Characterization of Recombinant Tetanus Toxin Derivatives Suitable for Vaccine Development

Recombinant derivatives of tetanus toxin (TeTx) were isolated and used to immunize mice. Recombinant TeTx light chain, a derivative of fragment C that had lost the ability to bind neurons, and a recombinant TeTx holotoxoid that could protect mice against TeTx challenge were identified. Tetanus toxin (TeTx), a neurotoxin produced by Clostridium tetani, is a 150-kDa protein, containing a 50-kDa amino-termi-nal light-chain disulfide bonded to a 100-kDa heavy chain (4, 6, 16). Fragment C, the 50-kDa carboxy-terminal portion of the heavy chain, has ganglioside binding (9, 10, 14, 15) and protein binding (23) activities. Light chain, a zinc-dependent protease (24), mediates the blockade of inhibitor release from neurons by proteolysis of synaptobrevin (22). Tetanus vaccines are manufactured by formaldehyde inactivation of TeTx obtained from C. tetani. New tetanus vaccines based upon recombinant antigens are in development. Recombinant fragment C puri-fied from Escherichia coli (5, 13), yeast cells (20), or culture