Influenza A virus inhibits sodium arsenite-induced SG formation at later times post-infection by an NS1-independent mechanism.

<p>(A and B). SG formation was analysed using immunofluorescent staining of A549 cells infected with the wild type (PR8) and the indicated NS1-mutant influenza A viruses treated with sodium arsenite (As) at 18 hours post-infection (hpi). Virus-infected cells were identified by antibody staining for NP (green) and SGs were visualized using staining for TIA-1 (red). In panel (B) nuclei were stained with DAPI (blue). Scale bars represent 20 µm. (C) Virus and arsenite-induced SG formation was quantified in A549 cells infected with WT PR8 virus at 6, 12, 18 and 24 hours post-infection (hpi). (D) Same quantification as in (C) was done in cells infected with PR8 NS1 N15 virus. (E) SG formation at 18 hpi was compared in mock-infected cells and cells infected with recombinant PR8 viruses with the indicated NS1 mutations. (F) Autoradiogram of the whole cell lysates of mock and PR8 virus-infected A549 cells. At 6 or 16 hpi cells were either left untreated (-) or treated with sodium arsenite (+As) for 1 hour and then immediately pulse-labelled with [³⁵S]methionine-[³⁵S]cysteine for 30 min. (G) Viral NP and HA translation rates post-arsenite treatment are compared between 6 and 16 hpi. Band intensities after arsenite treatment from (F) were normalized to untreated sample band intensities.