ANPEP and infection: Consistent with the results of the SPR assays, all these animal APNs (dAPN, pAPN, acAPN, hAPN, rmAPN, mAPN, rAPN and chAPN) that bind to PDCoV RBD can mediate the infection of PDCoV into BHK-21 cells (Fig 1D and 1E), but PDCoV was unable to infect the BHK-21 cells without the expression of APN.