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Vaginal Bacteria Kills HIV Treatment

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Certain species of vaginal bacteria can inhibit the efficacy of the topical microbicide tenofovir, which is used to prevent HIV, by breaking it down before it is absorbed, reports an international team of investigators in Science.

Image result for vagina

M.J. Friedrich

Women using the vaginal antiretroviral gel tenofovir to prevent acquisition of HIV have experienced inconsistent results. Variability in adherence has been shown to be a factor in the diverse trial outcomes, but little is known about the biological factors that may contribute to variable results.

In this study, the researchers compared the vaginal bacterial communities of 688 South African women who were HIV-negative when enrolled into the randomized controlled trial (CAPRISA 004) evaluating the efficacy of 1% tenofovir intravaginal gel in preventing HIV. The researchers identified 2 major types of vaginal bacterial communities—one populated mainly by the genus Lactobacillus and the other dominated by a diverse bacterial mix of non-Lactobacillus microbiota, namely Gardnerella vaginalis. Gel adherence was similar in both groups.

The researchers found that tenofovir significantly reduced HIV incidence only in women with Lactobacillus-dominant vaginal microbiota (61% vs 18% in women with non-Lactobacillus dominance). In vitro studies showed that G vaginalis and other anaerobes metabolized tenofovir before the body could absorb it, while 2 Lactobacillusspecies did not.

The findings indicate that differences in bacterial metabolism contribute to tenofovir’s variable effectiveness in HIV prevention and suggest that screening vaginal microbiota could be useful in identifying women most likely to benefit from such topical HIV microbicides.

read more at JAMA