Effective inhibition of infectious bursal disease virus replication by recombinant avian adeno-associated virus-delivered microRNAs.

RNA interference (RNAi) is a novel antiviral strategy against a variety of virus infections. Infectious bursal disease virus (IBDV) causes an economically important disease in young chickens. This study demonstrated efficient inhibition of IBDV replication by recombinant avian adeno-associated virus (rAAAV)-delivered anti-VP1 and anti-VP2 microRNAs (miRNAs). In the viral vector-transduced cells, sequence-specific miRNA expression was detected by poly(A)-tailed RT-PCR. Reporter assays using a pVP2-EGFP vector showed significant and long-lasting inhibition of VP2-EGFP expression in cells transduced with anti-VP2 miRNA-expressing rAAAV-RFPmiVP2E, but not with the control miRNA-expressing rAAAV-RFPmiVP2con or anti-VP1 miRNA-expressing rAAAV-RFPmiVP1. Semi-quantitative RT-PCR and/or virus titration assays showed a significant inhibitory effect on homologous IBDV replication in cells transduced with rAAAV-RFPmiVP1 or rAAAV-RFPmiVP2E. For two heterologous IBDV isolates, transduction with rAAAV-RFPmiVP1 led to slightly weaker but similar inhibitory effects, whereas transduction with rAAAV-RFPmiVP2E resulted in significantly weaker and different inhibitory effects. These results suggest that rAAAV could act as an efficient vector for miRNA delivery into avian cells and that VP1 is the more suitable target for interfering with IBDV replication using RNAi technology.