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Updated: Apr 30, 2026
Rodent Estrous Cycle Monitoring Utilizing Vaginal Lavage: No Such Thing As a Normal Cycle
Published on: August 30, 2021
SHIV susceptibility changes during the menstrual cycle of pigtail macaques
Ellen N Kersh1, Tara Henning, Sundaram A Vishwanathan
1Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Background:
Hormonal changes during menstrual cycling may affect susceptibility to HIV.
Methods:
We determined the simian human immunodeficiency virus (SHIV) acquisition time point in 43 cycling pigtail macaques infected by repeated vaginal virus exposures initiated randomly in the cycle.
Results:
SHIV infection was first detected in the follicular phase in 38 macaques (88%), and in the luteal phase in five macaques (12%), indicating a statistically significant timing difference. Assuming a 7-day eclipse phase, most infections occurred during or following a high-progesterone period associated with menstruation, vaginal epithelium thinning, and suppressed mucosal immunity.
Conclusions:
This raises questions whether other high-progesterone conditions (pregnancy, hormonal contraception) similarly affect HIV risk.
