Antiviral Immunity Induced by Double Stranded RNA in a Marine Shrimp
Javier Robalino1, Thomas Bartlett1, Sarah Prior2, Eleanor Shepard2, Pamela Parnell3, Robert Chapman2, Paul S. Gross1, Craig Browdy2, and Gregory Warr1
1 Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC
2 South Carolina Department of Natural Resources, Charleston, SC
3 Clemson Veterinary Diagnostic Center, Columbia, SC
Crustaceans are known to be susceptible to several pathogenic viruses. These viral diseases severely impact the shrimp aquaculture industry worldwide, and pose a threat to natural populations of crustaceans that serve essential roles in marine ecosystems. Thus, a better understanding of the mechanisms of antiviral immunity used by crustaceans is necessary to develop sustainable strategies to mitigate the impact of viral diseases in aquaculture, as well as to protect the marine environment. Results from our studies in a model crustacean, the shrimp Litopenaeus vannamei, suggest that double stranded RNA (dsRNA) triggers diverse mechanisms of antiviral immunity in these animals. First, a broad-spectrum, relatively weak and non-specific antiviral response is mounted after exposure to dsRNA of any sequence, by mechanisms that are not yet known. Additionally, dsRNA that is equivalent in sequence to virally-encoded transcripts is capable of stimulating potent and virus-specific antiviral immunity. This sequence-specific antiviral mechanism is likely the result of dsRNA-mediated homologous gene silencing (i.e. RNA interference or RNAi). The idea that RNAi is used naturally by shrimp to fight viral pathogens is supported by the observation that a highly virulent agent has evolved the capacity to suppress the host RNAi response. Taken together, our results suggest that 1) like in the vertebrates, dsRNA is recognized as an indicator of viral infection in invertebrates, 2) sequence-independent mechanisms as well as the RNAi pathway play roles in the antiviral immune response of marine shrimp, and 3) manipulation of the RNAi response may prove useful to help control viral diseases in shrimp aquaculture.