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

MedicalResearch.com 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 

MedicalResearch.com: 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.

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Binge Drinking Linked To Risky Sexual Behavior in MSM

MedicalResearch.com Interview with:
Kristen Hess  ORISE Fellow
Division of HIV/AIDS Prevention,
National Center for HIV, Viral Hepatitis, STD and TB Prevention
Centers for Disease Control and Prevention Atlanta, GA

MedicalResearch: What is the background for this study?

Response: Men who have sex with men (MSM) of all races continue to be the risk group most severely affected by HIV in the United States. CDC’s most recent HIV incidence data show that the number of new infections among MSM increased 12 percent between 2008 and 2010, with an even steeper increase among the youngest MSM. These data clearly show the urgent need to better understand the factors that affect their risk and to develop effective prevention interventions.

One specific factor is excessive alcohol use, which is responsible for 88,000 deaths in this nation each year, and cost the U.S. about $224 billion in 2006. Binge drinking (consuming ≥5 drinks for men on an occasion; ≥4 drinks for women) is the most common form of excessive alcohol consumption. The association between excessive alcohol consumption, including binge drinking, and risky sexual behaviors among MSM has had mixed results in the literature with some studies finding an association and others not. One limitation of previous work is that the definition of excessive alcohol consumption varies between studies, so results are not easily compared between studies and populations.

Our study examines the relationship between binge drinking and sexual risk behaviors among MSM who are current drinkers and who were either HIV-negative or unaware of their HIV status.

MedicalResearch: What are the main findings?

Response: We assessed the prevalence of binge drinking, using a standard definition, among a sample of MSM recruited from 20 cities across the U.S. We also examined the association between binge drinking and several risky sexual behaviors.

The findings show that 6 in 10 MSM reported binge drinking. Those who binge drank, in comparison to non-binge drinkers, were more likely to engage in risky sexual behaviors such as sex with an HIV-positive or unknown status partner and exchange sex for money or drugs at last sex, as well as more likely to have concurrent partners and more condomless sex partners in the past year.

We also found that the likelihood of risky sexual behaviors went up with increased frequency of binge drinking. In fact, MSM who reported 10 or more binge-drinking episodes in the past month were more likely to report risky behaviors. This is a critical point, especially given that, among those who binged, 22 percent reported 10 or more binge drinking episodes in the past month. Continue reading