鸡传染性法氏囊病病毒DK株VP2基因序列分析及其对SPF雏鸡的致病力

Sequence analysis of VP2 gene of chicken infectious bursal disease virus DK strain and its virulence evaluation in SPF chicks

为探究鸡传染性法氏囊病病毒(IBDV)DK分离株的致病性和遗传变异情况,本研究测定了该分离株的鸡胚半数致死量(ELD50)、对SFP雏鸡的致病力以及扩增病毒的VP2基因并分析其序列。结果显示,DK分离株对鸡胚的ELD50为104.5/0.2mL,以2×10^3ELD50剂量感染SFP雏鸡出现典型IBD的临床症状、剖检和组织学病变;实验鸡发病率为100%,致死率为44.4%;DK株VP2基因序列与参考株的同源性为93.1%~97.0%、氨基酸序列同源性为93.6%~97.5%,其基因序列和氨基酸序列均与Cu-1wt参考株(经典株)同源性最高;DK株VP2氨基酸序列的七肽区SASWSGS及249Q、253Q、279D、284A、290M、313V、330S氨基酸位点均与强毒株的氨基酸位点一致;但其222P、256V、299N3个氨基酸不符合IBDV超强毒株的特征;而其第222、249位氨基酸为P和Q,与抗原变异株(vIBDV)的T和K也不相同。结果表明:IBDVDK株为中等偏强毒力病毒。本研究为IBD的防控提供参考依据。

To investigate the pathogenicity and genetic variation of the infectious bursal disease virus(IBDV)DK isolate,the IBDV isolate was further characterized by the half-lethal dose of chicken embryos(ELD50)measurment,the pathogenicity evaluation,and the VP2 gene sequence analysis.The results showed that the ELD50 of the DK isolate was 10-4.5/0.2mL.All the SFP chicks artificially infected with 2×10^3 ELD50 of the virus isolate showed clinical symptoms,necropsy and histological lesions,and the mortality rate was 44.4%.In addition,the VP2 gene sequence of DK isolate had 93.1%to 97%homology with the reference strains,and the homology of the amino acid sequence was 93.6%to 97.5%,which had the highest homology with the Cu-1wt reference strain(classic IBDV).The SASWSGS heptapeptide region and 249Q,253Q,279D,284A,290M,313V and 330S amino acid positions of the VP2 were all consistent with the amino acid positions of the virulent IBDV strain.However,the three amino acid positions of 222P,256V and 299N were not consistent with the characteristics of the very virulent IBDV strain.And its amino acids at the positions of 222 and 249 were P and Q,which were different from those of T and K of antigen mutant(vIBDV).The results showed that the DK isolate was a virulent IBDV and the its virulent was relatively higher than that of the classical IBDV.This study provided a reference for the prevention and control of IBD.