Fish immunology - Arctic char

Farming af Arctic char (Salvelinus alpinus) has been increasing over the past two decades. One of the main tenets of successful fish farming is disease control, and knowledge about how to diagnose and reduce the incidence of diseases.

The aim of our work on Arctic char has been to gather information about the innate and adaptive responses to two bacteria, i.e. Aeromonas salmonicida ssp. achromogenes (Asa) and Renibacterium salmoninarum (Rs).

Infection experiments were performed, using relatively low infections titers, to enhance the possibility of detecting activation of both the innate and adaptive immune response. The experiment with Rs lasted 70 days, but 13 days with Asa.

The activation of the immune response to these bacteria was monitored by gene expression changes of key immune genes, both by RTqPCR and transcriptome sequencing. The gene expression studied by RTqPCR was that of IL1b, IL8, TGFb1, IL4/13a, IFNg, NADPH, hepcidin, transferrin, and CRP1. The results of the RTqPCR measurments showed activation of the immune response in both infections, but did not give decisive results regarding activation of the adaptive response.

To get a better understanding og the immune response, transcriptome sequencing was performed on selected samples. This gave information about expression changes for all Arctic char genes during the infections. Data analysis, e.g. regarding activation of CD4+ T-helper cells, showed indications of Th1 and Th2 activation in the Rs infection. When the Asa transcriptome data was studied, there were signs of suppression of immune pathways, that was not seen in the Rs infection, for example regarding Th1 and Th2 responses. Analysis of the data is an ongoing project.

Group leader: Birkir Þór Bragason