摘要
鸡传染性法氏囊病(Infectious Bursal Disease,IBD)是由鸡传染性法囊病病毒(Infectious bursaldisease virus, IBDV)引起的一种急性、高度接触性传染病。IBD是危害世界养禽业最严重的疾病之一。除经典毒株外,具有致病性的血清I型毒株目前还包括弱毒株、抗原变异毒株和超强毒株(very virulent Infectious bursal disease virus, vvIBDV)。IBDV各型毒株致病性不尽相同,特别是1987年vvIBDV的出现给IBD的防控带来了新的挑战。vvIBDV的高致死率给养禽业造成了严重的损失。探索各型毒株致病性差异的分子基础及分子机制一直是IBDV研究的热点之一。IBDV基因功能及致病机制的早期研究主要聚焦在基因组A节段及其编码的VP2蛋白。近来的流行病学数据显示,基因组B节段及其编码的VP1蛋白与vvIBDV的爆发关系密切。本研究将进一步证实B节段及其编码的VP1蛋白与IBDV致病性增强的关系,定位其具体分子基础,并从病毒自身和宿主因子两个角度探讨其分子机制。
克隆获得HuB-1、HeB10XS02、SD10LY013株IBDV流行毒株的全基因组序列。遗传进化分析表明,IBDV VP1蛋白分为明显的3个亚群,即第I亚群(非超强毒)、第II亚群(中国新型vvIBDV)、第III亚群(经典vvIBDV)。HuB-1及SD10LY01VP1属于第III亚群,HeB10XS02的VP1则属于第II亚群。VP1氨基酸序列比对结果表明,I、II、III亚群之间共存在17个保守氨基酸差异位点。根据IBDV毒株的全基因组序列分析和致病性研究,筛选到VP1来源于不同亚群的代表病毒,即Gt(其VP1属于第I亚群)、HLJ0504(其VP1属于第II亚群)、HuB-1(其VP1属于第III亚群)。
分别将弱毒Gt、vvIBDV HuB-1的A节段与上述筛选的3个不同亚群代表病毒的B节段进行组合,共拯救6个重组病毒。研究结果表明,VP1蛋白影响IBDV的复制及致病性,第II、III亚群的VP1促进病毒在体内、外的复制,使IBDV的致病性增强,而第I亚群的VP1则降低病毒在体内、外的复制的能力,使IBDV的致病性减弱。
根据VP1的三维结构,将VP1划分为3个功能结构域,即N-端结构域、中心活性区(M段)和C-端结构域。以HuB-1毒株VP1的N端、M段、C端替换Gt株的相应区域,拯救获得3个细胞适应重组病毒;同时,以Gt株VP1的N端替换HuB-1株的相应区域,拯救获得1个细胞非适应重组病毒。致病性研究结果表明,VP1N端由强变弱,病毒体外复制能力降低,体内复制能力提高,病毒致病性明显降低。VP1N端(1-167aa)氨基酸序列比对结果表明,VP1N端145-147位氨基酸形成3个独特的三联体基序。不同亚群的B节段具有不同的三联体基序,I亚群为NEG、II亚群为TEG、III亚群为TDN。在此基础上,以弱毒Gt为骨架,将NEG分别替换为TEG或TDN,拯救了2个点突变病毒(rGtTEG,rGtTDN);相应的,以vvIBDV HuB-1为骨架,将TDN分别替换为NDN、TEG或NEG,拯救了3个点突变病毒(rHuBNDN,rHuBTEG,rHuBNEG)。研究结果表明,由NEG替换为TEG或TDN,病毒体外复制能力降低,体内的复制能力增强,致病性增强;反之,则使其体外复制能力增强,体内复制能力降低,病毒致病性降低。聚合酶活性检测结果表明,VP1N端145-147位氨基酸影响VP1聚合酶活性,由NEG替换为TEG或TDN,聚合酶活性明显降低;反之,其聚合酶活性明显提高。VP1聚合酶活性的改变进而引起病毒复制能力的改变,是145-147位氨基酸影响病毒致病性的分子机制之一。
为了进一步探索影响VP1聚合酶活性的分子机制,本研究从病毒和宿主两个方面入手探寻影响其活性的因素。研究表明,IBDVVP3蛋白是VP1发挥聚合酶活性的必要因素,但VP3蛋白对病毒聚合酶活性的影响与VP1145-147位氨基酸影响聚合酶活性无正相关性。另一方面,通过酵母共转化实验、CO-IP、激光共聚焦实验证明宿主eIF4AII因子与VP1之间存在相互作用;该蛋白通过与VP1相互作用抑制其聚合酶的活性,进而限制IBDV的复制;进一步聚合酶活性检测表明,宿主eIF4AII因子能够抑制VP1野生型及突变型的聚合酶活性,但eIF4AII抑制聚合酶活性与VP1145-147位氨基酸影响聚合酶活性无正相关性。
综上,本研究证实:VP1蛋白是影响IBDV致病力的重要因素;VP1N端145-147位氨基酸是影响IBDV致病性的重要分子基础,其分子机制是通过改变VP1的聚合酶活性进而影响到病毒复制;病毒蛋白(VP3)和宿主因子(eIF4AII)均参与调控VP1的聚合酶活性的发挥,eIF4AII通过与IBDVVP1之间的相互作用而抑制VP1聚合酶活性,进而限制IBDV的复制,是宿主抵抗病毒感染的天然防御因子之一。
Infectious bursal disease (IBD) caused by infectious bursal disease virus (IBDV) is an acute and highlycontagious disease. IBD is one of the most economically significant diseases of chickens worldwide. Besidesthe classical virulent strains, the pathogenic serotype1viruses also include attenuated strains, antigenicvariant strains and very virulent IBDV (vvIBDV) strains. The emergence of vvIBDV causing severe andacute IBD with more than sixty percent mortality since1987brings new challenges for effective preventionand control of IBD. The exploration of the molecular determinants of vvIBDV virulence is an area of activeresearch. Some reports showed that segment A was not the sole factor that determines the virulence of IBDV.The segment A was not the major contributing factor in the emergence and expansion of vvIBDV. But thevvVP1played an important role in the initiation of vvIBDV expansion. This study further confirmed the VP1protein contributed to IBDV pathogenicity.
