Development of an antigen-presenting cell-targeted DNA vaccine against melanoma by mannosylated liposomes

As part of our research involving the targeted delivery of plasmid DNA (pDNA) to antigen-presenting cells (APCs), we developed mannosylated cationic liposomes: N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA)/cholesten-5-yloxy-N-(4-((1-imino-2-D-thiomannosyl-ethyl)amino)butyl)formamide (Man-C4-Chol)/Chol (Man liposomes). In this study, we used melanoma-associated antigen expressing pDNA; pUb-M and Man liposomes to create a novel APC-targeted DNA vaccine against melanoma and examined its potency by measuring the Ub-M mRNA expression in splenic dendritic cells and macrophages, the cytotoxic T lymphocyte (CTL) activity against melanoma B16BL6 cells and the melanoma B16BL6-specific anti-tumor effect after intraperitoneal (i.p.) administration. We verified that Man lipoplex induces significantly higher pUb-M gene transfection into dendritic cells and macrophages than unmodified lipoplex and naked DNA and it also strongly induces CTL activity against melanoma, inhibits its growth and prolongs the survival after tumor challenge compared with unmodified liposomes and the standard method (naked pDNA, intramuscular (i.m.)). These results demonstrate that Man liposomes are a potent APCs-targeted vector that induce strong immunopotency of DNA vaccine against melanoma.