ACE2 and COVID-19: SARS-CoV-2 virus, the causative agent of COVID-19, infects a wide array of cells, including epithelial cells, endothelial cells, and macrophages of multiple organs such as lung, gut, liver and kidneys via angiotensin-converting enzyme 2 (ACE2) as a receptor and transmembrane protease serine 2 (TMPRSS2) as an activating protease (1).