Changes in VP3 and VP5 genes during the attenuation of the very virulent infectious bursal disease virus strain Gx isolated in China.
A very virulent infectious bursal disease virus (vvIBDV) Gx strain with high pathogenicity was attenuated through replication in specific-pathogen free (SPF) chicken embryos and in chicken embryo fibroblast (CEF) cell cultures. The changes in nucleotide sequences and the deduced amino acid sequences of VP3 and VP5 genes during attenuation were obtained. Sequence analysis of selected passages from numbers 0 to 20 in CEF's (designated here Gx to CEF-20) showed that there were no amino acid changes detected in the VP3 and VP5 genes before CEF-9. There were some changes in the nucleotide sequence and amino acid substitutions in the VP3 and VP5 genes at CEF-9. CEF-9 was an intermediate with some amino acid changes which were possibly related to virulence. The amino acid sequences of VP2 and VP5 genes remained unchanged from CEF-10 to CEF-20. The results of pathogenicity test showed that the mortalities of vvIBDV-Gx, CEF-5, CEF-8, and CEF-9 were 64, 60, 60, and 28%, respectively, while there were no mortalities observed for CEF-10, CEF-15 and CEF-20. There was also no bursal atrophy when chickens were inoculated with CEF-10, CEF-15, and CEF-20. Virus neutralization tests with the Gx strain and sera from inoculated chickens showed that the antigenicity was similar from Gx to CEF-20. The implications of these findings for the study of IBDV virulence and a more effective control of vvIBDV are discussed.
Wang
Xiaomei
X
National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, 427 Maduan Street, Harbin, 150001, PR China. xmw@hvri.ac.cn
Zhang
Houshuang
H
Gao
Honglei
H
Fu
Chaoyang
C
Gao
Yulong
Y
Ju
Yulin
Y
D000595:Amino Acid Sequence; D000818:Animals; D018175:Birnaviridae Infections / Q000401:mortality / Q000821:virology; D002642:Chick Embryo; D002645:Chickens; D002681:China; D014644:Genetic Variation; D007243:Infectious bursal disease virus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011994:Recombinant Proteins / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017361:Viral Nonstructural Proteins / Q000032:analysis / Q000235:genetics*; D015678:Viral Structural Proteins / Q000032:analysis / Q000235:genetics*; D014776:Virus Cultivation
D011994:Recombinant Proteins; C478244:VP3 protein, infectious bursal disease virus; C518635:VP5 protein, infectious bursal disease virus; D017361:Viral Nonstructural Proteins; D015678:Viral Structural Proteins