Researchers to Study Role of the Male Microbiome in HIV Transmission

The multi-institution research team, led by GW Associate Professor Cindy Liu, was awarded $3.5 million for the five-year project.

March 8, 2022

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The George Washington University Milken Institute School of Public Health has been awarded more than $3.5 million to study factors that shape the male microbiome in the urogenital tract. The human microbiome is made up of trillions of microbes all over the body, including those that live in the urethra, the bladder and genitals. The goal of the new project is to develop solutions aimed at reducing sexual transmission of HIV.

Very little is known about how different factors such as antibiotic use and sexual activity can help shape the genital microbiome, particularly in men. Scientists know that certain female genital microbiome profiles have been linked to increased risk of preterm births, surgical infections and sexually transmitted infections, including HIV.

“There has been much more focus on studying the female genital microbiome,” said Cindy Liu, associate professor of environmental and occupational health and chief medical officer at the GW Antibiotic Resistance Action Center. “My team and my collaborators are one of the very few groups focused on studying the male genital microbiome, which can have important implications for male and female reproductive health since we expect that genital microbiome can be shared by sexual partners.”

Liu is the principal investigator of the five-year research project funded by the National Institute of Diabetes and Digestive and Kidney Diseases, which is part of the National Institutes of Health. She will collaborate with researchers from the Rakai Health Sciences Program, Johns Hopkins University, University of Toronto and Western University.

Previous work has found that men with higher amounts of certain genital bacteria are more likely to become infected by HIV, Liu said. The team wondered where the bacteria came from and about the factors that cause the transmission of these anaerobic bacteria—bacteria that do not thrive in the presence of oxygen. 

“In addition to understanding what drives the transmission of these specific bacteria within the genital microbiome, we also want to understand how antibiotic treatments impact the male genital microbiome,” she said.

To answer these questions, GW researchers will conduct multiple studies, including those of adolescent boys before and after they become sexually active. The team will use samples from an earlier study undertaken with Johns Hopkins University. Additionally, GW researchers will work with Rakai Health Sciences Program to study sexual partners and with University of Toronto to research the impact of antibiotic treatment on the male genital microbiome.

This project will use a novel foreskin tissue culture model to directly study the impact of environmental conditions including pH, oxygenation, antibiotics and metabolites on genital bacteria transmission. Using this type of model, Liu hopes researchers can directly compare different ways to change the genital microbiome.

Knowledge gained from the study could be used to develop new ways to protect people from HIV infection, Liu said.

“What makes someone more likely to acquire the genital bacteria that increase their risk for HIV infection?” Liu said. “And what can we do to change that—and reduce that risk?”