Vaccine potential of the Neisseria meningitidis 2086 lipoprotein

Meningococcal disease and the complement system

Despite considerable advances in the understanding of the pathogenesis of meningococcal disease, this infection remains a major cause of morbidity and mortality globally. The role of the complement system in innate immune defenses against invasive meningococcal disease is well established. Individuals deficient in components of the alternative and terminal complement pathways are highly predisposed to invasive, often recurrent meningococcal infections. Genome-wide analysis studies also point to a central role for complement in disease pathogenesis. Here we review the pathophysiologic events pertinent to the complement system that accompany meningococcal sepsis in humans. Meningococci use several often redundant mechanisms to evade killing by human complement. Capsular polysaccharide and lipooligosaccharide glycan composition play critical roles in complement evasion. Some of the newly described protein vaccine antigens interact with complement components and have sparked considerable research interest.

A multi-country evaluation of Neisseria meningitidis serogroup B factor H-binding proteins and implications for vaccine coverage in different age groups

BACKGROUND

Recombinant vaccines containing factor H-binding protein (fHBP) have been developed for the purpose of protection from invasive meningococcal serogroup B disease. Neisseria meningitidis fHBP sequences can be divided into 2 genetically and immunologically distinct subfamilies (A and B); thus, cross protection is conferred within but not between subfamilies. A comprehensive understanding of fHBP epidemiology is required to accurately assess the potential vaccine impact when considering different vaccination implementation strategies.

METHODS

Systematically collected invasive meningococcal serogroup B isolates from England, Wales, Northern Ireland, the United States, Norway, France and the Czech Republic were previously characterized for fHBP sequence. This study expanded the evaluation with additional meningococcal serogroup B disease isolates from Spain (n = 346) and Germany (n = 205). This expanded set (n = 1841), collected over a 6-year period (2001 to 2006), was evaluated for fHBP sequence and fHBP subfamily relative to patient age.

RESULTS

All 1841 isolates contained fhbp. fHBP sequences from Spain and Germany fell within the previously described subfamilies, with 69% of isolates belonging to subfamily B and 31% to subfamily A; prevalent sequence variants were also similar. Stratification of data by age indicated that disease in infants <1 year of age was caused by a significantly higher proportion of isolates with fHBP subfamily A variants than that seen in adolescents and young adults 11-25 years (47.7% versus 19.5%, P < 0.0001, respectively).

CONCLUSIONS

These observations highlight a difference in epidemiology of fHBP subfamilies in different age groups, with fHBP subfamily A strains causing more disease in vulnerable populations, such as infants, than in adolescents.

Meningococcal factor H-binding protein vaccines with decreased binding to human complement factor H have enhanced immunogenicity in human factor H transgenic mice

Factor H-binding protein (fHbp) is a component of a meningococcal vaccine recently licensed in Europe for prevention of serogroup B disease, and a second vaccine in clinical development. The protein specifically binds human factor H (fH), which down-regulates complement activation and enhances resistance to bactericidal activity. There are conflicting data from studies in human fH transgenic mice on whether binding of human fH to fHbp vaccines decreases immunogenicity, and whether mutant fHbp vaccines with decreased fH binding have enhanced immunogenicity. fHbp can be classified into two sub-families based on sequence divergence and immunologic cross-reactivity. Previous studies of mutant fHbp vaccines with low fH binding were from sub-family B, which account for approximately 60% of serogroup B case isolates. In the present study, we evaluated the immunogenicity of two mutant sub-family A fHbp vaccines containing single substitutions, T221A or D211A, which resulted in 15- or 30-fold lower affinity for human fH, respectively, than the corresponding control wild-type fHbp vaccine. In transgenic mice with high serum concentrations of human fH, both mutant vaccines elicited significantly higher IgG titers and higher serum bactericidal antibody responses than the control fHbp vaccine that bound human fH. Thus, mutations introduced into a sub-family A fHbp antigen to decrease fH binding can increase protective antibody responses in human fH transgenic mice. Collectively the data suggest that mutant fHbp antigens with decreased fH binding will result in superior vaccines in humans.

Distinct binding and immunogenic properties of the gonococcal homologue of meningococcal factor h binding protein

Neisseria meningitidis is a leading cause of sepsis and meningitis. The bacterium recruits factor H (fH), a negative regulator of the complement system, to its surface via fH binding protein (fHbp), providing a mechanism to avoid complement-mediated killing. fHbp is an important antigen that elicits protective immunity against the meningococcus and has been divided into three different variant groups, V1, V2 and V3, or families A and B. However, immunisation with fHbp V1 does not result in cross-protection against V2 and V3 and vice versa. Furthermore, high affinity binding of fH could impair immune responses against fHbp. Here, we investigate a homologue of fHbp in Neisseria gonorrhoeae, designated as Gonococcal homologue of fHbp (Ghfp) which we show is a promising vaccine candidate for N. meningitidis. We demonstrate that Gfhp is not expressed on the surface of the gonococcus and, despite its high level of identity with fHbp, does not bind fH. Substitution of only two amino acids in Ghfp is sufficient to confer fH binding, while the corresponding residues in V3 fHbp are essential for high affinity fH binding. Furthermore, immune responses against Ghfp recognise V1, V2 and V3 fHbps expressed by a range of clinical isolates, and have serum bactericidal activity against N. meningitidis expressing fHbps from all variant groups.

Neisseria meningitidis is a major cause of sepsis and meningitis in young children and adolescents. Although vaccines are currently available against several serogroups, a broadly effective vaccine against serogroup B is still needed. Factor H binding protein (fHbp) can bind the human complement regulator factor H (fH) and is an important meningococcal immunogen. fHbp is divided into three variant groups (V1, V2 and V3) and immunisation with V1 fHbp does not elicit cross-protection against meningococcus expressing fHbp V2 or V3, and vice versa. Here, we investigate a homologue of fHbp in Neisseria gonorrhoeae which we named Gonococcal homologue of factor H binding protein (Ghfp). We show that in contrast to fHbp, Ghfp is not expressed on the bacterial surface and is unable to bind to factor H. Surprisingly, we found that antibodies raised against Ghfp have the capacity to mediate protective immunity against N. meningitidis expressing any of the three variant groups of fHbp, and could provide a broadly protective vaccine against N. meningitidis.

