The invention relates to an isolated peptide for use as a medicament, wherein said peptide has 9 to 30 amino acids and comprises or consists of an amino acid sequence according to SEQ ID NO 1 (VMAPRTLXL), wherein X is an amino acid with a hydrophobic side chain (A, I, L, F, V, P, G), preferably V, L, I or F. The invention further relates to the peptide of the invention for use as a medicament to expand and/or activate NKG2C+ natural killer (NK) cells. The invention further relates to the peptide of the invention for use in the treatment and/or prevention of a medical condition associated with pathogenic cells expressing HLA-E and a peptide comprising an amino acid sequence according to SEQ ID NO 1 or 2. Additionally, the invention relates to a genetically modified virus encoding a peptide comprising or consisting of a polypeptide of the invention for use as a medicament to expand and/or activate NKG2C+ natural killer (NK) cells.
