title: A method to measure an indicator of viraemia in Atlantic salmon using a reporter cell line.
abstract: RTG-P1 is a transgenic fish cell line producing luciferase under the control of the IFN-induced Mx rainbow trout gene promoter. This cell line was used to measure viraemia of Salmonid alphavirus (SAV), the cause of Salmon Pancreas Disease (SPD), a serious disease in farmed Atlantic salmon. Two SAV genotype 1 (SAV1) isolates were used in this study, F93-125 (tissue-culture adapted, from Ireland) and 4640 (from a field case in Scotland). The kinetics and magnitude of luciferase activity were monitored versus the time of infection. During a direct infection experiment, the induction of luciferase significantly increased 16- and 4-fold after incubation for 6 days with F93-125 at 15 and 20°C, respectively. Filtration and heat treatment experiments demonstrated that the luciferase induction in RTG-P1 was dependent on viral replication. Unlike many cell lines used in fish viral diagnostic, RTG-P1 is not sensitive to salmonid serum, therefore, viraemia could be successfully monitored on serum collected from fish during a cohabitation challenge with 4640 isolate. A peak of viraemia could be detected 16 days post IP inoculation of the shedders. This novel cost-effective method to measure viraemia does not rely on development of cytopathic effect (CPE) in culture, is compatible with non-lethal blood collections in fish and can be used to assign emerging diseases to a viral aetiology.
authors.affiliation: Marine Scotland Science, Marine Laboratory, Victoria Road, Aberdeen AB11 9DB, Scotland, UK. Bertrand.Collet@scotland.gsi.gov.uk
authors.forename: Bertrand
authors.initials: B
authors.lastname: Collet
authors.forename: Katy
authors.initials: K
authors.lastname: Urquhart
authors.forename: Patricia
authors.initials: P
authors.lastname: Noguera
authors.forename: Katrine H
authors.initials: KH
authors.lastname: Larsen
authors.forename: Katherine
authors.initials: K
authors.lastname: Lester
authors.forename: David
authors.initials: D
authors.lastname: Smail
authors.forename: David
authors.initials: D
authors.lastname: Bruno
mesh_terms: D000524:Alphavirus / Q000302:isolation & purification*; D018354:Alphavirus Infections / Q000175:diagnosis / Q000662:veterinary* / Q000821:virology; D000818:Animals; D002460:Cell Line; D005393:Fish Diseases / Q000175:diagnosis* / Q000821:virology; D017930:Genes, Reporter; D008156:Luciferases / Q000032:analysis / Q000235:genetics; D020317:Salmo salar / Q000821:virology*; D014730:Veterinary Medicine / Q000379:methods*; D019562:Viral Load / Q000379:methods; D014766:Viremia / Q000175:diagnosis / Q000662:veterinary* / Q000821:virology; D014773:Virology / Q000379:methods*
chemical_list: D008156:Luciferases