Production of genetically modified Epstein-Barr virus-specific cytotoxic T cells for adoptive transfer to patients at high risk of EBV-associated lymphoproliferative disease

Advances in virus-specific T-cell therapy for polyomavirus infections: A comprehensive review

Polyomaviruses are a group of small, non-enveloped, double-stranded DNA viruses that can infect various hosts, including humans. BKPyV causes conditions such as human polyomavirus-associated nephropathy (HPyVAN), human polyomavirus-associated haemorrhagic cystitis (HPyVHC), and human polyomavirus-associated urothelial cancer (HPyVUC). JC polyomavirus (JCPyV), on the other hand, is the causative agent of progressive multifocal leukoencephalopathy (PML), a severe demyelinating disease of the central nervous system. PML primarily affects immunocompromised individuals, including those with HIV, recipients of certain immunosuppressive therapies, and transplant patients. The treatment options for HPyV infections have been limited, but recent developments in virus-specific T cell (VST) therapy have shown promise. Although VST therapy has shown potential in treating both BKPyV and JCPyV infections, several challenges remain. These include the time-consuming and costly preparation of VSTs, the need for sophisticated production facilities, and uncertainties regarding the optimal cell type and infusion frequency. To the best of our knowledge, 85 patients with haemorrhagic cystitis, 27 patients with BKPyV viremia, 2 patients with BKPyV nephritis, 14 patients with haemorrhagic cystitis and BKPyV viremia, and 32 patients with PML have been treated with VST in the literature. The overall response results were 82 complete response, 33 partial response, 35 no response, and 10 no-outcome-reported. This review underscores the importance of VST therapy as a promising treatment approach for polyomavirus infections, emphasising the need for continued research and clinical trials to refine and expand this innovative immunotherapeutic strategy.

Evaluation of novel Epstein-Barr virus-derived antigen formulations for monitoring virus-specific T cells in pediatric patients with infectious mononucleosis

BACKGROUND

Infection with the Epstein-Barr virus (EBV) elicits a complex T-cell response against a broad range of viral proteins. Hence, identifying potential differences in the cellular immune response of patients with different EBV-associated diseases or different courses of the same disorder requires interrogation of a maximum number of EBV antigens. Here, we tested three novel EBV-derived antigen formulations for their ability to reactivate virus-specific T cells ex vivo in patients with EBV-associated infectious mononucleosis (IM).

METHODS

We comparatively analyzed EBV-specific CD4+ and CD8+ T-cell responses to three EBV-derived antigen formulations in 20 pediatric patients during the early phase of IM: T-activated EBV proteins (BZLF1, EBNA3A) and EBV-like particles (EB-VLP), both able to induce CD4+ and CD8+ T-cell responses ex vivo, as well as an EBV-derived peptide pool (PP) covering 94 well-characterized CD8+ T-cell epitopes. We assessed the specificity, magnitude, kinetics, and functional characteristics of EBV-specific immune responses at two sequential time points (v1 and v2) within the first six weeks after IM symptom onset (Tonset).

RESULTS

All three tested EBV-derived antigen formulations enabled the detection of EBV-reactive T cells during the early phase of IM without prior T-cell expansion in vitro. EBV-reactive CD4+ and CD8+ T cells were mainly mono-functional (CD4+: mean 64.92%, range 56.15-71.71%; CD8+: mean 58.55%, range 11.79-85.22%) within the first two weeks after symptom onset (v1) with IFN-γ and TNF-secreting cells representing the majority of mono-functional EBV-reactive T cells. By contrast, PP-reactive CD8+ T cells were primarily bi-functional (>60% at v1 and v2), produced IFN-γ and TNF and had more tri-functional than mono-functional components. We observed a moderate correlation between viral load and EBNA3A, EB-VLP, and PP-reactive CD8+ T cells (rs = 0.345, 0.418, and 0.356, respectively) within the first two weeks after Tonset, but no correlation with the number of detectable EBV-reactive CD4+ T cells.

CONCLUSIONS

All three EBV-derived antigen formulations represent innovative and generic recall antigens suitable for monitoring EBV-specific T-cell responses ex vivo. Their combined use facilitates a thorough analysis of EBV-specific T-cell immunity and allows the identification of functional T-cell signatures linked to disease development and severity.

