of SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto. In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0120] In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0121] In some embodiments, the A. baumannii immunogenic polypeptide consists of SEQ ID NO: 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0122] In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0123] In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0124] In some embodiments, the A baumannii immunogenic polypeptide consists of SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0125] In some embodiments, the A. baumannii immunogenic polypeptide consists of SEQ ID NO: 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0126] The term “polypeptide” is used in the normal sense to mean a series of residues, typically L- amino acids, connected one to the other typically by peptide bonds between the a-amino and carboxyl groups of adjacent amino acids. The term is synonymous with "protein". By “immunogenic polypeptide”, it is meant that a portion or part of the polypeptide is capable of inducing an immune response. Preferably, the immunogenic polypeptide is capable of inducing a protective immune response against subsequent challenge with A baumannii.

[0127] The term “fragment” typically refers to a selected region of the polypeptide that is of interest either functionally or, for example, in an assay. “Fragment” thus refers to an amino acid that is a portion of a full-length polypeptide or polynucleotide.

[0128] It will be appreciated by one skilled in the art that an immunogenic fragment of the A. baumannii immunogenic polypeptide (i.e. a fragment of a polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO:

[0129] 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 85% identity thereto) can retain the ability to produce an immune response.

[0130] As used herein, the term “immunogenic fragment” means a fragment of the specified sequence which retains the ability to induce an immune response.

[0131] Thus, the invention provides an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0132] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO:

[0133] 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0134] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0135] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0136] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0137] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0138] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0139] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0140] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0141] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto. In some embodiments, the immunogenic fragment is an immunogenic fragment of an A baumannii immunogenic polypeptide comprising SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0142] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0143] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0144] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0145] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0146] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0147] The invention provides an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID

[0148] NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26,

[0149] SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ

[0150] ID NO: 33, or a sequence having at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% identity thereto.

[0151] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A baumannii immunogenic polypeptide comprising SEQ ID NO: 1 , or a sequence having at least 70% (suitably, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0152] In some embodiments, the immunogenic fragment is an immunogenic fragment of an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 3, or a sequence having at least 80% (suitably, at least 84%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto.

[0153] The A. baumannii immunogenic polypeptide or immunogenic fragment of the invention comprises at least one immunogenic epitope, for example at least one immunogenic peptide epitope.

[0154] The immunogenic epitope induces an immune response when administered to a subject. The immunogenic epitope may induce a T cell response (e.g. a cytotoxic T cell response) and / or a humoral immune response in a subject. Preferably, the immunogenic epitope may induce a memory humoral immune response in a subject.

[0155] Suitably, the present immunogenic polypeptide or immunogenic fragment thereof is capable of inducing a humoral response comprising an antibody response that is capable of binding and / or opsonising A. baumannii, for example to activate the complement system and / or promote opsonophagocytosis of the bacteria.

[0156] Methods for determining if a polypeptide or fragment thereof is immunogenic, i.e. induces an immune response, are well-known in the art and include, for example, immune cell activation assays using CD4+and / or CD8+T cells or B cells. Suitable markers for activation may include cell proliferation and / or signature cytokines (e.g. for T cells - I FNy, TNFa, IL-2, IL-13 and / or IL-17) production using methods such as ELISpot. Suitably, a polypeptide or fragment thereof may be assayed for the production of antibodies, for example, using the method described herein.

[0157] An immunogenic epitope refers to an epitope which is recognised by either a T cell receptor (TCR) or a B cell receptor (BCR) / antibody. Suitably, the immunogenic epitope is a T cell epitope or a B cell epitope. In an adaptive immune response, T cells are capable of recognising internal epitopes of a protein antigen. Antigen presenting cells (APC) take up protein antigens and degrade them into short peptide fragments. A peptide may bind to a major histocompatibility complex (MHC) class II molecule within the cell and be carried to the cell surface. When presented at the cell surface in the context of an MHC molecule, the peptide may be recognised by a T cell (via the TCR), in which case the peptide is a T cell epitope.

[0158] In one embodiment, the immunogenic epitope (e.g. immunogenic peptide epitope) is a T cell epitope. Suitably, a peptide epitope may be capable of being recognised by a TCR when presented at the cell surface in the context of a MHC molecule. Peptides which bind to MHC class II molecules are typically between 8 and 20 amino acids in length, more usually between 10 and 17 amino acids in length, and can be longer (for example up to 40 amino acids). These peptides lie in an extended conformation along the MHC II peptide-binding groove which (unlike the MHC class I peptide-binding groove) is open at both ends. The peptide is held in place mainly by main-chain atom contacts with conserved residues that line the peptide- binding groove.

[0159] Peptides that bind to MHC class I are typically 7 to 13, more usually 8 to 10 amino acids in length. The binding of the peptide is stabilised at its two ends by contacts between atoms in the main chain of the peptide and invariant sites in the peptide-binding groove of all MHC class I molecules. There are invariant sites at both ends of the groove which bind the amino and carboxy termini of the peptide. Variations in peptide length are accommodated by a kinking in the peptide backbone, often at proline or glycine residues that allow flexibility.

[0160] A T cell epitope may thus be a peptide derivable from an antigen which is capable of binding to the peptide-binding groove of an MHC molecule and being recognised by a T cell in the context of an MHC molecule.

[0161] The minimal T cell epitope is the shortest fragment derivable from a T cell epitope, which is capable of binding to the peptide-binding grove of an MHC class I or II molecule and being recognised by a T cell in the contact of an MHC molecule. For a given immunogenic region, it is typically possible to generate a “nested set” of overlapping peptides which act as epitopes, all of which contain the minimal epitope but differ in their flanking regions.

[0162] Thus, it is possible to identify the minimal T cell epitope for a particular MHC molecule: T cell combination by measuring the response to truncated peptides, i.e. peptide fragments. For example, if a response is obtained to the peptide comprising residues 1-20 in the overlapping library, sets which are truncated at both ends (i.e. 1-19, 1-18, 1-17 etc. and 2-20, 3-20, 4-20 etc.) can be used to identify the minimal epitope.

[0163] Methods for identifying T cell epitopes within a protein or peptide sequence are known in the art and include, but are not limited to MHC binding assays and / or immune cell activation assays using CD4+and / or CD8+T cells. Suitable markers for activation may include cell proliferation and / or signature cytokines (e.g. for T cells - I FNy, TNFa, IL-13 and / or IL-17) production using methods such as ELISpot.

[0164] Bioinformatics methods for predicting T cell epitopes from a protein are known in the art and include, but are not limited to, EpiDOCK, MotifScan, Rankpep, SYFPEITHI, MAPPP, PREDIVAC, PEPVAC, EPISOPT, Vaxign, MHCPred, EpiTOP, BIMAS, TEPITOPE, Propred, E[iJen, IEDB-MHCI, IEDB-MHCII, MULTIPRED2, MHC2PRED, NetMHC, NetMHCll, NetMHCpan, NetMHCHpan, nHLApred, SVMHC, SVRMHC, NetCTL and WAPP.

[0165] In one embodiment, the immunogenic epitope is a B cell epitope. A B cell epitope refers to an epitope which is capable of binding to a B cell receptor (BCR) / antibody. B cell epitopes are generally divided into two categories, linear epitopes and conformational epitopes, based on their structure and interaction with the antibody. A linear epitope is formed by the 3D conformation adopted by the interaction of contiguous amino acid residues. In contrast, a conformational epitope is formed by the 3D conformation adopted by the interaction of discontiguous amino acid residues.

[0166] Suitably, the immunogenic epitope may be a linear B cell epitope. Suitably, the immunogenic epitope may be a conformational B cell epitope.

[0167] Bioinformatics methods for predicting B cell epitopes from a protein are known in the art and include, but are not limited to, linear B cell epitope predictors such as PEOPLE, BepiPred, ABCpred, LBtope, BCPREDS and SVMtrip and conformational B cell epitope predictors such as CEP, DiscoTope, ElliPro, PEPITO, SEPPA, EPITOPIA, EPSVR, EPIPRED, PEASE, MIMOX, PEPITOPE, EpiSearch, MIMOPRO and CBTOPE.

[0168] Suitably, B cell epitopes may be identified from epitopes bound by antibodies isolated from a subject previously infected / recovered from an A. baumannii infection and / or previously vaccinated with an antigen from A. baumannii. Methods for determining the epitope bound by an antibody (i.e. a B cell epitope) include, but are not limited to, X-ray crystallography, cryogenic electron microscopy, array-based oligo-peptide screening, site-directed mutagenesis mapping, high-throughput mutagenesis mapping, hydrogen-deuterium exchange and cross-linking-coupled mass spectrometry. The A baumannii immunogenic polypeptide or immunogenic fragment may comprise at least one B cell epitope and / or at least one T cell epitope as defined herein. Suitably, the A. baumannii immunogenic polypeptide or immunogenic fragment may comprise at least one B cell epitope and at least one T cell epitope as defined herein.

