β-glucan and anisodamine can enhance the immersion immune efficacy of inactivated cyprinid herpesvirus 2 vaccine in Carassius auratus gibelio

Abstract

As one of the most important fish in freshwater aquaculture, gibel carp (Carassius auratus gibelio) is easily susceptible to Cyprinid herpesvirus 2 (CyHV-2). Immersion vaccination has attracted many researchers due to its simple operation in preventing infectious diseases. However, the unavoidable disadvantage is that the immersion vaccine must be used with adjuvants to get a better performance. In this study, gibel carps were vaccinated by a 60 min bath in a β-propiolactone-inactivated Cyprinid herpesvirus 2, mixed with DTT, β-glucan, anisodamine and scopolamine, respectively. After immunization, the fishs were challenged by CyHV-2 in 2 weeks. By analyzing pathological section, we found that β-glucan, anisodamine and scopolamine groups protected the gibel carp compared to the control group, which was consistent with the trend of survival rate. Specifically, β-glucan group in serum appeared best on lysozyme, TSOD and complement C3. Real time quantitative RT-PCR results demonstrated that in both spleen and head kidney tissues, mRNA expressions of typical Th1 immune response cytokines IL-2 and IFN-γ2 in β-glucan group and anisodamine group were significantly higher than other groups and the level of immunoglobulins related to systemic immunity (IgM) and mucosal immunity (IgZ) were also enhanced in the immune period. DTT group slightly affected immune gene and serum enzyme activity, while did not show an adjuvant effect on survival rate. In addition, four adjuvant groups could obviously inhibit CyHV-2 replication. This study explored and proved the good efficiency of β-glucan or anisodamine as immersion immune adjuvant and also provided reference for improving the efficiency of immersion immunity.