Diversity of genome segment B from infectious bursal disease viruses in the United States

Several phylogenetic lineages of the infectious bursal disease virus (IBDV) genome segment B have been identified. Although this genome segment has been shown to contribute to virulence, little is known about the genetic lineages that exist in the United States. The nucleotide genome segment B sequences of 67 IBDV strains collected from 2002 to 2011 in the United States were examined. Although they were from nine different states, a majority (47) of these viruses were from California. A 722-base pair region near the 5' end of genome segment B, starting at nucleotide 168 and ending at 889, was examined and compared to sequences available in GenBank. The nucleotide sequence alignment revealed that mutations were frequently observed and that they were uniformly spaced throughout the region. When the predicted amino acids were aligned, amino acids at positions 145, 146, and 147 were found to change frequently. Six different amino acid triplets were observed and the very virulent (vv) IBDV strains (based on presence of vvIBDV genome segment A sequence) all had the triplet T145, D146, and N147. None of the non-vvIBDV strains had this TDN triplet. Phylogenetic analysis of the 67 nucleotide sequences revealed four significant genome segment B lineages among the U.S. viruses. One of these included the genome segment B typically found in vvIBDV and three contained non-vvIBDV genome segment B sequences. When the available sequences in GenBank were added to the analysis, two additional lineages were observed that did not contain U.S. viruses; one included viruses from China and the other contained viruses from the Ivory Coast. Although the samples tested do not represent all poultry producing regions in the United States, serotype 1 viruses from states outside California all belonged to one genome segment B lineage. The other three lineages observed in the United States were populated with viruses exclusively found in California, except the serotype 2 lineage, where the type strain was a serotype 2 virus from Ohio. The data provide further evidence for the importance of genome segment B identification during routine molecular diagnosis of all IBDV strains.     

Confirmation of the existence of two distinct genetic groups of infectious bursal disease virus in Australia

OBJECTIVE: To characterise infectious bursal disease viruses (IBDVs) prevalent at major commercial sites throughout Australia and to compare the nucleic acid sequences of local strains of IBDV with those of characterised overseas strains. DESIGN: Samples of bursae were collected from 20 broiler farms that belonged to different poultry companies in New South Wales (NSW), Queensland (Qld), Victoria (Vic), Westem (WA) and South Australia (SA). METHOD: Bursae were collected from broilers between 24 and 35 days of age. Bursal tissue was homogenised and tested for the presence of IBDV antigen using four monoclonal antibodies (Mabs) which detect antigenic variation in IBDV strains. The nucleotide sequences of the hypervariable region (HVR) within the VP2 gene of IBDVs was determined and the deduced amino acid sequences compared with three vaccine strains and six previously characterised Australian IBDV strains. The deduced amino acid sequences were also compared with the published amino acid sequences of overseas strains. The phylogenetic relationships between Australian strains and overseas strains were then determined. RESULTS: IBDV was detected in birds from 14 out of 20 farms sampled. Typing with four Mabs showed that all viruses from Vic (6) and SA (10) were antigenic variants, whereas all viruses from NSW (29), Qld (4) and WA (5) were classical-like strains. Nucleotide sequencing of one sample from each of the 14 farms on which IBDV was detected confirmed results obtained with Mabs. The amino acid sequences of all Australian viruses differed from the amino acid sequences of foreign IBDV strains. Phylogenetic analysis showed that Australian IBDV viruses belonged to two distinct genetic groups. Very virulent (vv) IBDV strains belonged to a third genetic group, and overseas classical and variant strains belonged to a fourth genetic group. CONCLUSIONS: The results confirmed previous findings that there are two groups of IBDV strains circulating in commercial broilers in Australia. The majority are classical-like strains that are antigenically and genetically similar to vaccine strains 002/73 and V877. These classical strains were prevalent in broilers in three states, NSW, Qld and WA. The second group of strains are antigenic variants that were only found in broilers in two states, Vic and SA. All Australian IBDVs characterised to date are genetically distinct and can be differentiated from all other overseas strains. This enables identification of incursion of any exotic strain into Australian poultry, be it classical, US variant or wIBDV strains.     

传染性法氏囊病病毒超强毒HZ株和XN株VP2基因的克隆和序列比较

根据已发表的５２／７０株ＩＢＤＶ基因组序列,设计并合成了一对特异扩增ＩＢＤＶ ＶＰ２基因的引物。以陕西地区分离的ＩＢＤＶ野毒ＸＮ株,ＨＺ株为材料,以其基因组为模板利用ＲＴ－ＰＣＲ技术扩增出了１．５ｋｂ的ｃＤＮＡ产物,将ＶＰ２基因克隆于ＰＵＣ１１９质粒上,得到重组ＰＵＣ１１９质粒。     

鸡传染性法氏囊病毒基因组A节段编码前体多聚蛋白的遗传踪迹分析

为研究鸡传染性法氏囊病毒(IBDV)毒力变异的分子机理,本实验采用进化踪迹分析方法对GenBank中登录的28个毒力不同的IBDV参考病毒株的基因组A节段编码的前体多聚蛋白(NH2-pVP2-VP4-VP3-COOH)推导的氨基酸序列进行分析。结果表明超强IBDV与标准IBDV的差异位点集中在第299位、451位、680位、715位和751位氨基酸上;致弱IBDV与标准IBDV的差异位点在第242位、253位、330位和981位氨基酸。该结果为进一步研究IBDV的毒力变异奠定基础。     

Sequence analysis of both genome segments of three Croatian infectious bursal disease field viruses

In order to determine the mutations responsible for virulence, three Croatian field infectious bursal disease viruses (IBDV), designated Cro-Ig/02, Cro-Po/00, and Cro-Pa/98 were characterized. Coding regions of both genomic segments were sequenced, and the nucleotide and deduced amino acid sequences were compared with previously reported full-length sequenced IBDV strains. Phylogenetic analysis, based on the nucleotide and deduced amino acid sequences of polyprotein and VP1, was performed. Eight characteristic amino acid residues, that were common to very virulent (vv) IBDV, were detected on polyprotein: 222A, 256I, 294I, 451L, 685N, 715S, 751D, and 1005A. All eight were found in Cro-Ig/02 and Cro-Po/00. C-Pa/98 had all the characteristics of an attenuated strain, except for glutamine on residue 253, which is common for vv, classical virulent, and variant strains. Between less virulent and vvIBDV, three substitutions were found on VP5: 49 G --> R, 79 --> F, and 137 R --> W. In VP1, there were nine characteristic amino acid residues common to vvwIBDV: 146D, 147N, 242E, 390M, 393D, 511S, 562P, 687P, and 695R. All nine residues were found in A-Ig/02, and eight were found in B-Po/00, which had isoleucine on residue 390. Based on our analyses, isolates Cro-Ig/02 and Cro-Po/00 were classified with vv IBDV strains. C-Pa/98 shared all characteristic amino acid residues with attenuated and classical virulence strains, so it was classified with those.