Immunological interactions between Piscine orthoreovirus and Salmonid alphavirus infections in Atlantic salmon.
Heart and skeletal muscle inflammation (HSMI) and pancreas disease (PD) cause substantial losses in Atlantic salmon (Salmo salar) aquaculture. The respective causative agents, Piscine orthoreovirus (PRV) and Salmonid alphavirus (SAV), are widespread and often concurrently present in farmed salmon. An experimental infection in Atlantic salmon was conducted to study the interaction between the two viruses, including the immunological mechanisms involved. The co-infected fish were infected with PRV four or ten weeks before they were infected with SAV. The SAV RNA level and the PD specific lesions were significantly lower in co-infected groups compared to the group infected by only SAV. The expression profiles of a panel of innate antiviral response genes and the plasma SAV neutralization titers were examined. The innate antiviral response genes were in general upregulated for at least ten weeks after the primary PRV infection. Plasma from co-infected fish had lower SAV neutralizing titers compared to the controls infected with only SAV. Plasma from some individuals infected with only PRV neutralized SAV, but heat treatment removed this effect. Field studies of co-infected fish populations indicated a negative correlation between the two viruses in randomly sampled apparently healthy fish, in line with the experimental findings, but a positive correlation in moribund or dead fish. The results indicate that the innate antiviral response induced by PRV may temporary protect against a secondary SAV infection.
Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway; SalMar ASA, Kverva, Norway.
Magnus Vikan
MV
Røsæg
Sections of Immunology and Virology, Norwegian Veterinary Institute, Oslo, Norway.
Morten
M
Lund
Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway.
Ingvild Berg
IB
Nyman
Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway.
Turhan
T
Markussen
PatoGen AS, Ålesund, Norway.
Vidar
V
Aspehaug
Sections of Immunology and Virology, Norwegian Veterinary Institute, Oslo, Norway.
Hilde
H
Sindre
Sections of Immunology and Virology, Norwegian Veterinary Institute, Oslo, Norway.
Maria Krudtaa
MK
Dahle
Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway. Electronic address: espen.rimstad@nmbu.no.
Espen
E
Rimstad
D000524:Alphavirus / Q000502:physiology; D018354:Alphavirus Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D000818:Animals; D056738:Cross Protection; D005393:Fish Diseases / Q000276:immunology* / Q000821:virology; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate; D018165:Orthoreovirus / Q000502:physiology; D012088:Reoviridae Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D020317:Salmo salar
D029941:Fish Proteins
Atlantic salmon; Co-infection; Innate immune response; Piscine orthoreovirus; Salmonid alphavirus