Prediction by genetic MATS of 4CMenB vaccine strain coverage of invasive meningococcal serogroup B isolates circulating in Taiwan between 2003 and 2020.

Neisseria meningitidis serogroup B (NmB) strains have diverse antigens, necessitating methods for predicting meningococcal serogroup B (MenB) vaccine strain coverage. The genetic Meningococcal Antigen Typing System (gMATS), a correlate of MATS estimates, predicts strain coverage by the 4-component MenB (4CMenB) vaccine in cultivable and non-cultivable NmB isolates. In Taiwan, 134 invasive, disease-causing NmB isolates were collected in 2003-2020 (23.1%, 4.5%, 5.2%, 29.8%, and 37.3% from individuals aged ≤11 months, 12-23 months, 2-4 years, 5-29 years, and ≥30 years, respectively). NmB isolates were characterized by whole-genome sequencing and vaccine antigen genotyping, and 4CMenB strain coverage was predicted using gMATS. Analysis of phylogenetic relationships with 502 global NmB genomes showed that most isolates belonged to three global hyperinvasive clonal complexes: ST-4821 (27.6%), ST-32 (23.9%), and ST-41/44 (14.9%). Predicted strain coverage by gMATS was 62.7%, with 27.6% isolates covered, 2.2% not covered, and 66.4% unpredictable by gMATS. Age group coverage point estimates ranged from 42.9% (2-4 years) to 66.1% (≤11 months). Antigen coverage estimates and percentages predicted as covered/not covered were highly variable, with higher estimates for isolates with one or more gMATS-positive antigens than for isolates positive for one 4CMenB antigen. In conclusion, this first study on NmB strain coverage by 4CMenB in Taiwan shows 62.7% coverage by gMATS, with predictable coverage for 29.8% of isolates. These could be underestimated since the gMATS calculation does not consider synergistic mechanisms associated with simultaneous antibody binding to multiple targets elicited by multicomponent vaccines or the contributions of minor outer membrane vesicle vaccine components.IMPORTANCEMeningococcal diseases, caused by the bacterium Neisseria meningitidis (meningococcus), include meningitis and septicemia. Although rare, invasive meningococcal disease is often severe and can be fatal. Nearly all cases are caused by six meningococcal serogroups (types), including meningococcal serogroup B. Vaccines are available against meningococcal serogroup B, but the antigens targeted by these vaccines have highly variable genetic features and expression levels, so the effectiveness of vaccination may vary depending on the strains circulating in particular countries. It is therefore important to test meningococcal serogroup B strains isolated from specific populations to estimate the percentage of bacterial strains that a vaccine can protect against (vaccine strain coverage). Meningococcal isolates were collected in Taiwan between 2003 and 2020, of which 134 were identified as serogroup B. We did further investigations on these isolates, including using a method (called gMATS) to predict vaccine strain coverage by the 4-component meningococcal serogroup B vaccine (4CMenB).

Genetic variability of Polish serogroup B meningococci (2010-2016) including the 4CMenB vaccine component genes.

Neisseria meningitidis serogroup B (MenB) has recently become the major cause of invasive meningococcal disease in Poland. Therefore, the purpose of this study was to characterize MenB isolates, responsible for invasive meningococcal disease in 2010-2016, by MLST and sequencing of genes encoding proteins used as 4CMenB vaccine antigens. Two methods of coverage estimation were performed: extrapolation of MATS results of Polish meningococci 2010-2011 (exMATS) and gMATS, which combines genotyping and MATS results. Among 662 isolates 20 clonal complexes (CC) were detected, of which the most frequent were CC32, CC41/44 and CC18, accounting for 31.9%, 16.5% and 12.7%, respectively. A total of 111 combinations of PorA variable regions (VR1/VR2) were found, with P1.7,16 (15.0%) and P1.22,14 (13.6%) being prevalent. Vaccine variant VR2:4 was detected in 7.3% of isolates, mainly representing CC41/44 and non-assigned CC. Eighty five fHbp alleles encoding 74 peptide subvariants were revealed. Subvariant 1.1, a component of 4CMenB, was prevalent (24.2%) and found generally in CC32. Typing of the nhba gene revealed 102 alleles encoding 87 peptides. The most frequent was peptide 3 (22.4%), whereas vaccine peptide 2 was detected in 9.8%, mostly among CC41/44. The nadA gene was detected in 34.0% of isolates and the most prevalent was peptide 1 (variant NadA-1; 71.6%), found almost exclusively in CC32 meningococci. Vaccine peptide 8 (variant NadA-2/3) was identified once. Consequently, 292 completed BAST profiles were revealed. Regarding vaccine coverage, 39.7% of isolates had at least one 4CMenB vaccine variant, but according to exMATS and gMATS the coverage was 83.3% and 86.6%, respectively. In conclusion, Polish MenB (2010-2016) was highly diverse according to MLST and gene alleles encoding 4CMenB vaccine antigens. Some correlations between clonal complexes and variants of examined proteins/BAST profiles were revealed and a high coverage of 4CMenB vaccine was estimated.

