The proposal describes a research program which will examine the biological effects of human immunodeficiency virus type 1 (HIV-1) on neuronal cells, while providing fundamental training in virology and neurobiology which will lead to an independent research career in neurovirology. The AIDS Dementia Complex (ADC) is the most common CNS manifestation of HIV-1 infection. Neuropathological studies indicate that macrophages, rather than neurons, are the major site of productive infection in the CNS, suggesting indirect effects of infection on neuronal cells. Potential mechanisms include HIV-1 proteins produced and released by infected cells, as well as macrophage secretion products, that could effect neuronal cell function. A likely candidate mediator is the HIV-1 regulatory protein, tat (trans-activator or transcription) which is known to be released by some infected cells and can effect cell function when applied to uninfected lymphocytes. In preliminary studies we have shown that tat also induces morphological changes in primary brain cell cultures, and may provide a link between HIV-1 infection and neuronal cell dysfunction. Our hypothesis is that HIV-1 gene products and cellular products produced by infected macrophages within the CNS can affect neural cell function, and play a role in the pathogenesis of ADC. During Phase I of this program we will examine the effect of tat on primary rat brain cultures and transformed human neuronal cell lines. We will investigate the ability of tat to affect neural cell gene expression using transformed human neural cell lines. In addition, we will utilize a mixed cell co- culture system of primary rat brain cells and human monocyte-derived macrophages to study directly the interaction of products of HIV-infected macrophages with neuronal cells. In Phase II, we will employ the techniques and models developed in Phase II to examine the effects of other accessory HIV-1 gene products on neural cell functions. We will utilize primary rat brain cells and transformed neural cell lines to examine the effects of these gene products on our neural cell growth, morphology, and neural specific gene expression, as well as electrical activity. These studies utilizing our primary brain cell/macrophage co-cultivation system and transformed cell lines should aid in further understanding HIV-1/neural cell interactions, and help clarify the mechanism(s) of HIV-1 induction of CNS dysfunction.