The complete genome sequences of HuB-1, HeB10XS02and SD10LY01were cloned and the furtheranalysis of the nucleotide and amino acid sequences showed that VP1of IBDVs were divided into threedistinct subgroups, subgroup I (non-vvIBDV), subgroup II (China vvIBDV) and subgroup III (typicalvvIBDV). The VP1proteins of HuB-1and SD10LY01belong to subgroup III and HeB10XS02belongs tosubgroup II. The alignment of VP1deduced amino acid sequences showed that a total of17conservativeamino acid changes were found among I, II and III subgroups. Gt, HLJ0504and HuB-1with different VP1sfrom different subsets were screened by analysis of the genome sequences.
Three recombinant cell-adapted viruses and three recombinant non-cell-adapted viruses were rescuedbased on the sequences of the attenuated IBDV Gt and vvIBDV HuB-1. The results showed that VP1ofIBDV contributed to its replication and virulence. The VP1proteins from subgroups II and III enhanced thevirulence of IBDV due to their positive effects on viral replication in vitro and in vivo. However, VP1fromsubgroup I reduced the virulence of IBDV due to its negative effects on viral replication in vitro and in vivo.
According to the three-dimensional structure of VP1, VP1is divided into N-terminal, the center of theactive activity and the C-terminal functional domains. Three recombinant cell-adapted viruses were rescuedby replacing N-terminal, central active domain and C-terminal of the B-segment of HuB-1(HuBB) with thecorresponding region of the B-segment of Gt (GtB). Meanwhile, a recombinant non-cell-adapted virus wasrescued by replacing N-terminal of GtB with the corresponding region of HuBB. The virulence of the viruswas enhanced by vvVP1N-domain due to its negative effects on viral replication in vitro but positive effectson viral replication in vivo. The results of VP1N-terminal (1-167aa) amino acid sequences alignment showedthat, the145-147amino acids formed three unique "triplet" motifs, and different subgroup had different motif.Subgroup I was "NEG", subgroup II was "TEG" and subgroup III was "TDN". On this basis, two site-mutantcell-adapted viruses (rGtTEG, rGtTDN) and three site-mutant non-cell-adapted viruses (rHuBNDN,rHuBTEG, and rHuBNEG) were rescued. The results showed that the replacement of "NEG" with "TEG" or"TDN" enhanced the virulence of Gt due to its increased ability to replicate in vivo and reduced ability toreplicate in vitro. On the other hand, the replacement of "TDN" with "TEG" or "NEG" reduced viralvirulence of HuB-1due to its reduced ability to replicate in vivo and enhanced ability to replicate in vitro. The results of the detection of polymerase activity indicated that the polymerase activity was significantlyreduced by replacing "NEG" with "TEG" or "TDN". Otherwise, the polymerase activity was significantlyincreased by replacing "TDN" with "NDN","TEG" or "NEG". One of molecular mechanism of145-147amino acids attributing to viral virulence was the polymerase activity changed that further hanged the viralreplication.
To further explore the molecular mechanism of VP1polymerase activity, the study was carried out fromvirus and host aspects. The results showed that VP3of IBDV was necessary for VP1polymerase activity.However, there was no positive relationship between the impact of VP3on the viral polymerase activity andthe different polymerase activity induced by VP1145-147amino acids mutation. On the other hand, the hostprotein eIF4AII was proved to interact with VP1by yeast co-transformation, CO-IP and confocal. Thepolymerase activity of VP1was inhibited by eIF4AII protein, inhibiting the viral replication of IBDV. Thehost protein eIF4AII inhibited the polymerase activity of wild-type VP1and its mutants by polymeraseactivity assay. However, there was no positive relationship between the inhibition of polymerase activityinduced by eIF4AII and the different polymerase activity induced by VP1145-147amino acids mutation.
In summary, VP1is an important factor of IBDV virulence. The amino acids145-147located at VP1Nterminus is the molecular basis of the enhance virulence of vvIBDV and the molecular mechanism is themutation of145-147amino acids changed the viral polymerase activity and further changed the viralreplication. The viral proteins (VP3) and host factors (eIF4AII) are involved in the regulation of VP1polymerase activity. The eIF4AII interacts with VP1, which inhibits its viral polymerase activity and reducedthe replication of IBDV. The eIF4AII was shown to be a natural host defense factor against viral infection.
引文
1.毕英佐.广东地区鸡传染性法氏囊病的研究.华南农业大学报,1985,1:46~59.
2.高立.利用反向遗传技术构建IBDV候选疫苗株的研究.[硕士学位论文],北京,中国农业科学院,2010.
3.李银聚,吴庭才,张春贤,等.河南省传染性法氏囊病病毒分子流行病学调查.中国家禽,2007,29(8):17~20.
4.祁小乐,王笑梅,高玉龙,等.鸡传染性法氏囊病病毒VP2蛋白研究进展.中国预防兽医学报,2008,30(10):751~754.
5.祁小乐.鸡传染性法氏囊病病毒反向遗传操作系统的建立及基因功能研究.[博士学位论文],北京,中国农业科学院,2007.
6.秦立廷.鸡传染性法氏囊病病毒VP5蛋白功能研究及其基因突变株的构建.[博士学位论文],北京市,中国农业科学院,2009.
7.苏敬良,高福,索勋,禽病学.主译.第十一版.中国农业出版,2005,178~199.
8.王笑梅,王秀荣,陈冠春,等.鸡传染性法氏囊病超强毒致弱株的生物学特性研究.中国预防兽医学报,1999,21(6):436~438.
9.王永山,周宗安,瞿春生,等.麻雀自然感染鸡传染性法氏囊病病毒的调查.中国兽医学报,1994,14(3):268~270.
10.魏永伟,候贤宏,章晓栋,等.基于RNA聚合酶II的传染性法氏囊病病毒反向遗传系统的建立.中国预防兽医学报,2008,30(10):751~754.
11.杨克礼,韦平,潘玲,等.安徽省鸡免疫抑制性疾病的流行病学调查分析.中国兽医科学,2005,35(8),665~670.
12.殷震,刘景华.动物病毒学.第二版.北京科学出版社,1997,329~331.
13.宇文延青.我国部分地区传染性法氏囊病毒病分子流行病学研究.[博士学位论文],北京,中国农业科学院,2008.
