Epitope Mapping oftrans-Sialidase fromTrypanosoma cruziReveals the Presence of Several Cross-Reactive Determinants

Abstract

Trypanosoma cruzi, the agent of Chagas' disease, expresses trans-sialidase, a unique enzyme activity that enables the parasite to invade host cells by transferring sialyl residues from host glyconjugates to the parasite's surface acceptor molecules. The enzyme is also shed into the surrounding environment, causing apoptosis in cells from the immune system. During infections, an antibody response against the catalytic region of the trans-sialidase that is coincident with the control of the parasitemia and survival of the host is observed. This low-titer humoral response is characterized by its persistence for many years in benznidazole-treated patients. Here we analyzed the antigenic structure of the molecule by phage-displayed peptide combinatorial libraries and SPOT synthesis. Several epitopes were defined and located on the three-dimensional model of the enzyme. Unexpectedly, cross-reaction was found among several epitopes distributed in different locations displaying nonconsensus sequences. This finding was confirmed by the reactivity of three monoclonal antibodies able to recognize non-sequence-related peptides that together constitute the surface surrounding the catalytic site of the enzyme. The presence of cross-reacting epitopes within a single molecule suggests a mechanism developed to avoid a strong humoral response by displaying an undefined target to the immune system.

Multiple Overlapping Epitopes in the Repetitive Unit of the Shed Acute-Phase Antigen from Trypanosoma cruzi Enhance Its Immunogenic Properties

“…In one of them, peptides are flanked by cysteine residues, allowing the location of the epitopes in a solvent-exposed loop on phage pVIII protein (12). For these screenings, both the MAb anti-SAPA (10) and purified immunoglobulin G from GST-SAPA-immunized rabbits were used as described previously (16). Screening of the libraries with the MAb anti-SAPA yielded five positive phages (group I) with the consensus sequence SAH(A/V)XP(S/T), where X denotes a permissive position ( Fig.…”

Determination of the Compatibility Between Biomphalaria Alexandrina and Echinostoma Liei Using SDS-Page Analysis of Tissue Soluble Proteins

“…Epitope mapping of trans-sialidase from T. cruzi revealed the presence of several cross-reactive determinants (Pitcovsky et a/., 2001).…”

Theranostic applications of phage display to control leishmaniasis: selection of biomarkers for serodiagnostics, vaccination, and immunotherapy

“…Thus, it has been successfully applied to identify mimotopes used to diagnose malaria (22) (23) , toxoplasmosis (24) (25) , hepatitis A (26) , neurocysticercosis (27) , strongyloidiasis (28) , thyroid cancer (29) , Chagas' disease (30) , and bovine anaplasmosis (31) , and to develop vaccine candidates against cysticercosis (32) , herpes simplex virus infection (33) , cancer (34) , taeniasis (35) , hepatitis B (36) , trichinellosis (37) , Alzheimer's disease (38) , and bovine anaplasmosis (39) . Phage display technology has been also instrumental in the selection of therapeutic agents to treat various cancers such as glioblastoma, melanoma, leukemia, and prostate and thyroid cancers (40) (41) .…”