There is provided inter alia a nucleic acid construct comprising sequences encoding a) at least one invariant chain or variant thereof operatively linked to b) at least one antigenic protein or peptide or an antigenic fragment of said protein or peptide, wherein said nucleic acid construct is used for priming of a cancer vaccine, and/or said invariant chain or variant thereof does not comprise the first 17 amino acids, and/or said invariant chain or variant thereof does not comprise the LRMK amino acid residues of the KEY region, and/or said invariant chain comprises a variant of the CLIP region.
