Pooled-sera hSBA titres predict individual seroprotection in infants and toddlers vaccinated with 4CMenB

Recombinant ClearColi™-derived outer membrane vesicles as an effective carrier for development of neoepitope-based vaccine candidate against colon carcinoma

BACKGROUND

Colorectal carcinoma (CRC) is the third most common cancer worldwide, with high clonal heterogeneity due to somatic mutations. Poly neoepitope vaccines can inhibit the tumor's escape from the immune system. However, they have rapid clearance and low immunogenicity. Bacteria-derived recombinant outer membrane vesicles (OMVs) have gained increased attention as ideal cancer vaccine candidates due to their unique adjuvant properties and ability to carry antigens. Herein, the benefits of OMV-based and polyneoepitope-based vaccines were combined to obtain a functional individualized cancer vaccine.

METHODS

OMVs and rOMVs displaying CT26 polytopes were isolated from ClearColi™ and recombinant ClearColi™ containing pET-22b (ClyA-CT26 polytope) by the AS (70 %) + UDF method. BALB/c mice were immunized with OMVs (40 µg) and rOMVs (20 and 40 µg) and subcutaneously challenged with CT26 cells. Then, IgG1 and IgG2a antibodies specific for CT26 M90 and CT26 polytope, the stimulated IFN-γ, TNF-α, and IL-10 cytokines and the stimulated CTL responses by measuring granzyme B were evaluated. To investigate whether pooled sera and pooled splenocytes are indicators of individual responses, pooled and individual methods for determining the elicited immunity were compared. Additionally, the ability of OMVs and rOMVs (20 and 40 µg) to prevent tumor growth against the CT26 challenge was investigated.

RESULTS

Immunization with rOMVs displaying CT26 polytopes induced a higher titer of CT26 polytope- and CT26 M90 peptide-specific IgG2a than IgG1 antibodies in a dose-dependent manner, thus directing immunity to Th1. The antibody responses determined by pooled sera can be used as indicators of individual responses. In addition, both OMVs and rOMVs displaying CT26 polytopes could induce tumor-suppressing cytokines (IFN-γ and TNF-α). The ability of rOMVs displaying CT26 polytopes to induce these cytokines was higher than OMVs in a dose-dependent way. The results of the granzyme B assay were also in agreement with the cytokine assay. The survival of mice after the CT26 challenge was 100 % in the OMVs and rOMVs groups, and inhibition of tumor growth was significantly higher by rOMVs (40 µg) compared to OMVs.

CONCLUSION

The bioengineered OMVs displaying CT26 neoepitopes have the potential for the development of personalized tumor vaccines. Our results can provide new insights for developing rOMV-based vaccines displaying polytopes against diseases containing highly variable antigens.

Product review on the IMD serogroup B vaccine Bexsero®

Bexsero® is a multicomponent vaccine composed of four major proteins of Neisseria meningitidis: the fHbp, NHBA, NadA and PorA. This vaccine was licensed against invasive meningococcal disease (IMD) due to serogroup B isolates. When administered alone, Bexsero® showed a safety profile similar to other childhood vaccines. It provides an excellent immunogenicity but that requires booster doses in infants and young children. Although the vaccine does not seem to impact on acquisition of carriage of serogroup B isolates, it confers protection against isolates of serogroup B harboring distinct but cross-reactive variants of fHbp, NadA and NHBA. Primary vaccination schemes in infancy underwent a rapid increase after a toddler booster suggesting an anamnestic response and the establishment of a memory response. As Bexsero® targets sub-capsular proteins that can be conserved regardless the capsule, the vaccine can be effective against non-B isolates such as isolates of serogroups W and X.

Invasive serogroup B meningococci in England following three years of 4CMenB vaccination - First real-world data

OBJECTIVES

In 2015 the UK became the first country to implement the meningococcal B (MenB) vaccine, 4CMenB, into the national infant program. 4CMenB is expected to cover meningococci expressing sufficient levels of cross-reactive proteins. This study presents clonal complex, 4CMenB antigen genotyping, and 4CMenB coverage data for all English invasive MenB isolates from 2014/15 (1 year pre-vaccine) through 2017/18 and compares data from vaccinated and unvaccinated ≤3 year olds.