Distribution of Neisseria meningitidis serogroup b (NmB) vaccine antigens in meningococcal disease causing isolates in the United States during 2009-2014, prior to NmB vaccine licensure.

OBJECTIVES: Two Neisseria meningitidis serogroup B (NmB) vaccines are licensed in the United States. To estimate their potential coverage, we examined the vaccine antigen diversity among meningococcal isolates prior to vaccine licensure. METHODS: NmB vaccine antigen genes of invasive isolates collected in the U.S. from 2009 to 2014 were characterized by Sanger or whole-genome sequencing. RESULTS: During 2009-2014, the predominant antigen types have remained similar to those reported in 2000-2008 for NmB and 2006-2008 for NmC, NmY, with the emergence of a few new types. FHbp of subfamily B or variant 1 (B/v1) remained prevalent among NmB whereas FHbp of subfamily A or variant 2 and 3 (A/v2-3) were more prevalent among non-NmB. FHbp peptide 1 (B24/1.1) remains the most prevalent type in NmB. Full-length NadA peptide was detected in 26% of isolates, primarily in NmB and NmW. The greatest diversity of NhbA peptides was detected among NmB, with p0005 as the most prevalent type. CONCLUSIONS: The prevalence and diversity of the NmB vaccine antigens have remained stable with common antigen types persisting over time. The data collected prior to NmB vaccine licensure provide the baseline to understand the potential impact of NmB vaccines on antigen diversity and strain coverage.

Outbreak strain characterisation and pharyngeal carriage detection following a protracted group B meningococcal outbreak in adolescents in South-West England.

Between April 2016 and September 2017, four cases of group B meningococcal disease were reported among sixth-form college students in Bristol, UK. Culture and non-culture whole genome sequencing was utilised and demonstrated that the four genomes of the responsible ST-41 strains clustered closely on a sub-lineage of ST-41/44 clonal complex. The outbreak resulted in two fatalities. A distinct social group associated with one of the cases was selected for vaccination with 4CMenB and pharyngeal swabbing. In vitro culturing, multiple real-time PCR assays (sodC, ctrA and siaDB) and a PorA PCR-sequencing assay were used to detect meningococcal colonisation and a carriage rate of 32.6% was observed. Furthermore, a high proportion of the pharyngeal swabs (78.3%) yielded a Factor H-Binding Protein (fHbp) nucleotide allele suggesting that the antigenic gene is prevalent among non-meningococcal flora, most likely Neisseria commensals. This may have implications for fHbp as a vaccine antigen should it be shown to influence bacterial colonisation.

Genetic Meningococcal Antigen Typing System (gMATS): A genotyping tool that predicts 4CMenB strain coverage worldwide.