14.周蛟,刘福致,陈丽勇.北京地区鸡传染性法氏囊病病原分离.中国兽医杂志,1982,7:25~26.
15.周宗山,王永山,邓小邵,等.传染性法氏囊的生态学与流行病学研究.中国兽医学报,1998,18(5),430~433.
16. Almassy K., and Kakuk T. Immunosuppressive effect of a naturally acquired subclinical bursalagent infection on vaccination against Newcastle disease. Veterinary record,1976,99:435-437.
17. Arnold J. J., Vignuzzi M., Stone J.K., et al. Remote site control of an active site fidelity checkpointin a viral RNA-dependent RNA polymerase. Journal of Biological Chemistry,2005,280:25706–25716.
18. Azad A. A., Barret S. A., Fahey K. J., et al. The characterization and molecular cloning of thedouble-stranded dsRNA genome of an Australian strain of infectious bursal disease virus. Virology,1985,143:35-44.
19. Azad A. A., McKern N. M., Macreadie I. G., et al. Physicochemical and immunologicalcharacterization of recombinant host-protective antigen (VP2) of infectious bursal disease virus.Vaccine,1991,9:715-722.
20. Bayliss C. D., Spies U., Shaw K. A comparison of the sequences of segment A of four infectiousbursal disease virus strains and identication of a variable region in VP2. Journal of GeneralVirology,1990,71:1303-1312.
21. Bayliss C. D., Peters R. W., Cook J. K., et al. A recombinant fowlpox virus that expresses the VP2antigen of infectious bursal disease virus induces protection against mortality caused by the virus.Archives of Virology,1991,120:193-205.
22. Becht H., Muller H., Muller H. K. Comparative studies on structural and antigenic properties oftwo serotypes of infectious bursal disease virus. Journal of General Virology,1988,69:631-640.
23. Ben Abdeljelil N., Delmas B., Mardassi H. Replication and packaging of an infectious bursaldisease virus segment A-drived minigenome. Virus Research,2008,136,146-151.
24. Ben Abdeljelil N., Khabouchi N., Mardassi H. Efficient rescue of infectious bursal disease virususing a simplified RNA polymerase Ⅱ-based reverse genetics strategy. Archives of Virology,2008,153:1131-1137.
25. Benton W. J., Cover M. S., Rosenberger J. K., et al. Physicochemical properties of the infectiousbursal agent. Avian Disease,1967,11:438-445.
26. Birghan C., Mundt E, Gorbalenya A. E. A non-canonical Lon proteinase lacking the ATPasedomain employs the Ser–Lys catalytic dyad to exercise broad control over the life cycle of adouble-stranded RNA virus. The EMBO Journal,2000,19:114–123.
27. Blum S., Schmid S. R., Pause A., et al. ATP hydrolysis by initiation factor4A is required fortranslation initiation in Saccharomyces cerevisiae. Proceedings of the National Academy ofSciences of the United States of America,1992,89:7664–7668.
28. Boot H. J., Agnes H. M., Arjan J. W. Rescue of very virulent and mosaic infectious bursal diseasevirus from cloned cDNA: VP2is not the sole determinant of the very virulent phenotype. Journalof Virology,2000,74:6701-6711.
29. Boot H. J., Dokic K., Peeter B. P. H. Comparition of RNA and cDNA transfection methods forrescue of infectious bursal disease virus. Journal of virological methods,2001,97:67-76.
30. Boot H. J., Huurne A. A., Peeter B. P. H., et al. Efficient rescue of infectious bursal disease virusfrom cloned cDNA: Evidence for involvement of the3’-terminal sequence in genome replication.Virology,1999,265:330–341.
31. Boot H. J., Hoekman A. J., Gielkens A. L. The enhanced virulence of very virulent infectiousbursal disease virus is partly determined by its B-segment. Archives of Virology,2005,150:137–144.
32. Boot H. J., Pritz-Verschuren S. B. Modifications of the3’-UTR stem-loop of infectious bursaldisease virus are allowed without influencing replication or virulence. Nucleic Acids Research,2004,32:211–222.
33. Boot H. J., Huurne A. H., Peeter B. P. H. Generation of full-length cDNA of the two genomicdsRNA segments of infectious bursal disease virus. Journal of virological methods,2000,84:49–58.
34. Borman A. M., Michel Y. M., Malnou C. E., et al. Free poly (A) stimulates capped mRNAtranslation in vitro through the eIF4G-poly(A)-binding protein interaction. Journal of BiologicalChemistry,2002,277:36818–36824.
35. Bottcher B., Kiselev N. A., Stel’Mashchuk V. Y., et al. Three-dimensional structure of infectiousbursal disease virus determined by electron cryomicroscopy. Journal of Virology,1997,71:325–330.
36. Brandt M., Yao K., Liu M., et al. Molecular determinants of virulence, cell tropism, and pathogenicphenotype of infectious bursal disease virus. Journal of Virology,2001,75:11974-11982.
37. Britton P., Green P., Kottier S., et al. Expression of bacteriophage T7RNA polymerase in avian andmammalian cells by a recombinant fowlpox virus. Journal of General Virology,1996,77:963-967.
38. Brown M. D., Green P., Skinner M. A. VP2sequences of recent European ‘very virulent’ isolatesof infectious bursal disease virus are closely related to each other but are distinct from those of‘classical’strains. Journal of General Virology,1994,75(Pt3):675–680.
39. Bruenn J. A. Relationships among the positive strand and double-strand RNA viruses as viewedthrough their RNA-dependent RNA polymerases. Nucleic Acids Research,1991,19:217–226.
40. Burkhardt E., Muller H. Susceptiblility of chicken blood lymphoblasts and monocytes to infectiousbursal disease virus (IBDV). Archives of Virology,1987,94:297-303.
41. Calvert J. G., Nagy E., Soler M., et al. Characterization of the VPg dsRNA linkage of infectiouspancreatic necrosis virus. Journal of General Virology,1991,72(Pt10):2563–2567.
42. Cao Y. C., Yeung W. S., Law M., et al. Molecular characterization of seven Chinese isolates ofinfectious bursal disease virus: classical, very virulent, and variant strains. Avian Disease,1998,42(2):340-351.