[0169] Suitably, the A. baumannii immunogenic polypeptide or immunogenic fragment may comprise at least one B cell epitope.

[0170] The A. baumannii immunogenic fragment may comprise or consist essentially of an immunogenic epitope. The A. baumannii immunogenic fragment may consist of an immunogenic epitope.

[0171] The A. baumannii immunogenic fragment may comprise or consist essentially of an immunogenic peptide epitope. The A. baumannii immunogenic fragment may consist of an immunogenic peptide epitope.

[0172] The peptide epitope(s) may independently be at least 7, at least 10, at least 15, at least 20, at least 30, at least 40 or at least 50 amino acids in length.

[0173] The peptide epitope(s) may independently be about 7 to about 50, or about 7 to about 24, or about 9 to about 22 amino acids in length.

[0174] The peptide epitope(s) may independently be about 50 (suitably, about 49, about 48, about 47 or about 46) or fewer amino acids in length.

[0175] For example, the immunogenic epitope may comprise or consist of about 7 to about 50, or about 7 to about 24, or about 9 to about 22 consecutive amino acids of any one of SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33.

[0176] It will be appreciated by one skilled in the art that a variant of an immunogenic fragment of any one of SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33 can retain the ability to produce an immune response.

[0177] The variant may have one, two or three amino acid substitutions. The variant may have one, two or three amino acid substitutions and / or may have one, two or three amino acid deletions at the N- and / or C-terminus. Suitably, the variant may have one, two or three amino acid substitutions and one, two or three amino acid deletions at the N- and / or C-terminus.

[0178] In some preferred embodiments, said amino acid substitutions are conservative amino acid substitutions.

[0179] Amino acids with similar biochemical properties may be defined as amino acids which can be substituted via a conservative substitution.

[0180] Conservative amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and / or the amphipathic nature of the residues. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; and amino acids with uncharged polar head groups having similar hydrophilicity values include leucine, isoleucine, valine, glycine, alanine, asparagine, glutamine, serine, threonine, phenylalanine, and tyrosine.

[0181] Conservative substitutions may be made, for example according to Table 1 below. Amino acids in the same block in the second column and preferably in the same line in the third column may be substituted for each other:

[0182] Table 1

[0183] The present invention also encompasses homologous substitution (substitution and replacement are both used herein to mean the interchange of an existing amino acid residue, with an alternative residue) i.e. like-for-like substitution such as basic for basic, acidic for acidic, polar for polar etc. An aliphatic, non-polar amino acid may be a glycine, alanine, proline, isoleucine, leucine or valine residue.

[0184] An aliphatic, polar uncharged amino may be a cysteine, serine, threonine, methionine, asparagine or glutamine residue.

[0185] An aliphatic, polar charged amino acid may be an aspartic acid, glutamic acid, lysine or arginine residue.

[0186] An aromatic amino acid may be a histidine, phenylalanine, tryptophan or tyrosine residue.

[0187] Suitably, a conservative substitution may be made between amino acids in the same line in Table 1.

[0188] Sequence comparisons can be conducted by eye, or more usually, with the aid of readily available sequence comparison programs. These publicly and commercially available computer programs can calculate sequence identity between two or more sequences.

[0189] Sequence identity may be calculated over contiguous sequences, i.e. one sequence is aligned with the other sequence and each amino acid in one sequence directly compared with the corresponding amino acid in the other sequence, one residue at a time. This is called an “ungapped” alignment. Typically, such ungapped alignments are performed only over a relatively short number of residues (for example less than 50 contiguous amino acids).

[0190] Although this is a very simple and consistent method, it fails to take into consideration that, for example, in an otherwise identical pair of sequences, one insertion or deletion will cause the following amino acid residues to be put out of alignment, thus potentially resulting in a large reduction in % homology when a global alignment is performed. Consequently, most sequence comparison methods are designed to produce optimal alignments that take into consideration possible insertions and deletions without penalising unduly the overall homology score. This is achieved by inserting “gaps” in the sequence alignment to try to maximise local homology.

[0191] However, these more complex methods assign “gap penalties” to each gap that occurs in the alignment so that, for the same number of identical amino acids, a sequence alignment with as few gaps as possible - reflecting higher relatedness between the two compared sequences - will achieve a higher score than one with many gaps. “Affine gap costs” are typically used that charge a relatively high cost for the existence of a gap and a smaller penalty for each subsequent residue in the gap. This is the most commonly used gap scoring system. High gap penalties will of course produce optimised alignments with fewer gaps. Most alignment programs allow the gap penalties to be modified. However, it is preferred to use the default values when using such software for sequence comparisons. For example, when using the GCG Wisconsin Bestfit package (see below) the default gap penalty for amino acid sequences is -12 for a gap and -4 for each extension.

[0192] Calculation of maximum % sequence identity therefore firstly requires the production of an optimal alignment, taking into consideration gap penalties. A suitable computer program for carrying out such an alignment is the GCG Wisconsin Bestfit package (University of Wisconsin, U.S.A; Devereux et a / ., 1984, Nucleic Acids Research 12:387). Examples of other software than can perform sequence comparisons include, but are not limited to, the BLAST package (see Ausubel et al., 1999 ibid - Chapter 18), FASTA (Atschul et al., 1990, J. Mol. Biol., 403-410) and the GENEWORKS suite of comparison tools. Both BLAST and FASTA are available for offline and online searching (see Ausubel et al., 1999 ibid, pages 7-58 to 7-60). However, it is preferred to use the GCG Bestfit program.

[0193] In one embodiment, the sequence identity is determined across the entirety of the sequence selected from SEQ ID NO: 1 to 33. In one embodiment, the sequence identity is determined across the entirety of the candidate sequence being compared to a sequence selected from SEQ ID NO: 1 to 33.

[0194] Although the final sequence identity can be measured in terms of identity, the alignment process itself is typically not based on an all-or-nothing pair comparison. Instead, a scaled similarity score matrix is generally used that assigns scores to each pairwise comparison based on chemical similarity or evolutionary distance. An example of such a matrix commonly used is the BLOSUM62 matrix - the default matrix for the BLAST suite of programs. GCG Wisconsin programs generally use either the public default values or a custom symbol comparison table if supplied (see user manual for further details). It is preferred to use the public default values for the GCG package, or in the case of other software, the default matrix, such as BLOSUM62.

[0195] Once the software has produced an optimal alignment, it is possible to calculate % sequence identity. The software typically does this as part of the sequence comparison and generates a numerical result.

[0196] The sequence may have one or more deletions, insertions or substitutions of amino acid residues which produce a silent change and result in a functionally equivalent molecule. These sequences are encompassed by the present invention. Deliberate amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and / or the amphipathic nature of the residues as long as the activity is retained. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; and amino acids with uncharged polar head groups having similar hydrophilicity values include leucine, isoleucine, valine, glycine, alanine, asparagine, glutamine, serine, threonine, phenylalanine, and tyrosine.

[0197] The immunogenic polypeptide may be conserved across multiple A baumannii strains, for example at least two, at least three, at least four, at least five A. baumannii strains. Preferably, the immunogenic polypeptide is conserved across at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 110, at least 120, at least 130, at least 140, at least 150, at least 160, at least 170, at least 180, at least 190, at least 200, at least 210, at least 220, at least 230, at least 240, at least 250 A baumannii strains.

[0198] The immunogenic polypeptide may be conserved across multiple clinical A. baumannii isolates, for example at least two, at least three, at least four, at least five clinical A. baumannii isolates. Preferably, the immunogenic polypeptide is conserved across at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 110, at least 120, at least 130, at least 140, at least 150, at least 160, at least 170, at least 180, at least 190, at least 200, at least 210, at least 220, at least 230, at least 240, at least 250 clinical A. baumannii isolates.

[0199] As used herein, the term “conserved” refers to the presence of a gene encoding a polypeptide in at least 70% of A. baumannii strains and / or clinical isolates, wherein the gene encodes a polypeptide having at least 70% identity to an immunogenic polypeptide as defined herein. In some embodiments, the gene encodes a polypeptide having at least 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% identity to an immunogenic peptide as defined herein.

[0200] In some embodiments, the immunogenic polypeptide is at least 70%, at least 75%, at least 80%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91 %, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% conserved. That is, the immunogenic polypeptide is present in at least 70% of A. baumannii strains and / or clinical isolates. In some embodiments, the immunogenic polypeptide is at least 80% conserved. In some embodiments, the immunogenic polypeptide is at least 90% conserved. In some embodiments, the immunogenic polypeptide is at least 95% conserved. In some embodiments, the immunogenic polypeptide is at least 99% conserved. In some embodiments, the immunogenic polypeptide is 100% conserved.

