Immunization of mice against tetanus with fragments of tetanus toxin synthesized in Escherichia coli.

Two recombinant plasmids, pTet11 and pTet18, which express nontoxic protein fragments of tetanus toxin in Escherichia coli, were constructed. pTet11 protein (86 kilodaltons) is a fusion between part of the E. coli trpE protein and 441 amino acids of tetanus fragment C, and pTet18 (63 kilodaltons) consists of part of fragment B and all of fragment C of tetanus toxin. The synthesis of these proteins was induced in E. coli cultures, and the proteins were partially purified. Mice were immunized with these proteins, and dose-dependent titers of anti-tetanus toxoid antibodies were obtained. The proteins were able to induce neutralizing antibodies in mice, as demonstrated by the ability of mice immunized with 1 microgram or more of protein to survive challenge with 10 50% lethal doses of tetanus toxin.