Fig. 6.

Impact of furin expression on virus-cell (left panel) and cell-cell fusion (right panel) driven by wt SARS-S and SARS-S variant T760R. Left panel: Pseudotypes harboring the indicated S-proteins were prepared in the presence (white bars) or absence (black bars) of co-expressed furin. After normalization for p24-content, the particles were used for infection of 293T cells in triplicates. Luciferase-activities in cell lysates were determined after 72 h and values measured for SARS-S pseudotypes prepared in the absence of overexpressed furin were set as 100%. The average of four independent experiments is shown, error bars indicate standard error of the mean (SEM). Right panel: 293T effector cells cotransfected with expression plasmids for the indicated S-variants (or transfected with empty vector as control), GAL-VP16 and furin (or transfected with empty vector as control), were co-cultivated with 293T target cells transfected with plasmids encoding a GAL-VP16-responsive luciferase gene and hACE2 (or transfected with empty vector as control) in triplicates. Luciferase-activities in cell lysates were measured two days after co-cultivation. The experiment shown is representative of three independent experiments, error bars indicate SD.