Cancer immunotherapy using a DNA vaccine encoding the translocation domainof a bacterial toxin linked to a tumor antigen

Certain domains of bacterial toxins have been shown to facilitate transloca tion from extracellular and vesicular compartments into the cytoplasm. This feature represents an opportunity to enhance class I presentation of exoge nous antigen to CD8(+) T cells. We investigated this notion by creating a n ovel fusion of the translocation domain (domain II) of Pseudomonas aerugino sa exotoxin A (ETA(dII)) with a model tumor antigen, human papillomavirus t ype 16 E7, in the context of a DNA vaccine. Our in vitro studies indicated that cells transfected with ETA-(dII)/E7 DNA or dendritic cells pulsed with IJ sates containing ETA(dII)/E7 protein exhibited enhanced MHC class I pre sentation of E7 antigen. Vaccination of mice with ETA(dII)/E7 DNA generated a dramatic increase in the number of E7-specific CD8(+) T cell precursors (similar to 30-fold compared with wild-type E7 DNA) and converted a less ef fective DNA vaccine into one with significant potency against human papillo mavirus type 16 E7-expressing murine tumors via a CD8-dependent pathway, Th ese results indicate that fusion of the translocation domain of a bacterial toxin to an antigen may greatly enhance vaccine potency.