[0201] The immunogenic polypeptide may be expressed at the surface of A. baumannii, for example the immunogenic polypeptide may be expressed at the bacterial envelope (e.g. the outer membrane, periplasm, or cytoplasmic membrane). The immunogenic polypeptide may be expressed extracellularly. The immunogenic polypeptide may be expressed in the cytoplasm.

[0202] In some embodiments, the immunogenic polypeptide is expressed at the A baumannii bacterial envelope. Preferably, the immunogenic polypeptide is expressed at the A baumannii outer membrane. Preferably, the immunogenic polypeptide is an outer membrane protein.

[0203] Methods for determining protein expression and localisation are known in the art. For example, protein localisation may be predicted using prediction software known in the art, including but not limited to the PSORT family of programs for subcellular localization predict (https : / / www. psort. org / ) .

[0204] Expression of the corresponding gene to an immunogenic A. baumannii polypeptide may be upregulated in the presence of human sera when measured by Iog2 transcripts of RNAseq data compared to culture in broth, and this may reflect upregulation during human infection.

[0205] POLYNUCLEOTIDE

[0206] In a further aspect, the present invention provides a polynucleotide encoding one or more A. baumannii immunogenic polypeptides of the invention.

[0207] Thus, in some embodiments, the invention provides a polynucleotide encoding one or more A. baumannii immunogenic polypeptides comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 70%, such as at least 85%, identity thereto, or an immunogenic fragment thereof.

[0208] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0209] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof. In some embodiments, the polynucleotide encodes an A baumannii immunogenic polypeptide comprising SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0210] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0211] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0212] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0213] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0214] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0215] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0216] In some embodiments, the polynucleotide encodes an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof. The terms “polynucleotide” and "nucleic acid sequence" as used herein are interchangeable. “Polynucleotide” generally refers to any polyribonucleotide or polydeoxribonucleotide, which may be unmodified RNA or DNA or modified RNA or DNA. A polynucleotide in relation to the present invention can be a double stranded or single stranded molecule and includes genomic DNA, cDNA, synthetic DNA, RNA and a chimeric DNA / RNA molecule.

[0217] It will be understood by a skilled person that numerous different polynucleotides can encode the same polypeptide as a result of the degeneracy of the genetic code. In addition, it is to be understood that skilled persons may, using routine techniques, make nucleotide substitutions that do not affect the polypeptide sequence encoded by the polynucleotides described here to reflect the codon usage of any particular host organism in which the polypeptides are to be expressed.

[0218] Typically, the nucleic acid sequence encompassed by the scope of the present invention is prepared using recombinant DNA techniques (i.e. recombinant DNA).

[0219] VECTOR

[0220] In a further aspect, the present invention provides a vector comprising one or more polynucleotides according to the invention.

[0221] A vector is a tool that allows or facilitates the transfer of an entity from one environment to another. In accordance with the present invention, and by way of example, some vectors used in recombinant nucleic acid techniques allow entities, such as a nucleic acid of the invention, to be transferred into and expressed by a target cell. The vector may facilitate the integration of the nucleic acid sequence of the invention to maintain the nucleic acid sequence of the invention and its expression within the target cell.

[0222] The vector may be or may include an expression cassette (also termed an expression construct). Expression cassettes as described herein comprise regions of nucleic acid containing sequences capable of being transcribed. Thus, sequences encoding mRNA, tRNA and rRNA are included within this definition.

[0223] The term "cassette" - which is synonymous with "construct" - includes a nucleic acid sequence directly or indirectly attached to a promoter. The expression cassettes for use in the invention comprise a promoter for the expression of the nucleic acid sequence of the invention. Preferably, the cassette comprises at least a nucleic acid sequence of the invention operably linked to a promoter. The choice of expression cassette, e.g. plasmid or viral vector, will often depend on the host cell into which it is to be introduced. The vector may contain one or more selectable marker genes (e.g. a kanamycin resistance gene) and / or traceable marker gene(s) (e.g. a gene encoding green fluorescent protein (GFP)).

[0224] INHIBITOR

[0225] In a further aspect, the invention provides an inhibitor which is capable of binding to an A baumannii immunogenic polypeptide or immunogenic fragment of the invention.

[0226] Thus, in some embodiments, the invention provides an inhibitor which is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10, SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 , or SEQ ID NO: 33, or a sequence having at least 70%, such as at least 85%, identity thereto, or an immunogenic fragment thereof.

[0227] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, or SEQ ID NO: 22, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0228] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, or SEQ ID NO: 1 , or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0229] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, or SEQ ID NO: 32, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0230] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 4, SEQ ID NO: 6, or SEQ ID NO: 8, or SEQ ID NO: 33, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0231] In some embodiments, the inhibitor is capable of binding to an A baumannii immunogenic polypeptide comprising SEQ ID NO: 6 or SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0232] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 6 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0233] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 8, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0234] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 33 or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0235] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 4, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0236] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 5, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0237] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 32, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0238] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 1 , or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0239] In some embodiments, the inhibitor is capable of binding to an A baumannii immunogenic polypeptide comprising SEQ ID NO: 3, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0240] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 9, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0241] In some embodiments, the inhibitor is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 22, or a sequence having at least 85% (suitably, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%) identity thereto, or an immunogenic fragment thereof.

[0242] Binding may be determined using a method known in the art, including but not limited to cellbased binding assays using FACS or surface plasmon resonance, or protein-based binding assays such as ELISA or Western blot.

[0243] The inhibitor binds to A. baumannii within an A. baumannii immunogenic polypeptide as described herein. Preferably, the inhibitor may be capable of binding to an immunogenic epitope within an A. baumannii immunogenic polypeptide as described herein. The inhibitor may be capable of binding to an immunogenic peptide epitope within an A. baumannii immunogenic polypeptide as described herein.

[0244] The inhibitor may be selected from one or more of the following: an antibody, an Ig fusion protein, a polypeptide, a peptide, a polynucleotide, a small molecule, a non-antibody scaffold, an aptamer, or combinations thereof.

[0245] Preferably, the inhibitor is an antibody which is capable of binding to an A. baumannii immunogenic polypeptide according to the invention.

[0246] The inhibitor may reduce or inhibit at least part of the A. baumannii lifecycle in a host organism / tissue / cell. For example, the inhibitor may promote cell lysis, such as by initiating the complement cascade and / or formation of membrane attack complex. The inhibitor may promote clearance of the bacteria from a host organism / tissue / cell. For example, the inhibitor may bind and / or opsonise the A. baumannii, for example to activate the complement system and / or promote opsonophagocytosis of the bacteria. The inhibitor (e.g. an antibody) may be capable of selectively binding to an A baumannii immunogenic polypeptide (e.g. an A. baumannii immunogenic epitope as described herein) and thus may have a greater binding affinity for an A. baumannii immunogenic polypeptide as compared to its binding affinity for other proteins / molecules. Preferably, the inhibitor does not bind to other proteins or binds with a greatly reduced affinity compared to the binding to said A. baumannii immunogenic polypeptide (e.g. with an affinity of at least 10, 50, 100, 500, 1000 or 10000 times less than its affinity for said A. baumannii immunogenic polypeptide). Thus, the inhibitor as referred to herein may bind to said A. baumannii immunogenic polypeptide (e.g. an A. baumannii immunogenic epitope as described herein) with at least 10, 50, 100, 500, 1000 or 10000 times the affinity of its binding to other proteins. The binding affinity of the inhibitor can be determined using methods well known in the art, such as with the Biacore system.

[0247] The inhibitor may have a high binding affinity for said A. baumannii immunogenic polypeptide (e.g. an A. baumannii immunogenic epitope as described herein), i.e. may have a Kd in the range of 10'5M, 10'6M, 10'7M or 10'9M or less. Any appropriate method of determining Kd may be used. Preferably, the Kd is determined by testing various concentrations of the test agent against various concentrations of antigen (i.e. A. baumannii immunogenic polypeptide as described herein), in vitro to establish a saturation curve, for example using the Lineweaver- Burk method, or by using commercially available binding model software, such as the 1 :1 binding model in the BIAcore 1000 Evaluation software.

[0248] In some embodiments, said inhibitor is an antibody.

[0249] In some embodiments, said antibody is a monoclonal antibody, a humanised antibody, a single-chain antibody or an antibody fragment. Suitably antibodies include, but are not limited to, monoclonal and polyclonal antibodies, engineered antibodies including chimeric, CDR- grafted and humanised antibodies, single-chain antibodies, antibody fragments and artificially selected antibodies produced using phage display or alternative techniques.

