When it comes to HIV, researchers are continually working to grasp a better understanding of what it is, how it spreads, who it spreads to, and how to prevent its transmission. Recently, new findings
presented in Durban, South Africa, have directly linked specific vaginal microbiomes to an increased risk of HIV infection. These findings may offer an explanation of why anti-HIV drugs given to prevent infection tend to work better in men rather than women.
According to the presentation, these findings are based on follow-up studies of women who had previously participated in a pre-exposure prophylaxis (PrEP) study
, a way for people who are not infected but highly susceptible to HIV to substantially lower their risk of infection. This particular study was conducted by the Centre for the AIDS Programme of Research in South Africa (CAPRISA) and explored the potential beneficial use of a vaginal gel that contained tenofovir, an anti-HIV drug. Although initial results in 2010 seemed promising (results showed that the gel actually lowered women’s potential risk by 44%), the gel ultimately failed in a subsequent trial.
Last year, CAPRISA and their collaborators at the University of Cape Town reported that women with increased genital tract inflammation were more likely to contract HIV as CD4 white blood cells, commonly targeted by HIV, are brought to the mucosal surface when inflammation occurs. Similarly, in another study carried out in South Africa’s KwaZulu-Natal province, Douglas Kwon, PhD, an immunologist at Massachusetts General Hospital in Boston, and colleagues found that a decrease in Lactobacillus
in the vagina is linked to vaginal inflammation and creates an environment unreceptive to helpful pathogens.
In a new follow-up study, researchers used samples from the women in the CAPRISA tenofovir study in an effort to identify the various bacterial species found on the vaginal swabs collected. One lab in particular, run by Ian Lipkin, MD, at Columbia University, made an interesting discovery.
According to the presentation, after Dr. Lipkin removed approximately 25,000 bacterial ribosomal RNA, he was able to identify 1,368 bacterial species; one of which played a role in increasing inflammation. Dr. Lipkin found that women who had more than 1% of Prevotella bivia
in their vaginal microbiome makeup experienced greater inflammation as well as increased levels of lipopolysaccharide (LPS), and therefore, had the highest susceptibility of acquiring HIV.
According to the study
, published in Science
, “Women who had greater than 1% P. bivia
were 13 times more likely to become infected by HIV.”
Anthony Fauci, MD, head of the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said that these new findings offer possibilities for researchers to either manipulate the vaginal microbiome itself or introduce “helpful” bacteria that could work to head off infection. However, Dr. Kwon cautioned that this kind of manipulation is “often extremely difficult.”