Homogeneity of protein serotype antigens in Neisseria meningitidis group A.

Serotype antigens (STA), which have been shown to be constituents of outer-membrane protein, were extracted from group A meningococci with 0.2 M LiCl and pelleted by centrifugation at 150,000 X g. The STAs from 100 group A strains, which had been isolated from cases and carriers in various geographical locations, were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Every STA produced three major protein bands with molecular weights of approximately 35,000, 39,000, and 45,000, respectively. This SDS-PAGE pattern is clearly distinct from that produced by the serotype of group B and C meningococci most commonly isolated from cases (group B type 2 and group C type 2). The group A STAs were also indistinguishable by immunodiffusion. However, differences in bactericidal reactions were demonstrated, suggesting that there are other antigens that play a role in antibody response.