[0250] Suitably the inhibitor is a polyclonal antibody.

[0251] Suitably the inhibitor is a monoclonal antibody.

[0252] Suitable antibody fragments capable of binding to a selected target, include Fv, ScFv, F(ab') and F(ab')2. In addition, alternatives to classical antibodies may also be used in the invention, for example “avibodies”, “avimers”, “anticalins”, “nanobodies” and “DARPins”.

[0253] Reference to “scFv” or “single-chain variable fragment” as used herein includes molecules wherein the variable heavy (VH) and variable light chain (VL) of an antibody are linked via a flexible oligopeptide. A scFv is thus a fusion between at least one variable heavy and at least one variable light chain.

[0254] Reference to a “complementarity determining region” or “CDR” as used herein refers to the regions of hypervariability within antibodies which bind to the specific antigen. The CDRs of an antibody thus usually provide an antibody with its binding specificity. Three CDRs may be present in the variable region of each heavy chain of an intact antibody molecule (i.e. comprising two full length heavy and two full length light chains) and three CDRs may be present in the variable region of each light chain (heavy chain CDRs 1 , 2 and 3 and light chain CDRs 1 , 2 and 3, numbered from the amino to the carboxy terminus). The CDRs of the variable regions of a heavy and light chain of an antibody can be predicted from the heavy and light chain variable region sequences of the antibody, using prediction software known in the art, including but not limited to the Abysis algorithm (www.bioinf.org.uk / abysis / sequence_input / key_annotation / key_annotation.cgi) and IMGT / V- QLIEST software, e.g. the IMGT algorithm (ImMunoGeneTics) (www.lMGT.org^Lefranc et al, 2009 NAR 37:D1006-D1012; and Lefranc 2003, Leukemia 17: 260-266). CDRs may vary in length, depending on the antibody from which they are predicted and between the heavy and light chains. A CDR for example, may range from 2 amino acids in length to 20 amino acids in length, e.g. from 3-14 amino acids in length. The Kabat nomenclature is followed herein in order to define the positioning of the CDRs (Kabat et al., 1991 , 5thEd. Public Health Service, National Institutes of Health, Bethesda, MD, 647-669, incorporated herein by reference).

[0255] The term “heavy chain variable region” (VH domain) as used herein refers to the variable region of a heavy chain of an antibody molecule.

[0256] The term “light chain variable region” (VL domain) as used herein refers to the variable region of a light chain of an antibody molecule.

[0257] Antibodies capable of binding to A. baumannii (e.g. within an A. baumannii immunogenic polypeptide as described herein) can be produced using any method known in the art. Methods for the production of monoclonal antibodies, recombinant antibodies and aptamers are reviewed in Groff et al. (Biotechnology Advances 2015, 33(8): 1787-1798) and Dangi et al. (Front Pharmacol. 2018; 9: 630) - each of which is incorporated herein by reference.

[0258] Antibodies capable of binding and / or inhibiting A. baumannii may be identified using any method known in the art, including an assay for binding of A. baumannii immunogenic polypeptide on the surface of a cell, e.g. FACS. IMMUNOGENIC COMPOSITION

[0259] The invention provides an immunogenic composition comprising one or more A baumannii immunogenic polypeptides according to the invention.

[0260] The invention provides an immunogenic composition comprising one or more polynucleotides according to the invention.

[0261] The invention provides an immunogenic composition comprising one or more vectors according to the invention.

[0262] The immunogenic composition may further comprise a pharmaceutically acceptable carrier, diluent or excipient. The immunogenic composition may be a pharmaceutical composition.

[0263] The immunogenic composition may induce an immune response when administered to a subject. The immunogenic composition may induce a T cell response (e.g. a cytotoxic T cell response) and / or a humoral immune response in a subject. Preferably, the immunogenic composition may induce a memory humoral immune response in a subject.

[0264] Suitably, the present immunogenic composition is capable of inducing a humoral response comprising an antibody response that is capable of binding and / or opsonising A. baumannii, for example to activate the complement system and / or promote opsonophagocytosis of the bacteria.

[0265] Methods for determining if an immunogenic composition induces an immune response are well-known in the art and include, for example, immune cell activation assays using CD4+and / or CD8+T cells or B cells as described herein above.

[0266] Suitably, the induction of humoral immunity to A. baumannii may refer to B cell activity. The activity of B cells may be determined using methods which are known in the art. For example, the activity of B cells may be determined by determining antibody (e.g. IgG or IgM) production or antiviral cytokine production (e.g. IFNy or IL-6) following treatment with the immunogenic composition. Enhancement of B cell activity may be determined by an increase in antibody or effector cytokine (e.g. percentage of effector cytokine positive cells) as determined by flow cytometry or amount of effector cytokine mRNA or protein as determined by qPCR, ELISA or ELISPOT, respectively) compared to a control experiment which has not been treated with the immunogenic composition.

[0267] For example, levels of antiviral cytokine production in B-cells treated with an immunogenic composition may be increased by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 75% or at least 100% compared to control cells which have not been treated with the immunogenic composition. Suitably, the induction of T cell immunity (e.g. of humoral immunity) to A baumannii may refer to CD4+T cell activity. The activity of CD4+T cells may be determined using methods which are known in the art. For example, CD4+T cell activity may be assessed by determining effector cytokine production (i.e. IFNy, IL-21 or IL-4) following treatment with the immunogenic composition. Enhancement of CD4+T cell activity may be determined by an increase in effector cytokine (e.g. percentage of effector cytokine positive cells as determined by flow cytometry or amount of effector cytokine mRNA or protein as determined by qPCR, ELISA or ELISPOT, respectively) compared to a control experiment which has not been treated with the immunogenic composition.

[0268] For example, levels of effector cytokine in CD4+T cell treated with an immunogenic composition may be increased by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 75% or at least 100% compared to control cells which have not been treated with the immunogenic composition.

[0269] Suitably, induced T cell immunity to A. baumannii may refer to CD8+ T cell activity. The activity of CD8+T cells may be determined using methods which are known in the art. For example, CD8+T cell activity may be assessed by determining effector cytokine production (i.e. IFNy / TNF / IL-2) following treatment with the immunogenic composition. Enhancement of CD8+T cell activity may be determined by an increase in effector cytokine (e.g. percentage of effector cytokine positive cells as determined by flow cytometry or amount of effector cytokine mRNA or protein as determined by qPCR or ELISA or ELISPOT, respectively) compared to a control experiment which has not been treated with the immunogenic composition. Proliferative expansion of antigen-specific CD8+T cells can also be assessed by staining with MHC / peptide multimers.

[0270] For example, levels of effector cytokine in CD8+T cells treated with an immunogenic composition may be increased by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 75% or at least 100% compared to control cells which have not been treated with the immunogenic composition.

[0271] In the context of the present invention, an immunogenic composition is administered to a subject in order to enhance the subject’s immune response to A. baumannii infection.

[0272] In the context of the present invention, a pharmaceutical composition is administered to a subject in order to treat and / or prevent an A. baumannii infection.

[0273] Suitably, the immunogenic composition will be formulated for administration by injection, for example by intramuscular, intradermal, intravenous or sub-cutaneous injection. An immunogenic composition or a pharmaceutical composition will generally be administered in admixture with a pharmaceutical carrier, excipient or diluent, particularly for human therapy. Suitably, an immunogenic composition or a pharmaceutical composition may be administered in admixture with an adjuvant, particularly for human therapy.

[0274] VACCINE

[0275] The invention provides a vaccine comprising one or more A. baumannii immunogenic polypeptides according to the invention.

[0276] The invention provides a vaccine comprising one or more polynucleotides according to the invention.

[0277] The invention provides a vaccine comprising one or more vectors according to the invention.

[0278] The vaccine may induce a protective immune response when administered to a subject, i.e. an immune response that is protective against subsequent challenge with A. baumannii. The vaccine may induce a protective T cell response (e.g. a cytotoxic T cell response) and / or a protective humoral immune response in a subject. Preferably, the vaccine may induce a memory humoral immune response in a subject.

[0279] Suitably, the present vaccine is capable of inducing a humoral response comprising an antibody response that is capable of binding and / or opsonising A. baumannii, for example to activate the complement system and / or promote opsonophagocytosis of the bacteria.

[0280] Methods for determining if a vaccine induces a protective immune response are well-known in the art and include, for example, vaccination of a subject and subsequent challenge (either natural or deliberate) with A. baumannii.

[0281] In the context of the present invention, a vaccine is administered to a subject in order to enhance the subject’s immune response to A. baumannii infection.

[0282] In the context of the present invention, a vaccine is administered to a subject in order to treat and / or prevent an A. baumannii infection.

