We have recently established a novel model for HIV-1 infection in healthy immunocompetent mice. Mice inoculated i.v. or i.p. with EcoHIV, a chimeric HIV-1 carrying MLV envelope that mediates HIV-1 entry into mouse cells, become persistently infected, with production of antibodies to viral proteins and presence of virus in the spleen, peritoneal macrophages, and PBL. A large proportion of inoculated animals show evidence of early virus infiltration into the brain and elevated expression of genes such as MCP-1, STAT1, and IL-1b, which are associated with inflammation in brain tissue in humans. In contrast, relatively few animals displayed brain lesions indicative of overt brain disease. Thus EcoHIV is neurotropic and neuropathogenic in mice but it does not express HIV-1 gp120 and it appears to cause attenuated, "preclinical" brain disease in mice. HIV-1 gp120 is thought to contribute to neuropathogenesis through interaction with surface receptors on macrophages, astrocytes, and neurons. Preliminary studies indicate that HIV-1 carrying native gp120 induces a wider range of inflammatory molecules in mouse astrocytes in culture than EcoHIV. We hypothesize that expression of selected gp120 segments, such as V3, by EcoHIV will facilitate HIV-1-mediated neuropathogenesis in mice. The exploratory studies proposed here will evaluate this hypothesis in two Aims. In Aim 1, we will construct a series of chimeric EcoHIV with increasingly large HIV-1 gp120 regions around V3, including those responsible for interaction with surface receptors, inserted into MLV Env of EcoHIV. The chimeras will be tested for infectivity in vitro and in vivo and for their ability to induce inflammatory proteins in mouse macrophages and astrocytes in culture compared to EcoHIV. The first such chimera we constructed, EcoHIV-V3, was found to be infectious in vivo. In Aim 2, we will compare selected gp120- expressing chimeras and EcoHIV for induction of neuropathogenesis in mice. We will determine the kinetics of virus infection and neuroinvasion in vivo, the expression of selected molecular markers of HIV-1 neuropathogenesis in the brain, and the development of neuropathology. The proposed studies may help to define the role of HIV-1 gp120 in HIV-1-mediated neuropathogenesis in mice in distinction from contribution of the viral genome lacking gp120. The studies employ an animal model, molecular, and pathological analyses of animal tissues, and molecular virology and recombinant DMA technologies. In the larger public health context, our studies will establish the utility of this animal model of HIV-1 infection in research on HIV-1 pathogenesis, including that in the central nervous system, development of HIV-1 vaccine, and convenient inexpensive testing of antiviral compounds in vivo. [unreadable] [unreadable]