INVESTIGADORES
LONGHI Silvia Andrea
congresos y reuniones científicas
Título:
Recombinant antibodies against Trypanosoma cruzi modulate cardiac rhythm and retina
Autor/es:
SMULSKI CR; LABOVSKY V; LONGHI SA; SIMONETTI L; LEVIN MJ
Lugar:
Rio de Janeiro, Brasil
Reunión:
Congreso; 13th International Congress of Immunology; 2007
Institución organizadora:
IUIS, ALAI, SBI
Resumen:
Human antibodies from patients with Chagas heart disease and monoclonal antibodies (mAb)
against the carboxy-terminal end (B cell epitope R13) of the ribosomal P2ß protein of
Trypanosoma cruzi (TcP2ß) have been found to cross-react and stimulate the ß1 adrenergic
receptor (ß1-AR). To study the structural basis of this cross-reactivity the variable regions of the
anti-R13 mAb 17.2 were cloned, sequenced and used to express two different single-chain Fv
fragments (scFv) in E. coli (C5 (VH-VL short linker) and B7 (VH-VL long linker)). Both were
characterized for their physicochemical and immunochemical properties. The scFv C5 was a
dimer and bound to TcP2ß with an affinity of Kd=8 nM, whereas scFv B7 was monomeric and
had less affinity than scFv C5 for TcP2ß, Kd=46 nM. Interestingly, while scFv C5 induced an
increase in cAMP levels in CHO-K cells transfected with the human ß1-AR, scFv B7 had no
intrinsic effect on these cells, but blocked isoproterenol induced stimulation. The agonist-like
activity of scFv C5 and the antagonist activity of scFv B7 were both confirmed in vitro on
neonatal rat cardiomyocytes, and in vivo on heart beating frequency after their passive transfer
to mice. Bio-distribution experiments confirmed high scFv C5 concentration in heart
concomitantly with tachycardia and revealed binding to eyes, including functional effect on
retina. This may be explained by the presence of ß1-AR in the retinal pigmented epithelium.
These results suggest a relevant role of antibodies against the carboxy-terminal end of T. cruzi
ribosomal proteins in the pathogenesis of Chagas disease.