Predicted Strain Coverage of a New Meningococcal Multicomponent Vaccine (4CMenB) in Spain: Analysis of the Differences with Other European Countries

Genomic Surveillance of Invasive Meningococcal Disease During a National MenW Outbreak in Australia, 2017-2018

Background

In Australia, invasive meningococcal disease (IMD) incidence rapidly increased between 2014 and 2017 due to rising serogroup W (MenW) and MenY infections. We aimed to better understand the genetic diversity of IMD during 2017 and 2018 using whole genome sequencing data.

Methods

Whole genome sequencing data from 440 Australian IMD isolates collected during 2017 and 2018 and 1737 international MenW:CC11 isolates collected in Europe, Africa, Asia, North America, and South America between 1974 and 2020 were used in phylogenetic analyses; genetic relatedness was determined from single-nucleotide polymorphisms.

Results

Australian isolates were as follows: 181 MenW (41%), 144 MenB (33%), 88 MenY (20%), 16 MenC (4%), 1 MenW/Y (0.2%), and 10 nongenogroupable (2%). Eighteen clonal complexes (CCs) were identified, and 3 (CC11, CC23, CC41/44) accounted for 78% of isolates (343/440). These CCs were associated with specific serogroups: CC11 (n = 199) predominated among MenW (n = 181) and MenC (n = 15), CC23 (n = 80) among MenY (n = 78), and CC41/44 (n = 64) among MenB (n = 64). MenB isolates were highly diverse, MenY were intermediately diverse, and MenW and MenC isolates demonstrated the least genetic diversity. Thirty serogroup and CC-specific genomic clusters were identified. International CC11 comparison revealed diversification of MenW in Australia.

Conclusions

Whole genome sequencing comprehensively characterized Australian IMD isolates, indexed their genetic variability, provided increased within-CC resolution, and elucidated the evolution of CC11 in Australia.

Effectiveness of a Meningococcal Group B Vaccine (4CMenB) in Children

BACKGROUND

In September 2015, the four-component, protein-based meningococcal serogroup B vaccine (4CMenB; Bexsero) became available for private purchase in Spain.

METHODS

We conducted a nationwide matched case-control study to assess the effectiveness of 4CMenB in preventing invasive meningococcal disease in children. The study included all laboratory-confirmed cases of invasive meningococcal disease in children younger than 60 months of age between October 5, 2015, and October 6, 2019, in Spain. Each case patient was matched with four controls according to date of birth and province. 4CMenB vaccination status of the case patients and controls was compared with the use of multivariate conditional logistic regression.

RESULTS

We compared 306 case patients (243 [79.4%] with serogroup B disease) with 1224 controls. A total of 35 case patients (11.4%) and 298 controls (24.3%) had received at least one dose of 4CMenB. The effectiveness of complete vaccination with 4CMenB (defined as receipt of at least 2 doses, administered in accordance with the manufacturer's recommendations) was 76% (95% confidence interval [CI], 57 to 87) against invasive meningococcal disease caused by any serogroup, and partial vaccination was 54% (95% CI, 18 to 74) effective. Complete vaccination resulted in an effectiveness of 71% (95% CI, 45 to 85) against meningococcal serogroup B disease. Vaccine effectiveness with at least one dose of 4CMenB was 64% (95% CI, 41 to 78) against serogroup B disease and 82% (95% CI, 21 to 96) against non-serogroup B disease. With the use of the genetic Meningococcal Antigen Typing System, serogroup B strains that were expected to be covered by 4CMenB were detected in 44 case patients, none of whom had been vaccinated.

CONCLUSIONS

Complete vaccination with 4CMenB was found to be effective in preventing invasive disease by serogroup B and non-serogroup B meningococci in children younger than 5 years of age.

Population structure of Neisseria meningitidis ST-9493 identified in Colombian isolates

INTRODUCTION

Neisseria meningitidis is associated with invasive infections causing high mortality rates. The objective of this study was to describe the population structure of Colombian invasive isolates with ST-9493, a potentially emerging clonal group in the country.

METHODS

The complete genomes of 34 invasive isolates of serogroup B with ST-9493 and its variants at one or two loci were sequenced by Illumina to describe the phenotypic and genotypic characteristics of these isolates.

RESULTS

The relationship of a clonal group associated with ST-136 CC41/44 was phylogenetically established, identifying two main clades composed of isolates from an outbreak or endemic. The most frequent alleles and peptides included porA 17, porB 44, fHbp 2.24, NHBA 10, and the FetA F5-17 variant. Most of the isolates were susceptible to the antibiotics evaluated.

CONCLUSION

This study shows that meningococcal isolates with ST-9493 are an autochthonous clonal group with population dynamics and the capacity to cause endemic and epidemic meningococcal disease in Colombia.

Genetic Features of a Representative Panel of 110 Meningococcal B Isolates to Assess the Efficacy of Meningococcal B Vaccines

Predictions of vaccine efficacy against Neisseria meningitidis serogroup B (NmB) disease are hindered by antigenic variability, limiting the representativeness of individual NmB isolates. A qualitative human serum bactericidal assay using endogenous complements of individual subjects (enc-hSBA) enables large panels of NmB isolates to be tested. A 110-isolate panel was randomly selected from 442 invasive NmB isolates from United States cases reported to the Centers for Disease Control (CDC) from 2000 to 2008. Typing analyses confirmed the 110-isolate panel is representative of the 442 isolates. The genetic features of the 110-isolate panel were compared against over 4,200 invasive NmB isolates collected from 2000 to 2018 in the United States, Australia, Canada, and nine European countries. Clonal complexes in the 110-isolate panel are also present in each geographical region; cumulative percentages show that these account for around 81% of the clonal complexes found in NmB isolates in other panels. For the antigens (fHbp, NHBA, PorA1.4, NadA) included in the currently licensed meningococcal serogroup B (MenB) vaccines, specifically considering the presence of at least one antigen with a matched genotype, the 110-isolate panel represents approximately 89% of the NmB isolates circulating worldwide, ranging from 87% for the European isolates to 95% and 97% for NmB isolates in the United States and Australia, respectively. The 110-isolate panel includes the most prevalent clonal complexes and genetic variants of MenB vaccine antigens found in a multinational collection of invasive NmB isolates. This panel is useful for assessing the efficacy of MenB vaccines in clinical trials worldwide.

