Nasal and vaginal vaccinations have differential effects on antibody responses in vaginal and cervical secretions in humans

Sexually transmitted diseases are a major health problem worldwide, but the re is still a lack of knowledge about how to induce an optimal immune respo nse in the genital tract of humans. In this study we vaccinated 21 voluntee rs nasally or vaginally with the model mucosal antigen cholera toxin B subu nit and determined the level of specific immunoglobulin A (IgA) and IgG ant ibodies in vaginal and cervical secretions as well as in serum. To assess t he hormonal influence on the induction of antibody responses after vaginal vaccination, we administered the vaccine either independently of the stage in the menstrual cycle or on days 10 and 24 in the cycle in different group s of subjects. Vaginal and nasal vaccinations both resulted in significant IgA and IgG anti-cholera toxin B subunit responses in serum in the majority of the volunteers in the various vaccination groups. Only vaginal vaccinat ion given on days 10 and 24 in the cycle induced strong specific antibody r esponses in the cervix with 58-fold IgA and 16-fold IgG increases. In contr ast, modest responses were seen after nasal vaccination and in the other va ginally vaccinated group. Nasal vaccination was superior in inducing a spec ific IgA response in vaginal secretions, giving a 35-fold increase, while v aginal vaccination induced only a 5-fold IgA increase. We conclude that a c ombination of nasal and vaginal vaccination might be the best vaccination s trategy for inducing protective antibody responses in both cervical and vag inal secretions, provided that the vaginal vaccination is given on optimal time points in the cycle.