Identification of Chlamydia trachomatis Antigens Recognized by T Cells From Highly Exposed Women Who Limit or Resist Genital Tract Infection.

BACKGROUND: Natural infection induces partial immunity to Chlamydia trachomatis Identification of chlamydial antigens that induce interferon γ (IFN-) secretion by T cells from immune women could advance vaccine development.
METHODS: IFN-γ production by CD4+ and CD8+ peripheral blood T cells from 58 high-risk women was measured after coculture with antigen-presenting cells preincubated with recombinant Escherichia coli expressing a panel of 275 chlamydial antigens. Quantile median regression analysis was used to compare frequencies of IFN-γ responses in women with only cervical infection to those in women with endometrial infection and frequencies in women who remained uninfected for over 1 year to those in women who developed incident infection. Statistical methods were then used to identify proteins associated with protection.
RESULTS: A higher median frequency of CD8+ T-cell responses was detected in women with lower genital tract chlamydial infection, compared with those with upper genital tract chlamydial infection (13.8% vs 9.5%; P =04), but the CD4+ T-cell response frequencies were not different. Women who remained uninfected displayed a greater frequency of positive CD4+ T-cell responses (29% vs 18%; P < .0001), compared with women who had incident infection, while the frequencies of CD8+ T-cell responses did not differ. A subset of proteins involved in central metabolism, type III secretion, and protein synthesis were associated with protection.
CONCLUSIONS: Investigations in naturally exposed women reveal protective responses and identify chlamydial vaccine candidate antigens.