Identification And Immunity Comparison Of NDV F₄₈E₉ And La Sota Strain Specific B Cell Epitopes

Newcastle disease virus (NDV) causes a highly contagious and economically important disease in poultry. Immunization of poultry against ND is the most effective method to prevent its prevalence, however some researches have shown that vaccination against NDV does not eradicate periodic outbreaks of the disease in immunized poultry, the variation of NDV may play a major role. This project was done to understand the antigenic differenc between isolate and vaccine NDV, explain the relationship of variation and protection.NDV F₄₈E₉ strain belongs to an unique DC genogroup which consist of NDV isolated form China only in near 60 years,and La Sota was one of the most popular vaccine strain.there are much difference between current vaccine and unique genotype â…¨ in their biology, serology and genetics. So they are the best model for us to clarify the difference between isolates and vaccine of NDV.The virulence of NDV is mainly related to F and HN protein,main glycoproteins of NDV,and they are the main immunogens that induce protective protection against ND too. Consider of its important role in NDV pathogenisis and immunity, we select F protein as target protein. In proteins,the epitope is a basic unit of functional analysis;it is a distinguishable antigenic site.To compare the antiginicity difference of F protein, epitope identification is the powerful technique. We compared the difference between antigen epitopes activation of F protein of F₄₈E₉ and La Sota strain. B cell-epitopes on F protein of NDV F₄₈E₉ and La Sota vaccine strain were predicted by Hydropphilicity,Flexibility, Accessilility,Antigenicity and Secondary structure index.At the same time,the potential of mChIL-18 protein were tested as adjuvant for polypeptide vaccine.To identify and compare the predicted B cell-epitopes between NDV F₄₈E₉ and La Sota strain, we cloned 4 genes cDNA segments (P1, P2, P5and P6) that encoded predicted epitopes, and constructed Prokar-yotic vector which expressed peptides separately. 8 recombinant peptides expressed in E.coli were analyzed by SDS-PAGE, it was proved that molecular weight of four peptides segments P1, P2, P5and P6 are 8.0 KD, 10.8KD, 13.5KD, 10.5KD respectively. The Antigenicity of expressed peptides were identified by western blot with anti- F₄₈E₉ and anti-La Sota strains serum. The results showed that peptides P1, P2, P5 and P6 of NDV F₄₈E₉ and La Sota could reacted with both anti-serum. However,the western blot of pepti de P5 with F₄₈E₉ and La Sota antiserum showed a strain specific reaction. Then we purified P5 ploype ptide and mChIL-18 protein by Ni-NTA Resin. Using mChIL-18 as adjuvant,immunized SPF chickens with P5 peptide of F₄₈E₉ or La Sota, serum were collected and NDV specific antibody titers were detected with ELISA.The results indicated that F₄₈E₉ P5 peptide (FP5) in combination with mChIL-18 protein has the highest antibody titer among all immunized groups,and it is the only group that could protect some of immunized chicken from death (20%).Finding of immunogenic difference between FP5 peptide and LP5...