Adoptive immunotherapy of EBV-associated malignancies with EBV-specific cytotoxic T-cell lines

Next-Generation Chimeric Antigen Receptor T-Cell Therapy: Going off the Shelf

Autologous, patient-specific chimeric antigen receptor T-cell (CART) therapy has emerged as a powerful and potentially curative therapy for cancer, especially for CD19-positive hematological malignancies. Indeed, on August 30, 2017, the University of Pennsylvania-designed CD19-directed CART (CART-19) cell therapy (CTL019, tisagenlecleucel-t, Kymriah - Novartis) became the first CART therapy approved by the Food and Drug Administration (FDA) for acute lymphoblastic leukemia. However, the development of CART technology and its wider application is partly limited by the patient-specific nature of such a platform and by the time required for manufacturing. The efficacious generation of universal allogeneic CART cells would overcome these limitations and represent a major advance in the field. However, several obstacles in the generation of universal CART cells need to be overcome, namely the risk of CART rejection and the risk of graft-versus-host disease mediated by the allogeneic CART. In this review, we discuss the different strategies being employed to generate universal CART and provide our perspective on the successful development of a truly off-the-shelf CART product.

Prospects of a novel vaccination strategy for human gamma-herpesviruses

Due to the oncogenic potential associated with persistent infection of human gamma-herpesviruses, including Epstein-Barr virus (EBV or HHV-4) and Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8), vaccine development has focused on subunit vaccines. However, the results using an animal model of mouse infection with a related rodent virus, murine gamma-herpesvirus 68 (MHV-68, γHV-68, or MuHV-4), have shown that the only effective vaccination strategy is based on live attenuated viruses, including viruses engineered to be incapable of establishing persistence. Vaccination with a virus lacking persistence would eliminate many potential complications. Progress in understanding persistent infections of EBV and KSHV raises the possibility of engineering a live attenuated virus without persistence. Therefore, we should keep the option open for developing a live EBV or KSHV vaccine.

Immunotherapy of malignant brain tumors

Despite aggressive multi-modality therapy including surgery, radiation, and chemotherapy, the prognosis for patients with malignant primary brain tumors remains very poor. Moreover, the non-specific nature of conventional therapy for brain tumors often results in incapacitating damage to surrounding normal brain and systemic tissues. Thus, there is an urgent need for the development of therapeutic strategies that precisely target tumor cells while minimizing collateral damage to neighboring eloquent cerebral cortex. The rationale for using the immune system to target brain tumors is based on the premise that the inherent specificity of immunologic reactivity could meet the clear need for more specific and precise therapy. The success of this modality is dependent on our ability to understand the mechanisms of immune regulation within the central nervous system (CNS), as well as counter the broad defects in host cell-mediated immunity that malignant gliomas are known to elicit. Recent advances in our understanding of tumor-induced and host-mediated immunosuppressive mechanisms, the development of effective strategies to combat these suppressive effects, and a better understanding of how to deliver immunologic effector molecules more efficiently to CNS tumors have all facilitated significant progress toward the realization of true clinical benefit from immunotherapeutic treatment of malignant gliomas.

Stimulation by means of dendritic cells followed by Epstein-Barr virus-transformed B cells as antigen-presenting cells is more efficient than dendritic cells alone in inducing Aspergillus f16-specific cytotoxic T cell responses

Adoptive immunotherapy with in vitro expanded antigen-specific cytotoxic T lymphocytes (CTLs) may be an effective approach to prevent, or even treat, Aspergillus (Asp) infections. Such lines can be generated using monocyte-derived dendritic cells (DC) as antigen-presenting cells (APC) but requires a relatively high volume of starting blood. Here we describe a method that generates Asp-specific CTL responses more efficiently using a protocol of antigen presented on DC followed by Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (BLCL) as APC. Peripheral blood mononuclear cells were stimulated weekly (2-5x) with a complete pool of pentadecapeptides (PPC) spanning the coding region of Asp f16 pulsed onto autologous mature DC. Cultures were split and stimulated subsequently with either PPC-DC or autologous PPC-pulsed BLCL (PPC-BLCL). Lines from the DC/BLCL arm demonstrated Asp f16-specific cytotoxicity earlier and to a higher degree than lines generated with PPC-DC alone. The DC/BLCL-primed lines showed a higher frequency of Asp f16-specific interferon (IFN)-gamma producing cells but an identical effector cell phenotype and peptide specificity compared to PPC-DC-only-primed lines. Tumour necrosis factor (TNF)-alpha, but not IL-10, appeared to play a role in the effectiveness of BLCL as APC. These results demonstrate that BLCL serve as highly effective APC for the stimulation of Asp f16-specific T cell responses and that a culture approach using initial priming with PPC-DC followed by PPC-BLCL may be a more effective method to generate Asp f16-specific T cell lines and requires less starting blood than priming with PPC-DC alone.