[0283] Suitably, the vaccine will be formulated for administration by injection, for example by intramuscular, intradermal, intravenous or sub-cutaneous injection.

[0284] A vaccine will generally be administered in admixture with a pharmaceutical carrier, excipient or diluent, particularly for human therapy. Suitably, a vaccine may be administered in admixture with an adjuvant, particularly for human therapy. COMPOSITION

[0285] The invention provides a composition comprising one or more inhibitors according to the invention.

[0286] In some embodiments, the invention provides a composition comprising one of more antibodies according to the invention.

[0287] In some embodiments, the composition comprises an antibody that is capable of binding to an A baumannii immunogenic polypeptide comprising SEQ ID NO: 32, or a sequence having at least 70%, such as at least 85% identity thereto, or an immunogenic fragment thereof, and an antibody that is capable of binding to an A. baumannii immunogenic polypeptide comprising SEQ ID NO: 5, or a sequence having at least 70%, such as at least 85% identity thereto, or an immunogenic fragment thereof.

[0288] The composition may further comprise a pharmaceutically acceptable carrier, diluent or excipient. The composition may be a pharmaceutical composition.

[0289] In the context of the present invention, a composition or pharmaceutical composition is administered to a subject in order to treat and / or prevent an A. baumannii infection.

[0290] The composition or pharmaceutical composition may be administered to a subject in order to confer passive immunity to A. baumannii.

[0291] Suitably, the composition or pharmaceutical composition will be formulated for administration by injection, for example by intramuscular, intradermal, intravenous or sub-cutaneous injection.

[0292] A composition or a pharmaceutical composition will generally be administered in admixture with a pharmaceutical carrier, excipient or diluent, particularly for human therapy. Suitably, an composition or a pharmaceutical composition may be administered in admixture with an adjuvant, particularly for human therapy.

[0293] METHODS OF PREVENTION / TREATMENT

[0294] The invention provides a method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an A. baumannii immunogenic polypeptide according to the invention.

[0295] The invention provides a method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject a polynucleotide or vector according to the invention. The invention provides a method of treating or preventing an A baumannii infection in a subject comprising administering to the subject an immunogenic composition or vaccine according to the invention.

[0296] The invention provides a method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an inhibitor or antibody according to the invention.

[0297] The invention provides a method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject a composition according to the invention.

[0298] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an A. baumannii immunogenic polypeptide according to the invention.

[0299] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii a polynucleotide or a vector according to the invention.

[0300] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an immunogenic composition or vaccine according to the invention.

[0301] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an inhibitor or antibody according to the invention.

[0302] The invention provides a method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii a composition according to the invention.

[0303] The invention provides an A. baumannii immunogenic polypeptide according to the invention for use in a method of treating or preventing an A. baumannii infection in a subject.

[0304] The invention provides a polynucleotide or a vector according to the invention for use in a method of treating or preventing an A. baumannii infection in a subject.

[0305] The invention provides an immunogenic composition or vaccine according to the invention for use in a method of treating or preventing an A. baumannii infection in a subject. The invention provides an inhibitor or antibody according to the invention for use in a method of treating or preventing an A baumannii infection in a subject.

[0306] The invention provides a composition according to the invention, for use in a method of treating or preventing an A. baumannii infection in a subject.

[0307] The invention provides for the use of an A. baumannii immunogenic polypeptide according to the invention for the manufacture of a medicament for the treatment or prevention of an A. baumannii infection.

[0308] The invention provides for the use of a polynucleotide or a vector according to the invention for the manufacture of a medicament for the treatment or prevention of an A. baumannii infection.

[0309] The invention provides for the use of an immunogenic composition or vaccine according to the invention for the manufacture of a medicament for the treatment or prevention of an A. baumannii infection.

[0310] The invention provides for the use of an inhibitor or antibody according to the invention for the manufacture of a medicament for the treatment or prevention of an A. baumannii infection.

[0311] The invention provides for the use of a composition according to the invention for the manufacture of a medicament for the treatment or prevention of an A. baumannii infection.

[0312] The term “treat / treatment / treating” may refer generally to administering an immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention to a subject having an existing disease or condition in order to reduce, alleviate or eliminate one or more symptoms associated with the disease, disorder or condition which is being treated and / or to slow down, reduce or block the progression of the disease, disorder or condition which is being treated.

[0313] The term "prevent / prevention / prophylaxis” may refer generally to administering an immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention to a subject having an existing disease or condition or at risk of developing a disease or condition in order to delay or prevent the onset of the symptoms of the disease, disorder or condition. Prevention may be absolute (such that no disease occurs) or may be effective only in some individuals or for a limited amount of time. The immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention may be administered to the subject in combination with at least one further pharmaceutically active agent.

[0314] In some embodiments, the immunogenic polypeptide, immunogenic composition or vaccine of the invention is administered to the subject in combination with at least one further pharmaceutically active agent.

[0315] In some embodiments, the inhibitor, antibody or composition of the invention is administered to the subject in combination with at least one further pharmaceutically active agent.

[0316] Preferably, the pharmaceutically active agent is an antibiotic.

[0317] The antibiotic may be a p-lactam (such as a penicillin, cephalosporin, carbapenem, monobactam), beta-lactamase inhibitor, aminoglycoside, fluoroquinolone, tetracycline or polymyxin. The antibiotic may be chloramphenicol, rifampicin, or colistin (polymyxin E).

[0318] In some embodiments, the antibiotic is a p-lactam. In some embodiments, the antibiotic is a carbapenem.

[0319] In some embodiments, the antibiotic is a polymyxin. In some embodiments, the antibiotic is colistin.

[0320] Thus, in some embodiments, the methods of treatment and / or prevention described herein may further comprise administering an antibiotic to the subject.

[0321] Suitably, “in combination” may mean that the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and the further pharmaceutically active agent are administered to the subject in a simultaneous, combined, sequential or separate manner.

[0322] By “simultaneous”, it is to be understood that the two agents are administered concurrently, whereas the term “combined” is used to mean they are administered, if not simultaneously, then “sequentially” within a time frame that they both are available to act therapeutically within the same time frame. Thus, administration “sequentially” may permit one agent to be administered within 5 minutes, 10 minutes or a matter of hours after the other provided the circulatory half-life of the first administered agent is such that they are both concurrently present in therapeutically effective amounts. The time delay between administration of the components will vary depending on the exact nature of the components, the interaction therebetween, and their respective half-lives. Suitably, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and further pharmaceutically active agent are administered in a simultaneous, combined, or sequential manner to a subject.

[0323] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and the further pharmaceutically active agent (e.g. antibiotic) are administered to the subject simultaneously.

[0324] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and the further pharmaceutically active agent (e.g. antibiotic) are administered to the subject in a combined or sequential manner.

[0325] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention is administered to the subject prior to administration of the further pharmaceutically active agent (e.g. antibiotic).

[0326] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention is administered to the subject after administration of the further pharmaceutically active agent (e.g. antibiotic).

[0327] In contrast to “combined” or “sequential”, “separate” may be understood as meaning that the gap between administering one agent and the other agent is significant, i.e. the first administered agent may no longer be present in the bloodstream in a therapeutically effective amount when the second agent is administered.

[0328] Suitably, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and further pharmaceutically active agent are administered in a separate manner to a subject.

[0329] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention and the further pharmaceutically active agent (e.g. antibiotic) are administered to the subject separately.

[0330] In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention is administered to the subject prior to administration of the further pharmaceutically active agent (e.g. antibiotic). In some embodiments, the immunogenic polypeptide, polynucleotide, vector, immunogenic composition, vaccine, inhibitor, antibody or composition of the invention is administered to the subject after administration of the further pharmaceutically active agent (e.g. antibiotic).

[0331] SUBJECT

[0332] The subject may be a human or non-human animal.

[0333] Examples of non-human animals include vertebrates, for example mammals, such as non- human primates (particularly higher primates).

[0334] Preferably, the subject is a human. The subject may be any age, gender or ethnicity.

[0335] The subject may be suffering from, or at risk of, A baumannii infection.

[0336] A. baumannii is a Gram-negative, opportunistic bacterial pathogen primarily associated with hospital-acquired (nosocomial) infections, and which exhibits extensive resistance to most first-line antibiotics.

[0337] In some embodiments, the subject is hospitalised and / or immunocompromised.

[0338] In some embodiments, the subject is infected with A. baumannii.

[0339] In some embodiments, the subject is infected with antibiotic resistant A. baumannii.

[0340] In some embodiments, the subject is infected with A. baumannii that is resistant to one or more beta-lactam, beta-lactamase inhibitor, aminoglycoside, fluoroquinolone, tetracycline and / or polymyxin antibiotic.

