Antigen-specific serotyping of Neisseria gonorrhoeae. I. Use of an enzyme-linked immunosorbent assay to quantitate pilus antigens on gonococci.

Purified pili from Neisseria gonorrhoeae were used in an enzyme-linked immunosorbent assay (ELISA) to quantitate human or rabbit antibodies to pili; amounts of pilus antigen on different gonococci were quantitated, and yields of pili during purification were determined in ELISA by the degree of inhibition of optical density. The amount of pilus antigen expressed on the surface of colony type 1 or 2 gonococci of three different strains varied from 450 to 9,000 ng/600 microliter of a 200-Klett unit suspension. The quantity of pilus antigen was correlated directly with the extent of piliation as determined by electron microscopy. No pilus antigen was found by ELISA in colony type 4 organisms (devoid of pili) of three different strains. No more than 10% shared antigenicity was observed for antigenically different pili. Present purification procedures for gonococcal pili provide a yield of approximately 15%. ELISA may allow better evaluation and quantitation of the potential roles of antibody to pili in the killing or opsonization of gonococci or in the inhibition of gonococcal attachment to human cells.