We also noticed that the cell-free infection of SARS-CoV-2 in Vero-ACE2-TMPRRS2 cells was still sensitive to treatment by endosomal inhibitors, similar to a recent report (80); we reason that this could be associated with the levels of TMPPRS2 expression on the plasma membrane of target cells used for infection, as well as viral stocks that contain furin-defective mutants generated from Vero cells. This evidence concerns the gene ACE2 and infection.