Effect of sequence variation in meningococcal PorA outer membrane protein on the effectiveness of a hexavalent PorA outer membrane vesicle vaccine

Though meningococcal serogroup C conjugate vaccines have been introduced into the UK infant immunisation schedule, there is currently no vaccine solution for serogroup B disease. PorA outer membrane protein (OMP) is a potential serogroup B vaccine candidate. A hexavalent PorA outer membrane vesicle (OMV) vaccine has been evaluated in phase I and II trials with promising results. This vaccine contains six different PorA OMPs each representing a different serosubtype. However, considerable sequence variation occurs in the variable regions (VRs) encoding these serosubtypes. By using recombinant P1.5,10 PorA variants we have demonstrated that the killing of this particular serosubtype combination was due mainly to the induction of antibody to the VR2 (P1.10) epitope region, and that after three or four doses of vaccine there was a significant reduction in the killing of variants P1.10a (three doses, p<0.0001; four doses, p = 0.003) and P1.10f (three doses, p<0.0001; four doses, p = 0.002), as compared to responses to the P1.10 strain, when the P1.10 serosubtype was used as the immunogen. Since large numbers of serosubtype variants are known to exist, this finding may have implications for the use of PorA as a meningococcal serogroup B vaccine.     

Development and characterisation of outer membrane vesicle vaccines against serogroup A Neisseria meningitidis

Neisseria meningitidis bacteria of serogroup A are causing recurring meningitis epidemics on the African continent. An outer membrane vesicle (OMV) vaccine against serogroup A meningococci made from a subgroup III serogroup A meningococcal strain was previously shown to induce antibodies with serum bactericidal activity (SBA) in mice. We have here further investigated the properties of OMV vaccines made from five different subgroup III serogroup A meningococcal strains grown in a synthetic medium with low iron content. In addition to the major outer membrane proteins (PorA, PorB, RmpM, Opa and OpcA), small amounts of the NadA, TdfH, Omp85, FetA, FbpA and NspA outer membrane proteins, as well as lipooligosaccharides, were detected in the vaccines. The OMV vaccines were used to immunise mice. Anti-meningococcal IgG antibodies in the mouse sera were analysed by immunoblotting and by enzyme-linked immunosorbent assay against OMVs, and against live meningococcal cells in SBA and a flow-cytometric assay. The vaccines induced antibodies with high SBA and opsonophagocytic activity. The strongest IgG responses were directed against PorA. Significant SBA responses were also observed against a subgroup III strain, which did not express PorA, whereas no SBA was observed against a clone IV-1 serogroup A strain. An OMV vaccine from serogroup A meningococci may be an alternative to polysaccharide and conjugate polysaccharide vaccines for Africa.     

Immunogenicity and safety of a hexavalent meningococcal outer-membrane-vesicle vaccine in children of 2-3 and 7-8 years of age

To study the reactogenicity and immunogenicity of a hexavalent meningococcal outer-membrane-vesicle vaccine (OMV), two different dosages of this vaccine (7.5 and 15 microg of individual PorA proteins) consisting of vesicles expressing class 1 outer-membrane proteins (OMPs) of subtypes P1.7,16; P1.5,2; P1.19,15 and P1.5(c), 10; P1.12,13; P1.7(h),4 were administered to a group of 7-8 year (n=165) and a group of 2-3 year old children (n=172). Control groups of children with similar ages were vaccinated against hepatitis B. All participants received three injections. Pre- and postimmunisation sera were tested for bactericidal antibodies against six isogenic meningococcal vaccine strains expressing different PorA proteins. Antibody titres against OMP of the two different vesicles (PL16215 and PL10124) were measured by ELISA. The meningococcal hexavalent OMV vaccine was well tolerated. No statistically significant differences were seen between the high and low dose of hexavalent meningococcal OMV vaccine. The percentage of children showing a fourfold increase of bactericidal antibody titres against the specific serosubtype varied in toddlers from 28 to 98% and in older children from 16 to 100%. Both ELISA antibody titres and bactericidal activity showed the highest level in the youngest age-group.     

