Estradiol May Protect Against Sexually Transmitted Infections

17β-estradiol, more commonly known as estradiol, is an estrogen and the primary female steroid hormone. Estradiol is produced by the follicles within the female ovaries and plays important roles in female menstrual and reproductive cycles. Recent evidence has come to light which has established a protective role of estradiol, more specifically estradiol 2 (E2), in females for the prevention of sexually transmitted infections (STIs). 

The study was carried out under the supervision of Charu Kaushic, professor of Pathology and Molecular Medicine, a member of the Michael G. DeGroote Institute for Infectious Disease Research and McMaster Immunology Research Centre and the lead researcher of this study. The results of the study were subsequently published in PLOS Pathogens.

During the course of the study, experiments were carried out on female mice with Herpes Simplex type 2 (HSV-2) infection. The investigators imbedded estradiol-containing pellets into the female mice. The ovaries of these mice had been removed. This was followed by injection of two phases of HSV-2 vaccine after which the strains of herpes Simplex type 2 (HSV-S) were introduced in these mice. 

Herpes simplex is one of the diseases that are transmitted via sexual contact. The disease affects millions of women around the globe annually. The study has identified the precise mechanism by which estradiol plays a protective role against STIs in females. 

Estradiol: The Protector against STIs

The researchers noted that most of the mice that were injected with the vaccine and the virus survived. The symptoms of herpes simplex were less in these mice in contrast to the mice that were not given the vaccine. 

The researchers looked further to explore the underlying molecular mechanisms. They discovered that estradiol stimulates the dendritic cells present in the vagina to enhance the CD4+ T cell immunity against the invading virus. These responses were mediated via an interleukin 1 (IL-1) dependent pathway. 

The investigators observed an unusual anti-viral activity of the T cells in the cell cultures obtained from the vaginal tract, that was limited to the cells lining the vagina tract and none of the mucosal surfaces present elsewhere in the body showed this activity. 

According to Kaushic, the lead researcher involved in the study, this study is the first of its kind to discover the exact process by which estradiol fortifies the immune system of the body and wards off the sexually transmitted infections. 

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The Future Prospects

This study has effectively established that female sex hormone estradiol can have a major impact on the susceptibility and immune responses towards the sexually transmitted infections. 

The study is expected to have far-reaching implications in terms of development of better preventive strategies for sexually transmitted infections in the form of oral contraceptives. These contraceptives can be administered to women who are at exceptionally high risk of contracting sexually transmitted infections like HIV and HSV, especially in the Sub-Saharan Africa. 

It is also likely that these findings will be used to find out which form of immunity plays a better role in protecting women against the sexually transmitted infections so that better vaccines can be developed to fight STIs.