Female hormones play a vital role in defense against sexually transmitted diseases

[img_inline align=”right” src=”http://padnws01.mcmaster.ca/images/kaushic_charu.jpg” caption=”Charu Kaushic”]
Two McMaster University studies, to be published in the Journal of Virology,
show that sex hormones have a profound effect on susceptibility of female mice
to the herpes simplex virus, type 2 (HSV-2 ), one of the most common sexually
transmitted diseases.
Charu Kaushic, assistant professor and supervisor of the studies, says the
implication of this work is quite significant. The research clearly shows,
and reaffirms previous research, that in female mice, sex hormones have a profound
effect on susceptibility to sexually transmitted infections as well as on the
body's defense mechanisms against them.
One of the many implications of these findings she says, is that if future
studies can figure out that women too, like mice, are protected in primary exposure
by estradiol, contraceptive creams could be formulated that would prevent herpes
virus infection before they could start. Additionally she says, if they were
designing a vaccine trial against HSV-2 and if the mice results hold true for
women, they could suggest vaccination protocols under combination hormone therapy
to get the best benefit from the vaccine.
Work in this area is important because one in every four sexually active adults
is seropositive for HSV-2 and women are much more susceptible than men.
The results directly indicate that the hormonal conditions that provide
protection against primary exposure to sexually transmitted viral infections
may be very different than those that may be useful in vaccination strategies,
said Kaushic.
There is of course the flip side to this as well. Our studies in mice
and in fact a number of clinical studies as well show that women who use Depo-provera,
a progesterone based injectable contraceptive, have particularly high susceptibility
to sexually transmitted infections, including HIV-1 and HSV-2. We do not understand
why, and our hope is that by doing these kind of mouse studies, we can understand
the mechanisms.
In the first study, female mice received either the hormone estradiol or progesterone,
a combination of both, or nothing at all prior to exposing them to the herpes
virus. Both estradiol and progesterone are natural hormones found in the body.
The estradiol-treated mice were protected 100 percent, whereas the progesterone-treated
mice and mice that didn't receive any hormones, showed extensive infection,
and additionally, the progesterone-treated mice had increased inflammation and
were more susceptible to the virus. The mice treated with a combination of the
two hormones, estradiol and progesterone, were protected, but only if the virus
doses were weakened.
In the second study, just like in the first study, mice were treated with hormones
but, before being exposed to the real herpes virus, they received a vaccine
Surprisingly, unlike in the first study, the progesterone-treated mice and
the mice that received no hormones were the most protected. About half the mice
in the combination hormone group were also protected and the estradiol-treated
group was not at all protected. Similar studies confirmed that a combination
of the hormones estradiol with progesterone provided the best protection in
vaccinated mice.
These studies add to the growing evidence that we need to promote more
gender-specific medical approaches in future, she said. We have
to increase awareness in both the medical community as well as the public regarding
sexually transmitted diseases and women.
Extending these findings into clinical studies is the next step. McMaster researchers
are currently discussing the design of a study with infectious disease clinicians
in Hamilton, which may begin in as early as the next few months. Additionally
they will be looking at issues of co-infection with both HIV-1 and HSV-2 which
is a big problem clinically.
The two studies were posted online on the Journal of Virology website this
week and will be published in the Journal in the March issue.