Characterization of vaccine antigens of meningococcal serogroup W isolates from Ghana and Burkina Faso from 2003 to 2009.
ABSTRACT: Neisseria meningitidis is a major cause of bacterial meningitis and a considerable health problem in the 25 countries of the 'African Meningitis Belt' that extends from Senegal in West Africa to Ethiopia in the East. Approximately 80% of cases of meningococcal meningitis in Africa have been caused by strains belonging to capsular serogroup A. After the introduction of a serogroup A conjugate polysaccharide vaccine, MenAfriVac (™), that began in December 2010, the incidence of meningitis due to serogroup A has markedly declined in this region. Currently, serogroup W of N. meningitidis accounts for the majority of cases. Vaccines based on sub-capsular antigens, such as Generalized Modules for Membrane Antigens (GMMA), are under investigation for use in Africa. To analyse the antigenic properties of a serogroup W wave of colonisation and disease, we investigated the molecular diversity of the protein vaccine antigens PorA, Neisserial Adhesin A (NadA), Neisserial heparin-binding antigen (NHBA) and factor H binding protein (fHbp) of 31 invasive and carriage serogroup W isolates collected as part of a longitudinal study from Ghana and Burkina Faso between 2003 and 2009. We found that the isolates all expressed fHbp variant 2 ID 22 or 23, differing from each other by only one amino acid, and a single PorA subtype of P1.5,2. Of the isolates, 49% had a functional nhbA gene and 100% had the nadA allele 3, which contained the insertion sequence IS1301 in five isolates. Of the W isolates tested, 41% had high fHbp expression when compared with a reference serogroup B strain, known to be a high expresser of fHbp variant 2. Our results indicate that in this collection of serogroup W isolates, there is limited antigenic diversification over time of vaccine candidate outer membrane proteins (OMP), thus making them promising candidates for inclusion in a protein-based vaccine against meningococcal meningitis for Africa.
Project description:BACKGROUND: Serogroup B meningococcal (MenB) isolates currently account for approximately 90% of invasive meningococcal disease (IMD) in Greece with ST-162 clonal complex predominating. The potential of a multicomponent meningococcal B vaccine (4CMenB) recently licensed in Europe was investigated in order to find whether the aforementioned vaccine will cover the MenB strains circulating in Greece. A panel of 148 serogroup B invasive meningococcal strains was characterized by multilocus sequence typing (MLST) and PorA subtyping. Vaccine components were typed by sequencing for factor H-binding protein (fHbp), Neisserial Heparin Binding Antigen (NHBA) and Neisseria adhesin A (NadA). Their expression was explored by Meningococcal Antigen Typing System (MATS). RESULTS: Global strain coverage predicted by MATS was 89.2% (95% CI 63.5%-98.6%) with 44.6%, 38.5% and 6.1% of strains covered by one, two and three vaccine antigens respectively. NHBA was the antigen responsible for the highest coverage (78.4%), followed by fHbp (52.7%), PorA (8.1%) and NadA (0.7%). The coverage of the major genotypes did not differ significantly. The most prevalent MLST genotype was the ST-162 clonal complex , accounting for 44.6% of the strains in the panel and with a predicted coverage of 86.4%, mainly due to NHBA and fHbp. CONCLUSIONS: 4CMenB has the potential to protect against a significant proportion of Greek invasive MenB strains.
Project description:Meningococcal 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.Compare 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.Human 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.The 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.NOMV-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.
Project description:The meningococcal antigen typing system (MATS) sandwich enzyme-linked immunosorbent assay (ELISA) was designed to measure the immunologic cross-reactivity and quantity of antigens in target strains of a pathogen. It was first used to measure the factor H-binding protein (fHbp), neisserial adhesin A (NadA), and neisserial heparin-binding antigen (NHBA) content of serogroup B meningococcal (MenB) isolates relative to a reference strain, or "relative potency" (RP). With the PorA genotype, the RPs were then used to assess strain coverage by 4CMenB, a multicomponent MenB vaccine. In preliminary studies, MATS accurately predicted killing in the serum bactericidal assay using human complement, an accepted correlate of protection for meningococcal vaccines. A study across seven laboratories assessed the reproducibility of RPs for fHbp, NadA, and NHBA and established qualification parameters for new laboratories. RPs were determined in replicate for 17 MenB reference strains at laboratories A to G. The reproducibility of RPs among laboratories and against consensus values across laboratories was evaluated using a mixed-model analysis of variance. Interlaboratory agreement was very good; the Pearson correlation coefficients, coefficients of accuracy, and concordance correlation coefficients exceeded 99%. The summary measures of reproducibility, expressed as between-laboratory coefficients of variation, were 7.85% (fHbp), 16.51% (NadA), and 12.60% (NHBA). The overall within-laboratory measures of variation adjusted for strain and laboratory were 19.8% (fHbp), 28.8% (NHBA), and 38.3% (NadA). The MATS ELISA was successfully transferred to six laboratories, and a further laboratory was successfully qualified.
