title: Transcriptome analysis reveals strong and complex antiviral response in a mollusc.
abstract: Viruses are highly abundant in the oceans, and how filter-feeding molluscs without adaptive immunity defend themselves against viruses is not well understood. We studied the response of a mollusc Crassostrea gigas to Ostreid herpesvirus 1 µVar (OsHV-1μVar) infections using transcriptome sequencing. OsHV-1μVar can replicate extremely rapidly after challenge of C. gigas as evidenced by explosive viral transcription and DNA synthesis, which peaked at 24 and 48 h post-inoculation, respectively, accompanied by heavy oyster mortalities. At 120 h post-injection, however, viral gene transcription and DNA load, and oyster mortality, were greatly reduced indicating an end of active infections and effective control of viral replication in surviving oysters. Transcriptome analysis of the host revealed strong and complex responses involving the activation of all major innate immune pathways that are equipped with expanded and often novel receptors and adaptors. Novel Toll-like receptor (TLR) and MyD88-like genes lacking essential domains were highly up-regulated in the oyster, possibly interfering with TLR signal transduction. RIG-1/MDA5 receptors for viral RNA, interferon-regulatory factors, tissue necrosis factors and interleukin-17 were highly activated and likely central to the oyster's antiviral response. Genes related to anti-apoptosis, oxidation, RNA and protein destruction were also highly up-regulated, while genes related to anti-oxidation were down-regulated. The oxidative burst induced by the up-regulation of oxidases and severe down-regulation of anti-oxidant genes may be important for the destruction of viral components, but may also exacerbate oyster mortality. This study provides unprecedented insights into antiviral response in a mollusc. The mobilization and complex regulation of expanded innate immune-gene families highlights the oyster genome's adaptation to a virus-rich marine environment.
authors.affiliation: Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, Shandong 266003, China; Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, Port Norris, NJ 08345, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: He
authors.affiliation: UMR BOREA, "Biologie des Organismes et Ecosystèmes Aquatiques", MNHN, UPMC, UCBN, CNRS-7208, IRD, Université de Caen Basse-Normandie, Esplanade de la Paix, 14032 CAEN, France.
authors.forename: Aude
authors.initials: A
authors.lastname: Jouaux
authors.affiliation: Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, Port Norris, NJ 08345, USA.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Ford
authors.affiliation: UMR BOREA, "Biologie des Organismes et Ecosystèmes Aquatiques", MNHN, UPMC, UCBN, CNRS-7208, IRD, Université de Caen Basse-Normandie, Esplanade de la Paix, 14032 CAEN, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Lelong
authors.affiliation: UMR BOREA, "Biologie des Organismes et Ecosystèmes Aquatiques", MNHN, UPMC, UCBN, CNRS-7208, IRD, Université de Caen Basse-Normandie, Esplanade de la Paix, 14032 CAEN, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Sourdaine
authors.affiliation: UMR BOREA, "Biologie des Organismes et Ecosystèmes Aquatiques", MNHN, UPMC, UCBN, CNRS-7208, IRD, Université de Caen Basse-Normandie, Esplanade de la Paix, 14032 CAEN, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Mathieu
authors.affiliation: Haskin Shellfish Research Laboratory, Department of Marine and Coastal Sciences, Rutgers University, Port Norris, NJ 08345, USA. Electronic address: xguo@hsrl.rutgers.edu.
authors.forename: Ximing
authors.initials: X
authors.lastname: Guo
mesh_terms: D000818:Animals; D049896:Crassostrea / Q000235:genetics* / Q000276:immunology / Q000821:virology*; D004267:DNA Viruses / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D016679:Genome, Viral; D008969:Molecular Sequence Data
keywords: Antiviral response; Immune receptors; Innate immunity; Marine virus; Ostreid herpesvirus OsHV-1μVar; Oxidative burst; Oyster; Viral RNA