A sugar‐coated strategy to treat a rare neurologic disease provides a blueprint for a decoy glycan therapeutic and a potential vaccine for CoViD‐19

Abstract In a rare neurologic disease known as IgM monoclonal gammopathy the immune system targets a sulfated trisaccharide known as the Human Natural Killer‐1 (HNK‐1) epitope that comprises a constituent of the myelin sheath known as MAG (myelin‐associated glycoprotein). This Editorial highlights a study by Aliu and colleagues in the current issue of the Journal of Neurochemistry, in which the investigators constructed a biodegradable poly‐l‐lysine backbone with multiple copies of this sulfated HNK‐1 trisaccharide. This decoy, poly(phenyl disodium 3‐ O ‐sulfo‐β‐ d ‐glucopyranuronate)‐(1→3)‐β‐ d ‐galactopyranoside, known as PPSGG, removed anti‐MAG IgM autoantibodies from the blood, while not activating the immune system. These findings provide a path for the selective removal of a pathogenic set of antibodies that target the myelin sheath resulting in neuropathy. These findings are applicable to a parallel strategy for the generation of polysaccharides similar to those present in the receptor‐binding domain of CoViD‐19, which might inhibit viral adhesion to its receptor, the angiotensin‐converting enzyme‐2 (ACE2) protein, thereby impairing cellular uptake of the virus itself. The deployment of complex polysaccharides that mimic actual COVID19 polysaccharides on the spike protein may also provide a feasible structural basis for a vaccine. Carbohydrate mimics, if conjugated to a carrier or backbone, might provoke an immune response to the spike protein. A vaccine that targets critical carbohydrates on COVID19, and then neutralizes the virus would recapitulate a successful strategy employed in other microbial vaccines, like the pneumococcal vaccines and the meningococcal vaccines. These vaccines direct an immune response to complex carbohydrates and successfully prevent life‐threatening disease. This paper provides lessons from a rare neurologic disease that may teach us strategies applicable to a global pandemic.