The high transmissibility and infectivity of a SARS-CoV-2 variant is usually ascribed to the Spike mutations, while emerging non-spike mutations might be a serious threat to the current Spike-recombinant vaccines. In addition to mutations in structural Spike glycoprotein, rapid accumulation of mutations across non-structural genes is leading to continuous virus evolution, altering its pathogenicity. We performed whole genome sequencing of SARS-CoV-2 positive samples collected from different clinical groups from eastern India, during the second pandemic wave (April-May, 2021). In addition to the several common spike mutations in Delta variant, two mutually explicit signature constellations of non-spike co-appearing mutations were identified, driving symptomatic and asymptomatic infections. We attempted to correlate these unique signatures of non-Spike co-appearing mutations to COVID-19 disease outcome. Results revealed that the Delta strains harboring a unique constellation of 9 non-spike co-appearing mutations could be the wheeler and dealer of symptomatic infection, even post vaccination. The strains predominantly driving asymptomatic infection possessed 7 non-spike co-appearing mutations, which were mutually exclusive in contrast to the set of mutations causing symptomatic disease. Phylodynamic analysis depicted high probability of emergence of these unique sub-clusters within India, with subsequent spread worldwide. Interestingly, some mutations of this signature were selected in Omicron and IHU variants, which suggest that gradual accumulation of such co-existing mutations may lead to emergence of more “vaccine-evading variants” in future. Hence, unfaltering genome sequencing and tracking of non-Spike mutations might be significant in formulation of any future vaccines against emerging SARS-CoV-2 variants that might evade the current vaccine-induced immunity.

The third SARS-CoV-2 pandemic wave causing Omicron variant has comparatively higher replication rate and transmissibility than the second wave-causing Delta variant. The exact mechanism behind the differential properties of Delta and Omicron in respect to infectivity and virulence is not properly understood yet. This study reports the analysis of different mutations within the receptor binding domain (RBD) of spike glycoprotein and non-structural protein (nsp) of Delta and Omicron strains. We have used computational studies to evaluate the properties of Delta and Omicron variants in this work. Q498R, Q493R and S375F mutations of RBD showed better docking scores for Omicron compared to Delta variant of SARS-CoV-2, whereas nsp3_L1266I with PARP15 (7OUX), nsp3_L1266I with PARP15 (7OUX), and nsp6_G107 with ISG15 (1Z2M) showed significantly higher docking score. The findings of the present study might be helpful to reveal the probable cause of relatively milder form of COVID-19 disease manifested by Omicron in comparison to Delta variant of SARS-CoV-2 virus. Supplementary Information The online version contains supplementary material available at 10.1007/s13337-023-00823-0.

Accumulation of diverse mutations across the structural and nonstructural genes is leading to rapid evolution of SARS‐CoV‐2, altering its pathogenicity. We performed whole genome sequencing of 239 SARS‐CoV‐2 RNA samples collected from both adult and pediatric patients across eastern India (West Bengal), during the second pandemic wave in India (April–May 2021). In addition to several common spike mutations within the Delta variant, a unique constellation of eight co‐appearing non‐Spike mutations was identified, which revealed a high degree of positive mutual correlation. Our results also demonstrated the dynamics of SARS‐CoV‐2 variants among unvaccinated pediatric patients. 41.4% of our studied Delta strains harbored this signature set of eight co‐appearing non‐Spike mutations and phylogenetically out‐clustered other Delta sub‐lineages like 21J, 21A, or 21I. This is the first report from eastern India that portrayed a landscape of co‐appearing mutations in the non‐Spike proteins, which might have led to the evolution of a distinct Delta subcluster. Accumulation of such mutations in SARS‐CoV‐2 may lead to the emergence of “vaccine‐evading variants.” Hence, monitoring of such non‐Spike mutations will be significant in the formulation of any future vaccines against those SARS‐CoV‐2 variants that might evade the current vaccine‐induced immunity, among both the pediatric and adult populations.

No abstract