Schistosoma circulating antigens were used for the detection of active infection. Anti-S. mansoni IgG2a monoclonal antibody (MAb) designated C5C4 was generated. The target epitope of this MAb was detected in adult worms, eggs, and cercariae antigenic extracts of S. mansoni and S. haematobium, had a molecular size of 63 kD, and was not detected in Fasciola hepatica and Ascaris. In addition, a 50-kD degradation product was identified only in the urine of infected individuals. Analysis by high-performance liquid chromatography of the purified antigen demonstrated only one peak. The 63-kD antigen was characterized as a protein containing 40.4% hydrophobic, 7.5% acidic, and 8.8% basic amino acids. The C5C4 MAb was used in a Fast Dot-ELISA for rapid and simple diagnosis of human schistosomiasis. The 63-kD circulating antigen was detected in 92% of urine samples from 330 S. mansoni-infected individuals, with 16% false-positive results among 130 noninfected individuals.

The identification and characterization of schistosome antigens in different developmental stages and the assessment of their role in host-parasite interactions are needed as a step toward the diagnosis of human schistosomiasis. 1 Several investigators have isolated and characterized many of the schistosomiasis antigens in different developmental stages of the parasite that have a potential application in immunodiagnosis. 2–4 In the present study, we have identified and characterized a schistosome antigen using a specific anti–Schistosoma mansoni mouse monoclonal antibody (MAb) and evaluated the suitability of this MAb in the immunodiagnosis of S. mansoni infection.