title: Altered pathogenicity of a tl/CH/LDT3/03 genotype infectious bronchitis coronavirus due to natural recombination in the 5'- 17kb region of the genome.
abstract: An infectious bronchitis coronavirus, designated as ck/CH/LGX/130530, was isolated from an IBV strain H120-vaccinated chicken in this study. Analysis of the S1 gene showed that isolate ck/CH/LGX/130530 was a tl/CH/LDT3/03-like virus, with a nucleotide sequence similarity of 99%. However, a complete genomic sequence analysis showed that ck/CH/LGX/130530 was more closely related to a Massachusetts type strain (95% similarity to strain H120) than to the tl/CH/LDT3/03 strain (86%), suggesting that recombination might have occurred during the origin of the virus. A SimPlot analysis of the complete genomic sequence confirmed this hypothesis, and it showed that isolate ck/CH/LGX/130530 emerged from a recombination event between parental IBV H120 strain and pathogenic tl/CH/LDT3/03-like virus. The results obtained from the pairwise comparison and nucleotide similarity showed that the recombination breakpoint was located in the nsp14 gene at nucleotides 17055-17083. In line with the high S1 gene sequence similarity, the ck/CH/LGX/130530 isolate was serotypically close to that of the tl/CH/LDT3/03 strain (73% antigenic relatedness). Furthermore, vaccination with the LDT3-A vaccine, which was derived from the tl/CH/LDT3/03 strain by serial passaging in chicken eggs, provided good protection against challenge with the tl/CH/LDT3/03 strain, in contrast to the poor protection offered with the H120 vaccine. Interestingly, isolate ck/CH/LGX/130530 exhibited low pathogenicity toward specific-pathogen-free chickens compared with the nephropathogenic tl/CH/LDT3/03 strain, which was likely due to natural recombination in the 5' 17-kb region of the genome. Our results also indicate that the replicase gene of IBV isolate ck/CH/LGX/130530 is associated with viral pathogenicity.
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Zongxi
authors.initials: Z
authors.lastname: Han
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Mengying
authors.initials: M
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Yuqiu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Qiuling
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Yuhao
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Huixin
authors.initials: H
authors.lastname: Li
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
authors.forename: Xiangang
authors.initials: X
authors.lastname: Kong
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China. Electronic address: swliu@hvri.ac.cn.
authors.forename: Shengwang
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D002645:Chickens; D018352:Coronavirus Infections / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D016679:Genome, Viral; D005838:Genotype; D001351:Infectious bronchitis virus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D008404:Massachusetts; D011201:Poultry Diseases / Q000473:pathology* / Q000821:virology*; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D065288:Serogroup
keywords: Infectious bronchitis coronavirus; Pathogenicity; Recombination; Serotype; Vaccination-challenge test