Cross-reacting serum opsonins to meningococci after vaccination.

The opsonic activity of sera from healthy volunteers immunized with an outer membrane vesicle vaccine prepared from a Neisseria meningitidis (class 3, 44/76, B:15:P1.7,16), characteristic of the present Norwegian epidemic, has been examined. A marked increase in the phagocytosis of class 3 and nontypeable strains of different serogroups, serotypes, and serosubtypes was demonstrated in the presence of postvaccination sera. Sera from vaccinees also caused a significant increase in leukocyte oxidative metabolism as measured by luminol-enhanced chemoluminescence during phagocytosis of class 3 and nontypeable meningococci. An increase in serum opsonins cross-reacting with class 2 (type 2a) meningococci of different serogroups was not observed, suggesting that future meningococcal outer membrane vesicle vaccine preparations should contain both class 2 and class 3 porins in geographic areas where both class 2 and class 3 strains cause disease.