METHODS

Vaccine coverage of all invasive MenB isolates from 2014/15 to 2017/18 (n = 784) was analysed using the Meningococcal Antigen Typing System. Genotyping utilised the Meningococcus Genome Library.

RESULTS

Among ≤3 year olds, proportionally fewer cases in vaccinees (1, 2 or 3 doses) were associated with well-covered strains e.g. cc41/44 (20.5% versus 36.4%; P<0.01) and antigens e.g. PorA P1.4 (7.2% versus 17.3%; P = 0.02) or fHbp variant 1 peptides (44.6% vs 69.1%; P<0.01). Conversely, proportionally more cases in vaccinees were associated with poorly-covered strains e.g. cc213 (22.9% versus 9.6%; P<0.01) and antigens e.g. variant 2 or 3 fHbp peptides (54.2% versus 30.9%; P<0.01).

CONCLUSIONS

4CMenB reduces disease due to strains with cross-reactive antigen variants. No increase in absolute numbers of cases due to poorly covered strains was observed in the study period.

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.

Cross-reactivity of 4CMenB vaccine-induced antibodies against meningococci belonging to non-B serogroups in Italy

The four-component meningococcal serogroup B vaccine (4CMenB) contains antigens present in the majority of meningococci causing invasive meningococcal disease (IMD) and may potentially offer protection against strains belonging to non-B serogroups.This study aimed to evaluate the ability of 4CMenB-induced antibodies to kill, in a human serum bactericidal assay (hSBA), non-B meningococci belonging to the main genotypes responsible for IMD in Italy.Meningococci, collected between 2015 and 2017, was characterized for PorA, FetA and sequence type, and for clonal complex. Twenty non-B isolates, representative of the most frequent genotypes, were molecularly characterized for 4CMenB antigens and tested in hSBA with sera from 4CMenB-vaccinated infants and adolescents.Among twenty isolates, eleven were serogroup C, five were Y, two W and two X. All isolates contained genes encoding for fHbp and NHBA antigens and four harbored the NadA full-length encoding gene. Positive hSBA titers were obtained against all serogroup W, X and Y isolates and against five serogroup C isolates.These data show that the 4CMenB vaccine can induce bactericidal antibodies against genetically representative meningococcal W, Y and X strains from Italy. For serogroup C, different susceptibilities to killing were observed for strains with similar antigenic repertoires.

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.

4CMenB Immunization Induces Serum Bactericidal Antibodies Against Non-Serogroup B Meningococcal Strains in Adolescents

Introduction

Invasive meningococcal disease (IMD) is an important public health concern. In developed countries, most IMD is caused by meningococcal serogroup B (MenB) and two protein-based MenB vaccines are currently available: the four-component vaccine 4CMenB (Bexsero, GSK) and the bivalent vaccine MenB-FHbp (Trumenba, Pfizer). Genes encoding the 4CMenB vaccine antigens are also present in strains belonging to other meningococcal serogroups.

Methods

To evaluate the potential of 4CMenB vaccination to protect adolescents against non-MenB IMD, we tested the bactericidal activity of sera from immunized adolescents on 147 (127 European and 20 Brazilian) non-MenB IMD isolates, with a serum bactericidal antibody assay using human complement (hSBA). Serum pools were prepared using samples from randomly selected participants in various clinical trials, pre- and post-vaccination: 12 adolescents who received two doses of 4CMenB 2 months apart, and 10 adolescents who received a single dose of a MenACWY conjugate vaccine (as positive control).

Results

4CMenB pre-immune sera killed 7.5% of the 147 non-MenB isolates at hSBA titers ≥ 1:4. In total, 91 (61.9%) tested isolates were killed by post-dose 2 pooled sera at hSBA titers ≥ 1:4, corresponding to 44/80 (55.0%) MenC, 26/35 (74.3%) MenW, and 21/32 (65.6%) MenY isolates killed.

