亲神经亚型梅毒螺旋体通过mTOR信号通路诱导Th细胞分化并促进免疫逃逸的作用及其机制

The pathogenesis of neurosyphilis is unknown. Helper T (Th) cell subsets play an important role in the outcome of neurosyphilis. Our previous studies have shown that Treponema pallidum (Tp) neurotropic strain is closely related to neurosyphilis. Th1 to Th2 shift and upregulation of Th17 and Treg cells are found in neurosyphilis. Th cell subsets change along with the clinical progression of neurosyphilis. We hypothesize that neurotropic and non neurotropic Tp have differential effects on Th cell differentiation and thus lead to different neurosyphilis outcomes. This project will determine the relevance between Th cell subsets differentiation and the course of neurosyphilis. This project will first determine in vitro that neurotropic Tp can stimulate na?ve T cells differentiation into Th2 and Treg cell via mTOR signaling pathway which will result in immune escape of Tp and lead to persistent infection. On the contrary, non neurotropic Tp can promote na?ve T cells differentiation into Th1 and Th17 cell via mTOR signaling pathway which will activate microglia and lead to the clearance of the non-neurotropic subtype Tp. This project will further determine that neurotropic Tp can stimulate Th cell differentiation via mTOR signaling pathway in animal models. At last, this project will identify new therapeutic targets for neurosyphilis by selectively interfering important regulators of mTOR signaling pathway in Th cell differentiation. This project will elucidate the neurosyphilis pathogenesis from a new perspective and provide new approach for treatment of neurosyphilis.

神经梅毒发病机制未明，Th细胞亚群对神经梅毒转归起重要作用。我们研究显示：亲神经亚型Tp与神经梅毒密切相关；神经梅毒患者呈现Th1 向Th2 漂移，且Th17和Treg细胞上调；伴随病程进展，Th细胞亚群发生改变。猜测亲神经亚型Tp诱导Th细胞分化功能不同，导致疾病转归不同。本项目首先明确机体Th细胞亚群的变化与神经梅毒病程的相关性。通过验证亲神经亚型Tp通过mTOR信号通路促进Th细胞分化为Th2和Treg细胞，介导Tp发生免疫逃逸；而非亲神经亚型Tp则诱导Th细胞分化为Th1和Th17细胞，激活小胶质细胞，从而被清除。进一步通过动物模型体内验证亲神经亚型Tp通过mTOR信号通路对Th细胞分化的影响。同时遴选出Th细胞mTOR信号通路中的重要调控分子进行干预，寻找神经梅毒生物治疗的靶点。本项目将从全新的角度阐明神经梅毒的发病机制，并为神经梅毒的生物治疗提供新的思路。

神经梅毒发病机制未明，Th 细胞亚群对神经梅毒转归起重要作用。本项目研究神经梅毒患者免疫微环境中T淋巴细胞亚群表达及mTOR信号通路蛋白表达的变化；阐明神经梅毒患者免疫微环境中T淋巴细胞亚群中Th2细胞、Th9细胞、CD8+IL4+细胞和CD8+IL17+细胞的含量与梅毒非神经梅毒患者相比显著下调，而 CD8+IFN-γ+ 细胞含量显著上调。经过ROC分析，CD8+IFN-γ+细胞数可区分神经梅毒和非神经梅毒患者， 曲线下面积是0.670 (95 % CI: 0.513–0.826, P<0.05). 当CD8+IFN-γ+细胞数的临界值取27.25%时，诊断神经梅毒的敏感性是79.2%，特异性是54.5%。神经梅毒患者免疫微环境中T淋巴细胞pmTOR/mTOR和pAKT/AKT低于梅毒非神经梅毒患者，pS6/S6显著低于梅毒非神经梅毒患者。体外研究亲神经亚型Tp通过mTOR信号通路调控Th1、Th2、Th17及Treg 细胞分化的作用。结果发现亲神经亚型Tp经DC细胞抗原提呈给初始Th细胞，促进初始Th细胞分化为Th2细胞增多。初始Th细胞少量甚至几乎不表达mTOR通路中的蛋白。亲神经亚型Tp共培体系中，Akt磷酸化水平比非亲神经亚型Tp共培体系Th细胞表达量低，mTOR总蛋白及S6蛋白磷酸化水平也都较低。提示蛋白激酶B（Akt）磷酸化可促进mTORC1的作用激活S6控制转录，mTORC1可以抑制信号传导和转录活化子的负调节因子SOCS3的表达从而促进初始Th细胞向Th1细胞分化。mTOR信号通路阻断剂雷帕霉素干预可抑制初始Th细胞向Th1的分化，促进Th2的分化。说明在初始Th细胞增值和活化的过程中mTOR通路被激活。研究亲神经亚型Tp通过mTOR信号通路诱导Th分化后Th细胞亚群对小胶质细胞功能的影响。结果当亲神经亚型Tp促进初始Th细胞分化为Th2细胞增多，小胶质细胞吞噬Tp的吞噬率较低。分别经雄性新西兰兔脑脑池注射亲神经亚型Tp和非亲神经亚型Tp，建立神经梅毒兔感染模型。结果亲神经亚型Tp通过mTOR信号通路诱导初始Th细胞分化为Th2和Treg细胞。