Genetic distribution of noncapsular meningococcal group B vaccine antigens in Neisseria lactamica

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.

Mutant Native Outer Membrane Vesicles Combined with a Serogroup A Polysaccharide Conjugate Vaccine for Prevention of Meningococcal Epidemics in Africa

Background

The meningococcal serogroup A (MenA) polysaccharide conjugate vaccine used in Sub-Saharan Africa does not prevent disease caused by MenW or MenX strains, which also cause epidemics in the region. We investigated the vaccine-potential of native outer membrane vesicles with over-expressed factor H-binding protein (NOMV-fHbp), which targeted antigens in African meningococcal strains, and was combined with a MenA polysaccharide conjugate vaccine.

Methodology/Principal Findings

The NOMV-fHbp vaccine was prepared from a mutant African MenW strain with PorA P1.5,2, attenuated endotoxin (ΔLpxL1), deleted capsular genes, and over-expressed fHbp in variant group 1. The NOMV-fHbp was adsorbed with Al(OH)₃ and used to reconstitute a lyophilized MenA conjugate vaccine, which normally is reconstituted with liquid MenC, Y and W conjugates in a meningococcal quadrivalent conjugate vaccine (MCV4-CRM, Novartis). Mice immunized with the NOMV-fHbp vaccine alone developed serum bactericidal (human complement) activity against 13 of 15 African MenA strains tested; 10 of 10 African MenX strains, 7 of 7 African MenW strains, and 6 of 6 genetically diverse MenB strains with fHbp variant group 1 (including 1 strain from The Gambia). The combination NOMV-fHbp/MenA conjugate vaccine elicited high serum bactericidal titers against the two MenA strains tested that were resistant to bactericidal antibodies elicited by the NOMV-fHbp alone; the combination elicited higher titers against the MenA and MenW strains than those elicited by a control MCV4-CRM vaccine (P<0.05); and high titers against MenX and MenB strains. For most strains, the titers elicited by a control NOMV-fHbp knock out vaccine were <1∶10 except when the strain PorA matched the vaccine (titers >1∶000).

Conclusion/Significance

The NOMV-fHbp/MenA conjugate vaccine provided similar or higher coverage against MenA and MenW strains than a quadrivalent meningococcal conjugate vaccine, and extended protection against MenX strains responsible for epidemics in Africa, and MenB strains with fHbp in variant group 1.

fH-dependent complement evasion by disease-causing meningococcal strains with absent fHbp genes or frameshift mutations

Meningococci bind human fH to down-regulate complement, which enhances survival of the bacteria in serum. A major fH ligand is the vaccine candidate, factor H-binding protein (fHbp). Although fHbp has been considered an essential meningococcal virulence factor, rarely, invasive isolates with absent fHbp genes or frameshift mutations have been identified. In previous studies fH binding to these isolates was not detected. The aim of the present study was to investigate fH binding and complement evasion by invasive meningococcal serogroup B clinical isolates with absent fHbp genes or frameshift mutations. Four of the seven isolates tested bound human fH by flow cytometry and survived in IgG-depleted human serum. In all four, fH binding was decreased after inactivating the gene encoding NspA. Binding of fH to fHbp and NspA is specific for human fH. To investigate fH-dependent evasion of host defenses, human fH transgenic infant rats, or control littermates negative for human fH, were challenged IP with 10(3)-10(4)CFU of two of the isolates with no detectable fH binding by flow cytometry. At 6h, bacteremia caused by both strains was higher in human fH transgenic rats than in control rats (P<0.002). In conclusion, six of the seven isolates had evidence of fH binding and/or human fH-dependent complement evasion in transgenic rats. In four, NspA was as an alternative fH ligand. fHbp vaccination may select for mutants that do not require fHbp for complement evasion. Inclusion of additional target antigens in vaccines containing fHbp may delay emergence of these mutants.

Conservation of meningococcal antigens in the genus Neisseria

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.

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.

Vaccines for low-income countries

Low-income countries typically lag behind industrialised nations, where the introduction of new vaccines is commonly tailored to the pressures of the commercial market. Happily in recent years this paradigm has started to change with the introduction of a univalent meningococcal A conjugate vaccine that is specifically targeted for the prevention of epidemic meningitis in Africa. The declaration of the 2010s as a New Decade of Vaccines, together with Millennium Development Goals 4 and 5, provide a strong mandate for a new approach to the development of vaccines for low-income countries, so that there has never been a more exciting time to work in this field. This review considers the opportunities and challenges of developing these new vaccines in the context of innovations in vaccinology, the need to induce protective immunity in the populations at risk and the requirement for strong partnership between the countries that will use these vaccines and different elements of the vaccine industry.

Does binding of complement factor H to the meningococcal vaccine antigen, factor H binding protein, decrease protective serum antibody responses?

Factor H binding protein (fHbp) is a principal antigen in a multicomponent meningococcal vaccine recently licensed in Europe for prevention of serogroup B diseases. The protein recruits the complement downregulator, factor H (fH), to the bacterial surface, which enables the organism to resist complement-mediated bacteriolysis. Binding is specific for human fH. In preclinical studies, mice and rabbits immunized with fHbp vaccines developed serum bactericidal antibody responses, which in humans predict protection against developing meningococcal disease. These studies, however, were in animals whose fH did not bind to the vaccine antigen. Here we review the immunogenicity of fHbp vaccines in human fH transgenic mice. The data suggest that animals with high serum human fH concentrations have impaired protective antibody responses. Further, mutant fHbp vaccines with single amino acid substitutions that decrease fH binding are superior immunogens, possibly by unmasking epitopes in the fH binding site that are important for eliciting serum bactericidal antibody responses. Humans immunized with fHbp vaccines develop serum bactericidal antibody, but achieving broad coverage in infants required incorporation of additional antigens, including outer membrane vesicles, which increased rates of fever and local reactions at the injection site. The experimental results in transgenic mice predict that fHbp immunogenicity can be improved in humans by using mutant fHbp vaccines with decreased fH binding. These results have important public health implications for developing improved fHbp vaccines for control of serogroup B meningococcal disease and for development of vaccines against other microbes that bind host molecules.

