Serological correlates of protection against meningococci in a cohort of university students, before and during an outbreak of serogroup C infection.

The association between individual meningococcal antigens and the development of protective immunity to both serogroup C and B meningococci was studied before and during an outbreak of serogroup C infection among university students. Persons who became infected showed, in serum taken either before infection or on admission to the hospital, low levels of bactericidal activity against the outbreak strain; patients who survived infection developed bactericidal activity that correlated with production of antibodies to serogroup C capsular polysaccharide but not to either lipopolysaccharide or major outer-membrane proteins. Uninfected classmates also showed a strong correlation between bactericidal activity and the presence of anti-capsular antibodies. In contrast, bactericidal activity against serogroup B did not correlate with the presence of antibodies to capsular polysaccharide but did correlate with antibodies reacting with the porin proteins PorA and PorB. These studies support the introduction of conjugate MenC vaccines, validate strategies for prevention of serogroup B infection that are based on vaccines containing PorA, and suggest that PorB may also be an important component of such vaccines.