Application of dsRNA VP15-WSSV by Oral Vaccination to Increase Survival Rate and Response Immunes of Tiger Shrimp Penaeus monodon

Abstract

Background: RNA interference (RNAi) has recently introduced as a powerful technique for specific gene silencing in antiviral therapy for controlling shrimp diseases. The present study was conducted to assess the effect of dsRNA VP15-WSSV vaccine by oral administration on tiger shrimp survival rate and response immunes. Methods: A gene encoding VP15 was isolated from tiger shrimp infected WSSV and cloned into the L4440 vector with the T7 promoter. For mass production, the pT7-VP15 gene construct was transformed to bacteria. The bacteria were inactivated using the heat-killed method by immersion and 108 cells of bacteria were mixed with 0.02 g of commercial shrimp feed for dsRNA application. The shrimp were fed by: (A) feed containing dsRNA and coated by fish oil, (B) feed without dsRNA and coated by fish oil and (C) feed without dsRNA and fish oil. The shrimp were challenged with WSSV by intramuscular injection after vaccination for two weeks. The survival rate (SR) after the challenge test was counted daily, while the THC and proPO were observed before, then on 1st, 3rd and 5th days post-challenge (dpc). Result: The survival rate of tiger shrimp for all treatments tended to decrease until the 3rd dpc, while the 4th dpc the vaccinated tiger shrimp was started to exhibit the higher SR compared to both treatments. The vaccinated tiger shrimp had significantly (P<0.05) higher SR and THC compared with both control treatments, but not significantly (P>0.05) for proPO activity. The results indicated that the application of oral dsRNA vaccination suggested increasing in SR and response immune of tiger shrimp.