Identification of two promiscuous T cell epitopes from tetanus toxin.

Tetanus toxoid-specific T cell clones were isolated from a human donor. To determine the T cell epitopes recognized by the clones, 30 peptides representing amphipathic alpha helical regions of the tetanus toxin were screened for ability to induce proliferation of the clones. Two T epitopes were identified. These occurred within peptides 12 and 21, and had the amino acid sequences NSVDDALINSTKIYSYFPSV and PGINGKAIHLVNNESSE, respectively. An unusual feature was that both peptides could be presented to their respective T cell clones by antigen-presenting cells of many HLA specificities. Further investigation of peptide 12 showed that the epitope was only seven amino acids in length and had a very hydrophobic sequence, namely YSYFPSV. The ability of the T cell epitope-containing peptides 12 and 21 to interact with many different HLA alleles means they may potentially be very useful as "universal carrier molecules" in synthetic vaccines.