Immunogenicity and bactericidal activity in mice of an outer membrane protein vesicle vaccine against Neisseria meningitidis serogroup A disease

Serogroup A Neisseria meningitidis organisms of the subgroup III have caused epidemics of meningitis in sub-Saharan Africa since their introduction into the continent in 1987. The population structure of these bacteria is basically clonal, and these meningococci are strikingly similar in their major outer membrane antigens PorA and PorB. Protein-based vaccines might be an alternative to prevent epidemics caused by these meningococci; thus, we developed an outer membrane vesicle (OMV) vaccine from a serogroup A meningococcal strain of subgroup III. The serogroup A OMV vaccine was highly immunogenic in mice and elicited significant bactericidal activity towards several other serogroup A meningococci of subgroup III. The IgG antibodies generated were in immunoblot shown to be mainly directed towards the PorA outer membrane protein. The results presented demonstrate the potential of an OMV vaccine as an optional strategy to protect against meningococcal disease caused by serogroup A in Africa.     

Effect of sequence variation in meningococcal PorA outer membrane protein on the effectiveness of a hexavalent PorA outer membrane vesicle vaccine in toddlers and school children

Though meningococcal conjugate vaccines are effective against serogroup C, there is currently no vaccine solution for serogroup B disease. PorA outer membrane protein (OMP) is a potential serogroup B vaccine candidate. A hexavalent PorA outer membrane vesicle (OMV) vaccine has been evaluated in phase I and II trials with promising results. However, considerable sequence variation occurs in the variable regions (VRs) encoding these serosubtypes. By using five wild type P1.19,15 variant strains we examined the serum bactericidal antibody (SBA) titres from sera collected from toddlers and school children pre- and post-vaccination. The numbers of subjects with SBA titres of <4, 4 and > or = 8 varied greatly between the different strains. This was also reflected when > or = 4-fold rises in SBA titres were examined. This finding in sera from toddlers and school children may have implications for PorA based vaccines.     

Immunogenicity of various presentation forms of PorA outer membrane protein of Neisseria meningitidis in mice.

In this study we compare different vaccine formulations containing meningococcal PorA outer membrane protein; purified PorA, outer membrane vesicles (OMV) and immune-stimulating complexes (iscom). Bactericidal antibodies could be generated by the OMV and iscom formulation but not with purified PorA using either A1PO4 or Quil-A as adjuvant. OMV and iscom formulations revealed similar immunogenicity when tested in a dose response manner, with respect to bactericidal as well as OMV-binding antibodies. The anti-OMV IgG subclass response induced by PorA in OMV formulation was found in all subclasses IgG1, IgG2a, IgG2b, IgG3. OMP-iscoms induced very high IgG1 anti-OMV antibodies but almost no IgG3 response. Also, OMP-iscoms appeared to be a potent inducer of antibodies directed against linear peptides corresponding to surface exposed loops of PorA. In addition, iscoms as well as purified PorA with Quil-A as adjuvant (but not with A1PO4) induced high levels of antibodies against purified PorA. In summary, in addition to the OMV formulation, only iscoms containing PorA are able to generate an anamnestic and bactericidal antibody response.     

Epidemiology of pathogenic Neisseria meningitidis serogroup B serosubtypes in Malta: implications for introducing PorA based vaccines

OBJECTIVE: To describe the epidemiology of the serosubtypes of Neisseria meningitidis serogroup B (MenB) in the most densely populated area in Europe and to review the MenB Porin A (PorA) based outer membrane vesicle (OMV) vaccines that could provide the broadest protection. STUDY DESIGN AND SETTING: Active surveillance of invasive meningococcal disease in a population of 400,000 inhabitants in Malta from 1999 to 2006. Serogroup B isolates were serosubtyped and analysed by age and year. The suitability of OMV vaccines was then assessed. RESULTS: Laboratory confirmation of invasive meningococcal disease was obtained in 48% (79/163) of notified cases. Serogroup B caused the majority of invasive meningococcal disease (76%, 60/79) with the greatest disease burden occurring in 0-14-year-old children (73%, 44/60). MenC caused 14% (11/79) of cases. The most prevalent MenB serotype:serosubtype combination was B:4:P1.19,15 which constituted 59% (34/58) of all phenotypeable MenB isolates. The PorA epitopes P1.15 and P1.19, detected in 74% (43/58) of isolates, were significantly more prevalent than serosubtypes with other PorA epitopes (chi(2): 7.18, P<0.01). CONCLUSION: An assessment of the usefulness of a MenB OMV vaccine in Malta requires further research. The wild-type OMV vaccine developed by the Finlay Institute (FI) in Cuba could potentially be used to control an outbreak with a MenB P1.19,15 clone. A multivalent OMV vaccine would however be needed for broader protection against the endemic heterogenous MenB strains. A serogroup B vaccine incorporating more conserved proteins than PorA would be more suitable for comprehensive control of meningococcal B disease.     