Update on cancer vaccines

PURPOSE OF REVIEW

Vaccination against cancer has had a variable history, with claims of success often fading into disappointment. The reasons for this include poor vaccine design, inadequate understanding of the nature of the immune response, and a lack of objective measures to evaluate performance. The impact of genetic technology has changed everything. We now have multiple strategies to identify candidate tumor antigens, and we understand more about activation and regulation of immunity against cancer. There are novel vaccine strategies to activate specific attack on tumor cells. We also have modern assays using surrogate markers of performance to correlate with clinical effects. It is timely to select significant relevant papers to illustrate the growing potential for patients with cancer.

RECENT FINDINGS

Recent findings include tumor antigen discovery and vaccine formulation, relevant knowledge concerning mechanisms of induction of effective immunity from preclinical models, and translation into clinical trials with objective evaluation of performance.

SUMMARY

The ability of the immune response to dispose of cancer cells is clear. Passive transfer of antibody or immune cells is already clinically successful. We are now in a position to harness new gene-based information to design vaccines capable of inducing effective and long-lasting immunity. Safe vaccines could be used either in patients or in transplant donors. Pilot clinical trials are the means of testing performance, with continuing vaccine design modification to target specific antigens in different cancers.

Differentiation of naive cord-blood T cells into CD19-specific cytolytic effectors for posttransplantation adoptive immunotherapy

Disease relapse is a barrier to achieving therapeutic success after unrelated umbilical cord-blood transplantation (UCBT) for B-lineage acute lymphoblastic leukemia (B-ALL). While adoptive transfer of donor-derived tumor-specific T cells is a conceptually attractive approach to eliminating residual disease after allogeneic hematopoietic stem cell transplantation, adoptive immunotherapy after UCBT is constrained by the difficulty of generating antigen-specific T cells from functionally naive umbilical cord-blood (UCB)-derived T cells. Therefore, to generate T cells that recognize B-ALL, we have developed a chimeric immunoreceptor to redirect the specificity of T cells for CD19, a B-lineage antigen, and expressed this transgene in UCB-derived T cells. An ex vivo process, which is compliant with current good manufacturing practice for T-cell trials, has been developed to genetically modify and numerically expand UCB-derived T cells into CD19-specific effector cells. These are capable of CD19-restricted cytokine production and cytolysis in vitro, as well as mediating regression of CD19+ tumor and being selectively eliminated in vivo. Moreover, time-lapse microscopy of the genetically modified T-cell clones revealed an ability to lyse CD19+ tumor cells specifically and repetitively. These data provide the rationale for infusing UCB-derived CD19-specific T cells after UCBT to reduce the incidence of CD19+ B-ALL relapse.

T cell-mediated graft-versus-leukemia reactions after allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation represents the only curative approach for many hematological malignancies. During the last years the impact of the conditioning regimen has been re-assessed. With the advent of reduced-intensity conditioning the paradigm has changed from cytoreduction executed by high-dose radio-chemotherapy to immunological surveillance of leukemia by donor cells. Distinct subsets of T cells and NK cells contribute to graft-versus-leukemia reactions. So far, cytotoxic T lymphocytes are the mainstay of allogeneic immunotherapy. Here, we summarise the current knowledge of T cell-mediated graft-versus-leukemia reactions and present results from pre-clinical and clinical studies of T cell-based adoptive immunotherapy. We address the issues of feasibility and specificity of adoptive immunotransfer from a clinical point of view and discuss the prerequisites for successful clinical applications. Finally, the prospects for immunological research that have evolved with the increasing use of reduced-intensity conditioning and allogeneic stem cell transplantation are highlighted.

Telomere loss, senescence, and genetic instability in CD4+ T lymphocytes overexpressing hTERT

Little is known about the long-term consequences of overexpression of the human telomerase reverse transcriptase (hTERT) gene in T lymphocytes. To address this issue, we transduced polyclonal as well as clonally derived populations of naive and memory CD44 T cells from 2 healthy donors (aged 24 and 34 years) with retroviral vectors encoding green fluorescence protein (GFP) and hTERT (GFP-hTERT) or GFP alone. After transduction, cells were sorted on the basis of GFP expression and cultured in vitro until senescence. T cells transduced with hTERT exhibited high stable telomerase activity throughout the culture period. Relative to GFP controls, minor changes in overall gene expression were observed yet the proliferative lifespan of the hTERT-transduced populations was significantly increased and the rate of telomere loss was lower. Nevertheless, hTERT-transduced cells showed progressive telomere loss and had shorter telomeres at senescence than controls (2.3 +/- 0.3 kilobase [kb] versus 3.4 +/- 0.1 kb). Furthermore, a population of cells with 4N DNA consisting of binucleated cells with connected nuclei emerged in the hTERT-transduced cells prior to senescence. We conclude that overexpression of hTERT in CD4+ T cells provides a proliferative advantage independent of the average telomere length but does not prevent eventual genetic instability and replicative senescence.

