ISG15 and infection: Among the selected ISGs, Mx1, Mx2, OAS2, OASL, IFIT1, IFIT2, IFIT3, IFITM1, TRIM22, and ISG15 were highly up-regulated (130 to 1,300-fold change upon infection with wild-type Cal [NS1_low-PAX_high] virus), most of which are known to inhibit influenza virus infection and/or replication (Fig 5B).