Abstract:The aim of this study was to explore the immunoprotective mechanism and protective effects of oral specific egg yolk immunoglobulin (IgY) against white spot syndrome virus (WSSV) infection in Pacific white shrimp (Litopenaeus vannamei). Different doses of WSSV IgY agent (0, 0.2%, and 0.5%) were added to shrimp feeds and administered to juvenile L. vannamei for 28 days. The survival rate of juveniles was measured within 14 days of artificial infection with WSSV. The activity of immune enzymes and the relative expression levels of immune genes in shrimp hepatopancreas were measured after 3 days of WSSV infection. The results showed that compared with the control group without IgY, the 0.2% IgY agent group showed significantly higher enzyme activity by superoxide dismutase (SOD) and phenoloxidase (PO), and significantly lower enzyme activity by acid phosphatase (ACP) and alkaline phosphatase (AKP). The relative expression level of heat shock protein 70 gene (Hsp70) also significantly increased, while the relative expression levels of lectin gene (lectin) and β-1,3-glucan binding protein-lipoprotein gene (β-GBP-HDL) significantly decreased in the 0.2% IgY agent group. SOD activity significantly increased while PO activity did not change significantly, while ACP and AKP activities decreased in the 0.5% IgY agent group. The relative expression level of Hsp70 also significantly increased, and the relative expression level of lectin did not significantly change, while the relative expression level of β-GBP-HDL significantly decreased in the 0.5% IgY agent group. The artificial infection results showed that after 14 days of WSSV infection, the survival rates of shrimp in the 0.2% and 0.5% IgY agent groups, and the control group were 48.89%, 87.78%, and 0, respectively. The survival rate of shrimp in the 0.2% and 0.5% IgY agent groups was significantly higher than that in the control group, and the survival rate of shrimp in the 0.5% IgY agent group was also significantly higher than that in the 0.2 % IgY agent group. Specific IgY agents can change the course of a disease, delay disease onset and death of immune shrimp, and significantly improve the survival rate of shrimp over a certain period. The results showed that oral specific IgY agents could affect the activity of immune enzymes and the expression level of immune genes in the hepatopancreas of L. vannamei, significantly improving their ability to resist WSSV infection. This study provides a basis for the application of IgY agents in the prevention and control of WSSV infection, and also provides a reference for research on the anti-WSSV infection mechanism of IgY agents.
