Figure 1

Screening protocol for PRRSV inhibitors. A Screening procedure time course. Marc-145 cells were treated with 10 µM compound for 1 h and then infected with PRRSV (0.01 MOI) for 1 h. Cells were washed with PBS and then incubated in medium containing 10 µM compound for another 48 h. B Screening process flowchart. The criteria for passing the primary screen were that the compound had no apparent cytotoxicity and that it reduced CPE by at least 50% compared with that of the positive controls. The criteria for passing the secondary screen were that the compound had to leave cells at least 80% viable and had to inhibit PRRSV (0.01 MOI and 0.1 MOI) by more than 80%. Compounds that passed the tertiary screen inhibited PRRSV in a dose-dependent manner and had a selective index greater than ten. C Each dot represents the percent inhibition of PRRSV (0.01 MOI) achieved with each compound. The dots located above the dotted line indicate 80% or greater inhibition. D IFA of infected cells treated with one of the five designated compounds. PRRSV N-protein is coloured red, and brightfield-imaged cells show CPE. E IC₅₀ and CC₅₀ curves of the 5 designated compounds. The structure of each compound is inset. F SIs of the 5 designated compounds. Selectivity index (SI) = CC₅₀/IC₅₀