Pathogenesis of meningococcemia

Neisseria meningitidis is responsible for two major diseases: cerebrospinal meningitis and/or septicemia. The latter can lead to a purpura fulminans, an often-fatal condition owing to the associated septic shock. These two clinical aspects of the meningococcal infection are consequences of a tight interaction of meningococci with host endothelial cells. This interaction, mediated by the type IV pili, is responsible for the formation of microcolonies on the apical surface of the cells. This interaction is followed by the activation of signaling pathways in the host cells leading to the formation of a microbiological synapse. A low level of bacteremia is likely to favor the colonization of brain vessels, leading to bacterial meningitis, whereas the colonization of a large number of vessels by a high number of bacteria is responsible for one of the most severe forms of septic shock observed.

Introducing vaccination against serogroup B meningococcal disease: an economic and mathematical modelling study of potential impact

BACKGROUND

Meningococcal disease remains an important cause of morbidity and mortality worldwide. The first broadly effective vaccine against group B disease (which causes considerable meningococcal disease in Europe, the Americas and Australasia) was licensed in the EU in January 2013; our objective was to estimate the potential impact of introducing such a vaccine in England.

METHODS

We developed two models to estimate the impact of introducing a new 'MenB' vaccine. The cohort model assumes the vaccine protects against disease only; the transmission dynamic model also allows the vaccine to protect against carriage (accounting for herd effects). We used these, and economic models, to estimate the case reduction and cost-effectiveness of a number of different vaccine strategies.

RESULTS

We estimate 27% of meningococcal disease cases could be prevented over the lifetime of an English birth cohort by vaccinating infants at 2,3,4 and 12 months of age with a vaccine that prevents disease only; this strategy could be cost-effective at £9 per vaccine dose. Substantial reductions in disease (71%) can be produced after 10 years by routinely vaccinating infants in combination with a large-scale catch-up campaign, using a vaccine which protects against carriage as well as disease; this could be cost-effective at £17 per vaccine dose.

CONCLUSIONS

New 'MenB' vaccines could substantially reduce disease in England and be cost-effective if competitively priced, particularly if the vaccines can prevent carriage as well as disease. These results are relevant to other countries, with a similar epidemiology to England, considering the introduction of a new 'MenB' vaccine.

Importance of inhibition of binding of complement factor H for serum bactericidal antibody responses to meningococcal factor H-binding protein vaccines

BACKGROUND

Factor H (fH) binding protein (fHbp) is part of vaccines developed for prevention of meningococcal serogroup B disease. More than 610 fHbp amino acid sequence variants have been identified, which can be classified into 2 subfamilies. The extent of cross-protection within a subfamily has been difficult to assess because of strain variation in fHbp expression.

METHODS

Using isogenic mutant strains, we compared cross-protective serum antibody responses of mice immunized with 7 divergent fHbp variants in subfamily B, including identification numbers (ID) 1 and 55, which were chosen for vaccine development.

RESULTS AND CONCLUSIONS

In the presence of the human complement downregulator fH, the ability of the anti-fHbp antibodies to deposit sufficient complement C3b on the bacterial surface to elicit bactericidal activity required inhibition of binding of fH by the anti-fHbp antibodies. With less bound fH, the bacteria became more susceptible to complement-mediated bactericidal activity. Among the different fHbp sequence variants, those more central in a phylogenic network than ID 1 or 55 elicited anti-fHbp antibodies with broader inhibition of fH binding and broader bactericidal activity. Thus, the more central variants show promise of extending protection to strains with divergent fHbp sequences that are covered poorly by fHbp variants in clinical development.

An analysis of the sequence variability of meningococcal fHbp, NadA and NHBA over a 50-year period in the Netherlands

Studies of meningococcal evolution and genetic population structure, including the long-term stability of non-random associations between variants of surface proteins, are essential for vaccine development. We analyzed the sequence variability of factor H-binding protein (fHbp), Neisserial Heparin-Binding Antigen (NHBA) and Neisseria adhesin A (NadA), three major antigens in the multicomponent meningococcal serogroup B vaccine 4CMenB. A panel of invasive isolates collected in the Netherlands over a period of 50 years was used. To our knowledge, this strain collection covers the longest time period of any collection available worldwide. Long-term persistence of several antigen sub/variants and of non-overlapping antigen sub/variant combinations was observed. Our data suggest that certain antigen sub/variants including those used in 4CMenB are conserved over time and promoted by selection.

Vaccines, reverse vaccinology, and bacterial pathogenesis

Advances in genomics and innovative strategies such as reverse vaccinology have changed the concepts and approaches to vaccine candidate selection and design. Genome mining and blind selection of novel antigens provide a novel route to investigate the mechanisms that underpin pathogenesis. The resulting lists of novel candidates are revealing new aspects of pathogenesis of target organisms, which in turn drives the rational design of optimal vaccine antigens. Here we use the discovery, characterization, and exploitation of fHbp, a vaccine candidate and key virulence factor of meningococcus, as an illustrative case in point. Applying genomic approaches to study both the pathogen and host will ultimately increase our fundamental understanding of pathogen biology, mechanisms responsible for the development of protective immunity, and guide next-generation vaccine design.

A randomized, controlled, phase 1/2 trial of a Neisseria meningitidis serogroup B bivalent rLP2086 vaccine in healthy children and adolescents

BACKGROUND

Neisseria meningitidis serogroup B (MnB) is a significant cause of invasive meningococcal disease. Factor H binding protein (also known as LP2086) is a conserved outer membrane neisserial lipoprotein that has emerged as a strong candidate protein antigen for MnB vaccination. This study examined the safety, tolerability and immunogenicity of an initial formulation of a bivalent recombinant LP2086 (rLP2086) vaccine in healthy children and adolescents.

