传染性法氏囊病病毒CJ－801bkf毒株VP2 cDNA基因结构的分析

ANALYSIS OF cDNA GENE CODING FOR PROTECTIVEANTIGEN VP2 OF CJ-801bkf STRAIN OF INFECTIOUS BURSAL DISEASE VIRUS

以传染性法氏囊病病毒（ＩＢＤＮ）中国毒株ＣＪ－８０１ｂｋｆ的基因组Ａ片段ｄｓＲＭＡ为模板，经反向转录和ＰＣＲ扩增，克隆了保护性抗原ＶＰ２ｃＤＮＡ基因。经Ｓａｎｇｅｒ法测序，确定了ＶＰ２ｃＤＮＡ基因有１４８４个核苷酸，推测了ＶＰ２氨基酸的顺序，与已报导的６株ＩＢＤＶ毒株ＣｕＩ、ＰＢＧ９８、５２／７０、００２－７３、ＳＴＣ和ＶａｒｉａｎｔＥ的ＶＰ２区做了比较，证明：克隆的ＣＪ－８０１ｂｋｆＶＰ２ｃＤＮＡ基因是全长的，含有正确的起始密码子ＡＴＧ；ＣＪ－８０１ｂｋｆ与毒株Ｃｕｌ和ｐＢＧ９８同源性最高；ＣＪ－８０１ｂｋｆＶＰ２高可变区内两个亲水区的氨基酸顺序与ＣｕＩ、ＰＢＧ９８、５２／７０、００２－７３和ＳＴＣ完全相同；７肽区内第三个丝氨酸残基则变异为精氨酸。这些结果提示，中国ＣＪ－８０１ｂｋｆ毒株应属标准血清Ｉ型ＩＢＤＶ弱毒株。

ouble -stranded RNA of genomic segment A of the Chinese IBDV strain CJ -801bkf wasused as template to produce double0stranded cDNA by reverse-transcription.The cDNA genecoding for the host -protective antigen VP2 was amplified by polymerase chain reaction (PCR)and cloned . The nucleotide sequencing of the expected VP2 gene of 148bp was determined by Sanger’s DNA sequencing method ,and hence the amino acid sequence was deduced .The full-length cDNA gene of CJ0801bkf strain contains its initiation codon (ATG).Both the nucleotide sequence and amino acid sequence were compared with six published sequences of VP2 gene of IBDV strains including CuI ,pBG98,52/70,002-73,STC and variant E. It was shown that the CJ-801bkf strain was most closely related to the low -pathogenic strain CuI and non -pathogenic strain pBG98.Within the two hydrophilic regions of the variable region of VP2 ,in which the main antigenic sites might reside,the amino acid sequence were wholle conserved among all strains. However,in CJ-801bkf as well as in CuI and pBG98, a substitution from serine to arginine occurred in the heptapeptide which might be responsible for the pathogenicity of IBDV strains. These suggested that the Chinese CJ- 801bkf strain is a standard serotype I strain and has low pathogenicity