A method is provided of producing an immunogenic complex comprising a heat shock protein (hsp) coupled to a heterologous antigenic polypeptide, which method comprises: (a) expressing the antigenic polypeptide in a cell which cell has been subjected to a stimulus which causes the induction of a heat shock response in said cells; and (b) recovering the antigenic polypeptide coupled to one or more hsps from said cell or the culture medium. Also provided are immunogenic compositions comprising a heat shock protein (hsp) derived from a non-mammalian eukaryote coupled to a heterologous antigenic polypeptide which composition is capable of inducing an immune response to said antigenic polypeptide in a human or animal.