Antiretroviral therapy (ART) has led to significant decrease in incidence of the most severe forms of HIV associated neurocognitive disorder (HAND); however, the level of less severe forms of cognitive, behavioral and motor dysfunction have been reported to persist in 30-50% of patients. HIV-associated neuropathology has shifted from a rapidly progressing encephalitic condition to a prolonged neurodegenerative disease with pathologic features including astrogliosis, microgliosis and dendritic damage. However, white matter changes remain a common feature of HAND in the pre- and post-ART era. Intriguingly, a recent transcriptome analysis has shown that genes associated with oligodendrocyte differentiation and myelin production are down regulated in untreated patients with HAND as well as in patients with HAND treated with ART. These findings indicate that HIV and ART may disrupt myelin development and maintenance. However, the effects of ART compounds alone or in combination with HIV-infected cells on the oligodendrocytes and their precursor cells have not been studied. We hypothesize, that ART compounds alter oligodendrocyte differentiation, function, and survival, contributing to the persistence of HAND in the post-ART era. To this end, we have demonstrated that 2 antiretroviral compounds (ARV), one nucleoside reverse transcriptase inhibitor (NRTI), AZT, and one protease inhibitor (PI), ritonavir, alter oligodendrocyte morphology and decrease oligodendrocyte survival in a dose dependent manner in vitro. Further, at subtoxic concentrations, both AZT and ritonavir disrupt maturation of oligodendrocyte precursors (OPCs) in vitro induce oxidative damage and induce the endogenous antioxidant response as indicated by upregulation of heme oxygenase 1 (HO1). Oxidative stress has been shown to alter oligodendrocyte survival and differentiation in both perinatal white matter injury and Multiple Sclerosis models. A recent study has shown that a fumaric acid ester (FAE) with antioxidant properties is efficacious in MS clinical trials. Given th presence of oxidative stress in the CNS of patients with HAND, including those on ART we propose to test the hypothesis that HIV-infected macrophages (HIVMDM) and ARV compounds induce oxidative stress altering oligodendrocyte differentiation, function, and survival in vitro ad in vivo. To test this we will: a) determine the contribution of HIVMDM and ARVs to the development and maintenance of mature oligodendrocytes, b) determine the role of HIVMDM- and ARV-induced oxidative stress in blocking oligodendrocyte differentiation and myelination, c) determine the effect of ARV-induced oxidative stress on oligodendrocytes in vivo, and d) determine the state of oligodendrocyte damage and stress in the context of lentiviral-infection and ART in primates.