43. Caruthers J. M., Johnson E. R., McKay D. B. Crystal structure of yeast initiation factor4A, aDEAD-box RNA helicase. Proceedings of the National Academy of Sciences of the United Statesof America,2000,97:13080–13085.
44. Caston J. R., Martinez-Torrecuadrada J. L., Maraver A., et al. C terminus of infectious bursaldisease virus major capsid protein VP2is involved in definition of the T number for capsidassembly. Journal of Virology,2001,75:10815–10828.
45. Chandrakant T., Jaiswal T. N., Mishra S. C., et al. L-Arginine stimulates immune response inchickens immunized with intermediate plus strain of infectious bursal disease vaccine. Vaccine,2006,24:552–560.
46. Chappell S. A., Edelman G. M., Mauro V. P. A9-nt segment of a cellular mRNA can function as aninternal ribosome entry site (IRES) and when present in linked multiple copies greatly enhancesIRES activity. Proceedings of the National Academy of Sciences of the United States of America,2000,97:1536–1541.
47. Chettle N. J., Wyeth P. J. Failure of maternally derived infectious bursal disease antibodies toserotypes1and2to protect against heterologous virus. British Veterinary Journal,1989,145:165-169.
48. Chettle N. J., Stuart J. C., Wyeth P. J. Outbreak of virulent infectious bursal disease in East Anglia.Veterinary record,1989,125:271-272.
49. Chevalier C., Lepault J., Da Costa B., et al. The last C-terminal residue of VP3, glutamic acid257,controls capsid assembly of infectious bursal disease virus. Journal of Virology,2004,78:3296–3303.
50. Cornell C. T., Perera R., Brunner J. E., et al. Strand-specific RNA synthesis determinants in theRNA-dependent RNA polymerase of poliovirus. Journal of Virology,2004,78:4397–4407.
51. Coulibaly F., Chevalier C., Gutsche I., et al. The birnavirus crystal structure reveals structuralrelationships among icosahedral viruses. Cell,2005,120:761-772.
52. Cruz-Coy J. S., Giambrone J. J., Hoerr F. J. Immunohistochemical detection of infectious bursaldisease virus in formalin-fixed, paraffin-embedded chicken tissues using monoclonal antibody.Avian Disease.1993,37:577-581.
53. Cyril L. N., Gaelle R., Didier T., et al. Very virulent infectious bursal disease virus: reducedpathogenicity in a rare natural segment-B reassorted isolate. Journal of General Virology,2006,87:209–216.
54. Cyril M., Kathleen M., Sofia L., et al. Seven nucleotide changes characteristic of the hepatitis Cvirus genotype359untranslated region: correlation with reduced invitro replication. Journal ofGeneral Virology,2008,89:212-221.
55. Darteil R., Bublot M., Laplace E., et al. Herpesvirus of turkey recombinant viruses expressinginfectious bursal disease virus (IBDV) VP2immunogen induce protection against an IBDVvirulent challenge in chickens. Virology,1995,211:481-490.
56. Dobos P. Protein-primed RNA synthesis in vitro by the virion-associated RNA polymerase ofinfectious pancreatic necrosis virus. Virology,1995,208:19–25.
57. Dobos P., Hill B. J., Hallett R., et al. Biophysical and biochemical characterization of five animalviruses with bisegmented double-stranded RNA genomes. Journal of Virology,1979,32:593-605.
58. Dobos P. In vitro guanylylation of infectious pancreatic necrosis virus polypeptide VP1. Virology,1993,193(1):403-413.
59. Duncan R., Mason C. L., Nagy E., et al. Sequence analysis of infectious pancreatic necrosis virusgenome segment B and its encoded VP1protein: a putative RNA-dependent RNA polymeraselacking the Gly-Asp-Asp motif. Virology,1991,181:541–552.
60. Einem U. V., Gorbalenya A. E., Schirrmeier H., et al. VP1of infectious bursal disease virus is anRNA-dependent RNA polymerase. Journal of General Virololy,2004,85:2221-2229.
61. Escaffre O., Le Nouen C., Amelot M., et al. Both genome segments contribute to the pathogenicityof very virulent infectious bursal disease virus. Journal of Virology,2013,87:2767–2780.
62. Eterradossi N., Arnauld C., Tekaia F., et al. Antigenic and genetic relationships between Europeanvery virulent infectious bursal disease viruses and an early West African isolate. Avian Pathology,1999,28:36–46.
63. Eterradossi N., Arnauld C., Toquin D., et al. Critical amino acid changes in VP2variable domainare associated with typical and atypical antigenicity in very virulent infectious bursal diseaseviruses. Archives of Virology,1998,143:1627–1636.
64. Eterradossi N., Gauthier C., Reda I., et al. Extensive antigenic changes in an atypical isolate ofvery virulent infectious bursal disease virus and experimental clinical control of this virus with anantigenically classical live vaccine. Avian Pathology,2004,33:423–431.
65. Eterradossi N., Picault J. P., Drouin P., et al. Pathogenicity and preliminary antigeniccharacterization of six infectious bursal disease virus strains isolated in France from acuteoutbreaks. Zentralbl Veterinarmed,1992, B39:683–691.
66. Eterradossi N., Arnauld C., Tekaja F., et al. Antigenic and genetic relationships between Europeanvery virulent infectious bursal disease viruses and an early West African isolate. Avian Pathology,1999,28:36-46.
67. Fahey K. J., O’Donnell I. J., Azad A. A. Characterization by Western blotting of the immunogensof infectious bursal disease virus. Journal of General Virology,1985,66:1479-1488.
68. Fernandez-Arias A., Risco C., Martinez S., et al. Expression of ORF A1of infectious bursaldiseasevirus results in the formation of virus-like particles. Journal of General Virology,1998,79(Pt5):1047-1054.
69. Gabriel G., Dauber B., Wolff T., et al. The viral polymerase mediates adaptation of an avianinfluenza virus to a mammalian host. Proceedings of the National Academy of Sciences of theUnited States of America,2005.102:18590–18595.
70. Gao H. L., Wang X. M., Gao Y. L., et al. Direct evidence of symposium reassortment and mutantspectrum analysis of a very virulent infectious bursal disease virus. Avian Disease,2007,51:893-899.
