More than one antigen contributes to the immunogenicity of Neisseria gonorrhoeae in the guinea pig chamber model.

Gonococci adapted to growth in guinea pig chambers [strain BS4 (agar)] were predominantly smooth organisms and produced a type-specific antigen. A vaccine prepared by treating these gonococci with formalin, protected guinea pig chambers against homologous challenge in contrast to a similarly treated laboratory strain (BSDH) which had been selected in vitro from the same parent strain and which did not produce the type-specific antigen. Surface washes of BS4 (agar) contained the type-specific antigen but attempts to immunize guinea pigs with complexes of rabbit antibody with this antigen excised from gels failed. However, good immunity could be produced by combining such complexes with formalin-killed rough gonococci (strain BS4R), lacking the type-specific antigen, which were found in some chambers of challenged guinea pigs that had been immunized with the complexes. Hence, at least two antigens -- one the type-specific antigen and the other(s) possessed by both BS4 (agar) and BS4R -- are needed for immunogenicity. Surface washes of BS4 (agar) and BS4R contained three antigens, distinct from the type-specific antigen, which might complement it in producing immunity. Similar antigens were present in surface washes of five fresh isolates from human urethral pus, but only a few organisms from these isolates possessed antigens similar to the type-specific antigen. The variability of gonococci in antigenicity, immunogenicity and probably virulence is discussed.