ANPEP and infection: Consistent with the results of the SPR assays, all these animal APNs (dAPN, red fox APN, giant panda APN, cat APN, bAPN, hsAPN, pAPN and acAPN) that bind to TGEV RBD can mediate the infection of TGEV into BHK-21-APN cells (Fig 2D and 2E), but TGEV was unable to infect the BHK-21 cells without the expression of APN.