71. Garriga D., Navarro A., Querol-Audí J., et al. Activation mechanism of a noncanonicalRNA-dependent RNA polymerase. Proceedings of the National Academy of Sciences of the UnitedStates of America,2007,104:20540-20545.
72. Garriga D., Querol-Audi J., Abaitua F., et al. The2.6-Angstrom structure of infectious bursaldisease virus-derived T1particles reveals new stabilizing elements of the virus capsid. Journal ofVirology,2006,80:6895–6905.
73. Gingras A. C., Raught B., Sonenberg N. eIF4initiation factors: effectors of mRNA recruitment toribosomes and regulators of translation. Annual Review of Biochemistry,1999,68:913–963.
74. Glick B. Historical perspective: The bursae of Fabricius and its influence on B cell development,past and present. Veterinary Immunology Immunopathology,1991,30:3-12.
75. Gorbalenya A. E., Pringle F. M., Zeddam J. L., et al. The palm subdomain-based active site isinternally permuted in viral RNA dependent RNA polymerases of an ancient lineage. J MolecularBiology,2002,324:47–62.
76. Guittet M., Le Coq H., Picault J. P., et al. Safety of infectious bursal disease vaccines: assessmentof an acceptability threshold. Developments in Biological Standardization,1992,79:147-152.
77. Hassan M. K., Saif Y. M. Influence of the host system on the pathogenicity, immunogenicity, andantigenicity of infectious bursal disease virus. Avian Disease,1996,40:553-561.
78. He C. Q., Ma L. Y., Wang D., et al. Homologous recombination is apparent in infectious bursaldisease virus. Virology,2009,384:51-58.
79. Hein J., Boot H., Sylvia B. E. et al. Modification of the3’-UTR stem-loop of infectious bursaldisease virus is allowed without influencing replication or virulence. Nucleic Acid Research.2004.32:211-222.
80. Heine H. G., Haritou M., Failla P., et al. Sequence analysis and expression of the host protectiveImmunogen VP2of a variant strain of infectious bursal disease virus which can circumentvaccination with standard type Ⅰstrains. Journal of General Virology,1991,72:1835-1843.
81. Herrera M., Garcia-Arriaza J., Pariente N., et al. Molecular basis for a lack of correlation betweenviral fitness and cell killing capacity. PLoS Pathogens,2007,3:0498-0507.
82. Hirai K., Shimakura S. Structure of infectious bursal disease virus. Journal of Virology,1974,14:957-964.
83. Hon C. C., Lam T. Y., Drummond A., et al. Phylogenetic analysis reveals a correlation between theexpansion of very virulent infectious bursal disease virus and reassortment of its genome segmentB. Journal of Virology,2006,80:8503–8509.
84. Howie R., Thorsen J. An enzyme-linked immunosorbent assay (ELISA) for infectious bursaldisease virus. Canadian journal of comparative medicine,1981,45:51-55.
85. Hudson P. J., McKern N. M., Power B. E., et al. Genomic structure of the large RNA segment ofinfectious bursal disease virus. Nucleic Acids Research,1986,14:5001-5012.
86. Ingrao F., Rauw F., Lambrecht B., et al. Infectious Bursal Disease: A complex host-pathogeninteraction. Developmental&Comparative Immunology,2013,41:429-438.
87. Islam M. R., Zierenberg K., Müller H. The genome segment B encoding the RNA-dependent RNApolymerase protein VP1of very virulent infectious bursal disease virus (IBDV) is phylogeneticallydistinct from that of all other IBDV strains. Archives of Virology,2001,146:2481–2492.
88. Ismail N. M., Saif Y. M. Differentiation between antibodies to serotypes1and2infectious bursaldisease viruses in chicken sera. Avian Disease,1990,34:1002-1004.
89. Izet A., Smerdou C., Alonso S., et al. Replication and packaging of transmissible gastroenteritiscoronavirus-derived synthetic minigenome. Journal of Virology,1999,73:1535-1545.
90. Jackwood D. J., Sreedevi B., LeFever L. J., et al. Studies on naturally occurring infectious bursaldisease viruses suggest that a single amino acid substitution at position253in VP2increasespathogenicity. Virology,2008,377:110–116.
91. Jackwood D. H., Saif Y. M. Antigenic diversity of infectious bursal disease viruses. Avian Disease,1987,31:766-770.
92. Jackwood D. J., Sommer-Wagner S. E. Molecular studies on suspect very virulent infectious bursaldisease virus genomic RNA samples. Avian Disease,2005,49:246–251.
93. Jackwood D. J., Jackwood R. J. Infectious bursal disease viruses: molecular differentiation ofantigenic subtypes among serotype1viruses. Avian Disease,1994,38:531-537.
94. Jackwood D. J., Sommer S. E. Restriction fragment length polymorphisms in the VP2gene ofinfectious bursal disease viruses from outside the United States. Avian Disease,1999,43:310-314.
95. Jackwood D. J., Crossley B. M., Stoute S. T., et al. Diversity of genome segment B from infectiousbursal disease viruses in the United States. Avian Disease,2012,56:165-172.
96. Jeon W. J., Lee E. K., Joh S. J., et al. Very virulent infectious bursal disease virus isolated fromwild birds in Korea: epidemiological implications. Virus Research,2008,137(1):153-156.
97. Karunakaran K., Thanappapilldi M., Raghavan N. Seroprevalence of infectious bursal disease(IBD) in parts of Tamil Nadu, India. Comparative Immunology, Microbiology and InfectiousDiseases,1993,16:241-244.
98. Kasanga C. J., Yamaguchi T., Wambura P. N., et al. Detection of infectious bursal disease virus(IBDV) genome in free-living pigeon and guinea fowl in Africa suggests involvement of wild birdsin the epidemiology of IBDV. Virus Gene,2008,36(3):521-529.
99. Kataria R. S., Tiwari A. K., Butchaiah G., et al. Sequence analysis of the VP2gene hypervariableregion of infectious bursal disease viruses from India. Avian Pathology,2001,30:501-507.
100. Kendra A. B., Tatiana L. B., Emily A. D., et al. PB2residue271plays a key role in enhancedpolymerase activity of influenza A viruses in mammalian host cells. Journal of Virology.2010,84,4395-4406.