Immunogenicity and safety of monovalent p1.7(h),4 meningococcal outer membrane vesicle vaccine in toddlers: comparison of two vaccination schedules and two vaccine formulations

The safety and immunogenicity of two PorA-based meningococcal outer membrane vesicle (OMV) vaccines against the P1.4 serosubtype adsorbed with AlPO(4) or Al(OH)(3) were studied in 134 toddlers. Vaccinations were given three times with an interval of 3-6 weeks or twice with an interval of 6-10 weeks. A vaccination was repeated after 20-40 weeks. Pre- and post-immunization sera were tested for bactericidal activity against an isogenic strain expressing P1.7(h), 4 PorA. Both meningococcal OMV vaccines were well tolerated. The percentage of children with a fourfold increase in bactericidal activity was 96% (AlPO(4)-adjuvated vaccine/2+1 schedule), 100% (AlPO(4)-adjuvated vaccine/3+1 schedule), 93% (Al(OH)(3)-adjuvated vaccine/2+1 schedule) and 97% (Al(OH)(3)-adjuvated vaccine/3+1 schedule). Adsorption with AlPO(4) makes the OMV vaccine more immunogenic than adsorption with Al(OH)(3). Bactericidal activity was highest after the 3+1 schedule, although the response shortly after the primary series was higher in the two-dose priming group.     

Human IgG subclass responses in relation to serum bactericidal and opsonic activities after immunization with three doses of the Norwegian serogroup B meningococcal outer membrane vesicle vaccine

Ten adult volunteers, with low prevaccination levels of serum IgG antibodies against meningococcal antigens (< 1 microg ml(-1)), received three doses of the Norwegian group B meningococcal outer membrane vesicle (OMV) vaccine intramuscularly at weeks 0, 6 and 46. Anti-OMV IgG subclass responses were measured and compared with serum bactericidal activity (SBA) and opsonic activity against the vaccine strain 44/76. All vaccinees showed an IgG1 antibody response after each vaccine dose. The vaccine-induced median serum IgG1 antibody levels were 16, 17 and 18 microg ml(-1) 2-6 weeks after the first, second and third dose, respectively. Three vaccinees showed a weak IgG3 response after the first dose, whereas 8 and 9 showed a response after the second (median = 10 microg ml(-1)) and third dose (median = 10 microg ml(-1)), respectively. Low levels of anti-OMV IgG2 antibodies were found, whilst specific IgG4 antibodies were only detected for one vaccinee. The vaccine induced at least a fourfold increase in SBA titre in 8 vaccinees after the first dose, in 9 vaccinees after 2 doses and in all vaccinees after 3 doses. A positive correlation was found between IgG1 subclass antibody levels and SBA (r = 0.62, P < 0.0001). Elevated opsonophagocytic activity, measured as respiratory burst (RB), was observed in all vaccinees after one vaccine dose and usually increased after 2 and 3 doses. A strong positive correlation was found between IgG1 antibody levels and RB (r = 0.76, P < 0.0001). In conclusion, we have shown that systemic meningococcal OMV vaccination in adult vaccinees mainly induced IgG1 antibodies which correlated with bactericidal and opsonic activity, but also a considerable amount of IgG3 antibodies, which, in contrast to the IgG1 response, was induced only after 2 or 3 vaccine doses and declined more rapidly.     

Immunogenicity and reactogenicity in UK infants of a novel meningococcal vesicle vaccine containing multiple class 1 (PorA) outer membrane proteins.

The development of effective vaccines against serogroup B meningococci is of great public health importance. We assessed a novel genetically engineered vaccine containing six meningococcal class 1 (PorA) outer membrane proteins representing 80% of prevalent strains in the UK. 103 infants were given the meningococcal vaccine at ages 2, 3 and 4 months with routine infant immunisations, with a fourth dose at 12-18 months. The vaccine was well tolerated. Three doses evoked good immune responses to two of six meningococcal strains expressing PorA proteins contained in the vaccine. Following a fourth dose, larger bactericidal responses to all six strains were observed, suggesting that the initial course had primed memory lymphocytes and revaccination stimulated a booster response. This hexavalent PorA meningococcal vaccine was safe and evoked encouraging immune responses in infants. Vaccines of this type warrant further development and evaluation.     

