The parapoxvirus Orf virus inhibits IFN-β expression induced by dsRNA

• Published in: Virus research Vol. 307; p. 198619
• Main Authors: AlDaif, Basheer A, Mercer, Andrew A, Fleming, Stephen B
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 02.01.2022
• Subjects: Antiviral Agents - metabolism; HEK293 Cells; Humans; Immune modulation; Interferon Type I - metabolism; Interferon-beta; Interferon-beta - genetics; Interferon-beta - metabolism; Orf virus; Orf virus - genetics; Poxvirus; Retinoic acid inducible gene-like receptor; RNA, Double-Stranded - metabolism; OV-NZ2; RIG‐I; Poxvirus; Interferon-beta; IKK; ATF2/c-Jun; Orf virus; MDA5; Retinoic acid inducible gene-like receptor; PAMP; PRR; MAVS; STAT; TBK1; JAK; ORFV; PKR; RLR; STING; IRF; LGP2; Immune modulation
• ISSN: 0168-1702; 1872-7492
• DOI: 10.1016/j.virusres.2021.198619

•This article shows that the parapoxvirus orf virus has the ability to modulate type I IFN production. HEK293 cells are known to lack DNA pattern-recognition receptors and Toll-like receptors however, they do express the cytosolic dsRNA receptors RIG-I and MDA5. HEK293 cells were shown to produce high levels of IFN-β when cells were stimulated with dsRNA and this was shown to be predominantly via RIG-I-dependant signalling as confirmed by siRNA knock-down of RIG-I. Further we showed that HEK293 cells are permissive for orf virus and caused potent inhibition of IFN-β transcription when cells were stimulated with dsRNA post-viral infection. In addition our findings showed that the orf virus encoded factor ORF020, that is known to bind dsRNA, is involved in antagonising IFN expression. Overall, this study has shown for first time the ability of orf virus to counteract type i IFN expression by antagonising dsRNA-activated RIG-I signalling. Orf virus (ORFV) is the type species of the Parapoxvirus genus that belongs to the Poxviridae family. Type I interferons (IFN) are critical in the host defence against viruses. They induce hundreds of interferon stimulated genes (ISGs) many of which have an antiviral role. The ability of ORFV to modulate type I IFN production was undertaken to investigate whether ORFV could inhibit IFN-β expression via dsRNA dependant signalling pathways. HEK293 cells are known to lack DNA pattern-recognition receptors and Toll-like receptors however, they do express the cytosolic dsRNA receptors RIG-I and MDA5. HEK293 cells were shown to produce high levels of IFN-β when cells were stimulated with poly(I:C) and this was shown to be predominantly via RIG-I-dependant signalling as confirmed by siRNA knock-down of RIG-I. Further we showed that HEK293 cells are permissive for ORFV and caused potent inhibition of IFN-β transcription when cells were stimulated with poly(I:C) post-viral infection. Studies using heat inactivated ORFV suggested that de novo synthesis of early genes was required. In addition our findings showed that the ORFV encoded factor ORF020, that is known to bind dsRNA, is involved in antagonising IFN expression. Overall, this study has shown for first time the ability of ORFV to counteract type I IFN expression by antagonising dsRNA-activated RIG-I signalling.