Liu C, Zhang W, Gong W, Zhang D, She R, Xu B, Ning Y
Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Beijing, PR China; Department of Inspection Technology Research, China Institute of Veterinary Drug Control, No. 8 Zhongguancun South Street, Beijing, PR China.
Department of Inspection Technology Research, China Institute of Veterinary Drug Control, No. 8 Zhongguancun South Street, Beijing, PR China.
J Comp Pathol. 2015 Jul;153(1):38-49. doi: 10.1016/j.jcpa.2015.04.002. Epub 2015 May 14.
The outbreak of highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) in 2006 devastated the Chinese swine industry. HP-PRRS virus is still the predominant strain in mainland China, rather than the classical PRRSV strain, and the attenuated live vaccine remains the preferred choice for protecting piglets against HP-PRRSV infection. To fully evaluate the safety of strain GDr180, the 180th attenuated virus of the HP-PRRSV strain GD, we used clinicopathological, microscopical, ultrastructural, serological and molecular biological methods to assess the different clinical manifestations and respiratory characteristics of piglets inoculated with HP-PRRSV strain GD or strain GDr180. The 5-week-old piglets inoculated with strain GD displayed marked clinical signs, including fever, anorexia, dyspnoea and tachypnoea. Significant interstitial pneumonia was present, characterized by thickened alveolar septa infiltrated with mononuclear cells and cell debris. However, the piglets inoculated with strain GDr180 and the negative control piglets showed neither clinical signs nor microscopical or ultrastructural lesions. Ultrastructural observation of the piglets' tracheas and examination of the dynamic tissue distributions of PRRSV strain GD and attenuated strain GDr180, by immunohistochemistry and fluorescence quantitative reverse transcription-polymerase chain reaction, confirmed significant differences in their pathogenicity and distribution in the respiratory systems of piglets. The differences in pathogenicity are attributable to the different severity of the pathological changes in the pigs inoculated with the two strains. Thus, the HP-PRRSV GDr180 strain is practically harmless to the respiratory systems of piglets and may be a safe candidate for inducing immunity against HP-PRRS.
2006年高致病性猪繁殖与呼吸综合征（HP-PRRS）的爆发重创了中国养猪业。HP-PRRS病毒仍是中国大陆的主要毒株，而非经典PRRSV毒株，减毒活疫苗仍是保护仔猪免受HP-PRRSV感染的首选。为全面评估GDr180株（HP-PRRSV GD株的第180代减毒病毒）的安全性，我们采用临床病理学、显微镜检查、超微结构、血清学和分子生物学方法，评估接种HP-PRRSV GD株或GDr180株的仔猪的不同临床表现和呼吸特征。接种GD株的5周龄仔猪表现出明显的临床症状，包括发热、厌食、呼吸困难和呼吸急促。存在明显的间质性肺炎，其特征为肺泡间隔增厚，有单核细胞浸润和细胞碎片。然而，接种GDr180株的仔猪和阴性对照仔猪既无临床症状，也无显微镜或超微结构病变。通过免疫组织化学和荧光定量逆转录-聚合酶链反应对仔猪气管进行超微结构观察以及对PRRSV GD株和减毒株GDr180的动态组织分布进行检测，证实了它们在仔猪呼吸系统中的致病性和分布存在显著差异。致病性差异归因于接种两种毒株的猪的病理变化严重程度不同。因此，HP-PRRSV GDr180株对仔猪呼吸系统实际上无害，可能是诱导针对HP-PRRS免疫的安全候选毒株。
