Protection of Litopenaeus vannamei against white spot syndrome virus by electron-irradiated inactivated vaccine and prebiotic immunogen

WSSV1 is an infectious agent of shrimp and other crustaceans. Neither effective vaccines nor treatments are currently available for this disease. Although the immune system of shrimps is not comparable to that of vertebrates, shrimps can acquire protection against pathogenic challenge by building up immunity. This study for the production of radio vaccines against WSSV used a radiation facility providing 10-Mev electron beams and a 2-mA current. In this study WSSV was isolated from infected shrimp samples and multiplied in Astacus leptodactylus crayfish hemolymph and called WSSV/IRN/1/2010. Titration of WSSV was obtained in post-larvae by Karber method as 105.4 LD502/mL and the virus was inactivated by the electron beam irradiation, the D10 value and optimum dose of electron beam were obtained at 1.85 and 13 kGy, respectively. Electron beam-irradiated WSSV (EBI3-WSSV) was used as a radio vaccine to immunize L. vannamei by intramuscular injection and bath-immersion routes. Prebiotic Immunogen as a diet additive was used to improve immune responses. PD504 was calculated at 5.62 and 6.02 for the shrimp groups vaccinated with EBI-WSSV vaccine and EBI-WSSV vaccine + Prebiotic Immunogen, respectively. Calculated RPS values were 75%, 91% and 25% for the EBI-WSSV vaccine alone, EBI-WSSV + Prebiotic Immunogen and Prebiotic Immunogen alone (PID5) groups vaccinated by immersion route, and 73%, 82% and 18.5% by injection route, respectively. Significant difference in cumulative mortalities was observed between both vaccination groups (EBI-WSSV and EBI-WSSV+ immunogen), and the control groups (P<0.05). No significant difference in cumulative mortalities was observed between the two vaccination groups (P>0.05). Therefore, EBI-WSSV vaccine induced immunity responses in shrimp against WSSV infection and Prebiotic Immunogen enhanced this response.