Cellular immunotherapy for follicular lymphoma using genetically modified CD20-specific CD8+ cytotoxic T lymphocytes

CAR T-Cell Therapy Predictive Response Markers in Diffuse Large B-Cell Lymphoma and Therapeutic Options After CART19 Failure

Immunotherapy with T cells genetically modified with chimeric antigen receptors (CARs) has shown significant clinical efficacy in patients with relapsed/refractory B-cell lymphoma. Nevertheless, more than 50% of treated patients do not benefit from such therapy due to either absence of response or further relapse. Elucidation of clinical and biological features that would predict clinical response to CART19 therapy is of paramount importance and eventually may allow for selection of those patients with greater chances of response. In the last 5 years, significant clinical experience has been obtained in the treatment of diffuse large B-cell lymphoma (DLBCL) patients with CAR19 T cells, and major advances have been made on the understanding of CART19 efficacy mechanisms. In this review, we discuss clinical and tumor features associated with response to CART19 in DLBCL patients as well as the impact of biological features of the infusion CART19 product on the clinical response. Prognosis of DLBCL patients that fail CART19 is poor and therapeutic approaches with new drugs are also discussed.

A CAR RNA FISH assay to study functional and spatial heterogeneity of chimeric antigen receptor T cells in tissue

Chimeric antigen receptor (CAR) T cells are engineered cells used in cancer therapy and are studied to treat infectious diseases. Trafficking and persistence of CAR T cells is an important requirement for efficacy to target cancer. Here, we describe a CAR RNA FISH histo-cytometry platform combined with a random reaction seed image analysis algorithm to quantitate spatial distribution and in vivo functional activity of a CAR T cell population at a single cell resolution for preclinical models. In situ, CAR T cell exhibited a heterogenous effector gene expression and this was related to the distance from tumor cells, allowing a quantitative assessment of the potential in vivo effectiveness. The platform offers the potential to study immune functions of genetically engineered cells in situ with their target cells in tissues with high statistical power and thus, can serve as an important tool for preclinical assessment of CAR T cell effectiveness.

Role of Microenvironment in Non-Hodgkin Lymphoma: Understanding the Composition and Biology

Lymphoma microenvironment is a dynamic and well-orchestrated network of various immune and stromal cells that is indispensable for tumor cell survival, growth, migration, immune escape, and drug resistance. Recent progress has enhanced our knowledge of the pivotal role of microenvironment in lymphomagenesis. Understanding the characteristics, functions, and contributions of various components of the tumor niche, along with its bidirectional interactions with tumor cells, is paramount. It offers the potential to identify new therapeutic targets with the ability to restore antitumor immune surveillance and eliminate the protumoral factors contributed by the tumor niche.

A giant step forward: chimeric antigen receptor T-cell therapy for lymphoma

The combination of the immunotherapy (i.e., the use of monoclonal antibodies) and the conventional chemotherapy increases the long-term survival of patients with lymphoma. However, for patients with relapsed or treatment-resistant lymphoma, a novel treatment approach is urgently needed. Chimeric antigen receptor T (CAR-T) cells were introduced as a treatment for these patients. Based on recent clinical data, approximately 50% of patients with relapsed or refractory B-cell lymphoma achieved complete remission after receiving the CD19 CAR-T cell therapy. Moreover, clinical data revealed that some patients remained in remission for more than two years after the CAR-T cell therapy. Other than the CD19-targeted CAR-T, the novel target antigens, such as CD20, CD22, CD30, and CD37, which were greatly expressed on lymphoma cells, were studied under preclinical and clinical evaluations for use in the treatment of lymphoma. Nonetheless, the CAR-T therapy was usually associated with potentially lethal adverse effects, such as the cytokine release syndrome and the neurotoxicity. Therefore, optimizing the structure of CAR, creating new drugs, and combining CAR-T cell therapy with stem cell transplantation are potential solutions to increase the effectiveness of treatment and reduce the toxicity in patients with lymphoma after the CAR-T cell therapy.

Potential strategies against resistance to CAR T-cell therapy in haematological malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a rapidly developing method for adoptive immunotherapy of tumours in recent years. CAR T-cell therapies have demonstrated unprecedented efficacy in the treatment of patients with haematological malignancies. A 90% complete response (CR) rate has been reported in patients with advanced relapse or refractory acute lymphoblastic leukaemia, while >50% CR rates have been reported in cases of chronic lymphocytic leukaemia and partial B-cell lymphoma. Despite the high CR rates, a subset of the patients with complete remission still relapse. The mechanism of development of resistance is not clearly understood. Some patients have been reported to demonstrate antigen-positive relapse, whereas others show antigen-negative relapses. Patients who relapse following CAR T-cell therapy, have very poor prognosis and novel approaches to overcome resistance are required urgently. Herein, we have reviewed current literature and research that have investigated the strategies to overcome resistance to CAR T-cell therapy.

The long road to the first FDA-approved gene therapy: chimeric antigen receptor T cells targeting CD19

Thirty years after initial publications of the concept of a chimeric antigen receptor (CAR), the U.S. Food and Drug Administration (FDA) approved the first anti-CD19 CAR T-cell therapy. Unlike other immunotherapies, such as immune checkpoint inhibitors and bispecific antibodies, CAR T cells are unique as they are "living drugs," that is, gene-edited killer cells that can recognize and kill cancer. During these 30 years of development, the CAR construct, T-cell manufacturing process, and clinical patient management have gone through rounds of failures and successes that drove continuous improvement. Tisagenlecleucel was the first gene therapy to receive approval from the FDA for any indication. The initial approval was for relapsed or refractory (r/r) pediatric and young-adult B-cell acute lymphoblastic leukemia in August 2017 and in May 2018 for adult r/r diffuse large B-cell lymphoma. Here we review the preclinical and clinical development of what began as CART19 at the University of Pennsylvania and later developed into tisagenlecleucel.

