VACCINES. A mucosal vaccine against Chlamydia trachomatis generates two waves of protective memory T cells.

Genital Chlamydia trachomatis (Ct) infection induces protective immunity that depends on interferon-γ-producing CD4 T cells. By contrast, we report that mucosal exposure to ultraviolet light (UV)-inactivated Ct (UV-Ct) generated regulatory T cells that exacerbated subsequent Ct infection. We show that mucosal immunization with UV-Ct complexed with charge-switching synthetic adjuvant particles (cSAPs) elicited long-lived protection in conventional and humanized mice. UV-Ct-cSAP targeted immunogenic uterine CD11b(+)CD103(-) dendritic cells (DCs), whereas UV-Ct accumulated in tolerogenic CD11b(-)CD103(+) DCs. Regardless of vaccination route, UV-Ct-cSAP induced systemic memory T cells, but only mucosal vaccination induced effector T cells that rapidly seeded uterine mucosa with resident memory T cells (T(RM) cells). Optimal Ct clearance required both T(RM) seeding and subsequent infection-induced recruitment of circulating memory T cells. Thus, UV-Ct-cSAP vaccination generated two synergistic memory T cell subsets with distinct migratory properties.