Targeting synthetic glycopeptides to MGL on Dermal Dendritic cells

Abstract

The ability of a peptide vaccine to stimulate T cells in vivo might be improved by specifically targeting the peptide to dendritic cells (DC). The C-type lectin Macrophage Galactose-type lectin, MGL (CD301), has been shown to bind to N-acetyl-galactosamine (GalNAc) and small peptides bearing O-linked GalNAc. Synthetic GalNAc can be produced using relatively simple organic chemistry when compared with the complicated branched sugars that are recognised by other C-type lectins. MGL therefore represents a promising target for the design of synthetic peptide vaccines. We have identified that antigen-presenting cells in human skin express MGL and have confirmed that CD14+ dermal DCs might be targeted via MGL. The intracellular fate of MGL following internalisation was tracked by confocal microscopy. MGL traffics through early endosomes to late endosomes/lysosomes, and colocalises with MHC class I and class II. Synthetic glycopeptides were produced incorporating either native O-linked GalNAc or GalNAc residues linked to the peptide chain via non-native “Click” chemistry. Biophysical analysis of the ability of both “Click” and native glycopeptides peptides with recombinant MGL confirmed the ability of both these peptides to bind MGL. Ongoing work aims to determine whether targeting to MGL using these synthetic peptides results in efficient presentation of antigen to T cells.