Project Summary There are currently 38 million people living with HIV (PLWH) and due to current advances in combination antiretroviral therapy (cART), PLWH are living longer. However due to the latent viral reservoir, there is currently no cure for HIV as viral rebound arises following cART cessation. Therefore, a great effort has been put into defining this latent reservoir and strategies for eradication. One of these latent reservoirs is the brain, as demonstrated in both human and non-human primate models. Interestingly, brain latent reservoir can reseed peripheral organs following cART cessation. Understanding the role the brain plays in viral rebound and defining which cells contribute to CNS viral escape is critical for a viable cure strategy. Equally important is to define the neuroinflammatory signature under cART and changes following cART cessation to inform therapeutic strategies. In this application using a combinatorial imaging approach, we will define the viral reservoir in the brain after cART cessation in SIV-infected rhesus macaques (Aim 1) and using a multi-modal approach, we will define the neuroinflammatory signature in SIV-infected rhesus macaques following cART cessation (Aim 2). We will use brain tissue from 3 groups of SIV-infected rhesus macaques that are either cART naïve, on cART or following cART cessation to address three fundamental questions: 1) Which cell type(s) contain rebounding virus following cART cessation in the CNS of SIV-infected rhesus macaques? 2) Do these cells containing rebounding virus following cART cessation have replication competent virus? And 3) What is the neuroinflammatory signature associated with viral rebound in the CNS following cART cessation? Collectively our studies will use state-of-the art imaging technologies to better understand the role of the brain as a viral reservoir to inform cure strategies that addresses the unique characteristics of this sanctuary site.