Title: Evaluation of the protective efficacy of Flavobacterium psychrophilum O-polysaccharide-protein conjugate in rainbow trout (Oncorhynchus mykiss)
Student: Benjamin R. LaFrentz
Department: Fish & Wildlife Resources and the Aquaculture Research Institute
Flavobacterium psychrophilum is the etiological agent of coldwater disease (CWD) and rainbow trout fry syndrome (RTFS) and has emerged as one of the most significant bacterial pathogens in salmonid aquaculture in the Pacific Northwest and worldwide. This bacterium is especially problematic for restoration programs of native steelhead (Oncorhynchus mykiss), coho salmon (O. kisutch), chinook salmon (O. tshawytscha), and sockeye salmon (O. nerka) that are endangered and/or threatened species. Much research is being devoted to the development of an efficacious vaccine, since current disease prevention options are inconsistent and many times ineffective. Previous studies in our laboratory and others have suggested that the O-polysaccharide (O-PS) component of the lipopolysaccharide (LPS) of F. psychrophilum is highly immunogenic and may have been involved in eliciting a protective immune response following challenge with F. psychrophilum. We proposed to test the protective efficacy of the O-PS of LPS conjugated to a carrier protein, however, recent findings in our laboratory suggest that the carbohydrate antigens referred to as high molecular mass LPS with O-PS are likely the repeating carbohydrate antigens of the glycocalyx of F. psychrophilum and not LPS. Therefore, we will re-direct our research to further characterize and determine the protective ability of the glycocalyx. Initial studies will involve sodium dodecyl sulfate-polyacrylamide gel electrophoresis of LPS preparations and western blotting to demonstrate the presence of and distinct differences between the LPS and glycocalyx. Passive immunization experiments will also be conducted using a monoclonal antibody specific for the glycocalyx to determine if antibodies specific for this antigen are protective in rainbow trout. If these antibodies provide protection against F. psychrophilum challenge, then methods to purify the glycocalyx will be examined in order to test the glycocalyx as a vaccine candidate antigen for the prevention of CWD and RTFS.
For more information, email the PI: Dr. Kenneth Cain