USP18 and viral infectious disease: Most of these genes, including ISG15, ISG20, IFIT3, IFI6, USP18, XAF1, BST-2A, BST-2B, CCL2, DRAM1, FOLR3, IL18BP, and LGALS3BP, are involved in the immune response of the host against viral infection, mainly via IFN-mediated signaling pathways.