Letter to the editor: Importance of serum bactericidal activity for estimating the breadth of protection for new meningococcal vaccines

Abstract

To the editor: Brehony and colleagues [1] recently reported their investigation of six Neisseria meningitidis serogroup B (NmB) vaccines by deducing the prevalence of the vaccine components in isolates represented in publicly accessible sequence repositories of NmB. Based on the frequency of exact match of deduced peptide sequences in the databases to at least one component of each vaccine, and by assessing published data, the authors estimated the breadth of strain coverage. Their findings led them to conclude that meningococcal vaccines with multiple antigens would provide greater breadth of coverage against meningococcal disease. However, their evaluation did not incorporate important information about the diversity of factor H binding protein (fHBP) variants and the demonstration of protective immune responses against antigenically diverse MnB invasive disease strains following vaccination with Trumenba. Consequently, the authors’ analysis underestimates the potential for vaccine benefit provided by this licensed vaccine. We provide here a description of published data, including results that use the recognised correlate of protection for NmB, serum bactericidal activity measured using serum bactericidal assays performed with human complement (hSBA) [2,3]. This correlation was first validated in large clinical studies using outer membrane vesicle (OMV) vaccines that confer protection via induction of immune response directed against the PorA antigen of NmB [4]. Protection is essentially restricted to strains expressing the matched PorA sequence in the vaccine [5], thus the approach used by the authors to estimate vaccine strain coverage is appropriate for PorA based vaccines, such as the experimental vaccine NonaMen, as described.