Evaluation of a competitive antibody enzyme immunoassay for specific diagnosis of Chagas' disease

A competitive enzyme immunoassay based on the use of a monoclonal antibody (MAb) specific for "component 5" of Trypanosoma cruzi was evaluated. The antigenicity and immunogenicity of this component has been observed in natural and experimental infections. The studies were conducted in an area of Bolivia where mixed infections with Leishmania braziliensis are frequent and present a problem in the accurate diagnosis of T. cruzi infections. The specificity and sensitivity of this assay as compared to the indirect immunofluorescence and ELISA tests were demonstrated. The present test has proved to be more specific than the immunofluorescence and ELISA tests. The acute phase of Chagas' disease is often accompanied by patent parasitemia. In the indeterminate and chronic phases, parasites are rarely detectable in the blood, and diagnosis relies principally on serological tests. However, similarities in the antigenic make-up of Trypanosomatidae (Afchain et al., 1979) and mixed infections, mainly with species of Leishmania or Trypanosoma rangeli in many areas of Central and South America complicate the diagnosis of Chagas' disease. Afchain et al. (1979) identified a component termed "5," specific for Trypanosoma cruzi, that can induce precipitating antibodies and is usually detected in the sera of chronic chagasic patients (Afchain et al., 1970; Breniere et al., 1985). Furthermore, monoclonal antibodies (MAb) specific for component 5 (Orozco et al., 1982, 1984) recognize a 72-kd glycoprotein and have helped identify its maturation products (51, 43, and 24 kd). These MAb have made it possible to develop a specific test for Chagas' disease, based on a competitive (antibody) enzyme immunoassay (CEIA) (Lemesre et al., 1986) using a 24-kd-enriched fraction as antigen. In this work the CEIA test was studied with regard to its ability to discriminate Leishmania braziliensis and its sensitivity compared to the IFT and ELISA tests. The L. braziliensis to which we refer represents one of the species of the L. braziliensis complex of species. Received 5 May 1988; revised 17 November 1988; accepted 20 January 1989. t Facultad de Ciencias y Tecnologia, Departamento de Biologia, Universidad Mayor de San Simon, Cochabamba, Bolivia. t Centre d'Immunologie et de Biologie Parasitaire, Institut Pasteur, 1 Rue du Professor A. Calmette, 59019, Lille Cedex, France. MATERIALS AND METHODS