Vaginal Microbiome Affects HIV Prevention

Lactobacillus organisms from vaginal smear (Janice Carr, CDC/Dr. Mike Miller, Centers for Disease Control and Prevention's Public Health Image Library (PHIL))

Lactobacillus organisms from vaginal smear
(Janice Carr, CDC/Dr. Mike Miller, Centers for Disease Control and Prevention’s Public Health Image Library (PHIL))

Tenofovir is used as a pre-exposure drug for HIV prevention in high risk individuals. While pre-exposure drugs have proven to be highly effective for men, studies on their efficacy on women have been inconsistent. In their study, Klatt el al. discovered a link between tenofovir efficacy and the type of vaginal microbiome in African women.

The vaginal microbiome consists of a wide variety of microbial species that maintain vaginal mucosal health. Vaginal microbiomes usually fall into two categories: 59.2% of microbiomes are Lactobacillus-dominant while 40.8% are non-Lactobacillus-dominant, where a high abundance of Gardnerella vaginalis and other anaerobic bacteria can be found. A dysbiosis of this microbiome is commonly referred to as bacterial vaginosis and occurs when a microbiome shifts from being Lactobacillus-dominant to non-Lactobacillus-dominant. While bacterial vaginosis is usually asymptomatic, it is associated with higher HIV infection risk.

In Klatt el al.’s study, 688 women were either assigned a tenofovir topical gel or a placebo gel to use. In the Lactobacillus-dominant group, consistent tenofovir use reduced the risk of HIV infection by 61% compared to participants who used a placebo. In the non-Lactobacillus-dominant group, consistent tenofovir use still reduced the risk of HIV infection, but only by 18%.

Upon closer inspection, the researchers noticed that the Lactobacillus-dominant group had much higher mucosal tenofovir levels compared to the non-Lactobacillus-dominant group. After testing the interactions between G. vaginalis and tenofovir, researches discovered that G. vaginalis metabolized tenofovir at a rapid rate. This explained the lower tenofovir levels in non-Lactobacillus-dominant participants, which led to a higher risk of HIV infection.


Journal Article: Klatt NR et al., 2017. Vaginal bacteria modify HIV tenofovir microbicide efficacy in African women. Science

Article by Maxwell Chan


International Union of Immunological SocietiesUniversity of South AfricaInstitute of Infectious Disease and Molecular MedicineScience Education PrizesElizabeth Glazer Pediatric Aids Foundation