Type-specific antigens of group A Neisseria meningitidis: lipopolysaccharide and heat-modifiable outer membrane proteins

Abstract

The solid-phase radioimmunoassay inhibition method was used to analyze the noncapsular surface antigens of group A N. meningitidis for type specificity. By use of antisera prepared against group A strains, 3 serologically distinct lipopolysaccharide antigens and 5 outer membrane protein antigens were identified among group A strains from a variety of geographical origins. Two lipopolysaccharide antigens were unique to group A strains while the 3rd was similar to those on strains of other meingococcal serogroups. Fractionation of outer membrane proteins in the presence of 2% sodium deoxycholate followed by quantitative inhibition of the typing reactions with the subfractions revealed that the protein responsible for type specificity was not the principal outer membrane protein, but most likely, the 31,000 dalton, heat-modifiable outer membrane protein. Thus, although group A strains may share a common principal outer membrane protein, typing is feasible using other surface antigens. In a survey of 82 group A strains, 93% were typable with respect to outer membrane proteins.