Modulatory effects on myocardial physiology induced by an anti-Trypanosoma cruzi monoclonal antibody involve recognition of major antigenic epitopes from beta(1)-adrenergic and M(2)-muscarinic cholinergic receptors without requiring receptor cross-linking

CREMASCHI GA; FERNÁNDEZ MM; GORELIK G; GOIN JC; FOSSATI CA; ZWIRNER NW; MALCHIODI EL

JOURNAL OF NEUROIMMUNOLOGY

Elsevier/North-Holland,

Lugar: Netherlands; Año: 2004 vol. 153 p. 99 - 107

0165-5728

ABSTRACT    Involvement of anti-myocardial Abs against neurotransmitter (NT) receptors in the immunopathology of chronic Chagas’ heart disease has been proposed. Previously we demonstrated that an anti-T. cruzi monoclonal Ab (MAb), named CAK20.12, binds to murine cardiac b-adrenergic and mACh receptors eliciting abnormal physiological responses on normal heart.  To identify the putative NT receptor epitopes responsible of these effects, MAb interaction with synthetic peptides from the second extracellular loop of both ß1-adrenergic and mACh receptor-derived peptides was demonstrated by ELISA assays. Cross reactivity between NT receptor peptides and T. cruzi Ag was confirmed by inhibition of MAb CAK20.12 binding to NT receptor peptides by preincubation with parasite-derived F105 fraction. In addition cross-interference between one NT receptor-derived peptide and MAb binding to the other NT receptor-derived peptide was also demonstrated. Cross-linking of membrane receptors requirement in modulating cardiac physiology was also analyzed with Fab CAK20.12 fragment.  Non-competitive inhibition of specific radioligand binding to both NT receptors on cardiac membranes was achieved with the Fab fragment. Furthermore, both MAb and Fab CAK20.12 induced a raise in intracellular cyclic nucleotides coupled to both b1-adrenergic and M2-mACh receptors, namely cAMP and cGMP, respectively, and a positive inotropic effect on cardiac contractility. MAb an Fab actions on both cAMP and the isometric tension increment were abrogated by he b1 peptide, while the M2 peptide inhibited cGMP induction and potentiated b-adrenergic stimulation on cardiac contractility.  These results strongly support the existence of cross-reactivity due to molecular mimicry between the parasite antigen recognized by MAb CAK20.12 and the major antigenic epitopes present on both b1-adrenergic and M2-ACh receptors. Its possible relationship with cardiac dysfunction during chronic stage of Chagas´ disease is also discussed.