MSM: Microbes Associated with Sexual Behavior Can Alter Immune System to Increase HIV Risk Interview with:

Brent E. Palmer, PhDAssociate Professor of MedicineDirector, ClinImmune and ACI/ID Flow Cytometry FacilityDivision of Allergy and Clinical ImmunologyAurora, Colorado 80045

Brent Palmer

Brent E. Palmer, PhD
Associate Professor of Medicine
Director, ClinImmune and ACI/ID Flow Cytometry Facility
Division of Allergy and Clinical Immunology
University of Colorado Anschutz Medical College
Aurora, Colorado 80045 What is the background for this study? What are the main findings? 

Response: Previous studies showed that in western populations, men who have sex with men (MSM) have a distinct gut microbiome composition when compared with men who have sex with women (MSW).

We wanted to understand how these microbiome differences in MSM could impact their immune system. To test this, we transferred feces from healthy MSW and MSM to gnotobiotic (germ-free) mice and examined the immune system in the mice post-transplant. In mice that received transfers from MSM, there were higher frequencies of activated T cells in gut tissues, which are the primary targets of HIV.

This result suggested that gut microbes associated with MSM sexual behavior may actually contribute to HIV transmission by driving activation of HIV target cells. In fact, when we stimulated human gut derived cells with gut microbes isolated from MSM and MSW, cells that were stimulated with microbes from MSM were infected at a higher rate. What should readers take away from your report?

Response: Our study shows that microbes associated with MSM sexual behavior can alter the immune system in a way that could increase risk for HIV infection, at least in mice. What recommendations do you have for future research as a result of this work?

Response: These experiments were done in mice and in cell culture, so studies in human populations will be needed to demonstrate that the gut microbiome is indeed a risk factor for HIV infection. Additionally, it is still not clear how sexual behaviors specifically alter the gut microbiome – understanding how this occurs could lead to development of therapies that prevent or “reverse” these microbiome alterations.


Sam X. Li, Sharon Sen, Jennifer M. Schneider, Ka-Na Xiong, Nichole M. Nusbacher, Nancy Moreno-Huizar, Michael Shaffer, Abigail J. S. Armstrong, Erin Severs, Kristine Kuhn, Charles P. Neff, Martin McCarter, Thomas Campbell, Catherine A. Lozupone, Brent E. Palmer. Gut microbiota from high-risk men who have sex with men drive immune activation in gnotobiotic mice and in vitro HIV infection. PLOS Pathogens, 2019; 15 (4): e1007611 DOI: 10.1371/journal.ppat.1007611 



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