A defined antigen for the serodiagnosis of Taenia ovis infections in dogs.

The evaginated scolex of Taenia ovis secretes an antigen complex into defined culture medium that has been used to develop a cestode-specific enzyme-linked immunosorbent assay (ELISA). We now describe an immunoblot test for antibodies to T. ovis based on the recognition of a 94-kDa antigen band in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of T. ovis scolex secretions. The test was specific for cestode infections in dogs and was 82% sensitive for the recognition of T. ovis infections. Affinity-purified antibody uniquely recognizing this 94-kDa band was used to screen a cDNA expression library constructed utilizing mRNA from newly evaginated T. ovis scoleces. The cDNA from putative positive bacteriophage were subcloned into the plasmid pGEX and expressed as fusion proteins with schistosome glutathione-S-transferase (GST). The expressed fusion proteins were purified using glutathione-agarose beads. The recombinant parasite antigen was either eluted as a fusion protein with GST or cleaved from GST using a restriction protease. Some dog sera reacted with the GST molecule. However, the recombinant cleaved antigen from 1 clone, T. ovis 40, showed 42% sensitivity and 100% specificity for cestodes in an ELISA using test sera from dogs monospecifically infected with T. ovis and preabsorbed with bacteria. Some sera from dogs monospecifically infected with other cestode species (Taenia pisiformis, 30%; Taenia hydatigena, 30%; Echinococcus granulosus, 20%) reacted with the cloned antigen.