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Structure‐Guided Design of a Group B Streptococcus Type III Synthetic Glycan–Conjugate Vaccine
Author(s) -
Oldrini Davide,
Bino Linda,
Arda Ana,
Carboni Filippo,
Henriques Pedro,
Angiolini Francesca,
Quintana Jon I.,
Calloni Ilaria,
Romano Maria R.,
Berti Francesco,
JimenezBarbero Jesus,
Margarit Immaculada,
Adamo Roberto
Publication year - 2020
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.202000284
Subject(s) - epitope , glycoconjugate , glycan , chemistry , conjugate , glycosylation , rational design , immunogenicity , stereochemistry , antigen , biochemistry , biology , glycoprotein , mathematical analysis , genetics , mathematics
Identification of glycan functional epitopes is of paramount importance for rational design of glycoconjugate vaccines. We recently mapped the structural epitope of the capsular polysaccharide from type III Group B Streptococcus (GBSIII), a major cause of invasive disease in newborns, by using a dimer fragment (composed of two pentasaccharide repeating units) obtained by depolymerization complexed with a protective mAb. Although reported data had suggested a highly complex epitope contained in a helical structure composed of more than four repeating units, we showed that such dimer conjugated to a carrier protein with a proper glycosylation degree elicited functional antibodies comparably to the full‐length conjugated polysaccharide. Here, starting from the X‐ray crystallographic structure of the polysaccharide fragment–mAb complex, we synthesized a hexasaccharide comprising exclusively the relevant positions involved in binding. Combining competitive surface plasmon resonance and saturation transfer difference NMR spectroscopy as well as in‐silico modeling, we demonstrated that this synthetic glycan was recognized by the mAb similarly to the dimer. The hexasaccharide conjugated to CRM 197 , a mutant of diphtheria toxin, elicited a robust functional immune response that was not inferior to the polysaccharide conjugate, indicating that it may suffice as a vaccine antigen. This is the first evidence of an X‐ray crystallography‐guided design of a synthetic carbohydrate‐based conjugate vaccine.