Direct evidence of reassortment and mutant spectrum analysis of a very virulent infectious bursal disease virus.
The complete genomic sequence of very virulent infectious bursal disease virus (vvIBDV) Gx strain was determined, including the sequences of segment A, encoding the precursor polyprotein, and segment B, encoding the viral RNA polymerase (VP1) and 5'- and 3'-untranslating regions. Alignment of segment A of Gx with the sequences of 12 other vvIBDV strains showed 97.5% to 99.0% amino acid identity, whereas alignment of segment B of Gx with nine other vvIBDV strains revealed high sequence divergence, ranging from 10.3% to 11%. Phylogenetic analysis of segments A and B showed that they were in different branches, indicating that the reassortment occurred in this strain and that segment A and segment B derived from different pathotype strains. The mutant spectrum analysis of quasispecies virus demonstrated that the mean minimum mutation frequency in VP1 was 8.78-fold higher than in the polyprotein. The most frequent mutations were in the first 1986 nucleotides (nonsynonymous mutations) and the last 660 nucleotides (synonymous mutations), indicating that the 219 amino acid residues in the C-terminal of the VP1 form a functional region.
Gao
Hong-Lei
HL
Division of Avian Infectious Diseases, National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, 427 Maduan Street, Harbin 150001, P. R. China. xmw@hvri.ac.cn
Wang
Xiao-Mei
XM
Gao
Yu-Long
YL
Fu
Chao-Yang
CY
D000818:Animals; D001483:Base Sequence; D016679:Genome, Viral; D007243:Infectious bursal disease virus / Q000472:pathogenicity*; D009154:Mutation; D010802:Phylogeny; D016865:Reassortant Viruses / Q000235:genetics*; D014774:Virulence