title: Triplet amino acids located at positions 145/146/147 of the RNA polymerase of very virulent infectious bursal disease virus contribute to viral virulence.
abstract: Infectious bursal disease virus (IBDV) causes an economically significant disease of chickens worldwide. The emergence of very virulent IBDV (vvIBDV) has brought more challenges for effective prevention of this disease. The molecular basis for the virulence of vvIBDV is not fully understood. In this study, 20 IBDV strains were analysed phylogenically and clustered in three branches based on their full-length B segments. The amino acid triplet located at positions 145/146/147 of VP1 was found highly conserved in branch I non-vvIBDVs as asparagine/glutamic acid/glycine (NEG), in branch II vvIBDVs as threonine/glutamic acid/glycine (TEG) and in branch III vvIBDVs as threonine/aspartic acid/asparagine (TDN). Further studies showed that the three amino acids play a critical role in the replication and pathogenicity of vvIBDV. Substitution of the TDN triplet with TEG or NEG reduced viral replication and pathogenicity of the vvIBDV HuB-1 strain in chickens. However, the replication of the attenuated IBDV Gt strain was reduced in chicken embryo fibroblast cells, whilst it was enhanced in the bursa by substituting NEG with TEG or TDN. The exchange of the three amino acids was also found to be capable of affecting the polymerase activity of VP1. The important role of segment B in the pathogenicity of IBDV was confirmed in this study. These results also provided new insights into the mechanism of the virulence of vvIBDVs and may offer new targets for their attenuation to develop potential vaccines using reverse genetics.
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Kai
authors.initials: K
authors.lastname: Li
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Xiaole
authors.initials: X
authors.lastname: Qi
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Honglei
authors.initials: H
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Liting
authors.initials: L
authors.lastname: Qin
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Nan
authors.initials: N
authors.lastname: Shen
authors.affiliation: Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR 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, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Wang
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000235:genetics*; D000818:Animals; D002060:Bursa of Fabricius / Q000821:virology; D002478:Cells, Cultured; D002645:Chickens; D016000:Cluster Analysis; D004252:DNA Mutational Analysis; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005347:Fibroblasts / Q000821:virology; D007243:Infectious bursal disease virus / Q000235:genetics* / Q000472:pathogenicity*; D016297:Mutagenesis, Site-Directed; D010802:Phylogeny; D015678:Viral Structural Proteins / Q000235:genetics*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics*; D014779:Virus Replication
chemical_list: D000596:Amino Acids; C107669:VP1 protein, infectious bursal disease virus; D015678:Viral Structural Proteins; D037521:Virulence Factors; D012321:DNA-Directed RNA Polymerases