Conclusion

4CMenB vaccination in adolescents induces bactericidal killing of non-MenB isolates, suggesting that mass vaccination could impact IMD due to serogroups other than MenB.

Multicomponent meningococcal serogroup B vaccination elicits cross-reactive immunity in infants against genetically diverse serogroup C, W and Y invasive disease isolates

BACKGROUND

The multicomponent meningococcal serogroup B vaccine (4CMenB) is currently indicated for active immunization against invasive meningococcal disease caused by Neisseria meningitidis serogroup B (MenB). However, genes encoding the 4CMenB antigens are also variably present and expressed in strains belonging to other meningococcal serogroups. In this study, we evaluated the ability of antibodies raised by 4CMenB immunisation to induce complement-mediated bactericidal killing of non-MenB strains.

METHODS

A total of 227 invasive non-MenB disease isolates were collected between 1 July 2007 and 30 June 2008 from England and Wales, France, and Germany; 41 isolates were collected during 2012 from Brazil. The isolates were subjected to genotypic analyses. A subset of 147 isolates (MenC, MenW and MenY) representative of the meningococcal genetic diversity of the total sample were tested in the human complement serum bactericidal antibody assay (hSBA) using sera from infants immunised with 4CMenB.

RESULTS

Serogroup and clonal complex repertoires of non-MenB isolates were different for each country. For the European panel, MenC, MenW and MenY isolates belonged mainly to ST-11, ST-22 and ST-23 complexes, respectively. For the Brazilian panel, most MenC and MenW isolates belonged to the ST-103 and ST-11 complexes, respectively, and most MenY isolates were not assigned to clonal complexes. Of the 147 non-MenB isolates, 109 were killed in hSBA, resulting in an overall coverage of 74%.

CONCLUSION

This is the first study in which 147 non-MenB serogroup isolates have been analysed in hSBA to evaluate the potential of a MenB vaccine to cover strains belonging to other serogroups. These data demonstrate that antibodies raised by 4CMenB are able to induce bactericidal killing of 109 non-MenB isolates, representative of non-MenB genetic and geographic diversity. These findings support previous evidence that 4CMenB immunisation can provide cross-protection against non-MenB strains in infants, which represents an added benefit of 4CMenB vaccination.

Toward a Global Genomic Epidemiology of Meningococcal Disease

Whole-genome sequencing (WGS) is invaluable for studying the epidemiology of meningococcal disease. Here we provide a perspective on the use of WGS for meningococcal molecular surveillance and outbreak investigation, where it helps to characterize pathogens, predict pathogen traits, identify emerging pathogens, and investigate pathogen transmission during outbreaks. Standardization of WGS workflows has facilitated their implementation by clinical and public health laboratories (PHLs), but further development is required for metagenomic shotgun sequencing and targeted sequencing to be widely available for culture-free characterization of bacterial meningitis pathogens. Internet-accessible servers are being established to support bioinformatics analysis, data management, and data sharing among PHLs. However, establishing WGS capacity requires investments in laboratory infrastructure and technical knowledge, which is particularly challenging in resource-limited regions, including the African meningitis belt. Strategic WGS implementation is necessary to monitor the molecular epidemiology of meningococcal disease in these regions and construct a global view of meningococcal disease epidemiology.

Does vaccination with 4CMenB convey protection against meningococcal serogroup B strains not predicted to be covered by MATS? A study of the UK clonal complex cc269

The Meningococcal Antigen Typing System (MATS) has been developed as an hSBA surrogate to evaluate potential coverage afforded by the 4-component meningococcal serogroup B vaccine (4CMenB: Bexsero, GSK). We investigated whether the lower value of MATS coverage among invasive Meningococcus serogroup B clonal complex 269 strains from the United Kingdom (53% in 2014–2015 versus 73% in 2007–2008) reflected the lower bactericidal activity of the vaccine against these isolates. A total of 34 MATS-negative strains (31 were cc269 or closely related) were tested against pooled sera from 32 or 72 4CMenB-vaccinated infants in a serum bactericidal antibody assay in presence of human complement (hSBA). All infants had received four 4CMenB doses in the first 2 y of life. Baseline sera comprised 180 pooled samples from healthy-unvaccinated 2-month-old infants. Twenty of the 34 (59%) MATS-negative strains were killed in hSBA with titers ≥4 by pooled sera from vaccinated infants. There were 13/34 strains with hSBA titers ≥4 and at least a 4-fold rise in titer with respect to pooled baseline sera, and 10/34 with hSBA titers ≥8 and at least a 4-fold rise in titer with respect to baseline. These data confirm MATS as a conservative estimate for predicting strain coverage by 4CMenB.

