Enhanced non-inflammasome mediated immune responses by mannosylated zwitterionic-based cationic liposomes for HIV DNA vaccines.

Human immunodeficiency virus (HIV) DNA vaccine can induce cellular and humoral immunity. A safe and effective HIV DNA vaccine is urgent need to prevent the spread of acquired immune deficiency syndrome (AIDS). The major drawback of DNA vaccines is the low immunogenicity, which is caused by the poor delivery to antigen presenting cells and insufficient antigen expression. Sparked by the capability of endosomal/lysosomal escape of the zwitterionic lipid distearoyl phosphoethanol-amine-polycarboxybetaine (DSPE-PCB), we attempted to develop a zwitterionic-based cationic liposome with enhanced immunogenicity of DNA vaccines. The mannosylated zwitterionic-based cationic liposome (man-ZCL) was constructed as a DNA vaccine adjuvant for HIV vaccination. Man-ZCL could complex with DNA antigens to form a tight structure and protect them from nuclei enzyme degradation. Benefited from the capability of the specific mannose receptor mediated antigen processing cells targeting and enhanced endosomal/lysosomal escape, the man-ZCL lipoplexes were supposed to promote antigen presentation and the immunogenicity of DNA vaccines. In vitro and in vivo results revealed that man-ZCL lipoplexes showed enhanced anti-HIV immune responses and lower toxicity compared with CpG/DNA and Lipo2k/DNA, and triggered a Th1/Th2 mixed immunity. An antigen-depot effect was observed in the administration site, and this resulted in enhanced retention of DNA antigens in draining lymph nodes. Most importantly, the man-ZCL could assist to activate T cells through a non-inflammasome pathway. These findings suggested that the man-ZCL could be potentially applied as a safe and efficient DNA adjuvant for HIV vaccines.