Abstract 2069 Pulmonary: Cystic Fibrosis Poster Symposium, Tuesday, 5/4

Although infection is an inciting event, the intense host inflammatory response in the lung largely accounts for the progressive, suppurative pulmonary disease in cystic fibrosis (CF). Neutrophils, the prominent inflammatory cell in the CF lung, attempt to clear bacteria from the airways, yet proteases, like neutrophil elastase (NE), produced by these cells provoke the release of proinflammatory mediators from the respiratory epithelium. This inflammatory response engendered by the neutrophils in the airway could potentially be blocked by inhibiting the action of NE at the airway cell surface. The results of clinical studies examining the effectiveness of systemic or inhaled antiproteases, like alpha1-antitrypsin (A1AT), in patients with CF have generally been discouraging, due to the relative inaccessibility of the respiratory epithelium. It may be possible, however, to deliver the antiprotease to the respiratory epithelium via the polymeric immunoglobulin receptor (pIgR) through the addition of a ligand that permits specific targeting of A1AT to the airway lumen. We have produced fusion proteins consisting of human A1AT linked to a single chain Fv fragment directed against secretory component (SC), the extracellular portion of the pIgR. These bifunctional proteins recognized human SC, and the fusions were effectively transported in a basolateral-to-apical direction across monolayers of cells that express pIgR. Purified human A1AT alone was not transported across receptor-expressing cells. The other component of the fusion protein, human A1AT, was also active as evidenced by its ability to bind and inhibit NE. Moreover, fusion protein (100 pmole) injected into the systemic circulation was transported across human tracheal xenografts, based on immunoblot analyses of the lumenal contents from the xenografts. Thus, both components of the fusion protein were functional, and these fusions will transport a therapeutic payload to the apical surface of epithelia both in vitro and in vivo. Similar bifunctional proteins could potentially be used to specifically deliver other biologically relevant agents to the respiratory epithelial surface in CF patients.

National Institutes of Health DK48996, HL60293, and P30DK27651

Drs. Davis and Ferkol hold equity in Copernicus Pharmaceuticals, a small biotechnology firm in Cleveland, Ohio, that has licensed this technology from Case Western Reserve University.