MX1 and infection: Infection of chicken myotubes with LPAI H2N3 virus resulted in potent induction of IFN-β mRNA at 12 h p.i. (≈685-fold increase), which correlated with the upregulation of the interferon-inducible MDA-5, Mx1, 2′,5′-OAS, and PKR genes (Fig. 6A).