Development of novel vaccine system with nanocarrier

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We showed that second dose PEGylated liposome is aggressively transported from marginal zone (MZ) into follicle in spleen when they are injected twice into the same rat with short interval1. We revealed that splenic MZ B cells capture and transport second dose liposomes into follicle in a time after second dose injection-dependent manner. The captured and then transported liposomes were finally taken up by follicular dendritic cell. We tried to apply this unique immune response to be a novel adjuvant system which enhances a specific antibody response against antigen encapsulated in second dose liposomes. Pre-immunization with low dose empty liposome, which triggers the transport of antigen-containing second dose liposomes into follicle, induced both anti-OVA IgM and anti-OVA IgG productions as OVA-containing liposomes, not free OVA, was intravenously injected as a second dose. The produced anti-OVA IgG contained IgG1, IgG2a and IgG2b subclasses. In addition, the high level of anti-OVA IgG lasted over 12 weeks after the immunization. These suggest that pre-stimulation with empty PEGylated liposomes could enhance the specific antibody response against antigen encapsulated in second dose liposomes. We conclude that our active transport methodology can be useful for a novel and alternative vaccine strategy to potentiate specific antibody response.