Effective inhibition of replication of infectious bursal disease virus by miRNAs delivered by vectors and targeting the VP2 gene

RNA interference (RNAi) is a potent mechanism against a variety of viral infections. Infectious bursal disease virus (IBDV) causes an important disease economically in chickens, which is difficult to control. As part of the development of viral vector-mediated RNAi strategy against the disease, five anti-VP2 small interference RNAs were selected for construction of microRNA (miRNA) expression vectors tailored for avian cells. Transfection of DF-1 cells with the five vectors resulted in significant inhibition of VP2-EGFP reporter gene expression. More effective miVP2A and miVP2E were selected for further study using single or double miRNA expression vectors. After demonstration of specific miRNA expression, the gene silencing effects were determined in the vector-transfected and IBDV-infected cells. Reverse transcriptase PCR and virus titration showed inhibition rates from 76 to 82% on VP2 expression and significant decreases in virus titer by individual and co-expressed miVP2A and miVP2E. The inhibitory effects lasted for at least 120 h after infection with IBDV. These data suggest that the miRNAs targeting the VP2 can inhibit efficiently replication of IBDV.