Isolation of T cell receptors targeting recurrent neoantigens in hematological malignancies.

Mutation-derived neoantigens represent an important class of tumour-specific, tumour rejection antigens, and are attractive targets for TCR gene therapy of cancer. The majority of such mutations are patient-specific and targeting these requires a fully personalized approach. However, some mutations are found recurrently among cancer patients, and represent potential targets for neoantigen-specific TCR gene therapy that is more widely applicable.

RNAi-mediated TCR knockdown prevents autoimmunity in mice caused by mixed TCR dimers following TCR gene transfer.

Genetically modified T cells that express a transduced T cell receptor (TCR) α/β heterodimer in addition to their endogenous TCR are used in clinical studies to treat cancer. These cells express two TCR-α and two TCR-β chains that do not only compete for CD3 proteins but also form potentially self-reactive mixed TCR dimers, composed of endogenous and transferred chains. To overcome these deficits, we developed an RNAi-TCR replacement vector that simultaneously silences the endogenous TCR and expresses an RNAi-resistant TCR.

High-throughput identification of antigen-specific TCRs by TCR gene capture.

The transfer of T cell receptor (TCR) genes into patient T cells is a promising approach for the treatment of both viral infections and cancer. Although efficient methods exist to identify antibodies for the treatment of these diseases, comparable strategies to identify TCRs have been lacking. We have developed a high-throughput DNA-based strategy to identify TCR sequences by the capture and sequencing of genomic DNA fragments encoding the TCR genes.

Blockade of TGF-β signaling greatly enhances the efficacy of TCR gene therapy of cancer.

TCR gene therapy is a promising approach for the treatment of various human malignancies. However, the tumoricidal activity of TCR-modified T cells may be limited by local immunosuppressive mechanisms within the tumor environment. In particular, many malignancies induce T cell suppression in their microenvironment by TGF-β secretion.

T-cell receptor gene therapy: critical parameters for clinical success.

T-cell receptor (TCR) gene therapy aims to induce immune reactivity against tumors by introducing genes encoding a tumor-reactive TCR into patient T cells. This approach has been extensively tested in preclinical mouse models, and initial clinical trials have demonstrated the feasibility and potential of TCR gene therapy as a cancer treatment. However, data obtained from preclinical and clinical studies suggest that both the therapeutic efficacy and the safety of TCR gene therapy can be and needs to be further enhanced.

Lethal graft-versus-host disease in mouse models of T cell receptor gene therapy.

The transfer of T cell receptor (TCR) genes can be used to induce immune reactivity toward defined antigens to which endogenous T cells are insufficiently reactive. This approach, which is called TCR gene therapy, is being developed to target tumors and pathogens, and its clinical testing has commenced in patients with cancer. In this study we show that lethal cytokine-driven autoimmune pathology can occur in mouse models of TCR gene therapy under conditions that closely mimic the clinical setting.

Adoptive therapy with redirected primary regulatory T cells results in antigen-specific suppression of arthritis.

Regulatory T cells (Tregs) can suppress a wide range of immune cells, making them an ideal candidate for the treatment of autoimmunity. The potential clinical translation of targeted therapy with antigen-specific Tregs is hampered by the difficulties of isolating rare specificities from the natural polyclonal T cell repertoire. Moreover, the initiating antigen is often unknown in autoimmune disease.

Preclinical development of T cell receptor gene therapy.

The adoptive transfer of TCR gene-modified T cells has been developed with the aim to induce immune reactivity toward defined tumor-associated antigens to which the endogenous T cell repertoire is non-responsive. Here we discuss in which areas preclinical studies in mouse models can or cannot be expected to be of value to guide clinical trial design, and how the available data from preclinical studies should influence forthcoming clinical trials.

Requirements for effective antitumor responses of TCR transduced T cells.

