Abstract
The COVID-19 pandemic has caused an unprecedented global public health and economic crisis. The origin and emergence of its causal agent, SARS-CoV-2, in the human population remains mysterious, although bat and pangolin were proposed to be the natural reservoirs. Strikingly, unlike the SARS-CoV-2-like coronaviruses (CoVs) identified in bats and pangolins, SARS-CoV-2 harbors a polybasic furin cleavage site in its spike (S) glycoprotein. SARS-CoV-2 uses human angiotensin-converting enzyme 2 (ACE2) as its receptor to infect cells. Receptor recognition by the S protein is the major determinant of host range, tissue tropism, and pathogenesis of coronaviruses. In an effort to search for the potential intermediate or amplifying animal hosts of SARS-CoV-2, we examined receptor activity of ACE2 from 14 mammal species and found that ACE2s from multiple species can support the infectious entry of lentiviral particles pseudotyped with the wild-type or furin cleavage site-deficient S protein of SARS-CoV-2. ACE2 of human/rhesus monkey and rat/mouse exhibited the highest and lowest receptor activities, respectively. Among the remaining species, ACE2s from rabbit and pangolin strongly bound to the S1 subunit of SARS-CoV-2 S protein and efficiently supported the pseudotyped virus infection. These findings have important implications for understanding potential natural reservoirs, zoonotic transmission, human-to-animal transmission, and use of animal models.IMPORTANCE SARS-CoV-2 uses human ACE2 as a primary receptor for host cell entry. Viral entry mediated by the interaction of ACE2 with spike protein largely determines host range and is the major constraint to interspecies transmission. We examined the receptor activity of 14 ACE2 orthologs and found that wild-type and mutant SARS-CoV-2 lacking the furin cleavage site in S protein could utilize ACE2 from a broad range of animal species to enter host cells. These results have important implications in the natural hosts, interspecies transmission, animal models, and molecular basis of receptor binding for SARS-CoV-2.
Highlights
Coronavirus disease 2019 (COVID-19) was first identified in Dec. 2019 in the city of Wuhan, China [1], and has since spread worldwide, causing 2.3 million infected and around 160,000 fatalities as of April 18th, 2020.These numbers are still growing rapidly
In an effort to search for potential animal hosts, we examined the receptor activity of ACE2 from 14 mammal species, including human, rhesus monkey, Chinese horseshoe bat (Rs bat), Mexican free-tailed bat (Tb bat), rat, mouse, palm civet, raccoon dog, ferret badger, hog badger, canine, feline, rabbit, and pangolin for SARS-CoV-2 and a mutant virus lacking the furin cleavage site in the S protein
Syncytia formation was only seen for cells expressing Human ACE2 (hACE2), but not hACE1, mixed with cells expressing the S protein of SARS-CoV-2 or SARS-CoV. These results confirm that hACE2 is the bone fide entry receptor for SARS-CoV-2
Summary
Coronavirus disease 2019 (COVID-19) was first identified in Dec. 2019 in the city of Wuhan, China [1], and has since spread worldwide, causing 2.3 million infected and around 160,000 fatalities as of April 18th, 2020 (https://coronavirus.jhu.edu/map.html). Coronavirus 2 (SARS-CoV-2; initially named as 2019-nCoV) [2, 3]. The origin of SARS-CoV-2 and its emergence in the human population remain mysterious. Sequencing analyses showed that the genome of SARS-CoV-2 shares 79.5%, 89.1%, 93.3%, and 96.2% nucleotide sequence identity with that of human SARS-CoV, bat coronavirus (CoV) ZC45, bat CoV
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