Generation of Epstein-Barr virus-specific cytotoxic T lymphocytes resistant to the immunosuppressive drug tacrolimus (FK506)

Generating CTLs against the subdominant EBV LMP antigens by transient expression of an A20 inhibitor with EBV LMP proteins in human DCs

Epstein-Barr virus (EBV) infection leads to Hodgkin’s disease (HD) in some immunocompetent hosts. The malignant Reed-Sternberg cells of HD only express a limited array of subdominant EBV antigens to evade preexisting immune responses to EBV. The EBV-encoded latent membrane proteins (LMP1 and LMP2), which are expressed by HD and various EBV-associated malignancies, have been proposed as a potential target for CTL-based therapy. However, the precursor frequency for LMP-specific CTL is generally low in healthy EBV-infected hosts, and immunotherapy based on these antigens is often compromised by the poor immunogenicity and the oncogenic potential. In the present study, we report that transitively expressing an inhibitor of A20, a key negative regulator of inflammatory signaling pathways, together with the LMP antigens (truncated LMP1 and full-length LMP2) greatly enhances maturation and cytokine production of human (h) monocyte-derived dendritic cells (DCs). As a consequence, LMP1/2-expressed, A20-silenced hDCs have an enhanced potency to prime LMP-specific T cell response. When the in vitro primed T cells are adoptively transferred into tumor-xenografted, severe combined immunodeficient (SCID) mice, some of the xenografted tumors approach complete regression. Thus, the study may provide an available resource of LMP-specific T cells for T cell immunotherapy.

T-cell therapies for Epstein-Barr virus-associated lymphomas

Epstein-Barr virus (EBV)-associated lymphomas represent a broad spectrum of diseases and can be characterized by their pattern of viral latency. These pathologies display the importance of healthy T cell-mediated control of the EBV-infected B cells. Burkitt's lymphoma is the least immunogenic and has a type I latency pattern. Hodgkin's and a variety of non-Hodgkin's lymphomas exhibit antigens of type II latency. Posttransplant lymphoproliferative disease in the solid organ and hematopoietic stem cell transplant setting as well as lymphomas arising in primary immunodeficiency patients are tumors with type III latency. This last group expresses all 9 latent proteins and is the most immunogenic. T-cell approaches including donor lymphocyte infusions and the adoptive transfer of EBV-specific cytotoxic T lymphocytes can be used to treat these diseases. The authors describe the biology of these EBV-associated lymphomas and review the methodology and outcomes of existing T cell-based therapies as well as strategies to improve their efficacy.

Strategies to harness immunity against infectious pathogens after haploidentical stem cell transplantation

Viral and fungal infections account for significant morbidity and mortality, particularly in pediatric patients with profound immune suppression resulting from allogeneic hematopoietic stem cell transplantation (HSCT). Therapies with anti-viral and anti-fungal drugs are often associated with significant toxicity, are of limited efficacy and can induce drug resistance. One innovative approach to prevent and/or treat viral and fungal infections involves the adoptive transfer of in vitro-expanded or in vitro-generated pathogen-specific T cells. This review summarizes the clinical trials that have been run to date with virus- and fungus-specific T cells, with special emphasis on the clinical context of haploidentical HSCT for pediatric malignancies. It will also discuss initiatives and strategies to overcome the hurdles associated with time-consuming and complex GMP-grade laboratory procedures required to generate pathogen-specific T cells.

Genetic modification of T cells

Adoptively transferred T cells have shown activity in treating viral infections after hemopoietic transplantation and anti-tumor activity against some malignancies such as melanoma and lymphoma. Current research focuses on defining the optimum type of cell for transfer to improve persistence and genetically modifying infused T cells to augment function, overcome tumor evasion strategies and allow ablation should adverse effects occur.

Immunotherapy against EBV-lymphoma in recipients of HSCT

Epstein-Barr virus (EBV)-associated lymphoproliferations represent life-threatening complications of hematopoietic stem cell transplantation. In the last decade, immunological therapeutic strategies that allow us to selectively abrogate the origin of lymphoproliferation, namely B-cell compartment or EBV antigen-expressing tumor cells, have significantly reduced treatment-related toxicity while maintaining equal or superior efficacy. A further implementation is the possibility of preventing disease occurrence by delivering immunotherapy in the presymptomatic phase, on the basis of EBV-DNA blood levels. Despite the excellent results, T-cell therapy with EBV-specific cytotoxic T-lymphocytes has but a marginal role in the treatment of these forms. Promising implementations are underway, including logistic solutions to extend T-cell therapy beyond academic centers, delineation of strategies aimed at simplifying/shortening production and targeting immune evasion mechanisms exerted by tumor cells.

