Chlamydia trachomatis-specific interferon-γ-producing CD8 T-cells are associated with lower chlamydia bacterial load in reinfected women.

This study aimed to better understand the importance of CD8 T cell responses in protective immunity to chlamydia. In women evaluated for reinfection at a 3-month follow-up visit after treatment for chlamydia, the presence or magnitude of Chlamydia trachomatis-specific CD8 interferon-gamma (IFN-γ) responses to Momp and Pgp3 peptide pools was not associated with reinfection status, despite having an increased frequency of responses compared to C. trachomatis CD4-specific T cells. However, reinfected women with detectable interferon-gamma (IFN-γ)-producing CD8 T cells had lower C. trachomatis bacterial load compared to women without these CD8 T cell responses. Moreover, the frequency of IFN-γ-producing CD8 T cells was inversely associated with C. trachomatis bacterial load. We further determined that C. trachomatis-specific IFN-γ-producing CD8 T cells were predominately late differentiated effector memory T cells that re-expressed CD45RA (Temra; CCR7-CD45RA+) or effector memory T cells (Tem; CCR7-CD45RA-). Together, these data support the concept that CD8 T cells may contribute to protective immunity against chlamydia in women.