FIG 4.
MERS-CoV NS4a and NS4b mutants are attenuated in IFN competent cells. (A) Vero cells were infected in triplicate at an MOI of 1 with WT MERS-CoV, MERS-ΔNS4a, and MERS-ΔNS4ab. Supernatants were collected at indicated times postinfection, and infectious virus was quantified by plaque assay. (B) A549DPP4 cells were infected in triplicate at an MOI of 1 with WT MERS-CoV, MERS-ΔNS4a, and MERS-ΔNS4ab, and replication was quantified as in panel A. (C) Statistical significance for mutant virus replication versus WT was calculated by two-way ANOVA. Data are from one representative of three independent experiments. In panel A, the 72-h postinfection data point was only assessed in one out of three experiments. Data are displayed as means ± standard deviation (SD). *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001; ****, P ≤ 0.0001.