Immunogenic peptides for use in the prevention and/or treatment of infectious diseases, autoimmune diseases, immune responses to allofactors, allergic diseases, tumors, graft rejection and immune responses against viral vectors used for gene therapy or gene vaccination

A method for preparing a peptide capable of eliciting NKT cell activation, said method comprising the steps of:

• (1) identifying within an antigenic protein a NKT cell epitope sequence comprising a [FWHY]-xx-[ILMV]-xx-[FWHY] motif, wherein x is any amino acid, wherein [FWHY] is an amino acid selected from Phe, Trp, His, and Tyr, and wherein [ILMV] is an amino acid selected from Ile, Leu, Met, and Val,
• (2) testing a peptide with a NKT cell epitope sequence identified in step (1) in vitro for activation of NKT cells when said peptide is presented by CD1d, and
• (3) providing a peptide comprising:
• a NKT cell epitope tested in step (2) and having confirmed activation of NKT cells, linked to
• a thioreductase [CST]-xx-C or C-xx-[CST] motif, wherein x is any amino acid, and wherein [CST] is an amino acid selected from Cys, Ser, and Thr, such that said thioreductase motif and said NKT cell epitope sequence are either immediately adjacent to each other or separated by a linker of at most 7 amino acids in length.