抗原5与C型凝集素受体介导细粒棘球蚴免疫逃避的机制研究

The specific mechanism how Echinococcus granulosus escape the host immune response is still not clear. It has been reported that dendritic cells (DC) play an important role in the immune escape of Echinococcus granulosus. Antigen 5 of Echinococcus granulosus is a glycoprotein decorated by carbohydrates with known immune-modulating and C-type lectin receptors (CLR) recognizing activities. In our previous work, Antigen 5 of Echinococcus granulosus was purified and added to DC from human peripheral blood mononuclear cells. We found that it suppressed the expression of co-stimulatory markers on DC. The carbohydrates which are same with Antigen 5 were found to have the ability to suppress the phagocytosis of Antigen 5 by DC. Therefore, we speculate that CLR expressed on DC are the receptors of Antigen 5. Echinococcus granulosus may take advantage of the interaction between Antigen 5 and CLR to escape immune response by impairing the maturity of DC and inducing Treg cells differentiation. In this project, in vitro and in vivo assays will be performed to detect the role of antigen 5 in maturity of DC, expression of cytokines, activation of transcription factors and differentiation of Treg cells. This project will also confirm whether CLR are the receptors of Antigen 5. The carbohydrates which are same with Antigen 5 and anti-CLRs antibody will be used in inhibition assay. These carbohydrates will be also used in vivo assay to show their possible ability in interfering Echinococcus granulosus infection. This project will clarify the immune escape mechanism adopted by Echinococcus granulosus via the interaction between Antigen 5 and CLR.

细粒棘球蚴逃避宿主免疫的机制尚未研究清楚。有研究报道，树突状细胞（DC）在此过程中起重要作用。细粒棘球蚴抗原5是一种具有免疫调节功能的糖蛋白，其结构中包含可能被C型凝集素受体(CLR)识别的糖分子。前期，我们使用分离纯化的抗原5与人外周血来源的DC相作用，发现抗原5抑制DC表面共刺激分子的表达，加入与抗原5结构相同的糖分子可抑制DC对抗原5的内化。因此，我们推测DC表面的CLR是识别抗原5的受体，细粒棘球蚴通过抗原5与CLR相互作用影响DC的成熟，诱导Treg细胞分化，从而逃避宿主免疫。本项目拟通过体外细胞实验和动物实验，检测抗原5对DC的成熟、细胞因子的表达、转录因子的活化及对Treg细胞分化的影响，确定CLR是否是抗原5的受体，观察糖分子或CLR抗体对抗原5作用的DC及对Treg细胞的影响，体内观察糖分子对细粒棘球蚴感染的干预，阐明抗原5与CLR相互作用介导细粒棘球蚴免疫逃避的机制。

细粒棘球蚴逃避宿主免疫的机制尚未研究清楚。有研究报道，树突状细胞（DC）在此过程中起重要作用。细粒棘球蚴囊液中的抗原已被报道包含有免疫调节功能的多糖结构，是潜在的C型凝集素受体(CLR)识别靶点。在本研究中，我们用不同浓度的细粒棘球蚴囊液体刺激外诱导小鼠骨髓来源树突状细胞，结果发现，细粒棘球蚴囊液可以抑制树突状细胞的激活，并对损伤树突状细胞分泌炎性因子的功能。此效应是由细粒棘球蚴囊液激活c-Raf及其下游Toll样受体4信号通路所介导的。而用高碘酸盐氧化修饰细粒棘球蚴囊液抗原时，抑制效应被逆转。多糖抑制实验结果显示，甘露糖受体及巨噬细胞半乳糖型凝集素可能是小鼠骨髓来源树突状细胞表面与细粒棘球蚴囊液抗原结合的受体。本研究在前期的基础上，进一步探索了细粒棘球蚴囊液在影响Toll样受体信号通路、c-Raf的激活从而逃避宿主免疫中的作用，从细胞水平揭示了细粒棘球蚴利用宿主树突状细胞逃避宿主免疫的生物学机制。本研究还探索了宿主树突状细胞上潜在的受体，为研发新的细粒棘球蚴疫苗或靶点药物提供了理论依据。