PCV2 WH株人工感染断奶仔猪复制多系统衰竭综合征

目的]建立猪圆环病毒2型（PCV2）WH株人工感染断奶仔猪多系统衰竭综合征（PMWS）的动物模型,为探讨PCV2的致病机理及疫苗免疫效果评价奠定基础.方法]将PCV2 WH株通过颈部肌注和滴鼻感染PCV2抗体阴性的7周龄仔猪,攻毒后第4、7d用钥孔血蓝蛋白（KLH）进行刺激,第7、11 d再腹腔注射巯基乙酸,同时设阴性对照组（单独KLH刺激）.攻毒后第35 d扑杀所有试验猪,观察其组织病变,并取肺脏、淋巴结组织提取病毒DNA,用PCR检测PCV2;取试验猪的肺脏、肝脏、脾脏、肾脏、淋巴结、心脏、膀胱等组织制作石蜡切片,进行HE染色和免疫组化分析.结果]攻毒组仔猪的临床症状主要表现为发热、消瘦、被毛粗乱、皮肤苍白;攻毒后第35 d扑杀所有试验猪,剖检发现阴性对照组未出现病理变化,而攻毒组仔猪有明显病理变化,从其病变的肺脏、淋巴结、肾脏、脾脏、肝脏、心脏组织中均能检测到PCV2.HE染色结果显示,组织病理学变化主要为间质性肺炎、淋巴细胞缺失、间质性肾炎、肝脏肝窦单核巨噬细胞增生.免疫组化分析结果显示,肺脏支气管上皮细胞呈明显阳性,部分肺泡巨噬细胞可见阳性信号,主要位于胞浆内;肠系膜淋巴结均出现较强阳性信号,主要位于淋巴细胞的胞浆内;肾间质细胞呈明显阳性.结论]用PCV2WH株攻毒联合KLH和巯基乙酸反复刺激断奶仔猪能成功复制出PMWS,为后续PCV2疫苗的免疫效果评价及PMWS发病机理研究提供了理想的动物模型.

Artificial infection of PCV2 WH strain induced postweaning multisystemic wasting syndrome （PMWS） in piglets

Objective]The piglet model of PCV2 induced PMWS was established for the study on pathogenic mechanism and vaccine evaluation of PCV2.Method]Healthy 7-week-old piglets were infected by PCV2 WH strain through both neck intramuscular injection and intranasal administration.Then,piglets were immunized with keyhole limpet hemocyanin （KLH） on the 4th and 7th day after challenge,respectively,followed by intraperitoneal injection of thioglycollic acid on the 7th and 11th day after challenge.Additionally,the negative control group only received KLH.Experimental animals were slaughtered on the 35th day,after which post-mortem examinations were carried out Lungs and lymph nodes were collected for detection of PCV2 by PCR.In addition,lungs,livers,spleens,kidneys,lymph nodes,hearts and bladders from the experimental piglets were examined by immunohistochemical analysis and HE staining.Result]The challenged piglets showed clinical signs like fever,emaciation,roughened hair and cyanosis of the skin.Autopsies results demonstrated the pathological changes were only found in the challenged group.PCR results indicated the presence of PCV2 in collected samples from the challenged piglets.Histopathological changes including interstitial pneumonia,lymphocyte depletion,interstitial nephritis and hepatic sinusoid mononuclear macrophage proliferation were observed by HE staining.IHC results revealed that the PCV2 positive signals were detected at lung bronchus epithelial cells,and partial alveolar macrophages were mainly situated in cytoplasm.Strong PCV2 positive signals were also detected both at inguinal lymph nodes and mesenteric nodes,mainly situated in cytoplasm.Renal interstitium cells were found to have significantly positive signals.Conclusion]Artificial infection of PCV2 WH strains combined with KLH and thioglycollic acid can induce PMWS in piglets,which play a critical role in developing animal model for study of PCV2 pathogenic mechanism and vaccine evaluation.