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Background: Nuclease activity present within respiratory tissues contributes to the rapid clearance of injected DNA and therefore may reduce the transfection activity of directly injected transgenes. Most gene transfer technologies transduce or transfect murine tissues more efficiently than corresponding primate tissues. Therefore, it is prudent to assess the utility of novel gene transfer strategies in both rodent and primate models before proceeding with further development., Methods: This study analyzed the effects of ATA (a nuclease inhibitor) on the direct transfection of macaque and murine lung tissue; compared the levels of DNase activity in murine, primate, and human lung fluids; and tested the inhibitory activity of ATA on the DNase activity present in these samples. Fluorescent microspheres were used to detect areas of transfection in lung., Results: Intratracheal administration of a nuclease inhibitor (ATA) with naked DNA (0.5 microg ATA/g body weight) enhanced direct transfection efficacy in macaque lung by over 86-fold and by over 54-fold in mouse lung. Hematoxylin and eosin staining showed no apparent tissue toxicity. Moreover, macaque, human, and mouse lung fluids were found to possess similar levels of DNase activity and this activity was inhibited by similar concentrations of ATA. The authors also successfully pioneered the use of carboxylate-modified microsphere tracers to identify areas of transfection and/or treatment., Conclusion: This work provides evidence that using direct nuclease inhibitors will enhance lung transfection and that nuclease activity is present in all lung fluids tested, which can be inhibited by the use of direct DNase inhibitors., (Copyright 2002 John Wiley & Sons, Ltd.)

In developing gene therapy for cystic fibrosis (CF) airways disease, a transgene encoding a partially deleted CF transmembrane conductance regulator (CFTR) Cl- channel could be of value for vectors such as adeno-associated virus that have a limited packaging capacity. Earlier studies in heterologous cells indicated that the CFTR R (regulatory) domain is predominantly random coil and that parts of the R domain can be deleted without abolishing channel function. Therefore, we designed a series of CFTR variants with shortened R domains (between residues 708 and 835) and expressed them in well-differentiated cultures of CF airway epithelia. All of the variants showed normal targeting to the apical membrane, and for the constructs we tested, biosynthesis was like wild type. Moreover, all constructs generated transepithelial Cl- current in CF epithelia. Comparison of the Cl- transport suggested that the length of the R domain, the presence of phosphorylation sites, and other factors contribute to channel activity. A variant deleting residues 708-759 complemented CF airway epithelia to the same extent as wild-type CFTR and showed no current in the absence of cAMP stimulation. In addition, expression in nasal mucosa of CF mice corrected the Cl- transport defect. These data provide insight into the structure and function of the R domain and identify regions that can be deleted with retention of function. Thus they suggest a strategy for shortening the transgene used in CF gene therapy.