Demonstration of antigenic heterogeneity of Neisseria gonorrhoeae pili antigens using human sera in the test system.

Antigenic heterogeneity of gonococcal pili using human sera in the test system was demonstrated by means of indirect haemagglutination (IHA) inhibition studies. The reactivities of sera from 104 females with current gonococcal infection were compared by the IHA test using different pili preparations as antigens. Sera and gonococcal strains were collected from 365 patients. Pili were purified from strains infecting patients who met the following three requirements: 1) no history of previous gonococcal infection(s), 2) an infection that had lasted a week or more, 3) a seronegative result when tested by the IHA test using pili from Buchanan's strain 2686 as antigen. Each patient's serum was tested against pili produced by the gonococcal strain infecting this particular patient. A seropositive reaction obtained by using pili antigen from the strain infecting the seronegative (strain 2686) patient indicates an antigenically heterogeneous pili preparation. Two such strains, antigenically different from one another and from strain 2686, were found among 22 pili preparations investigated.