IMPORTANCENeisseria meningitidis serogroup B (NmB) is a major cause of invasive meningococcal disease (IMD). Predicting the effectiveness of vaccines against NmB is difficult because NmB is an uncommon disease and because antigens targeted by meningococcal serogroup B (MenB) vaccines have highly variable genetic features and expression levels. Therefore, a large number of NmB isolates from different regions would need to be tested to comprehensively assess vaccine effectiveness. We examined a panel of 110 isolates obtained from NmB IMD cases in the United States and compared the genetic features of this panel with those of panels from different countries around the world. We found the 110-isolate panel included the most common clonal complexes and genetic variants of MenB vaccine antigens that exist in the global collections of invasive NmB isolates. This confirms the value of the NmB 110-isolate panel in understanding the effectiveness of MenB vaccines in clinical trials worldwide.

Translating meningococcal serogroup B vaccines for healthcare professionals

INTRODUCTION

Vaccination is an effective strategy to combat invasive meningococcal disease (IMD). Vaccines against the major disease-causing meningococcal serogroups are available; however, development of vaccines against serogroup B faced particular challenges, including the inability to target traditional meningococcal antigens (i.e. polysaccharide capsule) and limited alternative antigens due to serogroup B strain diversity. Two different recombinant, protein-based, serogroup B (MenB) vaccines that may address these challenges are currently available. These vaccines have been extensively evaluated in pre-licensure safety and immunogenicity trials, and recently in real-world studies on effectiveness, safety, and impact on disease burden.

AREAS COVERED

This review provides healthcare professionals, particularly pediatricians, an overview of currently available MenB vaccines, including development strategies and evaluation of coverage.

EXPERT OPINION

Overall, recombinant MenB vaccines are valuable tools for healthcare professionals to protect patients against IMD. Their development required innovative design approaches that overcame challenging hurdles and identified novel protein antigen targets; however, important distinctions in the approaches used in their development, evaluation, and administration exist and many unanswered questions remain. Healthcare providers frequently prescribing MenB vaccines are challenged to keep abreast of these differences to ensure patient protection against this serious disease.

High coverage of diverse invasive meningococcal serogroup B strains by the 4-component vaccine 4CMenB in Australia, 2007-2011: Concordant predictions between MATS and genetic MATS

Meningococcal serogroup B (MenB) accounts for an important proportion of invasive meningococcal disease (IMD). The 4-component vaccine against MenB (4CMenB) is composed of factor H binding protein (fHbp), neisserial heparin-binding antigen (NHBA), Neisseria adhesin A (NadA), and outer membrane vesicles of the New Zealand strain with Porin 1.4. A meningococcal antigen typing system (MATS) and a fully genomic approach, genetic MATS (gMATS), were developed to predict coverage of MenB strains by 4CMenB. We characterized 520 MenB invasive disease isolates collected over a 5-year period (January 2007-December 2011) from all Australian states/territories by multilocus sequence typing and estimated strain coverage by 4CMenB. The clonal complexes most frequently identified were ST-41/44 CC/Lineage 3 (39.4%) and ST-32 CC/ET-5 CC (23.7%). The overall MATS predicted coverage was 74.6% (95% coverage interval: 61.1%-85.6%). The overall gMATS prediction was 81.0% (lower-upper limit: 75.0-86.9%), showing 91.5% accuracy compared with MATS. Overall, 23.7% and 13.1% (MATS) and 26.0% and 14.0% (gMATS) of isolates were covered by at least 2 and 3 vaccine antigens, respectively, with fHbp and NHBA contributing the most to coverage. When stratified by year of isolate collection, state/territory and age group, MATS and gMATS strain coverage predictions were consistent across all strata. The high coverage predicted by MATS and gMATS indicates that 4CMenB vaccination may have an impact on the burden of MenB-caused IMD in Australia. gMATS can be used in the future to monitor variations in 4CMenB strain coverage over time and geographical areas even for non-culture confirmed IMD cases.

Molecular characterization of invasive serogroup B Neisseria meningitidis isolates from Spain during 2015-2018: Evolution of the vaccine antigen factor H binding protein (FHbp)

Studies of meningococcal genetic population structure, including the potential associations between surface proteins variants and clonal complexes, are important to understand how new protein MenB vaccines might impact in specific scenarios. With the aim to analyze the diversity of Spanish invasive MenB strains, and genetic variability of the fHbp vaccine antigen, all MenB isolates received at National Reference Laboratory (NRL) from 2015 to 2018 were molecularly characterized.

MATERIAL AND METHODS

108, 103, 87 and 112 invasive MenB strains isolated during 2015-2018, respectively, were received at NRL. The strains were whole genome sequenced, and porA, fetA, MLST and fHbp variability was analyzed. Potential impact on MenB vaccines coverage was also assessed.

RESULTS

A total of 42, 38 and 3 different FHbp subfamily A, B and A/B hybrid peptides, respectively, were found. FHbp subfamily A peptides were harboured by most of the strains (65.9%), being the most prevalent peptide 45 which was associated with genosubtype 22,14 and cc213. FHbp subfamily B peptides were harboured by 32.4% of the strains, and 6 strains harbouring subfamily A/B hybrid peptides were also found. The 64.15% of the strains showed FHbp variants "exact-match" or "cross-reactive" to the FHbp variants included in rLP2086 vaccine according to hSBA assays in the rLP2086 clinical development, and 15.85% showed FHbp peptides defined as predictors of FHbp-coverage for 4CMenB vaccine by gMATS.

