IDO1 and viral infectious disease: Several gene groups and key genes important in reducing local viral infection are identified, including complement-related genes C3AR1 and CFB, as well as TLR3, IFNB1 [29,30], genes encoding chemokines for recruiting neutrophils (IL-8), monocytes (CCL2), dendritic cells (CCL20), T cells and NK cells (CCL5, CCL20, CXCL10) [31], and genes involved in modulation of the immune response (IDO1) [32].