Fig. 3

Elastase facilitates RaTG13 and Khosta-2 S protein-mediated cell–cell fusion (A) Schematics of the cell–cell fusion assay are presented in the panel (A). (B) Spike- and EGFP-transfected HEK293 T cells were suspended, pre-incubated for 5 min with each protease (final concentration: 100 µg/mL), and overlaid onto a monolayer of VeroE6/TMPRSS2 cells. After 3 h, the GFP-positive fused cells were photographed (panel B). Scale bar = 100 μm. (C) The green signal area of GFP-positive fused cells, as in (B), was quantified using ImageJ, and the results are shown as a bar graph. The experiments were independently repeated twice, and similar results were observed. Data from a representative experiment are shown (n = 5). Statistical analysis was performed using one-way ANOVA and subsequent Dunnett’s test. *** indicates p < 0.001, **** indicates p < 0.0001, ns: no significance.