An overview of cancer immunotherapeutic strategies

Artificially boosting body's immune response is one of the most exciting, effective and promising advancements in the treatment of cancers. Cancer immunotherapeutics consist of variety of treatment approaches such as cytokine therapy, adoptive T-cell transfer therapy, and antibodies that stimulate innate and adoptive immune responses. In addition to this, development of HPV vaccine has paved way toward the development of other cancer vaccines. Checkpoint blockade inhibitors, for example, anti-programmed cell death protein 1 and anti-cytotoxic T-lymphocyte-associated antigen-4, chimeric antigen receptor T-cell therapy and monoclonal antibodies are emerging as other major breakthroughs that are highly effective against cancer. This review addresses the current status of immunotherapeutic strategies against cancer and provides baseline data for future research.

CAR T-cells for cancer therapy

Chimeric antigen receptor (CAR) T-cells are redirected T-cells that can recognize cancer antigens in a major histocompatibility complex (MHC)-independent fashion. A typical CAR is comprised of two main functional domains: an extracellular antigen recognition domain, called a single-chain variable fragment (scFv), and an intracellular signaling domain. Based on the number of intracellular signaling molecules, CARs are categorized into four generations. CAR T-cell therapy has become a promising treatment for hematologic malignancies. However, results of its clinical trials on solid tumors have not been encouraging. Here, we described the structure of CARs and summarized the clinical trials of CD19-targeted CAR T-cells. The side effects, safety management, challenges, and future prospects of CAR T-cells for the treatment of cancer, particularly for solid tumors, were also discussed.

Optimized depletion of chimeric antigen receptor T cells in murine xenograft models of human acute myeloid leukemia

We and others previously reported potent antileukemia efficacy of CD123-redirected chimeric antigen receptor (CAR) T cells in preclinical human acute myeloid leukemia (AML) models at the cost of severe hematologic toxicity. This observation raises concern for potential myeloablation in patients with AML treated with CD123-redirected CAR T cells and mandates novel approaches for toxicity mitigation. We hypothesized that CAR T-cell depletion with optimal timing after AML eradication would preserve leukemia remission and allow subsequent hematopoietic stem cell transplantation. To test this hypothesis, we compared 3 CAR T-cell termination strategies: (1) transiently active anti-CD123 messenger RNA-electroporated CART (RNA-CART123); (2) T-cell ablation with alemtuzumab after treatment with lentivirally transduced anti-CD123-4-1BB-CD3ζ T cells (CART123); and (3) T-cell ablation with rituximab after treatment with CD20-coexpressing CART123 (CART123-CD20). All approaches led to rapid leukemia elimination in murine xenograft models of human AML. Subsequent antibody-mediated depletion of CART123 or CART123-CD20 did not impair leukemia remission. Time-course studies demonstrated that durable leukemia remission required CAR T-cell persistence for 4 weeks prior to ablation. Upon CAR T-cell termination, we further demonstrated successful hematopoietic engraftment with a normal human donor to model allogeneic stem cell rescue. Results from these studies will facilitate development of T-cell depletion strategies to augment the feasibility of CAR T-cell therapy for patients with AML.

Engineering HIV-Resistant, Anti-HIV Chimeric Antigen Receptor T Cells

The treatment or cure of HIV infection by cell and gene therapy has been a goal for decades. Recent advances in both gene editing and chimeric antigen receptor (CAR) technology have created new therapeutic possibilities for a variety of diseases. Broadly neutralizing monoclonal antibodies (bNAbs) with specificity for the HIV envelope glycoprotein provide a promising means of targeting HIV-infected cells. Here we show that primary human T cells engineered to express anti-HIV CARs based on bNAbs (HIVCAR) show specific activation and killing of HIV-infected versus uninfected cells in the absence of HIV replication. We also show that homology-directed recombination of the HIVCAR gene expression cassette into the CCR5 locus enhances suppression of replicating virus compared with HIVCAR expression alone. This work demonstrates that HIV immunotherapy utilizing potent bNAb-based single-chain variable fragments fused to second-generation CAR signaling domains, delivered directly into the CCR5 locus of T cells by homology-directed gene editing, is feasible and effective. This strategy has the potential to target HIV-infected cells in HIV-infected individuals, which might help in the effort to cure HIV.

CAR-modified T-cell therapy for cancer: an updated review

The use of chimeric antigen receptor (CAR)-modified T cells is a promising approach for cancer immunotherapy. These genetically modified receptors contain an antigen-binding moiety, a hinge region, a transmembrane domain, and an intracellular costimulatory domain resulting in T-cell activation subsequent to antigen binding. Optimal tumor removal through CAR-modified T cells requires suitable target antigen selection, co-stimulatory signaling domain, and the ability of CAR T cells to traffic, persist, and retain antitumor function after adoptive transfer. There are several elements which can improve antitumor function of CAR T cells, including signaling, conditioning chemotherapy and irradiation, tumor burden of the disease, T-cell phenotype, and supplementary cytokine usage. This review outlines four generations of CAR. The pre-clinical and clinical studies showed that this technique has a great potential for treatment of solid and hematological malignancies. The main purpose of the current review is to focus on the pre-clinical and clinical developments of CAR-based immunotherapy.

