Tetanus toxin (TeNT) is a potent neurotoxin produced by Clostridium tetani. TeNT is similar in structure and function to the botulinum toxins produced by other Clostridium species (1, 2). TeNT is among the most toxic protein toxins known for humans. TeNT is synthesized as an inactive single chain precursor that undergoes proteolytic cleavage to create light and heavy chains that are linked by a disulfide bond. The 50 kDa light chain contains a metalloprotease domain whereas the 100 kDa heavy chain contains a receptor binding domain and a domain required for translocation across the cell membrane (3). Once inside a neuronal cell the zinc metalloprotease domain is able to cleave synaptobrevin to cause motor neuron disinhibition, resulting in the spastic paralysis characteristic of tetanus (4). The E. coli expressed recombinant TeNT light chain is an active protease. In the absence of heavy chains, however, it lacks toxicity because it cannot enter into host cells.