More than infectious
“A growing body of evidence suggests that severity of illness from COVID-19 is largely determined by the patient’s aberrant immune response to the virus,” Jatin Roper, MD, of Duke University, Durham, N.C., said in an interview. “Therefore, a critical question is: What patient factors determine this immune response? The gut microbiota closely interact with the host immune system and are altered in many immunological diseases,” he said. “Furthermore, the SARS-CoV-2 virus infects enterocytes in the intestine and causes symptomatic gastrointestinal disease in a subset of patients. Therefore, understanding a possible association between gut microbiota and COVID-19 may reveal microbial species involved in disease pathogenesis,” he emphasized.
In the current study, “I was surprised to find that COVID-19 infection is associated with depletion of immunomodulatory gut bacteria,” said Dr. Roper. “An open question is whether these changes are caused by the SARS-CoV-2 virus and then result in altered immune response. Alternatively, the changes in gut microbiota may be a result of the immune response or other changes associated with the disease,” he said.
“COVID-19 is an immunological disease, not just an infectious disease,” explained Dr. Roper. “The gut microbiota may play an important role in the pathogenesis of the disease. Thus, specific gut microbes could one day be analyzed to risk stratify patients, or even modified to treat the disease,” he noted.
Beyond COVID-19
“Given the impact of the gut microbiota on health and disease, as well as the impact of diseases on the microbiota, I am not at all surprised to find that there were significant changes in the microbiota of COVID-19 patients and that these changes are associated with inflammatory cytokines, chemokines, and blood markers of tissue damage,” said Anthony Sung, MD, also of Duke University.
According to Dr. Sung, researchers have already been investigating possible connections between gut microbiota and other conditions such as Alzheimer’s disease, and it’s been hypothesized that these connections are mediated by interactions between the gut microbiota and the immune system.
“While this is an important paper in our understanding of COVID-19, and highlights the microbiome as a potential therapeutic target, we need to conduct clinical trials of microbiota-based interventions before we can fully realize the clinical implications of these findings,” he said.
The study was supported by the Health and Medical Research Fund, the Food and Health Bureau, The Government of the Hong Kong Special Administrative Region, and donations from Hui Hoy & Chow Sin Lan Charity Fund Limited, Pine and Crane Company Limited, Mr. Hui Ming, and The D.H. Chen Foundation. The researchers had no financial conflicts to disclose. Dr. Roper and Dr. Sung had no financial conflicts to disclose.
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