Abstract:

This experiment was conducted to study the immune protection effect of a Recombinant Pseudotype Baculovirus expressing the Sl protein of infectious bronchitis virus. Sixty-six 7-dayold SPF chickens were randomly divided into 6 groups, and were inoculated with Ac-V-EGFP (2×10⁹ pfu), Ac-V-S1, ^poly156S1 subunit vaccine, commercialized inactivated vaccine (M41) and PBS (control) respectively, boosted immunization was conducted at day 21. The results showed that, in the humoral immune, the inactivated vaccine group induced the highest level of IBV-specific ELISA antibody, significantly higher than other groups(P<0.01), in turn were prime-boost group and the Ac-V-S1 group; in cellular immunity, the Ac-V-S1 immunized group showed significantly higher than other groups(P<0.01), in turn were prime-boost group and the wild-type baculovirus group. Two weeks after the second immunization, the chickens were challenged with IBV M41 strain. The post-challenge results showed that the protective rate of Ac-V-S1, Ac-V-EGFP, and ^poly156S1 subunit vaccine were 55%(6/11), 27%(3/11), 37%(4/11), respectively, and the protective rate of the prime-boost immunity group was 64%(7/11), a little lower than the regular inactivated vaccine group 73%(8/11). Results demonstrated that the recombinant baculovirus Ac-V-S1 showed better effects on cellular immunity, which can make up for deficiencies in humoral immunity, and the prime-boost immunization strategy can further enhance the immune effect of recombinant baculovirus. This study laid the foundation of the research of recombinant baculovirus as genetic engineering vaccine of IBV.