Overexpression of SOCS1 decreases the antiviral effect of IFN-γ and tyrosine phosphorylation of STAT1 during MHV-68 infection in NIH3T3 fibroblasts.

<p>NIH3T3 cells were transfected with an expression plasmid encoding SOCS1 (pSOCS1) or control (pcDNA3.1). (A) At 48 hours after transfection, the cells were pre-treated with IFN-γ (10 U/mL) for 12 hours, and were then infected with MHV-68 at MOI = 10. At the indicated times post infection, the viral titer was measured by plaque assay. *<i>p</i> < 0.05, **<i>p</i> < 0.01, ***<i>p</i><0.001, pSOCS1+IFN-γ <i>vs</i>. pcDNA3.1+IFN-γ. In parallel, western blotting was performed to assess the SOCS1 expression levels in cells without IFN-γ treatment. (B) RT-qPCR was used to detect the viral ORF50 mRNA expression at 13 hpi. Data are expressed as values relative to the MHV-68 infected, pcDNA3.1 transfected cells without IFN-γ treatment. *<i>p</i> < 0.05, ***<i>p</i> < 0.001. (C) Cells were infected with MHV-68 for the indicated times, with the last hour of infection being in the presence of IFN-γ (10 U/mL) or not. Proteins were extracted, and western blotting was performed to evaluate the tyrosine phosphorylation level of STAT1. Results are representative of three independent experiments and are expressed as mean ± S.E.M.