The respiratory epithelium is a potential site for somatic gene therapy for the common hereditary disorders alpha 1-antitrypsin (alpha 1AT) deficiency and cystic fibrosis. A replication-deficient adenoviral vector (Ad-alpha 1AT) containing an adenovirus major late promoter and a recombinant human alpha 1AT gene was used to infect epithelial cells of the cotton rat respiratory tract in vitro and in vivo. Freshly isolated tracheobronchial epithelial cells infected with Ad-alpha 1AT contained human alpha 1AT messenger RNA transcripts and synthesized and secreted human alpha 1AT. After in vivo intratracheal administration of Ad-alpha 1AT to these rats, human alpha 1AT messenger RNA was observed in the respiratory epithelium, human alpha 1AT was synthesized and secreted by lung tissue, and human alpha 1AT was detected in the epithelial lining fluid for at least 1 week.

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The most common mutation of the cystic fibrosis transmembrane conductance regulator gene, CFTR, associated with the clinical disorder cystic fibrosis (CF) is called "APhe5N," a triple-base deletion resulting in loss of phenylalanine at residue 508 of the predicted 1480-amino acid CFTR CFTR gene expression quantified by limited polymerase chain reaction amplification showed that in normal individuals, CFTR mRNA transcripts are expressed in nasal, tracheal, and bronchial epithelial cells at -1-2 copies per cell, more than 100-fold greater than in pharyngeal epithelium. Importantly, allele-specific hybridization studies demonstrated that the normal and APhe5" CFTR alleles are expressed in the respiratory epithelium in similar amounts.Cystic fibrosis (CF) is a fatal recessive disorder caused by mutations of the CF transmembrane conductance regulator gene, CFTR, whose postulated protein product is a 1480-amino acid membrane protein thought to modulate Clsecretion across the apical membrane of epithelial cells (1-4). The most common mutation of the CFTR gene is called "Afe 508 ," a triple-base deletion resulting in loss of the codon for phenylalanine at residue 508 of the predicted protein sequence found on ;'"70% ofchromosomes containing an abnormal CFTR gene (3, 4). All organs with exocrine glands are affected by abnormalities of the CFTR gene, but the major clinical manifestations are in the respiratory tract, with impacted mucus, chronic infection, and inflammation with subsequent derangements of airways and lung parenchyma (1). It is not known how mutations in the CFTR gene cause the respiratory abnormalities, but it is assumed to be directly related to abnormalities in expression of the CFTR gene in the respiratory epithelium. As an approach to this question, the present study is directed toward quantifying in vivo CFTR gene expression at the mRNA level in respiratory epithelium of normals and individuals with CF. METHODS