1株QX基因型鸡传染性支气管炎病毒的致病性

Pathogenicity of a QX genotype avian infectious bronchitis virus

通过对8日龄SPF鸡人工感染鸡传染性支气管炎病毒(IBV)QX株发病,分别在攻毒后3,7,30 d剖杀并采集气管、肺、肾、脾、胸腺、法氏囊制作病理组织切片。攻毒7 d后,采集上述器官相同部位进行免疫组织化学法分析。根据IBV-QX株NP基因的保守序列设计引物,构建质粒标准品,建立了IBV-QX Real-time PCR标准曲线,并跟踪检测试验鸡的口腔、泄殖腔排毒情况。此外,观察并记录了2组鸡的临床症状、体质量差异等信息。结果显示,发病初期(3 d),气管、肺几乎无明显病理变化,其他器官均出现不同程度的炎性反应;临床症状明显期(7 d),所涉及的器官均有不同程度的病理变化;发病后期(30 d),气管纤毛有所恢复,肺、脾炎性反应有所减轻,但肾脏和法氏囊的病变依然严重。免疫组织化学法检测到上述器官均有可见抗原聚集。30 d时被感染鸡的口腔、泄殖腔仍可检出病毒核酸。试验鸡临床症状明显,体质量差异显著。本试验旨在探究具有组织嗜性的IBV-QX毒株对宿主的免疫器官和该病毒的主要靶器官的病理损伤以及被损伤器官的自我修复情况,抗原分布差异,排毒规律等,为后续研究宿主免疫器官发挥天然免疫的相关机理打下基础,也为研发新的疫苗、相关药物的临床药效评价、制定合理的疫苗接种策略提供参考。

In this study,8-day-old specific-pathogen-free(SPF) chickens were infected with infectious bronchitis virus QX strain(IBV-QX).All surviving chickens were euthanized and necropsied.Samples(trachea,lung,kidney,spleen,thymus and bursa) were collected and used to histopathologic examination and immunohistochemical analysis,at 3,7,30 days post-infection(dpi).The primers were designed according to the conserved gene sequence NP gene of IBV-QX strain,and the plasmid standard was constructed.The IBV-QX Real-time PCR standard curve was established,which was used to track and test the virus-shedding of the oral and cloaca of the test chicken.In addition,the information on clinical symptoms and body weight differences between the two groups of chickens was observed and recorded.The results showed that there were almost no obvious pathological change in the trachea and lung,and other organs showed different degrees of inflammatory reaction at 3 dpi.During the obvious period of clinical symptoms(7 dpi),it was found that the organs involved had different degrees of pathological changes.At the late stage of the disease(30 dpi),it was found that the tracheal cilia recovered,and the inflammatory response of the lungs and spleen was alleviated,but the lesions of the kidney and bursa were still serious.The results of immunohistochemistry showed that the above organs had visible antigen aggregation.Viral nucleic acid can still be detected in the oral cavity and cloaca of the infected chicken at 30 days.The infected chickens have obvious clinical symptoms and slow-growing.The aim of this study was to investigate the pathological damage of the hosts immune organs and the main target organs of the virus.And observe the self-healing of the damaged organs by the tissue-dependent IBV-QX strain,difference in antigen distribution,virus-shedding rules,etc.This study lays a foundation for the subsequent study of the relevant mechanisms of natural immunity of host immune organs,and also provides reference for the development of new vaccines,clinical efficacy evaluation of related drugs,and the development of reasonable vaccination strategies.