Evidence for cGAS-STING Signaling in the Female Genital Tract Resistance to Chlamydia trachomatis Infection

Sexually transmitted Chlamydia trachomatis can ascend to the upper genital tract due to its resistance to innate immunity in the lower genital tract. C. trachomatis can activate the cGAS-STING signaling pathway in cultured cells via either cGAS or STING. This study was designed to evaluate the role of the cGAS-STING pathway in innate immunity against C. trachomatis in the mouse genital tract. Following intravaginal inoculation, C. trachomatis significantly declined by day 5 following a peak infection on day 3, while the mouse-adapted Chlamydia muridarum continued to rise for >1 week, indicating that C. trachomatis is susceptible to the innate immunity in the female mouse genital tract. This conclusion was supported by the observation of a similar shedding course in mice deficient in adaptive immunity. Thus, C. trachomatis can be used to evaluate innate immunity in the female genital tract. It was found that mice deficient in either cGAS or STING significantly increased the yields of live C. trachomatis bacteria on day 5, indicating an essential role of the cGAS-STING signaling pathway in innate immunity of the mouse genital tract. Comparison of live C. trachomatis bacteria recovered from different genital tissues revealed that the cGAS-STING-dependent immunity against C. trachomatis was restricted to the mouse lower genital tract regardless of whether C. trachomatis was inoculated intravaginally or transcervically. Thus, we have demonstrated an essential role of the cGAS-STING signaling pathway in innate immunity against chlamydial infection, laying a foundation for further illuminating the mechanisms of the innate immunity in the female lower genital tract.