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Detailed Investigation of the Immunodominant Role of O‐Antigen Stoichiometric O‐Acetylation as Revealed by Chemical Synthesis, Immunochemistry, Solution Conformation and STD‐NMR Spectroscopy for Shigella flexneri 3a
Author(s) -
Boutet Julien,
Blasco Pilar,
Guerreiro Catherine,
Thouron Françoise,
Dartevelle Sylvie,
Nato Farida,
Cañada F. Javier,
Ardá Ana,
Phalipon Armelle,
JiménezBarbero Jesús,
Mulard Laurence A.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201600567
Subject(s) - shigella flexneri , epitope , chemistry , monoclonal antibody , nuclear magnetic resonance spectroscopy , stereochemistry , immunochemistry , two dimensional nuclear magnetic resonance spectroscopy , antigen , microbiology and biotechnology , glycoside , acetylation , antibody , biochemistry , escherichia coli , biology , genetics , immunology , gene
Abstract Shigella flexneri 3a causes bacillary dysentery. Its O‐antigen has the {2)‐[α‐ d ‐Glc p ‐(1→3)]‐α‐ l ‐Rha p ‐(1→2)‐α‐ l ‐Rha p ‐(1→3)‐[Ac→2]‐α‐ l ‐Rha p ‐(1→3)‐[Ac→6] ≈40 % ‐β‐ d ‐Glc p NAc‐(1→} ([(E)AB Ac C Ac D]) repeating unit, and the non‐ O ‐acetylated equivalent defines S. flexneri X. Propyl hepta‐, octa‐, and decasaccharides sharing the (E′)A′B Ac CD(E)A sequence, and their non‐ O ‐acetylated analogues were synthesized from a fully protected B Ac CD(E)A allyl glycoside. The stepwise introduction of orthogonally protected mono‐ and disaccharide imidate donors was followed by a two‐step deprotection process. Monoclonal antibody binding to twenty‐six S. flexneri types 3a and X di‐ to decasaccharides was studied by an inhibition enzyme‐linked immunosorbent assay (ELISA) and STD‐NMR spectroscopy. Epitope mapping revealed that the 2 C ‐acetate dominated the recognition by monoclonal IgG and IgM antibodies and that the B Ac CD segment was essential for binding. The glucosyl side chain contributed to a lesser extent, albeit increasingly with the chain length. Moreover, tr‐NOESY analysis also showed interaction but did not reveal any meaningful conformational change upon antibody binding.