GAS6 and Flavivirus Infections: AXL has at least two modes of action to enhance flavivirus infection of cultured cells: (1) its extracellular domain facilitates virus attachment using the GAS6 ligand as a bridge between the host cell and the virus membrane and (2) its intracellular kinase activity boosts viral production by muting type I interferon signaling to reduce the cellular antiviral response [27,29,41].