A族链球菌作用巨噬细胞通过TLR4/MYD88途径诱导SOCS-1而发生早期免疫逃逸的机制研究

The suppressor of cytokine signaling-1 (SOCS-1) has been known an important negative-feedback molecule which could regulate macrophages activation in late phase. We have focused on the research about immune escape mechanism of group A Streptococcus(GAS) for many years. In previous study, we found that GAS is capable of inducing high expression of the suppressor of cytokine signaling-1（SOCS-1）in macrophages. IFN-β signal , a classic pathway of SOCS-induced in macrophages, only play partly role in GAS-induced SOCS-1 expression, whereas it is closely related with TLR4 signal. So we deduce that TRL4 signal induced SOCS - 1 is an important mechanism for GAS to immune escape in early phase and rapid way. In this subject, Inhibitors and knockout mice will be used to determine the role and mechanism of TLR4 pathway signal proteins in SOCS1-induced by GAS;The technologies, including immune co-precipitation, immunofluorescence and knockout mice, will be used to study the relationship between MyD88 / NF - kB pathway and the JAK/STAT pathway in SOCS1-induced by GAS.;Constructing mutant GAS strains, expressing condidate proteins and Identifying component of GAS that could induce SOCS-1 in macrophage.This study will contributed to understand the interaction and mechanism between bacteria and immune cells, and rich understand the mechanism of innate immune escape about microbial inducing expression of negative regulation factors in macrophage rapidly and directly, help to establish and develop meansures of anti-infection immunity.

已知细胞因子信号抑制蛋白1(SOCS-1)是巨噬细胞重要的、后期相负反馈调节因子。我们多年致力于A族链球菌（GAS）固有免疫逃逸机制研究，前期工作发现GAS感染巨噬细胞可以诱导SOCS-1大量表达，但并不完全依赖于经典的IFN-β受体途径,而与TLR4途径密切相关。推断TRL4信号诱导SOCS-1是GAS早期快速进行免疫逃避的重要机制。本研究拟利用抑制剂、基因敲除鼠等手段确定TLR4通路信号蛋白在GAS诱导SOCS1产生中的作用及机制；利用免疫共沉淀、免疫荧光及基因敲除鼠等手段探讨MyD88/NF-kB通路与JAK/STAT通路的相互关系与作用；通过构建菌体蛋白基因缺失菌等手段确定与诱导SOCS1表达有关的GAS菌体成分。本研究将有助于丰富对细菌与免疫细胞相互作用方式、机制的认识，丰富对微生物诱发巨噬细胞快速表达负调控因子进行固有免疫逃逸机制的了解，有助于拓宽抗感染免疫措施的建立与发展。

A群链球菌(GAS)，革兰氏阳性致病菌，可导致咽炎、脓疱病和其他许多的呼吸道和软组织感染。GAS感染可以激活机体免疫系统巨噬细胞位于膜表面的TLR2、TLR4等膜式识别受体，诱导炎症细胞因子IL-1β，IL - 6和TNF-a以及IFN-β等产生， 但GAS之所以能在人群中持续存在并引起一些严重的感染性疾病，与其具有逃避宿主免疫攻击的能力密切相关，一个常见的现象就是GAS感染的严重坏死部位的一线防御细胞数量极少，我们的研究发现GAS诱导巨噬细胞产生的多种细胞因子、趋化因子相比于大肠杆菌、金黄色葡萄球菌等表现为低下或产生高峰迟滞。探其机制发现：1 GAS感染巨噬细胞早期可诱导负调节因子SOCS-1蛋白大量表达。2、细胞因子IFN-ß活化通路是诱导SOCS-1的经典通路,因此，用IFN-ß特异性中和抗体进行阻断，结果显示SOCS-1表达部分依赖于IFN-ß活化通路。3、另外，有研究证明通过TLR途径可以直接诱导SOCS-1的表达，我们研究发现TLR4/MyD88直接通路在GAS感染早期诱导表达SOCS-1中起重要作用。4、利用抑制剂、基因敲除鼠等手段研究TLR4、MYD88、NF-kB等关键节点蛋白在GAS诱导SOCS-1产生中的作用，结果显示 NF-κB信号通路通过调控JAK1/STAT1通路中STAT1蛋白的表达水平进而影响SOCS-1蛋白的表达5、GAS通过诱导非典型的的活化，影响细胞因子表达显著低于大肠杆菌及金黄色葡萄球菌。. 本研究丰富了细菌与免疫细胞相互作用方式、机制的认识，特别是丰富了对微生物逃逸宿主巨噬细胞的免疫机制的了解，有助于拓宽抗感染免疫措施的建立与发展。