Development Of Hybridization Among The Different Geographic E.tenella And Its Immunoprotecive To Chicken

Selection of parental strains for hybridization: Five strains of E.tenella isolated from different areas were compared on immunogenicity and immunoprotecive. The results showed that immunogenicity and immunoprotecive of three strains isolated from Guangzhou,Baodin and Changchun are better than those of other strains.Creation of analysis method by RAPD: The genomic DNA of Guangzhou strain,Baodin strain, Changchun strain and their filial generation were analysed by RAPD techique with 30 optimization primers screened from 200 primers. Genomic fingerprints by RAPD revealed a high degree of similarity (SI) among different strains. The average similarity of three different geographic strains is 0.6473,while average similarity between parental strain and filial generation is 0.9826. relationship tree was drawed by similarity, which showed relationship among the different strains. From above results, the method which based on RAPD was set up to identify the different geographic strains E.tenella.Cultivation of hybrid strain: Hybrid strain was cultivated by hybridization between Baodin strain and Changchun strain. Seventeen filial generations of hybridization were analysed by RAPD and relationship tree was drawed, the result showed that one of seventeen strains is obvious different from others. Similarity (Sl=0.7509~0.8564) between this strain and its parental strain is lower than that (81=0.9575-0.9911) between other strains and parental strain. According to relationship tree, this strain was regarded as hybrid strain (Fl strain) by Baodin strain and Changchun strain. In same way, F2 strain which hybrided by Guangzhou strain and Fl strain was definited.Immunoprotecive of hybrid strain: The chicken were inoculated with Fl and F2strain ,then challenged with the different strain. The results showed that there are better pathogenicity and immunogenicity in Fl and F2 strain, especially, chicken immuned by F2 strain has gained strong resistance against the different geographic strain infections, average protection rate is 84%. Chickens were immuned by Guangzhou strain,Baodin strain, Changchun strain,Fl strain and F2 strain and then withdrawaled to detect the level of CD4+ and CD8+ T cells. The result indicated that all strains can induce increasing quantity of CD4' and CD8+ T cells, changes are significant by F2 strain (p<0.05) .All above results are set up a basis for us to extremely study immunoprotecive mechanism of hybrid strain and find out the common protective antigen among different geographic E.tenella, so that we can prepare coccidial vaccine against different strains infection.