Epstein‒Barr virus-associated cellular immunotherapy

Epstein‒Barr virus (EBV) is a human herpes virus that is saliva-transmissible and universally asymptomatic. It has been confirmed that more than 90% of the population is latently infected with EBV for life. EBV can cause a variety of related cancers, such as nasopharyngeal carcinoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Currently, many clinical studies have demonstrated that EBV-specific cytotoxic T lymphocytes and other cell therapies can be safely and effectively transfused to prevent and treat some diseases caused by EBV. This review will mainly focus on discussing EBV-specific cytotoxic T lymphocytes and will touch on therapeutic EBV vaccines and chimeric antigen receptor T-cell therapy briefly.

Post-transplant lymphoproliferative disorder: Update on treatment and novel therapies

Post-transplant lymphoproliferative disorder (PTLD) is rare and heterogeneous lymphoid proliferations that occur as a result of immunosuppression following solid organ transplant (SOT) and haematopoietic stem cell transplant (HSCT) with the majority being driven by EBV. Although some histologies are similar to lymphoid neoplasms seen in immunocompetent patients, treatment of PTLD may be different due to difference in pathobiology and higher risk of treatment complications. The most common treatment approach in SOT PTLD after failing immunosuppression reduction (RIS) takes into consideration a risk-stratified sequential algorithm with rituximab +/- chemotherapy based on phase 2 studies. In HSCT PTLD, RIS alone and chemotherapy are usually ineffective making rituximab +/- RIS as the gold standard of frontline treatment. In this review, we give an update on the treatment of PTLD beyond RIS. We highlight the most recent studies that attempted to incorporate more aggressive chemotherapy regimens and novel treatments into the traditional risk-stratified sequential approach. We also discuss the role of EBV-cytotoxic T lymphocytes in treatment of EBV-driven PTLD. Other novel agents with potential role in PTLD will be discussed in addition to the challenges that could arise with chimeric antigen receptor T-cell therapy and immune checkpoint inhibitors in this population.

Dual-antigen targeted iPSC-derived chimeric antigen receptor-T cell therapy for refractory lymphoma

We generated dual-antigen receptor (DR) T cells from induced pluripotent stem cells (iPSCs) to mitigate tumor antigen escape. These cells were engineered to express a chimeric antigen receptor (CAR) for the antigen cell surface latent membrane protein 1 (LMP1; LMP1-CAR) and a T cell receptor directed to cell surface latent membrane protein 2 (LMP2), in association with human leucocyte antigen A24, to treat therapy-refractory Epstein-Barr virus-associated lymphomas. We introduced LMP1-CAR into iPSCs derived from LMP2-specific cytotoxic T lymphocytes (CTLs) to generate rejuvenated CTLs (rejTs) active against LMP1 and LMP2, or DRrejTs. All DRrejT-treated mice survived >100 days. Furthermore, DRrejTs rejected follow-up inocula of lymphoma cells, demonstrating that DRrejTs persisted long-term. We also demonstrated that DRrejTs targeting CD19 and LMP2 antigens exhibited a robust tumor suppressive effect and conferred a clear survival advantage. Co-operative antitumor effect and in vivo persistence, with unlimited availability of DRrejT therapy, will provide powerful and sustainable T cell immunotherapy.

Innovative therapeutic concepts of progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is an opportunistic viral disease of the brain-caused by human polyomavirus 2. It affects patients whose immune system is compromised by a corresponding underlying disease or by drugs. Patients with an underlying lymphoproliferative disease have the worst prognosis with a mortality rate of up to 90%. Several therapeutic strategies have been proposed but failed to show any benefit so far. Therefore, the primary therapeutic strategy aims to reconstitute the impaired immune system to generate an effective endogenous antiviral response. Recently, anti-PD-1 antibodies and application of allogeneic virus-specific T cells demonstrated promising effects on the outcome in individual PML patients. This article aims to provide a detailed overview of the literature with a focus on these two treatment approaches.

Identification of protective T-cell antigens for smallpox vaccines

Background aims

E3L is an immediate-early protein of vaccinia virus (VV) that is detected within 0.5 h of infection, potentially before the many immune evasion genes of vaccinia can exert their protective effects. E3L is highly conserved among orthopoxviruses and hence could provide important protective T-cell epitopes that should be retained in any subunit or attenuated vaccine. We have therefore evaluated the immunogenicity of E3L in healthy VV-vaccinated donors.