CONCLUSIONS

Due to invasive meningococcal strains temporal variability (eg prevalence of the cc213 increased from 3.6% in 2007 to 33% in 2018) affecting to the presence and distribution of the vaccine antigens, continuous detailed meningococcal surveillance and monitoring of the vaccine antigens is needed to determine the degree and durability of coverage provided by these protein vaccine.

Genomic surveillance of Neisseria meningitidis serogroup B invasive strains: Diversity of vaccine antigen types, Brazil, 2016-2018

Background

Neisseria meningitidis serogroup B remains a prominent cause of invasive meningococcal disease (IMD) in Brazil. Because two novel protein-based vaccines against serogroup B are available, the main purpose of this study was to provide data on the diversity and distribution of meningococcal vaccine antigen types circulating in Brazil.

Methodology

Genetic lineages, vaccine antigen types, and allele types of antimicrobial-associated resistance genes based on whole-genome sequencing of a collection of 145 Neisseria meningitidis serogroup B invasive strains recovered in Brazil from 2016 to 2018 were collected.

Results

A total of 11 clonal complexes (ccs) were identified among the 145 isolates, four of which were predominant, namely, cc461, cc35, cc32, and cc213, accounting for 72.0% of isolates. The most prevalent fHbp peptides were 24 (subfamily A/variant 2), 47 (subfamily A/variant 3), 1 (subfamily B/variant 1) and 45 (subfamily A/variant 3), which were predominantly associated with cc35, cc461, cc32, and cc213, respectively. The NadA peptide was detected in only 26.2% of the isolates. The most frequent NadA peptide 1 was found almost exclusively in cc32. We found seven NHBA peptides that accounted for 74.5% of isolates, and the newly described peptide 1390 was the most prevalent peptide exclusively associated with cc461. Mutated penA alleles were detected in 56.5% of the isolates, whereas no rpoB and gyrA mutant alleles were found.

Conclusion

During the study period, changes in the clonal structure of circulating strains were observed, without a predominance of a single hyperinvasive lineage, indicating that an epidemiologic shift has occurred that led to a diversity of vaccine antigen types in recent years in Brazil.

Meningococcal Deduced Vaccine Antigen Reactivity (MenDeVAR) Index: a Rapid and Accessible Tool That Exploits Genomic Data in Public Health and Clinical Microbiology Applications

As microbial genomics makes increasingly important contributions to clinical and public health microbiology, the interpretation of whole-genome sequence data by nonspecialists becomes essential. In the absence of capsule-based vaccines, two protein-based vaccines have been used for the prevention of invasive serogroup B meningococcal disease (IMD) since their licensure in 2013 and 2014. These vaccines have different components and different levels of coverage of meningococcal variants. Hence, decisions regarding which vaccine to use in managing serogroup B IMD outbreaks require information about the index case isolate, including (i) the presence of particular vaccine antigen variants, (ii) the expression of vaccine antigens, and (iii) the likely susceptibility of its antigen variants to antibody-dependent bactericidal killing.

As microbial genomics makes increasingly important contributions to clinical and public health microbiology, the interpretation of whole-genome sequence data by nonspecialists becomes essential. In the absence of capsule-based vaccines, two protein-based vaccines have been used for the prevention of invasive serogroup B meningococcal disease (IMD) since their licensure in 2013 and 2014. These vaccines have different components and different levels of coverage of meningococcal variants. Hence, decisions regarding which vaccine to use in managing serogroup B IMD outbreaks require information about the index case isolate, including (i) the presence of particular vaccine antigen variants, (ii) the expression of vaccine antigens, and (iii) the likely susceptibility of its antigen variants to antibody-dependent bactericidal killing. To obtain this information requires a multitude of laboratory assays, impractical in real-time clinical settings, where the information is most urgently needed. To facilitate assessment for public health and clinical purposes, we synthesized genomic and experimental data from published sources to develop and implement the Meningococcal Deduced Vaccine Antigen Reactivity (MenDeVAR) Index, which is publicly available on PubMLST (https://pubmlst.org). Using whole-genome sequences or individual gene sequences obtained from IMD isolates or clinical specimens, the MenDeVAR Index provides rapid evidence-based information on the presence and possible immunological cross-reactivity of different meningococcal vaccine antigen variants. The MenDeVAR Index enables practitioners who are not genomics specialists to assess the likely reactivity of vaccines for individual cases, outbreak management, or the assessment of public health vaccine programs. The MenDeVAR Index has been developed in consultation with, but independently of, both the 4CMenB (Bexsero; GSK) and rLP2086 (Trumenba; Pfizer, Inc.) vaccine manufacturers.

Epidemiological profile of Neisseria meningitidis in Casablanca, Morocco: 2010-2019

Surveillance of invasive meningococcal diseases (IMD) must be carried out regularly and continuously in order to detect the emergence of strains of reduced susceptibility to antibiotics for therapeutic and prophylactic use and the appearance of new invasive clones. Molecular-typing approaches allow reliable traceability and powerful epidemiological analysis. This is an epidemiological study of Neisseria meningitidis causing meningitis in Casablanca, Morocco. The grouping was confirmed by PCR mainly on the isolates from cerebrospinal fluid (CSF). A total of 245 confirmed isolates of N .meningitidis were obtained between 2010 and 2019 of which 93 % are of group B. Overall, 24 % of all the isolates have a reduced susceptibility to penicillin G, but no resistance to penicillin G has been reported. All the isolated strains are susceptible to third-generation cephalosporins (3GCs). Genotyping by multilocus sequence typing (MLST) of a selection of 18 strains showed that the majority of isolates belong to the invasive clonal complex CC 32(9/18) followed by the CC 41/44(3/18).

Meningococcal Serogroup B Disease in Vaccinated Children

BACKGROUND

Neisseria meningitidis serogroup B (MenB) is the most frequent cause of invasive meningococcal disease (IMD) in Spain. The multicomponent vaccine against MenB (4CMenB) was approved in Spain in January 2014.

METHODS

We present 4 cases of children who developed MenB-associated IMD despite previous vaccination with 4CMenB. Extensive immunologic diagnostic work-up was performed in order to rule out any immunodeficiency. Also, molecular characterization of the MenB strain was conducted to determine whether bacterial antigens matched vaccine antigens.

