DNA vaccination represents an anticipated approach for the control of numerous infectious diseases. Used alone, however, DNA vaccine is weak immunogen inferior to viral vectors. In recent, heterologous prime-boost vaccination leads DNA vaccines to practical reality.

We assessed prime-boost immunization strategies with a DNA vaccine (minigene, gB_498-505 DNA) and recombinant vaccinia virus (vvgB_498-505) expressing epitope gB_498-505 (SSIEFARL) of CD8+ T cells specific for glycoprotein B (gB) of herpes simplex virus (HSV). Animals were immunized primarily with gB_498-505 epitope-expressing DNA vaccine/recombinant vaccinia virus and boosted with alternative vaccine type expressing entire Ag.

In prime-boost protocols using vvgBw (recombinant vaccinia virus expressing entire Ag) and vvgB_498-505, CD8+ T cell-mediated immunity was induced maximally at both acute and memory stages if primed with vvgBw and boosted with vvgB_498-505 as evaluated by CTL activity, intracellular IFN-staining, and MHC class I tetramer staining. Similarly gB_498-505 DNA prime-gBw DNA (DNA vaccine expressing entire Ag) boost immunization elicited the strongest CD8+ T cell responses in protocols based on DNA vaccine. However, the level of CD8+ T cell-mediated immunity induced with prime-boost vaccination using DNA vaccine expressing epitope or entire Ag was inferior to those based on vvgBw and vvgB_498-505. Of particular interest CD8+ T cell-mediated immunity was optimally induced when vvgB_498-505 was used to prime and gB DNA was used as alternative boost. Especially CD8+ T cell responses induced by such protocol was longer lasted than other protocols.

These facts direct to search for the effective strategy to induce optimal CD8+ T cell-mediated immunity against cancer and viral infection.