The cancer-testis antigen NY-ESO-1 has been targeted as a tumor-associated antigen by immunotherapeutical strategies, such as cancer vaccines. The prerequisite for a T-cell-based therapy is the induction of T cells capable of recognizing the NY-ESO-1-expressing tumor cells. In this study, we generated human T lymphocytes directed against the immunodominant NY-ESO-1 157-165 epitope known to be naturally presented with HLA-A*0201. We succeeded to isolate autorestricted and allorestricted T lymphocytes with low, intermediate or high avidity TCRs against the NY-ESO-1 peptide. The avidity of the established CTL populations correlated with their capacity of lysing HLA-A2-positive, NY-ESO-1-expressing tumor cell lines derived from different origins, e.g. melanoma and myeloma. The allorestricted NY-ESO-1-specific T lymphocytes displayed TCRs with the highest avidity and best anti-tumor recognition activity. TCRs derived from allorestricted, NY-ESO-1-specific T cells may be useful reagents for redirecting primary T cells by TCR gene transfer and, therefore, may facilitate the development of adoptive transfer regimens based on TCR-transduced T cells for the treatment of NY-ESO-1-expressing hematological malignancies and solid tumors. Endogenously processed peptide epitopes recognized by autologous CD8 1 cytotoxic T cells and CD4 1 T helper cells have been identified for several class I and II molecules, respectively, pointing to the naturally occurring T-cell repertoire. 4,5 NY-ESO-1 expression in malignant tumors correlates with poor prognosis of the patients. 6,7 This might implicate that NY-ESO-1-expressing tumors do not easily escape from an NY-ESO-1-targeted therapy through the selection of Ag-loss variants as frequently observed after immunotherapies targeting the melanoma-associated differentiation Ags. 8,9 Following NY-ESO-1-directed immunizations specific T-cell responses can be elicited in the majority of patients with NY-ESO-1-expressing cancer. 2,3,10 However, there is no strong relationship between the amount of NY-ESO-1-specific T cells induced by the vaccines and the clinically observed tumor regressions. Several mechanisms may be responsible for this phenomenon: first, the levels of antigen-specific CTLs also capable of recognizing tumor cells may still be insufficient; second, the potentially tumor-reactive T cells may be silenced by tumor-mediated tolerance; third, the TCR avidity of NY-ESO-1-specific CTLs may be low because NY-ESO-1 is ectopically expressed in the thymus 11 and, therefore, high-avidity T cells are partly deleted.These problems may be solved with the adoptive transfer of NY-ESO-1-specific T cells, which display the combination of high TCR avidity, potent tumor recognition efficiency, and excellent proliferation capacity. The widespread application of autologous, antigen-specific T lymphocytes as a treatment method is limited due to the laborious procedure of T-cell isolation and characterization if tailored for every single patient. [12][13][14][15] This hurdle can be overcome if primary...
Cancer testis (CT)-antigens belong to a class of tumor antigens that are aberrantly expressed in a variety of hematological malignancies including multiple myeloma. Owing to their restricted gene expression, CT-antigens represent potential target antigens for immunotherapeutical approaches such as vaccination and adoptive T cell transfer. As the CT-antigens are self antigens, the majority of CT-antigen-specific autologous T cells display a low avidity T cell receptor (TCR), which often results in a weak tumor recognition efficiency. Our group has been focusing on the isolation of highly avid T cells against CT-antigens that are expressed in multiple myeloma, in particular MAGE-C1, MAGE-C2, and NY-ESO-1. The experimental approach was based on the stimulation of allo-restricted cytotoxic T cells, because highly avid T cells recognizing peptide epitopes in context with foreign HLA-alleles are not depleted in the thymus. HLA-A2-negative T cells were stimulated with HLA-A2-positive allogeneic dendritic cells that had been exogenously loaded with HLA-A2-binding peptides derived from NY-ESO-1, MAGE-C1 or MAGE-C2. Using this technique we were able to isolate allo-HLA-A2-restricted cytotoxic T lymphocyte (CTL) clones with peptide-dominant binding against known and novel peptide epitopes derived from NY-ESO-1, MAGE-C1 and MAGE-C2. The expanded peptide-specific CTL clones lysed HLA-A2-positive myeloma cell lines expressing NY-ESO-1, MAGE-C1 and MAGE-C2, respectively. Of note, the MAGE-C1-specific T cells crossreacted with the corresponding MAGE-C2 peptide due to the existing sequence homology between MAGE-C1 and MAGE-C2. Current experiments focus on redirecting primary T cells toward myeloma cells by retroviral gene transfer of CT-antigen-specific TCRs. The establishment of a set of high avidity TCRs specific for CT-antigens facilitates the development of adoptive transfer regimens based on TCR-transduced T cells for the treatment of multiple myeloma.
The Cancer Testis (CT) antigen NY-ESO-1 is one of the most immunogenic cancer antigens eliciting strong humoral and cellular immune responses in tumor patients and therefore it is a promising candidate antigen for successful adoptive T cell transfer. The aim of our studies is the transfer of autologous T cells re-directed towards CT antigens by T cell receptor (TCR) gene transfer. The first precondition for genetic transfer of CT-Ag-specific TCRs is the availability of tumor-reactive CD4+ and CD8+ T cell clones that express a CT-Ag-specific TCR. Therefore, we generated the autologous CD8+ T cell clone ThP2 through stimulating HLA-A2.1− PBMCs with autologous HLA-A2+DCs loaded with synthetic NY-ESO-1157–165. After two restimulations, FACS-sorting and cloning, the T cell line specifically recognized the NY-ESO-1157–165 peptide and also specifically lysed NY-ESO-1157–165 expressing tumor cells. In addition, we generated NY-ESO-1 specific T helper1 clones from HLA-DR1+ and HLA-DR4+ healthy donors by stimulation of CD4+ T cells with autologous dendritic cells (DC) pulsed with the NY-ESO-187–111 peptide. The specificity of CD4+ T helper cell clones was determined by proliferation assays and IFN gamma ELISPOT through screening with the NY-ESO-187–111 peptide. By limiting dilution of the NYESO- 1-specific T cell populations we succeeded to isolate CD4+ T cell clones, which recognized NY-ESO-1-pulsed target cells and DCs pulsed with NY-ESO-1 protein. The second precondition for TCR gene transfer is the availability of efficient vector systems. Using vectors based upon mouse myelo-proliferative sarcoma virus (MPSV), it was possible to achieve a high transgene expression in the TCR-transduced T cells. Therefore, we cloned the TCR of the HL-A2-restricted NY-ESO-1-specific CTL clone ThP2 in the retroviral vector and documented the correct expression of the TCR-chains using peptide/HLA-multimers following retroviral transduction of peripheral PBMCs. Moreover, the NY-ESO-1 specific lysis of HLA-A2+ NY-ESO-1+ tumor cell lines after transduction in primary T cells was as well effective as the primary T cell clone. Because the expression of naive transgenic T cell receptors in recipient human T cells is often insufficient to achieve highly reactive T cell bulks we modified the TCR of the ThP2 CTL clone by, murinisation, codon optimalization or by introducing cysteins into the constant regions. Afterwards we compared the expression efficiency of the three different modifications on naive T cells by tetramer-staining. We were able to show that codon optimalization leads to an increase in the expression levels of the transgenic TCRs in human CD8+ T cells. The next step is the development of T cell transfer regiments, which are based on class-II-restricted TCR-transduced T cells.
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