Significance AAV vectors have proven effective in transfer of recombinant DNA into cells of the respiratory epithelium, but for application to the lung disease cystic fibrosis safety and efficacy of CFTR gene transfer by the aerosol inhalation route is critical before human clinical trials can be instituted. Objectives Evaluate the safety and efficacy of administration by aerosol inhalation of the vector tgAAVCF, an adeno-associated viral vector carrying normal human CFTR, following a single inhalation treatment, in animals surviving 14 or 90 days after treatment. Following measurement of the inhalation dose delivered to each animal, evaluate safety through hematological, biochemical, radiographic, bronchoscopic and histologic techniques, and evaluate efficacy through analysis of cells and tissues for vector specific DNA. Results Aerosol exposure of tgAAVCF was accomplished in 6 animals along with treatment of 3 vehicle controls. Concurrent flow spirometry provided specific information about the aerosol dose deposited in the lower airway of each animal. Serial studies on both 14 day and 90 day animals were evaluated for evidence of adverse effects, and extensive histologic studies were completed 14 or 90 days after treatment. Lung and extrapulmonary tissues were evaluated both for evidence of any test agent related toxicity and for evidence of gene transfer. These evaluations are ongoing, however will provide the basis for a planned human clinical study. Future Directions The technique of airway microdissection and fluorescent imaging will be used in future studies to evaluate the specific distribution of transgene aerosols and the regional airway expression of recombinant material administered by aerosol inhalation. KEY WORDS aerosol gene transfer, cystic fibrosis, AAV FUNDING Targeted Genetics, Inc.