下丘脑—垂体—肾上腺轴在高致病性猪繁殖与呼吸综合征病毒感染仔猪中作用的研究

发布时间：2018-06-05 18:44

本文选题：高致病性猪繁殖与呼吸综合征病毒 + 糖皮质激素　；参考：《中国农业科学院》2015年硕士论文

【摘要】：猪繁殖与呼吸综合征(Porcine Reproductive and Respiratory Syndrome,PRRS)是PRRS病毒(PRRSV)引起的一种急性传染性动物疫病。自2006年以来,高致病性PRRS(HP-PRRS)在我国暴发并广泛流行,给我国养猪业带来严重的经济损失。目前认为该病毒对感染动物机体各组织器官具有广泛的致病性,并能够引起免疫抑制,是引起猪免疫功能紊乱的重要病原之一。哺乳动物下丘脑-垂体-肾上腺(Hypothalamus-Pitutary-Adrenal,HPA)系统,在病原微生物感染或应激条件下,会被高水平的促炎性细胞因子(Proinflammatory Cytokines)激活,激活后通过释放以糖皮质激素(Glucorcoticoids,GCs)为主的一系列内分泌激素来参与调节机体免疫功能,是机体神经-内分泌-免疫环路调控的中枢环节,在维持内环境稳态中发挥重要作用。本实验室前期研究表明,HP-PRRSV感染仔猪早期能够在外周血中检测到大量的促炎性细胞因子,病猪表现典型的高热症状,并伴随严重的胸腺萎缩和胸腺细胞凋亡,死亡率显著高于经典毒株感染。本研究以HP-PRRSV HuN4毒株接种断奶仔猪,观察攻毒后不同时间仔猪HPA轴器官及其释放激素的变化,并通过增强和抑制HPA轴的功能,从免疫系统与神经内分泌系统相互作用的水平上研究PRRSV在猪体内的致病机理。研究结果表明:HP-PRRSV感染后7-10 d,仔猪外周血CRH、ACTH和GCs3种激素的水平发生显著变化,外周血中促炎性因子IL-1β,IL-6,TNF-α的转录水平显著升高;病理组织学观察显示,病毒感染后7-10 d,仔猪下丘脑血管周围炎性细胞浸润,小胶质细胞结节并伴随细胞凋亡。使用糖皮质激素受体特异性抑制剂米非司酮(RU486)处理仔猪并接种HP-PRRSV,实验组同直接攻毒对照组相比,仔猪死亡率明显升高,攻毒后10 d肺部有明显的化脓性肺炎的病理变化。进一步对感染仔猪使用糖皮质激素类似物地塞米松,发现虽然感染仔猪外周血内促炎性细胞因子水平降低,外周血淋巴细胞亚群也趋于正常,但高热症状无法缓解,死亡率和肺脏及胸腺病理变化较单独攻毒组更加严重。以上实验结果表明HP-PRRSV感染诱导仔猪HPA轴系统的变化对机体起到了一定的正向作用,单独使用糖皮质激素受体特异性抑制剂RU486及糖皮质激素类似物地塞米松均打破了病毒感染与HPA轴反应的平衡,增强了HP-PRRSV感染仔猪造成的损伤。该结果对兽医临床用药的选择及畜牧饲料添加剂的选择具有重要的指导意义,为进一步研究HP-PRRSV致病机制的提供了新的实验依据。
[Abstract]:Porcine Reproductive and Respiratory Syndromeg PRRSs (PRRSs) is an acute infectious animal disease caused by PRRS virus. Since 2006, HP-PRRSs (highly pathogenic PRRSs) have been outbreak and widespread in China, which has brought serious economic losses to the pig industry in China. At present, it is considered that the virus has extensive pathogenicity to various tissues and organs of infected animals, and can cause immunosuppression, and it is one of the important pathogens of swine immune dysfunction. The Hypothalamus-Pitutary-Adrenalant (HPA) system of mammalian hypothalamus-pituitary-adrenal gland (Hypothalamus-Pitutary-Adrenalalus) is activated by a high level of proinflammatory cytokines (Proinflammatory Cytokines) under infection or stress by pathogenic microorganisms. After activation, a series of endocrine hormones, mainly glucocorticoid (GCs), are released to regulate the immune function of the body, which play an important role in maintaining the homeostasis of the internal environment. Previous studies in our laboratory showed that a large number of pro-inflammatory cytokines could be detected in peripheral blood of piglets infected with HP-PRRSv in early stage. The pigs showed typical hyperpyretic symptoms, accompanied by severe thymus atrophy and thymocyte apoptosis. The mortality rate was significantly higher than that of classical strain infection. In this study, weaning piglets were inoculated with HP-PRRSV HuN4 strain to observe the changes of HPA axis organs and their releasing hormones at different time after inoculation, and to enhance and inhibit the function of HPA axis. The pathogenesis of PRRSV in pigs was studied from the level of interaction between immune system and neuroendocrine system. The results showed that the levels of CRHP-PRRSv ACTH and GCs3 in peripheral blood of piglets changed significantly at 7-10 days after infection, and the transcription level of IL-1 尾 -IL-6 TNF- 伪 in peripheral blood increased significantly. From 7 to 10 days after virus infection, inflammatory cells infiltration and microglial nodule accompanied by apoptosis were observed in hypothalamic perivascular inflammatory cells of piglets. The piglets were treated with glucocorticoid receptor specific inhibitor Mifepristone RU486) and inoculated with HP-PRRSV.The mortality of the piglets in the experimental group was significantly higher than that in the control group, and there were obvious pathological changes in the lungs of suppurative pneumonia 10 days after the attack. Further more, dexamethasone, a glucocorticoid analogue, was used in infected piglets. It was found that although the levels of proinflammatory cytokines in peripheral blood of infected piglets decreased and the lymphocyte subsets of peripheral blood tended to be normal, the symptoms of hyperthermia could not be alleviated. The mortality and pathological changes of lung and thymus were more serious than those of control group. The results showed that the changes of HPA axis system induced by HP-PRRSV infection had a positive effect on the body. RU486, a glucocorticoid receptor specific inhibitor, and dexamethasone, a glucocorticoid analogue, broke the balance between viral infection and HPA axis reaction, and enhanced the damage caused by HP-PRRSV infection in piglets. The results are of great significance for the selection of veterinary drugs and animal feed additives, and provide a new experimental basis for the further study of the pathogenesis of HP-PRRSV.
【学位授予单位】：中国农业科学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S858.28

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