Gut-lung axis in COVID-19

Gut-lung axis in COVID-19

Busra AKTAS1, Belma ASLIM2

1Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Burdur Mehmet Akif Ersoy University, Burdur, Turkey https://orcid.org/0000-0001-9863-683X [email protected] (corresponding author)

2Department of Biology, Faculty of Science, Gazi University, Ankara, Turkey https://orcid.org/0000-0002-0595-7237

Abstract

The recent outbreak of the novel coronaviruses, COVID-19, affected millions of people around the world with a high mortality rate. COVID-19 is a viral respiratory diseases caused by SARS-CoV-2 but patients with COVID-19 show gastrointestinal symptoms as well, including diarrhea, vomiting, and abdominal pain. Later on, fecal samples collected from COVID-19 patients was found to be positive of SARS-CoV-2 nucleic acid and the idea of a possible fecal-oral transmission route of SARS-CoV-2 received attentions. However, not only the viral RNA but also the infectious viral particles are required for the viral infection and no proof has been demonstrated the transmission of the infectious virus particles via the fecal-oral route yet. COVID-19 has been found to cause adverse outcomes related to immune response. Increased proinflammatory cytokines and lymphocytopenia are associated with severe SARS-CoV-2 infection and may lead to multiple organ failure. There is an interaction between the gut microbiota and the lung that maintains host homeostasis and disease development with the association of immune system. This gut-lung interaction may influence the severity of COVID-19 in patients with extrapulmonary conditions. The disease severity and mortality of COVID-19 have mostly associated with elders and patients who have underlying medical conditions. Since the intestinal microbiota is disturbed as the other functions in the elderly, dysbiosis could be the reason for older adults being at high risk for severe illness from COVID-19. We think that gut-lung axis involves in COVID-19 severity with the association of dysbiosis. Disruption of the gut barrier integrity due to dysbiosis may lead to translocation of SARS-CoV-2 from the lung into the intestinal lumen via circulatory and lymphatic system. This may explain the detection of the virus in feces rather than fecal-oral transmission route. Conversely, dysbiosis in the gut microbiota results in gut permeability and may lead to secondary infection and multiple organ failure. This talk focuses on the role of the gut-lung axis in COVID-19 severity associated with dysbiosis. Additionally, this presentation aims to clarify the ambiguity in fecal-oral transmission of SARS- CoV-2.