TMPRSS2 and infection: In order to observe the proliferation of PEDV more intuitively and clearly, the syncytium formation (cell-cell fusion), the characteristic CPE [61], were observed post-infection, and our results clearly demonstrated that cell-cell fusion was shown in Vero/TMPRSS2, Vero/MSPL, and Vero cells with 3 ug/mL trypsin, but not in the Vero cells without trypsin.