MX1 and cytomegalovirus infection: However, as with infection of MyD88-expressing cells, we observed that the UL88-STOP-mCh HCMV infection, in which MyD88 levels are higher, actually downregulated a number of antiviral ISGs, including IFITM1, IFITM2, IFITM3, MX1, and IFI16 (the nuclear sensor that plays a role in sensing of HCMV) (Fig. 8E and F).