Hayakijkosol, Orachun, and Owens, Leigh (2012) B2 or not B2: RNA interference reduces Macrobrachium rosenbergii nodavirus replication in redclaw crayfish (Cherax quadricarinatus). Aquaculture, 326-329. pp. 40-45.

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Abstract

Macrobrachium rosenbergii nodavirus (MrNV) which causes white tail disease (WTD) is one of the most serious viral infections in M. rosenbergii. In less than one week mortality has been reported in hatcheries. RNA interference (RNAi) is an innate immune response which can be triggered by the recognition of intracellular dsRNA and can inhibit viral RNA in a sequence specific manner in cells. RNAi has been used against viral infections such as yellow head virus and white spot syndrome virus in prawns. However, no study of RNAi against MrNV has been reported. In this study, RNAi against viral protein B2 and MrNV were inoculated into redclaw crayfish (Cherax quadricarinatus) which was developed as an experimental animal model. Mortalities were 10% with stealth RNAi plus MrNV and 60% with control stealth RNAi and MrNV exposure. Moreover, length and weight analyses of control stealth RNAi with MrNV were significantly smaller (8.7 cm) and lighter (17.69 g) (F = 8.106, df = 5, 54, p < 0.05 and F = 2.943, df = 5, 54, p < 0.05), respectively compared to other treatments (average 10.3 cm in length and 22.9 g in weight). In this study, clinical signs of MrNV and histopathological lesions such as myolysis with haemocytic infiltration in the muscle were found in infected redclaw crayfish. Using qPCR, two out of ten redclaw crayfish in the stealth RNAi with MrNV treatment and eight out of ten in control stealth RNAi with MrNV treatment were detected to have MrNV. Protein B2 is anti-RNAi mechanism of nodavirus. Down regulating the viral defence by targeting protein B2 gene with RNAi could be an effective tool to decrease mortality and limit MrNV infection. This approach could be very effective against the economical very important viral encephalopathy and retinopathy in fish caused by nodavirus.

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