Immunogenicity studies with a genetically engineered hexavalent PorA and a wild-type meningococcal group B outer membrane vesicle vaccine in infant cynomolgus monkeys

The immunogenicity of two meningococcal outer membrane vesicle (OMV) vaccines, namely the Norwegian wild-type OMV vaccine and the Dutch hexavalent PorA OMV vaccine, were examined in infant cynomolgus monkeys. For the first time, a wild-type- and a recombinant OMV vaccine were compared. Furthermore, the induction of memory and the persistence of circulating antibodies were measured. The Norwegian vaccine contained all four classes of major outer membrane proteins (OMP) and wild-type L3/L8 lipopolysaccharide (LPS). The Dutch vaccine consisted for 90% of class 1 OMPs, had low expression of class 4 and 5 OMP, and GalE LPS. Three infant monkeys were immunised with a human dose at the age of 1.5, 2.5 and 4.5 months. Two monkeys of each group received a fourth dose at the age of 11 months. In ELISA, both OMV vaccines were immunogenic and induced booster responses, particularly after the fourth immunisation. The Norwegian vaccine mostly induced sero-subtype P1.7,16 specific serum bactericidal antibodies (SBA), although some other SBA were induced as well. The antibody responses against P1.7,16, induced by the Norwegian vaccine, were generally higher than for the Dutch vaccine. However, the Dutch vaccine induced PorA specific SBA against all six sero-subtypes included in the vaccine showing differences in the magnitude of SBA responses to the various PorAs.     

Deletion of major porins from meningococcal outer membrane vesicle vaccines enhances reactivity against heterologous serogroup B Neisseria meningitidis strains

Detergent-extracted detoxified outer membrane vesicle (dOMV) vaccines are effective at preventing invasive serogroup B meningococcal (MenB) disease caused by the homologous Neisseria meningitidis strain from which they are produced, but offer limited protection from heterologous strains. Differences in vaccine efficacy are partially due to strain-specific variations in the antigenic sequence types and expression levels of outer membrane proteins (OMPs), including the immunodominant OMP PorA. In this study, dOMV vaccines deficient in major OMPs, including PorA, PorB, and RmpM were isolated and used to immunize rabbits and mice. Serum samples were obtained from each animal and tested for antibody responses against five MenB strains. Immunization with wild type dOMVs elicited antibodies to major antigens including PorA, PorB, RmpM, and lipooligosaccharide (LOS), and demonstrated limited bactericidal activity against heterologous strains. In contrast, OMP-deficient dOMV vaccines elicited broadly cross-reactive bactericidal antibodies, with PorA/PorB-dual deficient dOMVs inducing antibodies exhibiting the greatest cross-reactivity. Enhanced killing of heterologous strains correlated with binding to unique protein bands in immunoblots, suggestive of improved immunogenicity of antigens under-represented in the wild type vaccine.     

A meningococcal NOMV-FHbp vaccine for Africa elicits broader serum bactericidal antibody responses against serogroup B and non-B strains than a licensed serogroup B vaccine

BackgroundMeningococcal epidemics in Sub-Sahara caused by serogroup A strains are controlled by a group A polysaccharide conjugate vaccine. Strains with serogroups C, W and X continue to cause epidemics. Protein antigens in licensed serogroup B vaccines are shared among serogroup B and non-B strains.PurposeCompare serum bactericidal antibody responses elicited by an investigational native outer membrane vesicle vaccine with over-expressed Factor H binding protein (NOMV-FHbp) and a licensed serogroup B vaccine (MenB-4C) against African serogroup A, B, C, W and X strains.MethodsHuman Factor H (FH) transgenic mice were immunized with NOMV-FHbp prepared from a mutant African meningococcal strain containing genetically attenuated endotoxin and a mutant sub-family B FHbp antigen with low FH binding, or with MenB-4C, which contains a recombinant sub-family B FHbp antigen that binds human FH, and three other antigens, NHba, NadA and PorA P1.4, capable of eliciting bactericidal antibody.ResultsThe NOMV-FHbp elicited serum bactericidal activity against 12 of 13 serogroup A, B, W or X strains from Africa, and four isogenic serogroup B mutants with sub-family B FHbp sequence variants. There was no activity against a serogroup B mutant with sub-family A FHbp, or two serogroup C isolates from a recent outbreak in Northern Nigeria, which were mismatched for both PorA and sub-family of the FHbp vaccine antigen. For MenB-4C, NHba was expressed by all 16 African isolates tested, FHbp sub-family B in 13, and NadA in five. However, MenB-4C elicited titers ≥1:10 against only one isolate, and against only two of four serogroup B mutant strains with sub-family B FHbp sequence variants.ConclusionsNOMV-FHbp has greater potential to confer serogroup-independent protection in Africa than the licensed MenB-4C vaccine. However, the NOMV-FHbp vaccine will require inclusion of sub-family A FHbp for coverage against recent serogroup C strains causing outbreaks in Northern Nigeria.     

