SERUM BACTERICIDAL ACTIVITY IN A SECONDARY-SCHOOL POPULATION FOLLOWING AN OUTBREAK OF MENINGOCOCCAL DISEASE - EFFECTS OF CARRIAGE AND SECRETOR STATUS

Sera obtained from 106 children following an outbreak of Neisseria men ingitidis (B:4:P1.15) were screened for bactericidal antibodies agains t isolates of meningococci and Neisseria lactamica. Most had high titr es of antibodies to N. lactamica and N. meningitidis NG:4:- but not to capsulate isolates: B:4:P1.15; B:15:P1.16; B:4:-; C:4:-. Bactericidal activity was higher for both carriers and secretors but the differenc es were not significant. Bactericidal activity was not associated with total or specific IgA or IgM. Carriers had significantly higher level s of IgG to N. lactamica but not to NG:4:- in sera with bactericidal a ctivity for each of the capsulate strains. Among non-carriers, higher levels of IgG to N. lactamica were associated with killing of B:4:P1.1 5 and B:4:-. Secretors' sera with bactericidal activity had significan tly higher levels of IgG to N. lactamica compared with sera that were not bactericidal. This was not observed among non-secretors. Antibodie s to the outbreak strain were adsorbed by all Neisseria isolates teste d and absorption of sera with N. lactamica alone completely removed th e bactericidal activity against the outbreak strain.