PD-1/PD-L1通路负性调控免疫细胞功能活性在布鲁氏菌感染中的作用和机制

Brucellosis is a serious zoonosis in pastoral areas of Xinjiang. Lacking of understanding of its pathogenesis, it is hard to prevent and treat effectively. A signal pathway of the immune regulatory molecules PD-1 and PD-L1 through the negative regulation of the immune response plays an important role in pathogen infection and tumor immune escape, but its role in brucellosis has not yet been elucidated. Previous work found that the high expression of PD-1 on Treg cells in brucellosis patients, but the mechanism is unclear. The project in the negative regulation of immunity of the PD-1/PD-L1 pathway as the breakthrough point, study on activation of the of PD-1/PD-L1 signaling pathway in brucellosis patients and mice before and after treatment, to clear its relationship with Brucella infection disease. Blocked by antibody of PD-1, we can analysis the negative regulation on macrophage and T cell functional activity by PD-1/PD-L1 pathway and clarify its role on formatting and maintaining host immune suppression. The function of macrophages and T cells are regulated by PD-1/PD-L1 pathway when using wild strains of Brucella for clarify the Brucella infection and host immune response relationship and further provides a new idea of brucellosis prevention and control target by carrying out to block the immune evasion pathway.

布鲁氏菌病为新疆牧区严重的人兽共患传染病，对其发病机制认识不足，阻碍了对其有效的预防和治疗。免疫调节分子PD-1与PD-L1形成信号通路的激活在病原体感染及肿瘤免疫逃逸中通过负调控免疫应答发挥重要作用，但其在布鲁氏菌病的作用尚未阐明。前期工作发现布鲁氏菌病患者Treg细胞高表达PD-1，但其机制尚不清楚。本项目以PD-1/PD-L1通路的免疫负调控为切入点，研究治疗前后布鲁氏菌病患者和感染小鼠PD-1/PD-L1信号通路的激活，明确其与布鲁氏菌感染病程的关系；通过PD-1阻断，分析PD-1/PD-L1通路对巨噬细胞和T细胞功能活性的负调控作用，阐明PD-1/PD-L1通路在宿主免疫抑制状态形成和维持上所起的作用；用野毒株布鲁氏菌调节PD-1/PD-L1通路对巨噬细胞和T细胞影响，阐明布鲁氏菌感染与宿主免疫应答关系，为开展以阻断免疫逃避信号途径为靶点的布鲁氏菌病防治研究提供新思路。

布鲁氏菌病是由布鲁氏菌(Brucella，Bru)感染引起的一种严重人兽共患传染病，其发病机制不清，本研究（1）在布鲁氏菌感染患者外周血细胞检测出PD-1，PD-L1高表达，并且与感染者免疫失衡以及疾病的病程密切相关。（2）建立异源性 T 淋巴细胞体外活化培养体系，发现布鲁氏菌活化PBMC，促使其高表达PD-1，高表达PD-1的CD4+T细胞功能低下（3）通过患者和健康人外周血分离单核细胞和Treg细胞，分别与野毒布鲁氏菌、减毒布鲁氏菌和非致病大肠杆菌共培养，发现巨噬细胞功能的降低和培养上清的TNF-α等相关细胞因子水平下降,分析PD-1/PD-L1 通路在布鲁氏菌病患者中对巨噬细胞的抑制作用。同时进行特异性抗体阻断 PD-1/PD-L1 通路实验观察巨噬细胞增殖和功能改变，证明PD-1/PD-L1 通路在布鲁氏菌感染中对免疫抑制的关键作用。（4）通过布鲁氏菌感染小鼠体内外实验，揭示 PD-1/PD-L1 通路调控布鲁氏菌感染免疫逃避的机制。采用中和抗体阻断 PD-1/PD-L1 通路，感染组Blab/c小鼠单核巨噬细胞影响 C57BL/6 小鼠 T 淋巴细胞的增殖能力，证明了单核巨噬细胞通过 PD-1/PD-L1 通路对 T 细胞功能的抑制作用。本研究显示PD-1/PD-L1在布鲁氏菌治病机制中发挥了重要作用，并且与疾病的慢性化相关，为后续布鲁氏菌病的治疗提供了新的治疗方向。