MX1 and infection: In the current study, the upregulation of STAT1, IFNAR1, and MX1 at the transcriptome level in addition to the upregulation of both IFNAR1 and MX1 at the proteome level on day 5 after viral challenge suggests the possibility of commencement of type I IFN antiviral response at a late time point after viral exposure and the contribution of MX1 to the absence of viral replication seen with restrictive infection in SARS-CoV-2-challenged human macrophages (38).