Western blot analysis of gonococcal serogrouping reagents

The W class antisera used in the coagglutination method of serogrouping Neisseria gonorrhoeae were analysed using sodium dodecyl sulphate polyacrylamide gel electrophoresis and western blot transfers. All were found to contain antibodies to the homologous protein II as well as antibodies to protein I group antigens. Examination of local isolates showed that some strains owed their reaction with coagglutination reagents to epitopes on their protein II not their protein I. How this may lead to difficulties when using coagglutination patterns to subdivide the W groups is discussed.