Aantigenicity And Genetic Variation Of Newcastle Disease Virus Isolated From Shandong Province

Newcastle (Newcastle disease, ND) is one of China’s most prominent disease hazards in the poultry industry. The death, respiratory symptoms and decreased egg production caused by ND are very common, even in chickens after repeated immunization. Therefore, to understand the epidemic dynamic of NDV, genetic characteristics and biological characteristics of grasp of China’s popular NDV, to explore the effect of virus antigenicity, formulate scientific and reasonable prevention measures, has important significance for the prevention and control of ND outbreak.Between2006to2013,55NDV isolates have been isolated and identified from different hosts in Shandong Province during the epidemiological surveillance of poultry. Then, fourty-nine NDV isolates which had successfully purified by plaque-purification in chicken embryo fibroblasts, were conducted and determined biological virulence include1-day-old chicks intracerebral pathogenicity index (ICPI), the minimum lethal dose lethal embryo mean death time (MDT) and6-week-old chickens intravenous pathogenicity index (IVPI). The results showed that55NDV, there are44of virulent, five moderate virulence, six of attenuated.. Through the different host red blood cell (RBC) agglutination tests showed that9strains isolated from duck and only6Chicken NDV genotype II NDV can agglutination four kinds of RBC, while other sources NDV from chicken and pigeon don’t have the character of agglutination horse RBC.Sequencing, genotyping and gene homology analysis were conducted on the F and HN genes of55isolates. The results showed that55strains belonged to four genotypes (Ⅱ, IX,Ⅵ, and Ⅶ),6isolates belonged to genotype Ⅱ,5strains (isolated from pigeon) to genotype VI,1isolate to IX, and the others to subtype Ⅶd. Amino acid sequence comparison confirmed that the strains between the same genotype with high homology, while homology rate of less than80%between genotype II LaSota strain and advantages. Meanwhile, even in the same genotype, there were still changes of point mutation accumulation, and this rule accompanied by an increase of more and more obvious. Genetic evolution analysis based on6coding genes and non-coding genes indicated that variation of NDV occurred throughout the genome.16epidemic NDV isolates and three classic strain (LaSota, Clone30and F48E9) were respectively prepared for definite factor positive sera by SPF chicken, and carried out the hemagglutination inhibition (HI) cross-reaction tests. The results showed that the relevant index of chickens popular genotype Ⅶ strains and LaSota is:0.31≤R≤0.66, confirmed pandemic strain were gradually deviated from antigenically LaSota vaccine strain. Protective efficacy tests proved that genotype VII strains immunohistochemistry symptoms, virus isolation rate and detoxification after the attack were significantly lower than the traditional vaccine (LaSota).In summary, the synchronous variation of the non-coding sequences and encoding genes results in the NDV molecular variation. Subtype Ⅶd NDVs are advantages epidemic stains in Shandong Province, with cumulative mutation of amino acids in functional F and HN genes; tradition LaSota vaccine and popular virus have appeared quite different antigenic, and genetic Ⅶd subtype vaccine have a better protection effect in inhibition of virus replication.