Antigen-Specific CD4 T cells Protect Against Reproductive Pathology by Subverting Chlamydia-specific CD8 T cell Response

Abstract

We have demonstrated previously that CD4 T cells are protective whereas CD8 T cells cause reproductive pathology following genital chlamydial infection. In this study, we explored the interactions of these cell types in context of vaccine-mediated protection. We evaluated three immunization regimens: live-chlamydial elementary body intranasal (EB-i.n.), live-EB i.m. (EB-i.m.), and irrelevant antigen bovine serum albumin i.n. (BSA-i.n.) that induced near-total (90%), partial (50%), and no (0%) protection, respectively against oviduct pathology following i.vag. C. muridarum challenge in C57BL6/J animals. We found no differences in Chlamydia-specific IFN-g, TNF-α, or IL-17 response from purified splenic CD8 T cells on days 7, 14, and 21 after immunization. We further evaluated Chlamydia-specific splenic CD8 T cell responses on days 3, 6, 9, and 12 following i.vag. chlamydial challenge. All groups of challenged animals displayed comparable induction of Ag-specific CD8 T cell cytokine responses on day 6 after challenge. As early as day 9 after challenge, Ag-specific IFN-g and TNF-α production from CD8 T cells was significantly reduced in EB-i.n.-immunized mice, and on day 12, both EB-i.n.- and EB-i.m.-immunized animals displayed minimal Ag-specific TNF-a production, compared to enhanced TNF-a production from CD8 T cells in BSA-i.n. immunized animals. Furthermore, adoptive transfer of Chlamydia-specific CD4 T cells at the time of genital infection induced significant reduction in Chlamydia-specific splenic CD8 T cell response on day 12 after challenge. In summary, these results suggest that Ag-specific CD4 T cells subvert a pathogenic Chlamydia-specific CD8 T cell response to protect against reproductive pathology.