Specific adsorbents for myasthenia gravis autoantibodies using mutants of the muscle nicotinic acetylcholine receptor extracellular domains

Myasthenia gravis (MG) is usually caused by antibodies against the muscle acetylcholine receptor (AChR). Plasmapheresis and immunoadsorption are often used to treat non-responsive patients. Antigen-specific immunoadsorption would remove only the pathogenic autoantibodies reducing side-effects. We expressed AChR extracellular domain mutants for use as specific adsorbents, and characterized them. Antigenicity and capacity for autoantibody binding were improved compared to the wild-type proteins. Adsorption appeared to be fast, as high plasma flow-rates could be applied. The bound autoantibodies were eluted repeatedly, allowing column reuse, without compromise in efficiency. Overall, the adsorbents were specific, efficient and suitable for use in therapy.