title: Antibody-antigen kinetics following immunization of rainbow trout (Oncorhynchus mykiss) with a T-cell dependent antigen.
abstract: Enhancement of the immune response through affinity maturation of the antibody response is a feature of the mammalian immune system and has important implications with respect to development of vaccination strategies. However, an absence of germinal centres and apparent lack of somatic hypermutation of immunoglobulin V genes suggests that this phenomenon does not occur in fish. We investigated the question of affinity maturation in rainbow trout (Oncorhynchus mykiss) by measuring antibody-antigen binding kinetics using a BIAcore biosensor. Following immunization with a T-cell dependent antigen (FITC-KLH), relative binding affinities of serum and mucosal antibodies were assessed based on their dissociation rate constants (k(diss.)). A detectable serum anti-FITC response developed by 4 weeks post-immunization, and a consistent shift to higher affinity antibody production (i.e. a decrease in k(diss.)) was observed over the ensuing course of the immune response. An average k(diss.) of 3.5 x 10(-4)+/-0.27 x 10(-4)sec(-1) was observed during early stages of the response (4 weeks), while by 6 weeks this decreased significantly (p<0.05). Further reduction in k(diss.) was observed, with a low of 1.2 x 10(-4)+/-0.06 x 10(-4)sec(-1) being observed by week 12. Analysis of the anti-FITC response in skin-derived mucus revealed a similar pattern of decreasing k(diss.) as the immune response progressed. While these data clearly demonstrate a 2-3 fold increase in antibody-antigen binding during the course of the immune response in trout, the magnitude of this increase is much less than that seen in the mammalian immune response. This may reflect differences in the mechanisms underpinning this phenomenon in divergent species.
authors.affiliation: Immunobiology Unit and The Cooperative Research Centre for Aquaculture, Department of Cell and Molecular Biology, University of Technology Sydney, P.O. Box 123, Broadway, NSW 2007, Australia. kcain@uidaho.edu
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Cain
authors.forename: Darren R
authors.initials: DR
authors.lastname: Jones
authors.forename: Robert L
authors.initials: RL
authors.lastname: Raison
mesh_terms: D000818:Animals; D000915:Antibody Affinity / Q000276:immunology*; D000936:Antigen-Antibody Complex / Q000276:immunology*; D015374:Biosensing Techniques / Q000662:veterinary; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives*; D006433:Hemocyanins / Q000031:analogs & derivatives* / Q000276:immunology*; D018928:Immunity, Mucosal / Q000276:immunology; D007114:Immunization / Q000662:veterinary*; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000276:immunology; D007700:Kinetics; D017686:Oncorhynchus mykiss / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000936:Antigen-Antibody Complex; D018984:Epitopes, T-Lymphocyte; D007075:Immunoglobulin M; C088472:fluorescein isothiocyanate-keyhole limpet hemocyanin; D006433:Hemocyanins; D016650:Fluorescein-5-isothiocyanate