Furthermore, its induction in virus infection can be mediated indirectly by proinflammatory cytokines such as interferon-γ (IFN-γ) [40] and directly, by virus components, for example, an envelope glycoprotein of HIV, gp41, triggers iNOS expression in human astrocytes and murine cortical brain cells in culture [41]. Here, IFNG is linked to viral infectious disease.