MX1 and influenza: For example, functional Mx1 transfection diminished the polymerase activity of influenza virus [19,20], and functional Mx1-carrying mice are highly resistant against pathogenic influenza infection such as pandemic 1918 and lethal human H5N1 [21,22], PR8 [23], and avian H5N2 Ab/Korea/ma81/07 virus [24].