In addition, it is generally recognized that trypsin facilitates PEDV infection in Vero cells during the different stages of the virus life cycle [62,63], demonstrating that the endogenous TMPRSS2 and MSPL in the cell lines play a crucial role in viral infection and replication by facilitating cell–cell fusion, but the specific mechanisms remain to be clarified. The gene discussed is TMPRSS2; the disease is viral infectious disease.