The invention relates to a product which comprises a C4bp domain of a non-mammalian origin, particularly SEQ ID NO:1, SEQ ID NO:23 or SEQ ID NO:37, or a variant thereof, and an antigen. The product is desirably in the form of a fusion protein. The chicken C4bp domain of SEQ ID NO:1 and SEQ ID NO:23 is also described. Antigens include monomeric antigens such as malarial and influenza antigens. The C4bp domain provides for assembly of multimeric complexes of the antigen, or mixtures thereof. The complexes are useful as vaccines.
