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4CMenB vaccine coverage of invasive serogroup B meningococci collected in Belgium between 2016 and 2022.

Neisseria meningitidis infections can cause life-threatening meningitis and septicemia. In Europe, serogroup B (MenB) is the leading cause of invasive meningococcal disease (IMD), particularly in young children. Genomic surveillance of circulating MenB strains through whole genome sequencing (WGS) provides a powerful tool to assess the potential impact of vaccination strategies, including the 4CMenB vaccine, which is available for infants from 2 months of age. Here, we present a retrospective WGS-based analysis of clinical MenB IMD cases (n = 311) recovered in Belgium from 2016 to 2022 by the Belgian National Reference Center. High-quality WGS data were obtained for 281 of these strains, demonstrating high genetic diversity of the antigen targets included in the 4-component meningococcal serogroup B vaccine 4CMenB (fHbp, PorA, NHBA and NadA) and at the 4CMenB Antigen Sequence Types (BAST) level. Novel antigen combinations, not yet assigned a BAST ID, were detected in 23.5% of isolates. Vaccine coverage was predicted using the Genetic Meningococcal Antigen Typing System (gMATS) and the Meningococcal Deduced Vaccine Antigen Reactivity (MenDeVAR) index. Of the 281 strains, 79.5% (lower limit-upper limit: 68.0-91.5%) were predicted to be covered by the vaccine by gMATS, and 80.7% (lower limit-upper limit: 66.5-95.4%) by MenDeVAR. No evidence of variation in vaccine coverage was found throughout the study period nor between different age groups, demonstrating the broad applicability of 4CMenB. This study highlights the benefits of a pathogen surveillance program and the need for experimental characterization of continuously evolving antigenic subvariants of Neisseria meningitidis.

Humans

Exploiting Real-Time Genomic Surveillance Data To Assess 4CMenB Meningococcal Vaccine Performance in Scotland, 2015 to 2022.

The United Kingdom implemented the first national infant immunization schedule for the meningococcal vaccine 4CMenB (Bexsero) in September 2015, targeting serogroup B invasive meningococcal disease (IMD). Bexsero contains four variable subcapsular proteins, and postimplementation IMD surveillance was necessary, as nonhomologous protein variants can evade Bexsero-elicited protection. We investigated postimplementation IMD cases reported in Scotland from 1 September 2015 to 30 June 2022. Patient demographics and vaccination status were combined with genotypic data from the causative meningococci, which were used to assess vaccine coverage with the meningococcal deduced vaccine antigen reactivity (MenDeVAR) index. Eighty-two serogroup B IMD cases occurred in children >5 years of age, 48 (58.5%) of which were in unvaccinated children and 34 (41%) of which were in children who had received ≥1 Bexsero dose. Fifteen of the 34 vaccinated children had received one dose, 17 had received two doses, and two had received three doses. For 39 cases, meningococcal sequence data were available, enabling MenDeVAR index deductions of vaccine-preventable (M-VP) and non-vaccine-preventable (M-NVP) meningococci. Notably, none of the 19 of the children immunized ≥2 times had IMD caused by M-VP meningococci, with 2 cases of NVP meningococci, and no deduction possible for 17. Among the 15 children partially vaccinated according to schedule (1 dose), 7 were infected by M-VP meningococci and 2 with M-NVP meningococci, with 6 for which deductions were not possible. Of the unvaccinated children with IMD, 40/48 were ineligible for vaccination and 20/48 had IMD caused by M-VP meningococci, with deductions not being possible for 14 meningococci. IMPORTANCE This study demonstrates the value of postimplementation genomic surveillance of vaccine-preventable pathogens in providing information on real-world vaccine performance. The data are consistent with 2 and 3 doses of Bexsero, delivered according to schedule, providing good protection against invasive disease caused by meningococci deduced from genomic data to be vaccine preventable. Single doses provide poorer protection to infants. In practical terms, these data can provide public health reassurance when vaccinated individuals develop IMD with non-vaccine-preventable variants. They further indicate that additional testing is needed on variants for which no immunological data exist to improve estimates of protection, although these data suggest that the uncharacterized variants are unlikely to be covered by Bexsero. Finally, the confirmation that incomplete or absent doses in infancy lead to reduced protection supports public health and general practitioners in promoting vaccination according to schedule.

Infant

Investigating genetic, antigenic, and structural diversity in the Neisseria gonorrhoeae outer membrane protein, PorB: implications for vaccine design.

UNLABELLED: Vaccines targeting Neisseria gonorrhoeae are needed to reduce disease burden and help address the problem of antimicrobial resistance, with an understanding of relationships between gonococcal genetics and molecules influencing diversity, infection, and the immune response essential for developing effective vaccine formulations. Whole-genome sequence data can be used to investigate these relationships among thousands of gonococcal isolates, allowing the study of antigenic diversity on a population scale. Such analyses typically examine antigenic diversity occurring in complete protein sequences, generating mean diversity indices and phylogenetic analyses that can inform on vaccine potential; however, to detect and measure the immune responses elicited, epitope characterization within an antigen helps guide vaccine formulations, with epitopes commonly located in surface-exposed regions of a protein. Here, we analyzed the genetic diversity of the major gonococcal antigen, PorB, in WGS from 22,227 N. gonorrhoeae isolates. We characterized the diversity of all eight surface-exposed outer membrane loops, or variable regions (VRs), and generated a PorB VR subtyping scheme to facilitate the global and temporal detection of circulating PorB subtypes. These analyses identified the presence of dominant VR combinations that persisted over time, indicative of (i) epistatic interactions between VRs and (ii) positive selection. Strain-specific, anti-PorB IgG responses directed toward distinct VR subtypes were detected in sera obtained from participants vaccinated with 4CMenB. The deconstruction of PorB into each surface-exposed loop provides a powerful approach for evaluating vaccine candidates: the methods used here allow immunodominant regions to be detected, which is invaluable for further vaccine investigations. IMPORTANCE: In the context of rising global gonorrhea cases, the development of vaccines becomes a priority; however, N. gonorrhoeae antigenic diversity and its ability to evade the immune system complicate vaccine development. This study characterizes the genetic diversity of the outer membrane protein, PorB, a key component of the outer membrane and a major gonococcal antigen. Using genomics and machine-learning techniques, this research identified dominant PorB variants that drive the immune response, proposing potential vaccine candidates and improving our understanding of the evolutionary forces maintaining genome structure and biological fitness. Understanding these processes is crucial for designing vaccines that effectively target N. gonorrhoeae and combat the spread of multidrug-resistant gonococci.

Neisseria gonorrhoeae