3株鸽源新城疫病毒的分子特征及对鸽的致病性

2011―2013年在新城疫流行病学调查中分离到3株鸽源新城疫病毒(SDS,SD01和SD02),为了进一步了解其生物学特性和遗传进化规律,对3株病毒进行了测序和生物活性分析,并对分离株SDS对鸽的致病性进行了评价。结果表明,毒株SDS基因组全长为15192 bp,基因排列方式为3′-NP-P-M-F-HN-L-5′,3个分离株F蛋白裂解位点氨基酸序列均为¹¹²RRQKRF¹¹⁷,具有典型的新城疫强毒的分子特征。系统进化分析表明这3个毒株与基因Ⅵ型NDV毒株聚于一簇,属于ClassⅡ系Ⅵb基因型。3个分离株F蛋白的融合肽和七肽重复区,HN蛋白的抗原中和表位存在多处突变,与单克隆抗体1E5、2F10的反应性也发生改变,表明3个分离株与疫苗株LaSota有明显的抗原差异。SDS攻毒试验结果显示,试验鸽自攻毒后5 d出现明显的临床症状,滴鼻组和肌肉注射组的死亡率分别为60%和70%;病死鸽剖检可见脑膜充血出血,腺胃乳头、腺胃肌胃交界及肠道出血,肝脏肿大,脾有淤血斑。滴鼻组在攻毒后5~14 d于喉头和泄殖腔检出排毒,而肌肉注射组在攻毒后3~14 d于喉头和泄殖腔有排毒。

Molecular characteristics of three strains of pigeon Newcastle disease virus and its pathogenicity to pigeon

In order to determine the phylogenetic and evolution characteristics of Newcastle disease virus(NDV)circulating in pigeons of China in recent years,three pigeon NDV(SDS,SD01 and SD02)isolated from pigeons during the surveillance from 2011 to 2013 were sequenced and analyzed and the pathogenicity of SDS isolate to pigeons was evaluated.The complete genome of SDS was 15192 nucleotides with the gene order of 3′-NP-P-M-F-HN-L-5′.All the isolate had the same motif of¹¹²RRQKRF¹¹⁷at the cleavage site of F protein,which was typical of velogenic Newcastle disease virus(NDV).Phylogenetic analysis based on variable region(nucleotide 47 to 420)of the F gene revealed that all isolates belonged to genotypeⅥin classⅡ,and were placed into sub-genotypeⅥb.Several mutations were identified in the functional domains of F and HN proteins,including fusion peptide,heptad repeat region and neutralizing epitopes.The obvious antigenic difference between PPMV-1 isolates and LaSota strain was found based on the cell neutralization test of monoclonal antibody 1 E5 and 2 F10.Animal experiments with SDS isolate indicated that the infected pigeons showed obvious clinical symptoms on the 5 th day post infection,and the mortality of the nasal drop group and the muscle injection group were 60%and 70%,respectively.Autopsy of the diseased dead pigeon showed cerebral hyperemia and hemorrhage,glandular gastric papilla,glandular gastric and muscle gastric junction,and intestinal bleeding,liver enlargement,and spleen with blood stasis.Virus shedding could be detected in the larynx and cloaca of infected pigeons in nasal drip group from 5 to 14 days after challenge,while virus shedding was detected in the intramuscular injection group from 3 to 14 days after infection.The results indicated that Newcastle disease virus prevalent in pigeons was mainly genotypeⅥb,which was popular in China in recent years.There were several mutations at the neutralizing epitopes of hemagglutinin-neuraminidase(HN)of the three isolates,suggesting that the current vaccine may cause immune failure.SDS isolate had highly pathogenic to pigeons,and the mortality rate was 60%-70%with virus shedding14 dafter infection,indicating that the current epidemic of pigeon Newcastle disease virus posed a certain threat to the prevention and control of Newcastle disease.