This contract will support research programs of the laboratory of Tumor Cell Biology aimed at elucidating mechanisms of retroviral pathogenesis, and developing effective treatment and vaccination strategies. Task A covers work principally related to the biology and immunology of retroviruses and to purification of retroviral proteins and proteins with biologic activity. Specifically, the work will include in vitro culture and detection of retroviruses from blood and tissues of infected animals and humans: characterization of novel viruses isolated from animals or humans; provision of titered preparations of animal or human viruses for in vitro experiments; immunologic assessment of the serologic status of animal or human sample donors, and evaluation of virus prevalence in selected populations; provision of highly purified, characterized, and biologically active (where appropriate) proteins from viruses, cells, or conditioned media and from bacterial or mammalian expression systems; and provision of well-characterized monoclonal and polyclonal antibodies. Task B covers work principally related to development of gene therapy approaches. Specifically, the work will include provision of stem cell cultures; assessment of the efficacy, expression and toxicity of inserted genes in vitro; and evaluation of the distribution, expression levels, and longevity of genes introduced in vivo.