According to a new paper published in the scientific journal mBio, an increase in some types of bacteria living under the foreskin can increase a manâ€™s risk of HIV infection by up to 63 percent. The study, â€œPenile anaerobic dysbiosis as a risk factor for HIV infection,â€ was an international collaboration that included researchers from Northern Arizona University, the Milken Institute SPH, the Translational Genomics Research Institute (Flagstaff, AZ), School of Medicine and Bloomberg School of Public Health, Johns Hopkins University (Baltimore, MD), Rakai Health Sciences Program (Entebbe, Uganda) and the Department of Medicine, University of Toronto (Toronto, Canada).
NAU Regentsâ€™ Professor Bruce Hungate, a co-author of the paper, is Director of the Center for Ecosystem Science and Society.
â€œThis study is important,â€ explained Hungate, â€œbecause it shows, for the first time, that bacteria in the penile microbiome may be a risk factor for HIV infection in menâ€”and that this risk factor may be sexually transmissible.â€
Earlier studies linked the human microbiomeâ€”the collection of microbes living in and on the human bodyâ€”to a variety of health conditions, but little was known about the role of the penile microbiome as it relates to HIV. By examining the collection of bacteria living under the foreskin of men who either went on to become infected by HIV or remained HIV-negative, the researchers discovered a link between the quantity of anaerobes, bacteria that thrive in low-oxygen environments, and an increased risk of becoming infected by HIV.
The researchers conducted a two-year clinical study in Rakai, Uganda, during which 46 men became infected with HIV, by measuring the abundance of penile bacteria living under the foreskin. They found that a ten-fold increase in four anaerobic bacteriaâ€”Prevotella, Dialister, Finegoldia and Peptoniphilusâ€”correlated to a 54 to 63 percent increase in HIV risk.
The researchers hope that this study may lead to novel ways to protect both men and women from HIV infection, for example, by selectively reducing the amount of anaerobic bacteria on the genitalia and thereby decreasing the risk of HIV infection.
Funding for this study was provided by the National Institutes of Health, the Bill and Melinda Gates Foundation and the Canadian Institutes of Health Research.