Sexual Orientation in Men Can Affect the Intestinal Flora Which Can Raise the Risk of HIV Infection

Researchers say that men who have sex with men have unique microbiomes that can affect the immune system.

A person’s sexual behavior can affect the microbiome and immune system, which can increase the risk of HIV infection, according to new research by scientists at the Medical Campus of the University of Colorado Anschutz.

HIV Virus

The intestinal microbial flora plays an important role in the formation of the human immune system. However, recent research has shown that men who have sex with men have very clear microbial characteristics compared to men who have sex with women, regardless of their HIV status.

The researchers at the University of Colorado Anschutz wanted to know whether this modified microbial model activates the T cells which are associated with a higher risk of transmission.

For this study, they collected stool samples from 35 healthy men – men who had sex with men and men who had sex with women – and transplanted them to rats. Mice receiving stool samples from men who had sex with men showed increased signs of CD4+ T cell activation, which would expose them to an increased risk of contracting HIV if they were humans.

They also isolated immune cells from the intestines of HIV-negative people and exposed them to bacteria from the stool of men who had sex with men and men who have sex with women. Human intestinal immune cells exposed to MSM feces were more likely to be infected with HIV in vitro. This, in turn, was associated with increased immune activation by these fecal bacteria.

“These results demonstrate a direct link between the intestinal flora composition and immune activation in HIV-negative and HIV-positive men who had sex with men and justify the study of the intestinal microbiome as a risk factor for HIV transmission,” said Ph.D. student Brent Palmer and Associate Professor of Allergology and Clinical Immunology at McGill University School of Medicine.

The exact reason why the microbial cultures of men who have sex with men are so different remains unknown.

“There is a unique microbiome connection in men who have sex with men, which increases immune activation in the intestines and can also lead to higher levels of HIV infection,” says Palmer. “But we still don’t know exactly why.”

However, it is important to understand this microbiome, says Palmer, because it can directly affect the immune system of high-risk individuals and lead to an increased risk of HIV infection.

The co-authors of the study are Dr. Sam X. Li and Dr. Catherine Lozupone from the Medical Campus of the University of Colorado Anschutz.