Adenoviral-mediated gene transfer to fetal pulmonary epithelia in vitro and in vivo.

Abstract

Vector-mediated gene transfer offers a direct method of correcting genetic pulmonary diseases and might also be used to correct temporary abnormalities associated with ac- quired, nongenetic disorders. Because the fetus or newborn may be a more immune tolerant host for gene transfer using viral vectors, we used replication defective recombinant ade- noviral vectors to test the feasibility of gene transfer to the fetal pulmonary epithelium in vitro and in vivo. Both proximal and distal epithelial cells in cultured fetal lung tissues from rodents and humans diffusely expressed the lacZ transgene 3 d after viral infection. In vivo gene delivery experiments were performed in fetal mice and lambs. Deliv- ery of Ad2/CMV-I8Gal to the amniotic fluid in mice pro- duced intense transgene expression in the fetal epidermis and amniotic membranes, some gastrointestinal expression, but no significant airway epithelial expression. When we introduced the adenoviral vector directly into the trachea of fetal lambs, the lacZ gene was expressed in the tracheal, bronchial, and distal pulmonary epithelial cells 3 d after viral infection. Unexpectedly, reactive hyperplasia and squamous metaplasia were noted in epithelia expressing lacZ in the trachea, but not in the distal lung of fetal lambs. 1 wk after infection, adenovirus-treated fetuses developed inflammatory cell infiltrates in the lung tissue with CD4, CD8, IgM, and granulocyte/macrophage positive immune effector cells. Transgene expression faded coincident with inflammation and serologic evidence of antiadenoviral anti- body production. While these studies document the feasibil- ity of viral-mediated gene transfer in the prenatal lung, they indicate that immunologic responses to El-deleted recombi- nant adenoviruses limit the duration of transgene expres- sion. (