FIG. 4.

Beta interferon mRNA and secreted protein levels from HEC-1B cells, which lack a functional alpha/beta interferon receptor, infected with wild-type (WT) and 3A-2 mutant poliovirus and treated with double-stranded RNA. (a) RNase protection assay. HEC-1B cells were infected with wild-type poliovirus or 3A-2 mutant poliovirus at 20 PFU/cell. After 1.5 h of incubation at 37°C, cells were treated with 175 μg of poly(I):poly(C) and 800 μg of DEAE-dextran per ml in serum-free medium. RNA was collected at the indicated times (hours) postinfection (p.i.), and the RNase protection assay was performed as described in Materials and Methods. The solid arrow denotes beta interferon mRNA, and the open arrow identifies cyclophilin mRNA. (b) PhosphoImager quantitative analysis from the gel in panel a along with replicate experiments analyzed on the same gel. Standard error of replicated experiments is shown. (c) Single-cycle growth curve for HEC-1B cells infected at 20 PFU/cell with either wild-type (WT) or 3A-2 mutant virus.