BACKGROUND: The Meningococcal Antigen Typing System (MATS) was developed to identify meningococcus group B strains with a high likelihood of being covered by the 4CMenB vaccine, but is limited by the requirement for viable isolates from culture-confirmed cases. We examined if antigen genotyping could complement MATS in predicting strain coverage by the 4CMenB vaccine. METHODS: From a panel of 3912 MATS-typed invasive meningococcal disease isolates collected in England and Wales in 2007-2008, 2014-2015 and 2015-2016, and in 16 other countries in 2000-2015, 3481 isolates were also characterized by antigen genotyping. Individual associations between antigen genotypes and MATS coverage for each 4CMenB component were used to define a genetic MATS (gMATS). gMATS estimates were compared with England and Wales human complement serum bactericidal assay (hSBA) data and vaccine effectiveness (VE) data from England. RESULTS: Overall, 81% of the strain panel had genetically predictable MATS coverage, with 92% accuracy and highly concordant results across national panels (Lin's accuracy coefficient, 0.98; root-mean-square deviation, 6%). England and Wales strain coverage estimates were 72-73% by genotyping (66-73% by MATS), underestimating hSBA values after four vaccine doses (88%) and VE after two doses (83%). The gMATS predicted strain coverage in other countries was 58-88%. CONCLUSIONS: gMATS can replace MATS in predicting 4CMenB strain coverage in four out of five cases, without requiring a cultivable isolate, and is open to further improvement. Both methods underestimated VE in England. Strain coverage predictions in other countries matched or exceeded England and Wales estimates.

Potential Coverage of the 4CMenB Vaccine against Invasive Serogroup B Neisseria meningitidis Isolated from 2009 to 2013 in the Republic of Ireland.

Neisseria meningitidis is a common cause of bacterial meningitis in children and young adults worldwide. The 4CMenB vaccine (Bexsero), developed to combat meningococcal serogroup B (MenB) disease, contains subcapsular antigens that may induce immunity against strains of N. meningitidis, regardless of serogroup. Owing to differential levels of expression and peptide diversity in vaccine antigens across meningococcal strains, the meningococcal antigen typing system (MATS) was developed to estimate the potential MenB strain coverage of 4CMenB. Prior to introducing the 4CMenB vaccine into routine use, we sought to estimate the potential 4CMenB coverage against invasive MenB strains isolated in the Republic of Ireland (RoI) over four consecutive epidemiological years. MATS was applied to a panel of 105 invasive MenB strains isolated during July 2009 to June 2013. Sequence data characterizing the multilocus sequence typing (MLST) alleles and the major 4CMenB target peptides were extracted from isolate genome sequence data, hosted in the Bacterial Isolate Sequencing database (BIGSdb). MATS data indicated that 4CMenB may induce protective immunity against 69.5% (95% confidence interval [CI95%], 64.8% to 84.8%) of circulating MenB strains. Estimated coverage was highest against the most prevalent disease-causing lineage, cc41/44, where the most frequently observed sequence types, ST-154 and ST-41 (21% of isolates, collectively), were typically covered by three antigens. No significant temporal trends were observed. Overall, these data provide a baseline of strain coverage prior to the introduction of 4CMenB and indicate that a decrease in invasive meningococcal disease (IMD) is predicted following the introduction of 4CMenB into the routine infant immunization schedule in the RoI.IMPORTANCE The meningococcal antigen typing system (MATS) is an enzyme-linked immunosorbent assay (ELISA) that measures both the levels of expression and the immune reactivity of the three recombinant 4CMenB antigens. Together with PorA variable-region sequence data, this system provides an estimation of how susceptible MenB isolates are to killing by 4CMenB vaccine-induced antibodies. Assays based on subcapsular antigen phenotype analyses, such as MATS, are important in situations where conventional vaccine coverage estimations are not possible. Subcapsular antigens are typically highly diverse across strains, and vaccine coverage estimations would require unfeasibly large efficacy trials and screening of an exhaustive strain panel for antibody functional activity. Here, MATS was applied to all invasive meningococcal serogroup B (MenB) strains isolated over four consecutive epidemiological years (n = 105) and predicted reasonably high 4CMenB vaccine coverage in the Republic of Ireland.

Phase Variation of NadA in Invasive Neisseria meningitidis Isolates Impacts on Coverage Estimates for 4C-MenB, a MenB Vaccine.

