RNA interference reduces PmergDNV expression and replication in an in vivo cricket model

RNA interference (RNAi) is an attractive anti-viral preventative because it allows interference with the expression of a viral gene in a highly sequence-specific manner. Thus, essential viral genes can be targeted by design, with little or no risk of undesired off-target effects. To investigate if stealth RNAis can mediate a sequence-specific anti-viral effect against PmergDNV, adult Acheta domesticus were injected with 5 microg of stealth RNAi or control stealth RNAi, targeting the capsid protein. Twenty-four hours post-injection, crickets were challenged with PmergDNV. Mortality was monitored for 14 days and real-time reverse transcriptase PCR was used to enumerate the number of copies of PmergDNV in cricket tissues. Whilst statistically not significant, trends in mortality suggest crickets injected with RNAi targeting PmergDNV had the lowest mortality rate (11.5%) compared to crickets injected with control dsRNAi (33%) and PmergDNV alone (25%). Crickets challenged with specific dsRNAi had statistically significantly reduced PmergDNV titres by one log (3.58 x 10(2)) compared to crickets challenged with PmergDNV alone (3.42 x 10(3)). Interestingly, even the control dsRNAi was capable of reducing PmergDNV titres by one log (3.95 x 10(2)), but did not produce an inhibitory effect quite as strong as the targeted dsRNAi for the capsid protein of PmergDNV. The introduction of dsRNAi corresponding to the capsid protein of PmergDNV, was effective in reducing viral replication in Acheta domesticus. Administration of PmergDNV-specific dsRNAis may provide an efficient counter measure against PmergDNV in prawns.