METHODS

In this randomized, observer-blinded, parallel-group, multicenter trial conducted at 6 centers in Australia, 127 healthy participants aged 8-14 years were assigned to receive 20, 60 or 200 µg of the bivalent rLP2086 vaccine (n = 16, 45 and 45, respectively) or active control (Twinrix, n = 21) at 0, 1 and 6 months. Immunogenicity was assessed before the first dose and 1 month after doses 2 and 3. Local reactions, systemic events and other adverse events were recorded. The primary immunogenicity endpoint was the rate of seroconversion (≥4-fold rise in human complement serum bactericidal assay titer) against MnB strains expressing the homologous A05 or heterologous B02 LP2086 variants.

RESULTS

The bivalent rLP2086 vaccine was generally well-tolerated, with mostly mild to moderate local reactions. The most common adverse events, headache and upper respiratory tract infection, occurred with similar frequency in each group. Post-dose 3 seroconversion rates against strains expressing B02 and A05 variants were 68.8-95.3% for rLP2086 recipients and 0% for Twinrix recipients.

CONCLUSIONS

The bivalent rLP2086 vaccine was well-tolerated and immunogenic in healthy children and adolescents, supporting further evaluation as a broadly protective MnB vaccine.

ZnuD, a potential candidate for a simple and universal Neisseria meningitidis vaccine

Neisseria meningitidis serogroup B (MenB) is a major cause of bacterial sepsis and meningitis, with the highest disease burden in young children. Available vaccines are based on outer membrane vesicles (OMVs) obtained from wild-type strains. However, particularly in toddlers and infants, they confer protection mostly against strains expressing the homologous protein PorA, a major and variable outer membrane protein. In the quest for alternative vaccine antigens able to provide broad MenB strain coverage in younger populations, but potentially also across all age groups, ZnuD, a protein expressed under zinc-limiting conditions, may be considered a promising candidate. Here, we have investigated the potential value of ZnuD and show that it is a conserved antigen expressed by all MenB strains tested except for some strains of clonal complex ST-8. In mice and guinea pigs immunized with ZnuD-expressing OMVs, antibodies were elicited that were able to trigger complement-mediated killing of all the MenB strains and serogroup A, C, and Y strains tested when grown under conditions of zinc limitation. ZnuD is also expressed during infection, since anti-ZnuD antibodies were detected in sera from patients. In conclusion, we confirm the potential of ZnuD-bearing OMVs as a component of an effective MenB vaccine.

Neisseria meningitidis serogroup B vaccine development

Neisseria meningitidis is an air-borne, gram-negative pathogen that actively invades its human host leading to the development of life-threatening pathologies. As one of the leading causes of death in the world, during an epidemic period N. meningitidis can be responsible for nearly 1000 new infections per 100,000 individuals. The bacterial species is further categorized into 13 serotypes, with five, A, B, C, W-135, and Y, being the most clinically relevant, causing the overwhelming majority of diseases. There are two contemporary, purified protein conjugate vaccines available that function by targeting serogroups A, C, W-135, and Y. Historically, serogroup B has posed a vaccination challenge; however, there are currently two vaccines in development able to target serotype B. This review will highlight N. meningitidis as a pathogen and explore the recent literature providing a current review of meningococcal vaccination development.

Structural vaccinology starts to deliver

Following the impact of the genomics revolution on vaccine research and the development of reverse vaccinology, it was predicted that another new approach, structure-based antigen design, would become a driving force for vaccine innovation. Now, 5 years on, there are several examples of how structure-based design, or structural vaccinology, can deliver new vaccine antigens that were not possible before. Here, we discuss some of these examples and the contribution of structural vaccinology to our understanding of the protective epitopes of important bacterial and viral pathogens.

A phase 2 open-label safety and immunogenicity study of a meningococcal B bivalent rLP2086 vaccine in healthy adults

BACKGROUND

Neisseria meningitidis serogroup B (MnB) is a leading cause of bacterial meningitis and septicemia in adolescents and young adults. No currently licensed and available vaccine has been shown to provide broad protection against endemic MnB disease. A bivalent rLP2086 vaccine based on two factor H-binding proteins (fHBPs) has been developed to provide broad protection against MnB disease-causing strains.

METHODS

This study assessed the safety and immunogenicity of the final formulation of a bivalent rLP2086 vaccine in 60 healthy adults (18-40 years of age) receiving 120 μg doses at 0, 1, and 6 months. Safety was assessed by collecting solicited reactogenicity data and participant-reporting of adverse events. Immunogenicity was evaluated by human serum bactericidal assay (hSBA) against 5 MnB strains expressing distinct fHBP variants and fHBP-specific immunoglobulin G titre.

RESULTS

After each immunisation, local reactions such as pain at the injection site and erythema were generally mild or moderate. The most common vaccine-related adverse event was upper respiratory tract infection, which was reported by two participants. Seroprotection (hSBA titres ≥ 1:4) was achieved in 94.3% of participants against a MnB strain expressing the vaccine-homologous fHBP variant A05 and 70.0%-94.7% against MnB strains expressing the heterologous fHBP variants B02, A22, B44, and B24. Seroconversion rates (≥ 4-fold rise in hSBA titres) ranged from 70.0% to 94.7% across the five MnB test strains following the 3-dose vaccination regimen. Immunogenicity responses tended to increase upon subsequent vaccine doses.

CONCLUSIONS

Bivalent rLP2086 is a promising vaccine candidate for broad protection against MnB disease-causing strains.

Potential impact of the bivalent rLP2806 vaccine on Neisseria meningitidis carriage and invasive serogroup B disease

Asymptomatic throat carriage of Neisseria meningitidis is common in healthy individuals. In unusual cases, the bacteria become invasive, resulting in life-threatening disease. Effective meningococcal serogroup B (MnB) vaccines should provide broad protection against disease-causing strains and may confer indirect protection by impacting carriage and subsequent transmission. Factor H binding proteins (fHBPs), components of MnB vaccines in development, are classified into two immunologically distinct subfamilies (A and B). fHBP variants of MnB strains carried by adolescents are similar to those detected in infants with MnB disease. A vaccine containing subfamily A and B fHBP variants elicited bactericidal antibody responses (titers ≥ 1:4) against MnB strains expressing fHBP variants common to carriage strains and strains that cause disease in adolescents and infants in 75–100% of adolescent study subjects. This suggests that the bivalent fHBP vaccine has the potential to provide protection against invasive MnB strains and interrupt meningococcal carriage, which may also reduce infant MnB disease.

