Mice infected with 80 cercariae of Schistosoma mansoni were treated with a single oral dose of oxamniquine (400 mg/kg) 65 days after infection. 2. Groups of 8-12 animals were sacrificed approximately 2 weeks after treatment and then at monthly intervals. The sera obtained were evaluated for S. mansoni antibodies by enzyme-linked immunosorbent assay (ELISA) at 1:200 dilution. 3. Worms could not be recovered on days 14, 28, 58, 90, 119, 154 and 180 after treatment, indicating the efficacy of the chemotherapy. 4. When performed with different antigens obtained from several stages in the life cycle of S. mansoni, i.e., soluble egg antigen, adult worm tegument, cercaria antigen, schistosomule tegument and adult worm (10 micrograms antigen/ml), the ELISA showed a decrease in specific antibody levels as a function of time after treatment starting on day 58, reaching levels close to control (noninfected untreated) in most animals 120 days after treatment. 5. Purified antigens from the adult worm and the schistosomule tegument appear to be promising for use in clinical studies evaluating schistosomiasis after drug treatment.