Adoptive transfer of TCR gene-modified T cells has been proposed as an attractive approach to target tumors for which it is difficult or impossible to induce strong tumor-specific T cell responses by vaccination. Whereas the feasibility of generating tumor Ag-specific T cells by gene transfer has been demonstrated, the factors that determine the in vivo effectiveness of TCR-modified T cells are largely unknown. We have analyzed the value of a number of clinically feasible strategies to enhance the antitumor potential of TCR modified T cells.

TCR gene therapy of spontaneous prostate carcinoma requires in vivo T cell activation.

Analogous to the clinical use of recombinant high-affinity Abs, transfer of TCR genes may be used to create a T cell compartment specific for self-Ags to which the endogenous T cell repertoire is immune tolerant. In this study, we show in a spontaneous prostate carcinoma model that the combination of vaccination with adoptive transfer of small numbers of T cells that are genetically modified with a tumor-specific TCR results in a marked suppression of tumor development, even though both treatments are by themselves without effect. These results demonstrate the value of TCR gene transfer to target otherwise nonimmunogenic tumor-associated self-Ags provided that adoptive transfer occurs under conditions that allow in vivo expansion of the TCR-modified T cells.

Generation and characterization of transgenic mice expressing a T-cell receptor specific for the tumour-associated antigen MDM2.

T-cell-based antigen-specific immunotherapy targeting tumour-associated antigens offers the potential for cancer immunotherapy. However, the majority of identified tumour-associated antigens are also expressed at low levels in normal tissues and mechanisms of tolerance induction are likely to affect the quality of T-cell responses to such antigens. In this study a T-cell receptor transgenic model was developed to determine the magnitude of T-cell tolerance to the tumour-associated antigen murine double minute-2 (MDM2), a widely expressed protein that is found at elevated levels in many tumours.

A study of T cell tolerance to the tumor-associated antigen MDM2: cytokines can restore antigen responsiveness, but not high avidity T cell function.

Background: Most tumor-associated antigens (TAA) currently used for immunotherapy of cancer are also expressed in normal tissues, which may induce tolerance and impair T cell-mediated immunity. However, there is limited information about how physiological expression in normal tissues alters the function of TAA-specific T cells.

Methodology/principal Findings: We used a T cell receptor transgenic model to study how MDM2 expression in normal tissues affects the function of T cells specific for this TAA that is found at high levels in many different types of tumors.

Broadly expressed tumour-associated proteins as targets for cytotoxic T lymphocyte-based cancer immunotherapy.

T cell-based antigen-specific immunotherapy targeting self-proteins aberrantly expressed in many tumours offers the potential for widely applicable cancer immunotherapy, but carries the risk of autoimmunity. Immunological tolerance represents an inherent limitation of cancer vaccines targeting such broadly expressed tumour-associated proteins. Therefore, strategies to circumvent T cell tolerance have been developed and, when combined with T cell receptor (TCR) gene transfer technology, can generate highly avid tumour-reactive patient cytotoxic T lymphocytes (CTLs) specific for peptide epitopes of tumour-associated proteins.

A critical role of T cell antigen receptor-transduced MHC class I-restricted helper T cells in tumor protection.

Adoptive transfer of antigen-specific CD4(+) and CD8(+) T cells is one of the most efficient forms of cancer immunotherapy. However, the isolation of antigen-specific CD4(+) T cells is limited because only few tumor-associated helper epitopes are identified. Here, we used T cell antigen receptor gene transfer to target CD4(+) T cells against an MHC class I-presented epitope of a model tumor antigen.

Induction of unresponsiveness limits tumor protection by adoptively transferred MDM2-specific cytotoxic T lymphocytes.

There is evidence showing that high avidity CTLs can be more effective than low avidity CTLs for adoptive tumor immunotherapy. Because many T cell-recognized tumor antigens are nonmutated self-proteins, tolerance mechanisms are likely to render high avidity T cells unresponsive or cause T cell elimination by clonal deletion. We recently used the allo-restricted strategy to circumvent immunologic tolerance to a ubiquitously expressed tumor-associated protein, MDM2, and raised high avidity CTLs in humans and in mice.