Why do certain hormonal contraceptives increase the risk of HIV?
American Society for Microbiology
Washington, DC - September 1, 2015 - In recent years, evidence has been building that
injectable contraceptive depot medroxyprogesterone acetate (Depo-Provera or DMPA) is associated with
an increased risk of HIV infection. Now a study published in the September 1st issue of mBio, an
online open-access journal of the American Society for Microbiology, provides a biological
explanation for the phenomenon. The findings will help women make more informed choices
about birth control.
"Before this study, there were all these controversial reports, some showing that DMPA increases
the risk of HIV infection and others showing it doesn't, and there was no biologic explanation
for the differences between studies," said lead author Raina Fichorova, PhD, MD, director
of the Division of Genital Tract Biology at Brigham and Women's Hospital and associate
professor of obstetrics and gynecology and reproductive biology at Harvard Medical
School, Boston. "This new study offers an explanation for the inconsistent
studies, and it lies in the microbial communities of the reproductive tract."
The researchers analyzed cervical swabs and data from 823 women, between the ages of 18 and 35, who
were HIV negative and enrolled in family planning clinics in Uganda and Zimbabwe. Roughly 200
women in this cohort became HIV infected. Women were divided into three groups, those who
used DMPA, those who used estrogen-progesterone oral contraceptives, and those who used
no hormonal contraceptives. Within each of these groups, the investigators compared
results for women with a healthy vaginal environment (dominated by
Lactobacillus-morphotypes and free of bacterial vaginosis) to
women who had a disturbed vaginal microbioata or an infection from bacteria, fungi or parasites.
The team then looked to see if the women taking oral contraceptives or receiving DMPA were more at
risk for immunological changes that can increase a person's vulnerability to HIV infection than women
who weren't taking a hormonal contraceptive. They found that DMPA use was associated with an
increase in these immunological changes, and that the presence of certain vaginal infections
further increased this risk. In addition, women who had certain vaginal infections or
disturbed resident microbiota and took oral contraceptives were also at increased
risk for this unfavorable, immunological profile.
For example, women who had herpes and took DMPA, as well as women who had herpes or disturbed vaginal
microbiota and at the same time took levonorgestrel-containing oral contraceptives, were more likely
to have increased levels of proteins that attract HIV host cells. This kind of inflammatory
response is implicated in increasing the risk of HIV infection, transmission, or progression.
The research team also found that concurrent infections or disturbed vaginal microbiota may also
exacerbate the suppression of the immune system by DMPA, thus adding to a woman's vulnerability
to HIV. For example, DMPA appeared to suppress immune responses to Trichomonas vaginalis,
a wide-spread parasite that aids HIV infection.
"Women deserve to know more so that they can make informed choices about birth control. Both men
and women should be educated about our findings, as both partners are at risk and need to prevent
and treat infections," said Dr. Fichorova. "Studies of new contraceptive methods should evaluate
how they impact the microbial environment and how they act in concert with preexisting,
treatable microbial disturbances, to weaken the mucosal barrier against HIV and other
infections. Our hope is to prevent the unwanted side effects of available hormonal
contraceptives and improve and save millions of lives by developing new
affordable tools and approaches to restore and keep the healthy
vaginal microbial environment in women of reproductive age."
mBio ® is an open access online journal published by the American Society for Microbiology to
make microbiology research broadly accessible. The focus of the journal is on rapid publication
of cutting-edge research spanning the entire spectrum of microbiology and related fields. It
can be found online at http://mbio.asm.org.
The American Society for Microbiology is the largest single life science society, composed of over
39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences
as a vehicle for understanding life processes and to apply and communicate this knowledge for the
improvement of health and environmental and economic well-being worldwide.
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