Project description:The epidemiology of invasive meningococcal disease (IMD) in Québec, Canada, has been dominated in the past decade by a clone of serogroup B (MenB) Neisseria meningitidis defined by multi-locus sequence typing (MLST) as sequence type (ST)-269. With the licensure of a new MenB vaccine Bexsero (4CMenB) in Canada, this study characterized invasive N. meningitidis recovered in Québec from 2009 to 2013, with an objective to examine the diversity of the 4CMenB vaccine antigens. Isolates were serogrouped by antisera and genogrouped by PCR, and further typed by whole cell ELISA for serotype and serosubtype antigens. Clonal analysis was done by MLST. Isolates were genotyped by analysis of their 4CMenB vaccine antigen genes of PorA, factor H binding protein (fHbp), Neisserial Heparin Binding Antigen (NHBA), and Neisseria Adhesin A (NadA).Of the 263 IMD isolates analysed, 229, 16, 10, 7, and 1 belonged to MenB, MenY, MenW, MenC, and MenX, respectively. Of the 229 MenB, 159 (69.4 %) were typed as ST-269 clonal complex (CC); and they possessed a restricted number of three fHbp and five nhba gene alleles. Nine N. meningitidis isolates (eight MenB and one MenY) were found to possess at least one gene that encoded for an antigen that matched exactly with protein variants in the 4CMenB vaccine. Two MenB expressed PorA antigen P1.4 and possessed the nhba gene for peptide 2; four other MenB were predicted to have NHBA peptide 2; another two MenB were predicted to encode fHbp peptide 1.1; and a single MenY was found to have nadA gene for NadA peptide 8. In addition, another 172 isolates were found to possess genes for variant 1 fHbp peptides other than peptide 1.1 or NadA variant 1-2/3 peptides other than peptide 8; and therefore, may potentially be covered by 4CMenB.The most prevalent clone of N. meningitidis in Quebec was ST-269 CC; and 96 % of the isolates in this CC were predicted to be covered by 4CMenB vaccine. Extensive genetic diversity was found in the other IMD isolates in Québec which might suggest a lower coverage by the vaccine when compared to the ST-269 MenB.
Project description:The poor immunogenicity of the meningococcal serogroup B (MenB) capsule has led to the development of vaccines targeting subcapsular antigens, in particular the immunodominant and diverse outer membrane porin, PorA. These vaccines are largely strain specific; however, they offer limited protection against the diverse MenB-associated diseases observed in many industrialized nations. To broaden the scope of its protection, the multicomponent vaccine (4CMenB) incorporates a PorA-containing outer membrane vesicle (OMV) alongside relatively conserved recombinant protein components, including factor H-binding protein (fHbp), Neisseria adhesin A (NadA), and neisserial heparin-binding antigen (NHBA). The expression of PorA is unique to meningococci (Neisseria meningitidis); however, many subcapsular antigens are shared with nonpathogenic members of the genus Neisseria that also inhabit the nasopharynx. These organisms may elicit cross-protective immunity against meningococci and/or occupy a niche that might otherwise accommodate pathogens. The potential for 4CMenB responses to impact such species (and vice versa) was investigated by determining the genetic distribution of the primary 4CMenB antigens among diverse members of the common childhood commensal, Neisseria lactamica. All the isolates possessed nhba but were devoid of fhbp and nadA. The nhba alleles were mainly distinct from but closely related to those observed among a representative panel of invasive MenB isolates from the same broad geographic region. We made similar findings for the immunogenic typing antigen, FetA, which constitutes a major part of the 4CMenB OMV. Thus, 4CMenB vaccine responses may impact or be impacted by nasopharyngeal carriage of commensal neisseriae. This highlights an area for further research and surveillance should the vaccine be routinely implemented.
