Rapid expansion of SARS-CoV-2 variants of concern is a result of adaptive epistasis

Abstract

The SARS-CoV-2 pandemic has entered an alarming new phase with the emergence of the variants of concern (VOC), P.1, B.1.351, and B.1.1.7, in late 2020, and B.1.427, B.1.429, and B.1.617, in 2021. Substitutions in the spike glycoprotein (S), such as Asn⁵⁰¹Tyr and Glu⁴⁸⁴Lys, are likely key in several VOC. However, Asn⁵⁰¹Tyr circulated for months in earlier strains and Glu⁴⁸⁴Lys is not found in B.1.1.7, indicating that they do not fully explain those fast-spreading variants. Here we use a computational systems biology approach to process more than 900,000 SARS-CoV-2 genomes, map their spatiotemporal relationships, and identify lineage-defining mutations followed by structural analyses that reveal their critical attributes. Comparisons to earlier dominant mutations and protein structural analyses indicate that increased transmission is promoted by epistasis, i.e., the combination of functionally complementary mutations in S and in other regions of the SARS-CoV-2 proteome. We report that the VOC have in common mutations in non-S proteins involved in immune-antagonism and replication performance, such as the nonstructural proteins 6 and 13, suggesting convergent evolution of the virus. Critically, we propose that recombination events among divergent coinfecting haplotypes greatly accelerates the emergence of VOC by bringing together cooperative mutations and explaining the remarkably high mutation load of B.1.1.7. Therefore, extensive community distribution of SARS-CoV-2 increases the probability of future recombination events, further accelerating the evolution of the virus. This study reinforces the need for a global response to stop COVID-19 and future pandemics. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ”Nothing in Biology Makes Sense Except in the Light of Evolution” -Theodosius Dobzhansky