[0341] In some embodiments, the subject is infected with a beta-lactam resistant A. baumannii. In some embodiments, the subject is infected with a carbapenam resistant A. baumannii.

[0342] In some embodiments, the subject is infected with a polymyxin resistant A. baumannii.

[0343] In some embodiments, the subject is infected with chloramphenicol, rifampicin, and / or colistin resistant A. baumannii.

[0344] In some embodiments, the subject is infected with a colistin resistant A. baumannii.

[0345] In some embodiments, the subject is infected with a multidrug resistant (MDR) A. baumannii.

[0346] In some embodiments, the subject is infected with a pandrug resistant (PDR) A. baumannii. The subject may be infected with, or at risk of infection from, one or more strains of A baumannii. The subject may be infected with any strain(s) of A. baumannii.

[0347] In some embodiments, the subject is infected with one or more A. baumannii strains having a KL type of KL47, KL10, KL52, KL6, KL25, KL2, KL3, KL49, KL24, KL14 and / or KL28.

[0348] In some embodiments, the subject is infected with one or more A. baumannii strains having a KL type of KL47, KL10, KL52, KL6, and / or KL25.

[0349] In some embodiments, the subject is infected with one or more A. baumannii strains selected from the group consisting of AB5075, AB15, AB98, AB1615-09, ABMYH-1033, AB1 , AB55, ABAPSP-515, AB56, AB3879, NPRC-AB20, BAL_084, and AB1492-09.

[0350] In some embodiments, the subject is infected with one or more A. baumannii strains selected from the group consisting of AB55, NPRC-AB20 and AB1615-09.

[0351] In some embodiments, the subject is infected with one or more A. baumannii strains selected from the group consisting of AB3879, AB1492-09 and AB1615-09.

[0352] In some embodiments, the subject is infected with one or more A. baumannii strains selected from the group consisting of ABMYH-1033, AB1 , AB55, ABAPSP-515, and AB3879.

[0353] It will be understood that the invention is not limited by the exemplary strains and / or KL types disclosed herein, for example due to the conserved nature of the immunogenic polypeptides disclosed herein.

[0354] DOSAGE

[0355] The skilled person can readily determine an appropriate dose of one of the agents of the invention to administer to a subject without undue experimentation. Typically, a physician will determine the actual dosage which will be most suitable for an individual patient and it will depend on a variety of factors including the activity of the specific agent employed, the metabolic stability and length of action of that agent, the age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drug combination, the severity of the particular condition, and the individual undergoing therapy. There can of course be individual instances where higher or lower dosage ranges are merited, and such are within the scope of the invention.

[0356] The skilled person appreciates, for example, that route of delivery (e.g. oral vs. intravenous vs. subcutaneous etc.) may impact the required dosage (and vice versa). For example, where particularly high concentrations of an agent within a particular site or location are desired, focussed delivery may be preferred. Other factors to be considered when optimizing routes and / or dosing schedule for a given therapeutic regimen may include, for example, the disease being treated (e.g. type or stage etc.), the clinical condition of a subject (e.g. age, overall health etc.), the presence or absence of combination therapy, and other factors known to medical practitioners.

[0357] The dosage is such that it is sufficient to improve symptoms or markers of the disease - as described herein.

[0358] The invention will now be further described by way of Examples, which are meant to serve to assist one of ordinary skill in the art in carrying out the invention and are not intended in any way to limit the scope of the invention.

[0359] EXAMPLES

[0360] Example 1 - Selection of proteins for A. ba / mann / 7' protein microarray

[0361] Using genome data from 220 A. baumannii strains, including 191 clinical Thai isolates, an 868 A. baumannii protein microarray was constructed for immunogenicity studies. Proteins for the microarray were selected according to their potential suitability as an antibody therapy target due to (i) a high degree of conservation between A. baumannii strains causing infections, (ii) predicted surface location, and / or (iii) higher levels of expression of the corresponding gene during culture in vitro in human serum as a marker for likely expression during human infection. For the selected proteins successfully expressed and included in the microarray, the predicted localisation for 649 (67.7%) was the bacterial envelope (periplasm, inner or outer membrane), 24 (2.5%) extracellular, 165 (17.2%) cytoplasmic, and unknown for 120 (12.5%). For proteins included in the microarray the corresponding gene was present in a mean of 215.4 (97.9%) (range 114-220) of the 220 A. baumannii genomes when analysed using a 95% DNA conservation level. The mean rank of expression of the corresponding gene in ex vivo blood for the proteins included in the arrays was 553.08 counts per million (CPM) (strain AB1615- 09), 501.46 CPM (strain AB1), and 495.75 CPM (strain NPRC-AB20). The predicted localisation and expression in serum characteristics of the 868 proteins included in the microarray are summarised in Figure 1.

[0362] Example 2 - Identification of conserved immunogenic A. baumannii proteins

[0363] To identify A. baumannii proteins capable of inducing immune responses in mice, the protein microarray was probed with sera obtained from mice one month after non-lethal infection with A. baumannii. To ensure a broad range of antigens were identified, mice were infected three times with a single strain of A. baumannii (single strain sera, obtained for five Thai clinical strains) or with three different strains (multi-strain sera, two combinations). Whole cell ELISAs against both an encapsulated (AB5075 WT) and an unencapsulated (AB5075wza) A. baumannii strain demonstrated significant IgG recognition by sera from infected mice (Figure 2A). When used to probe the microarray, each infecting strain I combination of strains showed significant IgG responses to between 11 and 35 protein antigens, with shared recognition of many antigens (e.g. ABUW_2730 and ABUW_1741 (BamA)) (Figure 2B & 2C). Infection with mixed A. baumannii strains resulted in an almost four-fold increase in the mean number of antigens recognised by IgG compared to sera from mice infected with a single strain (Figure 2C), with principal component analysis showing clear separation in the immune response to A. baumannii proteins in sera obtained from the two mixed strain infection combinations (Figure 2D). Overall, a total of 66 protein antigens induced IgG in at least one mouse. Figure 2E shows the mean MFI for IgG binding for all serum samples for the top recognised antigens, and each antigen is described in Table 2. From these data, Ag1 , Ag2, Ag3, Ag4, Ag5, Ag7, Ag9, Ag10, and Ag11 (BamA) were selected for further investigation. Except Ag4 and Ag9, all the selected antigens are predicted outer membrane proteins. The selected antigens are 70 to 100% conserved amongst 220 A. baumannii strains, and seven had increased expression of the corresponding gene during culture in human blood compared to growth in broth. BamA has been described previously (Vieira de Araujo et al. 2021 , Microbes Infect 23, 104801).

[0364] Table 2. Summary of the data for the A baumannii proteins identified as potential targets for an antibody therapy.

[0365] 10M = outer membrane.

[0366] Conservation at amino acid level amongst 220 genome sequenced clinical A. baumannii isolates.

[0367] Table 3. Immune recognition and protection in vivo

[0368] 1Determined from immunological assays including ELISAs, IgG opsonisation, C3b / iC3b deposition, neutrophil phagocytosis, and MAC deposition. determined from mouse model of A. baumannii sepsis with clinical strain AB3879. Example 3 - IgG to the selected target antigens recognised clinical A. baumannii strains

[0369] Polyclonal rabbit antibodies were raised against each of the selected protein antigens for use in in vitro and in vivo experiments. In Western blots against purified protein (Figure 3A) the polyclonal rabbit antibodies generally recognised bands corresponding to the predicted protein sizes for each antigen. ELISAs against nine Thai clinical AMR A. baumannii isolates representing several seguence (MLST) types and KL classes (strains listed in Table 4) demonstrated significant recognition of each strain by most antibodies (Figure 3B). The strength of recognition varied with antigen target and between strains (e.g. compare results for antibody to Ag9 and Ag10 across the AB3879, AB98 and AB1615-09). a-Ag1 showed the highest levels of IgG recognition for the majority of strains (6 out of 9). Using antibody to antigens 1 and 11 , fluorescent microscopy showed significant surface recognition of both the encapsulated laboratory A baumannii strain AB5075 and the isogenic unencapsulated AB5075wzastrain (Figure 3C). a-Ag7 demonstrated more focal binding than a-Ag1 and a-Ag11 , with a marked increase in intensity of fluorescent labelling to the unencapsulated strain compared to the encapsulated strain.

