Fold increase in (A) Oas1a, (B) Oas1b, (C) Irf7,(D) Irf1 and (E) IFN beta mRNA expression levels in pC57BL/6, pRIG-I−/−, pMDA5−/− and pIPS-1−/− MEFs was measured by real-time qRT-PCR. Each experiment was repeated at least twice in triplicate. The mRNA level of each gene was normalized to the level of GAPDH mRNA in that sample and is shown as the fold change over the amount of mRNA in mock samples expressed in RQUs. The error bars represent the calculated SEM (n = 3) and are based on an RQMin/Max of the 95% confidence level. (F) Culture fluid harvested at the indicated times after infection was titered for infectivity by plaque assay. Each data point is the average of duplicate titrations from at least two experiments. Error bars indicate SDM.