野生水禽源ClassⅠ新城疫病毒对SPF鸡的致病性研究

Research on Pathogenicity of SPF Chicken Infected with a ClassⅠ NDV Isolated from Waterfowl

为了科学地了解新城疫病毒(NDV)的遗传进化规律,本研究对从鹭科候鸟分离的NDV毒株SD22/13的生物学特性和致病特性进行了研究。通过致病性指数测定和交叉血凝抑制试验测定分离株SD22/13的毒力及与LaSota疫苗株、基因Ⅶ型NDV毒株的抗原相关性,同时设计引物对F基因进行克隆测序和遗传进化分析,并对其在SPF鸡上的致病性进行评价。生物学特性和遗传进化分析显示SD22/13属于ClassⅠ分支基因3型,与LaSota疫苗株的抗原相关性为56.1%,与基因Ⅶ型强毒株的抗原相关性低于50%。致病性试验结果表明该毒株可在鸡体内较好复制,并刺激机体产生较高水平血清抗体,鸡的免疫器官和肾虽均有轻微的病理损伤,但无发病死亡,对试验鸡致病性较低;SD22/13感染后30d,再以基因Ⅶ型强毒株攻毒,在10d观察期内SD22/13感染组鸡均健康,无发病死亡,而对照组鸡至第5天时全部死亡。本研究结果表明分离株SD22/13在生物学特性、抗原性和对SPF鸡致病性方面与基因Ⅶ型NDV存在明显差异;虽然SD22/13与基因Ⅶ强毒株抗原相关性较低,不能阻止其排毒,却能完全保护鸡抵抗强毒株的攻击。

A lentogenic Newcastle disease virus(NDV),SD22/13,was isolated from heron.The biology and pathogenicity were characterized in order to understand the evolution of NDV better.Fgene of SD22/13 was sequenced and compared with that of reference strains.The antigenicity of the virus was compared with that of LaSota and other genotypeⅦ virulent NDV strains via cross hemagglutination inhibition(HI).The pathogenicity of SD22/13 to SPF chicken was also conducted.The results indicated that SD22/13 was classified as a class Ⅰ genotype 3NDV based on a partial sequence of the F gene.The antigenicity correlation between SD22/13 and LaSota was56.1%,and the correlation of which with genotype Ⅶ NDV strains was less than 50%.Experiments on animals demonstrate that the isolate SD22/13 can replicate well in SPF chicken and induce a high immune antibody and had slight pathogenic to immune organ and kidney.Chickens inoculated with SD22/13 were challenged with genotype Ⅶ virulence NDV strain on 30 dpi,andthere had no death in chickens infected with SD22/13.The results demonstrated that SD22/13 stain had significant differences with genotypeⅦ NDV in biological characterization and pathogenic to chickens.Although the antigenic correlation was low between SD22/13 and genotype ⅦNDV,class I viruses can provide 100% protection rate,but it cannot block virus shedding upon challenge with genotypeⅦ virulent NDV.