Synthesis of Asparagine Derivatives Harboring a Lewis X Type DC-SIGN Ligand and Evaluation of their Impact on Immunomodulation in Multiple Sclerosis

The protein myelin oligodendrocyte glycoprotein (MOG) is a key component of myelin and an autoantigen in the disease multiple sclerosis (MS). Post-translational N-glycosylation of Asn₃₁ of MOG seems to play a key role in modulating the immune response towards myelin. This is mediated by the interaction of Lewis-type glycan structures in the N-glycan of MOG with the DC-SIGN receptor on dendritic cells (DCs). Here, we report the synthesis of an unnatural Lewis X (Le^X)-containing Fmoc-SPPS-compatible asparagine building block (SPPS=solid-phase peptide synthesis), as well as asparagine building blocks containing two Le^X-derived oligosaccharides: LacNAc and Fucα1-3GlcNAc. These building blocks were used for the glycosylation of the immunodominant portion of MOG (MOG_31-55) and analyzed with respect to their ability to bind to DC-SIGN in different biological setups, as well as their ability to inhibit the citrullination-induced aggregation of MOG_31-55. Finally, a cytokine secretion assay was carried out on human monocyte-derived DCs, which showed the ability of the neoglycopeptide decorated with a single Le^X to alter the balance of pro- and anti-inflammatory cytokines, inducing a tolerogenic response.