Protection of chickens against infectious bronchitis virus with a multivalent DNA vaccine and boosting with an inactivated vaccine

Yan, Fang; Zhao, Yujun; Hu, Yongting; Qiu, Jianyang; Lei, Wenxin; Ji, Wenhui; Li, Xuying; Wu, Qian; Shi, Xiumin; Li, Zhong

Kinetic changes in A 570 values for the animals are shown in Fig. 3 . Data are expressed as the mean OD 570 values ± SD (n = 5). Columns are labeled with letters. Different letters indicate statistically significance differences (p ＜ 0.01) between different treatments within the time point while columns with the same letters indicate that no significantly differences (p > 0.05) were observed. Absence of a letter indicates that there were no significant differences (p > 0.05) between any of the time points. Similar to the antibody responses we observed, PBMC proliferation in response to IBV and ConA stimulation was also observed in chickens immunized with pVAX1-16S1, pVAX1-16M, pVAX1-16N, and pVAX1-16S1/M/N on day 21 and further increased on day 35. A 570 values for the monovalent and multivalent groups were much higher than those for the pVAX1 DNA vector control and inactivated vaccine groups when the birds were 35 days old. The A 570 values for the chicken immunized with the pVAX1-16N construct were higher than those for birds immunized with the pVAX1-16S1 or pVAX1-16M constructs (p ＜ 0.01). On day 49, proliferative responses of the pVAX1-16S1/M/N and pVAX1-16S1/M/N + inactivated vaccine groups were significantly higher than those of the other groups (p ＜ 0.01). These results indicate that immunization with a combination of the three-gene DNA vaccine and an inactivated vaccine not only elicited the strongest antibody response, but also induced the highest IBV-specific cellular proliferation rates in the chickens. The responses of all experimental groups to stimulation with ConA were similar to ones provoked by IBV (data not shown).