AAV vectors have a good safety profi le, and are less immunogenic compared with other viruses, although anti bodies do develop against AAV capsid proteins that can compromise repeat administration. AAV vectors can insert genes at a specifi c site on chromosome 19 . Th e packaging capacity of the virus is limited to 4.7 kb, restricting the size of the transgene that can be used. AAVs are less effi cient in transducing cells than adenoviral vectors. Successful AAV vector gene transfer has been demon strated in multiple lung cell types including lung progenitor cells, in both normal and naphthaleneinduced ALI lungs [20] . AAV serotypes have specifi c tissue tropisms, due to diff erent capsid proteins that bind to specifi c cell membrane receptors. AAV-5 [21] and AVV-6 [22] exhibit enhanced tropism for the pulmonary epi thelium [21, 22] . AAVs can transduce nondividing cells and result in long-lived transgene expression. AAV vectors have been used in clinical trials in cystic fi brosis patients, underlining their safety profi le [23, 24] .