Peptide epitopes from the Wilms' tumor 1 oncoprotein stimulate CD4+ and CD8+ T cells that recognize and kill human malignant mesothelioma tumor cells.
OBJECTIVE
Wilms' tumor 1 protein (WT1), a transcription factor overexpressed in malignant mesothelioma, leukemias, and other solid tumors, is an ideal target for immunotherapy. WT1 class I peptide epitopes that were identified and shown to stimulate CD8(+) T cells are being tested as vaccine candidates in several clinical trials. The induction and maintenance of a robust memory CD8(+) cytotoxic T-cell response requires CD4(+) T-cell help.


METHODS
Three HLA class II peptide epitopes of WT1 with high predictive affinities to multiple HLA-DRB1 molecules were identified using the SYFPEITHI algorithm. Due to the highly polymorphic nature of the HLA class II alleles, such reactivity is critical in the development of a broadly useful therapeutic. One of the WT1 CD4(+) peptide epitopes, 122-140, comprises a previously identified CD8(+) peptide epitope (126-134). By mutating residue 126 from an arginine to a tyrosine, we embedded a synthetic immunogenic analogue CD8(+) epitope (126-134) inside the longer peptide (122-140). This analogue was previously designed to improve immunogenicity and induce a potent CD8(+) response.


RESULTS
WT1 peptides 328-349 and 423-441 are able to stimulate a peptide-specific CD4(+) response that can recognize WT1(+) tumor cells in multiple HLA-DRB1 settings as determined by IFN-gamma enzyme-linked immunospot assays. The mutated WT1 peptide epitope 122-140 is able to induce CD4(+) and cytotoxic CD8(+) WT1-specific T-cell responses that can recognize the native WT1 epitopes on the surface of human WT1(+) cancer cells. Cross-priming experiments showed that antigen-presenting cells pulsed with either mesothelioma or leukemia tumor lysates can process and present each of the CD4(+) peptides identified.


CONCLUSIONS
These studies provide the rationale for using the WT1 CD4(+) peptides in conjunction with CD8(+) peptide epitopes to vaccinate patients with WT1-expressing cancers.
Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Rena J
RJ
May
Tao
T
Dao
Javier
J
Pinilla-Ibarz
Tatyana
T
Korontsvit
Victoriya
V
Zakhaleva
Rong H
RH
Zhang
Peter
P
Maslak
David A
DA
Scheinberg
D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D002857:Chromium / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D006684:HLA-DR Antigens / Q000378:metabolism; D059811:HLA-DRB1 Chains; D006801:Humans; D007114:Immunization; D007371:Interferon-gamma / Q000378:metabolism; D007938:Leukemia / Q000276:immunology / Q000473:pathology / Q000628:therapy; D008654:Mesothelioma / Q000276:immunology / Q000473:pathology* / Q000628:therapy; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000276:immunology / Q000473:pathology; D025721:WT1 Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
D000939:Epitopes; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; D010446:Peptide Fragments; D025721:WT1 Proteins; D002857:Chromium; D007371:Interferon-gamma