Comparison of functional immune responses in humans after intranasal and intramuscular immunisations with outer membrane vesicle vaccines against group B meningococcal disease

A serogroup B meningococcal outer membrane vesicle (OMV) vaccine was delivered either intranasally or intramuscularly to 12 and 10 volunteers, respectively. The mucosal vaccine was given as four weekly doses followed by a fifth dose after 5 months; each dose consisted of OMVs equivalent to 250 microg of protein. The intramuscular (i.m.) vaccine, consisting of the same OMVs but adsorbed to Al(OH)(3), was administered as three doses each of 25 microg of protein, with 6 weeks interval between first and second doses and the third dose after 10 months. Both groups of vaccinees demonstrated significant immune responses when measured as specific IgG antibodies against live meningococci, as serum bactericidal activity (SBA) and as opsonophagocytic activity. Two weeks after the last dose, the anti-meningococcal IgG concentrations were significantly higher in the i.m. group (median IgG concentration: 43.1 microg/ml) than in the intranasal group (10.6 microg/ml) (P=0.001). The corresponding opsonophagocytic activity was 7.0 and 3.0 (median log(2) titre) (P=0.001), and the SBA was 5.0 and 2.0 (median log(2) titre) (P=0.005), for the i.m. and intranasal groups, respectively. The last immunisation induced an enhanced immune response in the i.m. group, whereas the intranasal group showed no significant booster response. Accordingly, affinity maturation of anti-OMV-specific IgG antibodies was seen only after i.m. vaccination. The IgG1 subclass dominated the responses in both groups, whereas the significant IgG3 responses observed in the i.m. group were absent in the intranasal group. Although the intranasal OMV vaccination schedule used here induced functional immune responses relevant to protection, an improved vaccine formulation and/or a modified mucosal immunisation regimen may be needed to achieve a systemic effect comparable to that seen after three doses of intramuscular vaccination.     

Expression of human CEACAM1 in transgenic mice limits the Opa-specific immune response against meningococcal outer membrane vesicles

Outer membrane vesicles (OMVs) have been extensively investigated as meningococcal vaccine candidates. Among their major components are the opacity (Opa) proteins, a family of surface-exposed outer membrane proteins important for bacterial adherence and entry into host cells. Many Opa-dependent interactions are mediated through the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family of receptors. Importantly, binding of Opa to CEACAM1 has been reported to suppress human CD4 T cell proliferation in vitro in response to OMV preparations. This raises the question whether OMV vaccines should contain Opa proteins at all. Until now it has been difficult to answer this question, as the proposed immunosuppressive effect was only demonstrated with human cells in vitro, while immunization experiments in mice are not informative because the Opa interaction is specific for human CEACAM1. In the present study we have used Opa+ and Opa− OMVs for immunization experiments in a human CEACAM1 transgenic mouse model. OMVs were prepared from a meningococcal strain H44/76 variant expressing the CEACAM1-binding OpaJ protein, and from an isogenic variant in which all opa genes have been inactivated. Both the CEACAM1 expressing transgenic mice and their congenic littermates lacking it were immunized twice with the OMV preparations, and the sera were analyzed for bactericidal activity and ELISA antibody titres. Total IgG antibodies against the OMVs were similar in both mouse strains. Yet the titres for IgG antibodies specific for purified OpaJ protein were significantly lower in the mice expressing human CEACAM1 than in the nontransgenic mice. No significant differences were found in bactericidal titres among the four groups. Overall, these data indicate that expression of human CEACAM1 confers a reduced Opa-specific antibody response in vivo without affecting the overall immune response against other OMV antigens.     

