Acronym IMCOM
Category
Aquaculture
Title Development of tools for assessment of the immune competence of Atlantic salmon smolts and growers Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Aleksei Krasnov Coordinator email NA
Coordinator institution
NOFIMA - Norwegian Institute of Food, Fisheries and Aquaculture Research (Norway)
Institutions involved
NMBU - Norwegian University of Life Sciences (Norway) ,
Start year 2017 End year 2021 Funding (€) € 902,090 Website https://prosjektbanken.forskningsradet.no/en/project/FORISS/267644?Kilde=FORISS&distribution=Ar&chart=bar&calcType=funding&Sprak=no&sortBy=date&sortOrder=desc&resultCount=30&offset=180&TemaEmne.2=Marin+bioteknologi Summary "Smolt quality is a critical factor that determines success of Atlantic salmon aquaculture. Dramatic changes in salmon physiology, adaptation to novel environment, transportation stress and increased occurrence of pathogens make fish vulnerable, especially during first months in the sea. Rapid development of recirculation aquaculture systems (RAS) and new production protocols may be hindered by limitations in the biology of Atlantic salmon. This issue is the primary focus of current aquaculture research. Our previous findings of massive down-regulation of immune genes during smoltification suggested the need for development of methods for assessment of immune competence (ImCom), to supplement a toolbox for control of smolt quality. Advanced analytical methods were used to approach this task. Recently developed multigene expression assay (MGE) closes a gap between qPCR of small sets of genes and transcriptomics and has excellent potential for diagnostics. Bead-based immunoassay was used for multiplex analyses of antibody responses. Sequencing of IgM transcripts (Ig-seq) was developed to investigate the antibody repertoire and the traffic of B cells. The ultimate goal was assessment of immune competence of smolts and growers in relation to the production methods and conditions and the development of diagnostic tools that can be used by the industry.
Antibody responses after vaccination and challenge with salmonid alphavirus (SAV) were studied at NMBU. Differences in antibody kinetics were initially found in smolts exposed to two light regimens, which were, however, neutralized in vaccinated fish after challenge. In situ hybridization showed increased numbers of B cells in the heart in response to SAV challenge. Massive migration of B cells from the lymphatic organ (spleen) to the infected site (heart) was proven in vaccinated but not in control salmon, and this alleviated the disease. In addition, we showed strong and rapid responses of polyspecific antibodies to vaccination and infection and a high correlation with levels of vaccine-specific antibodies. The study gained new knowledge on the mechanisms of vaccine responses in salmonids. Multiplex immunoassay has been established as a time -and cost saving alternative for the assessment of humoral immunity.
MGE was developed on the Fludigm platform based on Nofima's long-term experience and resources in Atlantic salmon transcriptomics (database with >100 trials and >5000 microarrays). Genes were selected to represent functional groups and pathways of the immune system giving preference to genes that have shown strong and consistent responses to pathogens and related challenges. A database with client program was constructed for storage, management, and analysis of MGE data. The first version with 92 immune - and stress genes and four reference genes was tested on samples from seven independent projects that covered the production period from the start feeding to several months in the sea, different facilities, and regions of Norway. This stage pursued technical challenges: figuring out which tissues work best for the discrimination and how many genes are required. Gill was selected for continuation, because it is suitable for non-invasive live sampling and shows strong responses to challenges. A reference set included 650 gill samples from healthy salmon. In each comparison, not more than ten genes were required for discrimination of any arbitrary groups and 48 genes including two reference genes (next smaller Fluidigm format) were sufficient for implementation of any task. Second version of MGA was used with field samples. A proof-of-concept trial compared batches of smolts with low, intermediate (IM) and high (HM) mortality (Pharmaq Analytic). We anticipated different types of compromised immunity: suppression, unhealthy stimulation due to infection and loss of balance due to many up and downregulated genes. Two scenarios were observed. IM group showed general suppression of immunity and all HM fish were above the threshold by the squared deviation from the reference. Later, similar result was obtained for farmed salmon from the Polar region. A small 24-genes assay was suggested for diagnostics of acute conditions.
Two longitudinal studies were performed on salmon produced in traditional flow through and modern RAS, respectively, using the entire toolbox. MGE showed steady increase of expression of immune genes after seawater transfer with no significant effect of other factors (light regimen, salinity and smolt size). Though differences between the aquaculture systems were observed, gene expression and circulating antibody levels equalized in the end of the study period.
In conclusion, our results suggest that farmed salmon are sufficiently robust to cope with changes in the production. Monitoring is recommended for detection and mitigation of problems.
The project developed methods for assessment of immune competence of Atlantic salmon smolts and growers that have been validated on field material and can be transferred to the industry. The toolbox includes multigene expression assays supplemented with database, computer program, and reference data set and antibodies assays. Field research showed high adaptability of Atlantic salmon to different aquaculture systems and production methods and indicated problems that require monitoring of the immune status."
Keywords
Genetic;
Fish;
Salmon;
Fish biology;
Fish health;
Diagnostic application;
Marine Region
76
Not associated to marine areas
0
Marine Region Map
