title: Electroporation as a "prime/boost" strategy for naked DNA vaccination against a tumor antigen.
abstract: We have developed novel DNA fusion vaccines encoding tumor Ags fused to pathogen-derived sequences. This strategy activates linked T cell help and, using fragment C of tetanus toxin, amplification of anti-tumor Ab, CD4(+), and CD8(+) T cell responses is achievable in mice. However, there is concern that simple DNA vaccine injection may produce inadequate responses in larger humans. To overcome this, we tested electroporation as a method to increase the transfection efficiency and immune responses by these tumor vaccines in vivo in mice. Using a DNA vaccine expressing the CTL epitope AH1 from colon carcinoma CT26, we confirmed that effective priming and tumor protection in mice are highly dependent on vaccine dose and volume. However, suboptimal vaccination was rendered effective by electroporation, priming higher levels of AH1-specific CD8(+) T cells able to protect mice from tumor growth. Electroporation during priming with our optimal vaccination protocol did not improve CD8(+) T cell responses. In contrast, electroporation during boosting strikingly improved vaccine performance. The prime/boost strategy was also effective if electroporation was used at both priming and boosting. For Ab induction, DNA vaccination is generally less effective than protein. However, prime/boost with naked DNA followed by electroporation dramatically increased Ab levels. Thus, the priming qualities of DNA fusion vaccines, integrated with the improved Ag expression offered by electroporation, can be combined in a novel homologous prime/boost approach, to generate superior antitumor immune responses. Therefore, boosting may not require viral vectors, but simply a physical change in delivery, facilitating application to the cancer clinic.
authors.affiliation: Molecular Immunology Group, Southampton University Hospitals Trust, Southampton, United Kingdom.
authors.forename: Sarah
authors.initials: S
authors.lastname: Buchan
authors.forename: Eirik
authors.initials: E
authors.lastname: Grønevik
authors.forename: Iacob
authors.initials: I
authors.lastname: Mathiesen
authors.forename: Catherine A
authors.initials: CA
authors.lastname: King
authors.forename: Freda K
authors.initials: FK
authors.lastname: Stevenson
authors.forename: Jason
authors.initials: J
authors.lastname: Rice
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000818:Animals; D000912:Antibodies, Neoplasm / Q000096:biosynthesis; D000951:Antigens, Neoplasm / Q000276:immunology*; D019496:Cancer Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D004306:Dose-Response Relationship, Immunologic; D018274:Electroporation / Q000379:methods; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D006183:H-2 Antigens / Q000276:immunology*; D064532:Histocompatibility Antigen H-2D; D007117:Immunization, Secondary / Q000379:methods; D007074:Immunoglobulin G / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D015682:Retroviridae Proteins, Oncogenic / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014759:Viral Envelope Proteins / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D019496:Cancer Vaccines; D018984:Epitopes, T-Lymphocyte; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins; D015682:Retroviridae Proteins, Oncogenic; D019444:Vaccines, DNA; D014614:Vaccines, Synthetic; D014759:Viral Envelope Proteins