Influence of membrane-active peptides on lipospermine/DNA complex mediated gene transfer

To explore whether endosomal release presents a major barrier to lipospermine-mediated gene delivery, acidic membrane-active peptides derived from influenza virus or artificial sequences were incorporated into DNA/dioctadecylamidoglycylspermine (= Transfectam) complexes. Depending on the cell line used, gene expression levels are approximately 3-30-fold higher than those obtained by applying DNA complexed to optimal amounts of Transfectam alone. In addition, gene transfer efficiency of DNA complexes with lower amounts of Transfectam (1.5-2 charge equiv) is increased by a factor of up to 1000 by peptides INF6 (influenza virus derived sequence) and INF10 (artificial sequence). The helper lipids 1,2-dioleoylphosphatidylethanolamine, egg phosphatidylethanolamine, and 1,2-dioleoyl-racglycerol also can enhance the gene transfer. Thus, endosomal escape seems to be only a moderate barrier for optimized, positively charged DNA/Transfectam complexes, but a substantial bottleneck for less positively charged complexes.