Role of protein serotype antigens in protection against disease due to Neisseria meningitidis.

Evidence is provided for the protective effects of antibody to noncapsular antigens in immunity to meningococcal disease. Serotype 2 strains were associated with 50% of disease due to group B Neisseria meningitidis in Europe. The amount of serotype antibody in normal individuals is related to age, and adult levels are reached by about 10 years of age. Children under two years of age who have recovered from disease due to groups B and CN. meningitidis of serotype 2 make antibody to serotype 2; this fact indicates the potential immunogenicity of the serotype antigen in young children. The isolated serotype 2 antigen injected into rabbits elicited bactericidal antibody that was only weakly opsonic. Guinea pigs that were infected via spring implants with serotype 2 N. meningitidis developed antibody to serotype 2. After clearance of infection these animals became resistant to challenge with serotype 2 strains of groups B and C N. meningitidis. This serotypes-specific immunity to reinfection persisted for at least four months.