斑点热立克次体作为一种专性细胞内寄生菌，通过蜱虫叮咬传播并引起传染性疾病斑点热，严重威胁人类健康和公共卫生。细菌的毒素-抗毒素(TA)应激反应系统受到生存压力时被激活，在保障细菌生存和种群延续中发挥重要作用。申请人前期发现斑点热立克次体基因组包含多个不同于经典细菌TA系统构成的vapBC TA系统；且在生存压力下其被激活并大量编码VapC毒素蛋白，导致宿主细胞凋亡。为进一步解析斑点热立克次体vapBC TA系统对宿主细胞的作用机制，本课题将通过分析多种蛋白酶对VapB抗毒素蛋白的水解活性阐明vapBC TA系统的激活方式；结合RNA印迹和引物延伸技术揭示VapC蛋白在真核细胞内的靶标和功能；通过监测感染细胞内凋亡通路上关键分子的表达水平，明确该系统最终介导的真核细胞凋亡途径。该研究有望发现斑点热立克次体的致病机制和新的干预靶标，并对其它含TA系统专性胞内菌的研究有借鉴意义。

Spotted fever group rickettsiae is an obligate intracellular bacterium that spreads through the bite of ticks and causes serious infectious diseases. Toxin-antitoxin (TA) system is a stress response system that is activated under survival pressure to reserve the survival requirement for a small portion of bacteria and finally ensure the population continuity. TA systems are abundant in the genome of spotted fever group rickettsiae in which multiple vapBC TA systems are found. The upregulation for the transcription of vapBC TA system and the translation of VapC toxin protein have been confirmed in our previous study and it was also found that VapC protein is able to induce apoptosis of host cells by targeting on the key metabolic process. To further elucidate the mechanism of the rickettsia vapBC TA system interacting on their host cells, we aim to clarify the activation mechanism of vapBC TA system from spotted fever group rickettsiae through in vitro VapB antitoxin degradation assay; reveal the specific targets and function of VapC protein in eukaryotic cells using Northern blot and primer extension technology; and analyze key molecules involved in apoptotic pathway to clarify the eukaryotic cell apoptosis mechanism mediated by vapBC TA system. This study is of great significance for discovering new pathogenic mechanism for spotted fever group rickettsiae and other TA system harboring intracellular bacteria, and novel intervention targets.