Fig 7.

Entry of PVs bearing various spike proteins: (A and B) Serially diluted PVs were used for the infection of 293T-hACE2-TMPRSS2 cells. Infectivity [relative luminescence unit (RLU)] is shown against various dilutions of PV expressing parental and mutant spikes. The statistical significance for the difference in infectious titers between WT and WT-856K 981F at a given dilution was calculated using Mann-Whitney test. (C) HEK293T cells expressing Spike and GFP were added onto the monolayer of Vero-TMPRSS2. Shown are the images of syncytia after 2-hour incubation formed by Spike variants, or without Spike (Mock). (D and E) The size of the syncytia measured in µm² (micrometer squared) plotted for indicated Spike variants. (F and G) Infectivity of PVs in the presence of TMPRSS2-inhibitor camostat or cathepsin-inhibitor E64D. The statistical significance was calculated with reference to WT. The statistical significance in D–G was calculated using Kruskal-Wallis test, and comparisons were done by Dunn’s multiple comparison post test. (H) Syncytia formation of Vero-TMPRSS2 by Spike-expressing HEK293T cells in the presence of trypsin. The images were taken after 2 hours of addition of spike-expressing 293T cells onto Vero-TMPRSS2. The statistical analysis was done by using Kruskal-Wallis test, and P values were calculated by Dunn’s multiple comparison post-test. All the experiments were repeated at least twice.