title: CD4(+) T cells from healthy subjects and colon cancer patients recognize a carcinoembryonic antigen-specific immunodominant epitope.
abstract: The carcinoembryonic antigen (CEA) is an attractive target for immunotherapeutic purposes because of its expression profile, its role in tumor progression, and its immunogenicity. However, CEA belongs to the CD66 immunoglobulin super-gene family that comprises highly homologous molecules expressed on leukocytes, making CEA a potential autoantigen expressed on hematopoietic cells. We used a MHC class II epitope prediction algorithm (TEPITOPE) to select 11 sequence segments of CEA that could form promiscuous CD4(+) T-cell epitopes and used synthetic peptides corresponding to the predicted sequences to propagate in vitro CD4(+) T cells from healthy donors and colon cancer patients. CD4(+) T cells from all subjects strongly recognized the sequence segment (LWWVNNQSLPVSP), repeated at residues 177-189 and 355-367. Importantly, we demonstrated that this highly immunodominant region contains a naturally processed epitope(s). Cross-recognition experiments with peptide analogues present on the CD66 homologous proteins showed that CEA(177-189/355-367)-specific CD4(+) T cells did not recognize the analogues, demonstrating that recognition of the immunodominant epitope is CEA specific. These data suggest that the repertoire of CEA(177-189/355-367)-specific CD4(+) T cells might have been shaped by a selective process to exclude CD4(+) T cells specific for CD66 homologues expressed on leukocyte, while preserving the CEA-specific repertoire. The features of strong immunogenicity and immunodominance in the absence of potential induction of autoimmunity make the identified CEA epitope of particular interest for the development of antitumor vaccines.
authors.affiliation: Experimental Immunology Unit, Cancer Immunotherapy and Gene Therapy Program, Scientific Institute H. San Raffaele, 20132 Milan, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Campi
authors.forename: Mariacristina
authors.initials: M
authors.lastname: Crosti
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Consogno
authors.forename: Valeria
authors.initials: V
authors.lastname: Facchinetti
authors.forename: Bianca M
authors.initials: BM
authors.lastname: Conti-Fine
authors.forename: Renato
authors.initials: R
authors.lastname: Longhi
authors.forename: Giulia
authors.initials: G
authors.lastname: Casorati
authors.forename: Paolo
authors.initials: P
authors.lastname: Dellabona
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Protti
mesh_terms: D000483:Alleles; D015703:Antigens, CD / Q000276:immunology; D000943:Antigens, Differentiation / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D015815:Cell Adhesion Molecules; D003110:Colonic Neoplasms / Q000276:immunology*; D003429:Cross Reactions; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D006684:HLA-DR Antigens / Q000235:genetics / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000276:immunology; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; C069847:CD66 antigens; D002272:Carcinoembryonic Antigen; D015815:Cell Adhesion Molecules; D018984:Epitopes, T-Lymphocyte; D006684:HLA-DR Antigens; D016056:Immunodominant Epitopes; D010446:Peptide Fragments