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.

Evaluation of strain coverage of the multicomponent meningococcal serogroup B vaccine (4CMenB) administered in infants according to different immunisation schedules

The 4-component vaccine 4CMenB, developed against invasive disease caused by meningococcal serogroup B, is approved for use in infants in several countries worldwide. 4CMenB is mostly used as 3 + 1 schedule, except for the UK, where a 2 + 1 schedule is used, and where the vaccine showed an effectiveness of 82.9%. Here we compared the coverage of two 4CMenB vaccination schedules (3 + 1 [2.5, 3.5, 5, 11 months] versus 2 + 1 [3.5, 5, 11 months of age]) against 40 serogroup B strains, representative of epidemiologically-relevant isolates circulating in England and Wales in 2007–2008, using sera from a previous phase 3b clinical trial. The strains were tested using hSBA on pooled sera of infants, collected at one month post-primary and booster vaccination. 4CMenB coverage was defined as the percentage of strains with positive killing (hSBA titres ≥ 4 after immunisation and negative baseline hSBA titres < 2). Coverage of 4CMenB was 40.0% (95% confidence interval [CI]: 24.9–56.7) and 87.5% (95%CI: 73.2–95.8) at one month post-primary and booster vaccination, respectively, regardless of immunisation schedule. Using a more conservative threshold (post-immunisation hSBA titres ≥ 8; baseline ≤ 2), at one month post-booster dose, strain coverages were 80% (3 + 1) and 70% (2 + 1). We used a linear regression model to assess correlation between post-immunisation hSBA data for each strain in the two groups; Pearson’s correlation coefficients were 0.93 and 0.99 at one month post-primary and booster vaccination. Overall, there is no evidence for a difference in strain coverage when 4CMenB is administered according to a 3 + 1 or 2 + 1 infant vaccination schedule.

Immunogenicity and safety of the multicomponent meningococcal B vaccine (4CMenB) in children and adolescents: a systematic review and meta-analysis

BACKGROUND

The multicomponent meningococcal serogroup B vaccine (4CMenB) has been licensed in more than 35 countries. However, uncertainties remain about the lowest number of doses required to induce satisfactory, persistent immune responses. We did a systematic review and meta-analysis to provide quantitative estimates for the immunogenicity, persistence of immunogenicity, and safety of 4CMenB vaccine in children and adolescents.

METHODS

For this systematic review and meta-analyses (proportion, head to head, and network), we searched MEDLINE, Scopus, Embase, and ClinicalTrials.gov from database inception to June 30, 2017, for randomised trials that compared the immunogenicity or safety of the 4CMenB vaccine with its originator meningococcal B recombinant vaccine or routine vaccines in children or adolescents. For proportion meta-analyses, we also included single arm trials and follow-up studies of randomised controlled trials. Trials that assessed immunogenicity against at least one of four Neisseria meningitidis serogroup B reference strains (44-76/SL, 5/99, NZ98/254, and M10713) and included participants younger than 18 years who had received two or more doses of the 4CMenB vaccine were eligible for inclusion. We requested individual patient-level data from study authors and extracted data from published reports and online trial registries. We did meta-analyses to assess 4CMenB safety and immunogenicity against the four reference strains 30 days after a primary immunisation course (three doses for children, two doses for adolescents), 30 days after the primary course plus one booster dose (children only), 6 months or more after primary course, and 6 months or more after the booster dose.