Methods

Peripheral blood mononuclear cells from healthy volunteers (n = 13) who had previously received a smallpox vaccine (Dryvax) were activated and expanded using overlapping E3L peptides and their function, specificity and antiviral activity was analyzed. E3L-specific T cells were expanded from 7 of 12 (58.3%) vaccinated healthy donors. Twenty-five percent of these produced CD8+ T-cell responses and 87.5% produced CD4+ T cells. We identified epitopes restricted by HLA-B35 and HLA-DR15.

Results

E3L-specific T cells killed peptide-loaded target cells as well as vaccinia-infected cells, but only CD8+ T cells could prevent the spread of infectious virus in virus inhibition assays. The epitopes recognized by E3L-specific T cells were shared with monkeypox, and although there was a single amino acid change in the variola epitope homolog, it was recognized by vaccinia-specific T-cells.

Conclusions

It might be important to include E3L in any deletion mutant or subunit vaccine and E3L could provide a useful antigen to monitor protective immunity in humans.

Pathogen-Specific T Cells Beyond CMV, EBV and Adenovirus

PURPOSE OF REVIEW

Infectious diseases contribute significantly to morbidity and mortality in recipients of allogeneic haematopoietic stem cell transplantation (aHSCT), particularly in the era of highly immunosuppressive transplant regimens and alternate donor transplants. Delayed cellular immune recovery is a major mechanism for the increased risk in these patients. Adoptive cell therapy with ex vivo manipulated pathogen-specific T cells (PSTs) is increasingly taking its place as a treatment strategy using donor-derived or third party-banked cells.

RECENT FINDINGS

The majority of clinical trial data in the form of early-phase studies has been in the prophylaxis or treatment of cytomegalovirus (CMV), Epstein-Barr virus (EBV) and adenovirus (AdV). Advancements in methods to select and enrich PSTs offer the opportunity to target the less common viral pathogens as well as fungi with this technology. Early clinical studies of PSTs targeting polyomaviruses (BK virus and JC virus), human herpesvirus 6 (HHV6), varicella zoster virus (VZV) and Aspergillus spp. have shown promising results in small numbers of patients. Other potential targets include herpes simplex virus (HSV), respiratory viruses and other invasive fungal species. In this review, we describe the burden of disease of this wider spectrum of pathogens, the progress in the development of manufacturing capability, early clinical results and the opportunities and challenges for implementation in the clinic.

T-Cell Receptor Stimulation Enhances the Expansion and Function of CD19 Chimeric Antigen Receptor-Expressing T Cells

PURPOSE

Current protocols for CD19 chimeric antigen receptor-expressing T cells (CD19.CAR-T cells) require recipients to tolerate preinfusion cytoreductive chemotherapy, and the presence of sufficient target antigen on normal or malignant B cells.

PATIENTS AND METHODS

We investigated whether additional stimulation of CD19.CAR-T cells through their native receptors can substitute for cytoreductive chemotherapy, inducing expansion and functional persistence of CD19.CAR-T even in patients in remission of B-cell acute lymphocytic leukemia. We infused a low dose of CD19.CAR-modified virus-specific T cells (CD19.CAR-VST) without prior cytoreductive chemotherapy into 8 patients after allogeneic stem cell transplant.

RESULTS

Absent virus reactivation, we saw no CD19.CAR-VST expansion. In contrast, in patients with viral reactivation, up to 30,000-fold expansion of CD19.CAR-VSTs was observed, with depletion of CD19⁺ B cells. Five patients remain in remission at 42-60+ months.

CONCLUSIONS

Dual T-cell receptor and CAR stimulation can thus potentiate effector cell expansion and CAR-target cell killing, even when infusing low numbers of effector cells without cytoreduction.

EBV/LMP-specific T cells maintain remissions of T- and B-cell EBV lymphomas after allogeneic bone marrow transplantation

