Evidence of Serum Antibodies to Neisseria gonorrhoeae Before Gonococcal Infection

To characterize the serum antibody response to urethral infection with Neisseria gonorrhoeae, we examined pre- and postinfection sera from 13 men experiencing their first gonococcal infection. Using western blot analysis, we found that nine of 13 patients developed new serum IgG antibodies against one or more antigens, most commonly against lipooligosaccharide, followed in order by the H.8-antigen, pili, proteins I and II, and protein III. Twelve of 13 patients had preexisting IgG to gonococcal antigens, most commonly against the H.8 antigen, followed by pili, lipooligosaccharide, protein I, and protein III. Using serum obtained from other patients before and after nasopharyngeal carriage of Neisseria meningitidis, we demonstrated that carriage resulted in serum IgG cross-reactive to N. gonorrhoeae antigens. This is a likely explanation for the presence of antigen-specific antibody in preinfection sera.