FIG 5.

Biological interferon assay. A549 cells were infected with wtUUKV, rUUKV, rUUKdelNSs, rUUKdelNSsGFP, BUNV, or BUNdelNSs2 at an MOI of 3 or mock infected. Media were harvested at 24 h p.i. Serial dilutions of the UV-inactivated supernatant, or dilutions of IFN-β, were used to pretreat A549-Npro cells before infection with EMCV. Cells were stained with crystal violet at 4 days p.i. (A) Assay plates. (B) Relative IFN units (RIU) produced, calculated as RIU = 2^N, where N represents the number of wells that are protected from EMCV infection. The mean RIU value was calculated from data from triplicate experiments. Error bars indicate the standard errors of the means.