DPP4 and infection: To further investigate whether pangolin-CoV-HKU4-P251T can utilize DPP4 and ACE2 as receptors for infection, we conducted the experiments by observing the virus infectivity in wild type HeLa (HeLa-WT) cells as well as human DPP4-expressing HeLa (HeLa-hDPP4), Manis javanica pangolin DPP4-expressing HeLa (HeLa-pDPP4) and T. pachypus bat DPP4-expressing HeLa (HeLa-bDPP4), human ACE2-expressing HeLa (HeLa-hACE2), pangolin ACE2-expressing HeLa (HeLa-pACE2) and bat ACE2-expressing HeLa (HeLa-bACE2) cells (Fig. 3a, c).