Investigation of correlates of protection against pharyngeal carriage of Neisseria meningitidis genogroups W and Y in the African meningitis belt

Abstract

BackgroundSerum bactericidal antibody titres that correlate with protection against invasive meningococcal disease have been characterised. However, titres that are associated with protection against acquisition of pharyngeal carriage of Neisseria meningitidis are not known.MethodsSera were obtained from the members of a household in seven countries of the African meningitis belt in which a pharyngeal carrier of N. meningitidis had been identified during a cross-sectional survey. Serum bactericidal antibody titres at baseline were compared between individuals in the household of the carrier who became a carrier of a meningococcus of the same genogroup during six months of subsequent follow-up and household members who did not become a carrier of a meningococcus of this genogroup during this period.ResultsSerum bacterial antibody titres were significantly higher in carriers of a serogroup W or Y meningococcus at the time of recruitment than in those who were not a carrier of N. meningitidis of the same genogroup. Serum bactericidal antibody titres to a strain of N. meningitis of the same genogroup as the index cases were no different in individuals who acquired carriage with a meningococcus of the same genogroup as the index case than in those who did not become a carrier during six months of follow-up.ConclusionSerum bacterial antibody titres to N. meningitidis of genogroup W or Y in the range of those acquired by natural exposure to meningococci of these genogroups, or with cross-reactive bacteria, are not associated with protection against acquisition of carriage with meningococci of either of these genogroups.

Narrative review of methods and findings of recent studies on the carriage of meningococci and other Neisseria species in the African Meningitis Belt

“…Sufficient episodes of transmission of NmW and NmY occurred within the study households to allow correlations to be made between SBA titre to NmW and NmY and acquisition of carriage with meningococci of the respective serogroup. No correlation was found, even [16] though some subjects had high SBA titres in the range of those found following vaccination [28].…”

Impact of Meningococcal B (4CMenB) Vaccine on Pharyngeal Neisseria meningitidis Carriage Density and Persistence in Adolescents

“…Whilst it's possible that non-groupable carriage has some role in producing protective SBA titers, it is generally accepted that the most important correlate of protection against meningococcal infection is the presence of serum bactericidal activity against the invasive strain. [36,37] In populations with low carriage prevalence similar to South Australia, it is likely that a much larger impact on clearance would be required to result in significantly reduced carriage prevalence. This is especially the case with carriage acquisition being similar between the vaccinated and unvaccinated students at 12 months following vaccination in our cohort.…”

Safety and immunogenicity of a pentavalent meningococcal conjugate vaccine containing serogroups A, C, Y, W, and X in healthy adults: a phase 1, single-centre, double-blind, randomised, controlled study

“…The PHE rSBA assays for serogroups A and C are internationally standardised assays; 26 the rSBA assay method was adapted for serogroups Y, W, and X, as previously published. [27][28][29] The target strains in the rSBA assays were: serogroup A F8238, serogroup C C11, serogroup Y S1975, serogroup W M01 240070, and serogroup X BF2/97. 27 Increases in serogroup C rSBA titres of eight times or more are deemed as an appropriate conservative threshold of protection in seronegative individuals, 30 and an increase in rSBA titres of 128 times or more has been proposed as an appropriate threshold for correlate of protection in seropositive individuals.…”