The NS1 protein of influenza A virus suppresses interferon-regulated activation of antigen-presentation and immune-proteasome pathways

The NS1 protein of influenza virus counters host antiviral defences primarily by antagonizing the type I interferon (IFN) response. Both the N-terminal dsRNA-binding domain and the C-terminal effector domain are required for optimal suppression of host responses during infection. To better understand the regulatory role of the NS1 effector domain, we used an NS1-truncated mutant virus derived from human H1N1 influenza isolate A/Texas/36/91 (Tx/91) and assessed global transcriptional profiles from two independent human lung cell-culture models. Primary human tracheobronchial epithelial (HTBE) cells were washed and infected with 4×10^6 p.f.u. Tx/91 or Tx/91 NS1 : 1–126 viruses per filter (m.o.i. of 20) for 1 h at 37 °C. Three replicate wells were infected for each condition per time point. Allantoic fluid was used for mock treatments. At 9.5 and 25 h p.i., cells were collected and resuspended in TRIzol reagent (Invitrogen) for total RNA extraction. A549 cells were infected with Tx/91 or Tx/91 NS1 : 1–126 viruses at an m.o.i. of 2 for 1 h at 4 °C. Three replicate wells were infected for each condition per time point. Allantoic fluid was used for mock treatments. A549 cells were collected and lysed in solution D (4 M guanidinium thiocyanate, 25 mM sodium citrate, 0.5 % sarcosyl, 0.1 M β-mercaptoethanol) at 12 and 24 h p.i. for total RNA extraction.