题目：Action of Immunostimulatory DNA Drug Can Be Changed by Nanoparticles
报告人：Prof. Nobutaka Hanagata 日本独立行政法人物质材料研究机构纳米创新中心主任
时间：2014年1月9日（星期四）下午 1:30
地点：材料学院210会议室
【个人简介】
Prof. Nobutaka Hanagata received a Ph.D. in Biochemical Engineering from University of Tokyo in 1994. 1997-2001, he is an Associate Professor in University of Tokyo. 2001-2005, He is a full Professor in Tokyo University of Technology. From 2005, he moved to National Institute for Materials Science (NIMS) and worked at Biomaterials Center. Now he is a Director at Nanotechnology Innovation Station, a Group leader at Biomaterials Center in NIMS and a Professor at Graduate School of life Science, Hokkaido University.
Prof. Hanagata’s group is working to establish a novel field of material nanobiology called "surface nanobiology" or "particle nanobiology". Specific research interest includes (a) Elucidating bone formation mechanism and developing artificial bone, and (b) Evaluating biomaterials using comprehensive gene expression analysis, (c) Development of nanoparticles for delivery of next generation medicine.
Prof. Hanagata has published more than 100 journal papers in Nature medicine, Scinstific Report, ACS Nano, Biomaterials, Small et al. Currently, Prof. Hanagata is an Editor of “Materials Express”, Visiting Professor in Kanazawa Institute of Technology, and so on.
【报告摘要】
Oligodeoxynucleotides (ODNs) that contain unmethylated cytosine-phosphate-guanine (CpG) motifs have the potential to stimulate the immune system via interaction with the pattern-recognition receptor, Toll-like receptor 9 (TLR9). In humans, TLR9 is expressed in B cells and plasmacytoid dendritic cells (pDC). TLR9 activation in B cells induces cytokines—including interleukin-6 (IL-6), IL-10, and IL-12—through the signal-transduction pathways involved in nuclear factor-κB. Meanwhile, TLR9 activation in pDC induces type-I interferons, tissue necrosis factor-α (TNFα), IL-6, IL-12, and IFNγ-inducible 10-kDa protein. The potential of CpG ODNs to stimulate the immune system via activation of TLR9 can be applied to infectious diseases treatment, cancer therapy, and allergy treatment CpG ODNs are divided into 4 classes according to their sequence properties. Class-A and class-B CpG ODNs have been well characterized. Class-A CpG ODNs have a palindromic structure, consisting of a phosphodiester backbone in the center of the sequence, and poly-G motifs with a phosphorothioate backbone at each end. Class-B CpG ODNs have a linear structure, consisting entirely of a phosphorothioate backbone. IFN-α is induced by class-A, but not by class-B CpG ODNs. By contrast, class-B CpG ODNs are able to proliferate and activate B cells, leading to IL-6 production. Meanwhile, class-A CpG ODNs have a lower potential to induce IL-6.
Under certain physiological conditions, class-A CpG ODNs form nanometer-sized multimers by self-assembly, because of the palindromic and poly-G sequences. By contrast, class-B CpG ODNs lack the potential to form such higher-order structured multimer. IFN-α induction by class-A CpG ODNs is thought to result from the formation of multimers, the average size of which has been demonstrated to be ~100 nm in length. Interestingly, IFN-α production was observed when class-B CpG ODNs were loaded onto 180-nm polystyrene nanoparticles, suggesting that nanoparticles are able to alter the cytokine induction mediated by interaction between class-B CpG ODNs and TLR9. However, the mechanism by which class-B CpG ODNs acquires the potential to induce IFN-α remains unclear. In the present study, we aimed to clarify this mechanism. For this purposes, we prepared silicon nanoparticles (Si-NPs) with an average diameter of 3.4 nm, because silicon has a low inherent toxicity. The Si-NP possessed a substantial photoluminescence quantum yield in the visible region. Generally, polycations such as polyethyleneimine and poly-L-lysine are used for modifying nanoparticles to electrostatically bind negatively charged DNA. However, polycations have been reported to result in nonspecific binding of negatively charged molecules, and also to promote the formation of nanoparticles aggregates, which are thought to cause side effects. It is likely that the toxicity of polycations may affect cytokine induction in the immune system, and also the interaction between CpG ODN and TLR9. Thus, we modified the surface of Si-NP with allylamine, to ensure a positive charge, and electrostatically bound to CpG ODN molecules. Furthermore, alternative surface modification of Si-NP was performed by introducing maleimide into allylamine amino group to covalently crosslinked CpG ODN molecules onto Si-NP.
Here, we present the binding mode dependent bifurcation of cytokine induction (Figure 1) and discuss the possible mechanism of bifurcated cytokine induction by interaction between class-B CpG ODN molecules and TLR9. Our discoveries also provide that nanoparticles play roles in not only delivery of CpG ODN but also control of CpG ODN action.