FIG. 2.

PS-341 impairs FPV replication in A549 cells. (A and B) A549 cells were either pretreated for 1 h with different concentrations of PS-341 or with solvent only or were left untreated. Then, cells were infected with FPV at an MOI of 0.001 (A) or 0.05 (B). After virus inoculation cells were posttreated with different concentrations of PS-341. (A) At 24 h p.i. supernatants were obtained and progeny virus titers were measured by standard plaque assay. (B) Proteasome activity and the ability of PS-341 to inhibit the proteasome was determined 24 h p.i. (C) A549 cells were pretreated with 50 nM PS-341 or solvent or left untreated for 1 h. Afterwards cells were infected with FPV at an MOI of 0.0005. Subsequent to virus inoculation cells were posttreated with 50 nM PS-341 or solvent or left untreated. After the indicated times p.i. supernatants were obtained and progeny virus titers were determined by standard plaque assay. Arrow bars in all experiments represent standard deviations of three independent experiments.