Search

学位授与機関：城西大学 学位記番号：博甲第96号，学位の種別：博士（薬学）， 学位授与年月日： 令和2年(2020年)3月17日 (101p.) 2021年3月31日まで要旨のみ公開

Nucleic acids are expected as novel effective medicines, although they require a drug delivery system (DDS). Complexes of nucleic acids with cationic liposomes and cationic polymers have been mainly used as DDS for clinical use. However, most cationic complexes have disadvantages such as strong cytotoxicity and low biocompatibility. We previously found that a plasmid DNA (pDNA) complex coated with biodegradable γ-polyglutamic acid (γ-PGA) provided adequate gene expression without cytotoxicity. Based on these results, we developed a new DDS (multi-functional Nano-device) of pDNA using biodegradable polyamino acids. A typical cationic polyamino acid, poly-L-lysine (PLL), was complexed with pDNA. The binary complexes, however, showed low gene expression and high cytotoxicity. Gene expression was enhanced by addition of poly-L-histidine (PLH) to the binary complexes. PLH can increase endosome escape of the complexes by inducing pH-buffering effects. The quaternary complexes (pDNA-PLL-PLH-γ-PGA complexes) exhibited high gene expression and low cytotoxicity. Furthermore, we used dendrigraft poly-L-lysine (DGL) instead of PLL and PLH to enhance gene expression. DGL had sterically congested cations and was biodegradable. The ternary complexes (pDNA-DGL-γ-PGA complexes) exhibited markedly high gene expression and low cytotoxicity. The pDNA-DGL-γ-PGA complexes also had high gene expression in the marginal zone (rich dendritic cells) of the spleen after intravenous injection into mice. These results indicate that pDNA-DGL-γ-PGA complexes may be useful as vaccine vectors. Therefore we prepared a novel malaria DNA vaccine using Plasmodium yoelii GPI8p-transamidase-related protein pDNA (PyTAM). The PyTAM-DGL-γ-PGA complexes markedly improved survival time of model mice infected with malaria.

Safety in gene therapy is an important issue since both viral and non-viral vectors have toxic side effects. Not only vectors themselves, but also distributions of produced proteins affect safety in gene therapy; thus, development of target-selective gene transfer methods is rational. We have developed organ-, region- and cell-selective gene transfer methods using non-viral vectors. To deliver foreign gene to liver parenchymal cells (hepatocytes), galactosylation of cationic liposome/plasmid DNA complex is useful strategy. Based on analyses for intrahepatic disposition characteristics and interaction with blood components, we formulated novel galactosylated lipoplex with regulated salt concentration to reduce particle size of lipoplex and to stabilize lipoplex simultaneously; as a consequence, we succeeded in improvement of hepatocyte-selective gene transfer after intraportal injection of the lipoplex in mice. On the other hand, administration routes are important for target-selective gene transfer. We discovered that simple instillation of naked plasmid DNA onto organ surface (the liver, kidney, spleen, stomach and lung) in mice and rats could result in effective and region-selective transgene expression. Neither physical force nor carriers are necessary for gene transfer onto organ surface mesothelial cells. To rationally improve transfection efficiency, mechanism of gene transfer should be elucidated. We clarified that Rac-mediated macropinocytosis was required for naked plasmid DNA transfer in gastric mesothelial cells.

Autographa californica multiple nucleopolyhedrovirus (AcMNPV), an alphabaculovirus, has been widely utilized for protein expression in not only insect cells but also mammalian cells. AcMNPV is closely related to Bombyx mori nucleopolyhedrovirus (BmNPV) and nucleotide sequences of AcMNPV genes have high similarity with those of BmNPV. However, the transduction of BmNPV into mammalian cells has not been reported. In this study, we constructed a recombinant BmNPV (BmNPVΔbgp/AcGP64/EGFP) whose surface 64 kDa glycoprotein (BmGP64) was substituted with that from AcMNPV (AcGP64). BmNPVΔbgp/AcGP64/EGFP also carried an EGFP gene under the control of the CMV promoter. BmNPVΔbgp/AcGP64/EGFP successfully transduced HEK293T cells. In comparison, a control construct (BmNPVΔbgp/BmGP64/EGFP) which possessed BmGP64 instead of AcGP64 did not express EGFP in HEK293T cells. The transduction efficiency of BmNPVΔbgp/AcGP64/EGFP was lower than that of an AcMNPV based-BacMam GFP transduction control. This result indicates that AcGP64 facilitates BmNPV transduction into HEK293T cells. BmNPV can be prepared easily on a large scale because BmNPV can infect silkworm larvae without any special equipment, even though specific diet is needed for silkworm rearing. BmNPV gene transduction into mammalian cells can potentially be applied easily for gene delivery into mammalian cells.