title: Anti-viral gene induction is absent upon secondary challenge with double-stranded RNA in the Pacific oyster, Crassostrea gigas.
abstract: Oyster farming is one of the most important aquaculture industries in the world. However, its productivity is increasingly limited by viral disease and we do not yet have management practices, such as protective vaccination, that can control these disease outbreaks. Hence, in the current study we investigated the expression of known anti-viral genes in oysters (Crassostrea gigas) in response to primary and secondary encounter with a virus associated molecular pattern (dsRNA), and tested whether a common form of epigenetic gene regulation (DNA methylation) was associated with the expression of these anti-viral genes. Injection of dsRNA into the adductor muscle resulted in the rapid and transient expression of virus recognition receptors (TLR & MDA5), whereas several anti-viral signalling (IRF & SOC-1) and effector (PKR & viperin) genes were still up-regulated at one week post primary challenge (p < 0.05). This primary encounter with dsRNA appeared to deplete the immune system because anti-viral gene induction was absent in the gills when oysters were given a second injection of dsRNA at 1-week post-primary injection. The expression of DNA methylation genes (DNMT1, DNMT3b, TDG, TET2) and DNA methylation profiles up-stream of specific anti-viral genes (STING, SOC-1 & Viperin) did not change in response to dsRNA injection (p > 0.05). These results collectively suggest that C. gigas does not have an enhanced anti-viral gene response (immune-priming) to secondary dsRNA challenge and that the sustained up-regulation of anti-viral signalling and effector genes following primary challenge is unlikely to be associated with upstream DNA methylation levels.
authors.affiliation: School of Biological Sciences and Australian Seafood Cooperative Research Centre, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia. Electronic address: tim.green@flinders.edu.au.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Green
authors.affiliation: Marine Ecology Research Centre, Southern Cross University, P.O. Box 157, Lismore, NSW 2480, Australia.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Benkendorff
authors.affiliation: School of Biological Sciences and Australian Seafood Cooperative Research Centre, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia; Nofima, P.O. Box 210, N-1431 Ås, Norway.
authors.forename: Nick
authors.initials: N
authors.lastname: Robinson
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Raftos
authors.affiliation: School of Biological Sciences and Australian Seafood Cooperative Research Centre, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Speck
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D049896:Crassostrea / Q000235:genetics* / Q000276:immunology* / Q000821:virology; D019175:DNA Methylation / Q000276:immunology; D017931:DNA Primers / Q000235:genetics; D005786:Gene Expression Regulation / Q000276:immunology*; D054884:Host-Pathogen Interactions; D047468:Immunoprecipitation; D012330:RNA, Double-Stranded / Q000008:administration & dosage / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology
chemical_list: D017931:DNA Primers; D012330:RNA, Double-Stranded
keywords: Anti-viral response; Crassostrea; DNA methylation; Immune-priming; Poly I:C