The clonotypic T cell receptor is a source of tumor-associated antigens in cutaneous T cell lymphoma

Immunobiology and treatment of cutaneous T-cell lymphoma

INTRODUCTION

Primary cutaneous T cell lymphomas (CTCL) are a heterogenous group of non-Hodgkin lymphomas derived from skin-homing T cells. These include mycosis fungoides and its leukemic variant Sezary syndrome, as well as the CD30+ lymphoproliferative disorders.

AREAS COVERED

In this review, we provide a summary of the current literature on CTCL, with a focus on the immunopathogenesis and treatment of mycosis fungoides and Sezary syndrome.

EXPERT OPINION

Recent advances in immunology have provided new insights into the biology of malignant T cells. This in turn has led to the development of new therapies that modulate the immune system to facilitate tumor clearance or target specific aspects of tumor biology.

mRNA-Based Anti-TCR CDR3 Tumour Vaccine for T-Cell Lymphoma

Efficient vaccination can be achieved by injections of in vitro transcribed mRNA (ivt mRNA) coding for antigens. This vaccine format is particularly versatile and allows the production of individualised vaccines conferring, T-cell immunity against specific cancer mutations. The CDR3 hypervariable regions of immune receptors (T-cell receptor, TCR or B-cell receptor, BCR) in the context of T- or B-cell leukaemia or lymphoma are targetable and specific sequences, similar to cancer mutations. We evaluated the functionality of an mRNA-based vaccine designed to trigger immunity against TCR CDR3 regions in an EL4 T-lymphoma cell line-derived murine in vivo model. Vaccination against the hypervariable TCR regions proved to be a feasible approach and allowed for protection against T-lymphoma, even though immune escape in terms of TCR downregulation paralleled the therapeutic effect. However, analysis of human cutaneous T-cell lymphoma samples indicated that, as is the case in B-lymphomas, the clonotypic receptor may be a driver mutation and is not downregulated upon treatment. Thus, vaccination against TCR CDR3 regions using customised ivt mRNA is a promising immunotherapy method to be explored for the treatment of patients with T-cell lymphomas.

T-cell receptor signaling in peripheral T-cell lymphoma - a review of patterns of alterations in a central growth regulatory pathway

T-cell receptor (TCR) signaling is pivotal in T-cell development and function. In peripheral T-cell lymphomas/leukemias (PTCL/L), histogenesis, transforming events, epidemiology, and clinical presentation are also closely linked to TCR-mediated influences. After reviewing the physiology of normal TCR signaling and cellular responses, we describe here the association of subgroups of PTCL/L with specific patterns of TCR activation as relevant tumor-initiating and/or tumor-sustaining programs. We identify PTCL/L with a functionally intact TCR machinery in which stimulation is possibly incited by exogenous antigens or autoantigens. Distinct from these are tumors with autonomous oncogenic signaling by dysregulated TCR components uncoupled from extrinsic receptor input. A further subset is characterized by transforming events that activate molecules acting as substitutes for TCR signaling, but triggering similar downstream cascades. We finally discuss the consequences of such a functional model for TCR-targeted therapeutic strategies including those that are being tested in the clinic and those that still require further development.

Predictors of response to extracorporeal photopheresis in advanced mycosis fungoides and Sézary syndrome

BACKGROUND

Extracorporeal photopheresis (ECP) has been utilized for more than 20 years to treat cutaneous T-cell lymphoma (CTCL), but a clinical response can take up to 9 months to manifest. This study was undertaken to determine whether clinical features, laboratory values, cytokine levels, or gene expression levels of tumor markers are useful to predict the subsequent response to ECP in CTCL patients with blood involvement.

METHODS

Twenty-one patients with CTCL treated with ECP as monotherapy for at least 6 months were retrospectively identified. Laboratory and clinical data and blood obtained at baseline, 3, and 6 months of treatment were used for analysis.

RESULTS

In pretreatment blood specimens, a lower percentage of Sézary cells and a higher absolute eosinophil count were associated with a favorable clinical response. Clinical evidence of an early response after 3 months of ECP did not reliably predict a favorable response at 6 months or beyond. Comparison of cytokines, gene transcripts, and other laboratory measures of disease did not correlate with the subsequent clinical response, although lactate dehydrogenase levels tended to decrease progressively in ECP-responsive cases and increase progressively in ECP-non-responsive cases. Additionally, serum levels of TNF-alpha significantly increased from baseline to 6 months of ECP, but was not found to correlate with the clinical response.

