CONSTRUCTION AND IMMUNOGENICITY OF A MULTI-EPITOPE DNA VACCINE AGAINST INFECTIOUS BRONCHITIS VIRUS IN CHICKENS

The T cell epitope box of structural protein S1 gene of avian Infectious bronchitis virus(IBV) and B cell epitopes of Australia T strain and M41 strain S1 gene were cloned into the eukaryotic expression vector p VAX1, constructing five groups of eukaryotic expression plasmids: p VAX-S1T+M, p VAX-S1B-M41, p VAX-S1B-T, p VAX-S1T+S1B-M41 and p VAX-S1T+S1B-T. The plasmid solution from each group was administered to 7-days-old chickens via intramuscular route. Three weeks later, chickens were boosted with the same doses of DNA vaccines. Chickens receiving PBS served as controls. Blood samples were taken at 0, 7, 14 and 21 days post the fi rst vaccination and 10 days post the second vaccination. Anti-IBV specifi c antibodies were measured in indirect ELISA. At 10 days post the second vaccination, chickens were challenged with virulent IBV strains. The result showed that antibody titers of chickens immunized with p VAX-S1, p VAX-S1T+M and p VAX-S1B-T were signifi cantly higher(P 0.01) than that of control group. The protection against the challenge was achieved in 75% chickens administered with p VAX-S1 and p VAX-S1B-T. In conclusion, the present study provided a new strategy to enhance the protection of IBV DNA vaccine.