title: Antibody and CD8+ T cell responses against HER2/neu required for tumor eradication after DNA immunization with a Flt-3 ligand fusion vaccine.
abstract: OBJECTIVE
  HER2/neu is frequently overexpressed in breast cancer. In a mouse model, vaccination with HER2/neu DNA elicits antibodies that confer partial protection against tumor challenge.
  
  
  METHODS
  To enhance antitumor immunity, we fused cDNA encoding Flt-3 ligand (FL) to the rat HER2/neu extracellular domain (neu), generating a chimeric FLneu molecule. FLneu and neu DNA vaccines were compared for immunogenicity and their ability to protect mice from tumor challenge.
  
  
  RESULTS
  The neu vaccine generated a HER2/neu-specific antibody response. In contrast, vaccination with FLneu induced CD8+ T cells specific for HER2/neu but a negligible anti-HER2/neu antibody response. The switch from an antibody-mediated to T cell-mediated response was due to different intracellular localization of neu and FLneu. Although the neu protein was secreted, the FLneu protein was retained inside the cell, co-localizing with the endoplasmic reticulum, facilitating processing and presentation to T cells. The neu and FLneu vaccines individually conferred only weak tumor immunity. However, efficient tumor rejection was seen when neu and FLneu were combined, inducing both strong anti-HER2/neu-specific antibody and T cell responses. Adoptive transfer of both immune CD8+ T cells and immune sera from immunized mice was required to confer tumor immunity in naïve hosts.
  
  
  CONCLUSIONS
  These results show that active induction of both humoral and cellular immunity to HER2/neu is required for efficient tumor protection, and that neither response alone is sufficient.
authors.affiliation: Swim Across America Laboratory, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: Francesca
authors.initials: F
authors.lastname: Orlandi
authors.forename: Franco M
authors.initials: FM
authors.lastname: Venanzi
authors.forename: Antonio
authors.initials: A
authors.lastname: Concetti
authors.forename: Hanako
authors.initials: H
authors.lastname: Yamauchi
authors.forename: Shakuntala
authors.initials: S
authors.lastname: Tiwari
authors.forename: Larry
authors.initials: L
authors.lastname: Norton
authors.forename: Jedd D
authors.initials: JD
authors.lastname: Wolchok
authors.forename: Alan N
authors.initials: AN
authors.lastname: Houghton
authors.forename: Polly D
authors.initials: PD
authors.lastname: Gregor
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D019556:COS Cells; D019496:Cancer Vaccines; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry*; D005260:Female; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry*; D051379:Mice; D008856:Microscopy, Fluorescence; D009368:Neoplasm Transplantation; D009439:Neuraminidase / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013601:T-Lymphocytes / Q000378:metabolism; D013997:Time Factors; D019444:Vaccines, DNA / Q000737:chemistry
chemical_list: D019496:Cancer Vaccines; D008024:Ligands; D008565:Membrane Proteins; D019444:Vaccines, DNA; C084881:flt3 ligand protein; D004247:DNA; C403285:NEU2 protein, human; D009439:Neuraminidase