Autologous T cells targeting Epstein-Barr virus (EBV) latent membrane proteins (LMPs) have shown safety and efficacy in the treatment of patients with type 2 latency EBV-associated lymphomas for whom standard therapies have failed, including high-dose chemotherapy followed by autologous stem-cell rescue. However, the safety and efficacy of allogeneic donor-derived LMP-specific T cells (LMP-Ts) have not been established for patients who have undergone allogeneic hematopoietic stem-cell transplantation (HSCT). Therefore, we evaluated the safety and efficacy of donor-derived LMP-Ts in 26 patients who had undergone allogeneic HSCT for EBV-associated natural killer/T-cell or B-cell lymphomas. Seven patients received LMP-Ts as therapy for active disease, and 19 were treated with adjuvant therapy for high-risk disease. There were no immediate infusion-related toxicities, and only 1 dose-limiting toxicity potentially related to T-cell infusion was seen. The 2-year overall survival (OS) was 68%. Additionally, patients who received T-cell therapy while in complete remission after allogeneic HSCT had a 78% OS at 2 years. Patients treated for B-cell disease (n = 10) had a 2-year OS of 80%. Patients with T-cell disease had a 2-year OS of 60%, which suggests an improvement compared with published posttransplantation 2-year OS rates of 30% to 50%. Hence, this study shows that donor-derived LMP-Ts are a safe and effective therapy to prevent relapse after transplantation in patients with B cell- or T cell-derived EBV-associated lymphoma or lymphoproliferative disorder and supports the infusion of LMP-Ts as adjuvant therapy to improve outcomes in the posttransplantation setting. These trials were registered at www.clinicaltrials.gov as #NCT00062868 and #NCT01956084.

Transposon-modified antigen-specific T lymphocytes for sustained therapeutic protein delivery in vivo

A cell therapy platform permitting long-term delivery of peptide hormones in vivo would be a significant advance for patients with hormonal deficiencies. Here we report the utility of antigen-specific T lymphocytes as a regulatable peptide delivery platform for in vivo therapy. piggyBac transposon modification of murine cells with luciferase allows us to visualize T cells after adoptive transfer. Vaccination stimulates long-term T-cell engraftment, persistence, and transgene expression enabling detection of modified cells up to 300 days after adoptive transfer. We demonstrate adoptive transfer of antigen-specific T cells expressing erythropoietin (EPO) elevating the hematocrit in mice for more than 20 weeks. We extend our observations to human T cells demonstrating inducible EPO production from Epstein-Barr virus (EBV) antigen-specific T lymphocytes. Our results reveal antigen-specific T lymphocytes to be an effective delivery platform for therapeutic molecules such as EPO in vivo, with important implications for other diseases that require peptide therapy.

Vaccination Targeting Native Receptors to Enhance the Function and Proliferation of Chimeric Antigen Receptor (CAR)-Modified T Cells

Purpose: The multiple mechanisms used by solid tumors to suppress tumor-specific immune responses are a major barrier to the success of adoptively transferred tumor-specific T cells. As viruses induce potent innate and adaptive immune responses, we hypothesized that the immunogenicity of viruses could be harnessed for the treatment of solid tumors if virus-specific T cells (VST) were modified with tumor-specific chimeric antigen receptors (CAR). We tested this hypothesis using VZV-specific T cells (VZVST) expressing a CAR for GD2, a disialoganglioside expressed on neuroblastoma and certain other tumors, so that the live-attenuated VZV vaccine could be used for in vivo stimulation.Experimental Design: We generated GMP-compliant, GD2.CAR-modified VZVSTs from healthy donors and cancer patients by stimulation of peripheral blood mononuclear cells with overlapping peptide libraries spanning selected VZV antigens, then tested their ability to recognize and kill GD2- and VZV antigen-expressing target cells.Results: Our choice of VZV antigens was validated by the observation that T cells specific for these antigens expanded in vivo after VZV vaccination. VZVSTs secreted cytokines in response to VZV antigens, killed VZV-infected target cells and limited infectious virus spread in autologous fibroblasts. However, while GD2.CAR-modified VZVSTs killed neuroblastoma cell lines on their first encounter, they failed to control tumor cells in subsequent cocultures. Despite this CAR-specific dysfunction, CAR-VZVSTs retained functional specificity for VZV antigens via their TCRs and GD2.CAR function was partially rescued by stimulation through the TCR or exposure to dendritic cell supernatants.Conclusions: Vaccination via the TCR may provide a means to reactivate CAR-T cells rendered dysfunctional by the tumor microenvironment (NCT01953900). Clin Cancer Res; 23(14); 3499-509. ©2017 AACR.

