Definition of TCR epitopes for CTL-mediated attack of 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.

The immunopathogenesis and immunotherapy of cutaneous T cell lymphoma: Pathways and targets for immune restoration and tumor eradication

Cutaneous T cell lymphomas (CTCLs) are malignancies of skin-trafficking T cells. Patients with advanced CTCL manifest immune dysfunction that predisposes to infection and suppresses the antitumor immune response. Therapies that stimulate immunity have produced superior progression-free survival compared with conventional chemotherapy, reinforcing the importance of addressing the immune deficient state in the care of patients with CTCL. Recent research has better defined the pathogenesis of these immune deficits, explaining the mechanisms of disease progression and revealing potential therapeutic targets. The features of the malignant cell in mycosis fungoides and Sézary syndrome are now significantly better understood, including the T helper 2 cell phenotype, regulatory T cell cytokine production, immune checkpoint molecule expression, chemokine receptors, and interactions with the microenvironment. The updated model of CTCL immunopathogenesis provides understanding into clinical progression and therapeutic response.

Role of bexarotene in the treatment of cutaneous T-cell lymphoma: the clinical and immunological sides

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of lymphoid neoplasms. The incidence of CTCLs has risen over the last three decades. The most common CTCLs are mycosis fungoides and Sèzary syndrome. Therapies for CTCLs are various and range from skin-directed therapy to chemotherapy. Retinoids have been used in CTCL treatment since the 1980s with good results. Bexarotene is the first retinoid approved by the US FDA for CTCL therapy. Since then, numerous experiences of both its efficacy and mechanism of action have been reported. The aim of this paper is to review bexarotene action on CTCLs, as well as to highlight its immunological targets.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

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.

Down-modulation of CXCR3 surface expression and function in CD8+ T cells from cutaneous T cell lymphoma patients

Viruses can escape destruction by the immune system by exploitation of the chemokine-chemokine receptor system. It is less established whether human cancers can adopt similar strategies to evade immunologic control. In this study, we show that advanced cutaneous T cell lymphoma (CTCL) is associated with selective and efficient inactivation of CXCR3-dependent T cell migration. Our studies demonstrate that this alteration is at least in part due to CXCR3 down-regulation in vivo by elevated serum levels of CXCR3 ligands. The T cell population most affected by this down-regulatory mechanism are CD8+ cytotoxic effector T cells. In CTCL patients, cytotoxic effector T cells have strongly reduced surface CXCR3 expression, accumulate in peripheral blood, but are virtually absent from CTCL tumor lesions, indicating an inability to extravasate into lymphoma tissue. CTCL-associated inactivation of effector cell recruitment may be a paradigmatic example of a new type of immune escape mechanisms shielding the neoplasm from a tumoricidal attack.

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.

Rapid construction of a dendritic cell vaccine through physical perturbation and apoptotic malignant T cell loading

We have demonstrated that adherence and release of monocytes from a plastic surface drives their differentiation into immature dendritic cells (DC,) that can mature further during overnight incubation in the presence of apoptotic malignant T cells. Based on these results, we sought to develop a clinically, practical, rapid means for producing DC loaded with malignant cells. A leukapheresis harvest containing the clonal, leukemic expansion of malignant CD4+ T cells was obtained from the blood of patients with cutaneous T cell lymphoma (CTCL). CTCL cells were purified with a CD3-magnetic bead column where CD3 engagement rendered the malignant T cells apoptotic. The monocyte fraction was simultaneously activated by column passage, re-added to the apoptotic CTCL cells and co-cultured overnight. CTCL cell apoptosis, DC differentiation and apoptotic malignant T cell ingestion were measured by immunostaining. The results demonstrate that as monocytes passed through the column matrix, they became activated and differentiated into semi-mature DC expressing significantly increased levels of class II, CD83 and CD86 (markers associated with maturing DC) and reduced expression of the monocyte markers CD14 and CD36. Apoptotic malignant T cells were avidly engulfed by the phagocytic transitioning DC. The addition of supportive cytokines further enhanced the number of DC that contained apoptotic malignant T cells. Functional studies confirmed that column passaged DC increased class II expression as shown by significantly enhanced stimulation in mixed leukocyte culture compared to control monocytes. In addition, DC loaded with apoptotic CTCL cells stimulated an increase in the percentage and absolute number of CD8 T cells compared to co-cultivation with non-loaded DC. After CD8 T cells were stimulated by DC loaded with malignant cells, they mediated increased apoptosis of residual CTCL cells and TNF-alpha secretion indicating development of enhanced cytolytic function. We report a simple one-step procedure where maturing DC containing apoptotic malignant T cells can be prepared rapidly for potential use in vaccine immunotherapy. Ready access to both the DC and apoptotic cells provided by this system will allow extension to other malignancies through the addition of a variety of apoptotic tumor cells and maturation stimuli.

