Immunization of rainbow trout Oncorhynchus mykiss (Walbaum) with a crude lipopolysaccharide extract from Flavobacterium psychrophilum

Authors

  • Benjamin R LaFrentz,

    1. Department of Fish and Wildlife Resources and the Aquaculture Research Institute, University of Idaho, Moscow, ID, USA
    Current affiliation:
    1. United States Department of Agriculture, Agricultural Research Service (USDA-ARS), Aquatic Animal Health Research Unit, Auburn, AL, USA
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  • Scott E LaPatra,

    1. Research Division, Clear Springs Foods, Inc., Buhl, ID, USA
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  • Douglas R Call,

    1. Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
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  • Kenneth D Cain

    Corresponding author
    1. Department of Fish and Wildlife Resources and the Aquaculture Research Institute, University of Idaho, Moscow, ID, USA
    • Correspondence: K D Cain, Department of Fish and Wildlife Resources and the Aquaculture Research Institute, University of Idaho, P.O. Box 441136, Moscow, ID 83844-1136, USA.

      E-mail: kcain@uidaho.edu

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Abstract

Control methods for Flavobacterium psychrophilum are limited and oftentimes ineffective; hence, research efforts have focused on vaccine development. This study tested the hypothesis that a crude lipopolysaccharide (LPS) extract from F. psychrophilum will elicit a protective immune response in rainbow trout Oncorhynchus mykiss (Walbaum) against F. psychrophilum challenge. Rainbow trout (mean weight, 3 g) were immunized intraperitoneally with the following treatment and control preparations: 10 μg of crude LPS with or without Freund's complete adjuvant (FCA), 25 μg of crude LPS with or without FCA and saline with or without FCA. Immunization of fish with 10 or 25 μg of crude LPS/FCA resulted in significant antibody responses against F. psychrophilum using ELISA with a whole-cell lysate as the coating antigen, but only minimal levels of protection were conferred following F. psychrophilum challenge at 14 weeks post immunization. Western blot analyses demonstrated that fish exhibited antibodies specific for low-molecular mass proteins present in the crude LPS extract, but did not exhibit antibodies specific for F. psychrophilum LPS. The results indicate that higher immunization doses and/or the use of an alternative extraction method that yields larger LPS molecules (23–70 kDa) may be necessary to elicit specific antibody responses against F. psychrophilum LPS.

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