Innate immunity in teleosts

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My research program and the studies outlined in the present short-term objectives are designed to better understand innate resistance of fish to infectious disease. Aquaculture is responsible for more than half of all fish protein consumed worldwide and infectious disease is an important cause of lost production. Aquaculture is a growth industry for Canada and will continue to expand and support Canadian jobs in the future. The cost-benefit ratio (relatively low cost per unit product) for fish health requires that we identify innate markers for resistance to infectious disease to provide enhanced survival, without heavy reliance on antimicrobials or expensive products. Two important diseases of rainbow trout (RT) are viral hemorrhagic septicemia virus (VHSV) and Flavobacterium psychrophilum, the cause of bacterial coldwater disease (BCWD). BCWD is the most economically important disease of trout in North America and VHSV, as a reportable disease, is always of concern. The gill epithelium and the splenic macrophage are key cells that provide for resistance from VHSV and BCWD, respectively. The antimicrobial capabilities of the gill epithelium, which would limit initial VHSV replication, are critical to reduce systemic spread and mortality and the propsed research will use a cell line derived from RT gill epithelium. A RT splenic macrophage cell line will also be used to model killing of F. psychrophilum. Stimulation of antiviral and antibacterial resistance by using relatively cost-effective microbial patterns/structures is one potential outcome of this research. Finally, this research will examine a potentially very important phenomenon that we have discovered regarding resistance to BCWD. Trout which were fed a mycotoxin commonly found in commercial aquaculture feeds, or trout which were on a restricted diet, were actually less susceptible to experimental infection. We hypothesize that this mechanism is due to induction of a cell pathway termed autophagy that can limit the growth of intracellular organisms. Understanding this phenomenon could have important implications for reducing production losses and mortality in aquaculture. An important benefit of this research program would be reduced reliance on antimicrobial use in farmed fish and improved efficiency in the cost of production. This funding will also train at least four high quality personnel in applied and basic aquatic animal health and will ideally position them for employment in the allied health industry, either in positions directly related to aquaculture or in other fields.