Structure-Activity Relationship Studies, SPR Affinity Characterization and Conformational Analysisof Peptides Mimicking the HNK-1 Carbohydrate Epitope

The design of molecules mimicking biologically relevant glycans is a significant goal for understanding important biological processesand may lead to new therapeutic and diagnostic agents. We focused our attention on the trisaccharide human natural killer cell-1 (HNK-1), considered the antigenic determinant ofmyelin-associated glycoprotein and the target of clinically relevant auto-antibodies in autoimmune neurological disorders such as IgM monoclonal gammopathy and demyelinating polyneuropathy.We describe a structure-activity relationship study based on surface plasmon resonance binding affinities aiming at the optimization of a peptide mimicking the HNK-1 minimal epitope. We developed a cyclic heptapeptide showing an affinity of 1.09*10-7 Mfor a commercial anti-HNK1 mouse monoclonal antibody. A detailed conformational analysis gave possible explanations of the good affinity displayed by this novel analogue, which was subsequently used as immunological probe. However, a preliminary screening indicates that patients sera do not specifically recognize this peptide, showing that murine monoclonal antibodies cannot be used as a guide to select immunological probes for the detection of clinically relevant human auto-antibodies.