101. Kibenge F. S., Dhillon A. S., Russell R. G. Growth of serotypes I and II and variant strains ofinfectious bursal disease virus in Vero cells. Avian Disease,1988,32:298-303.
102. Kibenge F. S., Nagarajan M. M., Qian B. Determination of the5' and3' terminal noncodingsequences of the bi-segmented genome of the avibirnavirus infectious bursal disease virus. Archersof Virology,1996,141:1133-1141.
103. Kochan G., Gonzalez D., Rodriguez J. F. Characterization of the RNA binding activity of VP3, amajor structural protein of Infectious bursal disease virus. Archers of Virology,2003,148:723–744.
104. Kyono K., Miyashiro M., Taguchi I. Human eukaryotic initiation factor4AII associates withhepatitis C virus NS5B protein in vitro. Biochemical and biophysical research Communications,2002,292:659–666.
105. Lamphear B. J., Kirchweger R., Skern T., et al. Mapping of functional domains in eukaryoticprotein synthesis initiation factor4G (eIF4G) with picornaviral proteases. Implications forcap-dependent and cap-independent translational initiation. Journal of Biological Chemistry,1995,270:21975–21983.
106. Lasher H. N., Davis V. S. History of infectious bursal disease in the USA—the first two decades.Avian Disease,1997,41:11–19.
107. Le Nou n C., Rivallan G., Toquin D., et al. Significance of the genetic relationships deduced frompartial nucleotide sequencing of infectious bursal disease virus genome segments A or B. Archersof Virology,2005,150:313–325.
108. Le Nou n C., Rivallan G., Toquin D., et al. Very virulent infectious bursal disease virus: reducedpathogenicity in a rare natural segment-B reassorted isolate. Journal of General Virology,2006,87:209-216.
109. Le Nou n C., Toquin, D., Muller, H., et al. Different domains of the RNA polymerase of infectiousbursal disease virus contribute to virulence. PLoS One,2012,7(1): e28064.
110. Lejal N., Da Costa B., Huet J. C., et al. Role of Ser-652and Lys-692in the protease activity ofinfectious bursal disease virus VP4and identification of its substrate cleavage sites. Journal ofGeneral of Virology,2000,81:983–992.
111. Letzel T., Mundt E., Gorbalenya A. E. Evidence for functional significance of the permuted Cmotif in Co2+-stimulated RNA-dependent RNA polymerase of infectious bursal disease virus.Journal of General of Virology,2007,88:2824–2833.
112. Lim B. L., Cao Y. C., Yu T., et al. Adaption of very virulent infectious bursal disease virus tochicken embryonic fibroblasts by site-directed mutagenesis of residues279and284of viral coatprotein VP2. Journal of Virology,1999,73:2854-2862.
113. Liu M. H., Vakharia V. N. Nonstructural protein of infectious bursal disease virus inhibits apoptosisat the early stage of virus infection. Journal of virology,2006,80(7):3369-3377.
114. Liu M., Vakharia V. N. VP1protein of infectious bursal disease virus modulates the virulence invivo. Virology,2004,330:62–73.
115. Lojkic I., Bidin Z., Pokric B., et al. Sequence analysis of both genome segments of three Croatianinfectious bursal disease field viruses. Avian Disease,2008,52:513-519.
116. Lombardo E., Maraver A., Castn J. R., et al. VP1, the putative RNA-dependent RNA polymeraseof infectious bursal disease virus, forms complexes with the capsid protein VP3, leading toefficient encapsidation into virus-like particles. Journal of Virology,1999,73:6973–6983.
117. Lombardo E., Maraver A., Espinosa L., et al. VP5, the nonstructural polypeptide of infectiousbursal disease virus accumulates within the hostplasma membrane and induces cell lysis. Virology,2000,277:345-357.
118. Lorsch J. R, Herschlag D. The DEAD box protein eIF4A.1. A minimal kinetic and thermodynamicframework reveals coupled binding of RNA and nucleotide. Biochemistry,1998a,37:2180–2193.
119. Lorsch J. R., Herschlag D. The DEAD box protein eIF4A.2. A cycle of nucleotide andRNA-dependent conformational changes. Biochemistry,1998b,37:2194–2206.
120. Magyar G., Chung H. K., Dobos P. Conversion of VP1to VPg in cells infected by infectiouspancreatic necrosis virus. Virology,1998,245:142–150.
121. Mahardika G. N., Becht H. Mapping of cross-reacting and serotype-specific epitopes on the VP3structural protein of the infectious bursal disease virus (IBDV). Archers of Virology,1995,140:765-774.
122. Maraver A., Clemente R., Rodriguez J. F., et al. Identification and molecular characterization of theRNA polymerase-binding motif of infectious bursal disease virus inner capsid protein VP3. Journalof Virology,2003,77:2459–2468.
123. Maraver A., Clemente R., Rodríguez J. F., et al. Identification and molecular characterization of theRNA polymerase-binding motif of infectious bursal disease virus inner capsid protein VP3. Journalof Virology,2003,77:2459-2468.
124. Martinez-Salas E., Ramos R., Lafuente E., et al. Functional interactions in internal translationinitiation directed by viral and cellular IRES elements. Journal of General Virology,2001,82:973–984.
125. Mirriam G. J., Tacken, Peeters B. P., et al. Infectious bursal disease virus capsid protein VP3interacts with VP1,the RNA-dependent RNA polymerase,and with viral double-strandedRNA.Journal of Virology,2002,11:11301-11311.
126. Müller H., Islam M. R., Raue R. Research on infectious bursal disease-the past, the present and thefuture. Veterinary microbiology,2003,97:153-165.
127. Müller H., Scholtissek C., Becht H. The genome of infectious bursal disease virus consists of twosegments of double-stranded RNA. Journal of Virology,1979,31:584-589.
128. Müller H., Nitschke R. The two segments of the infectious bursal disease virus genome arecircularized by a90,000-Da protein. Virology,1987,159:174-177.
129. Mundt E., Kollner B., Kretzschmar D. VP5of infectious bursal disease virus is not essential forviral replication in cell culture. Journal of Virology,1997,71:5647–5651.
130. Mundt E., Beyer J., Muller H. Identification of a novel viral protein in infectious bursal diseasevirus-infected cells. Journal of General Virology,1995,76(Pt2):437-443.