A recombinant NadA protein is one of the four major protective antigens of 4C-MenB (Bexsero), a vaccine developed for serogroup B Neisseria meningitidis (MenB). The meningococcal antigen typing system (MATS) is utilized as a high-throughput assay for assessing the invasive MenB strain coverage of 4C-MenB. Where present, the nadA gene is subject to phase-variable changes in transcription due to a 5'TAAA repeat tract located in a regulatory region. The promoter-containing intergenic region (IGR) sequences and 5'TAAA repeat numbers were determined for 906 invasive meningococcal disease isolates possessing the nadA gene. Exclusion of the 5'TAAA repeats reduced the number of IGR alleles from 82 to 23. Repeat numbers were associated with low and high levels of NadA expression by Western blotting and enzyme-linked immunosorbent assay (ELISA). Low-expression repeat numbers were present in 83% of 179 MenB isolates with NadA-2/3 or NadA-1 peptide variants and 68% of 480 MenW ST-11 complex isolates with NadA-2/3 peptide variants. For isolates with vaccine-compatible NadA variants, 93% of MATS-negative isolates were associated with low-expression repeat numbers, whereas 63% of isolates with MATS relative potency (RP) scores above the 95% confidence interval for the positive bactericidal threshold had high-expression repeat numbers. Analysis of 5'TAAA repeat numbers has potential as a rapid, high-throughput method for assessing strain coverage for the NadA component of 4C-MenB. A key application will be assessing coverage in meningococcal disease cases where confirmation is by PCR only and MATS cannot be applied.

Prevalence and genetic characteristics of 4CMenB and rLP2086 vaccine candidates among Neisseria meningitidis serogroup B strains, China.

OBJECTIVE: To systematically investigate the prevalence and genetic characteristics of 4CMenB and rLP2086 vaccine candidates among Neisseria meningitidis serogroup B (NmB) in China. METHODS: A total of 485 NmB strains isolated in 29 provinces of China between 1968 and 2016 were selected from the culture collection of the national reference laboratory according to the isolation year, location, and source. Multi-locus sequence typing (MLST) and porA gene sequencing were performed on all 485 study strains; PCR was used to detect the fHbp, nadA, and nhba gene of 432 strains; positive amplification products from the fHbp and nadA genes from all strains, as well as those of the nhba gene from 172 representative strains, were sequenced. RESULTS: MLST results showed that the predominant (putative) clonal complexes (CCs) of NmB isolates have changed over time in China. While strains that could not be assigned to existing (p)CCs were the biggest proportion, CC4821 was the most prevalent lineage (36.0%) since 2005. PCR and sequence analysis revealed that the 4CMenB and rLP2086 vaccine candidates were highly diverse. Respectively, 152 PorA genotypes and 83 VR2 sequences were identified with significant diversity within a single CC; the complete nadA gene was found in ten of 432 study strains; fHbp was present in most strains (422/432) with variant 2 predominating (82.9%) in both patient- and carrier- derived isolates; almost all strains harbored the nhba gene while sequences were diverse. CONCLUSIONS: With regards to clonal lineages and vaccine candidate proteins, NmB isolates from China were generally diverse. Further studies should be performed to evaluate the cross-protection of present vaccines against Chinese NmB strains.

Frequent capsule switching in 'ultra-virulent' meningococci - Are we ready for a serogroup B ST-11 complex outbreak?

The meningococcal ST-11 complex (cc11) causes large invasive disease outbreaks with high case fatality rates, such as serogroup C (MenC) epidemics in industrialised nations in the 1990s and the serogroup W epidemic currently expanding globally. Glycoconjugate vaccines are available for serogroups A, C, W and Y. Broad coverage protein-based vaccines have recently been licensed against serogroup B meningococci (MenB), however, these do not afford universal MenB protection. Capsular switching from MenC to MenB among cc11 organisms is concerning because a large MenB cc11 (B:cc11) outbreak has the potential to cause significant morbidity and mortality. This study aimed to assess the potential for licensed and developmental non-capsular meningococcal vaccines to protect against B:cc11. The population structure and vaccine antigen distribution was determined for a panel of >800 geo-temporally diverse, predominantly MenC cc11 and B:cc11 genomes. The two licensed vaccines potentially protect against many but not all B:cc11 meningococci. Furthermore, strain coverage by these vaccines is often due to a single vaccine antigen and both vaccines are highly susceptible to vaccine escape owing to the apparent dispensability of key proteins used as vaccine antigens. cc11 strains with MenB and MenC capsules warrant special consideration when formulating future non-capsular meningococcal vaccines.

Serum Bactericidal Antibody Responses of Adults Immunized with the MenB-4C Vaccine against Genetically Diverse Serogroup B Meningococci.