RESULTS

Among the 4 patients (2 girls), 2 had previous risk factors for IMD (recurrent bacterial meningitis of unknown origin and treatment with eculizumab). All patients developed meningitis, but only 2 developed septic shock; they were all cured without sequelae. No other primary or secondary immunodeficiencies were detected. MenB sequence type 213 was identified in 3 cases. With the exception of neisserial heparin-binding antigen peptide 465 present in 1 isolate, the rest of the isolated strains harbored vaccine antigen variants that did not match antigen variants included in the vaccine.

CONCLUSIONS

We present 4 children who developed MenB-associated IMD despite previous vaccination with 4CMenB. In 2 cases, the antibodies induced by 4CMenB likely were not effective against the isolated strains. A high level of suspicion for IMD seems advisable regardless of the patient's vaccination history.

Methods to evaluate serogroup B meningococcal vaccines: From predictions to real-world evidence

Serogroup B meningococci (MenB) remain a prominent cause of invasive meningococcal disease (IMD). The protein-based multicomponent 4CMenB and the bivalent MenB-FHbp are the only currently available vaccines against MenB-caused IMD. Efficacy studies are not possible, due to the low incidence of IMD. Therefore, the vaccines' immunogenicity has been evaluated against several target strains chosen to quantify complement-mediated killing induced by each vaccine component in the serum bactericidal antibody assay. However, due to the wide genetic diversity and different expression levels of vaccine antigens across MenB strains, vaccine performance may differ from one strain to another. Here, we review the methods used to predict MenB strain coverage for 4CMenB and MenB-FHbp. Phenotypic assays such as the meningococcal antigen typing system (MATS, 4CMenB-specific) and the flow cytometric meningococcal antigen surface expression assay (MEASURE; MenB-FHbp-specific) were developed. Genomic approaches are also available, such as genetic MATS (gMATS) and the Bexsero antigen sequence type (BAST) scheme, both 4CMenB-specific. All methods allow tentative predictions of coverage across MenB strains, including that afforded by each vaccine antigen, and are rapid and reproducible. Real-world data on vaccine effectiveness are needed to confirm predictions obtained by these methods.

Culture-Confirmed Invasive Meningococcal Disease in Canada, 2010 to 2014: Characterization of Serogroup B Neisseria meningitidis Strains and Their Predicted Coverage by the 4CMenB Vaccine

Laboratory surveillance of invasive meningococcal disease (IMD) is important to our understanding of the evolving nature of the Neisseria meningitidis strain types causing the disease and the potential coverage of disease strains by the newly developed vaccines. This study examined the molecular epidemiology of culture-confirmed IMD cases in Canada by examining the strain types and the potential coverage of a newly licensed 4CMenB vaccine on Canadian serogroup B N. meningitidis strains. The strain types identified in different parts of Canada appeared to be unique as well as their predicted coverage by the 4CMenB vaccine. These data were compared to data obtained from previous studies done in Canada and elsewhere globally. For effective control of IMD, laboratory surveillance of this type was found to be essential and useful to understand the dynamic nature of this disease.

The molecular epidemiology of culture-confirmed invasive meningococcal disease (IMD) in Canada from 2010 to 2014 was studied with an emphasis on serogroup B Neisseria meningitidis (MenB) isolates, including their predicted coverage by the 4CMenB vaccine. The mean annual incidence rates of culture confirmed IMD varied from 0.19/100,000 in Ontario to 0.50/100,000 in New Brunswick and 0.59/100,000 in Quebec. In both Quebec and Atlantic region, MenB was significantly more common than other serogroups, while in other provinces, both MenB and serogroup Y (MenY) were almost equally common. The majority of MenB cases (67.0%) were in those aged ≤24 years, while most MenC (75.0%) and MenY (69.6%) cases were in adults more than 24 years old. The 349 MenB isolates were grouped into 103 sequence types (STs), 90 of which belonged to 13 clonal complexes (CCs). A large number of 4CMenB antigen genes were found among the Canadian MenB, which is predicted to encode 50 factor H binding protein (fHbp) types, 40 NHBA types, and 55 PorA genotypes. Provinces and regions were found to have their own unique MenB STs. A meningococcal antigen typing system assay predicted an overall MenB coverage by 4CMenB to be 73.6%, with higher coverage predicted for the two most common STs: 100% for ST154 and 95.9% for ST269, leading to higher coverage in both the Atlantic region and Quebec. Higher coverage (81.4%) was also found for MenB recovered from persons aged 15 to 24 years, followed by strains from infants and children ≤4 years old (75.2%) and those aged 5 to 14 years (75.0%).

IMPORTANCE Laboratory surveillance of invasive meningococcal disease (IMD) is important to our understanding of the evolving nature of the Neisseria meningitidis strain types causing the disease and the potential coverage of disease strains by the newly developed vaccines. This study examined the molecular epidemiology of culture-confirmed IMD cases in Canada by examining the strain types and the potential coverage of a newly licensed 4CMenB vaccine on Canadian serogroup B N. meningitidis strains. The strain types identified in different parts of Canada appeared to be unique as well as their predicted coverage by the 4CMenB vaccine. These data were compared to data obtained from previous studies done in Canada and elsewhere globally. For effective control of IMD, laboratory surveillance of this type was found to be essential and useful to understand the dynamic nature of this disease.

Selection of diverse strains to assess broad coverage of the bivalent FHbp meningococcal B vaccine

MenB-FHbp is a recombinant meningococcal serogroup B (MenB) vaccine composed of 2 factor H binding proteins (FHbps). Meningococcal vaccines targeting polysaccharide serogroup A, C, Y, and W capsules were licensed upon confirmation of bactericidal antibody induction after initial efficacy studies with serogroup A and C vaccines. Unlike meningococcal polysaccharide vaccines, wherein single strains demonstrated bactericidal antibodies per serogroup for each vaccine, MenB-FHbp required a more robust approach to demonstrate that bactericidal antibody induction could kill strains with diverse FHbp sequences. Serum bactericidal assays using human complement were developed for 14 MenB strains, representing breadth of meningococcal FHbp diversity of ~80% of circulating MenB strains. This work represents an innovative approach to license a non-toxin protein vaccine with 2 antigens representing a single virulence factor by an immune correlate, and uniquely demonstrates that such a vaccine provides coverage across bacterial strains by inducing broadly protective antibodies.

