Extended Data Fig. 5: S-protein cleavage and fusogenicity of Omi-S and Omicron.

a, Western blot of S incorporated into virus particles. Virions generated in ACE2/TMPRSS2/Caco-2 cells were concentrated, and equal amount of total protein was loaded in each lane. S (antibody against S2 domain) and N were detected. Numbers at the bottom indicate mean ± s.d. of two independent experiments. b, S in infected cell lysates. ACE2/TMPRSS2/Caco-2 cells, infected at an MOI of 0.01, were collected at 24 hpi and processed for western blot with antibodies against S2 and nucleocapsid. β-actin served as an internal control. Numbers at the bottom indicate mean ± s.d. of two independent experiments. For gel source data, see Supplementary Fig. 2. c, Immunofluorescence staining of ACE2/TMPRSS2/293T cells with anti-nucleocapsid antibody. Nuclei was stained with DAPI. Infection was carried out at an MOI of 1 for 18 h. Left, representative images; right, size of 20 syncytia from two experimental repeats. P values were calculated by a two-tailed, unpaired t-test with Welch’s correction.