Fig 4. Microscopic observation and immunofluorescence analysis the inhibitory activity of bis-benzylisoquinoline alkaloids against SARS-CoV-2 S-mediated cell–cell fusion.

(a) Structure of bis-benzylisoquinoline alkaloids. Vero-E6 cells co-culture with BHK that transfected with the SARS-CoV-2 S expression construct and treated with 10 μM berbamine hydrochloride, liensinine, isoliensinine, tetrandrine, fangchinoline, cepharanthine or DMSO. Cells were harvested at 12 h after treatment. The syncytial phenotype is indicated by the multinucleated giant cells as indicated by the red arrows. (b) Microscopic observation and (c) immunofluorescence images of cells staining with DAPI (blue) or anti-S Ab (green). Scale bar, 100 μm. Experiments were performed at least twice with two technical replicas per experiment.