TRANSDUCTION BY ADENOASSOCIATED VIRUS VECTORS IN THE RABBIT AIRWAY - EFFICIENCY, PERSISTENCE, AND READMINISTRATION

The ability of recombinant adeno-associated virus (AVV) vectors to int egrate into the host genome and to transduce nondividing cells makes t hem attractive as vehicles for gene delivery. In this study, we assess ed the ability of several AAV vectors to transduce airway cells in rab bits by measuring marker gene expression. AAV vectors that transferred either a beta-galactosidase (beta-gal) or a human placental alkaline phosphatase (AP) gene were delivered to one lobe of the rabbit lung by use of a balloon catheter placed under fluoroscopic guidance, We obse rved vector-encoded beta-gal or AP staining almost exclusively in the epithelial and smooth muscle tells in the bronchus at the region of ba lloon placement, The overall efficiency of transduction in the balloon -treated bronchial epithelium was low but reached 20% in some areas. T he majority of the staining was in ciliated cells but was also observe d in basal cells and airway smooth muscle cells, We observed an 80-fol d decrease in marker-positive epithelial cells during the 60-day perio d after vector infusion, whereas the number of marker-positive smooth muscle cells stayed constant. Although treatment with the topoisomeras e inhibitor etoposide dramatically enhanced AAV transduction in primar y airway epithelial cells in culture, treatment of rabbits did not imp rove transduction rates in the airway, Vector readministration failed to produce additional transduction events, which correlated with the a ppearance of neutralizing antibodies. These results indicate that both readministration and immune modulation will be required in the use of AAV vectors for gene therapy to the airway epithelium.