新城疫病毒弱毒骨架表达强毒F基因的重组病毒生物学特性研究

为了解目前中国新城疫病毒（Newcastle disease virus,NDV）优势基因VIId型的毒力机制,应用反向遗传技术将我国优势流行基因VIId型强毒株I4的F基因替换弱毒LX的F基因,获得表达NDV强毒株I4F基因的重组病毒NDV/LX-If。测定重组病毒的致病指数和组织分布,结果发现,重组病毒NDV/LX-If毒力比骨架病毒有了显著的提高。NDV/LX-If的鸡胚平均致死时间（mean death time,MDT）为56 h,雏鸡脑内接种致病指数（intracebral pathogenicity index,ICPI）为1.49,属于中等毒力,毒力比亲本病毒毒力低,但都能使自然途径感染的鸡100%死亡,同时获得了亲本毒株的组织嗜性。可见,新城疫病毒F基因是毒力和组织嗜性的主要决定因素,但是其它基因对新城疫病毒的毒力也可以产生影响。

CHARACTERIZATION OF A RECOMBINANT LENTOGENIC NEWCASTLE DISEASE VIRUS EXPRESSING F GENE OF VELOGENIC ORIGIN

The F gene of avirulent strain LX of genotype VIId Newcastle disease virus（NDV） was replaced by the F gene of virulent strain I4 by using reverse genetics technique,resulting in a recombinant virus NDV/LX-If.The pathogenicity and tissue tropism of the recombinant virus were examined in SPF chickens by natural infection route.The recombinant NDV/LX-If demonstrated a significant increase in virulence as compared with the original strain LX.The NDV/LX-If had MDT of 56 hours and ICPI of 1.49.When inoculated into SPF chickens via natural route,NDV/LX-If caused 100% morbidity and mortality and showed the same tissue tropism as the original virulent strain I4.The replacement of F gene in recombinant virus NDV/LX-If remarkably increased its virulence and altered its tissue tropism,suggesting that F gene is a major determinant of NDV virulence.