LIMITED ENTRY OF ADENOVIRUS VECTORS INTO WELL-DIFFERENTIATED AIRWAY EPITHELIUM IS RESPONSIBLE FOR INEFFICIENT GENE-TRANSFER

Investigations of the efficiency and safety of human adenovirus vector (AdV)-mediated gene transfer in the airways of patients with cystic f ibrosis (CF) in vivo have demonstrated little success in correcting th e CF bioelectrical functional defect, reflecting the inefficiency of A dV-mediated gene transfer to the epithelial cells that line the airway luminal surface. In this study, we demonstrate that low AdV-mediated gene transfer efficiency to well-differentiated (WD) cultured airway e pithelial cells is due to three distinct steps in the apical membrane of the airway epithelial cells: (i) the absence of specific adenovirus fiber-knob protein attachment receptors; (ii) the absence of alpha(v) beta(3/5) integrins, reported to partially mediate the internalizatio n of AdV into the cell cytoplasm; and (iii) the low rate of apical pla sma membrane uptake pathways of WD airway epithelial cells. Attempts t o increase gene transfer efficiency by increasing nonspecific attachme nt of AdV were unsuccessful, reflecting the inability of the attached vector to enter (penetrate) WD cells via nonspecific entry paths. Stra tegies to improve the efficiency of AdV for the treatment of CF lung d isease will require methods to increase the attachment of AdV to and p romote its internalization into the WD respiratory epithelium.