CONCLUSIONS

Although we found that increased eosinophils and decreased percentage of Sézary cells were associated with a favorable clinical response to ECP, we were not able to identify the predictors of ECP response within the first 3 months of treatment.

Transimmunization for cutaneous T cell lymphoma: A phase I study

Extracorporeal photochemotherapy (ECP) is a widely used immunotherapy for cutaneous T cell lymphoma (CTCL). It involves four sequential steps: conversion of blood monocytes into dendritic antigen presenting cells (DC) by repetitive adherence and disadherence to plastic surface; reinfusion of the new DC; presumed in vivo loading of the new DC with apoptotic malignant leukocytes; and expansion of the anti-tumor CD8 T cell pool. To assess the safety of a methodology designed to increase ex vivo contact between the apoptotic malignant cells and new DC prior to reinfusion, a single-center, open-label Phase I clinical study of a revised procedure--referred to as "Transimmunization"--was conducted in CTCL patients. Twenty-seven subjects were treated monthly for 3 to 5 months, alone or in combination with electron beam therapy. For those receiving Transimmunization alone, there was an overall diminution in infiltrative lesions in eleven (55%) of twenty patients. In the twelve leukemic CTCL patients, there was a significant mean reduction of 50.1% in the circulating malignant cells, as determined with family-specific anti-T cell receptor Vbeta monoclonal antibodies (P <or= 0.021). Because this therapy permits the synchronous induction and tumor loading of DC, with minimal toxicity, Transimmunization may merit further investigation in CTCL and other malignancies.

Efficacy and tolerability of currently available therapies for the mycosis fungoides and Sezary syndrome variants of cutaneous T-cell lymphoma

Primary cutaneous T-cell lymphomas are a heterogenous group of non-Hodgkin lymphomas. The characteristic clinicopathologic and immunophenotypic features and prognoses of the various cutaneous lymphomas have been recently described by the World Health Organization and European Organization for Research and Treatment of Cancer. Cutaneous T-cell lymphoma variants include mycosis fungoides and Sezary syndrome, which are generally associated, respectively, with indolent and aggressive clinical courses and are the subject of this review. Currently utilized treatments for cutaneous T-cell lymphoma include skin-directed therapies (topical agents such as corticosteroids, mechlorethamine, carmustine, and retinoids, phototherapy, superficial radiotherapy, and total skin electron beam therapy), systemic therapies (photophoresis, retinoids, denileukin diftitox, interferons, and chemotherapy), and stem cell transplantation (autologous and allogeneic). This review will describe recent advances in our understanding of the biology (immunologic, cytogenetic, and genetic) of cutaneous T-cell lymphomas and discuss the efficacy and tolerability of the current therapeutic options for cutaneous T-cell lymphomas. Disease progression in over 20% of patients with early stages of disease and the current lack of a definitive treatment which produces durable responses in advanced stages of disease indicates a critical unmet need in CTCL. New insights into the molecular and immunologic changes associated with cutaneous T-cell lymphomas should ultimately lead to the identification of novel therapeutic targets and the development of improved therapeutic options for patients with these malignancies.

Identification of HLA class I dependent immunogenic peptides from clonotypic TCRbeta expressed in cutaneous T-cell lymphoma

The clonotypic T-cell receptor (TCR) is a potential target antigen for specific immunotherapy of cutaneous T-cell lymphoma (CTCL). We identified T-cell epitopes from the rearranged TCR beta chain of the malignant T-cell population by the "reverse immunology" approach. Peptide-specific T-cell lines were generated against predicted epitopes and tested for the recognition of tumor cells and cells transfected with the full-length DNA coding for TCRV beta chain. Two peptides derived from the clonotypic TCRVbeta of a HLA-A2 positive patient could induce peptide-specific T cells from peripheral blood mononuclear cells of healthy donors and the patient as assessed by IFN-gamma ELISpot assay. Furthermore, the reactive CTLs efficiently recognized autologous Sézary tumor cells, as well as HLA-A2 positive 293 cells transfected with recombinant plasmid expressing the corresponding TCRVbeta29 protein. Similar results were obtained in a HLA-A3+ patient for TCRVbeta7-Jbeta2.7. In conclusion, our experiments show that the TCR beta chain harbors epitopes suitable as targets for specific vaccination which might be a promising approach for the specific immunotherapy of cutaneous T-cell lymphoma patients.

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.

Identifying epitopes of HIV-1 that induce protective antibodies

As with most pathogens, HIV-1 induces a polyclonal antibody response to a wide array of epitopes on different viral proteins. Studies of polyclonal sera have helped to identify several epitopes on HIV-1 envelope glycoproteins that induce protective antibodies.

