粗糙型布鲁菌激活四型分泌系统致死被感染巨噬细胞的分子机制研究

布鲁菌是一种革兰氏阴性、兼性胞内寄生菌，由其感染引起的布鲁菌病是一种呈世界范围流行的人畜共患病。布鲁菌无经典的毒力因子，其毒力主要体现在入侵宿主细胞并在胞内存活的能力。布鲁菌脂多糖（LPS）和四型分泌系统（T4SS）是其重要的毒力因子。LPS由类脂A、核心多糖和O-抗原组成，缺失LPS O抗原后布鲁菌由光滑型转变为粗糙型，毒力明显下降，并能致死感染的巨噬细胞（M）。T4SS为布鲁菌胞内存活和建立慢性感染所必需。前期研究表明布鲁菌粗糙型突变株致死感染的M，进一步敲除其T4SS的virB123基因后，不再致死M，表明其依赖T4SS的作用而致死感染的M。本研究旨在阐明粗糙型布鲁菌致死M的分子机制，为疫病防控奠定理论基础。研究内容包括：1）缺失LPS O抗原对布鲁菌T4SS分泌功能的影响；2）鉴定粗糙型布鲁菌致死被感染M的主要效应分子；3）研究粗糙型布鲁菌效应分子致死M的信号通路。

Brucella spp. is a species of Gram-negative, facultative, intracellular bacteria that induces an important zoonosis-Brucellosis in the world-wide. Brucella has no classical virulence factors, its pathogenicity depends on its capability to survive and proliferate within host cells. Lipopolysaccharide (LPS) and the type-IV secretion system (T4SS) are Brucella important virulence factors. LPS is composed of lipid A, core oligosaccharide and O-antigen. Deletion of Brucella LPS O-antigen results in production of Brucella rough mutant with attenuated intracellular survival and virulence. Brucella rough strains cause infected macrophage death with unknown mechanism. Brucella T4SS is important for bacterial intracellar survive and establishing chronic infection. Our previous studies showed that Brucella rough mutant caused infected macrophages death, but double-deletion mutant with further deletion of the T4SS virB123 gene from the rough mutant did kill the infected macrophages, indicating the lethal property of Brucella rough strain depends on association of the T4SS. Therefore, this study aims to elucidate the molecular mechanism of Brucella rough strain caused macrophage death, which will support the control of Brucellosis. This study includes three parts: 1) Elucidating how deletion of O-antigen from the Brucella strain functions on the T4SS secretion. 2) Identification of the Brucella rough strain effectors causing infected macrophage death; 3) Exploring the signaling pathway for Brucella rough strain effector caused macrophage death.