Effect of different doses of dsRNA VP15 vaccine for controlling white spot syndrome virus infection in tiger shrimp Penaeus monodon

Abstract

White spot syndrome virus (WSSV) is the most virulent pathogen in cultured penaeid shrimp, including Penaeus monodon. RNA interference (RNAi) technology has been applied for silencing of viral gene expression during infection, through induced by double-stranded RNA (dsRNA) of WSSV viral protein (VP). This study aimed to evaluate the effect of different doses of dsRNA VP15 WSSV on the survival rate and immune response of tiger shrimp. Production of dsRNA was conducted by in-vitro using the MEGAscript RNAi kit. Different doses of dsRNA vaccination as treatments were: (A) 0.02 µg, (B) 0.2 µg, (C) 2 µg and (D) control (injected with 50 µL of saline solution) for each shrimp. Vaccination was carried out by intramuscular injection to tiger shrimp (15.88 ± 3.50 g) and the shrimp were challenged by injection with WSSV. Survival rate was counted daily, while total hemocyte count (THC), prophenoloxidase (proPO) activity, and antiviral gene expression were observed before and 1-, 3- and 5-days post-challenge (dpc). The results showed that the dsRNA VP15 vaccine was successfully produced by the MEGAscript RNAi kit. The different doses of dsRNA VP15 significantly influenced the tiger shrimp survival (P<0.05), in which a dose of 0.02 µg/shrimp showed the highest shrimp survival (15%) compared to the other doses and control. The THC and proPO activity of vaccinated shrimp showed a higher value compared to the control. A trend to increase the antiviral gene expression was obtained until 3 dpc and then decrease at 5 dpc. The results indicated the application of dsRNA VP15 as a potential way to control WSSV infection of tiger shrimp.