Certain Genital Bacteria Trigger Risk of HIV

Some types of genital bacteria were associated with a quadrupled risk of human immunodeficiency virus (HIV) infection, according to a new study.

“Our results advance our understanding of the cervicovaginal microbiome as an HIV risk factor and demonstrate the importance of considering the microbiome in the development of new treatments and preventive strategies to reduce HIV acquisition in young women living in sub-Saharan Africa,” researchers wrote in a paper published in the journal Immunity.

Twenty-four million people in sub-Saharan Africa have HIV and young women have a risk of getting HIV that’s eight times higher than the risk facing young men. Most of the new infections are the result of heterosexual sex.

Using recent techniques to sequence the vaginal biome, the group found that 60% of the women who participated in their study had communities of bacteria that were more susceptible to increased inflammation and had more HIV target cells. Specifically, they did not have the type of female genital tract (FGT) bacteria characterized predominately by Lactobacillus, as found in 90% of women in developed countries. Prevotella melaninogenica, Velillonella montpelierenis, Mycopasma, Prevotella bivia, and Sneathia sanguinegens were kinds of bacteria associated with the increased HIV risk.

“By identifying both bacterial communities and individual bacterial species associated with HIV risk, we can provide specific targets for the development of preventive strategies. In addition, treatments targeting genital bacteria could improve the effectiveness of existing preventive measures,” the lead author, Christina Gosman, PhD, a research fellow at Harvard Medical School, explained in a news release.

The cohort’s type of bacterial communities was not dependent upon demographic factors, condom use, sexually transmitted infections, type of sexual acts, or number of sexual partners.

After following this sample population of 236 young women, who were not infected at the start of the study, the researchers discovered roughly a year later that 31 had developed HIV. This was despite having received HIV prevention counseling.

The researchers from Massachuesetts General Hospital (MGH) and the Ragon Institute at MGH, Massachuesetts Institute of Technology and Harvard further tested their findings on mice. They injected two groups of mice intravaginally. One set was injected with a Lactobacillus crispatus bacteria that appears to be protective and the other with Prevotella bivia which was associated with increased numbers of HIV target cells. The latter group showed an increase in HIV target cells.

“Together, these results indicate that specific bacterial taxa may increase HIV infection risk by inducing elevated numbers of HIV target cells in the FGT,” the study reported.

These findings also have implications for pregnant women and their babies. “Some of the risk-associated pro-inflammatory bacteria that we found in our study may also contribute to poor reproductive outcomes, such as premature birth and other complications of pregnancy,” added senior author, Douglas Kwon, MD, PhD. Kwon, an assistant professor of medicine at Harvard Medical School and a principle investigator at the Ragon Institute.

The authors’ paper concluded, “Our results suggest that highly prevalent genital bacteria increase HIV risk by inducing mucosal HIV target cells. These findings might be leveraged to reduce HIV acquisition on women living in sub-Saharan Africa.”

The study, “Lactobacillus-Deficient Cervicovaginal Bacterial Communities Are Associated with Increased HIV Acquisition in Young South African Women,” was published in Immunity. The news release was provided by Massachusetts General Hospital.

Related Coverage:

Why Do Some People Get HIV After Exposure But Others Don’t?

Injectable PrEp Protects Women from HIV Transmission

Vaginal Ring Lowers HIV Risk Without Interfering with Sexual Intercourse