New COVID Threat: Rodents Could Be Asymptomatic Carriers of SARS-Like Coronaviruses

Some ancestral rodents likely had repeated infections with SARS-like coronaviruses, leading them to acquire tolerance or resistance to the pathogens, according to new research publishing today (November 18^th, 2021) in PLOS Computational Biology by Sean King and Mona Singh of Princeton UniversityFounded in 1746, Princeton University is a private Ivy League research university in Princeton, New Jersey and the fourth-oldest institution of higher education in the United States. It provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences, and engineering.”>Princeton University, US. This raises the possibility that modern rodents may be reservoirs of SARS-like viruses, the researchers say.

SARS-CoV-2Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the official name of the virus strain that causes coronavirus disease (COVID-19). Previous to this name being adopted, it was commonly referred to as the 2019 novel coronavirus (2019-nCoV), the Wuhan coronavirus, or the Wuhan virus.”>SARS-CoV-2, the virus that causes COVID-19First identified in 2019 in Wuhan, China, Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has spread globally, resulting in the 2019–20 coronavirus pandemic.”>COVID-19 infection, is of zoonotic origin—it jumped from a non-human animal to humans. Previous research has shown that Chinese Horseshoe bats are a host of numerous SARS-like viruses and tolerate these viruses without extreme symptoms. Identifying other animals that have adapted tolerance mechanisms to coronaviruses is important for awareness of potential viral reservoirs that can spread new pathogens to humans.

In the new research, King and Singh performed an evolutionary analysis, across mammalian species, of the ACE2 receptors, used by SARS viruses to gain entry into mammalian cells. Primates had highly conserved sequences of amino acidsAmino acids are a set of organic compounds used to build proteins. There are about 500 naturally occurring known amino acids, though only 20 appear in the genetic code. Proteins consist of one or more chains of amino acids called polypeptides. The sequence of the amino acid chain causes the polypeptide to fold into a shape that is biologically active. The amino acid sequences of proteins are encoded in the genes. Nine proteinogenic amino acids are called “essential” for humans because they cannot be produced from other compounds by the human body and so must be taken in as food.”>amino acids in the sites of the ACE2 receptor known to bind SARS viruses. Rodents, however, had a greater diversity — and an accelerated rate of evolution — in these spots. Overall, the results indicated that SARS-like infections have not been evolutionary drivers in primate history, but that some rodent species have likely been exposed to repeated SARS-like coronavirus infections for a considerable evolutionary period.

“Our study suggests that ancestral rodents may have had repeated infections with SARS-like coronaviruses and have acquired some form of tolerance or resistance to SARS-like coronaviruses as a result of these infections,” the authors add. “This raises the tantalizing possibility that some modern rodent species may be asymptomatic carriers of SARS-like coronaviruses, including those that may not have been discovered yet.”

Reference: “Comparative genomic analysis reveals varying levels of mammalian adaptation to coronavirus infections” by King SB, Singh M, 18 November 2021, PLOS Computational Biology.
DOI: 10.1371/journal.pcbi.1009560

Funding: This work has been supported in part by the National Institutes of Health (NIH) R01-GM076275 (to M.S.) and 5T32GM007388 (to Princeton University Department of Molecular Biology). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.