Vector derived artificial miRNA mediated inhibition of West Nile virus replication and protein expression.

West Nile virus (WNV) has been found to be a common cause of neuroinvasive arboviral disease worldwide in human and horses. The process of RNA interference induced by small RNA molecules, like small interfering RNA (siRNA) and microRNA (miRNA), proved to be a novel approach for preventing viral infections. So far there is no published data for inhibition of West Nile virus by vector delivered artificial miRNA which believed to have more inhibitory potential than small interfering (siRNA). In the present study, we designed two artificial miRNA (amiRNAs) targeting the conserved NS5 and NS2A genomic regions of West Nile virus. These amiRNAs oligos were cloned in to miRNA based vector having murine miR-155 backbone which allows the high expression of amiRNAs in green fluorescent protein (GFP) tagged form. Vero cells were transiently transfected by cytomegalovirus (CMV) promoter derived vector expressing amiRNAs transcribed by RNA Pol II. Efficacy of amiRNA targeting the NS5 and NS2A regions of WNV was determined in highly virulent WNV Eg101 strain in Vero cells. The result indicated that both amiRNA effectively inhibit West Nile virus replication. The concatenated amiRNA having dual pre-amiRNA expression cassette showed better efficacy. amiRNA targeting NS5 showed best protection against WNV infection and percentage reduction of WNV titer was observed at 96 hpi is 97.11%. Further study for inhibition of WNV replication was assessed by plaque assay, quantitative reverse transcriptase PCR (qRT-PCR) assay, Immunofluorescence assay and Western blot analysis. Present study concludes that amiRNA (NS5) targeting conserved region of gene significantly reduced the virus replication as determined by plaque assay. Similarly, reduction was also observed at RNA and protein level through real-time RT-PCR and Western blot analysis directly correlate with the inhibition of WNV replication. Here, we describe our current understanding of the role of miRNAs in host defense response against West Nile virus, as well as their potential as new therapeutic approaches.