ROLE OF ALVEOLAR MACROPHAGES IN RAPID ELIMINATION OF ADENOVIRUS VECTORS ADMINISTERED TO THE EPITHELIAL SURFACE OF THE RESPIRATORY-TRACT

To evaluate the hypothesis that innate immune mechanisms play a major role in eliminating adenovirus (Ad) vectors from the lung, the fate of adenoviral genome of an Ad vector was quantified in the first 24 h af ter intratracheal administration of an Ad vector coding for beta-galac tosidase (beta gal) to mice, Southern analysis with an Ad specific pro be showed that 70% of the Ad genome was lost within 24 h, in both immu nocompetent and immunodeficient animals, When alveolar macrophages wer e eliminated by administration of liposomes containing dichloromethyle ne-biphosphanate, subsequent administration of Ad vector was associate d with a 100% +/- 8% increase in lung Ad DNA and 96% +/- 9% rise in be ta gal expression at 24 h compared to central animals, In vitro infect ion of mouse, rat, and human alveolar macrophages with an Ad vector re sulted in 65% loss of vector genome within 24 h, whereas the vector ge nome was stable in lung epithelial cell lines, PCR in situ hybridizati on demonstrated that the Ad vector genome persisted A549 lung epitheli al cell in vitro but not in alveolar macrophages, Finally, alveolar ma crophages recovered from the mouse lung 30 min following intratracheal administration of an Ad vector showed large amounts of vector genome, whereas much less was evident in alveolar macrophages recovered after 24 h, These observations demonstrate that alveolar macrophages play a n important role in elimination of Ad vectors from the lung and sugges t that strategies to transiently suppress this major innate immune def ense system might be rewarding in enhancing the efficiency Ad vectors for lung gene therapy.