FIG. 3.

NS1 proteins derived from avian influenza viruses have the ability to block IFN-β induction. (A) A549 cells were transfected with pCAGG-NS1, a β-galactosidase expression plasmid, and an IFN-β Luc construct. At 24 h posttransfection, cells were infected with SeV for 16 h. Luciferase activity was measured and normalized to β-galactosidase activity for each transfection to account for differences in translation and transfection efficiencies. NS1 proteins from human viruses are represented with white bars, and NS1 proteins from avian viruses are shown with black bars. (B) The A549 IFN-βLuc reporter cell line was infected with recombinant viruses containing the avian NS gene in a stable human genetic background (A/Victoria/3/75) at an MOI of 5 PFU/cell, and luciferase activity was measured after 8 h. (C) The A549 IFN-βLuc reporter cell line was infected with recombinant viruses containing the avian NS gene in a stable human genetic background (PR8P is the 6 + 2 recombinant of A/PR/8/34 and A/Panama/2007/99) at an MOI of 5 PFU/cell, and luciferase activity was measured after 8 h.