title: Melan-A/MART-1-specific CD4 T cells in melanoma patients: identification of new epitopes and ex vivo visualization of specific T cells by MHC class II tetramers.
abstract: Over the past decade, many efforts have been made to identify MHC class II-restricted epitopes from different tumor-associated Ags. Melan-A/MART-1(26-35) parental or Melan-A/MART-1(26-35(A27L)) analog epitopes have been widely used in melanoma immunotherapy to induce and boost CTL responses, but only one Th epitope is currently known (Melan-A51-73, DRB1*0401 restricted). In this study, we describe two novel Melan-A/MART-1-derived sequences recognized by CD4 T cells from melanoma patients. These epitopes can be mimicked by peptides Melan-A27-40 presented by HLA-DRB1*0101 and HLA-DRB1*0102 and Melan-A25-36 presented by HLA-DQB1*0602 and HLA-DRB1*0301. CD4 T cell clones specific for these epitopes recognize Melan-A/MART-1+ tumor cells and Melan-A/MART-1-transduced EBV-B cells and recognition is reduced by inhibitors of the MHC class II presentation pathway. This suggests that the epitopes are naturally processed and presented by EBV-B cells and melanoma cells. Moreover, Melan-A-specific Abs could be detected in the serum of patients with measurable CD4 T cell responses specific for Melan-A/MART-1. Interestingly, even the short Melan-A/MART-1(26-35(A27L)) peptide was recognized by CD4 T cells from HLA-DQ6+ and HLA-DR3+ melanoma patients. Using Melan-A/MART-1(25-36)/DQ6 tetramers, we could detect Ag-specific CD4 T cells directly ex vivo in circulating lymphocytes of a melanoma patient. Together, these results provide the basis for monitoring of naturally occurring and vaccine-induced Melan-A/MART-1-specific CD4 T cell responses, allowing precise and ex vivo characterization of responding T cells.
authors.affiliation: Division of Clinical Onco-Immunology, Ludwig Institute for Cancer Research, Lausanne Branch, University Hospital, Lausanne, Switzerland.
authors.forename: Gilles
authors.initials: G
authors.lastname: Bioley
authors.forename: Camilla
authors.initials: C
authors.lastname: Jandus
authors.forename: Sandra
authors.initials: S
authors.lastname: Tuyaerts
authors.forename: Donata
authors.initials: D
authors.lastname: Rimoldi
authors.forename: William W
authors.initials: WW
authors.lastname: Kwok
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Speiser
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Tiercy
authors.forename: Kris
authors.initials: K
authors.lastname: Thielemans
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Cerottini
authors.forename: Pedro
authors.initials: P
authors.lastname: Romero
mesh_terms: D000595:Amino Acid Sequence; D017951:Antigen Presentation; D000951:Antigens, Neoplasm / Q000097:blood / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D019496:Cancer Vaccines / Q000276:immunology / Q000627:therapeutic use; D002469:Cell Separation; D002999:Clone Cells; D018984:Epitopes, T-Lymphocyte / Q000097:blood / Q000276:immunology*; D006681:HLA-D Antigens / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D006683:HLA-DQ Antigens / Q000276:immunology / Q000378:metabolism; D059866:HLA-DQ beta-Chains; D006801:Humans; D058965:MART-1 Antigen; D008545:Melanoma / Q000097:blood / Q000276:immunology* / Q000556:secondary; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000097:blood / Q000276:immunology*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology
chemical_list: D000951:Antigens, Neoplasm; D019496:Cancer Vaccines; D018984:Epitopes, T-Lymphocyte; D006681:HLA-D Antigens; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D058965:MART-1 Antigen; C548667:MLANA protein, human; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D010446:Peptide Fragments