Immune gene profiles in Atlantic salmon (salmo salar L.) post-smolts infected with SAV3 by bath-challenge show a delayed response and lower levels of gene transcription compared to injected fish. Issue 62 (March 2017)

• Record Type: Journal Article
• Authors: Moore, L.J.; Jarungsriapisit, J.; Nilsen, T.O.; Stefansson, S.; Taranger, G.L.; Secombes, C.J.; Morton, H.C.; Patel, S.
• Is Part Of: Fish & shellfish immunology. Issue 62(2017)
• Page Start: 320
• Page End: 331
• Publication Date: 2017-03
• Subjects: Salmonid alphavirus -- Pancreas disease -- Gene expression -- Interferon -- Bath immersion -- Infection route; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2017.01.034
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: Salmonid alphavirus (SAV) causes pancreatic disease (PD) in salmonids in Northern Europe which results in large economic losses within the aquaculture industry. In order to better understand the underlying immune mechanisms during a SAV3 infection Atlantic salmon post-smolts were infected by either i.m. -injection or bath immersion and their immune responses compared. Analysis of viral loads showed that by 14 dpi i.m. -injected and bath immersion groups had 95.6% and 100% prevalence respectively and that both groups had developed the severe pathology typical of PD. The immune response was evaluated by using RT-qPCR to measure the transcription of innate immune genes involved in the interferon (IFN) response as well as genes associated with inflammation. Our results showed that IFNa transcription was only weakly upregulated, especially in the bath immersion group. Despite this, high levels of the IFN-stimulated genes (ISGs) such as Mx and viperin were observed. The immune response in the i.m. -injected group as measured by immune gene transcription was generally faster, and more pronounced than the response in the bath immersion group, especially at earlier time-points. The response in the bath immersion group started later as expected and appeared to last longer often exceeding the response in the i.m -injected fish at later time-points. High levels of transcription of many genes indicative of an active innate immune response were present in both groups. Highlights: The route of SAV3 infection affects the innate response in Atlantic salmon post-smolts recently transferred to seawater. SAV3 bath immersion challenge induces lower and more sustained innate immune response compared to injection challenge. Recently smoltified Atlantic salmon have a poor interferon response to salmonid alphavirus.