MX1 and cytomegalovirus infection: To gain further insight into the role of these genes during HCMV infection, we measured virus production in HCMV-infected HFFs after siRNA-mediated depletion of Mx1 or IFIT1—the latter having been shown to exert antiviral activity against HCMV only in fetal astrocytes upon lentiviral overexpression30.