Antigen presentation in teleost fish

diagram showing Antigen presentation in teleost fish
This research project examines one the basic mechanisms of immunity in teleost fish, antigen presentation. This process takes peptide fragments of pathogens and loads them into major histocompatibility complex receptors, which carry the peptides to the cell surface and present them to T-cells. These T cells then initiate immune responses. There are two distinct pathways, exogenous for peptides of extracellular pathogens, like bacteria, and endogenous for peptides derived from intracellular pathogens, such as viruses. Antigen presentation involves several chaperones and we are investigating which in particular participate in teleost fish antigen presentation, the order they participate and the regulation
of their expression by infection and environmental factors. Additionally, we are extracting the peptides from trout MHC receptors in order to sequence them and find which fragments of pathogenic proteins are targeted. This will help us understand the process of fish immune responses to pathogens, providing key information that will assist in the design of better vaccines for aquaculture. (NSERC discovery grant)

Environmental effects on Arctic charr immunity and populations

Arctic charr are the northernmost freshwater fish, with a circumpolar distribution. They live and breed in coldwater lakes, often the only fish species present. In many cases they have diversified into several different morphotypes, each occupying a different ecological niche. Molecular markers which are used for population discrimination often do not work on Arctic charr because the lakes they inhabit were formed only after the most recent glaciation and a timescale of less than 10,000 years is not sufficient for neutral genetic differences to arise. We are examining Arctic charr populations using MHC gene polymorphism (variation) because, as a selectable marker, it can evolve over much shorter time periods.  Differences in circumpolar populations at global, regional and local scale will be examined. Additionally, correlating MHC diversity with parasite and pathogen load over a latitudinal gradient and temperature effects on Arctic charr MHC gene expression will be examined. This project will aid in understanding the effects of climate change on fish populations in the Arctic, a region where the effects will be among the most dramatic (Canadian Research Chair funding).

Using MHC gene polymorphism to define lake trout populations

Lake Trout are also a coldwater fish that has developed a population structure in lakes which have formed since the last period of glaciation. Previous work using neutral genetic markers have shown a distinct population structure formed when fish from glacial refugia repopulated newly forming lakes. This project examines these same populations for genetic structure using MHC polymorphism to see if selectable markers mirror what is seen by neutral markers and also if there is recent evidence of the effect of stocking on lakes in Ontario. This project will aid in understanding the effects of global warming and stocking on Lake trout populations. (Funding from Ontario Ministry of Natural Resources).

Understanding immune responses to flavobacterium in rainbow trout

dead rainbow trout
Bacterial coldwater disease (BCWD), caused by Flavobacterium psychrophilum, has a marked deleterious impact on the freshwater salmonid aquaculture in Canada. With mortality of some trout strains approaching 20-30% and associated heavy antimicrobial use, the costs of the disease are substantial and the risk of antimicrobial resistance is serious. In spite of the obvious need, there are no commercial vaccines available. Further, breeding programs are currently underway to improve the growth of rainbow trout, but it is imperative that any gains made via a family selection program aren't negated by increased mortality or other costs due to BCWD. For these reasons, development of effective management tools to reduce the deleterious impact of this disease are needed. This project therefore has three major goals:

  1. to evaluate cold-induced genes and proteins as vaccine candidates
  2. to identify BCWD resistant and susceptible families of rainbow trout that can be used to understand the immunological basis for disease resistance by determining which families carry MHC alleles that confer either resistance or susceptibility to infection 
  3. to better characterize the humoral and cell-mediated immune response stimulated by vaccination and to natural and experimental infection by examining oxygen burst of both blood neutrophils and head kidney macrophage, antibody responses to the pathogen and cytokine responses by using unique assays that we have developed.

This project will assist in developing strategies to combat losses to this disease by the aquaculture industry (NSERC strategic grant).

Developing diagnostic assays to fish cytokines

Fish health is a serious concern for the aquaculture industry. Monitoring of fish health however is hampered by our limited knowledge of the mechanisms that control fish immunity. While we have sequenced fish genomes and have studied the expression of the genes involved in immunity in important aquaculture species, knowledge on the actual functions carried out by the proteins these genes encode is limited. This is particularly true for cytokines, which are small proteins secreted by immune system cells to pass signals to other cells. These molecules control immune responses. In fish, there are no commercially available antibodies to these molecules, a pre-requisite for detailed studies on any protein’s function.  This proposal will make antibodies to four of the most important signaling molecules in the salmonid immune system ad use those antibodies to develop assays that can determine which cells are secreting these cytokines, as well as the amount of cytokine being secreted.  Cedarlane Laboratories will market these products, as well as the antibodies and recombinant proteins used to make the assays as these have uses of their own in research. Since there are no current products available world-wide that can assess cytokine function in teleost fishes, Cedarlane would instantly corner the global market. These assays can then be used by researchers worldwide to advance out knowledge of fish immunity, providing benefits for the aquaculture and aquaculture diagnostics/vaccine development industries. (Cedarlane Labs, Ontario Centre of Excellence, NSERC CRD grant).

Genetic improvement of Chinook salmon aquaculture stocks

Brian Dixon on a dock
Capture fisheries alone are unable to sustain demand for seafood, and aquaculture is a growing source for that demand. Salmon farming is one of Canada’s growing industries and is extremely valuable (>$1,000 million in 2010; Stats Canada). However, salmon farming must balance production economics with environmental impacts. Farmed Chinook salmon are a valuable niche market with substantial growth potential, coupled with lower perceived environmental concerns (being a native species); however, their performance has not been systematically assessed. We will develop a performance-enhanced hybrid Chinook salmon stock with enhanced survival and growth and reduced feed costs. The new stock will use less wild-sourced lipid and protein for feed and minimize less therapeutants for disease control, thereby minimizing the environmental footprint. The project will generate data on Chinook salmon production stocks that will serve to improve salmon farming efficiency which will help make Canada a global leader in Pacific salmon farming.

The proposal involves close collaboration among leading researchers at three Universities, commercial salmon farms & related industries, and government and NGO agencies charged with fish management. Performance will be measured in offspring from crosses between inbred farmed and wild stocks: those offspring are expected to exhibit hybrid vigour, analogous to hybrid corn lines. We will rear the offspring in a range of environments (semi-natural channels to standard farm conditions), and compare performance as measured by molecular, physiological, and behavioural aspects of growth, survival and reproduction. Specifically, we will test for stock, environmental and interactions effects on growth, feeding and competitive ability, disease resistance, immune function, gene expression, and metabolic processes. The optimized commercial hybrid stocks, calibrated for variation in rearing conditions, will be marked domestically and internationally, supporting the economic and environmental development of Canada's large and growing aquaculture industry. Our research will also address important questions in the conservation and evolutionary biology of salmonids. (NSERC strategic grant).