Some vaginal bacteria may render HIV drug ineffective

Certain types of vaginal bacteria can may significantly reduce the effect of a medication used to prevent HIV, which affects millions of women worldwide, a new study has found.
High HIV acquisition rates among women are a major global health concern. While the drug called tenofovir routinely prevents the virus in men at great risk, efficacy of this drug in females has been variable.
To explore a role for the microbiome in this variability, Nichole Klatt from University of Washington in the US and colleagues used samples collected from participants in a clinical trial evaluating the effectiveness of tenofovir intravaginal gel in preventing HIV in South African women.

During the study period, some of the women went on to contract the virus.
Among the samples they analysed, researchers identified two major vaginal bacterial compositions in women - one dominated by the bacteria Lactobacillus, and the other by Gardnerella vaginalis.
They found that individuals where Lactobacillus predominated had around 3-fold greater protection against HIV acquisition, compared to those with non-Lactobacillus vaginal compositions.
Women with predominant Gardnerella vaginalis had high HIV acquisition, because the bacteria could rapidly metabolise and breakdown the active form of the drug.
The findings may have implications for which patients are administered the drug in the clinic, and for the design of public health programs and clinical trials.