To investigate the role of cell surface proteases on CCoV-HuPn-2018pp entry, Huh7 and 293T cells expressing feline APN (fAPN) were either treated with exogenous trypsin or transfected with a plasmid expressing TMPRSS2, followed by infection with CCoV-HuPn-2018pp, with VSVpp and HCoV-229Epp as negative and positive controls, respectively. The gene discussed is ANPEP; the disease is infection.