Efficient modification of CCR5 in primary human hematopoietic cells using a megaTAL nuclease and AAV donor template

Genetic mutations or engineered nucleases that disrupt the HIV co-receptor CCR5 block HIV infection of CD4(+) T cells. These findings have motivated the engineering of CCR5-specific nucleases for application as HIV therapies. The efficacy of this approach relies on efficient biallelic disruption of CCR5, and the ability to efficiently target sequences that confer HIV resistance to the CCR5 locus has the potential to further improve clinical outcomes. We used RNA-based nuclease expression paired with adeno-associated virus (AAV)-mediated delivery of a CCR5-targeting donor template to achieve highly efficient targeted recombination in primary human T cells. This method consistently achieved 8 to 60% rates of homology-directed recombination into the CCR5 locus in T cells, with over 80% of cells modified with an MND-GFP expression cassette exhibiting biallelic modification. MND-GFP-modified T cells maintained a diverse repertoire and engrafted in immune-deficient mice as efficiently as unmodified cells. Using this method, we integrated sequences coding chimeric antigen receptors (CARs) into the CCR5 locus, and the resulting targeted CAR T cells exhibited antitumor or anti-HIV activity. Alternatively, we introduced the C46 HIV fusion inhibitor, generating T cell populations with high rates of biallelic CCR5 disruption paired with potential protection from HIV with CXCR4 co-receptor tropism. Finally, this protocol was applied to adult human mobilized CD34(+) cells, resulting in 15 to 20% homologous gene targeting. Our results demonstrate that high-efficiency targeted integration is feasible in primary human hematopoietic cells and highlight the potential of gene editing to engineer T cell products with myriad functional properties.

Strategies to genetically engineer T cells for cancer immunotherapy

Immunotherapy is one of the most promising and innovative approaches to treat cancer, viral infections, and other immune-modulated diseases. Adoptive immunotherapy using gene-modified T cells is an exciting and rapidly evolving field. Exploiting knowledge of basic T cell biology and immune cell receptor function has fostered innovative approaches to modify immune cell function. Highly translatable clinical technologies have been developed to redirect T cell specificity by introducing designed receptors. The ability to engineer T cells to manifest desired phenotypes and functions is now a thrilling reality. In this review, we focus on outlining different varieties of genetically engineered T cells, their respective advantages and disadvantages as tools for immunotherapy, and their promise and drawbacks in the clinic.

Construction of Anti-CD20 Single-Chain Antibody-CD28-CD137-TCRζ Recombinant Genetic Modified T Cells and its Treatment Effect on B Cell Lymphoma

Background

Immunotherapy has been explored as a new therapy for B cell lymphoma, which is a non-Hodgkin’s lymphoma. Because CD20 is a B lymphocyte-specific marker, anti-CD20 single chain-tagged T lymphocytes have already begun to be experimentally used in B cell lymphoma treatment, but its use is still limited because of its unspecific targeting. T cells transfected with CD28 and CD137 can significantly improve the ability of cytokines secretion and anti-tumor effect, as well as extending T cell survival time and improving their proliferation ability.

Material/Methods

Genes containing anti-CD20-CD28-CD137-TCRζ were constructed. After cloning and sequencing, the plasmid was constructed and packaged by lentivirus. It was transfected to the peripheral blood T lymphocyte after identification transfection to induce the fusion protein expression. The cells were incubated with Raji cells and the LDH test was performed to detect the cytotoxic effect of CAR-T cells; the tumor volume and survival rate were measured to observe its inhibitory effect on B cell lymphoma in nude mice.

Results

Gene with anti-CD20-CD28-CD137-TCRζ was successfully constructed and transfected to the T cell surface. LDH assay revealed that CAR-T cells can kill the Raji cells with a killing rate of 32.89±6.26%. It can significantly inhibit B cell lymphoma growth in nude mice.

Conclusions

T lymphocytes transfected with anti-CD20-CD28-CD137-TCRζ fusion gene can kill B cell lymphoma, which could provide a new strategy for tumor treatment.

Adoptive immunotherapy for cancer

Recent clinical success has underscored the potential for immunotherapy based on the adoptive cell transfer (ACT) of engineered T lymphocytes to mediate dramatic, potent, and durable clinical responses. This success has led to the broader evaluation of engineered T-lymphocyte-based adoptive cell therapy to treat a broad range of malignancies. In this review, we summarize concepts, successes, and challenges for the broader development of this promising field, focusing principally on lessons gleaned from immunological principles and clinical thought. We present ACT in the context of integrating T-cell and tumor biology and the broader systemic immune response.

Design and development of therapies using chimeric antigen receptor-expressing T cells

Investigators developed chimeric antigen receptors (CARs) for expression on T cells more than 25 years ago. When the CAR is derived from an antibody, the resultant cell should combine the desirable targeting features of an antibody (e.g. lack of requirement for major histocompatibility complex recognition, ability to recognize non-protein antigens) with the persistence, trafficking, and effector functions of a T cell. This article describes how the past two decades have seen a crescendo of research which has now begun to translate these potential benefits into effective treatments for patients with cancer. We describe the basic design of CARs, describe how antigenic targets are selected, and the initial clinical experience with CAR-T cells. Our review then describes our own and other investigators' work aimed at improving the function of CARs and reviews the clinical studies in hematological and solid malignancies that are beginning to exploit these approaches. Finally, we show the value of adding additional engineering features to CAR-T cells, irrespective of their target, to render them better suited to function in the tumor environment, and discuss how the safety of these heavily modified cells may be maintained.

Engineered T cells for cancer treatment

Adoptively transferred T cells have the capacity to traffic to distant tumor sites, infiltrate fibrotic tissue and kill antigen-expressing tumor cells. Various groups have investigated different genetic engineering strategies designed to enhance tumor specificity, increase T cell potency, improve proliferation, persistence or migratory capacity and increase safety. This review focuses on recent developments in T cell engineering, discusses the clinical application of these engineered cell products and outlines future prospects for this therapeutic modality.

Developing strategies in the immunotherapy of leukemias

BACKGROUND

In the current treatment paradigms for leukemias, hematopoietic stem cell transplant (HSCT) is considered the best option with a curative potential although more often than not it simply delays disease progression. Advances are needed, both in current therapies and in the development of new strategies. Partly from studying the nuances of the curative potential of stem cell transplant, we have come to appreciate the relevance of the immune response and the potential of immunotherapy.

