Detection of circulating excretory secretory antigens in human fascioliasis by sandwich enzyme-linked immunosorbent assay.

We developed a sandwich enzyme-linked immunosorbent assay to detect circulating parasite antigen in humans with fascioliasis. The assay uses antibodies against Fasciola hepatica excretory secretory (ES) antigens. A monoclonal antibody was used to capture circulating ES antigens, and a human polyclonal antibody peroxidase conjugate was used to identify circulating ES antigens. Optimal dilutions of all reagents were determined by block titration. The antigen concentration in sera from patients was estimated by comparing the optical density at 492 nm of test sera with a standard curve. All of the serum samples from 25 patients with parasitological evidence of fascioliasis had a detectable antigen concentration (more than 10 ng/ml). None of the serum samples from 80 patients infected with parasites other than F. hepatica showed a positive reaction, suggesting the absence of cross-reactions in this assay.