An anionic synthetic sugar containing 6-SO(3) -NAcGlc mimics the sulfated cruzipain epitope that plays a central role in immune recognition.

ALICIA S COUTO,; L. L. SOPRANO,; LANDONI M; MARILYNE POURCELOT; ACOSTA D.M,; BULTEL L; PARENTE J; FERRARO MR; BARBIER M, ; DUSSOUY C; ESTEVA MI; KOVENSKY J,; DUSCHAK VG

FEBS JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Oxford; Año: 2012 vol. 279 p. 3665 - 3679

1742-464X

Cruzipain (Cz), the major cysteine proteinase ofTrypanosoma cruzi,isa glycoprotein that contains sulfated high-mannose-type oligosaccharides. We have previously determined that these sulfate groups are targets of spe-cific immune responses. In order to evaluate the structural requirements for antibody recognition of Cz, a systematic structure–activity study of the chemical characteristics needed for antibody binding to the Cz sulfated epi-tope was performed by immunoassays. With this aim, different synthesized molecules were coupled to the proteins BSA and aprotinin and confronted with (a) mouse sera specific for Cz and its carboxy-terminal (C-T) domain, (b) antibodies raised in rabbits immunized with Cz and its C-terminal domain and (c) IgGs purified from human Chagas disease sera. Our results indicate that a glucosamine containing an esterifying sulfate group in posi-tion O-6 and an N-acetyl group was the preferred epitope for the immune recognition of sera specific for Cz and its C-T domain. Although to a minor extent, other anionic compounds bearing sulfate groups in different positions and number as well as different anionic charged groups including carboxylated or phosphorylated monosaccharides, disaccharides and oligo-saccharides were recognized. In conclusion, we found that synthetic anionic sugar conjugates containing N-acetyl D-glucosamine-6-sulfate sodium salt (GlcNAc6S) competitively inhibit the binding of affinity purified rabbit anti-C-T IgG to the C-T extension of Cz. Extending these findings to the context of natural infection, immune assays performed with Chagas disease serum confirmed that the structure of synthetic GlcNAc6S mimics the N-glycan-linked sulfated epitope displayed in the C-T domain of Cz.