Modified epitopes for boosting CD4+ T-cell responses
The present invention relates to immunogenic peptides comprising a T-cell epitope. Said peptides are modified such that CD4+ T-cell responses are obtainable that are much stronger than the CD4+ T-cell responses obtained with the same peptides not comprising said modification. In particular, the modification is the addition of a cysteine, insertion of a cysteine or mutation into a cysteine of a residue at a position adjacent to but outside the MHC-binding site of the peptide. Further disclosed are the use of such modified peptides in treating, suppressing or preventing diseases such as infectious or allergic diseases and autoimmune diseases, in preventing or suppressing graft rejection, or in the eradication of tumor cells.
1. A unit dosage form comprising an active ingredient consisting of an isolated peptide with a length of between 9 and 30 amino acids, wherein said peptide consists of:
a) a natural MHC class II T cell epitope of a protein, said epitope comprising an 8 or 9 amino acid sequence that is capable of binding into the cleft of a human MHC class II molecule, and
b) an amino acid or a sequence of between 2 and 6 amino acids at the n-terminal and/or c-terminal side of the MHC class II T cell epitope of a), comprising a reducing cysteine residue separated by at most 5 amino acids from the n-terminal and/or c-terminal end, respectively, of the 8 or 9 amino acid sequence that is capable of binding into the cleft of the human MHC class II molecule, wherein said cysteine residue does not occur as part of a cysteine disulfide bridge,
wherein said amino acid or said sequence of between 2 and 6 amino acids does not comprise a C-xx-[CST] or [CST]-xx-C redox motif sequence,
wherein said cysteine residue does not occur in a sequence with the motif C-xx-[CST] or [CST]-xx-C, and
wherein said isolated peptide is an artificial peptide wherein the sequence defined in part a) and b) differs from the sequence as occurring in the wild type sequence of said protein.
2. The unit dosage form according to claim 1 , wherein the amino acid or the sequence of between 2 and 6 amino acids defined in part b) contains only one cysteine.
3. The unit dosage form according to claim 1 , wherein said peptide has a length of between 9 and 20 amino acids.