The goal of this study is to obtain training and expertise in the molecular biology of retroviruses with the eventual application of such experience to the study of the pathogenesis of feline immunodeficiency virus (FIV). Phase I of this plan is devoted to learning the various techniques and approaches used in molecular virology while studying avian retroviruses. During this initial phase, experience will be obtained in tissue culture as well as DNA, RNA, and protein manipulations. This phase will focus on retrofection, or the ability of retroviral particles to transmit desired phenotypes to recipient cells by infection, and on heterologous recombination which is recombination between retroviral and non-retroviral sequences. Part of this research will be used to fulfill thesis requirements for a Ph.D. degree in Microbiology. Phase II of this program will involve application Of the molecular approaches and techniques learned in Phase I to the study of FIV tropism and pathogenesis. FIV is a recently discovered lentivirus that causes immunodeficiency disease in cats. It is also a good animal model for AIDS. Molecular clones of FIV will be obtained directly from cat tissues and characterized in vitro during Phase II. Future experiments in cats will evolve from these studies and will be the focus of future grant applications. The studies in Phases I and II will be carried out under the supervision of well-established individuals in the field of molecular retrovirology.