INCREASED CONTACT TIME IMPROVES ADENOVINUS-MEDIATED CFTR GENE-TRANSFER TO NASAL EPITHELIUM OF CF MICE

Multiple dosing with recombinant adenoviral vectors containing the cys tic fibrosis transmembrane conductance regulator (CFTR) cDNA to the na sal mucosa of cystic fibrosis (CF) transgenic mice reportedly results in only partial correction of the CF defect in chloride (Cl-) secretio n without normalizing sodium (Na+) hyperabsorption, perhaps indicating inefficient gene transfer into the nasal airway epithelium in vivo In this study, we have examined whether optimizing vector administration such as contact time could improve gene transfer efficiency, Changes in basal nasal potential difference (PID), and in PD (Delta PD) follow ing addition of amiloride and subsequent removal of Cl- from the lumin al perfusate were assayed, As reported previously, the basal nasal PD was significantly more negative in CF mice (-24.9 +/- 2.1 mV) than in normal mice (-6.3 +/- 1.2 mV), Normal mouse nasal mucosa exhibited a l arge hyperpolarization in response to low Cl- substitution (Delta PD o f 8.5 +/- 1.9 mV), whereas the nasal mucosa of the CF mouse depolarize d in response to this treatment, No correction of either the Cl- or Na + transport defects were observed when 5 x 10(9) IU of Ad2/CFTR-5 were administered to the nasal passage of CF mice over a period of 5-20 mi n, However, when CF mice were perfused over a period of 60 min with th e same dose of vector, a significant response (Delta PD of 5.9 +/- 1.1 mV) to low Cl- substitution was detected 2 days later. In these mice, the basal nasal PD (-10.5 +/- 1.4 mV) and the response to amiloride w ere also reduced, indicating a partial correction of the Na+ transport defect, Expression of functional CFTR activity was transient with no measurable Delta PD signals observed by day 7 post-treatment, These re sults suggest that prolonging the contact between an adenoviral vector and the respiratory epithelium enhances the efficiency of gene transf er and can result in improved correction of the CF Na+ and Cl- ion tra nsport defects, Therefore, strategies that improve internalization of viral vectors and that prolong their contact time with target cells ma y result in the improved clinical efficacy of such vectors.