Study: Link Found Between Genital Bacteria and HIV Acquisition Risk

A recent study found that vaginal bacterial microbiomes not dominated by Lactobacillus crispatus are associated with increased the risk for HIV acquisition by 4-fold.

The study was conducted in South Africa, where there is up to an 8-fold higher prevalence of HIV among women than men, and included 236 HIV-uninfected women who were 18-32 years old, and a part of the Females Rising through Education, Support and Health (FRESH) study. The median follow-up time was 336 days. The researchers performed a bacterial 16S ribosomal gene and viral shotgun sequencing of cervicovaginal microbiota, and assessed the role of bacteria in the acquisition of HIV.
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During the study, 31 women acquired HIV and 205 remained HIV-uninfected.

Analysis of the vaginal bacteria revealed that 23 participants (10%) had low diversity and Lactobacillus crispatus dominated communities, 74 participants (32%) had low diversity and Lactobacillus iners dominated communities, and 58% of participants had high-diversity with low abundance of L. crispatus.

Among the women who had a low abundance of L. crispatus, 68 participants had vaginal microbiota dominated by Gardnerella. The remaining 70 participants had another dominate genus that was not Gardnerella or Lactobacillus, and the most abundant taxa present were Prevotella, Gardnerella, Shuttleworthia, Sneathia, and Megospharea. Researchers did not identify any distinct viral community structures in participants.

Their findings showed that women with high-diversity and low Lactobacillus abundance had a greater than 4-fold increased risk for HIV acquisition compared to women with L. crispatus dominate bacteria communities. Researchers found that none of the women with L. crispatus dominated communities acquired HIV. In addition, researchers noticed that there was no difference in genital bacteria communities for women who acquired HIV and women HIV-uninfected who shared similar cervicovaginal microbiota, which indicated that HIV risks were the same in all women who had high-diversity, and low abundance of L. crispatus.

Likewise, researchers found that women with high diversity and abundant Prevotella, Gardnerella, Shuttleworthia, Sneathia, and Megasphaera bacterial communities had a 17-fold increase in the number of HIV target cells than women with L. crispatus-dominate communities. Their findings demonstrated that L. crispatus was associated with reduced inflammation and HIV acquisition, while diverse bacteria microbiomes with abundant Prevotella, Gardnerella, Shuttleworthia, Sneathia, and Megasphaera increased inflammation and the risk for HIV acquisition.

“Our findings underscore the importance of developing more effective regimens that achieve a sustained alteration of the genital microbiome since this could potentially reduce HIV acquisition. In this context, strategies targeting specific bacterial taxa associated with reduced or increased HIV acquisition might be useful, although the host mechanisms that maintain specific microbial communities in the genital tract need to be better understood,” the researchers concluded.

—Melissa Weiss

Reference:

Gosmann C, Anahtar MN, Handley SA, et al. Lactobacillus-deficient cervicovaginal bacterial communities are associated with increased HIV acquisition in young South African women [published online January 10, 2017]. Immunity. doi:10.1016/j.immuni.2016.12.013.