Peptide vaccination breaks tolerance to HER-2/neu by generating vaccine-specific FasL(+) CD4(+) T cells: first evidence for intratumor apoptotic regulatory T cells.
BALB/c mice transgenic (Tg) for the transforming rat neu oncogene (BALB-neuT) are genetically predestined to develop mammary carcinogenesis in a process similar to that in humans. We crossed HLA-A2.1/HLA-DR1 (A2.1/DR1) Tg mice with BALB-neuT mice to generate A2.1/DR1 x BALB-neuT triple Tg (A2.1/DR1 x neuT(+)) mice, which represent an improvement over BALB-neuT mice for evaluating vaccination regimens to overcome tolerance against HER-2/neu. A vaccine formulation strategy, consisting of synthetic peptides from the rat HER-2/neu oncogene combined with granulocyte macrophage colony-stimulating factor, was highly effective in preventing the growth of established transplantable tumors in male A2.1/DR1 x neuT(+) mice. Vaccination with HER-2(435-443) (p435) CTL peptide alone induced weak antitumor responses, which were characterized by increased numbers of regulatory T cells (Treg) and low numbers of vaccine-specific CD8(+) CTL and helper T cells (Th). The administration of p435 plus HER-2(776-790) (p776; helper peptide) reversed this situation, inducing functionally active, peptide-specific CTL and Th. There was a striking change in the intratumoral balance of Tregs (decrease) and vaccine-specific Th (increase) that directly correlated with tumor rejection. Intratumoral administration of anti-FasL antibody promoted tumor growth. The decrease in Tregs (Fas(+)) was due to apoptosis induced by cell contact with Fas ligand(+) (L)(+) Th. Mice vaccinated with p435 plus p776 exhibited long-lasting antitumor immunity. Our vaccine regimen also significantly delayed the outgrowth of mammary carcinomas in female A2.1/DR1 x neuT(+) animals. We provide a mechanism to overcome tolerance against HER-2/neu, which proposes a combined vaccination with two (Th and CTL) HER-2 peptides against HER-2/neu-expressing tumors.
Gritzapis
Angelos D
AD
Cancer Immunology and Immunotherapy Center, Saint Savas Cancer Hospital, 171 Alexandras Avenue, 11522 Athens, Greece. adgritzapis@ciic.gr
Voutsas
Ioannis F
IF
Lekka
Eftychia
E
Papamichail
Michael
M
Baxevanis
Constantin N
CN
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology* / Q000494:pharmacology; D053222:Fas Ligand Protein / Q000276:immunology*; D005260:Female; D015789:HLA-A2 Antigen / Q000276:immunology; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000276:immunology* / Q000517:prevention & control*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000473:pathology; D022223:Vaccines, Subunit / Q000276:immunology* / Q000494:pharmacology
D019496:Cancer Vaccines; D053222:Fas Ligand Protein; D015789:HLA-A2 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D022223:Vaccines, Subunit; C505658:Fasl protein, mouse