FINDINGS

736 non-duplicate records were screened, and ten randomised trials and eight follow-on extension trials on 4CMenB met the inclusion criteria. In intention-to-treat analyses, the overall proportion of children and adolescents who achieved seroconversion 30 days after the primary course of 4CMenB was 92% (95% CI 89-95 [I²=95%, p<0·0001]) for the 44/76-SL strain, 91% (87-95 [I²=95%, p<0·0001]) for the 5/99 strain, 84% (77-90 [I²=97%, p<0·0001]) for the NZ98-254 strain, and 87% (68-99 [I²=97%, p<0·0001]) for the M10713 strain. 6 months after the primary course, the immunogenicity remained adequate to high against all three tested strains (5/99, 44/76-SL, and NZ98/254) in adolescents (≥77%), and against two of four strains (5/99 and 44/76-SL) in children (≥67%): the proportion of patients who achieved seroconversion substantially declined for M10713 (<50%) and NZ98/254 (<35%). A booster dose re-enhanced the proportion of patients who achieved seroconversion (≥93% for all strains). However, immunogenicity remained high 6 months after the booster dose for strains 5/99 (95%) and M10713 (75%) only, whereas the proportion of patients who achieved seroconversion against strains 44/76-SL and NZ98/254 returned to similar proportions recorded 6 months after the primary course (62% for 44/76-SL, 35% for NZ98/254). The incidence of potentially vaccine-related, acute serious adverse events in individuals receiving 4CMenB was low (5·4 per 1000 individuals), but was significantly higher than routine vaccines (1·2 per 1000 individuals).

INTERPRETATION

4CMenB has an acceptable short-term safety profile. The primary course is sufficient to achieve a satisfactory immune response within 30 days of vaccination. A booster dose is required for children to prolong the protection against strain M10713, and the long-term immunogenicity against strain NZ98/254 remains suboptimal.

FUNDING

None.

Adverse Events Following Vaccination With Bivalent rLP2086 (Trumenba®): An Observational, Longitudinal Study During a College Outbreak and a Systematic Review

BACKGROUND

In February 2015, two unlinked culture-confirmed cases of Neisseria meningitidis serogroup B (MenB) disease occurred at a local college in Rhode Island ("college X") within 3 days. This represented a 489-fold increase in the incidence of MenB disease, and an outbreak was declared. For the first time, bivalent rLP2086 (Trumenba) was selected as a mandatory intervention response. A mass vaccination clinic was coordinated, which provided a unique opportunity to collect safety data in a real-world population of college-age participants. Though the Advisory Committee on Immunization Practices recommends MenB vaccination for college-age individuals (16-23 year olds), there is limited quantifiable safety data available for this population.

METHODS

The Dillman total design survey method was used. Adverse events of bivalent rLP2086 were solicited and quantified retrospectively 2-4 months following each dose of vaccine. Safety data from six clinical trials were used as comparison tools.

RESULTS

The most commonly reported adverse event following vaccination was injection site pain. Reported rates of injection site pain, fatigue, myalgia, fever, and chills were similar than those reported in clinical trials. Reported rates of headache were lower than in clinical trials.

CONCLUSIONS

This study is the first to examine adverse events of bivalent rLP2086 in a real-world setting where more than 90% of a college-age population was vaccinated.

Meningococcal Antigen Typing System (MATS)-Based Neisseria meningitidis Serogroup B Coverage Prediction for the MenB-4C Vaccine in the United States

