Generation of recombinant Newcastle Disease virus LaSota vaccine strain expressing VP2 gene of very virulent infectious bursal disease virus isolated from cDNA clone

Китайский. 重组新城疫病毒（newcastle disease virus，NDV）作为新型的活病毒载体疫苗具有巨大的优势和应用前景,本研究旨在探讨新城疫病毒作为防制传染性法氏囊病超强毒（very virulent infectious bursal disease virus，vvIBDV）及新城疫重组二联活病毒载体疫苗的可行性。采用单股负链RNA病毒反向遗传操作技术，救获野生型NDV LaSota疫苗株rLaSota及表达vvIBDV Gx株VP2基因的重组疫苗株rLaSota-VP2，分别经滴鼻点眼途径免疫SPF雏鸡，免疫后21 d分别以vvIBDV Gx超强毒和新城疫强毒进行攻击。rLaSota及表达vvIBDV－VP2基因平均鸡胚致死时间均大于120 h，脑内致病指数（ICPI）分别为0.4和0.36，静脉内致病指数（IVPI）均为0；接种后72～96 h每毫升尿囊液EID50则分别达到109.0以上。rLaSota-VP2以106.0 EID50一次免疫7日龄SPF鸡雏，免疫后3周对新城疫强毒致死攻击100％保护，对vvIBDV攻击免疫保护率达90％以上。重组病毒rLaSota-VP2保持了LaSota亲本疫苗株高滴度的鸡胚生长特性和低致病性及遗传稳定性，免疫雏鸡对新城疫强毒和传染性法氏囊病毒超强毒株的致死均形成有效免疫保护。本研究为研制传染性法氏囊病－新城疫重组二联活载体疫苗奠定了基础。

Английский. Newcastle disease virus (NDV) is the promising and suitable live vaccine vector for the control and prevention of infectious diseases in poultry. In this study, the reverse genetic system for NDV vaccine LaSota strain was established. The gene encoding the VP2 protein of the very virulent infectious bursal disease virus (vvIBDV) Gx strain was inserted into the locus between P and M of in full-length genomic cDNA of NDV LaSota for expression. The recombinant NDV expressing VP2 protein, rLaSota-VP2, was rescued from genomic cDNA clone. Recombinant rLaSota-VP2 replicated to a titer similar to that of parental NDV strain LaSota in chicken embryoes and kept the low pathogenicity similar with LaSota vaccine strain. One time vaccinated in 7-day old specific-pathogen-free chickens with rLaSota-VP2 provided completely protection against a highly virulent NDV strain F48E9 and over 90% protection against vvIBDV Gx strain at three weeks post-vaccination. These results indicate that recombinant Newcastle disease virus LaSota vaccine strain expressing VP2 gene of very virulent infectious bursal disease virus can be used as a live bivalent vaccine against NDV and vvIBDV.