Designed Glucopeptides Mimetics of Myelin Protein Epitopes As Synthetic Probes for the Detection of Autoantibodies, Biomarkers of Multiple Sclerosis

We previously reported that the synthetic glucopeptide CSF114(Glc) detects diagnostically relevant autoantibodies in multiple sclerosis patients’ sera. As the native antigens recognized by anti-CSF114(Glc) autoantibodies are still elusive, we performed a sequence alignment analysis of myelin proteins and CSF114(Glc), which led to the identification of five relevant sequences. The corresponding glucopeptides were synthesized and tested in competitive enzyme-linked immunosorbent assay, showing that they share with the parent peptide a common minimal epitope,. Starting from these results, we designed an optimized sequence, termed SP077, showing a higher degree of homology with both CSF114(Glc) and the five fragments of central nervous system protein selected using the bioinformatic approach. SP077 was synthesized and tested in solid-phase enzyme-linked immunosorbent assay for its ability to detect diagnostically relevant autoantibodies in 50 representative multiple sclerosis patients sera, demonstrating that the newly designed antigenic probe is able to detect higher antibody titers, as compared to CSF114(Glc). Finally, the conformational properties of SP077 were studied by NMR spectroscopy and structure calculations, showing that it differs from CSF114(Glc) for the exposure of the sugar moiety and for the surface properties of the C-terminal portion. Thus, the slightly superior immunological activity of SP077 in the recognition of specific autoantibodies in multiple sclerosis patients sera may be ascribed to both the optimized design of its epitopic region, represented by the glucosylated Asn and the neighboring residues, and the superior surface interacting properties of its C-terminal region.