AsianScientist (Aug. 5, 2020) – Human, bat and pangolin coronaviruses all experienced strong selective pressure at the receptor binding motif of the spike protein, resulting in near-identical genetic sequences among specific viral strains. These findings, published in Science Advances, suggest that genetic shuffling between different species may have led to the evolution of SARS-CoV-2 and its introduction into humans.
A team led by Professor Gao Feng of Duke University, US, and Jilin University, China, analyzed 43 complete genome sequences from three strains of SARS-CoV-2-like coronaviruses found in bats and pangolins. They delineated which strains were the most and least similar to the novel coronavius, with a special focus on genes related to the virus’ spike protein complex, a critical component that facilitates viral entry into host cells.
The researchers found evidence of strong evolutionary selection around the receptor binding motif—part of the spike protein’s amino acid sequence that directly contacts host cell receptors—among the bat, pangolin and human coronaviruses they studied. Amino acid sequences from these viruses and SARS-CoV-2 were identical or nearly identical in the regions adjacent to the receptor binding motif, suggesting that common evolutionary mechanisms shaped these distinct viral strains.
Specifically, their results showed that the novel coronavirus’ entire receptor binding motif was introduced through recombination with pangolin coronaviruses. Together, evolutionary selection and frequent recombination among coronaviruses from bats, pangolins and humans may have allowed the closely related viruses to readily jump between species, the authors postulate, leading to the introduction of SARS-CoV-2 in humans.
While the precise origin of SARS-CoV-2 remains a mystery, this study joins ongoing efforts to identify the source of the virus that causes COVID-19, which is critical for informing efforts to establish proper animal models, discover new drugs and vaccines, and ultimately prevent the rise of future zoonotic diseases.
“Reducing or eliminating direct human contact with wild animals is critical to preventing new coronavirus zoonoses in the future,” the authors wrote.
The proximity of different species in a wet market setting, for example, may increase the potential for cross-species spillover infections by enabling recombination between more distant coronaviruses and the emergence of mutations, they concluded.
The article can be found at: Li et al. (2020) Emergence of SARS-CoV-2 Through Recombination and Strong Purifying Selection.
Source: American Association for the Advancement of Science; Illustration: OiKeat Lam.
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