Journal Article

Natural selection in the evolution of SARS-CoV-2 in bats created a generalist virus and highly capable human pathogen

MacLean, Oscar A., Weaver, Steven, Boni, Maciej F., Kosakovsky Pond, Sergei L., Lemey, Philippe, Lytras, Spyros, Singer, Joshua B., Robertson, David L.

2021

Overview

Virus host shifts are generally associated with novel adaptations to exploit the cells of the new host species optimally. Surprisingly, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has apparently required little to no significant adaptation to humans since the start of the Coronavirus Disease 2019 (COVID-19) pandemic and to October 2020. Here we assess the types of natural selection taking place in Sarbecoviruses in horseshoe bats versus the early SARS-CoV-2 evolution in humans. While there is moderate evidence of diversifying positive selection in SARS-CoV-2 in humans, it is limited to the early phase of the pandemic, and purifying selection is much weaker in SARS-CoV-2 than in related bat Sarbecoviruses . In contrast, our analysis detects evidence for significant positive episodic diversifying selection acting at the base of the bat virus lineage SARS-CoV-2 emerged from, accompanied by an adaptive depletion in CpG composition presumed to be linked to the action of antiviral mechanisms in these ancestral bat hosts. The closest bat virus to SARS-CoV-2, RmYN02 (sharing an ancestor about 1976), is a recombinant with a structure that includes differential CpG content in Spike; clear evidence of coinfection and evolution in bats without involvement of other species. While an undiscovered “facilitating” intermediate species cannot be discounted, collectively, our results support the progenitor of SARS-CoV-2 being capable of efficient human–human transmission as a consequence of its adaptive evolutionary history in bats, not humans, which created a relatively generalist virus.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: ACE2 / Adaptation / Adaptations / Analysis / Angiotensin-converting enzyme 2 / Animals / Bats / Binding / Biological evolution / Biology and life sciences / China / Chiroptera - virology / Computer and Information Sciences / Coronaviruses / COVID-19 / COVID-19 - epidemiology / COVID-19 - transmission / COVID-19 - virology / CpG islands / Disease transmission / DNA-directed RNA polymerase / Epidemics / Evolution / Evolution, Molecular / Genetic aspects / Genome, Viral / Host Specificity / Humans / Identification and classification / Infections / Medicine and health sciences / Methods / Natural history / Natural selection / Pandemics / Phylogeny / Physiological aspects / Quality control / Receptors, Virus - genetics / Recombination / Respiratory diseases / Respiratory tract / RNA viruses / RNA-directed RNA polymerase / SARS-CoV-2 - genetics / SARS-CoV-2 - pathogenicity / Selection, Genetic / Severe acute respiratory syndrome / Severe acute respiratory syndrome coronavirus 2 / Species / Substitutes / Viral diseases / Viral Zoonoses - genetics / Viral Zoonoses - transmission / Viral Zoonoses - virology / Viruses