EBV-Directed T Cell Therapeutics for EBV-Associated Lymphomas

Epstein Barr virus (EBV) is a human gamma herpes virus that establishes latency in B cells after primary infection. EBV generally only causes a mild, self-limiting viral illness but is also associated with several malignancies including posttransplantation lymphoproliferative disorder in the immunosuppressed host as well as Hodgkin and non-Hodgkin lymphoma in the immune competent host. The expression of EBV antigens by lymphoma has important applications as targets for adoptive T cell therapy. However, as many lymphomas only express subdominant EBV antigens that are less immunogenic, novel strategies are needed to manufacture EBV-specific T cell products specific for Latent Membrane Protein 1 (LMP1) and LMP2, which are expressed in lymphomas with type II and III latency. While several techniques for manufacturing EBV-CTLs are described in the literature, this chapter focuses on one method for generating Good Manufacturing Practice (GMP)-compliant EBV-specific T cell products that are enriched with LMP1 and LMP2.

Neutrophil elastase enhances antigen presentation by upregulating human leukocyte antigen class I expression on tumor cells

Neutrophil elastase (NE) is an innate immune cell-derived inflammatory mediator that we have shown increases the presentation of tumor-associated peptide antigens in breast cancer. In this study, we extend these observations to show that NE uptake has a broad effect on enhancing antigen presentation by breast cancer cells. We show that NE increases human leukocyte antigen (HLA) class I expression on the surface of breast cancer cells in a concentration and time-dependent manner. HLA class I upregulation requires internalization of enzymatically active NE. Western blots of NE-treated breast cancer cells confirm that the expression of total HLA class I as well as the antigen-processing machinery proteins TAP1, LMP2, and calnexin does not change following NE treatment. This suggests that NE does not increase the efficiency of antigen processing; rather, it mediates the upregulation of HLA class I by stabilizing and reducing membrane recycling of HLA class I molecules. Furthermore, the effects of NE extend beyond breast cancer since the uptake of NE by EBV-LCL increases the presentation of HLA class I-restricted viral peptides, as shown by their increased sensitivity to lysis by EBV-specific CD8+ T cells. Together, our results show that NE uptake increases the responsiveness of breast cancer cells to adaptive immunity by broad upregulation of membrane HLA class I and support the conclusion that the innate inflammatory mediator NE enhances tumor cell recognition and increases tumor sensitivity to the host adaptive immune response.

Adoptive immunotherapy for primary immunodeficiency disorders with virus-specific T lymphocytes

BACKGROUND

Viral infections are a leading fatal complication for patients with primary immunodeficiencies (PIDs) who require hematopoietic stem cell transplantation (HSCT). Use of virus-specific T lymphocytes (VSTs) has been successful for the treatment and prevention of viral infections after HSCT for malignant and nonmalignant conditions. Here we describe the clinical use of VSTs in patients with PIDs at 4 centers.

OBJECTIVE

We sought to evaluate the safety and efficacy of VSTs for treatment of viral infections in patients with PIDs.

METHODS

Patients with PIDs who have received VST therapy on previous or current protocols were reviewed in aggregate. Clinical information, including transplantation details, viral infections, and use of antiviral and immunosuppressive pharmacotherapy, were evaluated. Data regarding VST production, infusions, and adverse reactions were compared.

RESULTS

Thirty-six patients with 12 classes of PID diagnoses received 37 VST products before or after HSCT. Twenty-six (72%) patients had received a diagnosis of infection with cytomegalovirus, EBV, adenovirus, BK virus, and/or human herpesvirus 6. Two patients were treated before HSCT because of EBV-associated lymphoproliferative disease. Partial or complete responses against targeted viruses occurred in 81% of patients overall. Time to response varied from 2 weeks to 3 months (median, 28 days). Overall survival at 6 months after therapy was 80%. Four patients had graft-versus-host disease in the 45 days after VST infusion, which in most cases was therapy responsive.

CONCLUSION

VSTs derived from either stem cell donors or third-party donors are likely safe and effective for the treatment of viral infections in patients with PIDs.

Virus-specific T-cell therapy in solid organ transplantation

This article reviews the current state of T-cell therapy as therapeutic option for virus-associated diseases against the background of the most common viral complications and their standard treatment regimens after SOT. The available data of clinical T-cell trials in SOT are summarized. References to the hematopoietic stem cell transplantation are made if applicable data in SOT are not available and their content was considered likewise valid for cell therapy in SOT. Moreover, aspects of different manufacturing approaches including beneficial product characteristics and the importance of GMP compliance are addressed.