The factor H binding protein of Neisseria meningitidis interacts with xenosiderophores in vitro

The factor H binding protein (fHbp) is a key virulence factor of Neisseria meningitidis that confers to the bacterium the ability to resist killing by human serum. The determination of its three-dimensional structure revealed that the carboxyl terminus of the protein folds into an eight-stranded β barrel. The structural similarity of this part of the protein to lipocalins provided the rationale for exploring the ability of fHbp to bind siderophores. We found that fHbp was able to bind in vitro siderophores belonging to the cathecolate family and mapped the interaction site by nuclear magnetic resonance. Our results indicated that the enterobactin binding site was distinct from the site involved in binding to human factor H and stimulates new hypotheses about possible multiple activities of fHbp.

Design and evaluation of meningococcal vaccines through structure-based modification of host and pathogen molecules

Neisseria meningitis remains a leading cause of sepsis and meningitis, and vaccines are required to prevent infections by this important human pathogen. Factor H binding protein (fHbp) is a key antigen that elicits protective immunity against the meningococcus and recruits the host complement regulator, fH. As the high affinity interaction between fHbp and fH could impair immune responses, we sought to identify non-functional fHbps that could act as effective immunogens. This was achieved by alanine substitution of fHbps from all three variant groups (V1, V2 and V3 fHbp) of the protein; while some residues affected fH binding in each variant group, the distribution of key amino underlying the interaction with fH differed between the V1, V2 and V3 proteins. The atomic structure of V3 fHbp in complex with fH and of the C-terminal barrel of V2 fHbp provide explanations to the differences in the precise nature of their interactions with fH, and the instability of the V2 protein. To develop transgenic models to assess the efficacy of non-functional fHbps, we determined the structural basis of the low level of interaction between fHbp and murine fH; in addition to changes in amino acids in the fHbp binding site, murine fH has a distinct conformation compared with the human protein that would sterically inhibit binding to fHbp. Non-functional V1 fHbps were further characterised by binding and structural studies, and shown in non-transgenic and transgenic mice (expressing chimeric fH that binds fHbp and precisely regulates complement system) to retain their immunogenicity. Our findings provide a catalogue of non-functional fHbps from all variant groups that can be included in new generation meningococcal vaccines, and establish proof-in-principle for clinical studies to compare their efficacy with wild-type fHbps.

Vaccines are currently available against several serogroups of Neisseria meningitidis. However broadly effective serogroup B vaccines are still required as capsule-based approaches cannot be implemented with this serogroup because of the risks of auto-immunity. As a result, vaccines based on proteins in the bacterial outer membrane are being developed. Factor H binding protein (fHbp) is an important meningococcal immunogen which is able to bind the human complement regulator factor H (fH) at high affinity; this interaction could impair the efficacy of fHbp-based vaccines. Here we perform structure:function analyses to define non-functional fHbps and to explain the basis for the host specificity of the fHbp:fH interaction. The vaccine candidacy of non-functional fHbps was compared with wild-type proteins in a relevant transgenic model. These findings should allow the design and evaluation of future fHbp vaccines against this important human pathogen.

Meningococcal factor H binding protein fHbpd184 polymorphism influences clinical course of meningococcal meningitis

Factor H Binding protein (fHbp) is an important meningococcal virulence factor, enabling the meningococcus to evade the complement system, and a main target for vaccination. Recently, the structure of fHBP complexed with factor H (fH) was published. Two fHbp glutamic acids, E₂₈₃ and E₃₀₄, form salt bridges with fH, influencing interaction between fHbp and fH. Fifteen amino acids were identified forming hydrogen bonds with fH. We sequenced fHbp of 254 meningococcal isolates from adults with meningococcal meningitis included in a prospective clinical cohort to study the effect of fHbp variants on meningococcal disease severity and outcome. All fHbp of subfamily A had E304 substituted with T304. Of the 15 amino acids in fHbp making hydrogen bonds to fH, 3 were conserved, 11 show a similar distribution between the two fHbp subfamilies as the polymorphism at position 304. The proportion of patients infected with meningococci with fHbp of subfamily A with unfavorable outcome was 2.5-fold lower than that of patients infected with meningococci with fHbp of subfamily B (2 of 40 (5%) vs. 27 of 213 (13%) (P = 0.28). The charge of 2 of 15 amino acids (at position 184 and 306) forming hydrogen bonds was either basic or acidic. The affinity of fHbp_K184 and of fHbp_D184 for recombinant purified human fH was assessed by Surface Plasmon Resonance and showed average K_D of 2.60×10⁻⁸ and 1.74×10⁻⁸, respectively (ns). Patients infected with meningococci with fHbp_D184 were more likely to develop septic shock during admission (11 of 42 [26%] vs. 19 of 211 [9%]; P = 0.002) resulting in more frequent unfavorable outcome (9 of 42 [21%] vs. 20 of 211 [10%]; P = 0.026). In conclusion, we dentified fHBP_D184 to be associated with septic shock in patients with meningococcal meningitis.

Safety and immunogenicity of a meningococcal B bivalent rLP2086 vaccine in healthy toddlers aged 18-36 months: a phase 1 randomized-controlled clinical trial

BACKGROUND

A bivalent, recombinant, factor H-binding protein (rLP2086) vaccine was developed to protect against invasive Neisseria meningitidis serogroup B (MnB) in children and adolescents.

METHODS

Healthy toddlers (N = 99) were enrolled to 3 ascending dose-level cohorts (20, 60 or 200 μg). Within each cohort (n = 33), subjects were randomized to receive an initial formulation of the bivalent rLP2086 vaccine at 0, 1 and 6 months or hepatitis A vaccine/placebo control (2:1 ratio). Reactogenicity was assessed by parental reporting of local and systemic reactions using electronic diaries and reports of unsolicited adverse events. Immunogenicity was assessed by serum bactericidal activity assay using human complement and rLP2086-specific IgG binding.

