International AIDS Society

Vaginal Bacteria Make-up Affects Risk of Vertical HIV Transmission

Author: Mark Mascolini

07 July 2012

Make-up of vaginal microbiota—the microscopic organisms that populate the vagina—had a measurable impact on risk of vertical (or mother-to-child) transmission of HIV in a retrospective study of women in Burkina Faso.

Differences in vaginal microbial communities affect sexual transmission of HIV. But the impact of vaginal microbiota on perinatal HIV transmission had not been studied. Researchers addressed that question by sequencing bacterial genes from 10 women who transmitted HIV during a mother-to-child transmission (MTCT) trial of zidovudine and the microbicide benzalkonium chloride and 54 women who did not transmit HIV. The investigators analyzed a median of 350 sequences per sample.

Several lactobacilli species dominated vaginal microbiota of study participants. Lactobacilli—Gram-positive anaerobic bacteria—are among the most important “friendly” bacteria found in the digestive tract. A subset of study participants had diverse anaerobic species in the vagina.

Among abundant bacterial species, Gardnerella vaginalis raised the odds of antepartum HIV transmission 70% (odds ratio 1.7, P = 0.004). Gardnerella vaginalis can cause bacterial vaginosis by disrupting normal vaginal microflora.

Neither zidovudine nor benzalkonium chloride affected shifts in microbial distribution when compared with placebo.

“Alterations in vaginal microbial communities are associated with an increased risk for perinatal MTCT,” the researchers conclude, “consistent with results with horizontal transmission of HIV. Therefore, determining the mucosal features associated with alterations in vaginal microbial communities may guide efforts to modulate the risk for HIV MTCT.”

Source: Daniel N. Frank, Olivier Manigart, Valériane Leroy, Nicolas Meda, Diane Valéa, Weiming Zhang, François Dabis, Norman R. Pace, Philippe Van de Perre, Edward N. Janoff. Altered vaginal microbiota are associated with perinatal mother-to-child transmission of HIV in African women from Burkina Faso. JAIDS. 2012; 60: 299-306.

For the study abstract

(Downloading the complete article requires a subscription to JAIDS or an online payment; the abstract is free.)