负载TLR7配体/抗原OVA耦联复合功能肿瘤引流淋巴结靶向胶束的构建及免疫作用机制研究

The tumor vaccine based on dendritic cell has several pitfalls such as low targeting efficiency, functional singleness, insufficient activation of T cells, prone to produce humoral immune response and immune tolerance. This proposal aims to construct a tumor draining lymph node targeting coupled with antigen drug delivery system, fully activate T cells by dendritic cells, kill the tumor cells via cellular immune response and reverse the immune tolerance of body. The multifunctional delivery system is Imiquimod/PLLA-PEOz/Pluronic F127-ss-OVA., which could be accumulated in tumor draining lymph nodes through passive target mechanism. The pH-sensitive property makes Imiquimod intracellular orientating releasing, meanwhile increases the cytoplasmic processing ways of loaded antigen. The synergistic application of TLR signal pathway and complement system is expected to accelerate the maturation of dendritic cells in lymph nodes. The immune tolerance state within lymph nodes is reversed by elevation the levels of positive cytokines. The molecular mechanisms of immunotherapy within draining lymph node is expected to lay the foundations for the future development of dendritic cell-based antitumor vaccines in-depth research.

以树突细胞为基础的肿瘤疫苗给药系统大多存在靶向效率不高、功能单调、对T细胞活化不完全、易产生体液免疫及自身免疫耐受等问题。本课题旨在通过肿瘤引流淋巴结靶向给药系统，设计实现树突细胞对T细胞的完全活化，并以细胞免疫应答实现对肿瘤细胞的杀伤，同时逆转肿瘤机体存在的免疫耐受现象。课题构建了负载TLR7配体Imiquimod的PLLA-PEOz/Pluronic F127-ss-OVA复合功能给药系统。该系统可通过被动靶向机理实现在肿瘤引流淋巴结内的蓄积，通过pH敏感特性使Imiquimod在胞内定位释放，增加负载抗原的细胞质处理途径。通过激活TLR信号通路和补体系统两种途径协同加速树突细胞的成熟，进而上调正性细胞因子的表达，逆转淋巴结内的免疫耐受状态。同时，本课题将对该给药系统在引流淋巴结内的相关免疫作用的分子机制展开深入和系统研究，可望对肿瘤免疫治疗及其研究提供思路和借鉴。

以树突细胞为基础的肿瘤疫苗给药系统大多存在靶向效率不高、功能单调、对T细胞活化不完全、易产生体液免疫及自身免疫耐受等问题。该课题首先通过羧基化的Pluronic F127和pH敏感嵌段PEOz-PLA构成的复合胶束，负载免疫增强剂CL264靶向淋巴结内的树突细胞。该疫苗递送系统在皮下免疫后可通过淋巴引流的作用选择性的蓄积在淋巴结，并以清道夫受体-配体介导的内吞提高淋巴结内树突细胞对抗原及免疫增强剂的摄取。另外，借助pH敏感嵌段PEOz的质子化作用实现抗原的胞内呈递途径，增强了细胞毒性T淋巴细胞CTL的产生，促进了抗原特异性免疫应答。其次，通过补体系统，并协同人参皂苷Rg3对免疫功能的增强，设计构建了具免疫佐剂功能的疫苗递送系统COOH-NPs/OVA/Rg3。该递送系统可有效的促进淋巴结内树突细胞的成熟，增强脾脏内效应T淋巴细胞及记忆T淋巴细胞的增殖、分化，有效的抑制了荷瘤小鼠体内肿瘤细胞的生长。本课题的研究为抗肿瘤免疫治疗提供了新的方法和思路，也为设计具淋巴靶向功能的疫苗递送系统提供了理论和实验依据。