Comparison Of Immunology Of HN Polypeptide Of Different NDV Strains

Newcastle disease(ND) is a highly contagious and economically important disease in poultry caused by Newcastle disease virus(NDV), the Avulavirus genus within the family Paramyxoviridae. Although control of ND by vaccination is widely practiced in poultry flocks, some researches have shown that vaccination against NDV does not eradicate periodic outbreaks of the ND in immunized poultry, the variation of NDV strain may be the major causes.NDV divided into nine genotypes, genotypesâ…¦,â…¨,â…¥are predominant in China, especially genotypeâ…¦. Amino acids of glycoproteins of genotypeâ…¦showed character changes compared with other genotypes, residues 65-75 of HN protein conserves in genotypeâ…¦but different with other genotypes, whether the difference is associated to the immunology are still uncertain. The main goal of the current study was to reseach the function of this conserved region, so the objective gene of five strains was cloned into vector pGEX-6p-1, the positive recombinant plasmid was selected by restriction enzyme digestion, PCR identification and sequencing, nominated as pGEX-GX-2,pGEX-F₄₈E₉,pGEX-La Sota,pGEX-A₄,pGEX-V₄.The expressed protein was analyzed by SDS-PAGE. The recombinant protein was presented as inclusion body and the molecular weight is 39 ku, After purified, the antigenicity of expressed proteins were identified by western Blot with F₄₈E₉, La Sota,GX-2,A₄ and V₄ strains anti-serum. The result showed recombinant proteins could reacted with anti-serum, but there exits slightly difference among different recombinant proteins.To identify and compare the immunogenicity of each recombinant protein, SPF chickens were immunized with purifying recombinant proteins, using mChIL-18 as adjuvant, challenged with F48E9, and serum was collected.NDV specific antibody titer was detected with ELISA. The results indicated that the group immunized with pGEX- F₄₈E₉ and mChIL-18 protein has the highest antibody titer among all immunized groups, with the protection of 50%, suggested that there are strain specific epitopes exist in each strain and existed immunogenic difference among different strains. There are three possible reasons for lower protection:first, when cloning the fragment, maybe we lost some important residues of protein. Second, the characteristic of prokaryotic expressed system can't provide the glycosylation, this may effect the antigenicity. Last, construction of recombinant protein after denaturation and renaturation could altered, this may effect the immunogenic. In our study, we also testified that IL-18 can enhance the level of antibody titer, and the selected peptide of HN protein may contribute to the immunogenicity of NDV.