Vascular gene delivery has tremendous promise to serve both as an investigational and as a therapeutic tool. Transfer and expression of specific genes in the vessel wall can be used to identify the roles of these genes in the development or regression of arterial disease. Identification of gene products that prevent the progression of vascular disease or that promote disease regression may lead to the development of powerful gene-based therapies. Vascular gene therapies might eventually be used to prevent and treat atherosclerosis, thrombosis, and vascular graft failure. To date, progress in vascular gene therapy has been hindered by two principle obstacles: 1) an incomplete understanding of vascular pathophysiology; and 2) technical limitations of gene transfer vectors, including low efficiency, brief duration of expression, inflammatory host reactions, and alterations in the arterial phenotype. The broad, long-term goals of this project are to develop improved means of vascular gene delivery that will facilitate the study of vascular pathophysiology and will expedite the development of vascular gene therapy. The specific aims of this proposal are 1) to improve the utility of first-generation adenoviral vectors by genetic modifications that decrease vector immunogenicity and by the adjunctive use of targeted immunosuppression to block immune cell activation that occurs via B7 and/or CD40 ligand signaling (these strategies should substantially prolong recombinant gene expression and decrease the vascular wall inflammation that is associated with infusion of first-generation vectors); 2) to test the ability of adeno-associated virus and vesicular stomatitis virus G protein-pseudotyped murine retroviral vectors to accomplish efficient and durable vascular gene transfer without associated toxicity; 3) to test a gene therapy strategy in which local delivery of hirudin is used to prevent atherosclerosis; and 4) to determine whether targeted immunosuppression that interrupts immune cell signaling through B7 and/or CD40 ligand (interventions that are likely to be used as adjuncts to gene therapy) affects the development of atherosclerosis in established murine and rabbit models. Accomplishment of the proposed aims will open the door to a new generation of powerful and informative arterial gene transfer experiments. These experiments will eventually permit definition of the roles of specific proteins in the development and regression of arterial disease. Application of results of these experiments should lead to the development of rational and specific therapies for human vascular disease.