Fig. 4

Ins214EPE and H655Y are essential for the infectivity of Omicron to mice. A Several reverse-mutants for H655Y and Ins214EPE by mutating them back to the corresponding wild-type amino acids while keeping the N501Y mutation based on the Spike protein of the Omicron variant. NTD: N terminus domain; RBD: receptor-binding domain; SD: subdomain; S2: subunit 2. Cyan: three mutant sites. B Side and top view of S glycoprotein of Omicron. Blue: N501Y. Red: Ins214EPE. Yellow: H655Y. Cyan: other spike mutations of Omicron. C, D Representative images (C) and quantification (D) of syncytia formation upon expression of the indicated S glycoprotein in 293T-mACE2. Data are the mean ± SD of results from 4 fields (10× objective lens). More than three replicates were performed. E Expression of the luciferase reporter in 293T-mACE2 cells upon infection of viruses pseudotyped with Wild type or mutant type of S glycoproteins as indicated. Data are the mean ± SD of triplicate measurements