IMPROVED DETECTION OF CIRCULATING ANTIGEN IN CATTLE INFECTED WITH TAENIA-SAGINATA METACESTODES

In order to improve the sensitivity and the specificity of an existing IgM monoclonal antibody-based ELISA (Brandt et al., 1992) for the det ection of circulating antigen in the sera of cattle infected with T. s aginata metacestodes, a modified sandwich ELISA was developed. Monoclo nal antibodies (MAbs) of the IgG isotype were produced against the exc retory-secretory (ES)products of T. saginata metacestodes. Since it wa s shown that the affinity of these IgG MAbs for ES antigen was higher than that of the IgM MAbs, the latter were replaced by two IgG1 MAbs ( 158C11 and 60H8). Furthermore, heat treatment of the sera significantl y increased the OD-values of ES-spiked serum samples as compared to no ntreated samples. It also decreased the number of false positive react ions. When the original IgM MAb-based ELISA was compared with the IgG MAb-based ELISA using heat treated sera from animals harbouring more t han 50 living metacestodes of T. saginata, the sensitivity increased f rom 56% with the former to 92% with the latter assay. Only a small per centage of animals carrying less than 50 cysts were detected both with the ELISA using IgG or IgM MAbs. The specificity of the IgM- and IgG MAb-based ELISAs was 93.4% and 98.7% respectively. (C) 1998 Elsevier S cience B.V.