Neisseria meningitidis is an important cause of invasive meningococcal disease, effective vaccines exist for some serogroups but immunogenicity to the MenB group is poor. Thomas R. Jones and colleagues examine serum bactericidal responses from volunteers challenged with MenB-FHbp – a recombinant MenB vaccine containing two Factor H (FH)-binding proteins. Serum bactericidal responses are tested against 14 MenB clinical isolates selected in an unbiased manner to cover the vast breadth of FHbp antigen and epidemiological diversity. This work demonstrates the broad efficacy of the MenB-FHbp vaccine using a serum bactericidal activity as a surrogate of protection.

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.

[Economic evaluation of the introduction of 4CMenB (Bexsero®) in the national vaccine schedule in Spain]

INTRODUCTION

Bexsero® (4CMenB), meningococcal B vaccine, was licensed in Europe in 2013. In Spain, despite MenB being the most frequent cause of invasive meningococcal disease (IMD), Bexsero® is recommended and financed for patients at increased risk of IMD but is not financed by the NHS in the routine vaccination schedule.

OBJECTIVE

to evaluate the cost-utility, epidemiological impact, and total costs of the introduction of 4CMenB into the vaccination schedule to help inform vaccine policy in Spain.

METHOD

We adapted a cost-utility analysis, a probabilistic decision-tree, to Spain. A cohort of new-born infants in 2015 was modelled with two dosages, using two different strategies: routine vaccination schedule with 4CMenB and non-vaccination. Costs were measured from a payer perspective and benefits were calculated in quality-adjusted life years (QALYs). A Monte Carlo analysis and 32 scenarios were performed to assess the robustness and the uncertainty of our results.

RESULTS

With the 3+1 dosage, routine vaccination prevented 54% of cases and deaths and an incremental cost-utility ratio (ICUR) of 351.389 €/QALY (95% confidence interval [95%CI]: 265,193-538,428) was estimated. The 2+1 dosage prevented 50% of cases and deaths, with an ICUR of 278.556 €/QALY (95%CI: 210,285-430,122).

CONCLUSIONS

Given the current incidence of invasive meningococcal disease in Spain and the information available from 4CMenB, our model shows that routine vaccination is not cost-effective at the current price. Only with a vaccine price of 1.45 € for the 3+1 schedule or 3.37 € for the 2+1 schedule could it be recommended based on efficiency criteria.

Phenotypic and genotypic characterization of meningococcal isolates in Tunis, Tunisia: High diversity and impact on vaccination strategies

OBJECTIVES

The aim of this study was to characterize Neisseria meningitidis (Men) isolates in Tunisian paediatric patients with invasive meningococcal disease (IMD) in order to target therapeutic and preventive strategies.

METHODS

Fifty-nine isolates of Men and four cerebrospinal fluid samples that were culture-negative but Men-positive by PCR (NC-MenPPCR) (2009-2016) were collected from IMD patients. Isolates were analysed for their antimicrobial susceptibility. Whole-genome sequencing (WGS) was used to characterize isolates and multilocus sequence typing for NC-MenPPCR. Coverage of Men serogroup B (MenB) was determined by Genetic Meningococcal Antigen Typing System (gMATS) and fHbp expression by ELISA.

RESULTS

MenB was the predominant type (88.9%). The majority of isolates (81%) had reduced susceptibility to penicillin G with altered penA alleles. The clonal complex CC461 (27.1%) was the most frequent. Among the MenB vaccine targets neisserial heparin binding antigen (NHBA) and fHbp, the predominant variants were NHBA118 (30.8%) and fHbp peptide 47 (25%), respectively. The nadA gene was present in 17.3% of isolates. Using gMATS, 36.5% of MenB were predicted to be covered by the 4CMenB vaccine. ELISA showed that 92.4% of the MenB were expected to be killed by anti-fHbp antibodies.

CONCLUSIONS

MenB was the leading serogroup in IMD, and more than 90% had a sufficient level of fHbp expression for vaccine coverage. The study results will be useful for the Tunisian vaccination programme.

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.

Epidemiology of community-acquired bacterial meningitis

PURPOSE OF REVIEW

The epidemiology of bacterial meningitis has been dynamic in the past 30 years following introduction of conjugated vaccines against Haemophilus influenzae type B, Streptococcus pneumoniae and Neisseria meningitidis. The purpose of this review is to describe recent developments in bacterial meningitis epidemiology.

RECENT FINDINGS

The incidence of bacterial meningitis in Western countries (Finland, Netherlands, and the United States) gradually declined by 3-4% per year to 0.7-0.9 per 100 000 per year in the past 10-20 years. In African countries (Burkina Faso and Malawi), incidence rates are still substantially higher at 10-40 per 100 000 persons per year. Introduction of pneumococcal conjugate vaccines have not consistently decreased overall pneumococcal meningitis incidence because of serotype replacement. Following the introduction of serogroup A and C meningococcal vaccines, the incidence of meningococcal meningitis because of these serogroups strongly decreased. Novel outbreaks in the African meningitis belt by serogroup C and increased incidence of serogroup W in the United Kingdom and the Netherlands were observed recently.

SUMMARY

Bacterial meningitis remains an important infectious disease, despite a gradual decline in incidence after large-scale vaccination campaigns. Further development of vaccines with broader coverage is important, as is continuous surveillance of bacterial meningitis cases.

