Submitted to: Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/11/2007
Publication Date: 9/1/2007
Citation: Chen, M., Granger, A.J., VanBrocklin, M.W., Payne, W.S., Hunt, H.D., Zhang, H.M., Dodgson, J.B., Holmen, S.L. 2007. Inhibition of avian leukosis virus replication by vector-based RNA interference. Virology. 365:464-472. Interpretive Summary: RNA interference (also known as "RNA-mediated interference", abbreviated RNAi) is a mechanism for RNA-guided regulation of gene expression in which double-stranded ribonucleic acid inhibits the expression of genes with complementary nucleotide sequences. RNAi has recently emerged as a promising antiviral technique in varied genetic research. We tested retroviral delivered RNAi constructs against a subgroup of avian leukosis virus (ALV), an important oncogenic pathogen of chickens. Data from this study demonstrated efficient RNA interference (RNAi) in avian cells. This also opens possibility for further study to prevent viral infections in chickens using the RNAi-based technology.
Technical Abstract: RNAi has recently emerged as a promising antiviral technique in vertebrates. To date, most studies have used exogenous short interfering RNAs (siRNAs) to inhibit viral replication, though vectors expressing short hairpin RNAs (shRNA-mirs) in the context of a modified endogenous micro-RNA (miRNA) are more efficient at inhibiting translation and more practical for delivery to live organisms. We tested retroviral vector-delivered shRNA-mirs against subgroup B avian leukosis virus (ALV), an important oncogenic pathogen of chickens. The host receptor gene tvb and viral gene env, both necessary for entry of ALV(B) into a host cell, were tested as targets using a replication competent retroviral vector designed to deliver shRNA-mirs from a modified chicken mir-30a cassette and transcribed by an RNA polymerase II (pol-II) promoter. The constructs effectively reduced expression of green fluorescent protein (GFP), tvb, and env(B) by as much as 90% in cultured avian cells. DF-1 cells expressing shRNA-mirs directed against the tvb sequence were resistant to infection by ALV(B) compared to cells treated with no vector or one expressing a non-specific control. DF-1 cells expressing shRNA-mirs targeted against the env(B) sequence also slowed ALV(B) replication. The shRNA-mir construct can also be expressed from an inducible promoter, allowing for the regulation of the antiviral effect by doxycycline. This study demonstrates efficient RNA interference (RNAi) in avian cells using shRNA-mirs expressed from a pol-II promoter delivered by a replication-competent retroviral vector. In addition, these sequences were effective at inhibiting ALV(B) infection and replication in vitro, warranting further study of RNAi-based viral resistance in vivo.