RESULTS

The vaccine was considered to be well tolerated. Tenderness was the most frequently reported local reaction. Upper respiratory tract infection was the most commonly reported adverse event and occurred more frequently in the control group. Three cases (200 μg dose) of severe erythema that did not interfere with limb movement were reported. Four toddlers developed fever >40.0°C, 3 in the 200 μg group and 1 in the 60 μg group. Postdose 3, seroconversion (serum bactericidal activity assay using human complement ≥4-fold rise from baseline) was observed in 61.1-88.9% of participants against MnB strains expressing LP2086 variants homologous or nearly homologous to vaccine antigens and 11.1-44.4% against MnB strains expressing heterologous LP2086 variants. Seroconversion was observed in 77.8-100% of participants against additional, exploratory MnB strains expressing vaccine-homologous or heterologous LP2086 variants.

CONCLUSIONS

This study shows that the bivalent rLP2086 vaccine is well tolerated and immunogenic in toddlers.

History of meningococcal vaccines and their serological correlates of protection

For over a hundred years Neisseria meningitidis has been known to be one of the major causes of bacterial meningitis. However, effective vaccines were not developed until the latter part of the 20th century. The first of these were based on purified high molecular weight capsular polysaccharides and more recently the development of glycoconjugate vaccines has made paediatric immunisation programmes possible. The prevention of group B meningococcal disease has remained a challenge throughout this period. This review charts the history of the development of meningococcal vaccines and the importance of serological correlates of protection in their evaluation.

Considerations for controlling invasive meningococcal disease in high income countries

The development of conjugate vaccines has enabled the prevention and control of Neisseria meningitidis caused by serogroups A, C, W-135 and Y. Vaccines that provide protection against a broad number of serogroup B strains likely will be available soon to enable greater control of meningococcal disease in high income countries. We present an argument for adequate post-marketing surveillance to monitor epidemiological shifts and to provide a context for the safety and reactogenicity of serogroup B vaccines, including the newer recombinant vaccines. We also offer a series of recommendations to address possible concerns about vaccine safety.

The new multicomponent vaccine against meningococcal serogroup B, 4CMenB: immunological, functional and structural characterization of the antigens

Neisseria meningitidis is a major cause of endemic cases and epidemics of meningitis and devastating septicemia. Although effective vaccines exist for several serogroups of pathogenic N. meningitidis, conventional vaccinology approaches have failed to provide a universal solution for serogroup B (MenB) which consequently remains an important burden of disease worldwide. The advent of whole-genome sequencing changed the approach to vaccine development, enabling the identification of potential vaccine candidates starting directly with the genomic information, with a process named reverse vaccinology. The application of reverse vaccinology to MenB allowed the identification of new protein antigens able to induce bactericidal antibodies. Three highly immunogenic antigens (fHbp, NadA and NHBA) were combined with outer membrane vesicles and formulated for human use in a multicomponent vaccine, named 4CMenB. This is the first MenB vaccine based on recombinant proteins able to elicit a robust bactericidal immune response in adults, adolescents and infants against a broad range of serogroup B isolates. This review describes the successful story of the development of the 4CMenB vaccine, with particular emphasis on the functional, immunological and structural characterization of the protein antigens included in the vaccine.

Can we, should we, eradicate the meningococcus?

The eradication of infectious agents is an attractive means of disease control that, to date, has been achieved for only one human pathogen, the smallpox virus. The introduction of vaccines against Neisseria meningitidis into immunisation schedules, and particularly the conjugate polysaccharide vaccines which can interrupt transmission, raises the question of whether disease caused by this obligate human bacterium can be controlled, eliminated, or even eradicated. The limited number of meningococcal serogroups, lack of an animal reservoir, and importance of meningococcal disease are considerations in favour of eradication; however, the commensal nature of most infections, the high diversity of meningococcal populations, and the lack of comprehensive vaccines are all factors that suggest that this is not feasible. Indeed, any such attempt might be harmful by perturbing the human microbiome and its interaction with the immune system. On balance, the control and possible elimination of disease caused by particular disease-associated meningococcal genotypes is a more achievable and worthwhile goal.

[Meningococcal serogroup B vaccines]

The diversity and antigenic variability of Neisseria meningitidis serogroup B strains around the world has been a major challenge to developing a vaccine with broad coverage. Outer-membrane vesicle vaccines appear to be safe and effective but are strain-specific vaccines and used in delimited areas. Also, recombinant protein vaccines such as factor H binding protein, given alone or in combination with others antigens have been developed and may be effective against the majority of group B strains.

A bivalent Neisseria meningitidis recombinant lipidated factor H binding protein vaccine in young adults: results of a randomised, controlled, dose-escalation phase 1 trial

Neisseria meningitidis is a leading cause of meningitis and septicaemia, but a broadly-protective vaccine against endemic serogroup B disease is not licensed and available. The conserved, outer-membrane lipoprotein factor H binding protein (fHBP, also known as LP2086) is expressed as one of two subfamily variants in virtually all meningococci. This study investigated the safety, tolerability, and immunogenicity of a recombinant-expressed bivalent fHBP (r-fHBP) vaccine in healthy adults. Participants (N=103) aged 18-25 years were recruited into three ascending dose level cohorts of 20, 60, and 200μg of a bivalent r-fHBP vaccine formulation and randomised to receive vaccine or placebo at 0, 1, and 6 months. The vaccine was well tolerated. Geometric mean titres (GMTs) for r-fHBP subfamily-specific IgG antibodies increased 19-168-fold from pre-vaccination to post-dose 2 in a dose level-dependent manner. In addition, robust serum bactericidal assay using human complement (hSBA) responses for strains expressing both homologous and heterologous fHBP variants were observed. After three vaccinations, 16-52% of the placebo group and 47-90%, 75-100%, and 88-100%, of the 20, 60, and 200μg dose levels, respectively, had seroprotective (≥ 1:4) hSBA titres against six serogroup B strains. The bivalent r-fHBP vaccine was well tolerated and induced robust bactericidal activity against six diverse serogroup B strains in young adults at the 60 and 200μg dose levels.

