Friend or Foe: Innate Sensing of HIV in the Female Reproductive Tract

Female Genital Fibroblasts Diminish the In Vitro Efficacy of PrEP against HIV

The efficacy of HIV pre-exposure prophylaxis (PrEP) is high in men who have sex with men, but much more variable in women, in a manner largely attributed to low adherence. This reduced efficacy, however, could also reflect biological factors. Transmission to women is typically via the female reproductive tract (FRT), and vaginal dysbiosis, genital inflammation, and other factors specific to the FRT mucosa can all increase transmission risk. We have demonstrated that mucosal fibroblasts from the lower and upper FRT can markedly enhance HIV infection of CD4+ T cells. Given the current testing of tenofovir disoproxil fumarate, cabotegravir, and dapivirine regimens as candidate PrEP agents for women, we set out to determine using in vitro assays whether endometrial stromal fibroblasts (eSF) isolated from the FRT can affect the anti-HIV activity of these PrEP drugs. We found that PrEP drugs exhibit significantly reduced antiviral efficacy in the presence of eSFs, not because of decreased PrEP drug availability, but rather of eSF-mediated enhancement of HIV infection. These findings suggest that drug combinations that target both the virus and infection-promoting factors in the FRT-such as mucosal fibroblasts-may be more effective than PrEP alone at preventing sexual transmission of HIV to women.

The estrogen-macrophage interplay in the homeostasis of the female reproductive tract

BACKGROUND

Estrogens are known to orchestrate reproductive events and to regulate the immune system during infections and following tissue damage. Recent findings suggest that, in the absence of any danger signal, estrogens trigger the physiological expansion and functional specialization of macrophages, which are immune cells that populate the female reproductive tract (FRT) and are increasingly being recognized to participate in tissue homeostasis beyond their immune activity against infections. Although estrogens are the only female gonadal hormones that directly target macrophages, a comprehensive view of this endocrine-immune communication and its involvement in the FRT is still missing.

OBJECTIVE AND RATIONALE

Recent accomplishments encourage a revision of the literature on the ability of macrophages to respond to estrogens and induce tissue-specific functions required for reproductive events, with the aim to envision macrophages as key players in FRT homeostasis and mediators of the regenerative and trophic actions of estrogens.

SEARCH METHODS

We conducted a systematic search using PubMed and Ovid for human, animal (rodents) and cellular studies published until 2018 on estrogen action in macrophages and the activity of these cells in the FRT.

OUTCOMES

Our search identified the remarkable ability of macrophages to activate biochemical processes in response to estrogens in cell culture experiments. The distribution at specific locations, interaction with selected cells and acquisition of distinct phenotypes of macrophages in the FRT, as well as the cyclic renewal of these properties at each ovarian cycle, demonstrate the involvement of these cells in the homeostasis of reproductive events. Moreover, current evidence suggests an association between estrogen-macrophage signaling and the generation of a tolerant and regenerative environment in the FRT, although a causative link is still missing.

WIDER IMPLICATIONS

Dysregulation of the functions and estrogen responsiveness of FRT macrophages may be involved in infertility and estrogen- and macrophage-dependent gynecological diseases, such as ovarian cancer and endometriosis. Thus, more research is needed on the physiology and pharmacological control of this endocrine-immune interplay.