RHDNASE - SCIENTIFIC BACKGROUND, MOLECULA R-CLONING AND PRODUCTION

Despite the hopes raised by the first attempts in gene therapy, direct correction of the defect in CFTR protein associated with cystic fibro sis is still beyond clinical reach. Therefore we have to set upon the consequences of the defect. Respiratory distress and progressive lung destruction in cystic fibrosis can be accounted for by infectious exac erbations and the accumulation of viscous purulent secretions in the a irways. For a long time we have known that purulent secretions that ac cumulate in the airways of patients with cystic fibrosis contain large amounts of DNA, a complex macromolecule that contributes mostly to th e viscosity and hinders the mucociliary function. Hence we hypothesize d that enzymatic cleaving of DNA molecules by desoxyribonuclease (DNas e) should reduce the viscosity of sputum and slow or prevent the deter ioration of pulmonary function. Using the techniques of molecular biol ogy and genetic engineering, we identified the gene of human DNase I, which was cloned in mammalian cells to produce large amounts of a glyc osylated protein for therapeutic use. Catalytic amounts of rhDNase gre atly reduce the viscosity of purulent cystic fibrosis sputum transform ing ii within minutes from a nonflowing viscous gel to a flowing liqui d This effect was associated with a decrease in size of DNA fragments in the sputum. Our studies suggested that inhalation of a rhDNase aero sol might be a simple direct approach to reduce the viscosity of purul ent secretions and thereby help patients with cystic fibrosis clear th eir airways and breathe more easily.