Project description:Neisseria meningitidis is associated with high mortality and morbidity in infants and children worldwide. This phase 3 study (NCT02173704) evaluated safety and immunogenicity of a 4-component serogroup B recombinant meningococcal vaccine (4CMenB) co-administered with routine vaccines in Taiwanese infants. In total, 225 healthy infants were randomized (2 : 1 ) to receive 4CMenB and routine vaccines (4CMenB+Routine) or routine vaccines only (Routine group) at 2, 4, 6 and 12 months of age. Routine vaccines were diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae type b, 13-valent pneumococcal, hepatitis B, measles-mumps-rubella and varicella vaccines. Immune responses to 4CMenB components (factor H binding protein [fHbp], Neisserial adhesin A [NadA], porin A [PorA] and Neisseria heparin-binding antigen [NHBA]) were evaluated at 1 month post-primary and post-booster vaccination, using human serum bactericidal assay (hSBA). Reactogenicity and safety were also assessed. A sufficient immune response was demonstrated for fHbp, NadA and PorA, at 1 month post-primary and booster vaccination. In the 4CMenB+Routine group, hSBA titers ?5 were observed in all infants for fHbp and NadA, in 79% and 59% of infants for PorA and NHBA, respectively, at 1 month post-primary vaccination and in 92-99% of infants for all antigens, at 1 month post-booster vaccination. In the 4CMenB+Routine group, hSBA geometric mean titers for all antigens increased post-primary (8.41-963) and post-booster vaccination (17-2315) compared to baseline (1.01-1.36). Immunogenicity of 4CMenB was not impacted by co-administration with routine pediatric vaccines in infants. Reactogenicity was slightly higher in the 4CMenB+Routine group compared with Routine group, but no safety concerns were identified.
Project description:<h4>Background</h4>A novel meningococcal multicomponent vaccine, 4CMenB (Bexsero®), has been approved in Europe, Canada, Australia and US. The potential impact of 4CMenB on strain coverage is being estimated by using Meningococcal Antigen Typing System (MATS), an ELISA assay which measures vaccine antigen expression and diversity in each strain. Here we show the genetic characterization and the 4CMenB potential coverage of Spanish invasive strains (collected during one epidemiological year) compared to other European countries and discuss the potential reasons for the lower estimate of coverage in Spain.<h4>Material and methods</h4>A panel of 300 strains, a representative sample of all serogroup B Neisseria meningitidis notified cases in Spain from 2009 to 2010, was characterized by multilocus sequence typing (MLST) and FetA variable region determination. 4CMenB vaccine antigens, PorA, factor H binding protein (fHbp), Neisseria Heparin Binding Antigen (NHBA) and Neisserial adhesin A (NadA) were molecularly typed by sequencing. PorA coverage was assigned to strain with VR2 = 4. The levels of expression and cross-reactivity of fHbp, NHBA and NadA were analyzed using MATS ELISA.<h4>Findings</h4>Global estimated strain coverage by MATS was 68.67% (95% CI: 47.77-84.59%), with 51.33%, 15.33% and 2% of strains covered by one, two and three vaccine antigens, respectively. The predicted strain coverage by individual antigens was: 42% NHBA, 36.33% fHbp, 8.33% PorA and 1.33% NadA. Coverage within the most prevalent clonal complexes (cc) was 70.37% for cc 269, 30.19% for cc 213 and 95.83% for cc 32.<h4>Conclusions</h4>Clonal complexes (cc) distribution accounts for variations in strain coverage, so that country-by-country investigations of strain coverage and cc prevalence are important. Because the cc distribution could also vary over time, which in turn could lead to changes in strain coverage, continuous detailed surveillance and monitoring of vaccine antigens expression is needed in those countries where the multicomponent vaccine is introduced. This is really important in countries like Spain where most of the strains are predicted to be covered by only one vaccine antigen and the chance for escape mutants to emerge with vaccine use is higher. Based on the observed data, cc213 should receive special attention as it is associated with low predicted strain coverage, and has recently emerged in Spain.
