Protection against group B meningococcal disease: evaluation of serotype 2 protein vaccines in a mouse bacteremia model

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Abstract
A mouse bacteremia model was used to evaluate immunogenicity and protection against challenge provided by 5 different meningococcal serotype 2 vaccines. Mice vaccinated with serotype 2 protein vaccines had levels of bacteremia reduced by at least 100-fold after challenge with group B serotype 2 meningococci. Mice vaccinated with serotype 2 protein vaccine and challenged with group C serotype 2 meningococci showed 10-fold or less reduction in bacteremia. Vaccines were primarily serotype specific since no increase in protection was observed after challenge with group B serotype 4 or group C non-typable meningococci. Serotype 2 antibody levels, measured by the bactericidal assay and the enzyme-linked immunosorbent assay 3 wk after immunization, demonstrated a graded dose-response which correlated with protection up to 40 wk after vaccination with a single 10 or 25 .mu.g dose of serotype 2 protein vaccine. A 1 .mu.g booster dose of serotype 2 vaccine, given 2 wk after primary immunization, significantly increased bactericidal (P < 0.01) and enzyme-linked immunosorbent assay (P < 0.02) titers. Serotype 2 protein vaccines may be stable and immunogenic and protect mice against challenge with group B serotype 2 meningococci.