METHODS

This review article summarizes the recent advances in the field of immunology and immunotherapy for leukemia.

RESULTS

In passive immunotherapy, recent progress in chimeric T-cell antigen receptor technology has been encouraging. In active immunotherapy, a cancer vaccine may potentially enhance HSCT. An overview of various clinical studies of peptide vaccination strategies focusing on molecular targets such as the Wilms' tumor gene 1 (WT1), proteinase 3 (PR3), and receptor for hyaluronan acid-mediated motility (RHAMM) is provided. Cell-based vaccination strategies are also briefly explored.

CONCLUSIONS

The immune system clearly has the capacity to recognize and react to leukemic cells, and recent evidence directs our attention to the importance of mounting inflammatory and CD4 T-cell responses to complement and support the cytotoxic activity elicited by peptide vaccines.

Cellular composition of the tumor microenvironment

In addition to malignant cells, the tumor microenvironment also includes nonmalignant cells, secreted proteins, and blood vessels that surround and support the growth of the tumor. Interactions between the various components of the tumor microenvironment are significant; tumor cells can change the nature of the microenvironment, and conversely, the microenvironment can affect how a tumor grows and spreads. The structure and composition of the tumor microenvironment varies among different types of cancers and between patients. This paper focuses on the composition and function of the tumor microenvironment in hematologic malignancies with a specific focus on B-cell lymphomas.

Immunotherapy of malignant disease using chimeric antigen receptor engrafted T cells

Chimeric antigen receptor- (CAR-) based immunotherapy has been under development for almost 25 years, over which period it has progressed from a new but cumbersome technology to an emerging therapeutic modality for malignant disease. The approach involves the genetic engineering of fusion receptors (CARs) that couple the HLA-independent binding of cell surface target molecules to the delivery of a tailored activating signal to host immune cells. Engineered CARs are delivered most commonly to peripheral blood T cells using a range of vector systems, most commonly integrating viral vectors. Preclinical refinement of this approach has proceeded over several years to the point that clinical testing is now being undertaken at several centres, using increasingly sophisticated and therapeutically successful genetic payloads. This paper considers several aspects of the pre-clinical and clinical development of CAR-based immunotherapy and how this technology is acquiring an increasing niche in the treatment of both solid and haematological malignancies.

Intracellular delivery and trafficking dynamics of a lymphoma-targeting antibody-polymer conjugate

Ratiometric fluorescence and cellular fractionation studies were employed to characterize the intracellular trafficking dynamics of antibody-poly(propylacrylic acid) (PPAA) conjugates in CD22+ RAMOS-AW cells. The HD39 monoclonal antibody (mAb) directs CD22-dependent, receptor-mediated uptake in human B-cell lymphoma cells, where it is rapidly trafficked to the lysosomal compartment. To characterize the intracellular-release dynamics of the polymer-mAb conjugates, HD39-streptavidin (HD39/SA) was dual-labeled with pH-insensitive Alexa Fluor 488 and pH-sensitive pHrodo fluorophores. The subcellular pH distribution of the HD39/SA-polymer conjugates was quantified as a function of time by live-cell fluorescence microscopy, and the average intracellular pH value experienced by the conjugates was also characterized as a function of time by flow cytometry. PPAA was shown to alter the intracellular trafficking kinetics strongly relative to HD39/SA alone or HD39/SA conjugates with a control polymer, poly(methacryclic acid) (PMAA). Subcellular trafficking studies revealed that after 6 h, only 11% of the HD39/SA-PPAA conjugates had been trafficked to acidic lysosomal compartments with values at or below pH 5.6. In contrast, the average intracellular pH of HD39/SA alone dropped from 6.7 ± 0.2 at 1 h to 5.6 ± 0.5 after 3 h and 4.7 ± 0.6 after 6 h. Conjugation of the control polymer PMAA to HD39/SA showed an average pH drop similar to that of HD39/SA. Subcellular fractionation studies with tritium-labeled HD39/SA demonstrated that after 6 h, 89% of HD39/SA was associated with endosomes (Rab5+) and lysosomes (Lamp2+), while 45% of HD39/SA-PPAA was translocated to the cytosol (lactate dehydrogenase+). These results demonstrate the endosomal-releasing properties of PPAA with antibody-polymer conjugates and detail their intracellular trafficking dynamics and subcellular compartmental distributions over time.

Gene therapy of malignant solid tumors by targeting erbB2 receptors and by activating T cells

One of the strategies to improve the outcome of anti-erbB2-mediated immunotherapy is to combine anti-erbB2 antibodies with T-cell-based adoptive immunotherapy, which can be achieved by expressing anti-erbB2 mAb on the surface of T cells. A single-chain variable fragment (scFv) from an anti-erbB2 mAb has been expressed on T cell surface to bind to erbB2-positive cells, and CD3ζ has been expressed as a fusion partner at C terminus of this scFv to transduce signals. T cells grafted with this chimeric scFv/CD3ζ were able to specifically attack target tumor cells with no MHC/Ag restriction. To test the effects of CD28 signal on cellular activation and antitumor effectiveness of chimeric scFv/CD3ζ-modified T cells, we constructed a recombinant anti-erbB2 scFv/Fc/CD28/CD3ζ gene in a retroviral vector. T cells expressing anti-erbB2 scFv/Fc/CD28/CD3ζ specifically lyzed erbB2-positive target tumor cells and secreted not only interferon-γ (IFN-γ) but also IL-2 after binding to their target cells. Our data indicate that CD3 and CD28 signaling can be delivered in one molecule, which is sufficient for complete T cell activation without exogenous B7/CD28 co-stimulation.

