FIG. 1.

The effect of rIFN-β on PRV Be replication depends on the timing of IFN addition relative to viral infection. REF cells were treated with rat IFN-β (1,000 U/ml) 24 h prior to the addition of the viral inoculum, 6 h prior to the addition of the viral inoculum, or 1 h after the addition of the viral inoculum, or the cells were left untreated and infected at 1 PFU/cell. In all cases, virus was collected 24 h p.i., and the viral yield was determined by plaque assay. Each titer measurement was an average obtained from three independent experiments, with the error bars representing the standard deviations.