A virus usually works/makes you ill by invading a cell in your body and making and replicating itself within the host cell. After being released from the host cell, the virus can go on to infect other cells in the body and also other people. The less a virus replicates, the less severe the infection and the lower the risk it will be spread onto other people.
The researchers used human nasal epithelial cells (hNECs) from male and female donors- which are the main cells which the flu virus targets - and exposed the nasal cells to 17β-estradiol (i.e estrogen) or select estrogen modulators (SERMs) (these include natural and synthetic compounds which act like estrogen in the body and are used for hormone therapy). The cells were then infected with a seasonal influenza virus (IAV), with each test group of cells being tested against each SERM individually.
Within the group of SERMs is a compound called BPA (bisphenol A), which you may have heard of before. It is derived from a group of compounds called xenoestrogens. Xenoestrogens are a type of xenohormone - they are compounds that imitate estrogen and they can be either synthetic or natural chemical compounds. Bisphenol A is a chemical that is used in a wide variety of consumer products and exhibits hormone-like properties. BPA is a chemical that is used in a wide variety of consumer products, such as resins used to line metal food and beverage containers, thermal paper store receipts, and dental composites. BPA has been in the news recently because of its hormonal abilities and the negative effects that can be a result of high concentrations of BPA in the body. (There will be more blog posts on this in the future.)
The results showed that estrogen, raloxifene, and bisphenol A decreased the IAV titers in hNECs from female but not male donors.
The concentration of a solution a determined by titration.
Which means that the estrogen and SERMs were able to reduce the replication of the flu virus in the nasal cells of the female donors but not in the male donors nasal cells.
Sabra Klein, Ph.D., of Johns Hopkins University and lead investigator of the study commented, "Other studies have shown that estrogens have antiviral properties against HIV, Ebola, and hepatitis viruses. What makes our study unique is two-fold. First, we conducted our study using primary cells directly isolated from patients, allowing us to directly identify the sex-specific effect of estrogens. Second, 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 of estrogens."