MenB-4C is a meningococcal vaccine for the prevention of serogroup B disease. The vaccine contains factor H binding protein (FHbp) and three other antigens that can elicit serum bactericidal antibodies (SBA). For vaccine licensure, efficacy was inferred from the SBA responses against three antigen-specific indicator strains. The relation between those results and broad protection against circulating genetically diverse strains is not known. Twenty adults were immunized with two doses of MenB-4C given 1 to 2 months apart. SBA activity against 3 reference strains and 15 serogroup B test strains (6 from college outbreaks) was measured. Compared to the preimmunization titers, 70%, 95%, and 95% of subjects had ≥4-fold increases in the titers of anti-PorA P1.4, anti-NadA, and anti-FHbp antibodies against the reference strains, respectively. In contrast, only 25 to 45% of the subjects had ≥4-fold increases in responses to 10 of the 15 test strains, including 8 that expressed one to three of the antigens in the vaccine. At 1 month, the majority of subjects with <4-fold titer increases had serum titers of ≥1:4, which are considered sufficient for protection. However, the titers against four strains declined to <1:4 by 4 to 6 months in one-third to greater than 50% of the subjects tested. Clinically relevant isolates are often more resistant to SBA than the indicator strains used to measure antigen-specific SBA. A working model is that the percentage of subjects with titers of ≥1:4 at 1 month postimmunization correlates with short-term protection against that strain, whereas the percentage of subjects with ≥4-fold titer increases represents a more robust response. (The protocol used at the Oxford Vaccine Group has been registered at ClinicalTrials.gov under registration no. NCT02398396.).

Expression of factor H binding protein in meningococcal strains can vary at least 15-fold and is genetically determined.

Factor H binding protein (fHbp) is a lipoprotein of Neisseria meningitidis important for the survival of the bacterium in human blood and a component of two recently licensed vaccines against serogroup B meningococcus (MenB). Based on 866 different amino acid sequences this protein is divided into three variants or two families. Quantification of the protein is done by immunoassays such as ELISA or FACS that are susceptible to the sequence variation and expression level of the protein. Here, selected reaction monitoring mass spectrometry was used for the absolute quantification of fHbp in a large panel of strains representative of the population diversity of MenB. The analysis revealed that the level of fHbp expression can vary at least 15-fold and that variant 1 strains express significantly more protein than variant 2 or variant 3 strains. The susceptibility to complement-mediated killing correlated with the amount of protein expressed by the different meningococcal strains and this could be predicted from the nucleotide sequence of the promoter region. Finally, the absolute quantification allowed the calculation of the number of fHbp molecules per cell and to propose a mechanistic model of the engagement of C1q, the recognition component of the complement cascade.

Lipooligosaccharide Structures of Invasive and Carrier Isolates of Neisseria meningitidis Are Correlated with Pathogenicity and Carriage.

The degree of phosphorylation and phosphoethanolaminylation of lipid A on neisserial lipooligosaccharide (LOS), a major cell-surface antigen, can be correlated with inflammatory potential and the ability to induce immune tolerance in vitro. On the oligosaccharide of the LOS, the presence of phosphoethanolamine and sialic acid substituents can be correlated with in vitro serum resistance. In this study, we analyzed the structure of the LOS from 40 invasive isolates and 25 isolates from carriers of Neisseria meningitidis without disease. Invasive strains were classified as groups 1-3 that caused meningitis, septicemia without meningitis, and septicemia with meningitis, respectively. Intact LOS was analyzed by high resolution matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Prominent peaks for lipid A fragment ions with three phosphates and one phosphoethanolamine were detected in all LOS analyzed. LOS from groups 2 and 3 had less abundant ions for highly phosphorylated lipid A forms and induced less TNF-α in THP-1 monocytic cells compared with LOS from group 1. Lipid A from all invasive strains was hexaacylated, whereas lipid A of 6/25 carrier strains was pentaacylated. There were fewer O-acetyl groups and more phosphoethanolamine and sialic acid substitutions on the oligosaccharide from invasive compared with carrier isolates. Bioinformatic and genomic analysis of LOS biosynthetic genes indicated significant skewing to specific alleles, dependent on the disease outcome. Our results suggest that variable LOS structures have multifaceted effects on homeostatic innate immune responses that have critical impact on the pathophysiology of meningococcal infections.