Avidity maturation following vaccination with a meningococcal recombinant hexavalent PorA OMV vaccine in UK infants

To date, there are no data assessing the utility of avidity indices as a surrogate marker for the induction of immunological memory following meningococcal serogroup B outer membrane vesicle (OMV) vaccination. We studied infants who had been immunized with three doses of a recombinant hexavalent PorA OMV vaccine at ages 2-4 months, together with a fourth dose at age 12-18 months. A control group had received a single dose of the same vaccine at age 12-18 months. As previously reported, serum bactericidal antibody (SBA) titres increased after each of the first three doses, with a significant increase observed from 6 months post third dose to 1 month post fourth dose. The geometric mean avidity indices (GMAI), against strain H44/76 OMVs, increased from 1 month post first dose to 1 month post third dose. Significant increases in GMAI were observed at 6 months post third dose and again following the fourth dose. At 32-42 months of age, though the SBA titres had returned to post first dose levels, the GMAI remained elevated. No increase in avidity was observed in the control group. Antibody avidity indices are useful laboratory markers for the priming of immunological memory following vaccination with meningococcal serogroup B OMV vaccines.     

A comparative evaluation of two investigational meningococcal ABCWY vaccine formulations: Results of a phase 2 randomized,controlled trial

BackgroundA meningococcal vaccine protective against all major disease-associated serogroups (A, B, C, W and Y) is an unmet public health need. In this phase 2 observer-blinded, randomized, controlled study, two investigational meningococcal ABCWY vaccine formulations were evaluated to assess their immunological noninferiority to a licensed quadrivalent meningococcal ACWY glycoconjugate vaccine (MenACWY-CRM) for serogroups ACWY and immunogenicity against serogroup B test strains, as well as for formulation selection based on a desirability index (DI). Each investigational MenABCWY formulation contained recombinant protein and outer membrane vesicle (OMV) components of a licensed serogroup B vaccine (4CMenB) combined with components of MenACWY-CRM.MethodsA total of 484 healthy 10–25 year-old participants were randomized to receive two doses, two months apart, of an investigational MenABCWY formulation that contained either a full or one-quarter dose of OMV, 4CMenB alone, or a Placebo followed by MenACWY-CRM. Immunogenicity against each of serogroups ACWY and four serogroup B test strains was assessed by serum bactericidal assay with human complement (hSBA). MenABCWY formulations were compared by a DI based on key immunogenicity and reactogenicity parameters.ResultsSeroresponse rates for serogroups ACWY were significantly higher after two doses of either MenABCWY formulation than after one dose of MenACWY-CRM: respectively, A: 90–92% vs. 73%; C: 93–95% vs. 63%; W: 80–84% vs. 65%; and Y: 90–92% vs. 75%. Prespecified noninferiority criteria were met. Both MenABCWY formulations induced substantial immune responses against serogroup B test strains, although 4CMenB responses were higher. Overall DIs for both MenABCWY formulations were similar. Reactogenicity profiles of the MenABCWY formulations were similar to each other and to that of 4CMenB. No vaccine-related serious adverse events were reported.ConclusionsBoth investigational MenABCWY formulations elicited robust immune responses against serogroups ACWY and serogroup B test strains, and had acceptable reactogenicity profiles, with no safety concerns identified.     

Improved immunogenicity of a H44/76 group B outer membrane vesicle vaccine with over-expressed genome-derived Neisserial antigen 1870

A broadly protective vaccine against meningococcal group B disease is not available. We previously reported that an outer membrane vesicle (OMV) vaccine containing over-expressed genome-derived antigen (GNA) 1870 elicited broader protective antibody responses than recombinant GNA1870 or conventional OMV vaccines prepared from a strain that naturally expresses low amounts of GNA1870. Certain wildtype strains such as H44/76 naturally express larger amounts of GNA1870 and, potentially, could be used to prepare an improved OMV vaccine without genetic over-expression of the antigen. We transformed H44/76 with a shuttle vector to over-express variant 1 (v.1) GNA1870 and compared the immunogenicity in mice of OMV vaccines prepared from wildtype H44/76 (v.1), the mutant, and a recombinant v.1 GNA1870 vaccine. Mice immunized with OMV with over-expressed GNA1870 developed broader serum bactericidal and/or greater C3 deposition activity on the surface of encapsulated strains of N. meningitidis than control mice immunized with the OMV vaccine prepared from the wildtype strain, or the rGNA1870 vaccine. When a panel of group B strains from patients in California was tested, sera from mice immunized with the OMV vaccine containing over-expressed GNA1870 were bactericidal against 100% of the v.1 strains. In contrast, only 20% of isolates that expressed subvariants of the v.1 GNA1870 protein were susceptible to bactericidal activity of antibodies elicited by the rGNA1870 or conventional OMV vaccines. Thus, even a modest increase in GNA1870 expression in a strain that naturally is a high producer of GNA1870 results in an OMV vaccine that elicits broader protection against meningococcal disease.     