A phase 1, randomized, open-label, active-controlled trial to assess the safety of a meningococcal serogroup B bivalent rLP2086 vaccine in healthy adults

Neisseria meningitidis serogroup B (MnB) is a significant cause of invasive meningococcal disease, but no broadly protective vaccine is yet approved. We assessed the safety and immunogenicity of a bivalent MnB vaccine composed of lipidated subfamily A and B variants of recombinant LP2086 (rLP2086, also known as factor H binding protein, fHBP). Forty-eight adults, ages 18-40 y, were randomized to receive 60, 120 or 200 μg of the bivalent rLP2086 vaccine or control at 0, 2 and 6 mo. Immunogenicity was assessed by rLP2086-specific immunoglobulin G (IgG) geometric mean titers for subfamily A and B proteins. Safety was determined by laboratory assessments of blood and urine and by reporting of solicited and unsolicited adverse events (AEs). The bivalent rLP2086 vaccine elicited high IgG titers following the second and third vaccination at all dose levels. In each of the four study arms, 11 of the 12 participating subjects reported ≥ 1 AE, and no serious AEs were reported. Local and systemic reactions were mainly mild to moderate. Laboratory abnormalities (including increased sodium, decreased neutrophils, and proteinuria) were not associated with clinical events and were not considered to be related to the study vaccine. Vaccinations were generally well-tolerated. Strong IgG antibody responses and the absence of clinically significant laboratory abnormalities support further development of the bivalent rLP2086 vaccine (www.clinicaltrials.gov; identifier: NCT00879814).

Evolutionary and genomic insights into meningococcal biology

Epidemic disease caused by Neisseria meningitidis, the meningococcus, has been recognized for two centuries, but remains incompletely controlled and understood. There have been dramatic reductions in serogroup A and C meningococcal disease following the introduction of protein-polysaccharide conjugate vaccines, but there is currently no comprehensive vaccine against serogroup B meningococci. Genetic analyses of meningococcal populations have provided many insights into the biology, evolution and pathogenesis of this important pathogen. The meningococcus, and its close relative the gonococcus, are the only pathogenic members of the genus Neisseria, and the invasive propensity of meningococci varies widely, with approximately a dozen 'hyperinvasive lineages' responsible for most disease. Despite this, attempts to identify a 'pathogenome', a subset of genes associated with the invasive phenotypes, have failed; however, genome-wide studies of representative meningococcal isolates using high-throughput sequencing are beginning to provide details on the relationship of invasive phenotype and genotype in this fascinating organism and how this relationship has evolved.

Design of meningococcal factor H binding protein mutant vaccines that do not bind human complement factor H

Meningococcal factor H binding protein (fHbp) is a human species-specific ligand for the complement regulator, factor H (fH). In recent studies, fHbp vaccines in which arginine at position 41 was replaced by serine (R41S) had impaired fH binding. The mutant vaccines elicited bactericidal responses in human fH transgenic mice superior to those elicited by control fHbp vaccines that bound human fH. Based on sequence similarity, fHbp has been classified into three variant groups. Here we report that although R41 is present in fHbp from variant groups 1 and 2, the R41S substitution eliminated fH binding only in variant group 1 proteins. To identify mutants in variant group 2 with impaired fH binding, we generated fHbp structural models and predicted 63 residues influencing fH binding. From these, we created 11 mutants with one or two amino acid substitutions in a variant group 2 protein and identified six that decreased fH binding. Three of these six mutants retained conformational epitopes recognized by all six anti-fHbp monoclonal antibodies (MAbs) tested and elicited serum complement-mediated bactericidal antibody titers in wild-type mice that were not significantly different from those obtained with the control vaccine. Thus, fHbp amino acid residues that affect human fH binding differ across variant groups. This result suggests that fHbp sequence variation induced by immune selection also affects fH binding motifs via coevolution. The three new fHbp mutants from variant group 2, which do not bind human fH, retained important epitopes for eliciting bactericidal antibodies and may be promising vaccine candidates.

The effect of human factor H on immunogenicity of meningococcal native outer membrane vesicle vaccines with over-expressed factor H binding protein

The binding of human complement inhibitors to vaccine antigens in vivo could diminish their immunogenicity. A meningococcal ligand for the complement down-regulator, factor H (fH), is fH-binding protein (fHbp), which is specific for human fH. Vaccines containing recombinant fHbp or native outer membrane vesicles (NOMV) from mutant strains with over-expressed fHbp are in clinical development. In a previous study in transgenic mice, the presence of human fH impaired the immunogenicity of a recombinant fHbp vaccine. In the present study, we prepared two NOMV vaccines from mutant group B strains with over-expressed wild-type fHbp or an R41S mutant fHbp with no detectable fH binding. In wild-type mice in which mouse fH did not bind to fHbp in either vaccine, the NOMV vaccine with wild-type fHbp elicited 2-fold higher serum IgG anti-fHbp titers (P = 0.001) and 4-fold higher complement-mediated bactericidal titers against a PorA-heterologous strain than the NOMV with the mutant fHbp (P = 0.003). By adsorption, the bactericidal antibodies were shown to be directed at fHbp. In transgenic mice in which human fH bound to the wild-type fHbp but not to the R41S fHbp, the NOMV vaccine with the mutant fHbp elicited 5-fold higher serum IgG anti-fHbp titers (P = 0.002), and 19-fold higher bactericidal titers than the NOMV vaccine with wild-type fHbp (P = 0.001). Thus, in mice that differed only by the presence of human fH, the respective results with the two vaccines were opposite. The enhanced bactericidal activity elicited by the mutant fHbp vaccine in the presence of human fH far outweighed the loss of immunogenicity of the mutant protein in wild-type animals. Engineering fHbp not to bind to its cognate complement inhibitor, therefore, may increase vaccine immunogenicity in humans.

