FIG 1.

PRRSV infection reduces STAT3 in MARC-145 and PAM cells. (A) OSM treatment of MARC-145 cells inhibits PRRSV replication and has a minimal effect on cell viability. The cells were pretreated with OSM for 24 h before inoculation with PRRSV VR-2385 at a multiplicity of infection (MOI) of 1. The cells were harvested at 24 h postinfection (hpi). The relative percentage of PRRSV RNA levels determined by real-time PCR are shown. Significant differences from the untreated cells are denoted by asterisks (**) for P < 0.01. (B) PRRSV reduces STAT3 phosphorylation in MARC-145 cells upon OSM stimulation. The cells were infected with VR-2385 at an MOI of 1, incubated for 48 h, and treated with OSM for 30 min before harvested for Western blotting (WB) with antibody against STAT3, phosphorylated STAT3 (pSTAT3), and tubulin. The relative levels of pSTAT3 and STAT3 are shown below the images after normalization with tubulin in densitometry analysis. (C) PRRSV reduces the STAT3 protein level in MARC-145 cells but has a minimal effect on the STAT1 protein. The relative levels of STAT3 are shown below the images after normalization with GAPDH. (D) PRRSV reduces STAT3 protein level in PAM cells but has a minimal effect on the STAT1 protein. The cells were infected with VR-2385 at an MOI of 1 and harvested for WB at 16 hpi.