In vitro Stimulation with WT1 Peptide-Loaded Epstein-Barr Virus-Positive B Cells Elicits High Frequencies of WT1 Peptide-Specific T Cells with In vitro and In vivo Tumoricidal Activity

The Wilms tumor protein (WT1) is overexpressed in most acute and chronic leukemias. To develop a practicable, clinically applicable approach for generation of WT1-specific T cells and to comparatively evaluate the immunogenicity of WT1 in normal individuals, we sensitized T cells from 13 HLA-A0201 + and 5 HLA-A2402 + donors with autologous EBV-transformed B cells or cytokine-activated monocytes, loaded with the HLA-A0201 -binding WT1 peptides 126–134 RMFPNAPYL or 187–195 SLGEQQYSV or a newly identified HLA-A2402 -binding WT1 peptide 301–310 RVPGVAPTL. WT1-specific T cells were regularly generated from each donor. T cells sensitized with peptide-loaded EBV-transformed B cells generated higher numbers of WT1-specific T cells than peptide-loaded cytokine-activated monocytes. Contrary to expectations, the frequencies of WT1 peptide-specific T cells were equivalent to those generated against individual highly immunogenic HLA-A0201 -binding EBV peptides. Each of these T-cell lines specifically killed WT1 + leukemias and solid tumors in an HLA-restricted manner but did not lyse autologous or HLA-matched normal CD34 + hematopoietic progenitor cells or reduce their yield of colony-forming unit-granulocyte-macrophage (CFU-GM), burst-forming unit erythroid (BFU-E), or mixed colonies (CFU-mix). Furthermore, WT1 peptide-specific T cells after adoptive transfer into nonobese diabetic-severe combined immunodeficient mice bearing subcutaneous xenografts of WT1 + and WT1 − HLA-A0201 + leukemias preferentially accumulated in and induced regressions of WT1 + leukemias that expressed the restricting HLA allele. Such cells are clinically applicable and may prove useful for adoptive cell therapy of WT1 + malignant diseases in humans.