( Kenneth D. Cain 1 Les...)Separation and Comparison of Proteins From Virulent and Nonvirulent Strains of the Fish Pathogen Flavobacterium psychrophilum, Using a 2-D Electrophoretic Approach

Kenneth D. Cain¹ , Leslie Grabowski¹ , and Scott E. LaPatra²
1 Department of Fish and Wildlife Resources, University of Idaho, Moscow, ID USA
2 Clear Springs Foods Inc., Research Division, PO Box 712, Buhl, ID USA

Introduction
Coldwater disease (CWD) is a worldwide problem in commercial (foodfish) aquaculture as well as public resource enhancement hatcheries, and is caused by the gramnegative bacterium Flavobacterium psychrophilum. Juvenile trout and salmon infected with this disease experience high mortalities, and surviving fish often exhibit skeletal deformities associated with spinal compression. Aquaculture vaccines have become important tools in preventing fish diseases, but a commercial vaccine is not currently available for CWD. Development in this area has likely been hampered by altered expression of virulence factors among different strains of F. psychrophilum and an incomplete understanding of the immune response of fish to this pathogen. It has been noted that protease differences exist between strains (Dalsgaard 1993, Bertolini et al. 1994, Madsen and Dalsgaard 1999), but the identities of these components and roles they play in the fish immune response are unknown. Significant protection has been observed under laboratory conditions following immunization with F. psychrophilum (Holt 1988, Obach and Laurencin 1991), but antigenicity appears to be strain dependent.

A study is currently underway in our laboratory using twodimensional polyacrylamide gel electrophoresis (2-D PAGE) to identify antigens and virulence factors of this bacterium that may be targeted for the development of an efficacious vaccine for the aquaculture industry. 2-D gel profiles of virulent and nonvirulent strains are being compared to iden
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