IFIT1 and infection: We and others have described a WNV mutant with a site-specific substitution in the NS5 gene (WNV-E218A) that abolishes 2′-O-methyltransferase activity [29] and attenuates infection in wild type mice and cells [14]; replication of WNV-E218A in primary macrophages, however, was rescued in the absence of IFNAR or Ifit1 [14].