Induction of antiviral immunity by double-stranded RNA in a marine invertebrate.

Vertebrates mount a strong innate immune response against viruses, largely by activating the interferon system. Double-stranded RNA (dsRNA), a common intermediate formed during the life cycle of many viruses, is a potent trigger of this response. In contrast, no general inducible antiviral defense mechanism has been reported in any invertebrate. Here we show that dsRNA induces antiviral protection in the marine crustacean Litopenaeus vannamei. When treated with dsRNA, shrimp showed increased resistance to infection by two unrelated viruses, white spot syndrome virus and Taura syndrome virus. Induction of this antiviral state is independent of the sequence of the dsRNA used and therefore distinct from the sequence-specific dsRNA-mediated genetic interference phenomenon. This demonstrates for the first time that an invertebrate immune system, like its vertebrate counterparts, can recognize dsRNA as a virus-associated molecular pattern, resulting in the activation of an innate antiviral response.