Synthesis of antifungal vaccines by conjugation of β-1,2 trimannosides with T-cell peptides and covalent anchoring of neoglycopeptide to tetanus toxoid

• Published in: Carbohydrate research 2015-02, Vol.403, p.123-134
• Main Authors: Cartmell, Jonathan, Paszkiewicz, Eugenia, Dziadek, Sebastian, Tam, Pui-Hang, Luu, Thanh, Sarkar, Susmita, Lipinski, Tomasz, Bundle, David R.
• Format: Article
• Language: English
• Subjects: Acylation; Candida albicans - immunology; Chemistry Techniques, Synthetic; Epitopes, T-Lymphocyte - immunology; Fungal Vaccines - chemical synthesis; Fungal Vaccines - chemistry; Glycoconjugate vaccine; Glycopeptide tetanus toxoid conjugate; Glycopeptides - chemistry; Mannosides - chemistry; Sulfhydryl Compounds - chemistry; Synthesis of glycopeptide; Tetanus Toxoid - chemical synthesis; Tetanus Toxoid - chemistry; Thiol thioester exchange; Trisaccharides - chemistry; Vaccines, Conjugate - chemistry
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2014.06.024

•Three component trisaccharide–peptide and carrier protein vaccines have been synthesized.•Conjugation employed peptides bearing N-terminal thiols and acetylated C-terminal thiols.•Thiol–thioester exchanged results in a mixture of glycopeptides bearing saccharides linked to N-terminal and C-terminal amino acids.•Installation of an N-terminal thiol with a lower pKa ensured a single glycopeptide with an oligosaccharide installed at the N-terminus of the peptide.•Replacement of the C-terminal thiol with an azido amino acid allowed ‘click’ chemistry to be used for attaching the glycopeptide to a protein carrier. Selective strategies for the construction of novel three component glycoconjugate vaccines presenting Candida albicans cell wall glycan (β-1,2 mannoside) and polypeptide fragments on a tetanus toxoid carrier are described. The first of two conjugation strategies employed peptides bearing an N-terminal thiopropionyl residue for conjugation to a trisaccharide equipped with an acrylate linker and a C-terminal S-acetyl thioglycolyl moiety for subsequent linking of neoglycopeptide to bromoacetylated tetanus toxoid. Michael addition of acrylate trisaccharides to peptide thiol under mildly basic conditions gave a mixture of N- and C- terminal glyco-peptide thioethers. An adaptation of this strategy coordinated S-acyl protection with anticipated thioester exchange equilibria. This furnished a single chemically defined fully synthetic neoglycopeptide conjugate that could be anchored to a tetanus toxoid carrier and avoids the introduction of exogenous antigenic groups. The second strategy retained the N-terminal thiopropionyl residue but replaced the C-terminal S-acetate functionality with an azido group that allowed efficient, selective formation of neoglycopeptide thioethers and subsequent conjugation of these with propargylated tetanus toxoid, but introduced potentially antigenic triazole linkages.