Immunotherapy for B-Cell Neoplasms using T Cells expressing Chimeric Antigen Receptors: From antigen choice to clinical implementation

Immunotherapy with T cells expressing chimeric antigen receptors (CAR) is being evaluated as a potential treatment for B-cell neoplasms. In recent clinical trials it has shown promising results. As the number of potential candidate antigens expands, the choice of suitable target antigens becomes more challenging to design studies and to assess optimal efficacy of CAR. Careful evaluation of candidate target antigens is required to ensure that T cells expressing CAR will preferentially kill malignant cells with a minimal toxicity against normal tissues. B cells express specific surface antigens that can theoretically act as targets for CAR design. Although many of these antigens can stimulate effective cellular immune responses in vivo, their implementation in clinical settings remains a challenge. Only targeted B-cell antigens CD19 and CD20 have been tested in clinical trials. This article reviews exploitable B cell surface antigens for CAR design and examines obstacles that could interfere with the identification of potentially useful cellular targets.

The future is now: chimeric antigen receptors as new targeted therapies for childhood cancer

Improved outcomes for children with cancer hinge on the development of new targeted therapies with acceptable short-term and long-term toxicity. Progress in basic, preclinical, and clinical arenas spanning cellular immunology, gene therapy, and cell-processing technologies have paved the way for clinical applications of chimeric antigen receptor-based therapies. This is a new form of targeted immunotherapy that merges the exquisite targeting specificity of monoclonal antibodies with the potent cytotoxicity, potential for expansion, and long-term persistence provided by cytotoxic T cells. Although this field is still in its infancy, clinical trials have already shown clinically significant antitumor activity in neuroblastoma, chronic lymphocytic leukemia, and B-cell lymphoma, and trials targeting a variety of other adult and pediatric malignancies are under way. Ongoing work is focused on identifying optimal tumor targets and elucidating and manipulating both cell- and host-associated factors to support expansion and persistence of the genetically engineered cells in vivo. In pediatric oncology, CD19 and GD2 are compelling antigens that have already been identified for targeting pre-B acute lymphoblastic leukemia and neuroblastoma, respectively, with this approach, but it is likely that other antigens expressed in a variety of childhood cancers will also soon be targeted using this therapy. The potential to target essentially any tumor-associated cell-surface antigen for which a monoclonal antibody can be made opens up an entirely new arena for targeted therapy of childhood cancer.

Aurora kinase A-specific T-cell receptor gene transfer redirects T lymphocytes to display effective antileukemia reactivity

Aurora kinase A (AURKA) is overexpressed in leukemias. Previously, we demonstrated that AURKA-specific CD8(+) T cells specifically and selectively lysed leukemia cells, indicating that AURKA is an excellent target for immunotherapy. In this study, we examined the feasibility of adoptive therapy using redirected T cells expressing an HLA-A*0201-restricted AURKA(207-215)-specific T-cell receptor (TCR). Retrovirally transduced T cells recognized relevant peptide-pulsed but not control target cells. Furthermore, TCR-redirected CD8(+) T cells lysed AURKA-overexpressing human leukemic cells in an HLA-A*0201-restricted manner, but did not kill HLA-A*0201(+) normal cells, including hematopoietic progenitors. In addition, AURKA(207-215)-specific TCR-transduced CD4(+) T cells displayed target-responsive Th1 cytokine production. Finally, AURKA(207-215)-specific TCR-transduced CD8(+) T cells displayed antileukemia efficacy in a xenograft mouse model. Collectively, these data demonstrate the feasibility of redirected T cell-based AURKA-specific immunotherapy for the treatment of human leukemia.

Chimeric antigen receptor (CAR)-engineered lymphocytes for cancer therapy

INTRODUCTION

Chimeric antigen receptors (CARs) usually combine the antigen binding site of a monoclonal antibody with the signal activating machinery of a T cell, freeing antigen recognition from MHC restriction and thus breaking one of the barriers to more widespread application of cellular therapy. Similar to treatment strategies employing monoclonal antibodies, T cells expressing CARs are highly targeted, but additionally offer the potential benefits of active trafficking to tumor sites, in vivo expansion and long-term persistence. Furthermore, gene transfer allows the introduction of countermeasures to tumor immune evasion and of safety mechanisms.

AREAS COVERED

The basic structure of so-called first and later generation CARs and their potential advantages over other immune therapy systems. How these molecules can be grafted into immune cells (including retroviral and non-retroviral transduction methods) and strategies to improve the in vivo persistence and function of immune cells expressing CARs. Examples of tumor-associated antigens that have been targeted in preclinical models and clinical experience with these modified cells. Safety issues surrounding CAR gene transfer into T cells and potential solutions to them.

EXPERT OPINION

Because of recent advances in immunology, genetics and cell processing, CAR-modified T cells will likely play an increasing role in the cellular therapy of cancer, chronic infections and autoimmune disorders.

The B-cell tumor-associated antigen ROR1 can be targeted with T cells modified to express a ROR1-specific chimeric antigen receptor

Monoclonal antibodies and T cells modified to express chimeric antigen receptors specific for B-cell lineage surface molecules such as CD20 exert antitumor activity in B-cell malignancies, but deplete normal B cells. The receptor tyrosine kinase-like orphan receptor 1 (ROR1) was identified as a highly expressed gene in B-cell chronic lymphocytic leukemia (B-CLL), but not normal B cells, suggesting it may serve as a tumor-specific target for therapy. We analyzed ROR1-expression in normal nonhematopoietic and hematopoietic cells including B-cell precursors, and in hematopoietic malignancies. ROR1 has characteristics of an oncofetal gene and is expressed in undifferentiated embryonic stem cells, B-CLL and mantle cell lymphoma, but not in major adult tissues apart from low levels in adipose tissue and at an early stage of B-cell development. We constructed a ROR1-specific chimeric antigen receptor that when expressed in T cells from healthy donors or CLL patients conferred specific recognition of primary B-CLL and mantle cell lymphoma, including rare drug effluxing chemotherapy resistant tumor cells that have been implicated in maintaining the malignancy, but not mature normal B cells. T-cell therapies targeting ROR1 may be effective in B-CLL and other ROR1-positive tumors. However, the expression of ROR1 on some normal tissues suggests the potential for toxi-city to subsets of normal cells.

