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Researchers at the UCLA Fielding School of Public Health report that changes in the balance of microbes in the gastrointestinal tract of men with human immunodeficiency virus are associated with increasing amounts of the virus.
A person’s gastrointestinal tract contains a delicate balance of bacteria, viruses and fungi. Scientists believe these microbes play an important role in regulating digestion, immune system function and other processes. During this study, researchers found that changes in the balance of these microbes in the gastrointestinal tract of men with human immunodeficiency virus (HIV) were associated with increasing amounts of the virus. They found that, while people with no detectable levels of HIV still have an altered microbial balance, this disbalance worsens with increasing amounts of plasma HIV RNA. To carry out the study, researchers used a novel analytic strategy to incorporate a large amount of clinical and behavioral data. This approach may make it easier for other scientists to reproduce this group’s findings in future studies of HIV and the microbiome.
Previous research has suggested that HIV alters the composition and function of the gastrointestinal microbiome, inducing shifts from beneficial bacteria to those with pro-inflammatory and pathogenic properties. Previous studies, however, have not accounted for how a person’s sexual behavior, sexually transmitted infection diagnosis, substance use or other characteristics may alter the microbiome. As a result, the effects of HIV on the microbiome had not been adequately described and many conflicting findings appear in the literature.
The researchers analyzed rectal swabs and clinical and behavioral data from 383 participants in an ongoing study of diverse young men who have sex with men (the mSTUDY). They assessed the microbiome composition through genetic sequencing of bacteria collected using rectal swabs. The researchers used a statistical method of re-weighting the study sample to control for confounding factors and to examine differences in microbial composition between groups of participants with different levels of plasma HIV RNA.
The study shows that HIV is associated with a disruption of the gastrointestinal microbiome in a dose-dependent manner. Although more research is needed, an imbalance in the microbes of the gastrointestinal tract among people with HIV is thought to lead to premature aging of the immune system and development of health issues related to inflammation.
The study’s lead author is Ryan Cook, a doctoral candidate in the department of epidemiology at the UCLA Fielding School of Public Health. His doctoral advisor, Pamina Gorbach, professor of epidemiology at the UCLA Fielding School of Public Health, and doctoral committee member Dr. Grace Aldrovandi, chief of the division of infectious diseases at UCLA Mattel Children’s Hospital and professor of pediatrics at the David Geffen School of Medicine at UCLA, are co-senior authors. Other authors include Dr. Jennifer Fulcher, Dr. Nicole Tobin, Dr. Fan Li, David Lee, Marjan Javanbakht, Ron Brookmeyer and Steve Shoptaw, all at UCLA, and Dr. Robert Bolan from the Los Angeles LGBT Center.
The research is published in the journal AIDS.
The study was primarily supported by the National Institute on Drug Abuse and the UCLA Center for HIV Identification, Prevention, and Treatment Services (CHIPTS). Additional support was provided by the UCLA AIDS Institute and UCLA CFAR Microbiome and Mucosal Immunology Core as well as the National Institute of Allergy and Infectious Diseases and Eunice Kennedy Shriver National Institute of Child Health and Human Development.