Augmentation of type-1 polarizing ability of monocyte-derived dendritic cells from chronically immunosuppressed organ-transplant recipients

BACKGROUND

Chronic immunosuppressive (IS) therapy impairs normal T-cell immune surveillance and may predispose to opportunistic infections and malignancies that represent life-threatening complication of solid-organ transplantation (SOTx). Our study was designed to ascertain the impact of chronic in vivo administration of IS on the ability of monocyte-derived dendritic cells (MoDC) to differentiate, mature, and function ex vivo. The potential of these cells to be implemented for DC-based adoptive immunotherapy was also considered.

METHODS

MoDCs were propagated by conventional procedures, their phenotype was analyzed by flow cytometry, and their function was assessed by mixed leukocyte reaction, enzyme-linked immunoadsorbent assay, and ELISPOT assays. Nuclear translocation of nuclear factor (NF)-kB was analyzed by electrophoretic mobility shift assay.

RESULTS

Circulating DC1s in peripheral blood were reduced in SOTx patients. MoDCs generated from patients displayed higher endocytic activity versus normal DCs, indicating their comparative immaturity. Patients' DCs exposed to pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin [IL]-1beta, and IL-6) were less able to mature, to stimulate recall antigen (Ag)- or allo-Ag-induced proliferation responses, or to secrete IL-12p70. These deficiencies were associated with a decrease in NF-kB translocation. In contrast, combination of pro-inflammatory cytokines and interferon (IFN)-gamma (a Th1-polarizing factor) augmented patients' DC1-type function and IL-12p70 production by way of an NF-kB-independent mechanism.

CONCLUSIONS

Chronic IS restrains DC differentiation, maturation, and function at a transcriptional level; however, type-1 polarizing potential of patients' DC1 can be augmented ex vivo by a two-signal stimulation provided by pro-inflammatory cytokines and IFN-gamma. These results may have implications for DC-based immunotherapy of malignancies in the transplantation setting.

Targeting cytotoxic T lymphocytes for cancer immunotherapy

In light of their preeminent role in cellular immunity, there is considerable interest in targeting of cytotoxic T-lymphocytes to cancer. This review summarises the active and passive immunotherapeutic approaches under development to achieve this goal, emphasising how recent advances in tumour immunology and gene transfer have impacted upon this field.

DNA vaccines to attack cancer

Delivery of antigens by injection of the encoding DNA allows access to multiple antigen-presenting pathways. Knowledge of immunological processes can therefore be used to modify construct design to induce selected effector functions. Expression can be directed to specific intracellular sites, and additional genes can be fused or codelivered to amplify responses. Therapeutic vaccination against cancer adds a requirement to overcome tolerance and to activate a weakened immune repertoire. Induction of CD4(+) T helper cells is critical for both antibody and T cell effector responses. To activate immunity against tumor antigens, we fused the tumor-derived sequences to genes encoding microbial proteins. This strategy engages T helper cells from the large antimicrobial repertoire for linked help for inducing antibody against cell-surface tumor antigens. The principle of linked T cell help also holds for induction of epitope-specific antitumor CD8(+) T cells, but the microbial sequence has to be minimized to avoid competition with tumor antigens. Epitope-specific DNA vaccination leads to powerful antitumor attack and can activate immunity from a profoundly tolerized repertoire. Vaccine designs validated in preclinical models are now in clinical trial with immune responses detected against both tumor antigens and fused microbial antigens. DNA priming is highly efficient, but boosting may benefit from increased antigen expression. Physical methods including electroporation provide increased expression without introducing additional competing antigens. A wide range of cancers can be targeted, and objective assays of response will determine efficacy.

Epstein-barr virus nuclear antigen 1: from immunologically invisible to a promising T cell target

Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1)--the one EBV antigen that is expressed in all EBV-associated malignancies--has long been thought to go undetected by the cell-mediated immune system. However, recent studies show that EBNA1 can be presented to both CD4+ and CD8+ T cells, making it a potential new target for immunotherapy of EBV-related cancers.