Ex vivo gene transfer for improved adoptive immunotherapy of cancer

Adoptive immunotherapy is an appealing approach to cancer treatment, with the potential for more precise targeting and reduced toxicity. While early clinical trial data using adoptive T cells against post-transplant virus-associated hematologic malignancies, lymphoma and melanoma have been promising, treating other solid tumors has proven to be more challenging. Adoptive lymphocytes have been genetically modified in many ways to improve activity and circumvent tumor evasion, including transfer of transgenic T-cell receptors and chimeric antigen receptors to redirect T cell and natural killer cell antigen specificity. Gene transfer may also allow expression of homeostatic cytokines or their receptors to overcome the lack of stimulatory signals or expression of dominant-negative receptors for inhibitory cytokines to compensate for an immunosuppressive tumor milieu. In addition, suicide genes can install a 'safety switch' on adoptively transferred cells to allow ablation if necessary. Although further refinement and validation are necessary, these genetic modification strategies offer hope for significant improvements in cancer immunotherapy.

Immunotherapy for EBV-associated malignancies

Since 1995 to date, more than 250 patients with EBV-related diseases received virus-specific CTL. Cell therapy proved to be safe and effective, and achieved some complete remissions also in patients who failed all previous standard treatments. The first clinical results with EBV-specific CTL were obtained for both prophylaxis and treatment of post-transplant lymphoproliferative disease arising in stem cell transplant or solid organ transplant recipients. Based on such encouraging results, the same approach was then extended to other EBV-related diseases, namely Hodgkin's lymphoma, nasopharyngeal carcinoma, and chronic active infection. Nowadays, the modification of the CTL generation protocols and the introduction of new specificities into EBV-specific CTL lines by chimeric antigen receptor transfer allow targeting other viral infections and also non-EBV related malignancies. Aim of this review is to summarize clinical results obtained thus far in adoptive cell therapy approaches with EBV-specific CTL. Moreover, by analyzing ongoing clinical trials, we also provide some insights on the potential future of a successful and paradigmatic history.

White paper on adoptive cell therapy for cancer with tumor-infiltrating lymphocytes: a report of the CTEP subcommittee on adoptive cell therapy

Adoptive T-cell therapy (ACT) using expanded autologous tumor-infiltrating lymphocytes (TIL) and tumor antigen-specific T cell expanded from peripheral blood are complex but powerful immunotherapies directed against metastatic melanoma. A number of nonrandomized clinical trials using TIL combined with high-dose interleukin-2 (IL-2) have consistently found clinical response rates of 50% or more in metastatic melanoma patients accompanied by long progression-free survival. Recent studies have also established practical methods for the expansion of TIL from melanoma tumors with high success rates. These results have set the stage for randomized phase II/III clinical trials to determine whether ACT provides benefit in stage IV melanoma. Here, we provide an overview of the current state-of-the art in T-cell-based therapies for melanoma focusing on ACT using expanded TIL and address some of the key unanswered biological and clinical questions in the field. Different phase II/III randomized clinical trial scenarios comparing the efficacy of TIL therapy to high-dose IL-2 alone are described. Finally, we provide a roadmap describing the critical steps required to test TIL therapy in a randomized multicenter setting. We suggest an approach using centralized cell expansion facilities that will receive specimens and ship expanded TIL infusion products to participating centers to ensure maximal yield and product consistency. If successful, this approach will definitively answer the question of whether ACT can enter mainstream treatment for cancer.

