Fig. 3: Identification of mutation(s) for the reduced fusogenicity of BA.1.

Cell-cell fusion assay was performed with BA.1-associated S mutants. The various truncated S-SmBit transfected donor (HeLa) cells and the LgBit transfected recipient (293ACE2) cells were mixed 24 h post-transfection and were incubated for 48 h. After incubation, luminescence signals were measured by a POLARstar Omega plate reader. a Individual mutations were introduced into the BA.1 S sequence. Except for the corresponding mutations, the rest of the sequence is same as the native BA.1 S sequence. Similarly, the combination mutations were also introduced into the BA.1 S sequence. All data points are presented as mean values (SD, n = 4-8 biological independent replicates). For statistical comparison, adjusted P values are shown (vs BA.1, *P < 0.05; ****P < 0.0001; ns: not significant). All results are representative of three independent experiments. b Individual mutations were introduced into the Wuhan S sequence. Except for the corresponding mutations, the rest of the sequence is same as the native Wuhan S sequence. Similarly, the combination mutations were also introduced into the Wuhan S sequence. All data points are presented as mean values (SD, n = 4-8 biological independent replicates). For statistical comparison, adjusted P values are shown (vs Wuhan, **P < 0.01; ****P < 0.0001; ns: not significant). All results are representative of three independent experiments. c The fusogenic activities of various BA.1 subvariants S constructs were measured similarly. All data points are presented as mean values (SD, n = 8 biological independent replicates). For statistical comparison, adjusted P values are shown (vs BA.1, **P < 0.01; ****P < 0.0001; ns: not significant). All results are representative of three independent experiments.