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

Vector-mediated gene transfer offers a direct method of correcting genetic pulmonary diseases and might also be used to correct temporary abnormalities associated with acquired, 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 adenoviral 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. Delivery of Ad2/CMV-beta Gal to the amniotic fluid in mice produced 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 antibody production. While these studies document the feasibility of viral-mediated gene transfer in the prenatal lung, they indicate that immunologic responses to E1-deleted recombinant adenoviruses limit the duration of transgene expression.