Immunopathogenesis and therapy of cutaneous T cell lymphoma

Cutaneous T cell lymphomas (CTCLs) are a heterogenous group of lymphoproliferative disorders caused by clonally derived, skin-invasive T cells. Mycosis fungoides (MF) and Sezary syndrome (SS) are the most common types of CTCLs and are characterized by malignant CD4(+)/CLA(+)/CCR4(+) T cells that also lack the usual T cell surface markers CD7 and/or CD26. As MF/SS advances, the clonal dominance of the malignant cells results in the expression of predominantly Th2 cytokines, progressive immune dysregulation in patients, and further tumor cell growth. This review summarizes recent insights into the pathogenesis and immunobiology of MF/SS and how these have shaped current therapeutic approaches, in particular the growing emphasis on enhancement of host antitumor immune responses as the key to successful therapy.

Evidence for Restricted Vβ Usage in the Leukemic Phase of Cutaneous T Cell Lymphoma

Antibodies directed against the beta chain of the T cell receptor (anti-Vbeta antibodies) are useful to identify the Vbeta repertoire of T cells in various diseases and to quantify numbers of Vbeta-bearing T cells. The goals of this study were to identify Vbeta+ cases of leukemic phase cutaneous T cell lymphoma (CTCL) and to compare the percentage of positive calls with other measures of blood tumor burden, i.e., lymphocyte subsets with a CD4+CD7- and CD4+CD26- phenotype and Sezary cell counts. Thirty-three of 49 (67%) cases of leukemic CTCL reacted with an anti-Vbeta antibody. When combined with reports from the literature, the frequency of Vbeta5 (probably Vbeta5.1) usage was relatively high when compared with Vbeta2 that is also frequently expressed by normal CD4+ T cells. The percentage of Vbeta+ cells correlated to the percentage of CD4+CD7- and CD4+CD26- cells for cases in which the neoplastic cells were deficient in expression of CD7 and CD26, respectively, but not the Sezary cell count. We hypothesize that the increased Vbeta5.1 usage in CTCL may be the result of depletion of Vbeta2 and other Vbeta-bearing T cells by staphylococcal superantigens prior to neoplastic transformation, resulting in a relative increase in the frequency of Vbeta5.1 usage in CTCL.

Cutaneous T-cell lymphoma: malignant proliferation of T-regulatory cells

Studies in an in vitro model of cutaneous T-cell lymphoma (CTCL) demonstrated that CTCL cell proliferation is stimulated by direct contact with autologous, immature dendritic cells (DCs), suggesting that CD4(+) CTCL cell division is driven by antigens presented by DC major histocompatibility complex (MHC) class 2. We now report that the T-cell receptor (TCR) of the CD4(+) CTCL cells is triggered after interaction with DCs loaded with apoptotic CTCL cells, as shown by reduced membrane expression of CD3 and the TCR, up-regulation of cytotoxic T lymphocyte antigen-4 (CTLA-4), and calcium mobilization. CTCL cells adopt a T-regulatory (Treg) phenotype expressing CD25/CTLA-4 and FoxP3 and secreting interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta). Treg CTCL cells suppress normal T-cell antigen-driven secretion of IL-2 and interferon-gamma (IFN-gamma). Blocking DC MHC class 2 expression or transport inhibited CTCL cell adoption of a Treg phenotype. Allogeneic CTCL cells or normal CD4 T cells served as sources of apoptotic material for CTCL cell conversion to a Treg phenotype. Conversion of CTCL cells to Treg cells may explain the anergic, immunosuppressive nature of the malignancy.