One of the major consequences of chronic alcohol use in brain is increased inflammation that leads to neurodegeneration with associated cognitive and psychiatric impairments. Neuropsychiatric impairments persist in patients following substance abuse and are associated with poorer treatment outcomes. HCV is also associated with a variety of extrahepatic syndromes, including central nervous system (CNS) damage and neuropsychiatric impairments. However, it is unclear whether such cognitive and mood disturbances are a function of systemic disease, damaged hepatic function, or virus infection of the CNS. Animal models are needed to provide new insights into the molecular mechanisms and pathways affected by co-morbid alcohol dependence and chronic viral infection, and also those which are responsible for the persistence of neuropsychiatric impairments following abstinence and viral clearance. Our overall hypothesis is that HCV patients with co-morbid AUDs are at increased risk of brain damage that contributes to alcohol relapse risk. In humans and across species, our goal is to identify specific mechanisms by which chronic viral infection and alcohol induce abnormalities in immune cell function and contribute to persistent neuropsychiatric impairments. The following specific aims are proposed: 1) Determine the effects of HCV and alcohol use on peripheral T cell response and psychiatric function in veterans with co-morbid HCV and AUDs. Biological specimens and psychiatric data will be derived from those currently being collected for a treatment trial in veterans with HCV and co-morbid AUDs. We will obtain peripheral blood mononuclear cells and evaluate them across time for: i) phenotypic changes in T-cell populations, ii) surface and intracellular accumulation of cytokines, and iii) immunoreactivity to neuroantigens and other antigens. Blood samples will be used to measure key cytokines and chemokines, viral load, and liver enzymes. Rating scales that measure depression, anxiety, and alcohol consumption will also be used. Results from the immunoassays will be analyzed in relation to psychiatric measures, viral load, and alcohol use, as well as in relation to the findings from Aim 2. 2) Investigate the role of chronic alcohol exposure in regulating peripheral and central T-cell responses, CNS immunopathology, and behavioral signs of anxiety, depression, and cognitive impairments in mice infected with lymphocytic choriomeningitis virus (LCMV, clone 13 variant), an established model for HCV infections in humans. Mice will be chronically exposed to and dependent on ethanol administered intragastrically followed by intravenous injection of LCMV (or vehicle) to evaluate the consequences of co-morbidity. Behavioral tests will be conducted following ethanol exposure to assess anxiety, depressive-like behavior, and cognitive function. Blood, brain, and spleen samples will be collected to: i) measure blood ethanol concentrations, liver enzymes, viral titers, and key cytokines and chemokines, ii) evaluate T cell frequencies, including LCMV-specific CD8+ T cells (utilizing tetramer analysis; H-2Ld-restricted NP118), iii) calculate the percentage of CD4+, CD8+, and antigen-specific CD8+ T cells producing key cytokines (e.g., TNF- ), iv) evaluate immunoreactivity to neuroantigens, and v) assess neuroinflammation and neuronal degeneration. Examining the role of alcohol in regulating viral persistence and CNS immunopathology in LCMV-infected mice will lead to a more comprehensive understanding of co-morbid AUDs and HCV and may identify targets for future therapeutic development. If our hypotheses are supported, future studies will test our immunotherapeutic strategy that we have found reduces neuroinflammation and improves cognitive function in mouse models of methamphetamine dependence. Interventions that successfully treat alcohol induced neuropsychiatric impairments have a high likelihood of also reducing relapse rates and improving treatment outcomes.
The prevalence of co-morbid hepatitis C (HCV) and alcohol dependence is extremely high and estimated to be 60-70% for veterans treated in the Veterans Affairs healthcare system. Studies from our and other laboratories show that either HCV or prolonged use of alcohol and other drugs of abuse augment inflammatory responses and result in increased pro-inflammatory activation and impaired psychiatric function. However, the potential synergistic effects of a chronic viral infection and alcohol exposure on CNS immunopathology and behavior are not well defined. Through human studies and the establishment of an animal model of co-morbid viral infection and alcohol dependence, our goal for this translational research project is to identify specific mechanisms by which chronic viral infection and alcohol induce abnormalities in immune cell function and contribute to persistent neuropsychiatric impairments. This information will guide future pre-clinical testing of immunotherapeutic strategies to improve psychiatric function and reduce the risk of alcohol relapse.
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