Adoptive T-cell immunotherapy of cancer using chimeric antigen receptor-grafted T cells

Harnessing the power of the immune system to target cancer has long been a goal of tumor immunologists. One avenue under investigation is the modification of T cells to express a chimeric antigen receptor (CAR). Expression of such a receptor enables T-cell specificity to be redirected against a chosen tumor antigen. Substantial research in this field has been carried out, incorporating a wide variety of malignancies and tumor-associated antigens. Ongoing investigations will ensure this area continues to expand at a rapid pace. This review will explain the evolution of CAR technology over the last two decades in addition to detailing the associated benefits and disadvantages. The outcome of recent phase I clinical trials and the impact that these have had upon the direction of future research in this field will also be addressed.

CD34-based enrichment of genetically engineered human T cells for clinical use results in dramatically enhanced tumor targeting

Objective clinical responses can be achieved in melanoma patients by infusion of T cell receptor (TCR) gene transduced T cells. Although promising, the therapy is still largely ineffective, as most patients did not benefit from treatment. That only a minority of the infused T cells were genetically modified and that these were extensively expanded ex vivo may have prevented their efficacy. We developed novel and generally applicable retroviral vectors that allow rapid and efficient selection of T cells transduced with human TCRs. These vectors encode two TCR chains and a truncated CD34 molecule (CD34t) in a single mRNA transcript. Transduced T cells were characterized and the effects of CD34-based enrichment of redirected T cells were evaluated. Both CD8(+) and CD4(+) T cells could be transduced and efficiently co-expressed all introduced transgenes on their surface. Importantly, more than fivefold enrichment of both the frequency of transduced cells and the specific anti-tumor reactivity of the effector population could be achieved by magnetic beads-based enrichment procedures readily available for clinical grade hematopoietic stem cell isolation. This CD34-based enrichment technology will improve the feasibility of adoptive transfer of clinically relevant effectors. In addition to their enhanced tumor recognition, the enriched redirected T cells may also show superior reactivity and persistence in vivo due to the high purity of transduced cells and the shortened ex vivo culture.

Mathematical modeling of chimeric TCR triggering predicts the magnitude of target lysis and its impairment by TCR downmodulation

We investigated relationships among chimeric TCR (cTCR) expression density, target Ag density, and cTCR triggering to predict lysis of target cells by cTCR(+) CD8(+) T human cells as a function of Ag density. Triggering of cTCR and canonical TCR by Ag could be quantified by the same mathematical equation, but cTCR represented a special case in which serial triggering was abrogated. The magnitude of target lysis could be predicted as a function of cTCR triggering, and the predicted minimum cTCR density required for maximal target lysis by CD20-specific cTCR was experimentally tested. cTCR density below approximately 20,000 cTCR/cell impaired target lysis, but increasing cTCR expression above this density did not improve target lysis or Ag sensitivity. cTCR downmodulation to densities below this critical minimum by interaction with Ag-expressing targets limited the sequential lysis of targets in a manner that could be predicted based on the number of cTCRs remaining. In contrast, acute inhibition of lysis of primary, intended targets (e.g., leukemic B cells) due to the presence of an excess of secondary targets (e.g., normal B cells) was dependent on the Ag density of the secondary target but occurred at Ag densities insufficient to promote significant cTCR downmodulation, suggesting a role for functional exhaustion rather than insufficient cTCR density. This suggests increasing cTCR density above a critical threshold may enhance sequential lysis of intended targets in isolation, but will not overcome the functional exhaustion of cTCR(+) T cells encountered in the presence of secondary targets with high Ag density.

Induction/engineering, detection, selection, and expansion of clinical-grade human antigen-specific CD8 cytotoxic T cell clones for adoptive immunotherapy

Adoptive transfer of effector antigen-specific immune cells is becoming a promising treatment option in allogeneic transplantation, infectious diseases, cancer, and autoimmune disorders. Within this context, the important role of CD8+ cytotoxic T cells (CTLs) is objective of intensive studies directed to their in vivo and ex vivo induction, detection, selection, expansion, and therapeutic effectiveness. Additional questions that are being addressed by the scientific community are related to the establishment and maintenance of their longevity and memory state as well as to defining critical conditions underlying their transitions between discrete, but functionally different subtypes. In this article we review and comment latest approaches and techniques used for preparing large amounts of antigen-specific CTLs, suitable for clinical use.

Treatment of lymphoma with adoptively transferred T cells

BACKGROUND

Chemotherapy-resistant lymphomas can be cured with allogeneic hematopoietic cell transplantation, demonstrating the susceptibility of these tumors to T cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. Efforts have, therefore, been made to develop alternative T cell based therapies, and there is growing evidence that adoptive therapy with T cells targeted to lymphoma-associated antigens may be a safe and effective new method for treating this group of diseases.

OBJECTIVE/METHODS

We review publications on adoptive therapy with ex vivo expanded T cells targeting viral antigens, as well as genetically modified autologous T cells, as strategies for the treatment of lymphoma, with the goal of providing an overview of these approaches.

