Vaginal bacteria can consume HIV prevention drugs and put women at risk

Through Christa Lesté-Lasserre

KATERYNA KON / SCIENTIFIC PHOTO LIBRARY

Women with a certain blend of bacteria in their vagina may have a much higher risk of contracting HIV because the bacteria consume medications that prevent infection with the virus.

Pre-exposure oral prophylactic drugs (PrEP) are 90% effective in preventing HIV infections in men who have sex with men. But the effectiveness of PrEP medications drops to 50% or less in women, both orally and vaginally, and researchers don’t have a full explanation as to why this is the case.

Nichole Klatt of the University of Minnesota and his colleagues suspect that part of the reason could be the vaginal microbiome. In many cases, the vaginal microbiome is dominated by Lactobacillus bacteria, which help maintain a protective mucous layer that reduces the risk of inflammation and infection. Yup Lactobacillus numbers are dwindling, a diverse bacterial community that includes species such as Gardnerella vaginalis, takes over – and women may be more vulnerable to sexually transmitted infections.

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Klatt’s team has conducted a series of studies to see what happens when three HIV prevention drugs are grown with microbes taken from different vaginal microbiomes, some Lactoballicus– dominated and a little more diverse. Two drugs – tenofovir and dapivirine – quickly began to disappear from various cultures. After 24 hours, the Lactoballicusthe dominated cultures had double the level of HIV prevention drugs seen in various cultures, Klatt says.

Further analysis suggested the reason. Anaerobic bacteria such as G. vaginalis they seem to metabolize – essentially, eat – drugs. In the real world, they can do this before the drugs reach the vaginal cells they are supposed to protect. This would help explain why the drugs are less effective in some women, Klatt says.

The third drug had a different fate. Tenofovir alafenamide – which is primarily intended for the treatment of hepatitis B and is only approved as an HIV treatment for certain risk groups – does not appear to be affected by the various cultures, keeping the same volumes in both types of samples, he said.

The study reveals significant gaps in women’s health research that directly affect about 1 million women who contract HIV each year, says Klatt.

Journal reference: PLoS pathogens, DOI: 10.1371 / journal.ppat.1009024

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