Quantification of circulating schistosome antigen by monoclonal antibody-based enzyme-linked immunosorbent assay

A two-site enzyme-linked immunosorbent assay (2S-ELISA) was developed for the quantification of gut-associated schistosome circulating anodic proteoglycan (GASCAP) of Schistosoma japonicum using a monoclonal antibody (McAb M120), purified by one-step hydroxylapatite (HAP) chromatography, as both solid phase and peroxidase-conjugated reagent. In this system, a high detectable level of serum GASCAP concentration (0.25 microgram/L) could be achieved with the immunoaffinity purified GASCAP being used as the standard. The specificity of the assay was 97.2%, with minimized interference of rheumatoid factor. The intra-assay (4.01%) and interassay (6.09%) coefficients of variation and the mean analytical recovery (101.4%) for GASCAP demonstrated the precision and accuracy of the assay.