表达流行毒株VP2蛋白的IBDV重组疫苗株rGtHLJVP2的构建及其免疫效力的评价

Construction and immunological evaluation of rGtHLJVP2 expressing VP2 protein of prevalent infectious bursal disease virus strain HLJ0504

为应对传染性法氏囊病病毒(IBDV)变异毒株及超强毒株(vvIBDV)等突发疫情的出现,解决传统疫苗株筛选费时费力的难题,在流行病学调查的基础上,克隆了超强毒株HLJ0504的VP2基因,并突变细胞嗜性决定氨基酸位点(Q253H/A284T),用其替换IBDV弱毒株Gt基因组的相应区段,成功获得1株表达流行vvIBDV VP2蛋白的重组病毒rGtHLJVP2。体内、外复制动力学研究表明,该重组病毒与亲本病毒Gt的复制能力相当。动物试验结果表明,该重组病毒对接种鸡无明显致病性,接种鸡法氏囊指数均在0.7以上,法氏囊无明显萎缩现象。该重组病毒可以诱导机体产生良好的免疫应答,其抗体水平明显高于亲本毒,能够完全抵抗vvIBDV的攻击。另外,该重组病毒具有良好的遗传稳定性。本研究结果为新型传染性法氏囊病疫苗的研发奠定了基础,对于IBDV突发疫情的应急防控具有重要意义。

In response to the emergency of variant and very virulent infectious bursal disease virus(IBDV)strains and to solve the problem of time-consuming in screening of the conventional live vaccines,a recombinant virus rGtHLJVP2was generated based on the epidemiological investigation with its VP2gene cloned from a prevalent very virulent IBDV(vvIBDV)strain HLJ0504.To adapt this virus to CEF cells,two mutations of Q253Hand A284Twere introduced in its VP2gene.It was then used to replace the corresponding region of the attenuated IBDV vaccine strain Gt.The constructed virus rGtHLJVP2had comparable replication ability to its parental virus Gt in vitro and in vivo.The animal experiments showed that rGtHLJVP2had no pathogenicity in chickens with bursa index above 0.7and no significant bursal atrophy.The recombinant virus induced a good immune response with the antibody titer significantly higher than that induced by the parental virus Gt,and it provided full protection against vvIBDV challenge.In addition,the recombinant virus rGtHLJVP2had good genetic stability.This study provides the solid foundation for the development of IBD vaccines and is significant for the prevention of IBDV infection.