High predicted strain coverage by the multicomponent meningococcal serogroup B vaccine (4CMenB) in Poland.

Neisseria meningitidis of serogroup B (MenB) is currently responsible for more than 70% of cases of invasive meningococcal disease (IMD) in Poland and Europe as a whole. The aim of this study was to estimate strain coverage of a multicomponent meningococcal serogroup B vaccine (4CMenB) in Poland; the meningococcal antigen typing system (MATS) was used to test a panel of 196 invasive MenB strains isolated in Poland in 2010 and 2011. The strains were also characterized by MLST and sequencing of porA, factor H-binding protein (fHbp), Neisserial heparin-binding antigen (nhba) and Neisserial adhesin A (nadA) genes. MATS and molecular data were analyzed independently and in combination. The MATS results predicted that 83.7% (95% CI: 78.6-91.0%) of isolates would be covered by the 4CMenB vaccine; 59.2% by one vaccine antigen, 19.9% by two and 4.6% by three antigens. Coverage by each antigen was as follows: fHbp 73.0% (95% CI: 68.9-77.5%), NHBA 28.6% (95% CI: 13.3-47.4%), NadA 1.0% (95% CI: 1.0-2.0%) and PorA 10.2%. Molecular analysis revealed that the most frequent clonal complexes (ccs) were cc32 (33.2%), cc18 (17.9%) and cc41/44 (15.8%) with estimated coverage of 98.5%, 88.6% and 93.5%, respectively. Consistent with findings for other European countries, our study predicts high coverage by the 4CMenB vaccine in Poland.

Meningococcal Antigen Typing System Development and Application to the Evaluation of Effectiveness of Meningococcal B Vaccine and Possible Use for Other Purposes.

Development of the 4-component meningococcal serogroup B vaccine (4CMenB) has required new assays for the reliable evaluation of the expression and cross-reactivity of those specific antigen variants that are predicted to be targeted by bactericidal antibodies elicited by the vaccine in different isolates. Existing laboratory techniques, such as multilocus sequence typing, are poorly suited to this purpose, since they do not provide information on the contribution of single vaccine components and therefore cannot be applied to estimate the potential coverage of the multicomponent vaccine. The hSBA, the only correlate of protection against invasive meningococcal disease accepted thus far, cannot conveniently be used to test large number of strains. To overcome these issues, the meningococcal antigen typing system (MATS) has been specifically developed in order to predict 4CMenB coverage of individual meningococcus serogroup B strains. To date, MATS has proved advantageous for several reasons, including its ability to assess both qualitative and quantitative aspects of surface antigens of single strains in a highly reproducible, rapid, and resource-saving manner, while its shortcomings include a possible underestimation of 4CMenB coverage and the use of pooled sera to calculate the positive bactericidal threshold. This paper provides an overview of MATS development and its field application.

Reduced turnaround time and improved diagnosis of invasive serogroup B Neisseria meningitidis and Streptococcus pneumoniae infections using a lyophilized quadruplex quantitative PCR.

Since 1996 the Meningococcal Reference Unit (MRU) in Manchester has provided a national service for PCR confirmation of meningococcal and pneumococcal disease. Neisseria meningitidis serogroup B is predominant in the UK, accounting for >60% of cases. In response to this, the MRU has developed a quadruplex quantitative PCR that detects N. meningitidis capsule transporter (ctrA), serogroup B sialyltransferase (siaDB), Streptococcus pneumoniae pneumolysin (ply) and an internal control. The assay was prepared in a ready-to-use lyophilized format by Applied Biosystems. Laboratory validation showed excellent performance in a specificity panel of 52 isolates and improved detection in comparison with the routine assay. Testing of 244 patient samples showed sensitivity of 93% [95% confidence interval (CI): 88-98%] for the ctrA assay, 95% (95% CI: 91-100%) for the siaDB assay and 100% (95% CI: 95-100%) for the ply assay. Specificity was 100% (95% CI: 98-100%) for both meningococcal targets and 95% (95% CI: 92-98%) for ply. The quadruplex also retained high performance in mixed samples and had acceptable reproducibility. After introduction of the quadruplex into routine use the turnaround time for N. meningitidis group B PCR confirmation reduced from 37 to 29 h and the internal control has proved useful for detecting inhibitory samples. The quadruplex assay provides rapid group B confirmation of meningococcal positive samples, enabling timely public health interventions for the most common disease-causing meningococcal serogroup in the UK.

