In future, we could use a dimeric TCHE memory peptide (TpD) containing both tetanus toxoid and diphtheria toxoid TCHEs linked by a cathepsin site, which strongly benefited the Ab responses to a nicotine vaccine in mice and macaques; and all 20 normal human blood donors generated a T-helper-cell recall response to the TpD peptide (67). This evidence concerns the gene CTSS and diphtheria.