131. Mundt E. Tissue culture infectivity of different strains of infectious bursal disease virus isdetermined by distinct amino acids in VP2. Journal of General Virology,1999,80:2067-2076.
132. Mundt E., Müller H. Complete nucleotide sequences of5'-and3'-noncoding regions of bothgenome segments of different strains of infectious bursal disease virus. Virology,1995,209:10-16.
133. Murayama A., Weng L., Date T., et al. RNA polymerase activity and specific RNA structure arerequired for efficient HCV replication in cultured cells. PLoS Pathogens,2010,6: e1000885.
134. Nagarajan M. M., Kibenge F. S.The5'-terminal32basepairs conserved between genome segmentsA and B contain a major promoter element of infectious bursal disease virus. Archers of Virology,1997,142:2499-2514.
135. Nouen C. L., Toquin D., Muller H., et al. Different domains of the RNA polymerase of infectiousbursal disease virus contributes to virulence. PLoS One,2012,7: e28064.
136. Nunya T., Otaki Y., Tajima M., et al. Occurance of acute infectious bursal disease with highmortality in Japan and pathogenicity of fields isolates in specific-pathogen-free chickens. AvianDisease,1992,36:597-609.
137. Oppling V., Muller H., Becht H. The structural polypeptide VP3of infectious bursal disease viruscarries group-and serotype-specific epitopes. Journal of General Virology,1991,72(Pt9):2275-2278.
138. Pan J., Lin L., Tao Y. J. Self-guanylylation of birnavirus VP1does not require an intact polymeraseactivity site. Virology,2009, S395:87–96.
139. Pan J., Vakharia V. N., Tao Y. J. The structure of a birnavirus polymerase reveals a distinct activesite topology. Proceedings of the National Academy of Sciences of the United States of America,2007,104:7285-7390.
140. Patton J. T. Rotavirus VP1alone specifically binds to the3’end of viral mRNA but the interactionis not sufficient to initiate minus-strand synthesis. Journal of Virology,1996,70:7940-7947.
141. Perez M., Sanchez A., Cubitt B., et al. A reverse genetics system for Bornavirus disease virus.Journal of General Virology,2003,84,3099-3104.
142. Qi X. L., Gao H. L., Gao Y. L., et al. Naturally occurring mutations at residues253and284in VP2contribute to the cell tropism and virulence of very virulent infectious bursal disease. AntiviralResearch,2009,84:225-233.
143. Qi X. L., Gao Y. L., Gao H. L., et al. An improved method for infectious bursal disease virusrescue using RNA polymerase II system. Journal of Virological Methods,2007,142:81-88.
144. Qin L. T., Qi X. L., Gao Y. L., et al. VP5deficient mutant virus induced protection againstchallenge with very virulent infectious bursal disease virus of chickens. Vaccine,2010,28:3735-3740.
145. Raue R., Islam M. R., Islam M. N., et al. Reversion of molecularly engineered, partially attenuated,very virulent infectious bursal disease virus during infection of commercial chickens. AvianPathology,2004,33:181–189.
146. Schnitzler D., Bernstein F., Muller H., et al. The genetic basis for the antigenicity of the VP2protein of the infectious bursal disease virus. Journal of General Virology,1993,74(Pt8):1563-1571.
147. Schroder A., van Loon A. A., Goovaerts D., et al. Chimeras in noncoding regions betweenserotypes I and II of segment A of infectious bursal disease virus are viable and show pathogenicphenotype in chickens. Journal of General Virology,2000,81:533–540.
148. Schroder A., van Loon A. A., Goovaerts D., et al. VP5and the N terminus of VP2are notresponsible for the different pathotype of serotype I and II infectious bursal disease virus. Journalof General Virology,2001,82:159–169.
149. Schroder A., van Loon A. A., Goovaerts D., et al. Chimeras in noncoding regions betweenserotypes I and II of segment A of infectious bursal disease virus are viable and show pathogenicphenotype in chickens. Journal of General Virology,2000,81:533-540.
150. Shi L., Li H., Ma G., et al. Competitive replication of different genotypes of infectious bursaldisease virus on chicken embryo fibroblasts. Virus Research,2009,39:45-62.
151. Shwed P. S., Dobos P., Cameron L. A., et al. Birnavirus VP1proteins form a distinct subgroup ofRNA-dependent RNA polymerases lacking a GDD motif. Virology,2002,296:241–250.
152. Spies U., Muller H., Becht H. Properties of RNA polymerase activity associated with infectiousbursal disease virus and characterization of its reaction products. Virus Reserch,1987,8:127-140.
153. Spies U., Muller H. Demonstration of enzyme activities required for cap structure formation ininfectious bursal disease virus, a member of the birnavirus group. Journal of General Virology,1990,71(Pt4):977-981.
154. Stricker R. L., Behrens S. E., Mundt E. Nuclear factor NF45interacts with viral proteins ofinfectious bursal disease virus and inhibits viral replication. Journal of Virology,2010,84:10592-10605.
155. Sun J. H., Lu P., Yan Y. X., et al. Sequence and Analysis of Genomic Segment A and B of VeryVirulent Infectious Bursal Disease Virus Isolated from China. Journal of Veterinary Medicine,2003,B50:148-154.
156. Tacken M. G., Thomas A. A., Peeters B. P., et al. VP1, the RNA-dependent RNA polymerase andgenome-linked protein of infectious bursal disease virus, interacts with the carboxy-terminaldomain of translational eukaryotic initiation factor4AII. Archers of Virology,2004,149:2245-2260.
157. Tacken M. G., Peeters B. P., Thomas A. A., et al. Infectious bursal disease virus capsid protein VP3interacts both with VP1, the RNA dependent RNA polymerase, and with viral double-strandedRNA. Journal of Virology,2002,76:11301–11311.
158. Tacken M. G., Rottier P. J., Gielkens A. L., et al. Interactions in vivo between the proteins ofinfectious bursal disease virus: capsid protein VP3interacts with the RNA-dependent RNApolymerase, VP1. Journal of General Virology,2000,81:209–218.
159. Tacken M. G., van den Beuken P. A., Peeters B. P., et al. Homotypic interactions of the infectiousbursal disease virus proteins VP3, pVP2, VP4and VP5: mapping of the interacting domains.Virology,2003,312:306–319.