Potential benefits of using a multicomponent vaccine for prevention of serogroup B meningococcal disease

Meningococcal serogroup B (MenB) has become the main cause of invasive meningococcal disease in industrialized countries in recent years. The diversity of MenB strains and poor immunogenicity of the MenB capsular polysaccharide have made vaccine development challenging. Two MenB vaccines, including factor H binding protein (fHbp) as a major antigenic component, are now licensed for use. In addition to fHbp variant 1, the multicomponent vaccine 4CMenB contains neisserial heparin binding antigen, Neisseria adhesin A, and outer membrane vesicles containing porin A. The vast majority of circulating MenB strains contain genes encoding at least one 4CMenB component and many express genes for more than one vaccine antigen. Recent studies have suggested that serum bactericidal activity is enhanced against strains that express two or more vaccine antigens. Bacterial killing may also occur when antibodies to vaccine components are collectively present at levels that would individually be sub-lethal. The evaluation of immune responses to separate vaccine components does not take cooperative activity into account and may underestimate the overall protection. Available data on 4CMenB effectiveness indicate that this multicomponent vaccine affords broad coverage and protection against MenB disease. 4CMenB also has the potential to protect against disease caused by non-MenB meningococci and Neisseria gonorrhoeae.

The Development of a Vaccine Against Meningococcus B Using Reverse Vaccinology

The discovery of vaccine antigens through whole genome sequencing (WGS) contrasts with the classical hypothesis-driven laboratory-based analysis of microbes to identify components to elicit protective immunity. This radical change in scientific direction and action in vaccine research is captured in the term reverse vaccinology. The complete genome sequence of an isolate of Neisseria meningitidis serogroup B (MenB) was systematically analyzed to identify proteins predicted to be secreted or exported to the outer membrane. This identified hundreds of genes coding for potential surface-exposed antigens. These were amplified, cloned in expression vectors and used to immunize mice. Antisera against 350 recombinant antigens were obtained and analyzed in a panel of immunological assays from which 28 were selected as potentially protective based on the -antibody dependent, complement mediated- serum bactericidal activity assay. Testing of these candidate vaccine antigens, using a large globally representative strain collection of Neisseria species isolated from cases of disease and carriage, indicated that no single component would be sufficient to induce broad coverage and that a “universal” vaccine should contain multiple antigens. The final choice of antigens to be included was based on cross-protective ability, assayed by serum bactericidal activity and maximum coverage of the extensive antigenic variability of MenB strains. The resulting multivalent vaccine formulation selected consisted of three recombinant antigens (Neisserial Heparin Binding Antigen or NHBA, Factor H binding protein or fHbp and Neisseria Adhesin A or NadA). To improve immunogenicity and potential strain coverage, an outer membrane vesicle component obtained from the epidemic New Zealand strain (OMVNz) was added to the formulation to create a four component vaccine, called 4CMenB. A series of phase 2 and 3 clinical trials were conducted to evaluate safety and tolerability and to estimate the vaccine effectiveness of human immune responses at different ages and how these were affected by various factors including concomitant vaccine use and lot-to-lot consistency. 4CMenB was approved in Europe in 2013 and introduced in the National Immunization Program in the UK starting from September 2015 when the vaccine was offered to all newborns using a 2, 4, and 12 months schedule., The effectiveness against invasive MenB disease measured at 11 months after the study start and 5 months after the second vaccination was 83% and there have been no safety concerns.

Genomic Surveillance of 4CMenB Vaccine Antigenic Variants among Disease-Causing Neisseria meningitidis Isolates, United Kingdom, 2010-2016

In September 2015, 4CMenB meningococcal vaccine was introduced into the United Kingdom infant immunization program without phase 3 trial information. Understanding the effect of this program requires enhanced surveillance of invasive meningococcal disease (IMD) Neisseria meningitidis isolates and comparison with prevaccination isolates. Bexsero Antigen Sequence Types (BASTs) were used to analyze whole-genome sequences of 3,073 prevaccine IMD N. meningitidis isolates obtained during 2010−2016. Isolates exhibited 803 BASTs among 31 clonal complexes. Frequencies of antigen peptide variants were factor H binding protein 1, 13.4%; Neisserial heparin-binding antigen 2, 13.8%; Neisseria adhesin A 8, 0.8%; and Porin A-VR2:P1.4,10.9%. In 2015−16, serogroup B isolates showed the highest proportion (35.7%) of exact matches to >1 Bexsero components. Serogroup W isolates showed the highest proportion (93.9%) of putatively cross-reactive variants of Bexsero antigens. Results highlighted the likely role of cross-reactive antigens. BAST surveillance of meningococcal whole-genome sequence data is rapid, scalable, and portable and enables international comparisons of isolates.

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.

Meningococcal disease in adolescents and young adults: a review of the rationale for prevention through vaccination

Invasive meningococcal disease (IMD) caused by Neisseria meningitidis is characterized by high mortality and morbidity. While IMD incidence peaks in both infants and adolescents/young adults, carriage rates are often highest in the latter age groups, increasing IMD risk and the likelihood of transmission. Effective vaccines are available for 5 of 6 disease-causing serogroups. Because adolescents/young adults represent a significant proportion of cases, often have the highest carriage rate, and have characteristically low vaccination adherence, efforts should be focused on educating this population regarding long-term consequences of infection and the importance of meningococcal vaccination in prevention. This review describes the role of adolescents/young adults in meningococcal transmission and the clinical consequences and characteristics of IMD in this population. With a focus on countries with advanced economies that have specific meningococcal vaccination recommendations, the epidemiology of meningococcal disease and vaccination recommendations in adolescents/young adults will also be discussed.

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

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.

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 [CI_95%], 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.

