Immunity to rhabdoviruses in rainbow trout: the antibody response

Interactions between host and pathogen, as in the case of fish pathogenic viruses, represent interesting models for analyses of the relationships between structure and function of the teleost immune system. Two salmonid rhabdoviruses, IHNV and VHSV, have received special attention due to their occasional detrimental effect on rainbow trout farming. Research efforts have been focused on understanding the mechanisms involved in protective immunity. Several specific and nonspecific cellular and humoral parameters are believed to be involved, but only the antibody response has been characterised in detail so far. Analysis of the specificity of anti-virus trout antibodies has been complicated by a generally insufficient ability of the antibodies to bind the viral proteins in assays such as immunoblotting. However, other assays, specifically designed for detection of fish anti IHNV/VHSV antibodies, have demonstrated that rainbow trout can produce specific and highly functional antibodies that are able to neutralise virus pathogenicity in vitro as well as in vivo. The apparently more restricted antibody response to IHNV and VHSV antigens in fish compared to mammals could possibly be explained by different kinds of epitopes being differently immunogenic in fish and in mammals. Also, it may be assumed that the requirements for the assay-antigens in terms of antigenicity, may differ for mammals and fish. The present text includes an initial presentation of the pathogens, followed by basic and applied aspects of antibody response and antibody reactivity with IHNV and VHSV antigens.