title: Peptide-based analysis of the amino acid sequence important to the immunoregulatory function of Trypanosoma cruzi Tc52 virulence factor.
abstract: The intracellular protozoan parasite Trypanosoma cruzi is the aetiological agent of Chagas' disease. We have previously identified a T. cruzi-released protein called Tc52, which is crucial for parasite survival and virulence. In the present study, we attempted to define the Tc52 epitope(s) responsible for its immunoregulatory function. A naturally occurring major peptide fragment of molecular mass 28 kDa (Tc28k) was identified, which was localized in the C-terminal portion of Tc52 and was inhibitory for T-cell activation. Synthetic peptides corresponding to amino acid sequences in Tc52 were evaluated for their ability to modulate T-cell proliferation and cytokine production. Results obtained using five peptides spanning the N-terminal or C-terminal domain of the Tc52 protein indicated that the activity mapped to Tc52 residues 432-445. Moreover, it was found that the peptide, when coupled to a carrier protein (ovalbumin), exhibited increased inhibitory activity on T-lymphocyte activation. Incubation with 8 nm ovalbumin-coupled peptide 432-445 resulted in approximately the same levels (>75%) of inhibition of T-cell proliferation as 5 micro g/ml Tc28k. Furthermore, we showed that the coupled peptide significantly down-regulated the secretion of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2). Likewise, in immunized mice, the coupled peptide 432-445 was a very poor B- and T-cell antigen compared with the other Tc52-derived peptides. These results suggest that the immunomodulatory portion of the T. cruzi Tc52 virulent factor may reside, at least in part, in a conserved sequence within its C-terminal domain, which could minimize its antigenicity.
authors.affiliation: IRD UR 008 Pathogénie des Trypanosomatidae, Centre IRD de Montpellier, France.
authors.forename: Margarida
authors.initials: M
authors.lastname: Borges
authors.forename: Anabela Cordeiro
authors.initials: AC
authors.lastname: Da Silva
authors.forename: Denis
authors.initials: D
authors.lastname: Sereno
authors.forename: Ali
authors.initials: A
authors.lastname: Ouaissi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D015536:Down-Regulation; D007108:Immune Tolerance; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D008198:Lymph Nodes / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D010047:Ovalbumin / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D015800:Protozoan Proteins / Q000737:chemistry / Q000276:immunology*; D013154:Spleen / Q000276:immunology; D014349:Trypanosoma cruzi / Q000276:immunology*; D014774:Virulence / Q000276:immunology
chemical_list: C097550:52-kDa protein, Trypanosoma cruzi; D016207:Cytokines; D007376:Interleukin-2; D010446:Peptide Fragments; D015800:Protozoan Proteins; D007371:Interferon-gamma; D010047:Ovalbumin