A formulated double-stranded RNA diet for reducing Penaeus monodon densovirus infection in black tiger shrimp

RNA Interference Applied to Crustacean Aquaculture

RNA interference (RNAi) is a powerful tool that can be used to specifically knock-down gene expression using double-stranded RNA (dsRNA) effector molecules. This approach can be used in aquaculture as an investigation instrument and to improve the immune responses against viral pathogens, among other applications. Although this method was first described in shrimp in the mid-2000s, at present, no practical approach has been developed for the use of dsRNA in shrimp farms, as the limiting factor for farm-scale usage in the aquaculture sector is the lack of cost-effective and simple dsRNA synthesis and administration procedures. Despite these limitations, different RNAi-based approaches have been successfully tested at the laboratory level, with a particular focus on shrimp. The use of RNAi technology is particularly attractive for the shrimp industry because crustaceans do not have an adaptive immune system, making traditional vaccination methods unfeasible. This review summarizes recent studies and the state-of-the-art on the mechanism of action, design, use, and administration methods of dsRNA, as applied to shrimp. In addition, potential constraints that may hinder the deployment of RNAi-based methods in the crustacean aquaculture sector are considered.

RNAi-Based Therapy: Combating Shrimp Viral Diseases

Shrimp aquaculture has become a vital industry, meeting the growing global demand for seafood. Shrimp viral diseases have posed significant challenges to the aquaculture industry, causing major economic losses worldwide. Conventional treatment methods have proven to be ineffective in controlling these diseases. However, recent advances in RNA interference (RNAi) technology have opened new possibilities for combating shrimp viral diseases. This cutting-edge technology uses cellular machinery to silence specific viral genes, preventing viral replication and spread. Numerous studies have shown the effectiveness of RNAi-based therapies in various model organisms, paving the way for their use in shrimp health. By precisely targeting viral pathogens, RNAi has the potential to provide a sustainable and environmentally friendly solution to combat viral diseases in shrimp aquaculture. This review paper provides an overview of RNAi-based therapy and its potential as a game-changer for shrimp viral diseases. We discuss the principles of RNAi, its application in combating viral infections, and the current progress made in RNAi-based therapy for shrimp viral diseases. We also address the challenges and prospects of this innovative approach.

RNA Interference in Aquaculture: A Small Tool for Big Potential

For decades, the tight regulatory functions of DNA and RNA have been the focus of extensive research with the goal of harnessing RNA molecules (e.g., microRNA and small interfering RNA) to control gene expression and to study biological functions. RNA interference (RNAi) has shown evidence of mediating gene expression, has been utilized to study functional genomics, and recently has potential in therapeutic agents. RNAi is a natural mechanism and a well-studied tool that can be used to silence specific genes. This method is also used in aquaculture as a research tool and to enhance immune responses. RNAi methods do have their limitations (e.g., immune triggering); efficient and easy-to-use RNAi methods for large-scale applications need further development. Despite these limitations, RNAi methods have been successfully used in aquaculture, in particular shrimp. This review discusses the uses of RNAi in aquaculture, such as immune- and production-related issues and the possible limitations that may hinder the application of RNAi in the aquaculture industry. Our challenge is to develop a highly potent in vivo RNAi delivery platform that could complete the desired action with minimal side effects and which can be applied on a large-scale with relatively little expense in the aquaculture industry.

Increased antiviral capacity of transgenic silkworm via knockdown of multiple genes on Bombyx mori bidensovirus

Bombyx mori bidensovirus (BmBDV) causes fatal flacherie disease leading to severe economic losses in sericultures. The BmDNV-Z genome contains two single-stranded DNA molecules, VD1 and VD2. For generating silkworm lines with antiviral properties, two transgenic RNA interference (RNAi) vectors were constructed. Open reading frames (ORFs) 1-4 of VD1 were knockdown by vector pb-BDV1 while ORF1a, ORF1b, and ORF3 of VD2 were knockdown by vector pb-BDV2. Transgenic silkworm lines BDV1-I and BDV2-I were generated via RNAi microinjection. Mortality rates of BDV1-I and BDV2-I were reduced by 45% and 39%, respectively, and quantitative PCR showed that VD1 and VD2 contents in BDV1-I and BDV2-I were significantly lower than in the non-transgenic line. However, economic traits showed no obvious differences. Thus, knockdown of multiple BmDNV-Z genes provides strong resistance to BDV1-I and BDV2-I lines, and these can be used in sericulture without hampering silk production.

Presence of Penaeus monodon densovirus in the ovary of chronically infected P. monodon subadults

Shrimp infected with Penaeus monodon densovirus (PmoDNV) usually display no specific gross signs, but heavy infections can kill postlarvae and retard juvenile growth. In the present study, samples of hepatopancreas, feces, gonads and hemolymph were isolated from male and female P. monodon subadults chronically infected by PmoDNV. Each sample of hepatopancreas and gonad was divided into 2 parts: one for PmoDNV detection by polymerase chain reaction (PCR), and the other for routine histology and immunohistochemistry. The frequency of positive findings via PCR assays was 92% in the hepatopancreas, 57% in feces, 50% in ovary, 35% in hemolymph and 0% in the testis. Using the densitometric value (DV) of the specific band for PmoDNV relative to that of the β-actin gene as an index of the viral load in the samples, no significant differences were observed among sample types and sexes. Hematoxylin-eosin staining of infected hepatopancreas revealed typical PmoDNV inclusions in the nuclei of infected cells. The ovaries with high DV (>1) contained various types of inclusions along the row of the follicular cells or possibly in the connective tissue cells surrounding the oocytes. Using immunohistochemistry with specific probes to detect PmoDNV proteins, a positive reaction was observed in viral inclusions found in infected hepatopancreas and in ovaries with high DV, specifically in the ovarian capsule, hemolymph, oocytes and nuclear inclusions. These results suggest that the localization of PmoDNV in P. monodon is not confined to the hepatopancreas, but rather that the virus can also occur in the ovary; hence, trans-ovarian, vertical transmission of the virus is highly possible.