Abstract

Immunisation of ddY mice with the purified ribosomal fraction of Neisseria gonorrhoeae was found to protect against intravaginal challenge with homologous organisms. This protection correlated with the presence of bactericidal antibody to purified ribosomal fraction in serum as well as in vaginal secretions. Analysis of the vaginal fluids from control mice and those immunised with purified ribosomal fraction showed that the enhanced elimination of gonococci in immune mice might be because of an early response of leucocytes generated by the reaction mediated by antibody and complement. Absorption studies showed that there was at least one major protective antigen in purified ribosomal fraction, other than cell surface substances such as lipopolysaccharide, outer membrane proteins, and pili. Bactericidal assays mediated by antibody and complement showed that matched samples of serum and vaginal fluid from immune mice had comparable gonococcidal activity, which was augmented by the effect of progesterone. Although delayed hypersensitivity was produced in immune mice that were resistant to N gonorrhoeae, the exact role of cellular immunity could not be clarified in this study. These results suggest that antibody to purified ribosomal fraction plays a major part in protection against gonococcal infection in the genital tract, and that such protection may entail both cellular immunity and hormonal changes.