Post-transplantation lymphoproliferative disorders: diagnosis, prognosis, and current approaches to therapy

Post-transplantation lymphoproliferative disorders (PTLD) are a heterogenous group of abnormal lymphoid proliferations that occur after solid organ transplant (SOT) or hematopoietic transplantation. PTLDs consist of a disease spectrum ranging from hyperplasia to aggressive lymphomas with 60-70% being Epstein-Barr virus positive. The majority of cases are B-cell, although 10-15% are of T-cell origin or rarely Hodgkin lymphoma. Recent SOT series suggest PTLD occurs at a median of 36-40 months after transplant. Clinically, extra-nodal disease is common (up to 75-85%) including CNS involvement, which is seen in 10-15% of all cases. Since the first report over 40 years ago, PTLD has remained one of the most morbid complications associated with SOT. However, recent data suggests improved survival in the modern era, especially with the integration of early rituximab-based therapy. These studies utilized first line rituximab (+/- chemotherapy) together with reduced immune suppression (RI) for monomorphic and polymorphic PTLD. It will be critical in future studies to determine which PTLDs are most amenable to initial therapy with RI alone, versus RI/rituximab, versus RI/rituximab/chemotherapy. Additionally, novel therapeutics, such as adoptive immunotherapy, should continue to be explored.

Immune defence against EBV and EBV-associated disease

Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus widespread in the human population and normally contained as an asymptomatic infection by T cell surveillance, nevertheless causes infectious mononucleosis and is strongly linked to several types of human cancer. Here we describe new findings on the range of cellular immune responses induced by EBV infection, on viral strategies to evade those responses and on the links between HLA gene loci and EBV-induced disease. The success of adoptive T cell therapy for EBV-driven post-transplant lymphoproliferative disease is stimulating efforts to target other EBV-associated tumours by immunotherapeutic means, and has reawakened interest in the ultimate intervention strategy, a prophylactic EBV vaccine.

Immunotherapeutic options for Epstein-Barr virus-associated lymphoproliferative disease following transplantation

Epstein-Barr virus-associated lymphoproliferative diseases (EBV-LPD) after hematopoietic stem cell transplantation or solid-organ transplantation remain a serious and potentially life-threatening complication. In the last decade, outcomes for EBV-LPD have significantly improved. Key to this success was the development of early detection methods, such as serial measurements of EBV-DNA load in the peripheral blood of transplant recipients. Immunotherapeutic interventions for EBV-LPD include reduction of immunosuppression, CD20 monoclonal antibodies (rituximab) as monotherapy or in conjunction with chemotherapy, and adoptive immunotherapy with EBV-specific T cells. Pre-emptive immunotherapeutic interventions can prevent the development of EBV-LPD. As monotherapy, immunotherapy is effective in inducing remissions of EBV-LPD with low-risk features. For high-risk disease, combining immunotherapy with conventional therapies has led to superior outcomes. Current challenges consist of risk stratifying patients so that patients receive the most efficacious therapy without suffering from unwanted side effects.

Using Epstein-Barr viral load assays to diagnose, monitor, and prevent posttransplant lymphoproliferative disorder

Epstein-Barr virus (EBV) DNA measurement is being incorporated into routine medical practice to help diagnose, monitor, and predict posttransplant lymphoproliferative disorder (PTLD) in immunocompromised graft recipients. PTLD is an aggressive neoplasm that almost always harbors EBV DNA within the neoplastic lymphocytes, and it is often fatal if not recognized and treated promptly. Validated protocols, commercial reagents, and automated instruments facilitate implementation of EBV load assays by real-time PCR. When applied to either whole blood or plasma, EBV DNA levels reflect clinical status with respect to EBV-related neoplasia. While many healthy transplant recipients have low viral loads, high EBV loads are strongly associated with current or impending PTLD. Complementary laboratory assays as well as histopathologic examination of lesional tissue help in interpreting modest elevations in viral load. Circulating EBV levels in serial samples reflect changes in tumor burden and represent an effective, noninvasive tool for monitoring the efficacy of therapy. In high-risk patients, serial testing permits early clinical intervention to prevent progression toward frank PTLD. Restoring T cell immunity against EBV is a major strategy for overcoming PTLD, and novel EBV-directed therapies are being explored to thwart virus-driven neoplasia.