Antibodies to several constant regions of the virus envelope induce neutralizing antibodies, but because of the poor immunogenicity of some of these epitopes, the rare structure of neutralizing antibodies to these epitopes, or the preponderance of antibodies to particular epitopes that are non-neutralizing rather than neutralizing, targeting each of these epitopes with vaccine constructs presents difficult challenges.

Antibodies to variable regions of gp120, such as V1, V2 and V3, have long been considered irrelevant to vaccine design. However, there are conserved features in the stem of the V1/V2 loop and in the V3 loop that have crucial functions in virus infectivity and explain how antibodies to these regions can be crossreactive. These conserved elements within the variable regions might therefore be relevant targets for vaccines.

HIV-1 strains exist that are not neutralized by monoclonal antibodies but are neutralized by pooled sera from HIV-1⁺ individuals. This indicates that there might be neutralizing epitopes that have not yet been identified.

Present vaccine protocols induce antibodies to many epitopes rather than focusing the immune response on epitopes that will induce protective antibodies. Given that several neutralizing epitopes in gp120 and gp41 have been identified, it might be advantageous to direct the antibody response to these protective epitopes.

It is highly unlikely that a single construct will protect against all subtypes of HIV-1. Given the continuing evolution of the virus and the spread of subtypes throughout the world, the question is how to choose which strains, and how many, need to be represented in a vaccine to give maximum protection.

During the past 20 years, the pendulum of opinion in the HIV-1 vaccine field has swung between two extremes, initially favouring the induction of antibodies only, and subsequently favouring the induction of cell-mediated immune responses only. At present, the consensus seems to be that induction of both humoral and cellular immunity by an HIV-1 vaccine will be required to achieve maximum protection. One obstacle to the development of an effective HIV-1 vaccine has been the difficulty in inducing broadly reactive, potent antibodies with protective functions. Defining epitopes and designing immunogens that will induce these antibodies is one of the main challenges that now confronts the HIV-1 vaccine field.

Interaction of cutaneous lymphoma cells with reactive T cells and dendritic cells: implications for dendritic cell-based immunotherapy

BACKGROUND

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of skin neoplasms that originate from T lymphocytes. An anti-CTCL T-cell immunity has been described but seems to be inefficient to clear CTCL cells. It is not known whether cutaneous dendritic cells (DCs) perpetuate the proliferation of the malignant CTCL cell clone or play a role in the control of this usually slowly progressing disease.

OBJECTIVES

To characterize CTCL cell properties in the control of anti-CTCL T cells and to pave the way for a DC-based immunotherapy for CTCL.

METHODS

We studied the interaction of a CTCL cell line with DCs and with allogeneic T cells.

RESULTS

We found an antigen non-specific capacity of viable but not apoptotic CTCL cells to hamper CD4+ and CD8+ T-cell proliferation in a dose-dependent manner, indicating a suppressive potential of CTCL cells. Both viable and apoptotic CTCL cells were phagocytosed by immature DCs but only apoptotic CTCL cells induced an upregulation of DC maturation markers to a degree which enabled classification of these DCs as semimature. CTCL cells did not respond with proliferation when encountering allogeneic, mature DCs either loaded with CTCL cell material or unloaded, indicating a role for DCs in the induction of anti-CTCL T-cell immunity rather than in perturbation of clonal proliferation. For the loading of DCs with CTCL material lysate seems to be optimal as apoptotic cells were not phagocytosed extensively and necrotic CTCL material induced a partial cellular toxicity in DCs. DCs loaded with CTCL material were cryopreservable without significant loss of DC viability, surface marker expression or allostimulatory activity.

CONCLUSIONS

Together, these data argue in favour for a DC-based immunotherapy for CTCL patients and provide an experimental protocol for preparing CTCL cell-loaded DCs.

Selective immmunotherapy through extracorporeal photochemotherapy: yesterday, today, and tomorrow

ECP's extensive clinical record, as well as a considerable improvement in the understanding of the mechanism that underlies its efficacy, opens potential novel strategies for the treatment of cancer, GVHD, transplant rejection, and autoimmunity. The low side effect profile of this therapy has made it a more attractive treatment consideration than current conventional chemotherapeutic and immunosuppressive medications. As the mechanism of action of ECP is more fully elucidated and clinical studies are completed, the role of ECP in modern therapeutics of CTCL and other malignancies, as well as in the treatment of other T-cell mediated diseases, will be become clearer.

