Potentiation of Gene Transfer to the Mouse Lung by Complexes of Adenovirus Vector and Polycations Improves Therapeutic Potential

Abstract

Recombinant adenovirus (Ad) vectors are being considered for in vivo delivery of various therapeutic genes. One limiting factor in the development of Ad-based gene therapy is the low efficiency of gene transfer to target tissues such as vascular endothelium, smooth muscle, and airway epithelium. Complexing Ad vector with various polycations has been shown to enhance transduction of cell lines otherwise resistant to Ad infection in vitro. On the basis of this observation, the activity of Ad/polycation complexes was tested in vivo in the mouse lung. The results indicated that several polycations were capable of enhancing transduction of mouse respiratory epithelium, leading to a 1–2 log increase in levels of transgene expression. Poly-l-lysine (PLL) and DEAE-dextran were examined further and were found to increase Ad-mediated gene transfer without any additional toxicity as assessed histologically or through the measurement of inflammatory cytokines in bronchoalveolar lavages. The two polycations also failed to affect the humoral response against Ad vector and were themselves nonimmunogenic under conditions leading to enhanced gene transfer. Moreover, the ability to use reduced doses of vector complexed with polycations resulted in lower levels of Ad-specific antibodies and, thereby, improved readministration of vector. These results suggest that complexing Ad vectors with polycations has the potential to improve the therapeutic index by increasing transgene expression while reducing unwanted responses associated with high doses of vector. Adenovirus (Ad) vectors are promising candidates for in vivo delivery of various therapeutic genes but their effectiveness is limited by their limited transduction efficiency in target tissues such as airway epithelium. In this study, complexing Ad vector with various polycations was found to give rise to a significant increase in gene transfer to the mouse lung. Enhanced transduction with poly-l-lysine (PLL) or DEAE-dextran was not associated with any added toxicity or change in the humoral response to Ad particles. The two polycations themselves were nonimmunogenic under conditions leading to enhanced gene transfer. Importantly, the ability to use reduced doses of vector complexed with polycations resulted in lower levels of Ad-specific antibodies and, thereby, improved readministration of vector. These results suggest that complexing Ad vectors with polycations has the potential to enhance significantly the potency of this gene transfer vector system.