Abstract: The invention relates to nucleic acids (such as DNA immunization plasmids), encoding fusion proteins containing a destabilizing amino acid sequence attached to an amino acid sequence of interest, in which the immunogenicity of the amino acid sequence of interest is increased by the presence of the destabilizing amino acid sequence. The invention also relates to nucleic acids encoding secreted fusion proteins, such as those containing chemokines or cytokines, and an attached amino acid sequence of interest, in which the immunogenicity of the amino acid sequence of interest is increased as a result of being attached to the secretory sequence. The invention also relates methods of increasing the immunogenicity of the encoded proteins for use as vaccines or in gene therapy.