Antigenic Variation of Outer Membrane Protein II in Colonial Variants of Neisseria gonorrhoeae P9

Abstract

Antibodies were detected by an enzyme-linked immunosorbent assay (ELISA) in sera from rabbits immunized with outer membranes from colonial opacity variants of N. gonorrhoeae P9. ELISA-inhibition experiments with purified antigens revealed approximately equal proportions of antibodies directed against each of the 3 major surface antigens, lipopolysaccharide, the major outer membrane protein (protein I) and protein II, the variable protein associated with colonial opacity. Inhibition experiments with intact gonococci showed considerable surface antigenic diversity which could be correlated with differences between the protein II species present. Despite their considerable structural homology, different protein II species from colonial variants of the same strain showed little cross-reactivity with specific anti-protein II sera, demonstrating the considerable variation in that part of the antigen which is exposed on the surface of the gonococcus and is closely involved in pathogenic mechanisms.