IMMUNOGENETICS OF DISEASE RESISTANCE IN SALMONIDS AND THE DEVELOPMENT OF A USEFUL MODEL TO STUDY RESISTANCE

¹ Department of Animal Sciences, Washington State University, Pullman WA 99164-6351

² Basel Institute for Immunology, 487 Grenzacherstrasse, CH-4005, Basel, Switzerland

³ Department of Microbiology, Oregon State University, Corvallis OR 97331

⁴ Department of Genetics, Animal Science Institute, Agricultural Research Organization, Bet Dagan 50250, Israel

⁵ TroutLodge Sumner WA 98390

⁶ School of Biological Sciences, Washington State University, Pullman WA 99164-4236

Rainbow Trout Oncorhynchus mykiss, like mammals, possess both innate and adaptive immune responses. They have B cells, NK-like cells, T-like responses and a complex mucosal immune system. Unlike mammals, genes encoding MHC I (UAA) and MHC IIbeta (DAB) are unlinked (Hansen, J. Immunol., 1999). Like mammals, rainbow trout are subject to many disease pathogens. Two of these are infectious hematopoietic necrosis virus (IHNV), whose economic impact is felt worldwide, and Ceratomyxa shasta, a myxosporean parasite of wild salmon and rainbow trout in the Pacific NW and Canada. In the past, it has been noted that several species of salmonids were resistant to IHNV. Several of us are now studying the relationship of MHC to resistance to IHNV. Palti et al. have noted association of polymorphisms in MHCIIbeta and IHNV resistance in backcrosses of outbred rainbow trout and cutthroat trout. Bartholomew demonstrated that resistance to C. Shasta was passed as a dominant trait among progeny of crosses between the resistant Klamath and the susceptible Cape Cod strains of rainbow trout. Homozygous clones of trout [Hot Creek(HC), Arlee(A), OSU(O), Clearwater River(C), Swanson River(S)] are being developed in the Thorgaard laboratory as models for genetic studies. Ristow, using the clones and their doubled haploid progeny has demonstrated that nonspecific cytotoxic cell activity may be encoded by one gene. Bartholomew showed that the O X A F1 were highly susceptible to C. Shasta whereas O X C F1 were resistant. It is our intention to disseminate these trout to qualified laboratories working on the immunogenetics of disease resistance.