Enzyme-Linked Immunoassay Using Recombinant trans -Sialidase of Trypanosoma cruzi Can Be Employed for Monitoring of Patients with Chagas' Disease after Drug Treatment

Abstract

trans-Sialidase is an enzyme present on the surface of Trypanosoma cruzi and is an important antigen recognized by sera from patients with Chagas' disease. In the present study we investigated whether the benznidazole treatment of patients with Chagas' disease induced changes in the reactivity of serum toward a recombinant form of trans-sialidase in order to develop an assay for monitoring of patients after treatment for Chagas' disease, which is needed at Chagas' disease control centers. By using an enzyme-linked immunosorbent assay containing a recombinant protein corresponding to the catalytic domain of trans-sialidase, we found that the antigen had a high specificity for sera from untreated patients with Chagas' disease. Sera from healthy individuals or patients with active visceral leishmaniasis minimally cross-reacted with the antigen. Anti-transsialidase immunoglobulin was detected in 98% of 151 untreated patients with Chagas' disease. Of these, 124 patients were treated for 60 days with benznidazole (5 mg/kg of body weight/day), and their sera were assayed for reactivity with the recombinant trans-sialidase. By using this methodology, three groups of patients could be established. The first group (60 patients), which was considered to have been successfully treated, showed no reactivity after treatment. The second group (46 patients) still showed signs of infection, and after treatment their sera recognized trans-sialidase, but with reduced titers. The third group (18 patients) was considered to be resistant to drug treatment, and their sera presented identical reactivities before and after treatment. These results suggest that determination of the absence of antibodies to recombinant trans-sialidase in treated patients by the present assay is indicative of treatment success, while the presence of antibodies may indicate

Treatment with Benznidazole during the Chronic Phase of Experimental Chagas' Disease Decreases Cardiac Alterations

“…In the present study we also observed that benznidazole treatment decreased the levels of antibodies against TS. This finding is reinforced by a recent study (25) that demonstrated that benznidazole treatment of Chagas' disease patients induces a decrease in the reactivity of serum against recombinant TS that correlates with parasite elimination.…”

Chagas' disease: IgG isotypes against cytoplasmic (CRA) and flagellar (FRA) recombinant repetitive antigens of Trypanosoma cruzi in chronic Chagasic patients

“…The results were expressed in the form of a reactivity index, as described by Pereira-Chioccola et al (18), whereby the values of the means of DOs of the samples were divided by the CO of their respective plates, to enable comparison of the results from different plates.…”

Serological Evaluation of Specific-Antibody Levels in Patients Treated for Chronic Chagas' Disease

“…After the treatment of children younger than 14 years old, four groups (Britto et al [5], da Silveira et al [7], Sosa Estani and Segura [22], and Streiger et al [23]) detected significant titer reductions or regression to negative results for Ͼ50% of the patients, particularly when treatment was given during the acute phase. Other authors (Fabbro de Suasnábar et al [8], Pereira-Chioccola et al [16], and Viotti et al [26]) attempted to treat adults during the unapparent or chronic phase of infection. Although the observation periods, the sites of the trials, and the serological tests used varied among the studies, a trend toward a titer reduction and regression to antibody negativity by serology was also apparent, particularly in studies with long follow-up periods (8,26).…”

“…This means that negative parasitological test results are not a reliable criteria for cure. The only accepted criterion of parasitological cure is the absence of anti-T. cruzi antibodies measured by conventional assays (ELISA, indirect immunofluorescence assay, and IHA) with crude parasite antigens, which are available on the market as kits in every country where the disease is endemic (2,3,5,16,17,18,26). ELISA is the most precise, quantitative, and widely used technique.…”