title: Protective immunity in rainbow trout Oncorhynchus mykiss following immunization with distinct molecular mass fractions isolated from Flavobacterium psychrophilum.
abstract: Vaccine development for coldwater disease (CWD), also known as rainbow trout fry syndrome (RTFS), has been based primarily on whole-cell bacterins or outer membrane fractions of Flavobacterium psychrophilum. In the present study, immunogenic regions of the bacterium corresponding to 18-28, 41-49, and 70-100 kDa were identified by western blot analysis using rainbow trout Oncorhynchus mykiss immune sera. Following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), antigens within these regions were isolated by electro-elution and used in immunization trials. Groups of rainbow trout fry were immunized with these regions emulsified with Freund's complete adjuvant (FCA) and a formalin-killed bacterin emulsified with FCA. It was demonstrated that the 70-100 and 41-49 kDa regions and F. psychrophilum treatments elicited significant protection when compared to the saline control following subcutaneous challenge with 2 doses of a virulent strain of F. psychrophilum. Immunization with the 70-100 kDa region resulted in near complete protection in fish with mean cumulative percent mortality (CPM) of 6% and mean relative percent survival (RPS) of 94% at the lower challenge dose (6.25 x 10(6) colony forming units fish(-1)). This preparation also stimulated a high level of specific antibody to F. psychrophilum, as detected by an enzyme-linked immunosorbent assay (ELISA). Western blot analysis using sera from fish immunized with the 70-100 kDa region demonstrated that high molecular weight proteins and the O-polysaccharide component of lipopolysaccharide (LPS) are recognized by serum antibodies. This suggests that these antigens may be involved in eliciting a highly protective immune response, and could serve as vaccine candidates.
authors.affiliation: Department of Fish and Wildlife Resources, Aquaculture Research Institute, University of Idaho, Moscow, Idaho 83844-1136, USA.
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: LaFrentz
authors.forename: Scott E
authors.initials: SE
authors.lastname: LaPatra
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Jones
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Cain
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology*; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005393:Fish Diseases / Q000276:immunology* / Q000401:mortality / Q000517:prevention & control; D045826:Flavobacteriaceae Infections / Q000276:immunology / Q000401:mortality / Q000517:prevention & control / Q000662:veterinary*; D005417:Flavobacterium / Q000276:immunology*; D005620:Freund's Adjuvant; D007106:Immune Sera / Q000276:immunology; D007114:Immunization / Q000662:veterinary*; D017686:Oncorhynchus mykiss
chemical_list: D001428:Bacterial Vaccines; D007106:Immune Sera; D005620:Freund's Adjuvant