The interplay between Epstein-Barr virus and the immune system: a rationale for adoptive cell therapy of EBV-related disorders

The Epstein-Barr virus has evolved a plethora of strategies to evade immune system recognition and to establish latent infection in memory B cells, where the virus resides lifelong without any consequence in the majority of individuals. However, some imbalances in the equilibrium between the inherent virus transforming properties and the host immune system can lead to the development of different tumors, such as lymphoproliferative disorders, Hodgkin's lymphoma, Burkitt's lymphoma, and nasopharyngeal carcinoma. The expression of viral antigens in malignant cells makes them suitable targets for immunotherapeutic approaches, which are mainly based on the ex vivo expansion of EBV-specific T cells. Indeed, the infusion of virus-specific cytotoxic T lymphocytes has proved not only to be safe and effective, but also capable of restoring or inducing a protective anti-virus immunity, which is lacking, albeit to a different extent, in every EBV-driven malignancy. The purpose of this review is to summarize the results of adoptive immunotherapy approaches for EBV-related malignancies, with particular emphasis on the immunological and virological aspects linked to the clinical responses obtained. Data collected confirm the clinical relevance of the use of EBV-specific cytotoxic T lymphocytes in the field of adoptive immunotherapy and suggest the increasing importance of this approach also against other tumors, concurrent with the increasing knowledge of the intimate and continuous interplay between the virus and the host immune system.

Posttransplant lymphoproliferative diseases

The risk of developing cancer after solid organ transplantation (SOT) is about 5- to 10-fold greater than that of the general population. The cumulative risk of cancer rises to more than 50% at 20 years after transplant and increases with age, and so children receiving transplants are at high risk of developing a malignancy. Posttransplant lymphoproliferative disease (PTLD) is the most common cancer observed in children following SOT, accounting for half of all such malignancies. PTLD is a heterogeneous group of disorders with a wide spectrum of pathologic and clinical manifestations and is a major contributor to long-term morbidity and mortality in this population. Among children, most cases are associated with Epstein-Barr virus infection. This article reviews the pathology, immunobiology, epidemiology, and clinical aspects of PTLD, underscoring the need for ongoing systematic study of complex biologic and therapeutic questions.

Adoptive T cell therapy of cancer

Adoptive transfer of T cells specific for antigens expressed on tumor cells is an attractive strategy for producing targeted and long-lived anti-tumor activity. T cell therapies have shown activity in selected clinical applications but broader application is limited by inadequate persistence of transferred T cells and by tumor-evasion strategies. Current research focuses on defining the optimum type of cell for transfer, genetically modifying infused T cells to augment function and overcome tumor evasion strategies and modulating the host environment.

Therapy of relapsed leukemia after allogeneic hematopoietic cell transplantation with T cells specific for minor histocompatibility antigens

The adoptive transfer of donor T cells that recognize recipient minor histocompatibility antigens (mHAgs) is a potential strategy for preventing or treating leukemic relapse after allogeneic hematopoietic cell transplantation (HCT). A total of 7 patients with recurrent leukemia after major histocompatibility complex (MHC)-matched allogeneic HCT were treated with infusions of donor-derived, ex vivo-expanded CD8(+) cytotoxic T lymphocyte (CTL) clones specific for tissue-restricted recipient mHAgs. The safety of T-cell therapy, in vivo persistence of transferred CTLs, and disease response were assessed. Molecular characterization of the mHAgs recognized by CTL clones administered to 3 patients was performed to provide insight into the antileukemic activity and safety of T-cell therapy. Pulmonary toxicity of CTL infusion was seen in 3 patients, was severe in 1 patient, and correlated with the level of expression of the mHAg-encoding genes in lung tissue. Adoptively transferred CTLs persisted in the blood up to 21 days after infusion, and 5 patients achieved complete but transient remissions after therapy. The results of these studies illustrate the potential to selectively enhance graft-versus-leukemia activity by the adoptive transfer of mHAg-specific T-cell clones and the challenges for the broad application of this approach in allogeneic HCT. This study has been registered at http://clinicaltrials.gov as NCT00107354.

Immunotherapy of human cancers using gene modified T lymphocytes

Adoptive T cell therapies can produce objective clinical responses in patients with hematologic and solid malignancies. Genetic manipulation of T lymphocytes has been proposed as a means of increasing the potency and range of this anti-tumor activity. We now review how coupling expression of transgenic receptors with countermeasures against potent tumor immune evasion strategies is proving highly effective in pre-clinical models and describe how these approaches are being evaluated in human subjects.