Pulmonary endothelium is the locus of early structural and functional changes in several acquired forms of lung disease (e.g. environmental and drug-induced interstitial pulmonary fibrosis, adult respiratory distress syndrome) and may have inborn metabolic defects in pulmonary vascular disease of potentially hereditary origin (e.g. primary pulmonary hypertension, thromboembolic disorders). In addition, pulmonary endothelium is in close proximity to virtually all pulmonary cell types and thus may serve as an heterologous source of therapeutic proteins designed to prevent or reverse lung disease. Furthermore, since the pulmonary circulation receives the entire venous return and anatomically is situated upstream from the total systemic circulation, it is ideally located as a vehicle for protein replacement or detoxification therapy for systematic disorders. As a first approach in evaluating these possibilities, we propose to develop a method to deliver and express specific genes in the pulmonary endothelium. We will initially investigate an endothelial-directed ternary complex delivery system that includes an endothelial cell promoter-enhancer expression system. The delivery system will use monoclonal antibodies (to epitopes on murine pulmonary endothelial cells) covalently attached to polylysine. This polylysine antibody conjugate will be complexed with plasmid or viral vector DNA and a modified cholesterol to optimize internalization and expression in cultured endothelium. The vector system will be endowed with regulatory sequences that permit preferred expression in endothelial cells in culture and in vivo. Location of the expressed proteins will be monitored using a reporter gene (lac Z). Functionality in culture will be assessed by using a prokaryote gene (Sh ble) that produces resistance to the cytotoxic agent, bleomycin. Efficacy, specificity and toxicity of the ternary system will be tested first in cultured murine pulmonary endothelial cells, fibroblasts and smooth muscle cells and then in intact mice. Subsequently functional aspects of this gene transfer system will be assessed in vivo with a well established model of pulmonary fibrosis (e.g. bleomycin toxicity) that has the pulmonary endothelium as an essential target. Successful development of this approach might enhance the therapeutic index of valuable therapeutic agents, such a bleomycin, and provide tools for an alternative strategy to deliver important proteins to other parts of the lung or extrapulmonary sites.