A novel low-toxic liposomal adjuvant: Different liposome compositions regulate monocyte activation and viability

Liposomes are nanoparticles consisting of phospholipid-bilayer membranes and aqueous compartments. They can effectively incorporate both hydrophobic and hydrophilic molecules, and therefore have been widely applied as a carrier for gene and drug delivery. Moreover, liposomes are considered as a novel vaccine delivery system, which encapsulate both Antigen (Ag) and immunomodulatory agents, facilitating Ag delivery to specific immune cells in vivo. Till date, liposomal vaccines against various diseases, such as cancer, HIV, Hepatitis B and malaria, have been investigated and found to be safe. However, their immunogenicity remains to be further improved. Although conventional liposomes are usually formulated with neutral and/or negatively charged lipids, many studies indicated that the cationic liposomes with positive surface charge more effectively enhanced Ag-specific immune response and promoted vaccine-induced anti-cancer responses than other liposomes. On the other hand, cationic liposomes at a high concentration significantly induced apoptosis of dendritic cells and suppressed immune response, suggesting the immunotoxic effect. In the present study, we incorporated 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), a neutral lipid into dioleoyl-3-trimethylammoniumpropane (DOTAP), a cationic liposome, and investigate the effect of different liposome formulations on monocyte activation and viability. Our aim is to develop a safe and effective liposomal adjuvant for vaccine delivery.