Nucleic-acid based antivirals: augmenting RNA interference to 'vaccinate'Litopenaeus vannamei

The Pacific white shrimp, Litopenaeus vannamei (Penaeidae: Litopenaeus) has emerged as the dominant farmed shrimp species globally in tropical countries. Rearing animals at high density in semi-intensive or intensive culture systems, and translocating animals across the globe, have created optimum conditions for devastating epizootics. Of the various pathogens that impact shrimp culture, viruses are arguably the most important infectious disease agents that exact devastating economic losses to the industry. Augmenting the RNA interference (RNAi) capacity of shrimp is a promising, emerging solution to prevent disease caused by a variety of highly pathogenic shrimp viruses. Indeed RNAi functions as a primary mechanism of antiviral RNA in arthropods, as was revealed initially in studies of mosquito-virus interactions. Double-stranded RNA (dsRNA) or small interfering RNA (siRNA) can be used as RNAi triggers in vivo in L. vannamei to reduce the pathology associated with virus infection. We explored the efficacy of those triggers as a function of the target gene in the virus genome and show that efficacy is virus-specific and cannot be predicted based on the target gene function or transcript level in an infected cell. Further, we show that carefully designed RNAi triggers provide an immune stimulus that results in specific, long-term protection and therefore suggest that these dsRNA antivirals can function as vaccines in controlling disease.