Functional HLA-DR T cell epitopes of CEA identified in patients with colorectal carcinoma immunized with the recombinant protein CEA.
A baculovirus-produced recombinant CEA (rCEA) protein comprising the extracellular region was used for vaccination of CRC patients with or without GM-CSF as an adjuvant cytokine. Ten patients with a significant proliferative T cell response against rCEA were selected for T cell epitope mapping. Fifteen-aa-long overlapping peptides covering the entire aa sequence of the external domain of CEA were used in a proliferation assay. In six of the patients a repeatable T cell response against at least one peptide was demonstrated. For the first time, nine functional HLA-DR epitopes of CEA were defined. Two of the peptides were recognized by more than one patient, i.e., two and three patients, respectively. Those 15-mer peptides that induced a proliferative T cell response fitted to the actual HLA-DR type (SYFPEITHI). The affinity of the native peptides for the T cell receptor was in the low to intermediate range (scores 6-19). The 15-mer peptides also contained 9-mer peptide sequences that could be predicted to bind to the actual HLA-ABC genotypes (SYFPEITHI/BIMAS). Blocking experiments using monoclonal antibodies indicated that the proliferative T cell response was both MHC class I and II restricted. The defined HLA-DR T cell epitopes were spread over the entire CEA molecule, but a higher frequency was noted towards the C-terminal. Peptides with a dual specificity may form a basis for production of subunit cancer vaccines, but modifications should be done to increase the T cell affinity, thereby optimizing the antitumoral effects of the vaccine.
Ullenhag
Gustav J
GJ
Department of Oncology, Radiology and Clinical Immunology, Section of Oncology, Uppsala University Hospital, Uppsala, Sweden.
Fagerberg
Jan
J
Strigård
Karin
K
Frödin
Jan-Erik
JE
Mellstedt
Håkan
H
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D002455:Cell Division; D015179:Colorectal Neoplasms / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology; D006684:HLA-DR Antigens / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D007114:Immunization; D008213:Lymphocyte Activation / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D014611:Vaccination
D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen; D018984:Epitopes, T-Lymphocyte; D006684:HLA-DR Antigens; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D010446:Peptide Fragments; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor