自噬抑制NOD信号负反馈调节副猪嗜血杆菌的致炎反应

Haemophilus parasuis (HPS) is the causative agent inducing a severe systemic inflammation and high mortality in pigs, which contribute to the primary livestock healthy problems in the modern pig industry. However, the pathogenesis of the disease caused by HPS remains unclear and efficient preventive and therapeutic measures are lacking. In our previous study, we found that HPS’s entry into cytoplasm activated NOD (Nucleotide-binding oligomerization domain) to enhance the inflammation, and also induced autophagy to protect the host from inflammation. Importantly, NOD signaling pathway is the downstream target of autophagy proteins. Based on mentioned points above, we hypothesized that NOD signals critically control the infectious processes of HPS, and autophagy suppresses the activation of NOD signals served as a negative feedback mechanism. To prove the hypothesis and explore the underlying mechanisms, we will use NF-κB dual luciferase report system, siRNA, co-immunopreciptation and confocal laser microscopy imaging, to illuminate the molecular details and elucidate the biological effects of NOD signals activation by HPS infection, as well as the key targets that autophagy proteins regulated NOD signaling pathway, and to demonstrate the role of NOD in autophagy’s resistance of HPS infection. The project will elucidate the inflammatory and immune mechanisms by HPS infection, and may lead to efficient therapeutic strategies for HPS diseases.

副猪嗜血杆菌（Haemophilus parasuis, HPS）感染引起严重的猪全身性炎症反应，致死率高，是现代猪场面临的首要牲畜健康问题，但是感染机制不清，有效防治措施缺乏。我们前期发现，HPS既能进入细胞浆激活核苷酸结合寡聚化结构域（NOD）致使炎症反应加重，又能诱导自噬形成自我保护机制阻止炎症扩散，而NOD信号通路是自噬蛋白的下游靶点，据此我们推测NOD信号可能精密调控HPS的感染过程，自噬抑制NOD信号上扬是负反馈调节机制。因此，本项目拟采用NF-κB双荧光素酶报告系统、siRNA、免疫共沉淀和激光共聚焦扫描显微镜成像等技术，阐明NOD信号激活介导HPS感染的分子细节及生物学效应，分析自噬蛋白调节NOD信号通路的关键靶点，明确NOD在自噬抵抗HPS感染过程中的作用。以期深入解析HPS致猪感染的炎症机理和免疫机理，为治疗HPS病提供新的有效策略。

随着规模化养猪技术的应用和饲养密度增大，副猪嗜血杆菌（Haemophilus parasuis, HPS）引起的副猪嗜血杆菌病已成为当前猪场最危险的细菌性疾病，常与猪瘟、猪圆环病毒和猪蓝耳病毒等混合感染，加大猪病防控的严峻性，给世界养猪业造成严重的经济损失。HPS感染猪引起多发性纤维素性浆膜炎、关节炎和脑膜炎等全身炎症反应，但其炎症机理和免疫机制并不清楚，导致防治措施缺乏。本研究旨在探讨HPS感染细胞诱导自噬产生的分子机制及其对炎症信号通路和炎性小体的调控作用。主要结果为HPS强毒株感染PK-15细胞诱导自噬，高水平的自噬抑制细菌侵入细胞且通过抑制NF-κB, p38/JNK MAPK信号途径降低炎症因子产生；HPS感染PK-15细胞活化CASP1-IL1β/IL-18需要NLRP3参与，促进自噬下调HPS感染激活的NLRP3-CASP1信号通路，且NLRP3-CASP1炎性小体在自噬成熟阶段被抑制。以上结果说明自噬对HPS诱导的炎症反应有负性调控作用，并在自噬成熟阶段抑制炎性小体的形成，HPS诱导的自噬作为抵抗细菌侵入的防御机制而发挥作用，为寻找抑制HPS炎症的相关调控因子和关键节点以及快速控制HPS炎症发生发展提供新的方向。