Patent ID: 7193066

Claim:
A method of removing residual clostridial neurotoxin from a preparation of LH N of clostridial neurotoxin comprising: (i) applying a preparation comprising LH N of clostridial neurotoxin to a first affinity column, wherein said first affinity column comprises a first ligand immobilized on said first affinity column, and wherein said first ligand selectively binds to the residual clostridial neurotoxin but does not bind to the LH N, thereby forming an immobilized first ligand-clostridial neurotoxin complex, and an eluate comprising the LH N, wherein said eluate may contain an amount of the first ligand-clostridial neurotoxin complex that has become detached from the first affinity column; (ii) contacting said eluate with a second affinity column, wherein said second affinity column comprises a second ligand immobilized on said second affinity column, and wherein said second ligand selectively binds to the first ligand-clostridial neurotoxin complex, if present in the eluate, but does not bind to the LH N present in the eluate; and thereby removing the residual clostridial neurotoxin from the preparation of the LH N .