A vector that expresses VP28 of WSSV can protect red swamp crayfish from white spot disease

Abstract

White spot disease caused by white spot syndrome virus (WSSV) leads to devastating losses in shrimp farming. The WSSV envelope protein VP28, can be used as subunit vaccines that can efficiently protect shrimp against WSSV disease. However, the function of the envelope protein VP19 was not confirmed, some researches found that VP19 could protect shrimp against WSSV, and other reports found it no any protection. To detect the functions of VP28 and VP19 and find a method to prevent this disease in red swamp crayfish Procambarus clarkii, we constructed the plasmid vectors pIevp28 and pIevp19, which contains the ie1 promoter and coding region of vp28 or vp19 of WSSV, respectively. The results of quantitative real-time PCR and western blot showed that the injected vectors could transcribe corresponding mRNAs and translate to the protein VP28 or VP19 in the crayfish. The vp28 or vp19 signal was detected on the third day post injection, and maintained its expression for 30 days. The mortality of the crayfish with pIevp28 showed obvious decline compared with the controls (pIe and PBS injection). However, pIevp19 seems did not affect the mortality of the crayfish compared with the controls. Furthermore, only VP28 was found tightly bound to the host haemocytes under immunocytochemistry. The results suggest that the VP28 protein might protect shrimp from the virus through competitive inhibition. We also found that oral administration of Escherichia coli with pIevp28 could protect crayfish from white spot disease, but the E. coli with pIevp19 was not. Therefore, we think that oral administration of bacteria with pIevp28 is a potentially easy therapeutic way against white spot disease in aquaculture.