Injection immunization effect of inactivated large yellow croaker iridovirus vaccine on zebrafish

To study the immunological effect of inactivated large yellow croaker iridovirus (LYCIV) vaccine on zebrafish (Danio rerio), the fishes tested were divided into 4 groups (control group, inactivated virus group, adjuvant group, and vaccine group) and injected with cell culture solution, inactivated LYCIV, adjuvant and inactivated vaccine respectively. On the 21d post-immunization, each zebrafish was intraperitoneally injected with LYCIV at 5×10⁷ copies/fish. The expression levels of immune-related genes ifng, il1b, il12a, il2, mx, irf1, tlr9, myd88 and tnfa in the spleen and kidney tissues were determined by real-time quantitative PCR in 10 d, 21 dfand 35 d post-immunization. Results showed that the survival rates of control group, inactivated virus group, adjuvant group and vaccine group were 14.29%, 28.57%, 28.57%, and 42.86%, respectively. The survival rate of the vaccine group was significantly higher than that of the control group (P＜0.05) with a survival of 33.33 %. The genes ifng, il1b, il12a, mx, irf1, tlr9, myd88 and tnfa in the spleen tissue of vaccine group had significantly higher expression than those of the control, inactivated virus and adjuvant groups (P＜0.01). The expression of the genes ifng, il1b, il12a, mx, irf1, tlr9 and tnfa in kidney tissues of the fish in vaccine group were significantly higher than those in the control, inactivated virus and adjuvant groups on day 21 after immunization (P＜0.01). It indicates that the LYCIV inactivated vaccine prepared with Montanide^TM GEL 02 PR as adjuvant could improve the expression of interferon-related signaling molecules such as IFN-γ, IRF1, TLR9, MyD88 and inflammatory factors such as IL-1β in zebrafish besides the survival rate after infection.