The Exploration For DNA Immunization Against Avian Infectious Bursal Disease And Infectious Bronchitis

The experiment was carried out to explore DNA vaccination against chicken infectious busal disease(IBD). VP2 gene cDNA originating from IBDV D78 strain by RT-PCR was sequenced to confirm the ORF contact firstly, and then insert into pCI multiple clone site at downstream of CMV promoter-enhancer-intron and upstream of SV40 polyA signal to form VP2 expressive plasmid pCIVP2. Following amplified in E. coli, pCIVP2 was extracted by alkaline lysis and purified by PEG-8000, and soluted in PBS for DNA vaccination. 17 three week old chickens were divided into two groups, 11 for immune test inoculated with pCIVP2 100ug per chicken intramuscularly, 6 for control inoculated with pCI 100ug per chicken intramuscularly, and boosted with same dose after 2 weeks. At 4 weeks after priming, both group chickens were bled for VN antibody detects and challenged with 10² ELD₅₀ vvIBDV G strain. All survival chickens also were bled for VN test at 8 days post challenge.Results, although every chicken in both group showed clinical sign at 3 days post challenge, the mortality was much different between pCIVP2 vaccinated and control, i.e. 1/11 and 5/6 respectively. The observation of gross and histology revealed there was more serious bursal atrophy and follicle lymphocyte delete occurred in control survival chicken than pCIVP2 vaccinated survival chickens. VN antibody test also yielded different titers at pre-challenge between pCIVP2 group and control with the 10^1.5 of former and negative of later. These results strongly indicated that pCIVP2 DNA immunization elicits VN antibody and immune protection against vvIBDV challenge, though failure to prevent clinic sign and bursal lesion. This experiment was conducted to explore DNA vaccination against chicken infectious bronchitis(IB). S1 gene cDNA originating from a M41 like isolates by RT-PCR was sequenced to confirm the ORF contact firstly, and then insert into pCI multiple clone site at downstream of CMV promoter-enhancer-intron and upstream of SV40 polyA signal to form S1 expressive plasmid pCIS1. Following amplified in E. coli, pCIS1 was extracted by alkaline lysis and purified by PEG-8000, and soluted in PBS for DNA vaccination. 11 one week old chickens were divided into two groups, 6 for immune test inoculated with pCIS1 100ug per chicken intramuscularly, 5 for control inoculated with pCI 100ug per chicken intramuscularly, and boosted with same dose after 2 weeks. At 4 weeks after priming, both group chickens were bled for VN antibody detects and challenged with 10² ELD₅₀ IBV H52. Also, tracheal-cloacal swabs for virus isolation and second blooding for VN test were sampled at 4 days post challenge and 7 days post challenge respectively. Virus isolation revealed all control chicken(5/5) positive while only one pCIS1 inoculated chicken(1/6) positive. In contrast to control group chickens with no detectable VN antibody, the lower VN antibody could be detected in immune test chicken. These results indicated that pCIS1 DNA immunization elicits VN antibody to IBV and prevents IBV shedding from infectious chicken.