Functional and Genetic Analysis of Viral Receptor ACE2 Orthologs Reveals Broad Potential Host Range of SARS-CoV-2

The pandemic of a newly emerging coronavirus (SARS-CoV-2), the causative agent of severe pneumonia disease (COVID-19), is threatening global health. Epidemiological studies suggested that bats are the natural reservoir hosts for SARS-CoV-2, however, the host range of SARS-CoV-2 and the identity of intermediate hosts facilitating the transmission to humans remains unknown. Coronavirus-receptor interaction is a key genetic determinant of the host range, cross-species transmission, and tissue tropism. SARS-CoV-2 uses ACE2 as the receptor to enter the cells in a species-dependent manner, and it has been shown that human, palm civet, pig and bat ACE2 can support virus entry, but mouse ACE2 cannot. In this study, we aimed to characterize ACE2 from a diversity of species for its ability to support viral entry. We found that ACE2 is expressed in a wide range of host species, with high conservation especially in mammals. By analyzing critical amino acid residues in ACE2 for virus entry, based on the well-characterized SARS-CoV spike protein interaction with ACE2 (human, bat, palm civet, pig and ferret ACE2), we found approximately eighty ACE2 proteins from mammals could potentially function as the receptor to mediate SARS-CoV-2 entry. Functional assays showed that 44 of these mammalian ACE2 orthologs, including domestic animals, pet animals, livestock animals and even animals in the zoo or aquaria, could bind viral spike protein and support SARS-CoV-2 entry. In summary, our study demonstrated that ACE2 from a diversity of animal species could be utilized by SARS-CoV-2 to mediate viral entry, indicating it has a broad host range and highlighted that SARS-CoV-2 might be distributed much more widely than previously recognized, emphasizing the necessity to monitor the susceptible hosts, especially their potential of cross-species, which could prevent the future outbreaks.