DURBAN, South Africa — The microbiota of the vagina play a role in the transmission of HIV, according to new research.
The presence of the relatively uncommon Prevotella bivia bacteria in the vagina increases the risk for HIV infection, and when Gardnerella vaginalis is predominant in vaginal flora, the ability of tenofovir to prevent HIV infection is rapidly reduced.
"Approximately 70% of new and existing HIV infections occur in eastern and southern Africa, and young women in particular have very high rates of HIV infection," said Salim Abdool Karim, director of the Centre for the AIDS Programme of Research in South Africa (CAPRISA).
"We wanted to understand what it is about these young women that leads them to acquire HIV so rapidly," Dr Karim explained during a news conference here at the International AIDS Conference 2016.
In their analysis of the vaginal bacteria of 120 women, the CAPRISA investigators found that the risk for HIV infection was 13 times higher in those with high levels of P bivia than in those with lower or no levels.
P bivia is not sexually transmitted and it is the predominant vaginal bacteria in only about 15% to 20% of women, Dr Karim pointed out. But it contributes to a "sizeable minority" of HIV infections in young women and is also associated with genital inflammation.
The CAPRISA investigators also analyzed 3334 genital bacterial proteins from 688 women. They found that three of five women who had Lactobacillus-dominant vaginal bacteria benefited when tenofovir gel was used as pre-exposure prophylaxis.
However, they also found that the presence of G vaginalis kept tenofovir inside cells, and after 24 hours, levels of tenofovir dropped to zero in these women.
"This might be one of the reasons women have to be very strict about maintaining adherence to tenofovir, whether it's the gel or the tablets," Dr Karim said.
Levels of the protective and tenofovir-neutral Lactobacillus can be restored to normal in at least half of women with a single application of Lactobacillus vaginal suppositories, according to tests conducted in the United States.
"Implementing a combination of evidence-based targeted interventions to break the cycle of HIV transmission while effectively treating bacterial vaginosis could enhance HIV prevention in women in the highest HIV-burden region of the world," Dr Karim said in a statement.
To track transmission patterns in rural and in urban communities in South Africa, the CAPRISA investigators also analyzed the HIV genome from 1589 HIV-positive people.
They found that the high rate of HIV infection seen in adolescent girls and young women could be attributed to older men.
"I'm talking here about teenagers and young women in their twenties," said Dr Karim. "They are acquiring HIV infection mostly from men in their 30s. These men have often just become infected themselves, so they don't know they have HIV, they haven't been tested, they are not on treatment, and they have high viral loads."
"So they are exposing young women to high levels of the virus, and if these young women just happen to have Prevotella bivia," they are very vulnerable to infection, he explained.
"It has never been more critical to address this vital issue," said Chris Beyrer, MD, who is president of the International AIDS Society.
"Women account for the majority of adults living with HIV in sub-Saharan Africa, and new infections among young women are double those of young men in the region," he reported.
In fact, in southern and eastern Africa, 380,000 girls and women 16 to 24 years of age are infected with HIV each year, which is several times higher than the infection rate in their male counterparts.
International AIDS Conference 2016. Presented July 19, 2016.
Medscape Medical News © 2016 WebMD, LLC
Send comments and news tips to firstname.lastname@example.org.
Cite this: Bacterial Vaginosis Raises HIV Risk, Lowers Tenofovir Level - Medscape - Jul 19, 2016.