Functional activities and epitope specificity of human and murine antibodies against the class 4 outer membrane protein (Rmp) of Neisseria meningitidis

Antibodies against the class 4 outer membrane protein (OMP) from Neisseria meningitidis have been purified from sera from vaccinees immunized with the Norwegian meningococcal group B outer membrane vesicle vaccine. The human sera and purified antibodies reacted strongly with the class 4 OMP in immun oblots, whereas experiments with whole bacteria showed only weak reactions, indicating that the antibodies mainly reacted with parts of the class 4 mo lecule that were not exposed. The purified human anti-class 4 OMP antibodie s and the monoclonal antibodies (MAbs) were neither bactericidal nor opsoni c against live meningococci. Three new MAbs against the class 4 OMP were ge nerated and compared with other, previously described MAbs. Three linear ep itopes in different regions of the class 4 OMP were identified by the react ion of MAbs with synthetic peptides. The MAbs showed no blocking effect on bactericidal activity of MAbs against other OMPs. However, one of the eight purified human anti-class 4 OMP antibody preparations, selected from immun oblot reactions among sera from 27 vaccinees, inhibited at high concentrati ons the bactericidal effect of a MAb against the class 1 OMP. However, thes e antibodies were not vaccine induced, as they were present also before vac cination. Therefore, this study gave no evidence that vaccination with a me ningococcal outer membrane vesicle vaccine containing the class 4 OMP induc es blocking antibodies. Our data indicated that the structure of class 1 OM P does not correspond to standard P-barrel structures of integral OMPs and that no substantial portion of the OmpA-like C-terminal region of this prot ein is located at the surface of the outer membrane.