ALTERATIONS IN CNS FUNCTION AND DEVELOPMENT IN PEDIATRIC AIDS

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The proposed studies focus on the cellular and molecular bases of alterations in central nervous system (CNS) function and development that occur in pediatric AIDS (HIV-1-associated progressive encephalopathy of childhood). Children infected with the human immunodeficiency virus (HIV) exhibit a variety of neurologic disorders thought to be caused by HIV infection in the CNS. The biological bases for these abnormalities are unknown, but presumably involve changes in CNS neuronal function, structure and development. The ability to understand and treat such problems will be of significant value to the infected children and to society as a whole. Our studies will focus on the possible role of cytokines and HIV coat proteins (e.g., gp- 120, gp- 160, gp-41) in these abnormalities. The cytokines to be tested include IL-1beta, TNF-alpha and IL-6 which are known to be present at elevated levels in the brains or CSF of HIV infected individuals. These cytokines are secreted by macrophages and microglia, the cells in the CNS that harbor the virus. The effects of cytokines and viral proteins will be investigated alone and in combination to determine if their effects are additive or synergistic. Treatment conditions that significantly alter neuronal function function or development will be studied in detail to identify the altered sites and underlying mechanisms at the molecular level. Effects of cytokines and viral proteins will be investigated in cerebellar granule neurons in culture, a favorable developmental model that has been the focus of our studies during the last funding period. Many important morphological and physiological milestones known to occur during the maturation of these neurons in vivo are expressed in culture and thus are accessible for study in vitro. The neurons will be exposed chronically to the cytokines and/or viral proteins via the culture medium. Effects of these factors on the morphological and physiological development of the granule neurons will be investigated using immunohistochemical, electrophysiological and microscopic calcium imaging methods. The granule neurons will be grown in homogeneous neuronal cultures or co-cultured with astrocytes to determine if cytokines and/or viral proteins can directly induce altered granule neuronal function or if the intervention of astrocytes is required. Therapeutic agents will be tested for the ability to ameliorate the effects of th cytokines and/or viral proteins. In addition, granule neurons from transgenic mice overexpressing cytokines and/or viral proteins will be examined for altered function to provide an in vivo correlate of the in vitro studies involving exogenous application of these factor. Results from these studies should provide important information on neuronal and molecular mechanisms that may contribute to the cognitive and developmental problems observed in children infected with HIV.