Detection of circulating schistosome antigens in serum and urine of schistosomiasis patients and assessment of cure by a monoclonal antibody.

From a panel of monoclonal antibodies (MAb), an IgM monoclonal antibody (7F1/6B) reactive with repetitive epitopes on S. mansoni soluble egg antigen was selected. This MAb was employed both as antigen capture and detection antibody in a sandwich ELISA and had a detection limit < 1 ng S. mansoni SEA/mi. Serum and urine samples were collected from rural students who had S. mansoni (169 subjects) or mixed S. mansoni and S. haematobium (64 subjects) infections. Samples were collected before and at 4, 8 and 12 weeks after praziquantel therapy. Circulating schistosome antigens (CSA) were demonstrated in 90% of sera and 97% of urine samples of S. mansoni group and in 91% of sera and 100% of urine samples of mixed infection group. All sera from 29 uninfected individuals, 30 patients with other parasites and 70% of 55 S. haematobium-infected subjects were negative in this assay. CSA level in serum and urine samples correlated positively with the number of S. mansoni eggs/g stool in both groups. A significant reduction in CSA level was observed in serum and urine samples after praziquantel therapy. By 12 weeks post-treatment, negativity was 98% in sera and 97% in urine of S. mansoni-infected group and 98% in sera and 91% in urine of mixed infection group. The data demonstrate that the use of MAb 7F1/6B for the detection of CSA provides a sensitive method for immunodiagnosis of schistosomiasis and monitoring of cure.