Infection resistance dips during ovulation

High levels of estradiol (E2), present during ovulation and immediately after, diminish a woman's ability to protect against infection, according to a recent study from Spain and Austria. This means that women are more susceptible to fungal infection, such as with Candida albicans (C albicans), or sexually transmitted diseases, such as HPV or HIV, during ovulation than at any other time during the reproductive cycle.

To test the hypothesis, researchers set up a model using C albicans and mice. They found that bilaterally ovariectomized mice treated with E2 and injected with a nonlethal dose of C albicans showed a dose-dependent reduction in survival (25% vs 65%) compared with mice not treated with E2. Although most of the control animals survived the infection, only 50% to 70% of the E2-treated mice did so.

Both in vivo and ex vivo models demonstrated that E2-treated mice had a diminished ability to trigger a Th17 immune response to C albicans antigens. The Th17 cellular immune response is essential to a host's protective reaction to fungi; its deregulation may worsen fungal infections significantly. As the authors noted, E2 turned a nonvirulent fungal strain into a disease-causing pathogen.

Relloso M, Aragoneses-Fenoll L, Lasarte S, et al. Estradiol impairs the Th17 immune response against Candida albicans. J Leukoc Biol. 2012;91(1):159-165.