478. Preinjection of free DiC14-amidine liposome and dexamethasone synergistically enhance the intravenous transfection efficiency of cationic lipid/DNA lipoplex

Cationic lipids represent a safe alternative to viral vectors for gene therapy applications but their use is still limited by a low in vivo gene transfer efficiency. We report here that cationic lipid-mediated intravenous transfection efficiency can be improved by a single preinjection of free diC14-amidine liposomes or of the steroidal anti-inflammatory drug dexamethasone (Dex). This improvement is dose dependent. Surprisingly, the transfection activity of the complex was enhanced by approximately 24 fold when both diC14-amidine free liposomes and Dex were preinjected, at a doses where individually they have no effect. Synergy between diC14-amidine free liposomes and Dex improved also the intravenous transfection efficiency of DOTAP/DNA lipoplex demonstrating that the method is applicable to other lipoplexes. These finding suggest preinjection of diC14-amidine and dexamethasone as a way to improve the gene transfer efficiency and reduce the toxicity of liposomes.