Study On The Recombinant Dna Vaccine Coexpressing Newcastle Disease Virus F Gene And Chicken Il-2

Newcastle disease(ND)is a severe respiratory, neurological, or enteric disease and is characterized with a high frequency of death among infected chickens. The study investigated the protection of chickens against the ND by a recombinant DNA vaccine. A plasmid vector encoding NDV F protein, which is required for virus cell fusion and is important for vaccine induced immunity, was used as a model to study how DNA may be modulated by the simultaneous expression of chicken IL-2.Firstly, cDNA encoding NDV F protein of avirulent NDV D26 strain was cloned into pcDNA3 which contains CMV promoter. Two-week-old SPF chickens were intramuscularlly vaccinated with the eukaryotic plasmid. Antibody response showed that the specific antibody to NDV could be detected after vaccination, the titer of antibody was very high when chickens survived from challenge. 30% vaccinated chickens survived.Vaccination of SPF chickens with F protein expression plasmid and chicken IL-2 expression plasmid was set in two ways, one is coinjection, the other is separate injection. Antibody and Th B cell responses showed that the humoral and cellular immunity of F and IL-2 plasmid vaccinated chickens significantly enhanced compared with those vaccinated with F protein expression plasmid alone. Six weeks later, All chickens were challenged with a lethal dose of NDV F48E9 strain, 40% chickens vaccinated by separate injection of two plasmids survived, 50% chickens vaccinated by coinjection survived. The enhanced immunity by adding IL-2 plasmid showed that IL-2 was expressed, and it really has adjuvant effect, the effect of IL-2 expressing plasmid was dependent on coinjection with the plasmid expressing antigen.To ensure that IL-2 was delivered at the sites of immune interaction, we constructed a coexpression plasmid. The NDV D26 strain F gene with CMV promoter and BGH polyA signal sequence was amplified by PCR from eukaryotic plasmid pcDNA-F, which contains the full-length NDV F gene, and cloned into reconstructed eukaryotic plasmid pcDNA-1L2, which contains chicken IL-2 gene. Restriction endonuclease cleavage and PCR amplification showed that a bicistronic plasmid encoding NDV F gene and chicken JL-2 separately was successfully constructed. Two-week-old SPF chickens were intramuscularly inoculated with the recombinant plasmid. Antibody andlymphocyte proliferative responses showed that the humoral and cellular immunity of chickens vaccinated with the recombinant plasmid greatly increased compared with those inoculated only plasmid expressing NDV F protein. After challenge with a lethal dose of NDV F48E9 strain, 70% chickens vaccinated recombinant plasmid survived, only 30% chickens vaccinated with plasmid expressing F protein survived. These results proved the adjuvant effect of chicken IL-2, and showed that the efficacy of a DNA vaccine can be greatly improved by simultaneous expression of IL-2.The tissue sections of thymus bursa of Fabricius and spleen of experimental chickens showed that the cortex of thymus of chickens immunized with DNA vaccine broadened, the white pulp of spleen of chickens immunized with DNA vaccine enlarged, the number of lymphocytes in these immune organs of immunized chickens increased significantly compared with control chickens. In the meantime, there were no gross and histologic lesion found in immune organs of chickens vaccinated with chicken IL-2 plasmid. These results demonstrated that inoculating IL-2 plasmid is not only effective, but also safe.Doctoral Student: Jiang YonghouAdvisors:Prof. Liu Zhonggui Prof. Tong GuangzhiMajor:Basic Veterinary...