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

Abstract

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.

Effects of autoantibodies against β1-adrenoceptor in hepatitis virus myocarditis on action potential and L-type Ca2+currents

“…Whereas exposure of cells to anti-β 1 -receptor autoantibodies diluted at 1:80 in the presence of 1 µmol/L metoprolol resulted in a slight prolongation of the APD. As in Table 2 shown, the increase averaged only 7.2%, 5.3% and 4.1% for APD 20 , APD 50 and APD 90 vs control (P<0.01 vs anti-β 1 -receptor autoantibodies diluted at 1:80). Effects of anti-β 1 -receptor autoantibodies on I Ca-L channels in the absence and presence of metoprolol As described above, anti-β 1 -receptor autoantibodies markedly prolonged the plateau, suggesting the antibodies might enhance I Ca-L .…”

“…The action potential duration (APD) was assessed as a duration to 20%, 50% and 90% repolarization (APD 20 , APD 50 and APD 90 , respectively). Anti-β 1 -receptor autoantibodies diluted at 1:80 prolonged the APD in all phases of repolarization, and the increase averaged 39.2%, 29.1% and 15.2% for APD 20 , APD 50 and APD 90 vs control. Thus the plateau was markedly prolonged (Figure 2 and Table 1).…”

“…It was recently found that some cases of severe fulminant hepatitis virus myocarditis were accompanied by arrhythmias and/or cardiac injury. These cases were screened with a high prevalence of circulating autoantibodies against β 1 -adrenoceptor (anti-β 1 -receptor autoantibodies) [18] , which have been recognized in idiopathic dilated cardiomyopathy (DCM) and Chagas' cardiomyopathy [19,20] . Using the patch clamp technique, we examined the effects of anti-β 1 -receptor autoantibodies from patients with HVM on the electrophysiological properties of cardiomyocytes so as to find the possible clinical significance of the autoantibodies.…”

Ribosomes from Trypanosomatids: Unique Structural and Functional Properties

“…This specificity is due to only one amino acid change (Ser by Glu) [27][28][29][30]. In a previous work, we have obtained a recombinant single chain antibody (scFvC5), derived from a monoclonal antibody against the C-terminal region of T. cruzi P2 protein [31,32]. This recombinant antibody, similarly to human antibodies from chagasic patients, shows very high selectivity toward the parasite epitope.…”

Protein–protein interaction map of the Trypanosoma cruzi ribosomal P protein complex

“…Purified ribosomes were prepared as described (Gó mez et al, 2001). For immunoblotting, membranes were first incubated with mouse monoclonal antibodies 17.2 or 68.2 (Mahler et al, 2001) or monoclonal antibody against the BD domain of GAL4 (BD Biosciences Clontech, San Diego, CA, USA), followed by detection with anti-mouse IgG conjugated to peroxidase (Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA).…”