鸡传染性法氏囊病病毒B节段对病毒致病性的影响

Segment B of infectious bursal disease virus contributes to viral virulence

为研究鸡传染性法氏囊病病毒(IBDV)3个不同亚群B节段对病毒致病性的影响,本实验将IBDV HLJ0504超强毒株的A节段分别与3个亚群(Ⅰ亚群Gt株、Ⅱ亚群HLJ0504株及Ⅲ亚群HuB-1株)B节段进行组合,拯救了rH4AGtB、rH4AH4B和rH4AHuB3种重组病毒。动物实验结果表明,rH4AHuB引起雏鸡死亡率为80%、rH4AH4B次之为73.3%、rH4AGtB仅为33.3%。此外,rH4AHuB在体内复制的能力明显高于rH4AGtB(p<0.05),但与rH4AH4B无明显差异(p>0.05)。以上结果表明,IBDV B节段影响病毒的致病性,不同亚群B节段对IBDV致病性的影响作用不同。其中,第II、III亚群的B节段能够提高病毒在体内的复制能力,从而使IBDV的致病性增强,而第I亚群的B节段则降低了病毒在体内的复制能力,使IBDV的致病性减弱。

To study the impact of different subgroups of segment B on the virulence of infectious bursal disease virus （IBDV）, three recombinant IBDVs, named rH4AGtB, rH4AH4B and rH4AHuB were rescued by using the reverse genetic system which contained the segment A from wlBDV strain HLJ0504 and the segments B from different subgroup strains （attenuated Gt strain of subgroup Ⅰ, vvIBDV HLJ0504 strain of subgroup Ⅱ, and vvIBDV HUB-1 strain of subgroup Ⅲ）. The pathogenicity test results showed that the rH4AHuB caused a mortality of 80% which was higher than that of rH4AH4B （73.3%）. The rH4AGtB containing the attenuated segment B caused the lowest mortality of 33.3%. The viral loads of rH4AHuB in the bursal of infected chickens were significantly higher than that of rH4AGtB （p〈0.05）, but no significant difference with rH4AH4B （p〉0.05）. These results indicated that the different subgroups of segment B showed an impact on the viral virulence. The segment B from Ⅱ and Ⅲsubgroups had a positive effect on the viral replication and virulence in vivo, while the segment B from the subgroup Ⅰattenuated strains showed a negative effect on the viral replication and virulence.