RESULTS/CONCLUSIONS

Epstein-Barr virus specific T cell therapy is an effective and safe method of treating Epstein-Barr virus associated lymphomas; however, most lymphoma subtypes do not express EBV antigens. For these diseases, adoptive immunotherapy with genetically modified T cells expressing chimeric T cell receptors targeting lymphoma-associated antigens such as CD19 and CD20 appears to be a promising alternative. Recent innovations including enhanced co-stimulation, exogenous cytokine administration and use of memory T cells promise to overcome many of the limitations and pitfalls initially encountered with this approach.

Antibody-mediated B-cell depletion before adoptive immunotherapy with T cells expressing CD20-specific chimeric T-cell receptors facilitates eradication of leukemia in immunocompetent mice

We have established a model of leukemia immunotherapy using T cells expressing chimeric T-cell receptors (cTCRs) targeting the CD20 molecule expressed on normal and neoplastic B cells. After transfer into human CD20 (hCD20) transgenic mice, cTCR(+) T cells showed antigen-specific delayed egress from the lungs, concomitant with T-cell deletion. Few cTCR(+) T cells reached the bone marrow (BM) in hCD20 transgenic mice, precluding effectiveness against leukemia. Anti-hCD20 antibody-mediated B-cell depletion before adoptive T-cell therapy permitted egress of mouse CD20-specific cTCR(+) T cells from the lungs, enhanced T-cell survival, and promoted cTCR(+) T cell-dependent elimination of established mouse CD20(+) leukemia. Furthermore, CD20-specific cTCR(+) T cells eliminated residual B cells refractory to depletion with monoclonal antibodies. These findings suggest that combination of antibody therapy that depletes antigen-expressing normal tissues with adoptive T-cell immunotherapy enhances the ability of cTCR(+) T cells to survive and control tumors.

Lymphoma immunotherapy: vaccines, adoptive cell transfer and immunotransplant

Therapy for non-Hodgkin lymphoma has benefited greatly from basic science and clinical research such that chemotherapy and monoclonal antibody therapy have changed some lymphoma subtypes from uniformly lethal to curable, but the majority of lymphoma patients remain incurable. Novel therapies with less toxicity and more specific targeting of tumor cells are needed and immunotherapy is among the most promising of these. Recently completed randomized trials of idiotype vaccines and earlier-phase trials of other vaccine types have shown the ability to induce antitumor T cells and some clinical responses. More recently, trials of adoptive transfer of antitumor T cells have demonstrated techniques to increase the persistence and antitumor effect of these cells. Herein, we discuss lymphoma immunotherapy clinical trial results and what lessons can be taken to improve their effect, including the combination of vaccination and adoptive transfer in an approach we have dubbed 'immunotransplant'.

The promise and potential pitfalls of chimeric antigen receptors

One important purpose of T cell engineering is to generate tumor-targeted T cells through the genetic transfer of antigen-specific receptors, which consist of either physiological, MHC-restricted T cell receptors (TCRs) or non MHC-restricted chimeric antigen receptors (CARs). CARs combine antigen-specificity and T cell activating properties in a single fusion molecule. First generation CARs, which included as their signaling domain the cytoplasmic region of the CD3zeta or Fc receptor gamma chain, effectively redirected T cell cytotoxicity but failed to enable T cell proliferation and survival upon repeated antigen exposure. Receptors encompassing both CD28 and CD3zeta are the prototypes for second generation CARs, which are now rapidly expanding to a diverse array of receptors with different functional properties. First generation CARs have been tested in phase I clinical studies in patients with ovarian cancer, renal cancer, lymphoma, and neuroblastoma, where they have induced modest responses. Second generation CARs, which are just now entering the clinical arena in the B cell malignancies and other cancers, will provide a more significant test for this approach. If the immunogenicity of CARs can be averted, the versatility of their design and HLA-independent antigen recognition will make CARs tools of choice for T cell engineering for the development of targeted cancer immunotherapies.

Vaccine therapy and chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (CLL) should be an ideal target for immune-mediated responses. CLL arises from B cells that can act as antigen-presenting cells (APCs), expresses unique tumour antigens, and has been shown to be a target of the allogeneic T cells which mediate a graft-versus-leukaemia effect. Despite these potential benefits, immune responses against CLL cells have been difficult to elicit. CLL induces immune defects in the host, the tumour cells are inefficient APCs, and therapies given to patients with CLL are themselves immunosuppressive. Successful vaccination approaches in this disease will require steps to overcome these difficulties, including identification of the targets of immune responses in this disease to enable monitoring of the immune response after vaccination, improved presentation of antigens, and steps to improve the immune defects that accompany this disease.

Immunotherapy targeting EBV-expressing lymphoproliferative diseases

Epstein-Barr virus (EBV) is associated with non-Hodgkin's lymphoma (NHL), occurring in immunocompetent individuals as well as those with immunodeficiency. In patients with immunodeficiency, the nature of EBV infection in the malignant cell determines the pattern of antigen expression and the associated presence of targets for cellular immunotherapy. EBV-expressing lymphoma cells in the setting of immunodeficiency express type III latency, characterized by expression of all nine latent-cycle EBV antigens, and strategies to restore EBV-specific immune responses have resulted in effective anti-tumour activity. In contrast, EBV-associated NHL in immunocompetent individuals is characterized by type II latency, where a more restricted array of EBV-associated antigens is expressed. In this setting, T-cell therapies are limited by inadequate persistence of transferred T cells and by tumour-evasion strategies. A number of strategies to genetically modify the infused T cells and modulate the host environment are under evaluation.

