Project III, proposes studies to determine the effectiveness and safety of new therapies for treating CF lung disease, and to define when they should be administered. In an initial series of studies, key cell biologic issues relevant to therapy of CF lung disease will be studied. These studies include the following: 1) identification of the cell type(s) within proximal and distal airway epithelia that express the cystic fibrosis transmembrane regulator (CFTR); 2) quantitation of the rates and types of cells that proliferate in proximal and distal airway epithelia of normal and CF lungs; and 3) evaluation of the consequences of over-expression of CFTR on functions of proliferative and differentiated airway epithelia cells. Major efforts will be devoted towards evaluating therapies in a newly developed mouse model of cystic fibrosis. This model was developed by homologous recombinant techniques that disrupted exon 10 of the CFTR gene, and is termed the CFTR(-/-) mouse. A common strategy will characterize all therapeutic trials. Because the mouse has sub-mucosal glands in the nasal but not lower respiratory tract, the effects of treatment modalities in the two regions will be compared. Each therapy will be tested in protocols designed to measure whether the therapy is protective against the development of bacterial lung disease, and in protocols designed to measure the effectiveness of the therapy in CFTR(-/-) mice with established bacterial lung disease. In a first series of experiments, pharmacologic therapies directed at modulating the Na+ and C1- ion transport properties of the CFTR(-/-) mouse airway epithelia will be studied. Aerosolized amiloride, a Na+ channel blocker, and aerosolized UTP, a triphosphate nucleotide, will be studied singly and in combination. In parallel, a series of gene therapy studies will be initiated. In one series of studies transient expression vector systems for treating CF lung disease will be tested. The initial agent for these studies will be the adenoviral gene transfer vector. In another series of experiments, integrative gene transfer vectors will be employed. The recombinant retrovirus will be the first of this type of vector studied. The efficacy of therapies will be quantitated by pulmonary function measurements (respiratory rate, timing indices, 02 saturation), respiratory microbiology, and respiratory tract histology. Safety indices, both general and drug/vector specific, will be studied. The long range goal is to characterize the relative safety and efficacy of various therapies, alone or in combination, and develop strategies to intervene safely and effectively at all stages of CF lung disease.