ACE2 and COVID-19: COVID-19 is caused by SARS-CoV-2, which belongs to Betacoronavirus and is an enveloped and positive-sense single-stranded RNA (+ssRNA) virus [6].SARS-CoV-2 mainly uses angiotensin-converting enzyme 2(ACE2) as the entry receptor [7], and it employs the cellular serine protease transmembrane serine protease 2(TMPRSS2) for spike(S) protein priming [8].