DNA-Based Vaccination with Polycistronic Expression Plasmids

DNA-based vaccination is a potent technique to prime cellular (T-cell mediated) immune responses (reviewed in 1 ). Many details of the priming of T-cell precursors by antigen translated from injected expression plasmid DNA are unknown. The relevant cell that is transfected in situ after DNA vaccination and that can process and present the protein in an immunogenic form has not yet been identified. Alternatively, the transfected cell may initiate ‘cross-priming’ in vivo by transferring processed antigen to a professional antigen-presenting cell (APC).