VECTOR-SPECIFIC COMPLEMENTATION PROFILES OF 2 INDEPENDENT PRIMARY DEFECTS IN CYSTIC-FIBROSIS AIRWAYS

Cystic fibrosis (CF) lung disease has been linked to multiple primary defects in airway epithelia caused by a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) gene, These defects include altered Cl- and Na+ permeability as well as intracellular defects in glycoprotein processing, This apparent diversity in CFTR function is r eflected in the complex patterning of CFTR expression in airway epithe lia. Such complexities present challenges in the design of CF gene the rapies that are capable of reconstituting the endogenous patterns of C FTR gene expression in appropriate target cells. Using a human bronchi al xenograft model of the CF airway, me have evaluated the efficacy of recombinant adenoviral and cationic liposome-mediated gene transfer t o correct Cl- permeability and mucous sulfation defects found in CF lu ng disease. Results from these studies demonstrated a clear vector-spe cific complementation profile for these two defects that was dependent on the type of cell transduced and the level of transgene expression. Single-dose administration of recombinant adenovirus effectively tran sduced high levels of CFTR transgene expression in 11 +/- 1% of epithe lial cells and was capable of correcting cAMP-induced changes in Cl- p ermeability to 91 +/- 14% that seen in non-CF airways. However, this l evel of transgene expression was incapable of reversing defects in muc ous sulfation due to the lack of efficient targeting to goblet cells. In contrast, cationic liposome-mediated delivery of CFTR encoding plas mids to CF airways achieved extremely low levels of transgene expressi on with insignificant correction (7.4 +/- 2.4%) of cAMP-induced Cl- pe rmeability, This low level of transgene expression, however, efficient ly reduced mucous sulfation to levels seen in non-CF airways. Differen ces in the complementation profiles of these two vectors in correcting Cl- permeability and mucous sulfation defects mirror the ability of r ecombinant adenovirus and liposomes to reconstitute only certain featu res of the endogenous distribution and abundance of CFTR protein expre ssion, Such findings suggest that the level of intracellular CFTR requ ired to facilitate proper glycoprotein processing may be much lower th an that needed to mediate bulk Cl- flow across the airway epithelium. In summary, these data present the first example by which two differen t vector systems can efficiently complement independent primary defect s associated with a single dysfunctional gene.