Adenovirus as gene transfer vector is characterized by high transfection efficiency, high titer,good stability in target cells and low pathogenicity, and has been widely used in gene therapy. Compared to first- and second-generation adenovirus vectors, the third-generation adenovirus vectors have unique advantages for gene therapy because of their low immunogenicity and high capacity. However, the clinical application of the third-generation adenovirus vectors is hampered by the existance of helper contamination and difficulties in their large-scale production