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Abstract：
In the present study, an IBV strain I0305/19 was isolated from a diseased commercial broiler flock in 2019 in China with high morbidity and mortality. The isolate I0305/19 was clustered together with viruses in sublineage D of GI-19 lineage on the basis of the complete S1 sequence analysis. Isolate I0305/19 and other GI-19 viruses isolated in China have the amino acid sequence MIA at positions 110-112 in the S protein. Further analysis based on the complete genomic sequence showed that the isolate emerged through at least four recombination events between GI-19 ck/CH/LJS/120848- and GI-13 4/91-like strains, in which the S gene was found to be similar to that of the GI-19 ck/CH/LJS/120848-like strain. Pathological assessment showed the isolate was a nephropathogenic IBV strain that caused high morbidity of 100 % and mortality of 80 % in 1-day-old specific-pathogen-free (SPF) chicks. The isolate I0305/19 exhibited broader tropisms in different tissues, including tracheas, lungs, bursa of Fabricius, spleen, liver, kidneys, proventriculus, small intestines, large intestines, cecum, and cecal tonsils. Furthermore, subpopulations of the virus were found in tissues of infected chickens; this finding is important in understanding how the virulent IBV strains can potentially replicate and evolve to cause disease. This information is also valuable for understanding the mechanisms of replication and evolution of other coronaviruses such as the newly emerged SARS-CoV-2.
摘要：
在本研究中,2019年从中国一只患病的商业肉鸡群中分离出一株IBV株I0305/19，发病率和死亡率较高。基于完整的S1序列分析,将分离物I0305/19与GI-19谱系的亚谱系D中的病毒聚集在一起。在中国分离的分离物I0305/19和其他GI-19病毒在S蛋白的位置110-112处具有氨基酸序列MIA。基于完整基因组序列的进一步分析表明，该分离株通过GI-19ck/CH/LJS/120848-和GI-134/91-样菌株之间的至少四个重组事件出现，其中发现S基因与GI-19ck/CH/LJS/120848样菌株相似。病理评估显示，该分离株是一种肾致病性IBV菌株，在1天大的无特定病原体（SPF）雏鸡中引起100％的高发病率和80％的死亡率。分离物I0305/19在不同组织中表现出更广泛的向性，包括气管,肺,法布里修斯的法萨,脾,脾肝脏,肾脏，proventricuus,小肠，大肠,盲肠,和盲肠扁桃体.此外，在感染的鸡的组织中发现了病毒的亚群;这一发现对于了解毒力IBV毒株如何潜在地复制和进化以引起疾病非常重要。这些信息对于理解其他冠状病毒（例如新出现的SARS-CoV-2）的复制和进化机制也很有价值。
