Characterization of an Immunodominant Antigenic Epitope from Trypanosoma cruzi as a Biomarker of Chronic Chagas' Disease Pathology

Abstract

Nowadays, the techniques available for chronic Chagas' disease diagnosis are very sensitive; however, they do not allow discrimination of the patient's clinical stages of the disease. The present paper describes that three out of the five different repeats contained in the Trypanosoma cruzi TcCA-2 membrane protein (3972-FGQAAAGDKPPP, 6303-FGQAAAGDKPAP, and 3973-FGQ AAAGDKPSL) are recognized with high sensitivity (>90%) by sera from chronic Chagas' disease patients and that they are not recognized by sera from patients in the acute phase of the disease. A total of 133 serum samples from chagasic patients and 50 serum samples from healthy donors were tested. In addition, sera from 15 patients with different autoimmune diseases, 43 serum samples from patients suffering an infectious disease other than Chagas' disease, and 38 serum samples from patients with nonchagasic cardiac disorders were also included in this study. The residue 3973 peptide shows a specificity of >98%, as it is not recognized by individuals with autoimmune and inflammatory processes or by patients with a nonchagasic cardiomyopathy. Remarkably, the levels of antibody against the 3973 epitope detected by the sera from Chagas' disease patients in the symptomatic chronic phase, involving cardiac or digestive alterations, are higher than those detected by the sera from Chagas' disease patients in the indeterminate phase of the disease. It is suggested that the diagnostic technique described could also be used to indicate the degree of pathology. The amino acids F, Q, and DKP located in the peptide at positions 1, 3, and 8 to 10, respectively, are essential to conform to the immunodominant antigenic epitope.

A Parasite Biomarker Set for Evaluating Benznidazole Treatment Efficacy in Patients with Chronic Asymptomatic Trypanosoma cruzi Infection

“…In a small number of patients, a slight increase in the reactivity against the 4 BMKs was observed at T9 posttreatment (Յ20%) compared with that at baseline (T0). This slight increase may have been due to exposure to the antigenic fragments from nonviable parasites in response to benznidazole, as previously reported (24). When this increase was considered, the percentage of the patients who demonstrated the described seroconversion increased up to 44%, FIG 2 Number and percentage of Chagas disease patients whose reactivity against each of the four molecules met the STEC at 24 and 48 months posttreatment.…”

“…4). Interestingly, the functional pattern of antigen-specific CD8 ϩ T cells before treatment from patients who met the STEC was completely different from that of the Time after treatment (mo) 9 2 out of 33 (6.10) 24 1 out of 33 (3) 48 1 out of 19 (5.30) patients who did not meet the STEC in terms of both the multifunctional capacity and cytokine production pattern of the T cells. Thus, before treatment, those patients who did meet the STEC had a higher proportion of multifunctional antigen-specific CD8 ϩ T cells that expressed granzyme B and perforin than that in patients who did not meet the STEC.…”

“…It was also considered relevant that the drop had to be substantial; the decrease had to be by at least 40% for KMP11, PFR2, and 3973 d and 30% for HSP70. A drop in reactivity of 40% was established as substantial based on the fact that the reactivity of the sera from IND Chagas patients against the 3973 d antigen was 40% lower than that observed in the sera from symptomatic Chagas disease patients (24). In addition, the median reactivity to the 4 BMKs in sera from IND Chagas disease patients at 24 months after treatment was approximately 35% of that detected before treatment.…”

“…During the development of reliable tools to evaluate the therapeutic efficacy of drugs for Chagas disease, several markers have been proposed and, in some cases, have been demonstrated to be effective for assessing the responses to specific treatments (19)(20)(21)(22)(23). Previous laboratory studies showed that the KMP11, PFR2, HSP70, and 3973 T. cruzi antigens are recognized with high specificity and sensitivity in the sera from patients in the chronic stage of the disease (21,24). Likewise, a decrease in the reactivity against these antigens was detected shortly after benznidazole treatment (6 and 9 months) (21,25).…”

Chagas Disease Diagnostic Applications

“…Identification of diagnostic and/or predictive biomarkers of disease progression would therefore represent a major achievement towards improving the clinical management of Chagasic patients. Some authors proposed serological alternatives to tackle this issue, such as quantifying the antibody titers to Ag1/JL7/FRA/H49 to distinguish between Chagas disease-associated cardiac pathology and other non-Chagasic cardiological dysfunctions (Table 1) (Abraham and Derk, 2015; Bhattacharyya et al, 2014; Kaplan et al, 1997; Levin and Hoebeke, 2008; Thomas et al, 2012). On the other hand, antibodies to another 'parental repertoire' antigen, termed JL5, were shown to cross-recognize endogenous β1-adrenergic and M2 muscarinic receptors.…”