Researchers Outline How Gut Serves as Harbor for HIV, COVID-19

Recent years have seen deeper scrutiny and research into gut health and its implications across a variety of diseases, including diabetes and psoriasis. Other research has been focused on how viruses are affected by gut and the microbiota, the trillions of microbes that live symbiotically in the human body, most of them in the gut.

(Some experts reserve the term microbiome for the genes of those microbes as opposed to the organisms themselves. More commonly, though, microbiome is used to refer to the organisms themselves.)

In a recent paper in the journal Gut, Markus Neurath of the Friedrich-Alexander University Erlangen-Nürnberg in Germany, and his colleagues outlined the latest insights into how the gut microbiome harbors viruses like HIV and COVID-19, and what that means for HIV treatment and repeat COVID-19 infection.

“Recent studies have started to explore the composition and function of the gut virome, which provides a rich reservoir for bacteriophages and viruses,” wrote Neurath and his co-authors. “These studies have highlighted the concept that bacteriophages and viruses play a seminal role in shaping the bacterial microbiome and are important in controlling gut homeostasis.”

The researchers explain that a significant number of HIV-infected cells reside within the gut, even in patients being treated for HIVwith antiretroviral therapy.

Research findings have pointed to the mucosa — the innermost layer of the gastrointestinal tract — as being a reservoir for HIV-infected cells, accounting for an estimated 83% to 95% of all HIV-infected cells in the body. Previous reports have documented significantly higher rates of HIV-infected cells in the mucosa, ranging from five to twelve times as high as levels in the blood.

“The intestine has been identified as a crucial reservoir for HIV-infected immune cells that may reach the bloodstream via immune cell trafficking, thereby potentially impairing the efficacy of ART (antiretroviral therapy) in affected patients,” explained the researchers. “Furthermore, more recent studies of patients with COVID-19 on SARS-CoV-2 infection uncovered a potentially important role of persistent infection of intestinal epithelial cells for prolonged memory immune responses and prevention of reinfection.”

According to the researchers, several studies have indicated that SARS-CoV-2, the virus that causes COVID-19, was persistent in the epithelial cells, which line the surfaces of the body, including in the gut, in about one-third for several weeks or months after they were diagnosed with COVID-19. The findings suggest that the virus antigen remains in the gut even after recovering from COVID-19.

Because intestinal epithelial cells frequently turnover, the persistence of the virus in the gut suggest the virus continues to replicate.

Notably, the researchers underscore that the findings offer insight into a “rapid and effective adaptive immune response” to SARS-CoV-2 if exposed again and how this immune response can offer immunity against COVID-19 reinfection.