Genomic characterization unravelling the causative role of SARS-CoV-2 Delta variant of lineage B.1.617.2 in 2nd wave of COVID-19 pandemic in Chhattisgarh, India

COVID-19 pandemic 2nd wave catastrophic effect in the state of Chhattisgarh, India, from where no exclusive genomic data yet published, has prompted us to undertake this study to unearth the causative variant. Whole-genome sequencing of SARS-CoV-2 isolated from COVID-19 infected nine vaccinated healthcare workers (HCW), thirty mild/moderate, seventeen severe, and twenty-seven deceased patients, was performed. The significant predominance of the SARS-CoV-2 variant of concern (VOC), Delta (lineage B.1.617.2) identified in sixty-four (77.1%) cases in contrast to B.1 and its sublineage in eleven (13.2%), variant under monitoring (VUM), Kappa (lineage B.1.617.1) in five (6.0%) and another VOC Alpha (lineage B.1.1.7) in three (3.6%) cases respectively (p < 0.05, χ(2) = 162.49). 88.8% vaccine breakthrough, 60% mild/moderate, 94.4% severe and 81.5% dead patients were infected by Delta. Kappa presents exclusively in mild/moderate, Alpha in vaccine breakthrough, mild/moderate, and dead patient and B.1 and its sublineages in mild, severe, and dead patient categories. Delta variant spike mutation of T19R, G142D, E156G, L452R, and deletion (F157 and R158) helps in escaping antibody response, T478K and D614G enhance viral affinity with ACE2 receptor while P681R and D950N result in higher replication and transmissibility by cleaving S1/S2 at furin site. We conclude that Delta variant predominant role along with co-occurrence of Kappa, Alpha, and B.1 variant during COVID-19 2nd wave pandemic in Chhattisgarh may pose a potential threat of future outbreak through hybrid variant evolution. Thus, intensive genomic surveillance for monitoring variant evolution and a more efficacious vaccine against the Delta and Alpha variants are required.