The present invention relates to molecules, which can be used to induce a therapeutic or prophylactic immune response against MAP. In particular, the present invention relates to polypeptides comprising an alipC polypeptide sequence, a gsd polypeptide sequence, a p12 polypeptide sequence and an mpa polypeptide sequence, wherein said ahpC polypeptide comprises the sequence of SEQ ID NO: 2, a variant thereof having more than 70% amino acid sequence identity to SEQ ID NO: 2 across the full length of SEQ ID NO: 2, or a fragment of at least 8 amino acids of SEQ ID NO: 2 which comprises an epitope; said gsd polypeptide comprises the sequence of SEQ ID NO: 6, a variant thereof having more than 70% amino acid sequence identity to SEQ ID NO: 6 across the full length of SEQ ID NO: 6, or a fragment of at least 8 amino acids of SEQ ID NO: 6 which comprises an epitope; said pi 2 polypeptide comprises the sequence of SEQ ID NO: 10, a variant thereof having more than 70% amino acid sequence identity to SEQ ID NO: 10 across the full length of SEQ ID NO: 10, or a fragment of at least 8 amino acids of SEQ ID NO: 10 which comprises an epitope; and said mpa polypeptide comprises the sequence of SEQ ID NO: 14, a variant thereof having more than 70% amino acid sequence identity to SEQ ID NO: 14 across the full length of SEQ ID NO: 14, or a fragment of at least 8 amino acids of SEQ ID NO: 14 which comprises an epitope. Preferably such a variant maintains the ability to generate an immune response against the unmodified polypeptide.