Project description:Invasive disease caused by meningococcal capsular groups A, C, W-135, and Y is now preventable by means of glycoconjugate vaccines that target their respective polysaccharide capsules. The capsule of group B meningococci (MenB) is poorly immunogenic and may induce autoimmunity. Vaccines based on the major immunodominant surface porin, PorA, are effective against clonal epidemics but, thus far, have a limited scope of coverage against the wider MenB population at large. In an alternative approach, the first-generation, investigational, recombinant MenB (rMenB) plus outer membrane vesicle (OMV) (rMenB-OMV) vaccine contains a number of relatively conserved surface proteins, fHBP, NHBA (previously GNA2132), and NadA, alongside PorA P1.4-containing OMVs from the New Zealand MeNZB vaccine. MenB currently accounts for approximately 90% of cases of meningococcal disease in England and Wales. To assess potential rMenB-OMV vaccine coverage of pathogenic MenB isolates within this region, all English and Welsh MenB case isolates from January 2008 (n = 87) were genetically characterized with respect to fHBP, NHBA, NadA, and PorA. Alleles for fHbp, nhba, and porA were identified in all of the isolates, of which 22% were also found to harbor nadA alleles. On the basis of genotypic data and predicted immunological cross-reactivity, the potential level of rMenB-OMV vaccine coverage in England and Wales ranges from 66% to 100%.
Project description:Neisseria meningitidis, one of the major causes of bacterial meningitis and sepsis, is a member of the genus Neisseria, which includes species that colonize the mucosae of many animals. Three meningococcal proteins, factor H-binding protein (fHbp), neisserial heparin-binding antigen (NHBA), and N. meningitidis adhesin A (NadA), have been described as antigens protective against N. meningitidis of serogroup B, and they have been employed as vaccine components in preclinical and clinical studies. In the vaccine formulation, fHbp and NHBA were fused to the GNA2091 and GNA1030 proteins, respectively, to enhance protein stability and immunogenicity. To determine the possible impact of vaccination on commensal neisseriae, we determined the presence, distribution, and conservation of these antigens in the available genome sequences of the genus Neisseria, finding that fHbp, NHBA, and NadA were conserved only in species colonizing humans, while GNA1030 and GNA2091 were conserved in many human and nonhuman neisseriae. Sequence analysis showed that homologous recombination contributed to shape the evolution and distribution of both NHBA and fHbp, three major variants of which have been defined. fHbp variant 3 was probably the ancestral form of meningococcal fHbp, while fHbp variant 1 from N. cinerea was introduced into N. meningitidis by a recombination event. fHbp variant 2 was the result of a recombination event inserting a stretch of 483 bp from variant 1 into the variant 3 background. These data indicate that a high rate of exchange of genetic material between neisseriae that colonize the human upper respiratory tract exists. IMPORTANCE The upper respiratory tract of healthy individuals is a complex ecosystem colonized by many bacterial species. Among these, there are representatives of the genus Neisseria, including Neisseria meningitidis, a major cause of bacterial meningitis and sepsis. Given the close relationship between commensal and pathogenic species, a protein-based vaccine against N. meningitidis has the potential to impact the other commensal species of Neisseria. For this reason, we have studied the distribution and evolutionary history of the antigen components of a recombinant vaccine, 4CMenB, that recently received approval in Europe under the commercial name of Bexsero®. We found that fHbp, NHBA, and NadA can be found in some of the human commensal species and that the evolution of these antigens has been essentially shaped by the high rate of genetic exchange that occurs between strains of neisseriae that cocolonize the same environment.
Project description:Highly effective glycoconjugate vaccines exist against four of the five major pathogenic groups of meningococci: A, C, W-135, and Y. An equivalent vaccine against group B meningococci (menB) has remained elusive due to the poorly immunogenic capsular polysaccharide. A promising alternative, the investigational recombinant menB (rMenB)- outer membrane vesicle (OMV) vaccine, contains fHBP, NHBA (previously GNA2132), NadA, and outer membrane vesicles (OMVs) from the New Zealand MeNZB vaccine. MenB currently accounts for 90% of meningococcal disease in England and Wales, where the multilocus sequence type (ST) 269 (ST269) clonal complex (cc269) has recently expanded to account for a third of menB cases. To assess the potential cc269 coverage of the rMenB-OMV vaccine, English and Welsh cc269 isolates from the past decade were genetically characterized with respect to fHBP, NHBA, and NadA. All of the isolates harbored fHbp and nhba alleles, while 98% of the cc269 isolates were devoid of nadA. Subvariant profiling of fHbp, nhba, and porA against STs revealed the presence of two broadly distinct and well-defined clusters of isolates, centered around ST269 and ST275, respectively. An additional molecular marker, insertion sequence IS1301, was found to be present in 100% and <2% of isolates of the respective clusters. On the basis of the genetic data, the potential rMenB-OMV coverage of cc269 in England and Wales is high (up to 100%) within both clusters. Expression studies and serum bactericidal antibody assays will serve to enhance predictions of coverage and will augment ongoing studies regarding the significance of IS1301 within the ST269 cluster.