Fig. 6. Compounds 9 and 12 inhibited PRRSV at multiple stages of its replication cycle. Marc-145 cells were infected with the PRRSV GD-XH strain at 0.5 or 0.05 MOI. The infected cells were cultured in the presence or absence of 9 or 12 and collected at the indicated time-points post infection to determine viral NSP9 mRNA level by RT-PCR. Cellular GAPDH mRNA was used as a loading control and DMSO sample (set as 1) was used as an uninfected control. (A) Different 9 or 12 treatment schemes. (B) Compound treatment during PRRSV binding. (C) Compound treatment during PRRSV internalization. (D) Compound treatment during PRRSV RNA replication. (E) Compound treatment during PRRSV release. For (B) and (C), 0.5 MOI PRRSV were used to infect cells. For (D) and (E), 0.05 MOI PRRSV were used to infect cells. Statistical significances are denoted by *P < 0.05, **P < 0.01, and ***P < 0.001.