B型肝炎ウイルス表面抗原ナノ粒子を用いる生体内ピンポイント遺伝子導入法の開発

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We previously succeeded overproduction of the HBV env L particles in yeast cells (up to 42% of the total soluble protein). In the present studies, the L particles have been purified, characterized, and examined for the applicability to the gene delivery system. By AFM observation and sedimentation equilibrium, about 110 molecules of L proteins were found to be assembled into a lipid vesicle to form a spherical particle (-500 nm in diameter). To examine the L particles as gene carriers, a mammalian expression plasmid for GFP (green fluorescence protein) was incorporated into L particles by electroporation. The L particles containing the plasmid were added to the culture medium of human hepatoma HepG2 cells. After two days, more than 90% of the HepG2 cells expressed GFP, while the control non-human liver cells did not. Then, the nude mice transplanted with human hepatoma HuH-7 cells and human colon cancer WiDr cells were injected intraperitoneaUy with the L particles containing the plasmid. Two weeks later, the fluorescence was observed specifically in the HuH-7 cells, but neither in the WiDr cells nor in the liver, spleen, kidney, and intestine of the mice. Because the L particle is an empty vesicle containing no viral DNA, it can be used as a safe and efficient vector for human liver-specific gene transfer. We are now evaluating the effectiveness of L particles as the novel drug delivery system, together with the genetically engineered L particles that can be applied for the pinpoint gene/drug delivery system to different tissues.