Systemic and Secretory Humoral Immunity in the Normal Human Vaginal Tract

Abstract

The molecular status of Abs in the vaginal fluid is reconsidered as a basis for immunization strategies for women's vaccination against HIV. Analysis of separated immunogiobulins (Igs) shows a large proportion of uncleaved IgG, whereas the low amount of IgA includes SIgA, monomers and fragments. SIgM is at a very low level, while free SC molecules are abundant. In addition to the already documented local synthesis, vaginal IgG contains serum-derived tetanus antitoxins. The IgG could reach the lumen by diffusion, and/or be transported by an Fc receptor-associated mechanism as suggested by the subclass imbalance in favour of the IgGl isotype. Vaginal SIgA contains very low levels of antibodies to the cell-wall carbohydrates from a dental caries-associated streptococcus confirming the participation of the secretory immune system. In addition, the low percentage of IgA2 suggests that a proportion of vaginal SIgA can also derive from actively transported serum polymers. In agreement with our previous studies showing induction of vaginal tetanus antitoxins by intramuscular immunization, these results are in favour of classical parenteral vaccinations to induce protection of the human vagina.