title: DNA fusion gene vaccination mobilizes effective anti-leukemic cytotoxic T lymphocytes from a tolerized repertoire.
abstract: The majority of known human tumor-associated antigens derive from non-mutated self proteins. T cell tolerance, essential to prevent autoimmunity, must therefore be cautiously circumvented to generate cytotoxic T cell responses against these targets. Our strategy uses DNA fusion vaccines to activate high levels of peptide-specific CTL. Key foreign sequences from tetanus toxin activate tolerance-breaking CD4(+) T cell help. Candidate MHC class I-binding tumor peptide sequences are fused to the C terminus for optimal processing and presentation. To model performance against a leukemia-associated antigen in a tolerized setting, we constructed a fusion vaccine encoding an immunodominant CTL epitope derived from Friend murine leukemia virus gag protein (FMuLV(gag)) and vaccinated tolerant FMuLV(gag)-transgenic (gag-Tg) mice. Vaccination with the construct induced epitope-specific IFN-gamma-producing CD8(+) T cells in normal and gag-Tg mice. The frequency and avidity of activated cells were reduced in gag-Tg mice, and no autoimmune injury resulted. However, these CD8(+) T cells did exhibit gag-specific cytotoxicity in vitro and in vivo. Also, epitope-specific CTL killed FBL-3 leukemia cells expressing endogenous FMuLV(gag) antigen and protected against leukemia challenge in vivo. These results demonstrate a simple strategy to engage anti-microbial T cell help to activate epitope-specific polyclonal CD8(+) T cell responses from a residual tolerized repertoire.
authors.affiliation: Molecular Immunology Group, Cancer Sciences Division, University of Southampton School of Medicine, Southampton, UK. J.Rice@soton.ac.uk <J.Rice@soton.ac.uk>
authors.forename: Jason
authors.initials: J
authors.lastname: Rice
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Dossett
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlén
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Buchan
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kendall
authors.forename: Stuart N
authors.initials: SN
authors.lastname: Dunn
authors.forename: Freda K
authors.initials: FK
authors.lastname: Stevenson
authors.forename: Philip D
authors.initials: PD
authors.lastname: Greenberg
mesh_terms: D000818:Animals; D019677:Artificial Gene Fusion; D015551:Autoimmunity; D019496:Cancer Vaccines / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte; D005622:Friend murine leukemia virus / Q000276:immunology; D015683:Gene Products, gag / Q000235:genetics / Q000276:immunology; D007108:Immune Tolerance; D007938:Leukemia / Q000276:immunology* / Q000628:therapy; D008099:Liver / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D013950:Thymus Gland / Q000378:metabolism; D014611:Vaccination; D019444:Vaccines, DNA / Q000276:immunology*
chemical_list: D019496:Cancer Vaccines; D018984:Epitopes, T-Lymphocyte; D015683:Gene Products, gag; D019444:Vaccines, DNA