Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the recent pandemic COVID-19, is reported to have originated from bats, with its intermediate host unknown to date. Here, we screened 26 animal counterparts of the human ACE2 (hACE2), the receptor for SARS-CoV-2 and SARS-CoV, and found that the ACE2s from various species, including pets, domestic animals and multiple wild animals, could bind to SARS-CoV-2 receptor binding domain (RBD) and facilitate the transduction of SARS-CoV-2 pseudovirus. Comparing to SARS-CoV-2, SARS-CoV seems to have a slightly wider range in choosing its receptor. We further resolved the cryo-electron microscopy (cryo-EM) structure of the cat ACE2 (cACE2) in complex with the SARS-CoV-2 RBD at a resolution of 3 Å, revealing similar binding mode as hACE2 to the SARS-CoV-2 RBD. These results shed light on pursuing the intermediate host of SARS-CoV-2 and highlight the necessity of monitoring susceptible hosts to prevent further outbreaks.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been spreading worldwide and causing a global pandemic. Bat-origin RaTG13 is currently the most phylogenetically related virus. Here, we obtained the complex structure of RaTG13 receptor binding domain (RBD) with human ACE2 (hACE2), and further evaluated the binding of RaTG13 RBD to 24 additional ACE2 orthologs. By substituting residues in RaTG13 RBD with their counterparts in SARS-CoV-2 RBD, we found that residue 501, the major position found in VOCs 501Y.V1/V2/V3, plays a key role in determining the potential host range of RaTG13. We also found that SARS-CoV-2 could induce strong cross-reactive antibodies to RaTG13 and identified a SARS-CoV-2 MAb, CB6, that could cross-neutralize RaTG13 pseudovirus. These results elucidate the receptor binding and host-adaption mechanisms of RaTG13 and emphasize the importance of continuous surveillance of coronaviruses (CoVs) carried by animal reservoirs to prevent another spill-over of CoVs.

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