The antiviral vp28-siRNA expressed in bacteria protects shrimp against white spot syndrome virus (WSSV)

White spot syndrome virus (WSSV) has been a major viral pathogen responsible for large economic losses to shrimp aquaculture all over the world. The RNAi mediated by siRNA contributes a novel strategy to control this viral disease. However, the efficient approach to deliver the siRNA into shrimp in vivo remains to be addressed. In our study, the vp28-siRNA, having a specific activity against WSSV, was expressed in an RNase III-deficient strain of Escherichia coli HT115 (DE3). Then the inactivated bacteria expressing the vp28-siRNA were delivered into Marsupenaeus japonicus shrimp by injection. The results showed that the vp28-siRNA could be detected in shrimp hemocytes. As shown by quantitative PCR, the vp28-siRNA inhibited the replication of WSSV in shrimp, which presented a better antiviral activity of siRNA. Further evidence indicated that the mortality of WSSV-infected shrimp was significantly reduced (P < 0.01) by the vp28-siRNA. Therefore this study presented a novel efficient therapeutic approach to control WSSV by using siRNA expressed in bacteria.