Seroprevalence of bactericidal antibodies against serogroup B and C Meningococci in a University Hospital

Abstract

Meningococcus serogroup B (MenB), clonal complex 32 (cc 32), was the Brazilian epidemic strain of meningococcal disease (MD) in the 1990’s. Currently, meningococcus serogroup C (MenC), cc 103, is responsible for most of the cases of the disease in Brazil. The aim of this study was to investigate the seroprevalence of bactericidal antibody (SBA) against representative epidemic strains of MenC, (N753/00 strain, C:23:P1.22,14-6, cc103) and MenB, (Cu385/83 strain, B:4,7:P1.15,19, cc32) in students and employees of a university hospital in the State of Rio Grande do Sul (RS, Brazil). A second MenC strain (N79/96, C:2b:P1.5-2,10, cc 8) was used as a prototype strain of Rio de Janeiro’s outbreak that occurred in the 1990’s. Our previous study showed a 9% rate of asymptomatic carriers in these same individuals. A second goal was to compare the SBA prevalence in meningococcal carriers and non-carriers. Fifty-nine percent of the studied population showed protective levels of SBA titers (log2≥2) against at least one of the three strains. About 40% of the individuals had protective levels of SBA against N753/00 and Cu385/83 strains. Nonetheless, only 22% of the individuals showed protective levels against N79/96 strain. Significantly higher antibody levels were seen in carriers compared to non-carriers (P≤0.009). This study showed that, similar to other States in Brazil, a MenC (23:P1.22,14-6, cc103) strain with epidemic potential is circulating in this hospital. Close control by the Epidemiological Surveillance Agency of RS of the number of cases of MD caused by MenC strains in the State is recommended to prevent a new disease outbreak.

Production and Characterization of Bacterial Ghost Vaccine against Neisseria meningitidis

“…While measuring the antibody titer as a suitable indicator for the induction of antibodies, the SBA test is considered the hallmark of immunity against meningitis. The serum bactericidal titer is defined as the reciprocal serum dilution causing ≥50% killing of the bacteria [ 32 ].…”

Evaluating Functional Immunity Following Encapsulated Bacterial Infection and Vaccination

“…Although there has been effort to standardise Meningococcal B (MenB) SBA [30], no formal method has been established. One of the challenges for standardising SBA against Serogroup B is the diverse epidemiology of prevalent strains in different populations [31,32], making the choice of a 'universal' reference strain difficult. In addition, selection of a bacterial strain that is susceptible (i.e., the alternative and lectin activation pathways, which do not require an antibody) or resistant (i.e., the production of bacterial proteins that interfere with complement killing and/or the overproduction of bacterial polysaccharide) to complement killing may not be suitable for use in the assay [33].…”