Anti-Trypanosoma cruzi and anti-laminin antibodies in chagasic patients after specific treatment

Abstract

The antibody response to Trypanosoma cruzi epimastigote and trypomastigote stages, as well as to laminin, was studied in several groups of chagasic patients. In six patients who were cured of the parasite, the serum antibody titers as revealed by indirect immunofluorescence and hemagglutination tests against epimastigotes (conventional serology) and a complement-mediated lysis test with living trypomastigotes did not differ from those of normal individuals. In seven presumably cured patients, although the complement-mediated lysis test turned negative, conventional serology remained positive. Sera from this group of so-called "dissociated" patients presented significant lower mean antibody titers against epimastigote but not trypomastigote stages than did sera from 14 untreated patients (P less than 0.01). Most of the antibodies against trypomastigotes, including the residual levels found in cured patients, were absorbed by mouse laminin. In fact, significantly higher titers of anti-laminin antibodies were observed in sera from untreated chagasic patients (1.131 +/- 0.458) and cured patients (1.103 +/- 0.572) than in sera from eight normal individuals (0.459 +/- 0.402) (P less than 0.01). The anti-laminin titers were higher in sera of patients of blood group A or O than in those of patients of group B or AB. In Western blotting (immunoblotting) analysis against trypomastigotes, sera from chronic untreated patients recognized many polypeptide bands ranging from 26 to 160 kilodaltons, whereas no protein bands were observed with sera from cured patients. Only faint bands of parasite proteins were observed with sera of dissociated patients. In conjunction, the above data suggest that the anti-trypomastigote antibodies which persist after parasitological cure of patients with Chagas' disease are due mainly to cross-reactive epitopes from mouse laminin.