Genetic, cellular and immune approaches to disease therapy: past and future

Advances in immunology and molecular genetics have accelerated our understanding of the genetic and cellular basis of many diseases. At the same time, remarkable progress in recombinant DNA technology has enabled the development of molecular and cellular treatments for infectious diseases, inherited disorders and cancer. This Perspective is intended to give a sample of the progress over the past ten years in cellular, genetic and immune therapy of disease. During this time, monoclonal antibody technology and cellular transplantation have begun to come of age in biomedicine. Innovations in gene delivery have not only catalyzed the nascent field of human gene therapy, but may also ultimately impact human health by advancing recombinant vaccine technology.

Fiber-modified adenoviruses generate subgroup cross-reactive, adenovirus-specific cytotoxic T lymphocytes for therapeutic applications

Adenovirus (Ad) infections are responsible for considerable morbidity and mortality, particularly in pediatric hematopoietic stem cell transplant (HSCT) recipients. To date there is no therapy. The present study was motivated by the potential for using adoptive immunotherapy as either prophylaxis or treatment for Ad infections and associated diseases. The authors have developed a protocol to reactivate Ad-specific memory T cells from peripheral blood mononuclear cells (PBMCs) using a clinical-grade adenoviral vector. Such lines contain a specific CD4 and CD8 T-cell component and are capable of recognizing and lysing target cells infected with wild-type Ad serotypes from different Ad groups. Furthermore, the frequency of Ad-specific precursors can be determined in PBMCs ex vivo and used as a means to assess changes in Ad-specific T-cell memory responses after infusion. This is the first report of a simple and reproducible method to activate and expand Ad-specific cytotoxic T lymphocytes (CTLs), which should be protective against the range of different Ad subtypes that affect transplant recipients.

Epstein-Barr virus: induction and control of cell transformation

Epstein-Barr virus (EBV), a ubiquitous human herpes virus, is associated with an increasing number of lymphoid and epithelial malignancies. The ability of the virus to establish life-long persistent infections and induce growth transformation is related to the function of a set of viral proteins that are variously expressed in both normal and malignant cells. Recent evidence indicates that these viral proteins are able to usurp cellular pathways that promote the cell growth and survival, while impairing anti-viral immune responses. Elucidation of the mechanisms by which EBV induces cell transformation and escapes host immune control provides the rational background for the design of new strategies of intervention for EBV-related malignancies.

Anti-human immunodeficiency virus-gag CD8+ memory T cells generated in vitro from Listeria-immunized mice

The goal of vaccination is the generation of immune memory, an immune state that permits rapid and intense recall responses to a pathogen. Considerable effort is being made to understand the nature of memory T cells. We report here that by extending the length of in vitro culture following a single restimulation with specific peptide, preparations of highly enriched, highly active antigen-specific CD8+ memory T cells could be obtained. These cultures were begun with splenocytes from mice primed by infection either with an attenuated strain of Listeria monocytogenes or vaccinia virus, both expressing the human immunodeficiency virus-1-gag gene. In the cultures, antigen-specific cytotoxic T lymphocyte (CTL) activity reached a maximum at about 9 days and thereafter fell to negligible values. Concomitant with the fall of CTL activity, however, we observed enrichment for a subset of CD11ahigh antigen-specific gag-tetramerpos CD8+ T cells. The cells showed little or no 4-hr CTL activity, but had high delayed (18-hr) CTL activity, and very high cytolytic activity after restimulation. They rapidly expressed interferon-gamma production. Their growth and survival after sorting was completely dependent on interleukin-2 or -15. As few as 5000 of the fluorescence-activated cell sorting-purified cells protected recipients against challenge 3 months after transfer. In response to the challenge, the cells repopulated lymphoid and non-lymphoid organs and showed a sizeable increase in number. The cells therefore demonstrate high protective activity for long periods of time. These cultured cells are thus a potential source of enriched natural memory T cells for reperfusion studies and in which the mechanisms that underlie the generation, differentiation and persistence of memory can be examined.

Gene Therapy Applications to Cancer Treatment

Over the past ten years significant advances have been made in the fields of gene therapy and tumour immunology, such that there now exists a considerable body of evidence validating the proof in the principle of gene therapy based cancer vaccines. While clinical benefit has so far been marginal, data from preclinical and early clinical trials of gene therapy combined with standard therapies are strongly suggestive of additional benefit. Many reasons have been proposed to explain the paucity of clinical responses to single agent vaccination strategies including the poor antigenicity of tumour cells and the development of tolerance through down-regulation of MHC, costimulatory, signal transduction, and other molecules essential for the generation of strong immune responses. In addition, there is now evidence from animal models that the growing tumour may actively inhibit the host immune response. Removal of the primary tumour prior to T cell transfer from the spleen of cancer bearing animals, led to effective tumour cell line specific immunity in the recipient mouse suggesting that there is an ongoing tumour-host interaction. This model also illustrates the potential difficulties of clinical vaccine trials in patients with advanced stage disease.