685. Epithelium-Specific Gene Therapy Vector Protects Cftr Knockout Mice from Acute Lung Infection

Development of safe and effective vectors remains a major challenge for lung gene therapy. We developed a helper-dependent adenoviral vector for cystic fibrosis (CF) lung gene therapy, using epithelium-specific control elements to drive expression of the CF transmembrane conductance regulator (Cftr) gene. The vector expressed properly localized CFTR in human CF bronchial epithelial cells cultured at an air-liquid interface. Following a single intranasal dose, the vector expressed human CFTR specifically in the airway epithelium of mice, for up to 3 months. Acute inflammation was minimal to moderate. CFTR protein was also detected in the airway epithelium of 2 month-old mice that received one vector dose postnatally. Delivery of the vector to rabbit lung, in an aerosol containing surfactant, yielded strong gene expression (lacZ reporter) specifically in the airway epithelium, including trachea, bronchi, and bronchioles.To test the therapeutic potential of the vector, we challenged adult mice with a clinical strain of the CF-associated pathogen Burkholderia cepacia complex (Bcc). Cftr knockout mice, but not wild-type littermates, challenged with aspirated Bcc developed severe lung histopathology and had high lung bacteria counts. Cftr knockout mice receiving the Cftr gene therapy vector 1 week before Bcc challenge had less severe histopathology, and the number of Bcc in their lungs was reduced to the level seen in wild-type littermates. These results suggest Cftr gene therapy could benefit cystic fibrosis patients by reducing susceptibility to opportunistic pathogens.