Evolving Infection Paradox of SARS-CoV-2: Fitness Costs Virulence?

ABSTRACT

SARS-CoV-2 is evolved into eight fundamental clades where four (G, GH, GR, and GV) are globally prevalent in 2020. How the featured co-occurring mutations of these clades are linked with viral fitness is the main question here and we thus proposed a hypothetical model using in silico approach to explain the plausible epistatic effects of those mutations on viral replication and transmission. Molecular docking and dynamics analyses showed the higher infectiousness of a spike mutant through more favorable binding of G614 with the elastase-2. RdRp mutation p.P323L significantly increased genome-wide mutations (p<0.0001) since more flexible RdRp (mutated)-NSP8 interaction may accelerate replication. Superior RNA stability and structural variation at NSP3C241T might impact protein and/or RNA interactions. Another silent 5UTRC241T mutation might affect translational efficiency and viral packaging. These four G-clade-featured co-occurring mutations might increase viral replication. Sentinel GH-clade ORF3ap.Q57H constricted ion-channel through inter-transmembrane-domain interaction of cysteine(C81)-histidine(H57) and GR-clade Np.RG203-204KR would stabilize RNA interaction by a more flexible and hypo-phosphorylated SR-rich region. GV-clade viruses seemingly gained the evolutionary advantage of the confounding factors; nevertheless, Np.A220V might modulate RNA binding with no phenotypic effect. Our hypothetical model needs further retrospective and prospective studies to understand detailed molecular events featuring the fitness of SARS-CoV-2.