DPP4 and infection: Since DPP4 was not expressed in T. pachypus cells while this bat species hosts Ty-BatCoV HKU4, a close relative of MERS-CoV which can utilize hDPP4 for cell entry41,42, we overexpressed Tp-DPP4 in T. pachypus lung and kidney cells for infection by MERS-CoV.