[0370] Table 4. Acinetobacter baumannii strains

[0371] Example 4 - Rabbit antibodies to selected target antigens protected mice against A. baumannii sepsis

[0372] A mouse model of passive immunisation followed by septicaemic challenge with the clinical AMR strain AB3879 was used to assess the protective efficacy of polyclonal rabbit antibody to the selected antigens. Treatment with a-Ag2, a-Ag9, or a-Ag10 failed to cause statistically significant reductions in target organ CFU compared to PBS treated mice (Figures 4B, 4D, 4G, & 4H, respectively). In contrast, passive immunisation with a-Ag1 , a-Ag3, a-Ag5, a-Ag7, or a-Ag11 (BamA) significantly reduced bacterial CFU recovered from one or more target organs (kidney or spleen) by up to 3 log (Figures 4A, 4C, 4E, 4F, & 4I, respectively). Combining passive immunisation with a-Ag1 and a-Ag11 reduced target organ CFU compared to vaccination with either antibody alone (Figure 4J). Hence, a-Ag1 , a-Ag3, a-Ag5, a-Ag7, and a-Ag11 were selected for further investigation.

[0373] In a further experiment, 6 mice per group were injected intraperitoneally with 100 ul PBS or 100 ul purified rabbit IgG a-Ag4 @ 1 mg / ml (i.e. 100 ug each), followed 4h later with intraperitoneal injections of 7.09E+06 CFU / mouse of strain AB3879 + 5% mucin. Mice were culled ~20 h post infection and the number of CFUs determined in target organs. These data indicate that passive immunisation with rabbit IgG to Ag4 is protective in a mouse model of A. baumannii septicaemia (Figure 12).

[0374] Example 5 - Antibody to selected antigens promoted immune recognition and opsonophagocytosis of clinical A. baumannii isolates

[0375] To assess the potential conseguences of antibody recognition of the selected antigens, opsonisation with IgG and complement components C3b / iC3b, neutrophil phagocytosis, and complement membrane attack complex formation (MAC, C5b-8 / C5b-9) were assessed for the AB3879 and AB98 clinical A. baumannii strains using established flow cytometry assays. Antibody to all the selected antigens supported significant levels of opsonisation with IgG of AB3879 and / or AB98 (Figure 5A & B). After incubation in normal human serum (NHS), and as previously reported, A. baumannii strains AB3879 and AB98 varied in their susceptibility to opsonisation with C3b / iC3b, susceptibility to neutrophil phagocytosis, and degree of surface MAC formation (Figure 5C-H). Addition of antibody to Ag1 , Ag3 and Ag5 increased C3b / iC3b deposition against AB3879, and antibody to all five antigens increased C3b / iC3b deposition on the AB98 strain (Figure 5C & D). Conversely, a-Ag2, a-Ag9 and a-Ag10 which provided no protection against AB3879 sepsis in mice although they generally promoted IgG opsonisation of strains AB3879 and AB98 did not promote significant C3b / iC3b opsonisation in vitro (Figure 6). Complement-dependent neutrophil phagocytosis of strain AB3879 was improved by a-Ag5 and a-Ag7 (Figure 5E), and for strain AB98 (which was more susceptible to neutrophil phagocytosis than strain AB3879) by a-Ag3, a-Ag5 or a-Ag7 (Figure 5F). C5b-8 / C5b-9 formation on strain AB3879 was only promoted by a-Ag1 , whereas for strain AB98 a-Ag1 , a- Ag3, a-Ag5, or a-Ag7 all promoted C5b-8 / C5b-9 formation (Figure 5G & H). Overall, these data demonstrate that antibodies to the selected antigens bind to clinical A. baumannii strains and this can result in complement activation with opsonisation with C3b / iC3b, sometimes MAC formation, and neutrophil phagocytosis. However, the relationships between these immune effects was not always simply related to degree of IgG opsonisation for a given antibody I strain combination. Example 6 - Passive protection of mice by selected antibodies requires neutrophils and complement

[0376] To determine which phagocyte subset mediated protection from passive immunisation with rabbit antibody to our selected antigens in the AB3879 sepsis model, mouse infection experiments were repeated using a-Ag5 and a-Ag7 after depletion of tissue resident macrophages or neutrophils. When using spleen CFU as the readout, treating mice with intraperitoneal clodronate to deplete tissue macrophages (results in 86.2% SD 1.5% depletion of splenic macrophages) did not affect the protective effect of passive immunisation with a- Ag5 or a-Ag7 against A. baumannii strain AB3879 sepsis (Figure 7A). In contrast, treating mice with intraperitoneal a-Ly6G to deplete neutrophils (results in 99.5% SD 0.2% depletion of splenic neutrophils) prevented passive immunisation with a-Ag5 or a-Ag7 from protecting against A. baumannii strain AB3879 sepsis (Figure 7A). These results demonstrate that neutrophils were the main phagocyte mediating antibody dependent immunity against systemic infection in the sepsis model. To assess whether complement was also required for antibody-mediated protection, passive protection experiments were repeated after treating mice with cobra venom factor (CVF) to deplete serum complement (confirmed by loss of C3b / iC3b deposition on unencapsulated A. baumannii strain AB5075wzain serum obtained from CVF treated mice). CVF treatment also abrogated the full protective effect of passive immunisation with a-Ag5 and a-Ag7 against A. baumannii strain AB3879 when assessed using spleen CFU (Figure 7A), confirming complement is required for protection against systemic infection mediated by a-5 and a-7. However, the effects of depletion of macrophages, neutrophils or C3b / iC3b on lung CFU in the sepsis model were more complex. Although as shown for the spleen CFU data the protective effects of a-Ag7 for lung CFU were dependent on neutrophils and complement but not macrophages, protection against lung infection by a- Ag5 was dependent on both macrophages or neutrophils with only partial dependence on complement (Figure 7B).

[0377] Example 7 - Antibody to our target antigens increases A. baumannii sensitivity to antibiotics

[0378] To explore whether combining antibiotic treatment with antibody could be synergistic when treating microbial infections, the colistin resistant A. baumannii strain AB3879 (MIC > 4 pg / ml) was cultured in broth supplemented with NHS, with and without colistin and / or a-Ag1 , a-Ag11 (BamA) and a-Ag9. Addition of NHS inhibited A. baumannii growth and this effect was lost when NHS was heat treated to inactivate complement and MAC activity (Figure 8). Addition of a sub-MIC concentration of colistin (1 pg / ml) slightly impaired growth of AB3879 in NHS. Addition of a-Ag9 or a-Ag11 with NHS also slightly inhibited growth compared to addition of colistin alone. However, addition of both of these antibodies with colistin and NHS significantly inhibited growth of strain AB3879, demonstrating a potentially additive or synergistic effect of this antibody / antibiotic combination (Figure 8A & 8B). Addition of a-Ag1 to colistin and NHS did not affect the growth of this strain (Figure 8C).

[0379] Example 8 - Identifying antibody targets in Ac / 'netobacter Infection

[0380] A study was performed analysing 51 patients with confirmed Acinetobacter infections (ACB), 53 healthy controls, and 16 patients infected with other bacterial species. IgG antibody recognition profiles of proteins in plasma samples from these study groups identified that ABUW_0293 (PilP - SEQ ID NO: 33) exhibited a significantly higher recognition rate (47.7%) in the ACB group, suggesting a potentially Acinetobacter-spectfic antibody response.

[0381] Figure 9a depicts the plasma IgG levels against ABUW_0293 in Ac / netobacter-infected patients (ACB) during the first week of admission, healthy controls (HC) and other bacterial infected patients (OTH). ABUW_0293 showed significantly higher plasma IgG recognition in the ACB group compared to healthy controls, suggesting that ABUW_0293 may represent a specific target during Acinetobacter infection.

[0382] To assess the temporal dynamics of the IgG antibody response, paired plasma samples from 16 Ac / netobacter-infected patients collected at the first week of admission (Wk 0) and two weeks after admission (Wk 2). In 12 out of 16 (75%) patients, IgG recognition over the two- week period (Figure 9b).

[0383] Figure 10 shows rabbit polyclonal a-Ag13 (ABUW_0293) IgG recognition of clinical A. baumannii isolates representing several K locus capsule types (KL) and sequence types (ST), and IgG recognition of purified protein antigen.

[0384] Figure 11 shows passive immunisation with rabbit IgG to Ag13 (ABUW_0293) in a mouse model of A. baumannii infection in which mice were passively immunised by intraperitoneal inoculation of 100 pg rabbit polyclonal IgG or PBS 4 h before intraperitoneal inoculation with 3-6 x 106CFU / mouse of A. baumannii strain AB3879 suspended in PBS with 5% porcine mucin.

[0385] NUMBERED PARAGRAPHS

[0386] Various preferred features and embodiments of the present invention will now be described with reference to the following numbered paragraphs.