Vaccines containing factor H-binding protein (fHbp) are being developed for protection against bacterial meningitis and sepsis caused by meningococci. The antigen was identified from genomic sequences and only later found to bind a human complement protein, factor H (fH), but not fH from non-human species. In previous studies, native outer membrane vesicle (NOMV) vaccines from mutants with over-expressed fHbp elicited broadly protective serum antibodies in mice whose fH did not bind to fHbp in the vaccine. In this study, the authors immunized transgenic mice and showed that the presence of human fH decreased serum bactericidal antibody responses to a NOMV vaccine with fHbp that bound human fH. In contrast, a NOMV vaccine containing fHbp with a single amino acid substitution that eliminated fH binding elicited nearly twenty-fold higher protective antibody responses. Thus, a simple change in a vaccine antigen to eliminate binding to a host protein can increase immunogenicity.

Neisseria meningitidis serogroup B lipooligosaccharide genotyping reveals high prevalence of L2 strains in Spain and unexpected relationship with factor H-binding protein expression

Neisseria meningitidis may be classified according to the lipooligosaccharide immunotype. We show that this classification can be achieved by PCR genotyping of the genes involved in the lipooligosaccharide inner-core biosynthesis, lpt3, lpt6, lgtG and lot3. Genotyping data correlated well (90-100%) with mass spectrometry data and was, therefore, applied to screen a random subset of recent N. meningitidis serogroup B isolates from Europe. Analysis of the proportion of the different lipooligosaccharide types highlighted the predominance of L3 strains. Surprisingly, high rates of L2 type strains were found in Spain (17%, versus 2.5% in Germany and 1.9% in the United Kingdom). Therefore, we also investigated further these Spanish L2 strains in an attempt to explain such prevalence despite the known sensitivity of L2 immunotype to complement. We explored the hypothesis that these strains express high amounts of factor H-binding protein (fHbp), but we found, on the contrary, that L2 strains express low or undetectable amounts of fHbp. Our findings suggest that, in addition to a genetic analysis, a multivalent approach may be necessary to estimate the effectiveness of a N. meningitidis serogroup B vaccine.

A broadly cross-reactive monoclonal antibody against an epitope on the n-terminus of meningococcal fHbp

Meningococcal factor H binding protein (fHbp) is an important vaccine antigen for prevention of disease caused by capsular group B strains. The protein has been sub-classified into three variant groups. Most anti-fHbp antibodies are variant group-specific and recognize epitopes on the C-terminal domain. We report a murine IgG1 mAb, JAR 41, which broadly cross-reacted with fHbp sequence variants from all variant groups. The mAb bound to the surface of live meningococci with fHbp from each of the three variant groups. In combination with second non-bactericidal anti-fHbp mAbs, JAR 41 elicited complement-mediated bactericidal activity in vitro, and augmented passive protection against meningococcal bacteremia in human fH transgenic rats. The epitope was located on a conserved region of the N-terminal portion of the fHbp molecule opposite that of fH contact residues. The data underscore the importance of broadly cross-reactive, surface-exposed epitopes on the N-terminal domain in the design of protective fHbp vaccines.

Monoclonal antibodies to meningococcal factor H binding protein with overlapping epitopes and discordant functional activity

Background

Meningococcal factor H binding protein (fHbp) is a promising vaccine candidate. Anti-fHbp antibodies can bind to meningococci and elicit complement-mediated bactericidal activity directly. The antibodies also can block binding of the human complement down-regulator, factor H (fH). Without bound fH, the organism would be expected to have increased susceptibility to bacteriolysis. Here we describe bactericidal activity of two anti-fHbp mAbs with overlapping epitopes in relation to their different effects on fH binding and bactericidal activity.

Methods and Principal Findings

Both mAbs recognized prevalent fHbp sequence variants in variant group 1. Using yeast display and site-specific mutagenesis, binding of one of the mAbs (JAR 1, IgG3) to fHbp was eliminated by a single amino acid substitution, R204A, and was decreased by K143A but not by R204H or D142A. The JAR 1 epitope overlapped that of previously described mAb (mAb502, IgG2a) whose binding to fHbp was eliminated by R204A or R204H substitutions, and was decreased by D142A but not by K143A. Although JAR 1 and mAb502 appeared to have overlapping epitopes, only JAR 1 inhibited binding of fH to fHbp and had human complement-mediated bactericidal activity. mAb502 enhanced fH binding and lacked human complement-mediated bactericidal activity. To control for confounding effects of different mouse IgG subclasses on complement activation, we created chimeric mAbs in which the mouse mAb502 or JAR 1 paratopes were paired with human IgG1 constant regions. While both chimeric mAbs showed similar binding to fHbp, only JAR 1, which inhibited fH binding, had human complement-mediated bactericidal activity.

Conclusions

The lack of human complement-mediated bactericidal activity by anti-fHbp mAb502 appeared to result from an inability to inhibit binding of fH. These results underscore the importance of inhibition of fH binding for anti-fHbp mAb bactericidal activity.

Molecular epidemiology of Neisseria meningitidis serogroup B in Brazil

Background

Neisseria meningitidis serogroup B has been predominant in Brazil, but no broadly effective vaccine is available to prevent endemic meningococcal disease. To understand genetic diversity among serogroup B strains in Brazil, we selected a nationally representative sample of clinical disease isolates from 2004, and a temporally representative sample for the state of São Paulo (1988–2006) for study (n = 372).

Methods

We performed multi-locus sequence typing (MLST) and sequence analysis of five outer membrane protein (OMP) genes, including novel vaccine targets fHbp and nadA.

Results

In 2004, strain B:4:P1.15,19 clonal complex ST-32/ET-5 (cc32) predominated throughout Brazil; regional variation in MLST sequence type (ST), fetA, and porB was significant but diversity was limited for nadA and fHbp. Between 1988 and 1996, the São Paulo isolates shifted from clonal complex ST-41/44/Lineage 3 (cc41/44) to cc32. OMP variation was associated with but not predicted by cc or ST. Overall, fHbp variant 1/subfamily B was present in 80% of isolates and showed little diversity. The majority of nadA were similar to reference allele 1.

Conclusions

A predominant serogroup B lineage has circulated in Brazil for over a decade with significant regional and temporal diversity in ST, fetA, and porB, but not in nadA and fHbp.