Correction of the Apical Membrane Chloride Permeability Defect in Polarized Cystic Fibrosis Airway Epithelia Following Retroviral-Mediated Gene Transfer

We are studying the introduction and expression of the normal cystic fibrosis transmembrane conductance regulator (CFTR) cDNA into cultured human airway epithelial cells as a model for gene therapy of cystic fibrosis. In this paper, we show that the chloride transport defect at the apical membrane is corrected in vitro in differentiated ion-transporting CF airway epithelial cells that exhibit polarized properties similar to those found in vivo. Using a retroviral vector containing a copy of the normal CFTR cDNA, we infected cultures of proliferating, cystic fibrosis CFT1 cells and found that correction was maintained following differentiation into a polarized epithelial sheet. At least partial correction of the Cl¯ transport defect was preserved in CFT1 cells for periods of up to 6 months without selection for maintenance of the retroviral provirus. These results suggest that it may be feasible to target proliferating cells in the lung using retroviral vectors for treatment of CF lung disease. Gene therapy of cystic fibrosis lung disease is likely to require in vivo delivery of the genetic vector to the epithelia lining the lumen of the lung. Phenotypic correction of the chloride transport defect will require that expression of a normal CFTR be targeted to the apical membrane of chloride-transporting cells. The current study describes a model in vitro system utilizing airway epithelial cells that exhibit polarized properties similar to those found in vivo. The results are encouraging in that the phenotypic correction after retroviral-mediated gene transfer into proliferating cells is maintained after the cells are induced to differentiate into a polarized epithelial sheet.