Safety and immunogenicity of a Neisseria meningitidis type 2 protein vaccine in animals and humans.

Two Neisseria meningitidis vaccines consisting principally of outer membrane protein (lot 138I-0) or outer membrane protein plus group C polysaccharide (lot 138I-M1) were prepared from the group C type 2 strain 138I. Lipopolysaccharide and lipid were removed by gel filtration in the presence of sodium deoxycholate. The vaccines were found to be nontoxic and nonpyrogenic in animals. They provided active protection in mice against mucin-enhanced killing by group B type 2 meningococci and induced good titers of type-specific bactericidal and hemagglutinating antibodies in rabbits. In five volunteers the vaccines were well tolerated and induced significant increases in serum bactericidal activity against both group C and group B strains. Three of five volunteers had a two- to fourfold increase in antibodies to the outer membrane proteins, but these antibodies did not appear to have bactericidal activity. The bactericidal antibodies to both group B and group C strains were directed against the capsular polysaccharides.