Characterization of a monoclonal antibody against the 47- kDa antigen of Cryptobia salmositica Katz and its use in an antigen-capture enzyme-linked immunosorbent assay for detection of parasite antigen in infected rainbow trout, Oncorhynchus mykiss (Walbaum) |
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| Authors: | C K Verity P T K Woo |
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| Institution: | Department of Zoology, University of Guelph, Guelph, Ontario, Canada |
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| Abstract: | A monoclonal antibody (designated MAb-007) was produced against the pathogenic haemoflagellate Cryptobia salmositica Katz. This IgG3 antibody recognized the 47-kDa antigenic polypeptide of C. salmositica (SDS-PAGE and Western immuno-blotting). The antibody did not agglutinate live parasites, and there was no change in the staining intensity of the 47-kDa band on Western immunoblots after immunoabsorption of MAb-007 with live intact parasites. The 47-kDa antigen recognized by MAb-007 was localized in the cytoplasm of the parasite (immunogold labelling and electron microscopy). The monoclonal antibody cross- reacted with the 47-kDa polypeptides of C. bullocki Srrout and C. catostomi Bower & Woo. It was used in an antigen-capture ELISA for the detection of parasite antigen in the plasma of rainbow trout inoculated with the parasite, or with an attenuated vaccine strain of C. salmositica. All pre-infection plasma were negative while all infected fish with detectable parasitaemias were positive for antigen at 1–9 weeks after infection. Parasite antigen was even detected in vaccinated fish that were negative for parasites using the wet mount microscopic technique. The antigen-capture ELISA detected C, salmositica antigen in whole cell lysate preparations at concentrations as low as 0.5 μg ml-1. Fifty microlitres of fish plasma was required in the antigen-capture ELISA, and the use of a plate reader and 96-well plates facilitated rapid analysis of a large number of plasma samples. The sensitivity of the assay makes it a potentially useful tool for detection of Cryptobia infections. |
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