160. Tetsuro I., Peters C. J., Makino S. Rift valley fever virus nonstructural protein NSs promotes viralRNA replication and transcription in a minigenome system. Journal of virology,2005,79:5606-5615.
161. Tiwari A. K., Kataria R. S., Indervesh, et al. Differentiation of infectious bursal disease viruses byrestriction enzyme analysis of RT-PCR amplified VP1gene sequence. Comparative Immunology,Microbiology and Infectious Diseases,2003,26:47~53.
162. van den Berg T. P., Gonze M., Meulemans G. Acute infectious brusal disease in poultry: isolationand characterization of a highly virulent strain. Avian Pathology,1991,20:409-421.
163. van Den Berg T. P., Morales D., Enterradossi N., et al. Assessment of genetic,antigenic andpathotypic criteria for the characterization of IBDV strains. Avian Pathology,2004,1:1–2.
164. van den Berg, T.P. Acute infectious bursal disease in poultry: a review. Avian Pathology,2000,29:175-194.
165. van Dijk A. A., Makeyev E. V., Bamford D.H. Initiation of viral RNA-dependent RNApolymerization. Journal of General Virology,2004,85:1077-1093.
166. van Loon A. A., de Haas N., Zeyda I., et al., Alteration of amino acids in VP2of very virulentinfectious bursal disease virus results in tissue culture adaptation and attenuation in chickens.Journal of General Virology,2002,83:121-129.
167. von Einem U. I., Gorbalenya A. E., Schirrmeier H., et al. VP1of infectious bursal disease virus isan RNA-dependent RNA polymerase. Journal of General Virology,2004,85:2221–2229.
168. Wang X., Fu C., Gao H., et al. Pathogenic antigenic and molecular characterization of very virulentstrain (Gx) of infectious bursal disease virus isolated in China. Agricμltural Sciences in China,2003,2:566-572.
169. Wang Y. Q., Kang Z. H., Gao H. L., et al., A one-step reverse transcription loop-mediatedisothermal amplification for detection and discrimination of infectious bursal disease virus.Virology Journal,2011,8:108.
170. Wang, X. M., Zeng, X. W., Gao, H. L., et al. Changes in VP2gene during the attenuation of veryvirulent infectious bursal disease virus strain Gx isolated in China. Avian Disease,2004,48:77–83.
171. Wang Y. Q., Qi X. L., Gao H. L., et al. Comparative study of the replication of infectious bursaldisease virus in DF-1cell line and chicken embryo fibroblasts evaluated by a new real-timeRT-PCR. Journal of Virological Methods,2009,157:205–210.
172. Wei Y., Li J., Zheng J., et al. Genetic reassortment of infectious bursal disease virus in nature.Biochemical and Biophysical Research Communications,2006,350:277–287.
173. Wei Y., Yu X., Zheng J., et al. Reassortant infectious bursal disease virus isolated in China. VirusResearch,2008,131:279–282.
174. Xu H. T., Si W. D., Dobos P. Mapping the site of guanylylation on VP1, the protein primer forinfectious pancreatic necrosis virus RNA synthesis. Virology,2004,322:199–210.
175. Yamaguchi T., Iwata K., Kobayashi M., et al. Epitope mapping of capsid proteins VP2and VP3ofinfectious bursal disease virus. Archers of Virology,1996,141:1493-1507.
176. Yamaguchi T., Ogawa M., Miyoshi M., et al. Sequence and phylogenetic analyses of highlyvirulent infectious bursal disease virus. Archers of Virology,1997,142:1441-1458.
177. Yamaguchi T., Ogawa M., Inoshima Y., et al. Identification of sequence changes responsible for theattenuation of highly virulent infectious bursal disease virus. Virology,1996,223:219–223.
178. Yao K., Goodwin M. A., Vakharia V. N., et al. Generation of a mutant infectious bursal diseasevirus that does not cause bursal lesions. Journal of virololy,1998,72:2647-2654.
179. Yao K., Vakharia V. N. Induction of apoptosis in vitro by the17-kDa nonstructural protein ofinfectious bursal disease virus: possible role in viral pathogenesis.Virology,2001,285:50-58.
180. Yap C. C., Ishii K., Aoki Y., et al. A hybrid baculovirus-T7RNA polymerase system for recoveryof an infectious virus from cDNA. Virology,1997,231:192-200.
181. Yohsuke O., Keita S., Kentaro K., et al. Rescue of Akabane virus(family Bunyaviridae) entirelyfrom cloned cDNAs by using RNA PolymeraseⅠ. Journal of General Virology,2007,88:3385-3390.
182. Yoshinori K., Min Z., Mai Y., et al., Human metapneumovirus M2-2protein inhibits viraltranscription and replication. Microbes and Infection,2009,1-11.
183. Yu F., Qi X. L., Gao Y. L., et al. A simple and efficient method to rescue very virulent infectiousbursal disease virus using SPF chickens. Archers of Virology,2012,157:969–973.
184. Yu F., Qi X. L., Yuwen Y. Q., et al. Molecular characteristics of segment B of seven very virulentinfectious bursal disease viruses isolated in China. Virus Genes,2010,41:246–249.
185. Yu F., Ren X G.., Wang Y. Q., et al. A single amino acid V4I substitution in VP1attenuatesvirulence of very virulent infectious bursal disease virus (vvIBDV) in SPF chickens and increasesreplication in CEF cells. Virology,2013,40:204-209.
186. Yuwen Y. Q., Gao Y. L., Gao H. L., et al. Sequence analysis of the VP2hypervariable region ofeight very virulent infectious bursal disease virus isolates from the northeast of China. AvianDisease,2008,52:284-290.
187. Zierenberg K., Raue R., Nieper H., et al. Generation of serotype1/serotype2reassortant viruses ofthe infectious bursal disease virus and their investigation in vitro and in vivo. Virus Research,2004,105:23–34.
188. Zierenberg K., Nieper H., van den Berg T. P., et al. The VP2variable region of African and Germanisolates of infectious bursal disease virus: comparison with very virulent,"classical" virulent, anattenuated tissue culture-adapted strains. Archers of Virology,2000,145:113-125.