IMMUNE-RESPONSE OF BRAZILIAN CHILDREN TO A NEISSERIA-MENINGITIDIS SEROGROUP-B OUTER-MEMBRANE PROTEIN VACCINE - COMPARISON WITH EFFICACY

Since 1986, serogroup B Neisseria meningitidis has caused approximatel y 80% of of the meningococcal disease in Brazil. In 1988, an epidemic caused by N. meningitidis B:4:P1.15 was recognized in the greater Sao Paulo area of Brazil. The Sao Paulo state government decided to vaccin ate children from 3 to 83 months of age with a vaccine consisting of s erotype 4 outer membrane protein acid group C meningococcal polysaccha ride that was produced in Cuba. About 2.7 million children were vaccin ated during two immunization campaigns conducted in 1989 and 1990. Bec ause of this, a case control study was designed to determine vaccine e fficacy against group B meningococcal disease. The purpose of our stud y was to compare the antibody response with the protection from diseas e estimated from the case-control study. We measured the immune respon ses of vaccinees by enzyme-linked immunosorbent assay (ELISA), immunob lot, and bactericidal assay. The development of bactericidal antibodie s was age dependent and in good agreement with the results of the case -control study. Only 40% of vaccinees showed fourfold or greater incre ases in bactericidal antibody titers after vaccination. A poor correla tion between antibody levels detected by ELISA and those by bactericid al assay was found. Immunoblot analysis showed that about 50% of the s erum samples with bactericidal titers higher than 1:4 were reactive wi th class 1 outer membrane protein. We conclude that the bactericidal a ssay is a good, laboratory-based, functional assay for the study of va ccine immunogenicity and that an effective solution to group B meningo coccal disease remains to be demonstrated.