Adaptive antiviral cell-meditaed immune reactions agäinst IHNV in rainbow trout (Oncorhynchus mykiss)

• Applicant: Privatdozent Dr. Uwe Fischer
• Subject Area: Animal Breeding, Animal Nutrition, Animal Husbandry
• Term: from 2010 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 126382186

Cell-mediated cytotoxicity (CMC) is an important immune response mechanism in virus-infected hosts. Viruses replicate intracellularly and their proteins are cleaved by the host cell's proteasome to peptides that can be bound to MHC class I/beta2m monomers. This complex is finally presented on the host`s cell surface to the T cell receptors (TCR) of cytotoxic T lymphocytes (CTLs) triggering clonal expansion of antigen-specific CTLs. These mechanisms are likely to exist in fish because homologues of the main molecules involved in MHC class I loading and presentation have been discovered. Also, functional studies on the effector mechanisms lead to this suggestion. A significant part of these data were obtained in the laboratory of the applicant and his collaborators. However, in fish there is no information available yet on viral peptides presented by infected cells, nor do tools exist for CTL labelling. Knowledge on these immune response mechanisms will be extremely useful to understand the mechanisms of antiviral immune responses especially in the commercial fish species rainbow trout and for economically important viral infections such as infectious haematopoietic necrosis (IHNV).An aim of the initial project was:I. Analysis of viral peptides presented by MHC class I molecules on IHNV infected trout cells.For this, MHC class I presented IHNV-derived peptides were predicted and their capacity to stabilize recombinant MHC class I and beta2m protein complexes.The remaining aim of the renewal proposal will be: II. Analysis and characterization of IHNV-specific cytotoxic cells using virus-peptide loaded MHC class I tetramers.Fluorescence labelled in vitro synthesized MHC class I/beta2m tetramers loaded with the synthetic peptides will be used for the identification and separation of IHNV peptide-specific CTLs to study their gene expression profile, homing and cytotoxic properties. In conclusion, detailed knowledge of antiviral cell-mediated immune reactions in rainbow trout will give further insight into the evolution of the vertebrate immune system (1), add to the understanding of fish immune responses (2) and will finally allow to specifically design urgently needed anti-viral vaccines in fish facilitating an efficient antigen presentation (3).

• DFG Programme: Research Grants