Bacterial type III translocation: a unique mechanism for cytosolic display of heterologous antigens by attenuated Salmonella.

Upon infection, Gram-negative animal and plant pathogens evade the host immune response by utilizing a specialized protein secretion machinery, known as type III secretion system, for the export of bacterial virulence factors delivered directly into the cytosol of target cells. This unique translocation mechanism can be used for the delivery of large protein fragments derived from immunodominant viral and bacterial heterologous antigens into the MHC class I-restricted antigen-processing pathway by attenuated Salmonella carrier vaccines. In orally immunized mice, this novel vaccination strategy results in the induction of pronounced peptide-specific cytotoxic CD8 T cell responses.