Functional genes have been introduced into respiratory epithelial cells in vitro and in vivo by targeting the polymeric immunoglobulin receptor (pIgR). Complexes consisting of the Fab fragment of antibody directed against the extracellular portion of the receptor, secretory component, covalently linked to a polycation, were noncovalently bound to expression plasmids. Intravenous injection of these complexes in rats resulted in significant levels of transgene (P. pyralis luciferase and E. coli lac Z) expression in protein extracts from the liver and lung, achieving maximum values 4 to 8 days after treatment, but not in tissues that fail to express the receptor. Transgene expression decreased to lower levels 12 days after treatment, and in the respiratory tract, it was localized to the surface epithelium of the airways and the submucosal glands. Neither a conjugate prepared with irrelevant Fab antibodies nor a complex prepared with an expression plasmid containing an irrelevant reporter gene produced detectable transgene activity. This complex provided specific targeting of exogenous genes to cells that bear the pIgR, which include cells that may be appropriate targets for the gene therapy of cystic fibrosis (CF). This proposal is directed at determining the feasibility of receptor- mediated gene transfer into the respiratory epithelial cells as a method of gene therapy of CF. We will characterize the properties of the anti- secretory component Fab-based carrier-DNA complexes necessary to achieve maximal transfection efficiency of the respiratory tract, and to determine the efficacy of gene delivery and the level of transgene expression after repeated administrations of the complexes.
The second aim of this project will examine the ability of receptor-mediated endocytosis to deliver cDNA encoding the human CFTR to the airways of mice homozygous for the S489X CF mutation by targeting the pIgR. Transgene expression will be analyzed at both the transcriptional and translational level, and the electrophysiologic properties of various epithelia will be analyzed after transfection to determine if the bioelectric phenotype of these animals was corrected. We will also examine the impact of pulmonary inflammation and Pseudomonas infection on the delivery of reporter genes to the respiratory epithelium of mice via the pIgR. Furthermore, since the murine airway does not necessarily mimic the respiratory tract in humans, we will test ability of an anti-secretory component Fab-based carrier to deliver reporter genes to respiratory epithelial cells in Rhesus monkeys, capitalizing on the similarity of the animal's respiratory tract to the human and on the cellular distribution of pIgR in the airways of a primate. Finally, because treatments of the complexes are likely, the immunologic properties of DNA or DNA-carrier complexes will be examined. Receptor-mediated gene transfer can introduce functional genes into the respiratory epithelium in a manner that is safe, efficient, and selective, ad deserves further consideration as an alternative approach to gene therapy of CF.
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