Enhanced adjuvantic property of polymerized liposome as compared to a phospholipid liposome

Liposome, although intensively researched as vaccine or drug delivery vehicle, has been of limited use due to the low and unpredictable long-term stability. In order to overcome such problems, polymerized liposome (PL) that could initiate polymerization under very mild reaction condition was examined and compared to a conventional liposome. The polymerizable lipid, 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphorylcholine (DLL), was synthesized according to the literature, and 1,2-distearoyl-sn-glycero-3-phosphorylcholine (DSPC) was used as the conventional lipid counterpart. Polymerization of liposome was as easy and convenient as just shaking in pH 7.4 buffer. The protein encapsulation efficiency of DLL was higher than that of DSPC, and its protein release rate was lower. Immunoglobulin G (IgG) activity examined after intraperitoneal injection of antigen encapsulated by either DLL or DSPC showed that ca. 2 times as much antibody was formed by DLL-encapsulated lysozyme compared with DSPC-encapsulated form. The reasons for the superior adjuvantic properties of DLL and its future application as a drug delivery system are briefly discussed.