Neisseria meningitidis is the most common cause of bacterial meningitis in children and young adults worldwide. A 4-component vaccine against N. meningitidis serogroup B (MenB) disease (MenB-4C [Bexsero]; GSK) combining factor H binding protein (fHBP), neisserial heparin binding protein (NHBA), neisserial adhesin A (NadA), and PorA-containing outer membrane vesicles was recently approved for use in the United States and other countries worldwide. Because the public health impact of MenB-4C in the United States is unclear, we used the meningococcal antigen typing system (MATS) to assess the strain coverage in a panel of strains representative of serogroup B (NmB) disease in the United States. MATS data correlate with killing in the human complement serum bactericidal assay (hSBA) and predict the susceptibility of NmB strains to killing in the hSBA, the accepted correlate of protection for MenB-4C vaccine. A panel of 442 NmB United States clinical isolates (collected in 2000 to 2008) whose data were down weighted with respect to the Oregon outbreak was selected from the Active Bacterial Core Surveillance (ABCs; CDC, Atlanta, GA) laboratory. MATS results examined to determine strain coverage were linked to multilocus sequence typing and antigen sequence data. MATS predicted that 91% (95% confidence interval [CI₉₅], 72% to 96%) of the NmB strains causing disease in the United States would be covered by the MenB-4C vaccine, with the estimated coverage ranging from 88% to 97% by year with no detectable temporal trend. More than half of the covered strains could be targeted by two or more antigens. NHBA conferred coverage to 83% (CI₉₅, 45% to 93%) of the strains, followed by factor H-binding protein (fHbp), which conferred coverage to 53% (CI₉₅, 46% to 57%); PorA, which conferred coverage to 5.9%; and NadA, which conferred coverage to 2.5% (CI₉₅, 1.1% to 5.2%). Two major clonal complexes (CC32 and CC41/44) had 99% strain coverage. The most frequent MATS phenotypes (39%) were fHbp and NHBA double positives. MATS predicts over 90% MenB-4C strain coverage in the United States, and the prediction is stable in time and consistent among bacterial genotypes. IMPORTANCE The meningococcal antigen typing system (MATS) is an enzyme-linked immunosorbent assay (ELISA)-based system that assesses the levels of expression and immune reactivity of the three recombinant MenB-4C antigens and, in conjunction with PorA variable 2 (VR2) sequencing, provides an estimate of the susceptibility of NmB isolates to killing by MenB-4C-induced antibodies. MATS assays or similar antigen phenotype analyses assume importance under conditions in which analyses of vaccine coverage predictions are not feasible with existing strategies, including large efficacy trials or functional antibody screening of an exhaustive strain panel. MATS screening of a panel of NmB U.S. isolates (n = 442) predicts high MenB-4C vaccine coverage in the United States.

Emerging clinical experience with vaccines against group B meningococcal disease

The prevention of paediatric bacterial meningitis and septicaemia has recently entered a new era with the availability of two vaccines against capsular group B meningococcus (MenB). Both of these vaccines are based on sub-capsular proteins of the meningococcus, an approach that overcomes the challenges set by the poorly immunogenic MenB polysaccharide capsule but adds complexity to predicting and measuring the impact of their use. This review describes the development and use of MenB vaccines to date, from the use of outer membrane vesicle (OMV) vaccines in MenB outbreaks around the world, to emerging evidence on the effectiveness of the newly available vaccines. While recent data from the United Kingdom supports the potential for protein-based vaccines to provide direct protection against MenB disease in immunised children, further research is required to understand the breadth and duration of this protection. A more detailed understanding of the impact of immunisation with these vaccines on nasopharyngeal carriage of the meningococcus is also required, to inform both their potential to induce herd immunity and to preferentially select for carriage of strains not susceptible to vaccine-induced antibodies. Although a full understanding of the potential impact of these vaccines will only be possible with this additional information, the availability of new tools to prevent the devastating effect of invasive MenB disease is a significant breakthrough in the fight against childhood sepsis and meningitis.

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.

Immunogenicity and safety among laboratory workers vaccinated with Bexsero® vaccine

Neisseria meningitidis serogroup B is the most prevalent cause of invasive meningococcal disease in Europe and members of laboratories working on meningococci are at risk due to frequent handling. Recommendation for anti-meningococcal vaccination among these workers has been recently updated upon the licensure in Europe of Bexsero® vaccine. We tested the immunogenicity and safety of this vaccine among adults laboratory staff using the recommended schedule of 2 doses at 5 weeks interval. The vaccine was well tolerated in spite of frequent local side effects and all participants reported at least one side effect after each dose. Immunogenicity was evaluated 6 weeks and one year after the second dose. All participants showed increase in their bactericidal titers against the components of the vaccine 6 weeks after the second dose, however titers declined significantly one year later.