Issue 8, 2015

Convergent chemo-enzymatic synthesis of mannosylated glycopeptides; targeting of putative vaccine candidates to antigen presenting cells

Abstract

The combination of solid phase peptide synthesis and endo-β-N-acetylglucosaminidase (ENGase) catalysed glycosylation is a powerful convergent synthetic method allowing access to glycopeptides bearing full-length N-glycan structures. Mannose-terminated N-glycan oligosaccharides, produced by either total or semi-synthesis, were converted into oxazoline donor substrates. A peptide from the human cytomegalovirus (CMV) tegument protein pp65 that incorporates a well-characterised T cell epitope, containing N-acetylglucosamine at specific Asn residues, was accessed by solid phase peptide synthesis, and used as an acceptor substrate. High-yielding enzymatic glycosylation afforded glycopeptides bearing defined homogeneous high-mannose N-glycan structures. These high-mannose containing glycopeptides were tested for enhanced targeting to human antigen presenting cells (APCs), putatively mediated via the mannose receptor, and for processing by the APCs for presentation to human CD8+ T cells specific for a 9-mer epitope within the peptide. Binding assays showed increased binding of glycopeptides to APCs compared to the non-glycosylated control. Glycopeptides bearing high-mannose N-glycan structures at a single site outside the T cell epitope were processed and presented by the APCs to allow activation of a T cell clone. However, the addition of a second glycan within the T cell epitope resulted in ablation of T cell activation. We conclude that chemo-enzymatic synthesis of mannosylated glycopeptides enhances uptake by human APCs while preserving the immunogenicity of peptide epitopes within the glycopeptides, provided those epitopes are not themselves glycosylated.

Graphical abstract: Convergent chemo-enzymatic synthesis of mannosylated glycopeptides; targeting of putative vaccine candidates to antigen presenting cells

Supplementary files

Article information

Article type
Edge Article
Submitted
17 3 2015
Accepted
11 5 2015
First published
19 5 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2015,6, 4636-4642

Author version available

Convergent chemo-enzymatic synthesis of mannosylated glycopeptides; targeting of putative vaccine candidates to antigen presenting cells

J. D. McIntosh, M. A. Brimble, A. E. S. Brooks, P. R. Dunbar, R. Kowalczyk, Y. Tomabechi and A. J. Fairbanks, Chem. Sci., 2015, 6, 4636 DOI: 10.1039/C5SC00952A

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