Bioinformatic analysis of meningococcal Msf and Opc to inform vaccine antigen design

Neisseria meningitidis is an antigenically and genetically variable Gram-negative bacterium and a causative agent of meningococcal meningitis and septicaemia. Meningococci encode many outer membrane proteins, including Opa, Opc, Msf, fHbp and NadA, identified as being involved in colonisation of the host and evasion of the immune response. Although vaccines are available for the prevention of some types of meningococcal disease, none currently offer universal protection. We have used sequences within the Neisseria PubMLST database to determine the variability of msf and opc in 6,500 isolates. In-silico analysis revealed that although opc is highly conserved, it is not present in all isolates, with most isolates in clonal complex ST-11 lacking a functional opc. In comparison, msf is found in all meningococcal isolates, and displays diversity in the N-terminal domain. We identified 20 distinct Msf sequence variants (Msf SV), associated with differences in number of residues within the putative Vn binding motifs. Moreover, we showed distinct correlations with certain Msf SVs and isolates associated with either hyperinvasive lineages or those clonal complexes associated with a carriage state. We have demonstrated differences in Vn binding between three Msf SVs and generated a cross reactive Msf polyclonal antibody. Our study has highlighted the importance of using large datasets to inform vaccine development and provide further information on the antigenic diversity exhibited by N. meningitidis.

Increase of Neisseria meningitidis W:cc11 invasive disease in Chile has no correlation with carriage in adolescents

Neisseria meningitidis is a human exclusive pathogen that can lead to invasive meningococcal disease or may be carried in the upper respiratory tract without symptoms. The relationship between carriage and disease remains poorly understood but it is widely accepted that decreasing carriage by immunization should lead to a reduction of invasive cases. Latin America has experienced an increased incidence of serogroup W invasive cases of Neisseria meningitidis in the last decade. Specifically in Chile, despite low total incidence of invasive cases, serogroup W has become predominant since 2011 and has been associated with elevated mortality. Expecting to gain insight into the epidemiology of this disease, this study has used molecular typing schemes to compare Neisseria meningitidis isolates causing invasive disease with those isolates collected from adolescent carriers during the same period in Chile. A lower carriage of the serogroup W clonal complex ST-11/ET37 than expected was found; whereas, the same clonal complex accounted for 66% of total invasive meningococcal disease cases in the country that year. A high diversity of PorA variable regions and fHbp peptides was also ascertained in the carrier isolates compared to the invasive ones. According to the results shown here, the elevated number of serogroup W invasive cases in our country cannot be explained by a rise of carriage of pathogenic isolates. Overall, this study supports the idea that some strains, as W:cc11 found in Chile, possess an enhanced virulence to invade the host. Notwithstanding hypervirulence, this strain has not caused an epidemic in Chile. Finally, as genetic transfer occurs often, close surveillance of Neisseria meningitidis strains causing disease, and particularly hypervirulent W:cc11, should be kept as a priority in our country, in order to prepare the best response to face genetic changes that could lead to enhanced fitness of this pathogen.

Differences in the population structure of Neisseria meningitidis in two Australian states: Victoria and Western Australia

Neisseria meningitidis is the causative agent of invasive meningococcal disease (IMD). A recombinant vaccine called Bexsero® incorporates four subcapsular antigens (fHbp, NHBA, NadA and PorA) which are used to assign a Bexsero® antigen sequence type (BAST) to each meningococcal strain. The vaccine elicits an immune response against combinations of variants of these antigens which have been grouped into specific BAST profiles that have been shown to have different distributions within geographical locations thus potentially affecting the efficacy of the vaccine. In this study, invasive meningococcal disease isolates from the western seaboard of Australia (Western Australia; WA) were compared to those from the south-eastern seaboard (Victoria; VIC) from 2008 to 2012. Whole-genome sequencing (WGS) of 131 meningococci from VIC and 70 meningococci from WA were analysed for MLST, FetA and BAST profiling. Serogroup B predominated in both jurisdictions and a total of 10 MLST clonal complexes (cc) were shared by both states. Isolates belonging to cc22, cc103 and cc1157 were unique to VIC whilst isolates from cc60 and cc212 were unique to WA. Clonal complex 41/44 represented one-third of the meningococcal population in each state but the predominant ST was locally different: ST-6058 in VIC and ST-146 in WA. Of the 108 BAST profiles identified in this collection, only 9 BASTs were simultaneously observed in both states. A significantly larger proportion of isolates in VIC harboured alleles for the NHBA-2 peptide and fHbp-1, antigenic variants predicted to be covered by the Bexsero® vaccine. The estimate for vaccine coverage in WA (47.1% [95% CI: 41.1-53.1%]) was significantly lower than that in VIC (66.4% [95% CI: 62.3-70.5%]). In conclusion, the antigenic structure of meningococci causing invasive disease in two geographically distinct states of Australia differed significantly during the study period which may affect vaccine effectiveness and highlights the need for representative surveillance when predicting potential impact of meningococcal B vaccines.

Potential impact of the 4CMenB vaccine on oropharyngeal carriage of Neisseria meningitidis

The analysis of the potential impact of the meningococcal vaccines in asymptomatic carriers has become one of the key aspects in the evaluation of new vaccines and of their impact on disease control. An important step in this direction is provided by the analysis of the sequence variability and surface-exposure of the 4CMenB (Bexsero®) vaccine antigens, as well as the cross-reactivity of vaccine induced antibodies, in isolates from healthy carriers. The Spanish Reference Laboratory, in collaboration with the University Hospital Marqués de Valdecilla in Santander (Spain), carried out a meningococcal carrier survey between May 2010 and April 2012 (population aged 4 to 19 years). The present study was done on 60 meningococcal carrier strains representative of the overall strain panel obtained and compared to invasive strains isolated in Spain in the same time. We found quantifiable levels of fHbp and NHBA expression and immunologic cross-reactivity in 10% and 75% of analyzed carrier strains, respectively, so the potential impact of the 4CMenB vaccine on Spanish asymptomatic carrier strains is expected to be mediated by the NHBA antigen.

Predicted strain coverage of a meningococcal multicomponent vaccine (4CMenB) in Portugal

Objective

Although the incidence of meningococcal disease has been declining over the past decade in Portugal MenB meningococci is still an important cause of meningitis and sepsis. The aim of this study was to estimate the strain coverage of the 4CMenB vaccine in Portugal in order to support health policies for prevention and control of meningococcal disease.

