Identification of new epitopes from four different tumor-associated antigens: recognition of naturally processed epitopes correlates with HLA-A*0201-binding affinity.
Forty-two wild-type and analogue peptides derived from p53, carcinoembryonic Ag, Her2/neu, and MAGE2/3 were screened for their capacity to induce CTLs, in vitro, capable of recognizing tumor target lines. All the peptides bound HLA-A*0201 and two or more additional A2 supertype alleles with an IC(50) of 500 nM or less. A total of 20 of 22 wild-type and 9 of 12 single amino acid substitution analogues were found to be immunogenic in primary in vitro CTL induction assays, using normal PBMCs and GM-CSF/IL-4-induced dendritic cells. These results suggest that peripheral T cell tolerance does not prevent, in this system, induction of CTL responses against tumor-associated Ag peptides, and confirm that an HLA class I affinity of 500 nM or less is associated with CTL epitope immunogenicity. CTLs generated by 13 of 20 of the wild-type epitopes, 6 of 9 of the single, and 2 of 5 of the double substitution analogues tested recognized epitopes generated by endogenous processing of tumor-associated Ags and expressed by HLA-matched cancer cell lines. Further analysis revealed that recognition of naturally processed Ag was correlated with high HLA-A2.1-binding affinity (IC(50) = 200 nM or less; p = 0.008), suggesting that high binding affinity epitopes are frequently generated and can be recognized as a result of natural Ag processing. These results have implications for the development of cancer vaccines, in particular, and for the process of epitope selection in general.
Keogh
E
E
Epimmune, 5820 Nancy Ridge Drive, San Diego, CA 92121, USA.
Fikes
J
J
Southwood
S
S
Celis
E
E
Chesnut
R
R
Sette
A
A
D000483:Alleles; D019943:Amino Acid Substitution / Q000276:immunology; D017951:Antigen Presentation; D000951:Antigens, Neoplasm / Q000276:immunology / Q000378:metabolism*; D002272:Carcinoembryonic Antigen / Q000276:immunology / Q000378:metabolism; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D018984:Epitopes, T-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D005260:Female; D015789:HLA-A2 Antigen / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008213:Lymphocyte Activation; D008297:Male; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000276:immunology / Q000378:metabolism
D000951:Antigens, Neoplasm; D002272:Carcinoembryonic Antigen; D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D018719:Erb-b2 Receptor Tyrosine Kinases; D016159:Tumor Suppressor Protein p53; C072013:MAGEA3 protein, human; C072012:MAGEB2 protein, human