Structural insight into antibody evasion of SARS-CoV-2 omicron variant

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to mutate and evolve with the emergence of omicron (B.1.1.529) as the new variant of concern. The rapid spread of this variant regionally and globally could be an allusion to increased infectivity, transmissibility, and antibody resistance. The omicron variant has a large set of mutations in its spike protein, specifically in the receptor binding domain (RBD), reflecting their significance in ACE2 interaction and antibody recognition. We have carried out the present study to understand how these mutations structurally impact the binding of the antibodies to their target epitope. We have computationally evaluated the binding of different classes of RBD targeted antibodies, namely, CB6 (etesevimab), REGN10933 (casirivimab), S309 (sotrovimab), and S2X259 to the omicron mutation-induced RBD. Molecular dynamics simulations and binding free energy calculations unveil the binding affinity and stability of the antibody-RBD complexes. All the four antibodies show reduced binding affinity towards the omicron RBD. The therapeutic antibody CB6 aka etesevimab was substantially affected due to numerous omicron mutations occurring in its target epitope. This study provides a structural insight into the reduced efficacy of RBD targeting antibodies against the SARS-CoV-2 omicron variant.