Bacterial systems for the delivery of eukaryotic antigen expression vectors

Attenuated bacterial strains allow the administration of recombinant vaccin es via the mucosal surfaces. Whereas attenuated bacteria are generally engi neered to express heterologous antigens, a novel approach employs intracell ular bacteria for the delivery of eukaryotic antigen expression vectors (so -called DNA vaccines). This strategy allows a direct delivery of DNA to pro fessional antigen-presenting cells (APC), such as macrophages and dendritic cells (DC), through bacterial infection. The bacteria used for DNA vaccine delivery either enter the host cell cytosol after phagocytosis by the APC, for example, Shigella and Listeria, or they remain in the phagosomal compa rtment, such as Salmonella. Both intracellular localizations of the bacteri al carriers seem to be suitable for successful delivery of DNA vaccine vect ors.