Epitopes common to Trypanosoma cruzi and mammalian tissues are recognized by sera from Chagas' disease patients: prognosis value in Chagas disease

Abstract

Monoclonal antibodies (MoAbs) raised against Trypanosoma cruzi microsomal fraction (Mc) and cross-reactive with mammalian tissues were used to evaluate the ability of cross-reactive T. cruzi antigens to induce an immune response in Chagas' disease. Thus, we studied the ability of sera from Chagas' disease patients (CDP) with different degrees of cardiac dysfunction to block the immune recognition of these MoAb to the target antigen determining for each serum an inhibition index (II). By means of this approach we inferred that blocking of monoclonal antibody binding to T. cruzi microsomes by subjects' serum represents antibodies After serological and medical examinations, individuals were separated into the following groups: Chagas' disease patients without manifest cardiac involvement (CDP-0), CDP with suspected or borderline cardiac disease (CDP-1), CDP with moderate myocardial dysfunction (CDP-2), CDP with overt cardiac dysfunction (CDP-3) and controls including healthy subjects (HS) and patients with idiopathic myocarditis (IMP). The reactivity between MoAb 5F2 and its target antigen was significantly ( p < 0.05) inhibited by sera from CDP irrespective of the clinical stage [CDP: n = 46, 50± 20, mean II ± SD; control: n = 16, 18 ± 8]. Moreover, 5F2 was able to distinguish ( p < 0.05) sera from CDP with mild disease (CDP clinical grade 0 1 : n = 20, 34 ± 18 ) from that of CDP with severe disease (CDP clinical grade 2 3 : n = 20, 67 ± 7 ). Moreover, the inhibitory capacity of sera from asymptomatic CDP (CDP-0) correlated with patients age ( r = 0.66, p < 0.05). CDP-0 below or equal 40 years of age had results ( n = 15, 25 ± 13) comparable ( p > 0.05) to that of controls while mean inhibition of CDP-0 over 40 years of age ( n = 5, 60 ± 5) was indistinguishable ( p > 0.05) from that of patients with severe disease. Competitive assay with MoAb 5A9B11 also showed significant differences ( p < 0.05) between sera from CDP ( n = 46, 46 ± 24) and controls ( n = 13, 5 ± 5). On the contrary, the differences observed between CDP with different cardiac involvement was not significant (mild: n = 26, 31 ± 22; severe: n = 20, 66 ± 11). However a thorough study of data from asymptomatic group sera revealed the existence of two levels of reactivity, with low and high capacity to inhibit the reaction of 5A9B11 against Mc. On the contrary, CDP sera showed a blocking activity for 1A10C11 comparable to that of controls (CDP: n = 25, 19 ± 9; control: n = 12, 14 ± 6). Some cross-reactive MoAbs recognized epitopes partially composed of carbohydrates. Interestingly, 5F2 and 5A9B11 epitopes did not appear to have carbohydrates moieties. In summary, immunoinhibition assays revealed differences in the immune response of chronic chagasic patients against parasite epitopes. These results have opened the possibility to identify a prognosis marker of the disease suggesting the clinical utility of monitoring levels of these anti-Mc antibodies in patients with chronic Chagas' disease.