Therapeutic inhibition of yellow head virus multiplication in infected shrimps by YHV-protease dsRNA.

Yellow head virus (YHV) is an invertebrate nidovirus which causes a severe mortality in cultured Penaeus monodon. The mortality may be prevented by prior treatment of shrimps with YHV-protease dsRNA. Whether the YHV infected shrimp might be cured by the dsRNA remains to be investigated. P. monodon injected with 10(-6) YHV showed a high virus replication and mortality within 2 days. Injection of 25 microg YHV-protease dsRNA at 3, 6, 12 or 24 h post YHV infection showed a strong inhibition of YHV replication up to 12 h. Unrelated dsRNA-GFP showed no inhibition, indicating that the inhibition was nucleic acid sequence specific through RNAi pathway. Shrimp mortality could be prevented at 3h post YHV infection by the dsRNA, but not at 24 h. These results demonstrate that YHV-protease dsRNA gives therapeutic effect and pave the way to develop a cure for YHV-infected shrimps.