Vaginal application of anti-retroviral drugs, such as tenofovir, before sex has had mixed results in preventing HIV infection in women.
To learn why, Nichole Klatt at the University of Washington in Seattle, Adam Burgener at the Public Health Agency of Canada in Winnipeg, and their colleagues compared the vaginal bacterial communities of 688 South African women. The women had either mainly Lactobacillus species or a diverse population dominated by Gardnerella vaginalis, which is associated with bacterial vaginosis. The team then tracked whether the women contracted HIV over a 2.5-year period when they were given either tenofovir gel or a placebo. Tenofovir reduced the likelihood that women with mainly Lactobacilllus communities would get HIV, but the drug was less likely to protect women with a higher proportion of G. vaginalis and other similar microbes, which metabolize tenofovir before the body’s cells can absorb it.
Screening women to identify the composition of their vaginal bacterial community before anti-retroviral treatment could help to improve HIV prevention, the authors suggest.