Women with Lactobacillus-deficient vaginal microbiomes at fourfold increased risk for HIV

Young women whose vaginal bacteria are dominated by pro-inflammatory species were at a fourfold increased risk for HIV infection compared with women with “healthy” vaginal bacteria, a study in South Africa revealed.

“A small number of prospective studies indicate that women with cervicovaginal bacteria deficient in lactobacilli, a bacterial genus considered beneficial for vaginal health, are at higher risk of acquiring HIV,” Christina Gosmann, PhD, of the Ragon Institute of Massachusetts General Hospital, MIT and Harvard, and colleagues wrote. “However, the depth of these studies has been limited by the use of Gram-stained vaginal smears to assess the genital bacterial composition and by investigation of sex-worker and clinical cohorts not representative of the average healthy female population.”

Gosmann and colleagues performed genetic sequencing on the vaginal microbiota of 236 South African women aged 18 to 23 years without HIV and monitored participants with “high frequency” HIV testing.

Thirty-one women became infected with HIV during the study period. Median follow-up was 336 days, and overall HIV incidence was 8.43 per 100 person-years.

Gosmann and colleagues reported that 10% of women had low diversity vaginal bacteria communities that were dominated by Lactobacillus crispatus, a significant difference from white women in developed countries, of whom 90% had Lactobacillus-dominated bacterial communities. Those with high-diversity, low Lactobacillus communities (identified in the study as “CT4” and “CT3”) were over four times more likely to acquire HIV than those with L. crispatus dominance (CT4: HR = 4.03; 95% CI, 1.14-14.27; CT3: HR = 4.22; 95% CI, 1.06-16.88), the researchers wrote.

“We think of a healthy microbiome as being Lactobacillus-dominant — that’s what we’re taught in medical school — but those studies are mostly based on white women in developed countries,” Douglas Kwon, MD, PhD, director of clinical operations at the Ragon Institute, said in a press release accompanying the study. “Seventy percent of our volunteers had diverse bacterial communities with low Lactobacillus abundance. Here we show that not only are those more diverse communities associated with higher levels of genital inflammation but also with significantly increased HIV acquisition.”

Researchers also wrote that women with higher-risk vaginal microbiota had greater genital CD4 counts.

“We’re very excited about these findings. We’ve used modern medical molecular approaches to characterize the vaginal microbiome and link specific bacteria to HIV acquisition risk in young women living in Sub-Saharan Africa, where HIV is most profound,” Gosmann said in the release. “There is a direct translational application that comes from this work. By identifying bacterial species and communities associated with HIV risk, we provide specific targets that may be leveraged to develop new preventive strategies and to improve the effectiveness of existing preventive measures.” – by Andy Polhamus

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