Outer membrane vesicles (OMVs) and detoxified lipooligosaccharide (dLOS) obtained from Brazilian prevalent N. meningitidis serogroup B strains protect mice against homologous and heterologous meningococcal infection and septic shock

Neisseria meningitidis (N. meningitidis) is a serious bacterial pathogen that causes life-threatening invasive bacterial infections especially in children below 2 years of age, teenagers and young adults. We have investigated the protective potential of outer membrane vesicles (OMVs) and detoxified lipooligosaccharide (dLOS) obtained from Brazilian prevalent N. meningitidis serogroup B strains. Swiss mice were immunized with different combinations of OMV and dLOS from N. meningitidis serogroup B strains compared to a reference vaccine (VA-MENGOC-BC), Cuba). The OMVs + dLOS from Brazilian prevalent strains induced higher bactericidal antibody titers against homologous and heterologous target strains and stronger inhibition of thrombocytopenia as compared to the reference vaccine. When the challenge was performed with the B strain, all immunogens tested showed similar survival rates (80%) significantly higher than the control group. Bacterial clearance against the group B strain was comparable for animals immunized with the tested immunogen and the reference vaccine. Inclusion of dLOS from the B strain with the OMV, induced a similar clearance of C strain bacteria as compared to VA-MENGOC-BC. The immunogens, as well as the reference vaccine drastically inhibited increases in TNF-alpha and IL-6 plasma levels after challenge. In conclusion, the OMV/dLOS formulation obtained from Brazilian prevalent strains of N. meningitidis has a remarkable performance protecting mice against the lethal effects of meningococcal challenge showing a good potential as a vaccine and should be considered for clinical evaluation.     

Meningococcal vaccine development--from glycoconjugates against MenACWY to proteins against MenB--potential for broad protection against meningococcal disease

Novartis Vaccines has a long-standing research and development interest in the prevention of invasive meningococcal disease. From the initial licensure of the monovalent meningococcal C glycoconjugate vaccine, Menjugate(?), in response to the emergence of a virulent serogroup C ST-11 strain in the United Kingdom to the more recent development and licensure of a quadrivalent meningococcal ACWY glycoconjugate vaccine, Menveo(?), Novartis has a continuing commitment to the development of more effective tools for the control of meningococcal disease. Menveo is now licensed for use in adolescents and adults in over 50 countries and results from phase III studies have shown the vaccine to be well-tolerated and highly immunogenic in infants with vaccination beginning from 2 months of age. The 'holy grail' of meningococcal disease control is a broadly protective vaccine against serogroup B (MenB), preferably a vaccine that protects all age groups including infants. As the serogroup B capsule is poorly immunogenic, efforts over the past 40 years have focused on identifying conserved proteins expressed on the bacterial surface that elicit bactericidal antibodies. Novartis has approached this problem utilizing genomic tools to identify proteins meeting these criteria in a process now known as 'reverse vaccinology'[1]. This process has resulted in a novel multicomponent MenB vaccine (4CMenB) that consists of four major immunogenic components (three subcapsular MenB protein antigens plus outer membrane vesicles (OMVs) which themselves provide multiple subcapsular antigens, the immunodominant one being PorA). These all induce bactericidal antibodies against the antigens that are important in determining the survival, function, and virulence of the meningococci. Phase II studies of 4CMenB have been completed and have demonstrated that the vaccine is highly immunogenic against reference meningococcal strains selected to support licensure. Post-vaccination sera from clinical studies have also been tested against a diverse panel of serogroup B strains to support the development of the Meningococcal Antigen Typing System (MATS), a tool used to predict vaccine strain coverage [2] This overview is intended to give a broad summary of the key clinical data derived from the Menveo and 4CMenB clinical development programs.