A monoclonal antibody against the immunodominant epitope of the ribosomal P2β protein of Trypanosoma cruzi interacts with the human β 1‐adrenergic receptor

Monoclonal antibodies were raised against a recombinant ribosomal P2β protein of Trypanosoma cruzi. One of these reacted with the C terminus of this protein (peptide R13, EEEDDDMGFGLFD) and epitope mapping confirmed that this epitope was the same as the one defined by the serum of immunized mice, and similar to the previously described chronic Chagas' heart disease (cChHD) anti‐P epitope. Western blotting showed that the monoclonal antibody recognized the parasite ribosomal P proteins, as well as the human ribosomal P proteins. Electron microscopy showed that it stained different structures in parasite and human cells. Interestingly, surface plasmon resonance measurements indicated that the affinity for the parasite ribosomal P protein epitope (R13) was five times higher than for its human counterpart (peptide H13, EESDDDMGFGLFD). Since the human epitope contained an acidic region (EESDD) similar to the AESDE peptide recognized by cChHD patients in the second extra‐cellular loop of the human β1‐adrenergic receptor, the biological activity of the antibody was assessed on neonatal rat cardiomyocytes in culture. The monoclonal antibody had an agonist‐like effect. These results, together with the fact that the monoclonal reacted in Western blots with the different isoforms of the heart β1‐adrenergic receptor, confirm the possible pathogenic role of antibodies against the parasite ribosomal P protein based on their cross‐reaction with the human β1‐adrenergic receptor.