Newcastle disease (ND) is one of the most severe avian infectious disease inflicting a great loss on poultry industry worldwide. The control of ND relies on proper vaccination strategies. The vaccine strains of Newcastle disease virus (NDV) mainly belong to genotype I, II or III, which cannot fully prohibit virus shedding against the prevalent genotype VII virulent strain attack. To develop a safe, genotype matched vaccine candidate, we employed a bac-to-bac expression system and constructed a genotype VII NDV strain based virus-like particles (NDV VLPs). It was constructed with NDV M protein as the skeleton, and protective antigen F and HN proteins displayed on the surface. The NDV VLPs exhibited a similar appearance to the live NDV particles, but with denser F and HN proteins displayed on the surface. The immunization assay indicated that NDV VLPs stimulated a longer protection period, less tissue virus loading and shorter virus shedding period than the commercialized LaSota-formulated vaccine when challenged with genotype VII NDV strain. These results proposed the potential role of NDV VLPs as an alternative to current live genotype unmatched vaccine for the control and eliminate NDV in the avian flocks.

Newcastle disease (ND) is a highly contagious disease of poultry caused by Newcastle disease virus (NDV). Multiple genotypes of NDV have been circulating worldwide and NDV is continuously evolving, resulting into more diversity. Of multiple viral genotypes, VII is particularly important given that it had been associated with most recent ND outbreaks worldwide. In this study, an epidemiological investigation performed in northeastern China during 2014–2015 showed that 11 genotype VII isolates amounted to 55 percent in a total number of NDV isolates. Therefore, to evaluate the genetic diversity worldwide and epidemiological distribution in China of genotype VII NDV, a phylogenetic analysis based on the 1255 complete F gene sequences showed that VII is the most predominant genotype worldwide. A further detailed characterization on genotype VII was conducted based on the 477 complete F gene sequences from 11 isolates and 466 reference viruses available in GenBank. The results demonstrated that VII can be further divided into 8 sub-genotypes (VIIb, VIId–VIIj), indicating its complex genetic diversity. It is worthy of note that the isolation rate of VIIj is increasing recently. It emphasizes the necessity to pay close attention to the epidemiological dynamic of genotype VII NDV and highlights the importance of vaccination program.

利用昆虫细胞/杆状病毒表达载体系统,将已构建编码新城疫病毒(NDV)M、F和HN结构基因的3种单顺反子重组杆粒共感染悬浮培养的Sf9细胞以大量制备新城疫病毒样颗粒(ND VLPs).收集细胞培养上清经超速离心浓缩,蔗糖密度梯度纯化后,利用Western blot检测和透射电镜观察.结果显示,3种目的蛋白均正确表达且组装形成与原病毒粒子形态相似的颗粒,测定其血凝活性效价可达12log2.动物试验结果表明,与LaSota灭活油乳苗相比,将纯化后的病毒样颗粒以含25μg蛋白的剂量或联合佐剂免疫商品蛋鸡后能产生较高水平的HI抗体,且可有效减少攻毒鸡只口咽、泄殖腔途径的排毒时间,从而减少病毒在健康鸡群中的传播感染机会;表明所研制的基因Ⅶ型ND VLPs可作为疫苗候选株具有很大的防控优势.

通过比对新城疫病毒强、弱毒株F基因序列,根据其在F0裂解位点的差异以及F基因保守序列设计合成NDV-V-probe和NDV-L-probe探针组和NDV-F、NDV-R引物组,以基因Ⅶ型NA-1株和基因Ⅱ型LaSota疫苗株病毒RNA作为定量检测的标准品,建立检测方法.对所建立的标准曲线进行分析,相关系数R2均为0.997,线性关系良好.通过计算变异系数Cv/％分别为0.034％和0.027％,均小于1％,说明稳定性良好.对禽类常见病毒IBV、H9亚型AIV检测未发现有交叉反应,特异性好、重复性佳.结果表明:成功建立了新城疫病毒强、弱毒双重荧光定量RT-PCR的检测方法,实现了从分子水平上快速鉴别强、弱毒力的新城疫病毒,也可快速区分野毒感染动物和疫苗接种动物,减少不必要的经济损失.

利用Bac-to-Bac(R)昆虫-杆状病毒表达系统分别构建了含有新城疫强毒株M、F、NP和HN等4个结构基因的单顺反子重组杆粒,经转染后,观察S f9细胞病变以及PCR鉴定结果表明成功构建了4种重组杆状病毒;收集重组杆状病毒采用共感染策略,S f9细胞上清经超速离心,蔗糖密度梯度纯化与浓缩后,利用Western blotting方法和透射电子显微镜技术检测,结果表明目的蛋白均正确表达且组装成具有完整囊膜形态的病毒粒子.

设计2对引物分别用于新城疫强、弱毒的检测.使用强毒引物F1、R1可从NDV强毒株中特异性扩增出349bp的目的片段,使用弱毒引物F2、R2可从NDV弱毒株中特异性扩增出255 bp目的片段,该方法对H9亚型禽流感病毒(AIV)、传染性支气管炎病毒(IBV)和传染性法氏囊病毒(IBDV)的检测结果均为阴性.灵敏性试验结果显示,该方法对NDV强、弱毒株的最小检出量分别为1 pg和10 pg.利用该方法对7份临床样品进行检测,结果与测序结果一致,说明该方法可用于新城疫强、弱毒的快速鉴别诊断.