Fig 2. Newcastle disease virus infection impaired IFN-α-induced STAT1 phosphorylation.

(A) IFN-α-induced phosphorylated STAT1 degradation in NDV-infected A549 and Vero cells. A549 or Vero cells were infected with NDV strains ZJ1 at MOI 3. At indicated time points post infection, A549 and Vero cells were stimulated with 500 U/ml human IFN-α or IFN-γ in 1 ml DMEM at 37°C for 15 min. Uninfected cells were stimulated with IFN as negative controls (IFNα+/infection-). IFN-α-induced phospho-STAT1 was observed (IFNα+/infection+) for reduction in total STAT1 proteins. IFN-γ-induced phospho-STAT1 proteins were not reduced. (B) Phospho-STAT1 in A549 cells transfected with V-expressing plasmids after stimulation with IFN-α. (C) Expression level of STAT1 and phospho-STAT1 decreased in V-expressing Vero cells after IFN-α stimulation. Vero cells were mock transfected with pCI-neo plasmids. Cells on glass coverlips were transfected with pCI-V/ZJ1 plasmids. At 48 h post-transfection, cells were treated with IFN-α for 15 min prior to fixation as in “Material and methods”. V protein was detected by a mixture of anti-serum Pab-V1 and Pab-V2; STAT1 and phosphorylation were determined by anti-STAT1 antibody (ab31369) and anti-phospho-STAT1 antibody (ab30645). Cellular nuclei were stained with DAPI.