Background: SARS-CoV-2 is continuously spreading worldwide at an unprecedented scale and evolved into seven clades according to GISAID where four (G, GH, GR and GV) are globally prevalent in 2020. These major predominant clades of SARS-CoV-2 are continuously increasing
COVID-19 MESHD cases worldwide; however, after an early rise in 2020, the death-case ratio has been decreasing to a plateau. G clade viruses contain four co-occurring mutations in their genome (C241T+C3037T+C14408T:
RdRp PROTEIN.P323L+A23403G:spike.D614G). GR, GH, and GV strains are defined by the presence of these four mutations in addition to the clade-featured mutation in GGG28881-28883AAC:N. RG203-204KR, G25563T:
ORF3a PROTEIN.Q57H, and C22227T:spike.A222V+C28932T-N.A220V+G29645T, respectively. The research works are broadly focused on the
spike protein PROTEIN mutations that have direct roles in receptor binding, antigenicity, thus viral transmission and replication fitness. However, mutations in other proteins might also have effects on viral pathogenicity and transmissibility. How the clade-featured mutations are linked with viral evolution in this pandemic through gearing their
fitness MESHD and virulence is the main question of this study. Methodology: We thus proposed a hypothetical model, combining a statistical and structural bioinformatics approach, endeavors to explain this infection paradox by describing the epistatic effects of the clade-featured co-occurring mutations on viral
fitness MESHD and virulence. Results and Discussion: The G and GR/GV clade strains represent a significant positive and negative association, respectively, with the death-case ratio (incidence rate ratio or IRR = 1.03, p <0.001 and IRR= 0.99/0.97, p < 0.001), whereas GH clade strains showed no association with the Docking analysis showed the higher infectiousness of a spike mutant through more favorable binding of G614 with the
elastase-2 HGNC.
RdRp PROTEIN mutation p.P323L significantly increased genome-wide mutations (p<0.0001) since more expandable
RdRp PROTEIN (mutant)-
NSP8 PROTEIN interaction may accelerate replication. Superior RNA stability and structural variation at
NSP3 HGNC NSP3 PROTEIN:C241T might impact upon protein or RNA interactions. Another silent 5'UTR:C241T mutation might affect translational efficiency and viral packaging. These G-featured co-occurring mutations might increase the viral load, alter immune responses in host and hence can modulate intra-host genomic plasticity. An additional viroporin
ORF3a PROTEIN:p.Q57H mutation, forming GH-clade, prevents ion permeability by cysteine (C81)-histidine (H57) inter-transmembrane-domain interaction mediated tighter constriction of the channel pore and possibly reduces viral release and immune response. GR strains, four G clade mutations and N:p.RG203-204KR, would have stabilized RNA interaction by more flexible and hypo-phosphorylated SR-rich region. GV strains seemingly gained the evolutionary advantage of superspreading event through confounder factors; nevertheless, N:p.A220V might affect RNA binding. Conclusion: These hypotheses need further retrospective and prospective studies to understand detailed molecular and evolutionary events featuring the
fitness MESHD and virulence of SARS-CoV-2.