Human Intestinal Defensin 5 Inhibits SARS-CoV-2 Invasion by Cloaking ACE2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) emerged recently and caused a coronavirus disease 2019 (COVID-19) outbreak worldwide. Angiotensin-converting enzyme-2 (ACE2) is themain receptor of SARS-CoV-2 S1 and mediates viral entry into host cells.(1) In humans, ACE2 is remarkably abundant on the membrane of lung alveolar epithelial cells and enterocytes.2 Human intestinal epithelium encompasses approximately 200 m(2) of surface area and is conceivably susceptible to SARS-CoV-2; however, the occurrence of intestinal symptoms is lower than that of respiratory symptoms as a whole,3 indicating that enterocytes are actually not as easily infected by SARS-CoV-2 as expected. We explored the underlying reason.