三株新城疫病毒强毒株的生物学特性及全基因组序列分析

2009～2011年从北方发病鸡群和鸭群中分离出3株新城疫病毒（Newcastle disease virus,NDV）。通过致病性指数测定及交叉血凝抑制试验初步分析了3个毒株的毒力和相互之间的同源性。选取鸡源分离株SDLY01与新城疫疫苗株（LaSota）进行了交叉保护试验,选取鸭源毒株SD03对樱桃谷鸭进行攻毒实验,同时设计引物对3个毒株进行了全基因组测序,并与36株NDV参考株进行了分子进化分析。结果表明3个分离株F蛋白裂解位点的氨基酸序列均为112R-R-Q-K-R-F117符合强毒株的序列特征,并与致病性指数测定结果相符。交叉血凝抑制试验发现3个分离株与疫苗株LaSota 的抗原同源性较低为82.5%～89.4%,两个鸡源分离株间的抗原同源性为90%,而鸭源毒株SD03与鸡源毒株SDSG01同源性为100%。交叉保护试验和攻毒实验结果显示传统的LaSota疫苗能对SDLY01流行株提供100%免疫保护,但第5天仍检测到排毒;鸭源毒株SD03对樱桃谷鸭不致病,但能检出排毒,排毒期最长为5d。全基因组测序与分析表明3个毒株基因组长度均为15192bp,属于基因Ⅶd型毒株,与同期流行的鹅源及鸭源NDV毒株之间全基因组核苷酸序列具有高度的同源性,揭示鸭源、鹅源NDV与鸡源NDV在遗传学和流行病学上密切相关。

Biological characteristics of three Newcastle disease virus isolates and entire genome sequences analysis

Three Newcastle disease virus (NDV) strains recovered from ND outbreaks in chickens and duck flocks in north china during 2009 to 2011 were completely sequenced and biologically characterized. All the strains were velogenic and had the velogenic motif 112R-R-Q-K-R-F117 which was consistent with the results of biological tests. Analysis of the variable region (nucleotide 47 to 420) of the F gene indicated that the three isolates belonged to genotype VII d. Cross hemagglutination inhibition test indicated that the antigen homology between three isolates and LaSota were 82.5%-89.4%, the homology between the two isolates from chicken was 90%. A cross-protection experiment in which specific-pathogen-free chickens vaccinated with LaSota were challenged by SDLY01 isolate showed that LaSota vaccine could provide complete protection against SDLY01, however virus discharge could be detected on fifth day. Challenge experiment in which Cherry Valley duck of 30 day old challenged with SD03 strain indicated that cherry valley duck had no disease in experiment period, but virus discharge could be detected from Larynx and cloaca until fifth day. Genome length of three NDV isolates was 15192bp and belonged to genotype VII d. Sequence analysis clarified that the whole genomic sequence of these three isolates shared high homology with NDV virus strains isolated from goose and duck over the same period, which elucidated that NDV isolated from goose, duck or chicken had close genetics and epidemiological relationship.