SIV, gut bacteria linked in study

Simian immunodeficiency virus has detrimental implications on the stability of the gut microbiome of Tanzanian chimpanzees, a recent Yale-led study has shown.

Led by former Yale ecology and evolutionary biology researcher Howard Ochman, the research team observed an increase in pathogenic bacteria in chimpanzees infected with the immunovirus SIV after the meticulous examination of years’ worth of their fecal samples at western Tanzania’s Gombe Stream National Park. This increase, in turn, overwhelmed chimpanzees’ already beleaguered immune systems in a lethal fashion, exacerbating a debilitating medical situation. The study was published on Sept. 11 in the journal Cell Host & Microbe.

“It’s very exciting,” said Chair of Duke University’s Department of Evolutionary Anthropology Anne Pusey, a co-author of the paper. “It’s an extraordinary system where we can study the disease, and apply [our findings] to humans.”

Study co-author Megan Shilts, a former Yale researcher and current student at the Johns Hopkins School of Public Health, said this research could change the way doctors treat HIV and AIDS patients.

“Soon, we will have a study with humans to see if it does the same thing,” she said. Though there is no guarantee of success, Shilts said it is very likely that attempts will soon be made to apply this newfound information to a clinical environment. By examining HIV patients, physicians could potentially identify similar gut bacteria and thus develop new techniques to slow the progression of the disease and keep people healthy longer, she added.

The findings outlined in the study are a result of “years of diligent, long-term observation” of Gombe, the world’s only study site where SIV is present, said study co-author Elizabeth Lonsdorf, assistant professor of psychology at Franklin & Marshall College, in a Sunday email to the News. While the initial discovery of SIV amongst these primates was thought to be unfortunate, Pusey said the team of researchers leading the Tanzanian site slowly became cognizant of the sheer criticality of their finding.

“After a few years of sampling, they were writing papers, and they saw that it [SIV] was pathogenic,” she said. “We said, ‘Hold on a minute, let’s look at this,’ and we found that … they had depleted CD-4 cells and their spleens looked terrible, very much like human AIDS patients.”

Many of her fellow researchers, she said, were surprised.

Pusey added that researchers are now able to observe the same closed group of chimpanzees over an extended period of time — typically not possible in studies with human subjects.

“It actually can show a pretty direct influence of the virus [SIV] on the microbiome. For me, it’s very exciting,” she said, noting that the scrutiny of this collection of chimpanzees will continue.

Yet in spite of the team’s optimism and excitement, Shilts pointed out that there are still several obstacles impeding the translation of their work on animals to human subjects. Researchers must obtain fecal samples from before and after an individual becomes HIV-positive, she said, which is difficult to accomplish since the precise time of infection cannot be recorded or determined in humans. She added that certain technological limitations prevented the researchers from being able to completely determine the structure of the gut bacteria.

In spite of this, Shilts said she remains optimistic.

“There will be a big push soon,” she said. “It’s very exciting.”

The study was funded by the National Institutes of Health and the National Science Foundation.

Comments