Decades-Old Stool Sample Provides New Insight on HIV Susceptibility

A new study conducted on a 35-year-old blood and stool sample provides new insights into HIV research and the role the gut microbiome may have played in infection among infected individuals.

A new paper published this week in Microbiome noted that a change in the gut microbiome of some individuals made them more susceptible to HIV infection. Specifically, the research team primarily focused on homosexual men due to their higher infection rate. The scientists noted that homosexual men have a distinct fecal microbiome regardless of HIV-1 infection. However, in the paper’s abstract, the scientific team noted that it is unclear whether or not that difference in the gut microbiome affects the susceptibility and progression of HIV-1 infection.

First reported by Axios, researchers studied fecal microbiome profiles, short-chain fatty acids, and blood plasma inflammatory cytokines of 109 HIV-1 seroconverters that were taken from 1984 to 1985. The samples were taken during the Multicenter AIDS Cohort Study (MACS) before and after infection. They were then compared to 156 HIV-1-negative samples taken in the same study.

When the samples were first collected, the understanding of the gut microbiome was limited at best. Charles Rinaldo, Ph.D., a co-senior author of the study and a professor of infectious diseases at the University of Pittsburgh, noted that, in the early 1980s, the microbiome wasn’t in the “scientific lexicon” at the time. However, with advancements in research, those samples, which had been safely stored since they were taken, were now able to be examined.

“We said, ‘What the heck. Let’s look at the microbiome. There could be something important here,’” Rinaldo told Axios.

In the Microbiome article, the researchers hypothesized that the “unfavorable interplay of the host gut microbiome and the gut-associated immune system” could be a predisposing factor for HIV-1 infection in homosexual men. They also theorized that changes in the gut microbiome following HIV-1 infection negatively impact HIV-1 disease progression. The researchers wrote that this could have significant implications in the clinical management of acute HIV-1-infected individuals by exploring this concept.

The researchers concluded that pathogenic changes in the gut microbiome of homosexual men were present several months before infection with HIV-1. They noted that this was associated with increased inflammatory biomarkers, such as sCD14, sCD163, interleukin 6, and lipopolysaccharide-binding protein in the blood, which increased the risk for the development of AIDS.

The National Institutes of Health and the University of Pittsburgh found certain bacteria, such as Succinivibrionaceae, S24-7, Mogibacteriaceae, Coriobacteriaceae, and Erysipelotrichaceae, were significantly higher in the seroconverters than other bacteria types, such Odoribacteraceae, Verucomicrobiaceae, Bacteroidaceae, Barnesiellaceae, and Rikenellaceae. The researchers then noted that following HIV-1 infection, Prevotellaceae and Victivallaceae, and Bacteroides fragilis and Eubacterium cylindroides were significantly higher in those seroconverters who developed full-blown AIDS within five years, compared to seroconverters who were AIDS-free for more than 10 years without antiretroviral therapy. Additionally, the researchers found still other forms of bacteria that differentiated between infected and non-infected patients.

“To our knowledge, this is the first time we’ve been able to address what predisposed men who had sex with men to become infected with HIV and beyond that developing AIDS,” Rinaldo told Axios.

HIV has taken the lives of an estimated 35 million people in the 40 years since it first emerged in the 1980s. Currently, it is estimated that about 1.1 million Americans are living with HIV infection. It is estimated that 38,000 Americans are diagnosed with the infection each year, down significantly from peak infections.