[0387] 1. An Acinetobacter baumannii immunogenic polypeptide comprising SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22, SEQ ID NO: 2, SEQ ID NO: 7, SEQ ID NO: 10,

[0388] SEQ ID NO: 11 , SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15,

[0389] SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 20,

[0390] SEQ ID NO: 21 , SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 26,

[0391] SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31 or SEQ I D NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0392] 2. The A baumannii immunogenic polypeptide according to paragraph 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 , SEQ ID NO: 3, SEQ ID NO: 9, SEQ ID NO: 22 or SEQ ID NO: 33or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0393] 3. The A. baumannii immunogenic polypeptide according to paragraph 2, wherein the immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32, SEQ ID NO: 1 or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0394] 4. The A. baumannii immunogenic polypeptide according to paragraph 3, wherein the immunogenic polypeptide comprises SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 32 or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0395] 5. The A. baumannii immunogenic polypeptide according to paragraph 4, wherein the immunogenic polypeptide comprises SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ I D NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0396] 6. The A. baumannii immunogenic polypeptide according to paragraph 5, wherein the immunogenic polypeptide comprises SEQ ID NO: 6, or SEQ ID NO: 8, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0397] 7. The A. baumannii immunogenic polypeptide according to paragraph 6, wherein the immunogenic polypeptide comprises SEQ ID NO: 6 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof. 8. The A baumannii immunogenic polypeptide according to paragraph 6, wherein the immunogenic polypeptide comprises SEQ ID NO: 8, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0398] 9. The A. baumannii immunogenic polypeptide according to paragraph 5, wherein the immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0399] 10. The A. baumannii immunogenic polypeptide according to paragraph 5, wherein the immunogenic polypeptide comprises SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

[0400] 11. A polynucleotide encoding one or more A. baumannii immunogenic polypeptides according to paragraph 1.

[0401] 12. A vector comprising one or more polynucleotides according to paragraph 11.

[0402] 13. An inhibitor which is capable of binding to an A. baumannii immunogenic polypeptide according to paragraph 1.

[0403] 14. The inhibitor according to paragraph 13, wherein the inhibitor is an antibody.

[0404] 15. An immunogenic composition comprising one or more A. baumannii immunogenic polypeptides according to paragraph 1.

[0405] 16. An immunogenic composition comprising one or more polynucleotides as defined in paragraph 11, or vectors as defined in paragraph 12.

[0406] 17. A composition comprising one or more inhibitors according to paragraph 13 or paragraph 14, optionally wherein the composition further comprises a pharmaceutically acceptable carrier, diluent or excipient.

[0407] 18. A vaccine comprising one or more A. baumannii immunogenic polypeptides as defined in paragraph 1.

[0408] 19. A vaccine comprising a polynucleotide as defined in paragraph 11 or a vector as defined in paragraph 12.

[0409] 20. A method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an A. baumannii immunogenic polypeptide according to any one of paragraphs 1 to 10, a polynucleotide according to paragraph 11 , a vector according to paragraph 12, an immunogenic composition according to paragraph 15 or paragraph 16, or a vaccine according to paragraph 18 or paragraph 19. A method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an inhibitor according to paragraph 13 or paragraph 14, or a composition according to paragraph 17. The method according to paragraph 20 or paragraph 21 , wherein the method further comprises administering an antibiotic to the subject. A method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an A. baumannii immunogenic polypeptide according to any one of paragraphs 1 to 10, a polynucleotide according to paragraph 11 , a vector according to paragraph 12, an immunogenic composition according to paragraph 15 or paragraph 16, or a vaccine according to paragraph 18 or paragraph 19. A method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an inhibitor according to paragraph 13 or paragraph 14, or a composition according to paragraph 17. The method according to paragraph 23 or paragraph 24, wherein the method further comprises administering an antibiotic to the subject. An A. baumannii immunogenic polypeptide according to any one of paragraphs 1 to 10, a polynucleotide according to paragraph 11 , a vector according to paragraph 12, an immunogenic composition according to paragraph 15 or paragraph 16, or a vaccine according to paragraph 18 or paragraph 19, for use in a method of treating or preventing an A. baumannii infection in a subject. An inhibitor according to paragraph 13 or paragraph 14, or a composition according to paragraph 17, for use in a method of treating or preventing an A. baumannii infection in a subject. The A. baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to paragraph 26, or the inhibitor or composition for use according to paragraph 27, wherein the method further comprises administering an antibiotic to the subject. The method according to any one of paragraphs 20 to 25, the A baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to paragraph 26 or paragraph 28, or the inhibitor or composition for use according to paragraph 27 or paragraph 28, wherein the subject is infected with an antibiotic resistant A. baumannii. The method according to any one of paragraphs 20 to 25, the A. baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to any one of paragraphs 26 or 28-29, or the inhibitor or composition for use according to any one of paragraphs 27-29, wherein the subject is infected with a colistin resistant A. baumannii. The method according to any one of paragraphs 20 to 25, the A. baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to any one of paragraphs 26 or 28-30, or the inhibitor or composition for use according to any one of paragraphs 27-30, wherein the subject is infected with a multidrug resistant (MDR) A. baumannii. The method according to any one of paragraphs 20 to 25, the A. baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to any one of paragraphs 26 or 28-31 , or the inhibitor or composition for use according to any one of paragraphs 27-31 , wherein the subject is infected with an A. baumannii strain selected from AB15, AB98, AB1615-09, ABMYH- 1033, AB1 , AB55, ABAPSP-515, AB56, AB3879, NPRC-AB20, BAL_084, and AB1492-09.

Claims

1. CLAIMS1. An Acinetobacter baumannii immunogenic polypeptide comprising SEQ ID NO: 8, SEQ ID NO: 6, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 9, SEQ ID NO: 32 or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

2. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 8, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 9, or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

3. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 8, SEQ ID NO: 6, or SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

4. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 8 or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

5. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 6, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

6. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 4, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

7. The A. baumannii immunogenic polypeptide according to claim 1 , wherein the immunogenic polypeptide comprises SEQ ID NO: 33, or a sequence having at least 70% identity thereto, or an immunogenic fragment thereof.

8. A polynucleotide encoding one or more A. baumannii immunogenic polypeptides according to any of claims 1 to 7.

9. A vector comprising one or more polynucleotides according to claim 8.

10. An inhibitor which is capable of binding to an A. baumannii immunogenic polypeptide according to any of claims 1 to 7, preferably wherein the inhibitor is an antibody.

11. An immunogenic composition comprising one or more A. baumannii immunogenic polypeptides according to any of claims 1 to 7.

12. An immunogenic composition comprising one or more polynucleotides as defined in claim 8, or vectors as defined in claim 9.

13. A composition comprising one or more inhibitors according to claim 10, optionally wherein the composition further comprises a pharmaceutically acceptable carrier, diluent or excipient.

14. A vaccine comprising one or more A. baumannii immunogenic polypeptides as defined in any of claims 1 to 715. A vaccine comprising a polynucleotide as defined in claim 8 or a vector as defined in claim 9.

16. A method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an A. baumannii immunogenic polypeptide according to any one of claims 1 to 7, a polynucleotide according to claim 8, a vector according to claim 9, an immunogenic composition according to claim 11 or claim 12, or a vaccine according to claim 14 or claim 15.

17. A method of treating or preventing an A. baumannii infection in a subject comprising administering to the subject an inhibitor according to claim 10, or a composition according to claim 13.

18. A method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an A. baumannii immunogenic polypeptide according to any one of claims 1 to 7, a polynucleotide according to claim 8, a vector according to claim 9, an immunogenic composition according to claim 11 or claim 12, or a vaccine according to claim 14 or claim 15.

19. A method of enhancing the susceptibility of A. baumannii to antibiotics, comprising administering to a subject infected with A. baumannii an inhibitor according to claim 10, or a composition according to claim 13.

20. An A. baumannii immunogenic polypeptide according to any one of claims 1 to 7, a polynucleotide according to claim 8, a vector according to claim 9, an immunogenic composition according to claim 11 or claim 12, or a vaccine according to claim 14 or claim 15, for use in a method of treating or preventing an A. baumannii infection in a subject.

21. An inhibitor according to claim 10, or a composition according to claim 14, for use in a method of treating or preventing an A. baumannii infection in a subject.

22. The method according to any one of claims 16 to 19, the A baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to claim 20, or the inhibitor or composition for use according to claim 21 , wherein the method further comprises administering an antibiotic to the subject.

23. The method according to any one of claims 16 to 19 or 22, the A. baumannii immunogenic polypeptide, polynucleotide, vector, immunogenic composition, or vaccine for use according to claim 20 or claim 22, or the inhibitor or composition for use according to claim 21 or claim 22, wherein the subject is infected with an antibiotic resistant A. baumannii, optionally wherein the subject is infected with a multidrug resistant (MDR) A. baumannii.