title: Salmonid alphavirus glycoprotein E2 requires low temperature and E1 for virion formation and induction of protective immunity.
abstract: Salmonid alphavirus (SAV; also known as Salmon pancreas disease virus; family Togaviridae) causes pancreas disease and sleeping disease in Atlantic salmon and rainbow trout, respectively, and poses a major burden to the aquaculture industry. SAV infection in vivo is temperature-restricted and progeny virus is only produced at low temperatures (10-15 °C). Using engineered SAV replicons we show that viral RNA replication is not temperature-restricted suggesting that the viral structural proteins determine low-temperature dependency. The processing/trafficking of SAV glycoproteins E1 and E2 as a function of temperature was investigated via baculovirus vectors in Sf9 insect cells and by transfection of CHSE-214 fish cells with DNA constructs expressing E1 and E2. We identified SAV E2 as the temperature determinant by demonstrating that membrane trafficking and surface expression of E2 occurs only at low temperature and only in the presence of E1. Finally, a vaccination-challenge model in Atlantic salmon demonstrates the biological significance of our findings and shows that SAV replicon DNA vaccines encoding E2 elicit protective immunity only when E1 is co-expressed. This is the first study that identifies E2 as the critical determinant of SAV low-temperature dependent virion formation and defines the prerequisites for induction of a potent immune response in Atlantic salmon by DNA vaccination.
authors.affiliation: Wageningen University, Laboratory of Virology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Mia C
authors.initials: MC
authors.lastname: Hikke
authors.affiliation: Department of Food Safety and Infection Biology, The Norwegian School of Veterinary Science, PO 8146 Dep, N-0033 Oslo, Norway.
authors.forename: Stine
authors.initials: S
authors.lastname: Braaen
authors.affiliation: MSD Animal Health Innovation, Thormøhlensgate 55, N-5008 Bergen, Norway.
authors.forename: Stephane
authors.initials: S
authors.lastname: Villoing
authors.affiliation: MSD Animal Health Innovation, Thormøhlensgate 55, N-5008 Bergen, Norway.
authors.forename: Kjartan
authors.initials: K
authors.lastname: Hodneland
authors.affiliation: Wageningen University, Laboratory of Virology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Corinne
authors.initials: C
authors.lastname: Geertsema
authors.affiliation: Wageningen University, Laboratory of Virology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Lisa
authors.initials: L
authors.lastname: Verhagen
authors.affiliation: MSD Animal Health Innovation, Thormøhlensgate 55, N-5008 Bergen, Norway.
authors.forename: Petter
authors.initials: P
authors.lastname: Frost
authors.affiliation: Wageningen University, Laboratory of Virology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Just M
authors.initials: JM
authors.lastname: Vlak
authors.affiliation: Department of Food Safety and Infection Biology, The Norwegian School of Veterinary Science, PO 8146 Dep, N-0033 Oslo, Norway.
authors.forename: Espen
authors.initials: E
authors.lastname: Rimstad
authors.affiliation: Wageningen University, Laboratory of Virology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands. Electronic address: gorben.pijlman@wur.nl.
authors.forename: Gorben P
authors.initials: GP
authors.lastname: Pijlman
mesh_terms: D000524:Alphavirus / Q000235:genetics; D018354:Alphavirus Infections / Q000517:prevention & control / Q000662:veterinary*; D000818:Animals; D002478:Cells, Cultured; D003080:Cold Temperature; D005393:Fish Diseases / Q000517:prevention & control* / Q000821:virology; D006023:Glycoproteins / Q000276:immunology; D012367:RNA, Viral / Q000235:genetics; D020317:Salmo salar; D061987:Sf9 Cells; D019444:Vaccines, DNA / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*; D014771:Virion / Q000276:immunology
chemical_list: D006023:Glycoproteins; D012367:RNA, Viral; D019444:Vaccines, DNA; D014759:Viral Envelope Proteins; D014765:Viral Vaccines
keywords: DNA vaccine; Glycoprotein; Salmonid alphavirus; Temperature