Summary The abuse of stimulants such as methamphetamine (METH) exacerbates the deleterious effects of HIV infection. Here, we will carry out single nucleus RNA-Seq with the goal of identifying cell types and cell states that are pivotal in the effects of HIV and chronic methamphetamine (METH) self-administration on key brain regions relevant to the effects of persistent HIV infection and METH use disorder in HIV transgenic (Tg) rats, which harbor a non-replicating HIV-1 transgene and express chronic low-levels of multiple HIV-1 proteins. The occasional but limited use of a drug is clinically distinct from escalated drug use, which is characterized by the emergence of chronic compulsive drug-seeking and taking. Thus, we will use an established, state-of-the-art paradigm of voluntary intravenous drug self-administration under long access (LgA) conditions that leads to escalated (compulsive) METH intake in comparison to self-administration under short access (ShA) conditions, which leads to a moderate and stable pattern of METH intake. The paradigm of escalated drug intake under LgA conditions is highly relevant to the human substance use disorder (SUD) as it models all 7 of the criteria for drug addiction in the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV and 7 of the 11 criteria in the DSM-V. We showed that HIV Tg rats self-administering METH in this paradigm display increased compulsivity, neuroinflammation, and neural injury. The project will address the following vexing question about persistent HIV infection in the CNS: what are the cell types and cell states that drive neuroinflammation, neurodegeneration, and compulsive METH abuse in the setting of HIV that can reveal the pathogenic mechanisms behind neuroHIV disease progression, virus expression and persistence? The overarching hypothesis behind the present project is that the exploration of the gene regulatory network at the single cell level will elucidate key mechanisms that underlie the effects of HIV and METH abuse and their detrimental interactions on neuroHIV disease progression, virus expression, and virus persistence and will indicate novel therapeutic targets for neuroinflammation, neurodegeneration, and compulsivity to take METH. To test this hypothesis, we will use a validated systems biology strategy for the reconstruction and interrogation of genome-wide gene regulatory networks to identify the gene network dysregulations associated with the effects of HIV, compulsive METH use, and their interactions at single cell resolution gene profiling by single nucleus RNA-Seq. Overall, this collaborative interdisciplinary proposal integrating single cell level transcriptomics, state-of-the-art behavior methods in HIV Tg and wild-type rats, and computational strategies is expected to identify novel mechanistic hypotheses that may lead to transformative new therapeutic concepts for substance use disorder (SUD) in the HIV setting, and will establish key resources for the neuroHIV field to be made publicly available through the SCORCH data coordination center.

Public Health Relevance The molecular mechanisms responsible for neuropsychological impairment in HIV patients are not easily inferred with conventional high-throughput analysis methods. To investigate the molecular mechanisms behind the interactions of HIV and methamphetamine (METH), this interdisciplinary project will profile gene expression at the single cell level in key brain regions relevant to the effects of persistent HIV infection and substance use disorder (SUD) in a small animal model of neuroHIV in a behavioral paradigm of voluntary intravenous METH self-administration. We will bring to bear computational methods to elucidate the genes (master regulator genes) driving the altered gene expression, which will provide a framework for new testable hypotheses on the mechanisms underlying the neuropathogenesis of the increased neuroinflammation, neurodegeneration and compulsivity to take METH in the context of METH abuse that can be targeted therapeutically to improve neuropsychological functioning in people with HIV.