FIG 4.

Protective effect of exogenous IFNs on SCC-61, SQ-20B, and RKO cells infected with VSV. SCC61 (a), SQ20B (b), or RKO (c) cells were preincubated for 18 h with recombinant human IFN-α2a or IFN-β (100 U/ml or 1,000 U/ml) and then infected with M51R VSV (left) or rwt VSV (middle) at the indicated MOIs. Viability was measured at 48 h. Results shown are the means ± SD from 4 experiments per treatment. *, P < 0.05 for 100 U/ml IFN-β versus 100 U/ml IFN-α and P < 0.05 for 1,000 U/ml IFN-β versus 1,000 U/ml IFN-α, each determined by one-way ANOVA with Tukey's posttest. Viral titers in supernatants (right) were measured at 24 h by plaque assay. Two independent experiments for SCC61 and SQ20B and three independent experiments for RKO infected with M51R VSV (circles) or rwt VSV (squares) are shown.