Augmentation of monocyte interleukin-8 production by psoralen/UVA-treated CD4+ T cells

Treatment of cells with psoralen and ultraviolet A light (UVA) modulates their cytokine production. As extracorporeal photochemotherapy has been reported to induce cytokine production by monocytes, we quantified interleukin-8 (IL-8), a representative chemokine produced by monocytes, in culture supernatants from human peripheral blood mononuclear cells (PBMC) treated with 8-methoxypsoralen (8-MOP) and UVA. Lipopolysaccharide stimulated IL-8 production in 8-MOP-phototreated PBMC more efficiently than those untreated or treated with 8-MOP or UVA. More interestingly, when cultured with T-cell-stimulating anti-CD3 and anti-CD28 antibodies, 8-MOP/UVA-treated PBMC produced enhanced amounts of IL-8 with an increased level of IL-8 mRNA expression. Depletion of CD4 but not CD8 T cells from PBMC abrogated this augmented IL-8 elaboration, and CD4 T cells per se secreted no substantial amount of IL-8 even upon CD3/CD28 stimulation. Thus, 8-MOP/UVA-treated CD4 T cells stimulated monocytes to secrete IL-8. The IL-8 overproduction was induced by direct contact of monocytes with 8-MOP/UVA-treated CD4 T cells but not by cytokines from the treated CD4 T cells. These findings imply that in extracorporeal photochemotherapy, monocytes effectively produce IL-8 by cell-to-cell contact with 8-MOP/UVA-treated malignant CD4 T cells. The augmentation of monocyte cytokine/chemokine production by 8-MOP/UVA may be one of the mechanisms underlying the therapeutic efficacy of extracorporeal photochemotherapy.

Transimmunization and the evolution of extracorporeal photochemotherapy

We are now aware that extracorporeal photopheresis (ECP) - in which a patient's leukocytes are isolated, passed through an ultrathin clear plastic plate, and exposed to 8-methoxypsoralen (8-MOP) and ultraviolet A light prior to reinfusion - is a simple and efficient dendritic cell (DC) therapy and the first FDA approved selective immunotherapy for cancer. DCs, as the most effective antigen presenting cells (APCs), are central to many ongoing efforts to stimulate immune responses to cancer cells. Moreover, ECP has not only demonstrated efficacy in the treatment of a T cell malignancy--namely cutaneous T-cell lymphoma (CTCL)--but also in treatment of oligoclonal T-cell-mediated diseases such as graft-versus-host-disease (GVHD) and organ transplant rejection. Recent advances in the understanding of DC/T-cell interactions provide insight into how ECP-induced DCs (EI-DCs) can be utilized to stimulate specific T-cell (i.e. anti-tumor) responses, or down-regulate a pre-existing potent T-cell response. The mechanism of this apparent paradox of EI-DC functionality is likely dependent on several fundamental principles: (1) the status of existing in vivo T-cell reactions, (2) the temporal stage of EI-DC differentiation, and (3) the affinity of the available repertoire of T-cell receptors (TCRs) for the antigen(s) in question. Further investigation into DC/T-cell interactions will help to shape the future of ECP and the ability to optimize this therapy for the desired immune effect. To this end, we are developing and testing Transimmunization to replace conventional ECP.

Efficient tumor antigen loading of dendritic antigen presenting cells by transimmunization

Extracorporeal photochemotherapy (ECP), or photopheresis, was originally introduced for the management of patients with cutaneous T cell lymphoma (CTCL). Today, ECP remains the only FDA approved tumor-targeting selective immunotherapy for the treatment of any cancer. The key cellular events permitting ECP-induced anti-tumor immunity against CTCL are the induction of apoptotis in the malignant T cells, and the induction of monocyte-to-dendritic cell (DC) differentiation. In standard ECP, leukocytes extracorporeally exposed to psoralen and ultraviolet A light (UVA) are circulated back to the patient. However, recent findings suggest that co-incubation of these cells prior to re-infusion allows for more efficient phagocytosis and processing of the apoptotic malignant T cells by the newly formed DCs. Moreover, such a co-incubation step permits the direct external manipulation of this system and the design of strategies to augment the production of tumor-loaded DCs. These considerations have led to the development of Transimmunization, so named because it causes transfer of tumor antigens to newly formed dendritic cells capable of initiating immunization against the tumor cells, as the replacement technology for ECP. We will review the scientific understanding of ECP and explain how this can lead a more efficient, potentially broadly applicable, immunotherapy for cancer.