4株鸡传染性法氏囊病病毒VP2基因序列分析

试验从发病鸡场分离获得4株鸡传染性法氏囊病病毒（infectious bursal disease virus，IBDV），分别为河北株（HB）、湖北株（HUB）、山东株（SD）、山西株（SX）。通过特异性引物扩增VP2基因并进行测序，序列分析结果显示，4株病毒中，HUB、SD和SX的七肽区为S-W-S-A-S-G-S（aa 326S-332S），其222（A）、256（I）、294（I）和299（S）位是传染性法氏囊病病毒超强毒株（vvIBDV）的4个特征性氨基酸，确定这3株病毒均为超强毒株；而HB株七肽区为S-W-S-A-R-G-S（aa 326S-332S），其222（P）、256（V）、294（L）和299（N）位氨基酸显示该毒株属于弱毒株。进化树分析结果显示，HUB、SD和SX 3株病毒与2011年中国分离的大部分IBDV毒株亲缘关系较近，同源性在96%以上，同时与经典毒株Cro-Po/00、超强毒株GX和UK661亲缘关系很近；而HB株与减毒疫苗株D78株和B87株的亲缘关系近。本试验结果表明，IBDV目前在中国流行呈混发型，但以超强毒株为主。

Sequence Analysis of VP2 Gene of Four Infectious Bursal Disease Virus Strains

Four infectious bursal disease virus (IBDV) strains were isolated from Hebei (HB), Hubei (HUB), Shandong (SD) and Shanxi (SX), respectively. Gene analysis showed that the seven peptide areas of HUB, SD and SX were S-A-S-S-W-G-S (aa 326S to 332S), and 222(A), 256(I), 294(I) and 299(S) determined the three strains were vvIBDV. However, the seven peptide area of HB was S-W-S-A-R-G-S (aa 326S to 332S), 222(P), 256(V), 294(L) and 299(N), which showed HB was the weak strain. Evolutionary analysis indicated that HUB, SD and SX virus strains were located on the branch of vvIBDV and were similar with the most IBDV strains, which were isolated in 2011, the homologies were all above 96%. However, HB had close genetic distance with attenuated vaccine strains D78 and B87. IBDV was popular in the mixed style currently in China, but mainly was vvIBDV.