Gram-positive and Gram-negative bacteria as carrier systems for DNA vaccines.

Vaccination by intradermal or intramuscular injection of eukaryotic antigen expression vectors (so-called DNA vaccines) elicits strong cellular and humoral immune responses. A novel approach employs attenuated mutant strains of Gram-positive and Gram-negative intracellular bacteria as carriers for the delivery of DNA vaccines. This strategy allows the administration of the DNA vaccines via mucosal surfaces and a direct delivery of the plasmid DNA to professional antigen presenting cells (APC), such as macrophages and dendritic cells (DC). In this work, we have found that several Gram-negative bacteria are capable of delivering plasmid vectors to human DC. In addition, we tested the suitability of the Gram-positive bacterium Listeria monocytogenes as a vaccine carrier for the immunization of fish.