Infection with a PR8 H1N1 virus encoding an NS1 protein expressing only the first 125 amino acids (PR8 NS1–125) induced significantly higher amounts of IFN-β, IL-6, C-C motif Chemokine ligand 3 (CCL3), macrophage inflammatory protein 1-alpha (MIP-1α), and tumor necrosis factor (TNF) than the parental PR8 virus. Here, TNF is linked to infection.