牛肺表面活性蛋白A（SP-A）在牛多杀性巴氏杆菌感染中的作用及机制研究

牛多杀性巴氏杆菌A型是引起牛呼吸系统疾病（BRD）的重要病原菌之一，其致病机制并不清楚。肺表面活性蛋白A（SP-A）是肺部调节病原体入侵的重要天然免疫分子，而牛肺SP-A蛋白在牛多杀性巴氏杆菌感染致病中的作用尚无报道。基于此，项目申请者前期在牛源A型多杀性巴氏杆菌C1923临床分离株上成功建立遗传操作系统和感染小鼠致病模型。在本研究中采用Co-IP和质谱分析方法筛选鉴定牛多杀性巴氏杆菌与牛肺SP-A蛋白的互作分子，筛选可调控牛肺SP-A蛋白活性的互作分子并构建其基因缺失突变株；进而评估牛肺SP-A蛋白体外影响WT菌株和突变株黏附、侵入、抗吞噬、抗杀伤能力；在感染小鼠实验中评估牛肺SP-A蛋白影响WT菌株和突变株感染后小鼠存活率、组织载菌量、脏器病理损伤及炎症因子水平变化等；系统评价并阐释牛肺SP-A蛋白在牛多杀性巴氏杆菌感染中的作用及机制，为深入解析多杀性巴氏杆菌的致病机制奠定重要基础。

Bovine Pasteurella multocida type A is one of the important pathogens causing bovine respiratory disease (BRD), and its pathogenic mechanism is not clear. Pulmonary surfactant protein A (SP-A) is an important natural immune molecule that regulates the invasion of pathogens in the lung, while the role of bovine lung SP-A protein in the pathogenicity of bovine Pasteurella multocida infection has not been reported. Based on this, the project applicant successfully established the genetic operating system and the pathogenic model of infected mice on the clinical isolates of type A Pasteurella multocida C1923 from bovine in the early stage. In this study, Co-IP and mass spectrometry were used to screen and identify the interaction molecules between bovine Pasteurella multocida and bovine lung SP-A protein, screening the interaction molecules that can regulate the activity of bovine lung SP-A protein, and construct its gene deletion mutant strain. Furthermore, the effects of bovine lung SP-A protein on adhesion, invasion, anti-phagocytosis and anti-killing ability of WT strains and mutant strains in vitro were evaluated. In the experiment of infected mice, the effects of bovine lung SP-A protein on the survival rate, bacterial loading in tissue, pathological injury of organs and levels of inflammatory factors of mice infected with WT strain and mutant strain were evaluated. To systematically evaluate and elucidate the role and mechanism of bovine lung SP-A protein in the infection of bovine Pasteurella multocida. It will lay an important foundation for further understanding the pathogenic mechanism of Pasteurella multocida.