Females are not the weaker sex when it comes to battling the flu virus, says a new study. Published in the American Journal of Physiology - Lung Cellular and Molecular Physiology,
the study reports that estrogen protects against the flu virus in women, but not in men.
Estrogen is considered the ultimate female hormone, as it is the natural chemical responsible for the development and regulation of the female reproductive system. In addition to these uniquely “female” roles, the hormone has been found to decrease the replication of some viruses, including HIV, Ebola, and hepatitis. Researchers at the Johns Hopkins Bloomberg School of Public Health wondered whether this hormone could also dampen the effects the common flu virus.
In a simple and elegant experiment, a team of scientists, led by Sabra L. Klein, Ph.D., tested viral replication of the influenza A virus from nasal passage cells collected from male and female volunteers. The cells were exposed to different types of estrogens, and then infected with the seasonal influenza A virus.
They found that all types of estrogens, including selective estrogen receptor modulators and bisphenol A, decreased the virus' replication by nearly a 1,000-fold compared to cells not exposed to the hormones. Additionally, the replication decrease was more significant in women more than in men.
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. Sabra L. Klein, study lead.
Estrogen, though known as a female hormone, is also produced by males. However, the levels of this hormone in men are low and consequently, their cells don’t have as many estrogen receptors. And if the antiviral effects happen through the estrogen receptors, then it may explain why men aren’t as protected as women.
Can estrogen have a population-wide effect in protecting women from the flu? Researchers think this scenario is unlikely because normal estrogen levels fluctuate in women every month.
But these results could be very good news for people who are currently taking the estrogen, either for contraceptive purposes, hormone replacement therapies, or as part of infertility treatments. "If women are taking estrogen-like hormones for other reasons, an added benefit might be less susceptibility to influenza during the flu season," Klein says.
So, in one fell swoop, this study vindicates women for being the stronger sex, and confirms men’s enduring claims that the flu is worse for them. Perhaps these conclusions are already too obvious to some of us, but hey – it’s always nice when science backs up what we suspected all along!
Additional source: The American Physiological Society press release