Protective efficacy of hybridoma type-specific antibody against experimental infection with group-B Streptococcus.

Murine monoclonal antibodies to group-B Streptococcus type III were developed by fusion of splenic lymphocytes from immunized BALB/c mice with the mouse-myeloma cell line SP 2/0. The four type III-specific antibodies, which were of the IgM class, protected neonatal rats against intraperitoneal infection with homologous-type group-B streptococci; survival rates were 95%-100% for protected rats but only 17% for unprotected rats. One antibody preparation offered excellent protection against any of five type-III strains employed. Monoclonal antibody provided protection when administered 4, 8, or 12 hr after infection, although delayed administration was less efficacious against more virulent strains. Monoclonal IgM also protected against intranasal inoculation of bacteria. These results indicate the potential therapeutic efficacy of monoclonal antibody in neonatal group-B streptococcal disease, but further laboratory investigations must precede clinical investigation of monoclonal or polyclonal antibody therapy in humans.