Immunotherapy of lymphomas with T cells modified by anti-CD20 scFv/CD28/CD3zeta recombinant gene

One of the approaches to make anti-CD20 antibody more efficient is to express this antibody on the surface of T cells. scFv from anti-CD20 antibody has been expressed on T cell surface to bind to CD20 positive cells and CD3zeta has been expressed as a fusion partner to transduct signals. T cells grafted with this chimeric scFv/CD3zeta were able to redirect grafted T cells to an MHC/Ag-independent antitumor response. To test the effects of CD28 signal on the cellular activation and antitumor effectiveness of chimeric scFv/CD3zeta modified T cells, we constructed a recombinant anti-CD20 scFv/CD28/CD3zeta gene in a retroviral vector. T cells expressing anti-CD20 scFv/CD28/CD3zeta specifically lysed CD20 positive target tumor cells and secreted not only IFN-gamma but also IL-2 after binding to their target cells. Our data indicate that CD3 and CD28 signalling can be delivered in one molecule, which is sufficient for complete T cell activation without exogenous B7/CD28 costimulation.

Antigen sensitivity of CD22-specific chimeric TCR is modulated by target epitope distance from the cell membrane

We have targeted CD22 as a novel tumor-associated Ag for recognition by human CTL genetically modified to express chimeric TCR (cTCR) recognizing this surface molecule. CD22-specific cTCR targeting different epitopes of the CD22 molecule promoted efficient lysis of target cells expressing high levels of CD22 with a maximum lytic potential that appeared to decrease as the distance of the target epitope from the target cell membrane increased. Targeting membrane-distal CD22 epitopes with cTCR(+) CTL revealed defects in both degranulation and lytic granule targeting. CD22-specific cTCR(+) CTL exhibited lower levels of maximum lysis and lower Ag sensitivity than CTL targeting CD20, which has a shorter extracellular domain than CD22. This diminished sensitivity was not a result of reduced avidity of Ag engagement, but instead reflected weaker signaling per triggered cTCR molecule when targeting membrane-distal epitopes of CD22. Both of these parameters were restored by targeting a ligand expressing the same epitope, but constructed as a truncated CD22 molecule to approximate the length of a TCR:peptide-MHC complex. The reduced sensitivity of CD22-specific cTCR(+) CTL for Ag-induced triggering of effector functions has potential therapeutic applications, because such cells selectively lysed B cell lymphoma lines expressing high levels of CD22, but demonstrated minimal activity against autologous normal B cells, which express lower levels of CD22. Thus, our results demonstrate that cTCR signal strength, and consequently Ag sensitivity, can be modulated by differential choice of target epitopes with respect to distance from the cell membrane, allowing discrimination between targets with disparate Ag density.

Adoptive immunotherapy for indolent non-Hodgkin lymphoma and mantle cell lymphoma using genetically modified autologous CD20-specific T cells

Adoptive immunotherapy with T cells expressing a tumor-specific chimeric T-cell receptor is a promising approach to cancer therapy that has not previously been explored for the treatment of lymphoma in human subjects. We report the results of a proof-of-concept clinical trial in which patients with relapsed or refractory indolent B-cell lymphoma or mantle cell lymphoma were treated with autologous T cells genetically modified by electroporation with a vector plasmid encoding a CD20-specific chimeric T-cell receptor and neomycin resistance gene. Transfected cells were immunophenotypically similar to CD8(+) effector cells and showed CD20-specific cytotoxicity in vitro. Seven patients received a total of 20 T-cell infusions, with minimal toxicities. Modified T cells persisted in vivo 1 to 3 weeks in the first 3 patients, who received T cells produced by limiting dilution methods, but persisted 5 to 9 weeks in the next 4 patients who received T cells produced in bulk cultures followed by 14 days of low-dose subcutaneous interleukin-2 (IL-2) injections. Of the 7 treated patients, 2 maintained a previous complete response, 1 achieved a partial response, and 4 had stable disease. These results show the safety, feasibility, and potential antitumor activity of adoptive T-cell therapy using this approach. This trial was registered at www.clinicaltrials.gov as #NCT00012207.

Optimizing adoptive polyclonal T cell immunotherapy of lymphomas, using a chimeric T cell receptor possessing CD28 and CD137 costimulatory domains

We previously demonstrated the feasibility of generating therapeutic numbers of cytotoxic T lymphocyte (CTL) clones expressing a CD20-specific scFvFc:CD3zeta chimeric T cell receptor (cTCR), making them specifically cytotoxic for CD20+ B lymphoma cells. However, the process of generating and expanding he CTL clones was laborious, the CTL clones expressed the cTCR at low surface density, and they exhibited suboptimal proliferation and cytotoxicity. To improve the performance of the CTLs in vitro and in vivo, we engineered "second-generation'' plasmid constructs containing a translational enhancer (SP163) and CD28 and CD137 costimulatory domains in cis with the CD3zeta intracellular signaling domain of the cTCR gene. Furthermore, we verified the superiority of generating genetically modified polyclonal T cells expressing the second-generation cTCR rather than T cell clones. Our results demonstrate that SP163 enhances the surface expression of the cTCR; that the second-generation cTCR improves CTL activation, proliferation, and cytotoxicity; and that polyclonal T cells proliferate rapidly in vitro and mediate potent CD20-specific cytotoxicity. This study provides the preclinical basis for a clinical trial of adoptive T cell immunotherapy for patients with relapsed CD20+ mantle cell lymphoma and indolent lymphomas.

Gene therapy and active immune therapy of hematologic malignancies

Gene therapy for patients with hematologic malignancies, particularly chronic lymphocytic leukemia (CLL), have focused on transducing primary leukemia cells with a virus vector to express immune-stimulating genes which can induce and propagate a productive and clinically significant immune response against the malignant cells. A variety of replication-defective vectors has been studied to transduce genes for cytokines and function-associated surface molecules. Active vaccines have been developed in vitro, and their activity has been confirmed in clinical trials. Ongoing work aims to optimize this strategy and to identify the appropriate and optimal patient groups in which to apply vaccine therapy. Clinical trials also have provided insight into unexpected alternative mechanisms through which these strategies might provide a clinical benefit.