Effects of sexual dimorphism and estrous cycle on murine Clostridioides difficile infection.

Clostridioides difficile infection (CDI) causes the majority of identifiable antibiotic-associated diarrhea. Epidemiological studies have shown that biological human females are more susceptible to CDI than males. In this study, we show that female mice developed more severe CDI than males under all conditions tested. We found time-delayed effects of the female estrus cycle on CDI. Indeed, animals in proestrus at any time during CDI progression developed severe signs 1-2 days later. In contrast, animals that were in the estrus stage were protected. Consistent with the delayed effect of the estrous cycle on CDI, we found that pre-infection levels of the sexual hormone prolactin (PRL), immunoglobulin IgG2b, cytokine IL-1β, cytokine G-CSF, and chemokine KC (CXCL1) were the primary nodes of a complex network that correlated with CDI symptomatology on the day after spore challenge. Similarly, we found that the pre-infection levels of sex hormone progesterone, sex hormone luteinizing hormone (LH), immunoglobulin IgG1, chemokine eotaxin, and chemokine IP-10 (CXCL10) were the primary network nodes that affected CDI severity, but with a 2-day delay. As expected, early post-infection levels of immunoglobulins, cytokines, and chemokines formed a hormone-independent network that concurrently correlated with CDI severity. Interestingly, early post-infection levels of FSH, together with cytokine IL-1β and chemokine KC (CXL1), were the main nodes of a network that affected CDI 2 days later, during the recovery phase of the infection. In summary, we show that murine female sexual hormones affect CDI progression, probably by affecting the immune system both before infection and during disease development.