CTSL and infection: To produce pseudotyped viruses, cells overexpressing Furin, TMPRSS2, and Cathepsin L were transfected with SARS-CoV-2, PCoV-GD, and PCoV-GX spike expressing plasmids together with infection of VSV G pseudotyped virus19, which showed that SARS-CoV-2 containing a Furin recognition site expressed both enzymatically cleaved and uncleaved proteins in 293T cells, mainly in the cleaved form.