Figure 4

Requirement of the S1/S2 site for MERS-S-driven entry is cell type dependent, while the S2′ site is universally required. (a) Equal volumes of rhabdoviral vectors harboring MERS-S wt, the indicated S protein mutants, VSV-G or no glycoprotein at all (negative control) were used for transduction of Caco-2, Vero E6 cells or 293T cells that were either untreated or transfected with expression plasmid for DPP4. Transduction efficiency was quantified at 18 h post inoculation by measuring the activity of virus-encoded luciferase in cell lysates. Shown are the data from one representative experiment performed with quadruplicate samples, error bars indicate standard deviation (SD). Similar results were obtained in two separate experiments. (b) The combined results of three independent experiments carried out as described for panel a are shown. For normalization, transduction mediated by VSV particles harboring MERS-S wt was set as 100%. Error bars indicate standard error of the mean (SEM). Statistical significance of differences between transduction mediated by wt and mutant S proteins was analyzed using a paired, two-tailed students t-test (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ns, not significant).