With DNA vaccines, the subject is not injected with the antigen but with DNA encoding the antigen.

• DNA sequences encoding one or more protein antigens or, often, simply epitopes of the complete antigen(s);
• DNA sequences incorporating a promoter that will enable the DNA to be efficiently transcribed in the human cells.
• Sometimes DNA sequences encoding
  • costimulatory molecules
  • sequences that target the expressed protein to specific intracellular locations (e.g., endoplasmic reticulum)
  are included as well.

In contrast to conventional vaccines, DNA vaccines elicit cell-mediated — as well as antibody-mediated — immune responses.

The cell-mediated response

• The plasmid is taken up by an antigen-presenting cell (APC) like a dendritic cell.
• The gene(s) encoding the various components are transcribed and translated.
• The protein products are degraded into peptides.
• These are exposed at the cell surface nestled in class I histocompatibility molecules where
• they serve as a powerful stimulant for the development of cell-mediated immunity.