Duration of inhibitory effects on H-PRRSV in MARC-145 cells that stably transduced with Lenti-amiRNAs. Stably transduced MARC-145 cells were generated by recombinant lentiviruses via Blasticidin (8 μg/ml) selection. Images were taken with an inverted fluorescence microscope in bright (upper) or fluorescence (bottom) light of the same field, Magnification 200× (A). MARC-145 cells that were stably transduced with amirGP5-370, amirM-263-M-263 and negative amiRNA were infected with H-PRRSV at 5.0MOI. At 72, 96 and 120 hours post-infection, cell cultures were harvested, respectively, and virus titers were assayed by CCID50 (B).