Comparison of two delivery systems efficiency by using polyethylenimine (PEI) for plasmid HPV16E7 DNA transfection into COS-7 cells

DNA vaccines have been widely used to develop immunity against various pathogens including parasites and viruses. The potential of DNA vaccine to induce an effective immune response is related to the expression levels of the encoded protein in eukaryotic cells. Therefore, optimization of plasmid DNA delivery system is a major concern in protein expression in order to make an efficient DNA vaccination. Non-viral vectors such as polymers and cationic peptides have been recently known as efficient gene delivery systems into eukaryotic cells. In this study, transfection efficiency of HPV16E7 gene was evaluated by two non-viral delivery systems in vitro. DNA construct encoding HPV16E7 (pEGFP-E7) was prepared in large scale with high purity. Then, two delivery systems including polymer PEI 25 kDa and polymer-peptide hybrid as PEI600-Tat conjugate were used to compare their efficiency for HPV16E7 DNA transfection in vitro. Our data demonstrated that both delivery systems including PEI 25 kDa and PEI600-Tat are efficient tools for E7 gene transfection. Although the level of transfected COS-7 cells is higher using PEI 25 kDa in comparison with PEI600-Tat. Our study indicated that PEI potency for E7 gene transfection was higher than PEI600-Tat in vitro, but its toxicity was obstacle in vivo. Therefore, with regard to low toxicity of PEI600-Tat delivery system and its potent plasmid DNA delivery, it is critical issue to study its potency as new delivery system in vivo.