Methods

Since 2002 the clinical and laboratory notification of meningococcal disease is mandatory in Portugal. National database includes since then all confirmed cases notified to the reference laboratory or to the Directorate of Health. Strains included in this study were all the invasive MenB isolated from the 1^st July 2011 to the 30^th June 2015, sent to the reference laboratory. To predict the vaccine strain coverage of the 4CMenB the expression and cross-reactivity of the surface antigens fHbp, NadA, NHBA were assessed by the Meningococcal Antigen Typing System (MATS) whereas PorA typing was performed by sequencing. The presence of at least one antigen with a Relative Potency (RP) greater than its MATS-positive bactericidal threshold RP value or the presence of PorA VR2 = 4 was considered to be predictive for a strain to be covered by the 4CMenB vaccine.

Results

The estimated 4CMenB strain coverage in Portugal was 67.9%. The percentage of strain coverage in each of the four epidemiological years ranged from 63.9% to 73.7%.

Strains covered by one antigen represent 32.1% of the total of isolates, 29.2% of strains were covered by two antigens and 6.6% by three antigens. No strain had all the four antigens. Antigens that most contributed for coverage were NHBA and fHbp.

Data from Portugal is in accordance with the MATS predicted strain coverage in five European countries (England and Wales, France, Germany, Italy and Norway) that pointed to 78% coverage for strains collected in the epidemiological year 2007–2008.

Emerging experience with meningococcal serogroup B protein vaccines

INTRODUCTION

The successful development of two broadly protective vaccines targeting Neisseria meningitidis serogroup B (MenB); 4CMenB and rLP2086, is the most significant recent advance in meningococcal disease prevention. Areas covered: Here we review the principles underlying the development of each vaccine and the novel methods used to estimate vaccine coverage. We update clinical and post-licensure experience with 4CMenB and rLP2086. Expert commentary: The immunogenicity and acceptable safety profile of 4CMenB and rLP2086 has been demonstrated in clinical trials. Continuing uncertainties exist around the appropriate age groups to be immunized, the degree and duration of efficacy, and the impact on nasopharyngeal carriage which has implications for strategies to interrupt transmission and maximize herd protection effects. Universal vaccination programs such as those undertaken in Quebec and the United Kingdom are providing important information on these issues. The potential for MenB vaccines to prevent infection by other serogroups appears promising, and the impact of MenB vaccines on other pathogenic neisserial species with similar surface proteins warrants further investigation.

Meningococcal serogroup B strain coverage of the multicomponent 4CMenB vaccine with corresponding regional distribution and clinical characteristics in England, Wales, and Northern Ireland, 2007-08 and 2014-15: a qualitative and quantitative assessment

BACKGROUND

The UK introduced 4CMenB-a multicomponent vaccine against serogroup B meningococcal disease-into the national infant immunisation programme in September, 2015. The Meningococcal Antigen Typing System (MATS) was used to estimate coverage by 4CMenB of invasive meningococcal group B isolates obtained during 2007-08 in England and Wales (MATS coverage). We aimed to repeat the MATS survey for invasive meningococcal group B isolates obtained during 2014-15, before 4CMenB introduction; compare strain coverage between 2007-08 and 2014-15; and investigate associations between MATS coverage, age, region, and disease outcomes.

METHODS

Invasive serogroup B meningococcal isolates from cases in England, Wales, and Northern Ireland during 2014-15 were assayed using MATS and compared with 2007-08 data. MATS coverage was assessed by geographical region and age group. Clinical characteristics, risk factors, and outcomes were assessed according to MATS coverage for 2014-15 English cases.

FINDINGS

In 2014-15, 165 of 251 (66%; 95% CI 52-80) meningococcal group B isolates were estimated by MATS to be covered by 4CMenB, compared with 391 of 535 (73%; 95% CI 57-87) in 2007-08. The proportion of MATS-positive isolates with one vaccine antigen increased from 23% (122 of 535) in 2007-08 to 31% (78 of 251) in 2014-15, whereas the proportion with more than one antigen fell from 50% (269 of 535) to 35% (87 of 251). This effect reflected changes in circulating strains, particularly ST-269 clonal complex strains. MATS coverage increased with age, varied by geographical region, and was associated with more severe disease.

INTERPRETATION

In 2014-15, two-thirds of meningococcal group B isolates were predicted to be covered by 4CMenB. Temporal changes in MATS coverage underscore the need for continued monitoring of antigen expression and diversity, particularly in countries with 4CMenB programmes.

FUNDING

Public Health England, GlaxoSmithKline.

Epitope Mapping of a Monoclonal Antibody Directed against Neisserial Heparin Binding Antigen Using Next Generation Sequencing of Antigen-Specific Libraries

We explore here the potential of a newly described technology, which is named PROFILER and is based on next generation sequencing of gene-specific lambda phage-displayed libraries, to rapidly and accurately map monoclonal antibody (mAb) epitopes. For this purpose, we used a novel mAb (designated 31E10/E7) directed against Neisserial Heparin-Binding Antigen (NHBA), a component of the anti-group B meningococcus Bexsero® vaccine. An NHBA phage-displayed library was affinity-selected with mAb 31E10/E7, followed by massive sequencing of the inserts present in antibody-selected phage pools. Insert analysis identified an amino acid stretch (D91-A128) in the N-terminal domain, which was shared by all of the mAb-enriched fragments. Moreover, a recombinant fragment encompassing this sequence could recapitulate the immunoreactivity of the entire NHBA molecule against mAb 31E10/E7. These results were confirmed using a panel of overlapping recombinant fragments derived from the NHBA vaccine variant and a set of chemically synthetized peptides covering the 10 most frequent antigenic variants. Furthermore, hydrogen-deuterium exchange mass-spectrometry analysis of the NHBA-mAb 31E10/E7 complex was also compatible with mapping of the epitope to the D91-A128 region. Collectively, these results indicate that the PROFILER technology can reliably identify epitope-containing antigenic fragments and requires considerably less work, time and reagents than other epitope mapping methods.