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 detection of circulating antigen in the sera of cattle infected with T. saginata metacestodes, a modified sandwich ELISA was developed. Monoclonal antibodies (MAbs) of the IgG isotype were produced against the excretory–secretory (ES)-products of T. saginata metacestodes. Since it was 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 significantly increased the OD-values of ES-spiked serum samples as compared to nontreated samples. It also decreased the number of false positive reactions. When the original IgM MAb-based ELISA was compared with the IgG MAb-based ELISA using heat treated sera from animals harbouring more than 50 living metacestodes of T. saginata, the sensitivity increased from 56% with the former to 92% with the latter assay. Only a small percentage 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.