Immunity in infection with Neisseria gonorrhoeae: duration and serological response in the chimpanzee

Relative and absolute resistance to urethral and pharyngeal infection with Neisseria gonorrhoeae persisted for up to two years in male chimpanzees parenterally immunized with a colony type 2 gonococcal antigen. Twelve additional adult males were immunized with either a colony type 1 gonococcal antigen or a sham diluent before being challenged with the immunizing isolate of N. gonorrhoeae. Serum specimens were obtained throughout the immunization procedure and tested for indirect fluorescent, bactericidal, microhemagglutinating, and complement-fixing antibody to the immunizing isolate of N. gonorrhoeae. The serological response measured by the indirect fluorescent antibody and serum bactericidal tests correlated most closely with the resistance of individual chimpanzees when they were challenged in the pharynx and urethra with graduated doses of N. gonorrhoeae one month after the last immunization. In this study, the resistance of the immunized chimpanzees to urethral infection with N. gonorrhoeae varied from one to greater than 1,000 times that of sham-injected controls.