The cystic fibrosis (CF) transmembrane conductance regulator has been localized to both submucosal glands and surface epithelium, suggesting that both glandular and surface epithelium may be important targets for gene therapy. To determine the distribution and efficiency of recombinant adenovirus-mediated gene transfer to human airway submucosal glands, an in vivo model was developed by heterotopically transplanting human bronchial segments from both normal and CF lung tissue into severe combined immunodeficient mice. A serotype 5 E1-deleted recombinant adenovirus containing a lacZ reporter gene driven by the cytomegalovirus promoter (H5.010CMVlacZ) was used to infect the xenografts. Transgene expression was correlated with three factors: 1) viral titer, 2) penetration of microspheres, and 3) dwell time of the viral instillate. At viral titers ranging from 10(8) to 10(11) plaque forming units/ml, expression of the lacZ gene was observed in a subpopulation of epithelial cells within approximately 40% of submucosal glands, with more efficient gene transfer to the ducts than the secretory tubules. Within individual glands, gene transfer varied from < 1% to approximately 20% of submucosal cells, including duct, mucous, and serous cells. Adenovirus-sized fluorescent microspheres were found to penetrate only some of the submucosal glands, suggesting that the gene transfer efficiency to submucosal tubules is due to limited viral particle penetration rather than tropism. Gene transfer to surface epithelial cells was inefficient. However, the percentage of transduced surface epithelial cells increased from < 1% to 5-10% as the dwell time of viral solution was increased from 5 min to 1 h, indicating that the time allowed for virus binding and entry is important for gene transfer efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)