The COVID-19 pandemic has been an emerging threat to global public health. Several lines of evidence suggest that the causative virus SARS-CoV-2 infects the human intestinal epithelial cells as well as airway epithelial cells, suggesting that the enteric infection of SARS-CoV-2 has destructive effects on the intestinal microbiota and subsequently airway physiology and immunity through the gut-lung axis. Despite the important roles of the gut-lung axis in the antiviral immunity, only limited information is currently available concerning COVID-19-specific changes in the gut microbiome. This review summarizes recent knowledge of intestinal dysbiosis associated with COVID-19 patients and its potential contribution to the respiratory symptoms through the gut-lung axis. We also discuss the possibility of prophylactic and therapeutic use of probiotics in COVID-19, including our ongoing trial using Lactobacillus plantarum, which is known to have a wide variety of immunomodulatory activity against respiratory viral infections.

To develop probiotics for the management of COVID-19, more effort is required to isolate and/or identify more probiotic strains with the ability to reduce the viral load and suppress hyperinflammation via different mechanisms of action. Bacterial species outside of the genera Lactobacillus and Bifidobacterium should be explored. Randomized controlled trials with large cohorts aimed at evaluating the prophylactic and therapeutic use of probiotics are also essential. As described above, the respiratory tract is inhabited by commensal bacterial communities, and the respiratory microbiota is known to be closely associated with susceptibility to and severity of respiratory infections. In fact, metatranscriptomic studies have revealed that COVID-19 patients have more disrupted airway microbiome. Interestingly, bacteria within gut-specific genus Bacteroides are commonly and abundantly found in bronchoalveolar lavage fluid from ARDS patients. Indirect manipulation of the respiratory microbiome with oral probiotics may be a promising adjunctive therapy to alleviate lifethreatening hyperinflammation in COVID-19.

Thanks and Regards,

Alpine

Associate Editor J

ournal of Clinical Trials

clinicaltrials@eclinicalsci.com