T-cell responses directed against multiple HLA-A*0201-restricted epitopes derived from Wilms' tumor 1 protein in patients with leukemia and healthy donors: Identification, quantification, and characterization
ABSTRACT Antigens derived from the Wilms' tumor (WT1) protein, which is overexpressed in leukemias, are attractive targets for immunotherapy. Four HLA-A*0201-restricted WT1-derived epitopes have been identified: WT37, WT126, WT187, and WT235. We determined the natural immunogenecity of these antigens in patients with hematologic malignancies and healthy donor.
To detect very low frequencies of WT1-specific CD8+ T cells, we used quantitative reverse transcription-PCR to measure IFN-gamma mRNA production by WT1 peptide-pulsed CD8+ T cells from 12 healthy donors, 8 patients with chronic myelogenous leukemia, 6 patients with acute myelogenous leukemia, and 8 patients with acute lymphoblastic leukemia.
Responses were detected in 5 of 8 chronic myelogenous leukemia patients, 4 of 6 patients with acute myelogenous leukemia, and 7 of 12 healthy donors. No responses were detected in patients with acute lymphoblastic leukemia. The magnitude and extent of these CD8+ T-cell responses was greater in patients with myeloid leukemias than in healthy donors. Clonotypic analysis of WT1-specific CD8+ T cells directly ex vivo in one case showed that this naturally occurring population was oligoclonal. Using fluorescent peptide-MHC class I tetramers incorporating mutations in the alpha3 domain (D227K/T228A) that abrogate binding to the CD8 coreceptor, we were able to confirm the presence of high-avidity T-cell clones within the antigen-specific repertoire.
The natural occurrence of high-avidity WT1-specific CD8+ T cells in the periphery could facilitate vaccination strategies to expand immune responses against myeloid leukemias.
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- "The relative contribution of alloreactive cells, as compared with TAAs specific T cells is not difficult to quantify, however since most TAAs are aberrantly expressed self-proteins resulting in T cells with low-affinity TCR, it is possible that the alloreactive component is more determinant for GvL. Additionally, although low frequency TAA specific T cells are transferred to patients after allo-HSCT or DLI, they do not persist (Rezvani et al., 2005, 2007), potentially due to activation-induced apoptosis (Molldrem et al., 2003), or terminally differentiated effector memory phenotype (Brenchley et al., 2003). Given the successful abrogation of GVHD in vivo, several ongoing clinical trials have replaced the time consuming in vitro allo-depletion step with in vivo allo-depletion using AP1903 for those developing GVHD in the haploidentical (Clinicaltrials.gov "
ABSTRACT: Adoptive T-cell therapy can involve donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation, the administration of tumor infiltrating lymphocyte (TILs) expanded ex-vivo, or more recently the use of T cell receptor (TCR) or chimeric antigen receptor (CAR) redirected T cells. However cellular therapies can pose significant risks, including graft-versus-host-disease and other on and off-target effects, and therefore strategies need to be implemented to permanently reverse any sign of toxicity. A suicide gene is a genetically encoded molecule that allows selective destruction of adoptively transferred cells. Suicide gene addition to cellular therapeutic products can lead to selective ablation of gene-modified cells, preventing collateral damage to contiguous cells and/or tissues. The ‘ideal’ suicide gene would ensure the safety of gene modified cellular applications by granting irreversible elimination of ‘all’ and ‘only’ the cells responsible for the unwanted toxicity. This review presents the suicide gene safety systems reported to date, with a focus on the state-of-the-art and potential applications regarding two of the most extensively validated suicide genes, including the clinical setting: herpes-simplex-thymidine-kinase (HSV-TK) and inducible-caspase-9 (iCasp9).Frontiers in Pharmacology 10/2014; 5(524). DOI:10.3389/fphar.2014.00254 · 3.80 Impact Factor
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- "Although WT1 is expressed in normal tissues during embryogenesis, immunological tolerance to WT1 is not complete: WT1-specific CTLs have been detected and expanded following exposure to the peptide both in healthy donors (Rezvani et al, 2003) and in patients with AML (Scheibenbogen et al, 2002). Recent studies have shown immune and clinical responses with peptide vaccinations against single epitopes of WT1 (Oka et al, 2004; Keilholz et al, 2009); however, naturally occurring CD8 + T cell responses against myeloid leukaemias target multiple epitopes , potentially enhancing the strength and diversity of these responses (Gannag e et al, 2005; Rezvani et al, 2005). We have identified two distinct peptide epitopes of WT1 that are presented by HLA-A0201 (A2) and function as targets for leukaemia-reactive CD8 + CTL: pWT126 and pWT235 (Bellantuono et al, 2002). "
ABSTRACT: Wilms' Tumour 1 (WT1) is a zinc finger transcription factor that is over-expressed in acute myeloid leukaemia (AML). Its restricted expression in normal tissues makes it a promising target for novel immunotherapies aiming to accentuate the cytotoxic T lymphocyte (CTL) response against AML. Here we report a phase I/II clinical trial of subcutaneous peptide vaccination with two separate HLA-A2-binding peptide epitopes derived from WT1, together with a pan-DR binding peptide epitope (PADRE), in Montanide adjuvant. Eight HLA-A2-positive patients with poor risk AML received five vaccination cycles at 3-weekly intervals. The three cohorts received 0·3, 0·6 and 1 mg of each peptide, respectively. In six patients, WT1-specific CTL responses were detected using enzyme-linked immunosorbent spot assays and pWT126/HLA-A*0201 tetramer staining, after ex vivo stimulation with the relevant WT1 peptides. However, re-stimulation of these WT1-specific T cells failed to elicit secondary expansion in all four patients tested, suggesting that the WT1-specific CD8(+) T cells generated following vaccination may be functionally impaired. No correlation was observed between peptide dose, cellular immune response, reduction in WT1 mRNA expression and clinical response. Larger studies are indicated to confirm these findings.British Journal of Haematology 02/2014; 164(3):366-75. DOI:10.1111/bjh.12637 · 4.96 Impact Factor
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- "As at least one study has shown clonal diversity in the CD8+ T cell response to WT1 126 antigen (Rezvani et al., 2005), the structural differences observed here suggest caution in the use of the R1Y variant of the WT1 126 antigen as a therapeutic vaccine. Expanded studies are likely to reveal differences in TCR binding properties and thus the sets of T cells that respond to the two peptides. "
ABSTRACT: Presentation of peptides by class I or class II major histocompatibility complex (MHC) molecules is required for the initiation and propagation of a T cell-mediated immune response. Peptides from the Wilms Tumor 1 transcription factor (WT1), upregulated in many hematopoetic and solid tumors, can be recognized by T cells and numerous efforts are underway to engineer WT1-based cancer vaccines. Here we determined the structures of the class I MHC molecule HLA-A*0201 bound to the native 126-134 epitope of the WT1 peptide and a recently described variant (R1Y) with improved MHC binding. The R1Y variant, a potential vaccine candidate, alters the positions of MHC charged side chains near the peptide N-terminus and significantly reduces the peptide/MHC electrostatic surface potential. These alterations indicate that the R1Y variant is an imperfect mimic of the native WT1 peptide, and suggest caution in its use as a therapeutic vaccine. Stability measurements revealed how the R1Y substitution enhances MHC binding affinity, and together with the structures suggest a strategy for engineering WT1 variants with improved MHC binding that retain the structural features of the native peptide/MHC complex.Molecular Immunology 09/2010; 47(15):2519-24. DOI:10.1016/j.molimm.2010.06.005 · 3.00 Impact Factor