Regulation of PRRSV infection by mTOR inhibitors and activator in MARC-145 cells. (a) Cells were treated with 1 µM rapamycin, 2 µM PP242 or 2 µM MHY1485 for 24 h, then infected with DsRed-labelled PRRSV (m.o.i. of 1), visualized and imaged with fluorescence microscopy at 36 h post-infection (h p.i.). (b–e) mTOR inhibitors and activator regulate PRRSV infection in a dose- and time-dependent manner in MARC-145 cells. Cells were pretreated with serial dilutions of mTOR inhibitors, rapamycin and PP242, or activator MHY1485 for 12, 24, 36 or 48 h, then infected with DsRed-labelled PRRSV (m.o.i. of 1), and quantified with a SpectraMax i3 (Molecular Devices) at 36 h p.i.; n=3; a, b and c indicate p<0.001, 0.01 and 0.05, respectively, relative to the control. Rapa, Rapamycin; MHY, MHY1485.