Are substrates of type III secretion targets of protective CD8+ T-cells?

Ando van der Velden

Yersinia and Salmonella are gram negative bacteria that cause diseases ranging from relatively mild gastroenteritis (Y. enterocolitica, Y. pseudotuberculosis, and several Salmonella species) to typhoid fever (S. typhi) and bubonic plague (Y. pestis). Among the factors required for Yersinia and Salmonella virulence is a functional type III secretion system. When bound to host cells, the type III secretion apparatus allows the organisms to inject a subset of bacterial proteins directly into the cytosol of the host cell. These translocated proteins have a variety of effects on the host cell. Effects of these translocated proteins include manipulation of host cell actin and other structural proteins and modification of host cell signal transduction pathways. We have found that these translocated substrates of the type III secretion apparatus are processed and presented by MHC-I molecules. Our work is directed towards understanding to what extent recognition of these translocated proteins by CD8+ T-cells mediates clearance of the pathogen.