Atlantic salmon scale explants in bacteria-host interaction studies: in vitro challenge model.

Atlantic salmon scale explants is a promising model for bacterial challenges. Exposure to pathogens (Moritella viscosa and Tenacibaculum finnmarkense) and commensal bacteria consistently upregulated a suite of immune genes in a dose response manner. This panel includes chemokines, cytokines, genes involved in eicosanoid metabolism, and both humoral and cellular effectors. The prevalence of genes related to signaling and communication suggests that salmon scales function as sentinels, mobilizing immune responses upon encountering bacteria. While common immune responses were evident across all trials, scales also revealed differences between bacterial species. Combining commensal bacteria with M. viscosa enhanced responses to pathogens, and differences were observed between M. viscosa and T. finnmarkense. The effects of commensal bacteria varied in magnitude. Exposed cells showed changes in morphology and increased iNOS expression. The data set includes four experiments with similar setup. Cultures of scale explants were exposed to pathogenic or commensal bacteria in marine broth medium (or only medium in controls) for 2h. The cell culture medium was thereafter removed, scale explants were washed twice and replaced with fresh medium including antibiotics. Cells were harvested 24 hours post-exposure.