TMPRSS11D and infection: For example, transmembrane protease serine 2 (TMPRSS2)and airway trypsin-like protease TMPRSS11D activate the S proteinin HCoV-229E, SARS-CoV-1 and SARS-CoV-2 infections,39 while cathepsin L is activated in SARS-CoV and MERS-CoV.40 After the virus enters a susceptible cell, thegenome is transcribed and translated.