Viral gene transcription and protein translation were inhibited by CP1 treatment. (A) Cells were inoculated with CH-1a at an MOI of 0.1 in the presence of CP1 (480 μg/ml) or YPD (control) for 6, 12, 24, 36, or 48 h. Viral RNA transcription was determined with qRT–PCR at different time points after treatment. The level of PRRSV ORF7 mRNA was normalized to the level of GAPDH mRNA in the same sample. (B) CP1 or YPD (control) was added to CH-1a for 2 h at 37°C, and the mixture was then used to infect cells for 2 h at 37°C. The inoculum was removed and the cells were cultured for another 36 h and then harvested for immunoblotting analysis. (C, D, and E) CP1 treatment was performed either before (pretreatment) (C), simultaneously with (cotreatment) (D), or after viral infection (posttreatment) (E) for 36 h. Viral protein levels were determined with immunoblotting. Data are the results of three independent experiments (means ± SE). Significant differences compared with the YPD-treated control group are denoted: *P <0.05, **P <0.01, or ***P <0.001.