DESCRIPTION (provided by applicant): Nearly one third of HIV-infected individuals develop neurocognitive deficits despite adequate cART and excellent virological control in the blood. This range of neurocognitive deficits is collectively referred to as HIV-1-associated neurocognitive disorders (HAND). Virus may also enter the brain again in the later stages of infection when there is a general immune failure. The ability of the virus to replicate depends on the cell type and its state of activation. Once inside the brain parenchyma, it resides in perivascular macrophages and microglial cells that provide the site of productive replication and evolution for HIV. Recent studies suggest that there is a substantial viral load in the meninges as well where there is a rich collection of macrophages. Within these regions, HIV infects the macrophages/microglia and astrocytes most commonly located in the perivascular regions where they constitute the blood-brain barrier. Perivascular and meningeal macrophages have been shown to be sites of active viral replication in the human brain. Exosomes are membrane-bound vesicles produced by a variety of cells that contain classical membrane marker proteins such as tetraspanins, adhesion proteins and metalloproteinases. They are considered to play an important role in intercellular communication either by target cell uptake or by inducing cell signaling via membrane receptors. In addition to membrane proteins, exosomes carry mRNAs as well as non-coding RNAs, including miRNAs that are thought to affect gene regulation in the target cells. Research by our group and others has shown that HIV-1-infected cells produce exosomes that activate naïve target cells through a dsRNA called TAR. Our long term goal is to understand the role played by exosomes originating from HIV-1 infected cells in regulating host-virus interactions. We hypothesize that unique viral RNA present in the exosomes of infected cells will alter recipient cells impacting regulation of gene expression and establishment of inflammatory response. Our aims include: To characterize the biogenesis and function of exosomes from infected donor cells under cART (Aim I); To characterize exosomes from infected cells treated with inhibitors and their cellular origin (Aim II), and defining the mechanim of TAR effect on TLR modulation and cytokine production in recipient cells. Collectively our data indicates that infected cells under cART still secrete TAR associated exosmes and that these exosomes activate the naïve recipient cells resulting in unwanted proinflammatory signals. These activities will be reversed with use of inhibitors and tested in both an in vitro BBB model and humanized latent model of HIV infection.