Delivery of virus-specific dsRNA using a composite nanomaterial improves the protection of shrimp (Litopenaeus vannamei) against yellow head virus challenge

Abstract

Aquaculture systems that produce crustaceans are often threatened by various diseases, particularly those caused by viruses. RNA interference (RNAi) is a promising technology that can enhance the resilience of aquaculture species against viral infections. The success of RNAi-based protection relies on the availability of efficient delivery systems for double-stranded RNA (dsRNA), the precursor molecule in this pathway. However, the instability of dsRNA is a major challenge for any control technology that aims to function in complex production systems, especially in aquatic environments. This study investigated composite polymer-clay nanoparticles, based on a bentonite biopolymer (BenPol), for their ability to protect dsRNA from degradation and improve its delivery to shrimp (Litopenaeus vannamei). A dsRNA targeting the protease gene of yellow head virus (dsYHV) was adsorbed within these nanoparticles to produce BenPol-dsYHV complexes. The results showed that the BenPol nanomaterial was capable of safeguarding the dsYHV from nuclease digestion and stabilizing it under simulated environmental conditions in a time-dependent manner. To evaluate the release efficiency of the BenPol-dsYHV complexes in shrimp, the complexes were prepared and stored at 4 °C for 3 or 8 days before injection into shrimp. The injected shrimp were maintained for 7 days prior to challenging with YHV. The findings revealed that shrimp treated with BenPol-dsYHV complexes prepared 8 days prior to injection had a 100 % survival rate compared to all other groups. Consequently, the 8-day prepared BenPol-dsYHV complexes were further tested to determine the duration of protection from YHV infection. Shrimp were injected with BenPol-dsYHV complexes for 7 and 21 days before YHV challenge. The results showed that the mortality rates in the BenPol-dsYHV complexes and dsYHV groups were 33 % and 69 %, respectively, for the treatments 7 days before YHV challenge. However, the mortality rate was similar when the interval between treatment and YHV challenge was 21 days. The possible mechanisms underlying these observations are discussed. The results of this study suggest that BenPol is a promising nanoparticle-based delivery platform for the safe and effective delivery of dsRNA to protect shrimp against viral infections in aquaculture production systems.