Genomic resolution of an aggressive, widespread, diverse and expanding meningococcal serogroup B, C and W lineage.

OBJECTIVES: Neisseria meningitidis is a leading cause of meningitis and septicaemia. The hyperinvasive ST-11 clonal complex (cc11) caused serogroup C (MenC) outbreaks in the US military in the 1960s and UK universities in the 1990s, a global Hajj-associated serogroup W (MenW) outbreak in 2000-2001, and subsequent MenW epidemics in sub-Saharan Africa. More recently, endemic MenW disease has expanded in South Africa, South America and the UK, and MenC cases have been reported among European and North American men who have sex with men (MSM). Routine typing schemes poorly resolve cc11 so we established the population structure at genomic resolution. METHODS: Representatives of these episodes and other geo-temporally diverse cc11 meningococci (n = 750) were compared across 1546 core genes and visualised on phylogenetic networks. RESULTS: MenW isolates were confined to a distal portion of one of two main lineages with MenB and MenC isolates interspersed elsewhere. An expanding South American/UK MenW strain was distinct from the 'Hajj outbreak' strain and a closely related endemic South African strain. Recent MenC isolates from MSM in France and the UK were closely related but distinct. CONCLUSIONS: High resolution 'genomic' multilocus sequence typing is necessary to resolve and monitor the spread of diverse cc11 lineages globally.

Sequence Type 4821 Clonal Complex Serogroup B Neisseria meningitidis in China, 1978-2013.

Serogroup B Neisseria meningitidis strains belonging to sequence type 4821 clonal complex (CC4821), a hyperinvasive lineage first identified for serogroup C in 2003, have been increasingly isolated in China. We characterized the outer membrane protein genes of 48 serogroup B and 214 serogroup C strains belonging to CC4821 and analyzed the genomic sequences of 22 strains. Four serogroup B strains had porin A (i.e., PorA), PorB, and ferric enterobactin transport (i.e., FetA) genotypes identical to those for serogroup C. Phylogenetic analysis of the genomic sequences showed that the 22 CC4821 strains from patients and healthy carriers were unevenly clustered into 2 closely related groups; each group contained serogroup B and C strains. Serogroup B strains appeared variable at the capsule locus, and several recombination events had occurred at uncertain breakpoints. These findings suggest that CC4821 serogroup C N. meningitidis is the probable origin of highly pathogenic CC4821 serogroup B strains.

Diversity of Greek meningococcal serogroup B isolates and estimated coverage of the 4CMenB meningococcal vaccine.

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.

Variability of genes encoding surface proteins used as vaccine antigens in meningococcal endemic and epidemic strain panels from Norway.

Surface-expressed protein antigens such as factor H-binding protein (fHbp), Neisserial adhesin A (NadA), Neisserial heparin-binding antigen (NHBA) and Porin protein A (PorA); all express sequence variability that can affect their function as protective immunogens when used in meningococcal serogroup B vaccines like the recently-approved 4CMenB (Bexsero(®)). We assessed the sequence variation of genes coding for these proteins and two additional proteins ("fusion partners" to fHbp and NHBA) in pathogenic isolates from a recent low incidence period (endemic situation; 2005-2006) in Norway. Findings among strains from this panel were contrasted to what was found among isolates from a historic outbreak (epidemic situation; 1985-1990). Multilocus sequence typing revealed 14 clonal complexes (cc) among the 66 endemic strains, while cc32 vastly predominated in the 38-strain epidemic panel. Serogroup B isolates accounted for 50/66 among endemic strains and 28/38 among epidemic strains. Potential strain-coverage ("sequence match") for the 4CMenB vaccine was identified among the majority (>70%) of the endemic serogroup B isolates and all of the epidemic serogroup B isolates evaluated. Further information about the degree of expression, surface availability and the true cross-reactivity for the vaccine antigens will be needed to fully characterize the clinical strain-coverage of 4CMenB in various geographic and epidemiological situations.