Immunochemical purification and characterization of a 74.0-kDa Schistosoma mansoni antigen

A polypeptide antigen of 74.0 kDa molecular weight was detected in the antigenic extracts of the 3 developmental stages of Schistosoma mansoni (eggs, cercariae, and adult worms) by western blotting using BRL4 monoclonal antibody (mAb) that significantly protected mice at the levels of 51.6%, 42%, and 53.8% against challenge S. mansoni infection in 3 separate experiments. This antigen was isolated and purified from crude soluble worm antigen preparation by immunoaffinity chromatography using CNBr-activated sepharose-4B beads coupled with the BRL4 mAb. The purified antigen showed a single peak when analyzed by both high-performance liquid chromatography and high-performance capillary electrophoresis. The 74-kDa antigen was characterized as a protein in nature with 56.9% hydrophilic amino acids and 43.1% hydrophobic amino acids. This antigen was detected in 93% of urine samples from infected cases with specificity of 89% among noninfected cases using an enzyme immunoassay-fast dot-enzyme-linked immunosorbent assay based on BRL4 mAb.