A new study that highlights the antiviral effects of the female hormone estrogen, could lead to novel flu therapies. By isolating estrogen from female patients, researchers found that it can protect against the influenza A virus. The study was conducted by researchers from John Hopkins University, and is published in American Journal of Physiology—Lung Cellular and Molecular Physiology.

The flu virus grows by replicating inside the host cell, where it can then spread throughout the body, and also infect other people. Halting this spread can limit the degree of sickness a patient experiences. To test the effect of estrogen on the ability of the flu virus to replicate, researchers gathered nasal cells from male and female donors that the virus primarily infects.

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Researchers exposed the cells to the virus, estrogen,  environmental estrogen bisphenol A, and selective estrogen receptor modulators (SERM). They found that estrogen, raloxifene (a SERM compound), and bisphenol A reduced virus replication in the nasal cells from women but not men. They also found that estrogens exerted their antiviral effects through estrogen receptor beta.

Although previous studies have shown estrogens to have antiviral properties against HIV, Ebola and hepatitis viruses, this study is unique in that it used primary cells directly isolated from patients. “This is the first study to identify the estrogen receptor responsible for the antiviral effects of estrogens, bringing us closer to understanding the mechanisms mediating this conserved antiviral effect,” said Sabra Klein, PhD, of John Hopkins University, who was the lead investigator of the study.

As a result of their findings, the authors hypothesized that premenopausal women on certain kinds of birth control, or postmenopausal women on hormone replacement, may be better protected during flu epidemics. “We see clinical potential in the finding that therapeutic estrogens that are used for treating infertility and menopause may also protect against the flu,” said Dr. Klein.

For more information visit the ajplung.physiology.org.