Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
Virology. 2020 Nov;550:1-7. doi: 10.1016/j.virol.2020.08.009. Epub 2020 Aug 20.
Avian coronavirus infectious bronchitis virus (IBV) is an important pathogen threatening poultry production worldwide. Here, two recombinant IBVs (rYN-1a-aYN and rYN-1b-aYN) were generated in which ORF1a or ORF1b of the virulent YN genome were replaced by the corresponding regions from the attenuated strain aYN. The pathogenicity and virulence of rIBVs were evaluated in ovo and in vivo. The results revealed that mutations in the ORF1a gene during passage in embryonated eggs caused the decreased pathogenicity of virulent IBV YN strain, proven by determination of virus replication in ECEs and CEK cells, the observation of clinical signs, gross lesions, microscopic lesions, tracheal ciliary activity and virus distribution in chickens following exposure to rIBVs. However, mutations in ORF1b had no obvious effect on virus replication in both ECEs and CEK cells, or pathogenicity in chickens. Our findings demonstrate that the replicase 1a gene of avian coronavirus IBV is a determinant of pathogenicity.
禽传染性支气管炎病毒（IBV）是一种重要的病原体，威胁着全球家禽生产。在这里，我们构建了两个重组 IBV（rYN-1a-aYN 和 rYN-1b-aYN），其中 YN 基因组的 ORF1a 或 ORF1b 被弱毒 aYN 株的相应区域所取代。我们在鸡胚和体内评估了 rIBV 的致病性和毒力。结果表明，在鸡胚中传代过程中 ORF1a 基因的突变导致了强毒 IBV YN 株致病性的降低，这可以通过在鸡胚成纤维细胞（ECEs）和鸡肾细胞（CEK）中检测病毒复制、观察临床症状、大体病变、组织学病变、气管纤毛活性以及病毒在感染 rIBV 后的鸡体内分布来证明。然而，ORF1b 中的突变对 ECEs 和 CEK 细胞中的病毒复制或鸡的致病性没有明显影响。我们的研究结果表明，禽冠状病毒 IBV 的复制酶 1a 基因是决定其致病性的因素。
