New research has found some women's bodies create natural armor against sexually transmitted infections, a mechanism that could someday be harnessed to create a kind of biological condom.
A study published Tuesday in mBio, an online journal of the American Society for Microbiology, found vaginal mucus that contains a specific type of naturally occurring bacteria can work as a natural barrier to the HIV virus.
Cervicovaginal mucus (CVM), which coats the female reproductive tract, acts as the first line of defense against potential infections, preventing pathogens from penetrating underlying cells. Research has shown CVM can immobilize HIV virions and reduce the viral load that arrives at target cells. The average number of mobile HIV particles in CVM samples that trap the virus was only 1.3% ± 0.6% compared to 45% ± 8% in CVM samples that did not.
The biochemical makeup of CVM is shaped by vaginal microbes in ways researchers don't yet fully understand, the study's lead author Sam Lai said.
Researchers believe the protective bacteria could be "among the most effective means of reducing vaginal HIV transmission"
"People know for a fact the mucus properties can vary between different women but also in the same women over time, so we wanted to specifically understand what might contribute to the differences in the various properties," he told Motherboard.
For the study, researchers measured the properties of CVM samples from 31 women of reproductive age, and then used high-resolution, time-lapse microscopy to observe whether HIV pseudovirus particles were trapped within the samples. They found CVM that trapped HIV had higher levels of D-lactic acid, which can be produced by a variety of bacteria.
"One of the things we surprisingly found from this study is that it appears as though women who possess a particular strain of bacteria appear to possess a mucous much more able to trap and immobilize HIV viruses than women possessing other bacteria," Lai said.
Ultimately they found women who harbor L. crispatus bacteria appear to be more protected against HIV whereas women who harbor L. iners bacteria have a substantially higher risk of acquiring sexually transmitted infections (STIs).
Lai said L. crispatus is also likely to lower their risk of contracting other sexually transmitted infections that involve enveloped viruses—viruses wrapped in a protective outer coat—including herpes.
He added that current health screenings do not test for these specific bacteria, and that healthcare workers should be advised that patients who harbor L. iners are at higher risk for STIs.
Although it is difficult to compare the effectiveness of the microbial defense to traditional condom use, the researchers believe the protective bacteria could be "among the most effective means of reducing vaginal HIV transmission." Building upon this study, other researchers could work to find a way to induce this micro barrier in women through antibiotics or other means.
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