Heparanase promotes tumor infiltration and antitumor activity of CAR-redirected T lymphocytes

Adoptive transfer of chimeric antigen receptor (CAR)-redirected T lymphocytes (CAR-T cells) has had less striking effects in solid tumors^1–3 than in lymphoid malignancies^{4, 5}. Although active tumor-mediated immunosuppression may play a role in limiting efficacy⁶, functional changes in T lymphocytes following their ex vivo manipulation may also account for cultured CAR-T cells’ reduced ability to penetrate stroma-rich solid tumors. We therefore studied the capacity of human in vitro-cultured CAR-T cells to degrade components of the extracellular matrix (ECM). In contrast to freshly isolated T lymphocytes, we found that in vitro-cultured T lymphocytes lack expression of the enzyme heparanase (HPSE) that degrades heparan sulphate proteoglycans, which are main components of ECM. We found that HPSE mRNA is down regulated in in vitro-expanded T cells, which may be a consequence of p53 binding to the HPSE gene promoter. We therefore engineered CAR-T cells to express HPSE and showed improved capacity to degrade ECM, which promoted tumor T-cell infiltration and antitumor activity. Employing this strategy may enhance the activity of CAR-T cells in individuals with stroma-rich solid tumors.

Manufacture of tumor- and virus-specific T lymphocytes for adoptive cell therapies

Adoptive transfer of tumor-infiltrating lymphocytes (TILs) and genetically engineered T lymphocytes expressing chimeric antigen receptors (CARs) or conventional alpha/beta T-cell receptors (TCRs), collectively termed adoptive cell therapy (ACT), is an emerging novel strategy to treat cancer patients. Application of ACT has been constrained by the ability to isolate and expand functional tumor-reactive T cells. The transition of ACT from a promising experimental regimen to an established standard of care treatment relies largely on the establishment of safe, efficient, robust and cost-effective cell manufacturing protocols. The manufacture of cellular products under current good manufacturing practices (cGMPs) has a critical role in the process. Herein, we review current manufacturing methods for the large-scale production of clinical-grade TILs, virus-specific and genetically modified CAR or TCR transduced T cells in the context of phase I/II clinical trials as well as the regulatory pathway to get these complex personalized cellular products to the clinic.

Antiviral T-cell therapy

Serious viral infections are a common cause of morbidity and mortality after allogeneic stem cell transplantation. They occur in the majority of allograft recipients and are fatal in 17–20%. These severe infections may be prolonged or recurrent and add substantially to the cost, both human and financial, of the procedure. Many features of allogeneic stem cell transplantation contribute to this high rate of viral disease. The cytotoxic and immunosuppressive drugs administered pretransplant to eliminate the host hematopoietic/immune system and any associated malignancy, the delay in recapitulating immune ontogeny post‐transplant, the immunosuppressive drugs given to prevent graft versus host disease (GvHD), and the effects of GvHD itself, all serve to make stem cell transplant recipients vulnerable to disease from endogenous (latent) and exogenous (community) viruses, and to be incapable of controlling them as quickly and effectively as most normal individuals.

Early transduction produces highly functional chimeric antigen receptor-modified virus-specific T-cells with central memory markers: a Production Assistant for Cell Therapy (PACT) translational application

BACKGROUND

Virus-specific T-cells (VSTs) proliferate exponentially after adoptive transfer into hematopoietic stem cell transplant (HSCT) recipients, eliminate virus infections, then persist and provide long-term protection from viral disease. If VSTs behaved similarly when modified with tumor-specific chimeric antigen receptors (CARs), they should have potent anti-tumor activity. This theory was evaluated by Cruz et al. in a previous clinical trial with CD19.CAR-modified VSTs, but there was little apparent expansion of these cells in patients. In that study, VSTs were gene-modified on day 19 of culture and we hypothesized that by this time, sufficient T-cell differentiation may have occurred to limit the subsequent proliferative capacity of the transduced T-cells. To facilitate the clinical testing of this hypothesis in a project supported by the NHLBI-PACT mechanism, we developed and optimized a good manufacturing practices (GMP) compliant method for the early transduction of VSTs directed to Epstein-Barr virus (EBV), Adenovirus (AdV) and cytomegalovirus (CMV) using a CAR directed to the tumor-associated antigen disialoganglioside (GD2).

RESULTS

Ad-CMVpp65-transduced EBV-LCLs effectively stimulated VSTs directed to all three viruses (triVSTs). Transduction efficiency on day three was increased in the presence of cytokines and high-speed centrifugation of retroviral supernatant onto retronectin-coated plates, so that under optimal conditions up to 88% of tetramer-positive VSTs expressed the GD2.CAR. The average transduction efficiency of early-and late transduced VSTs was 55 ± 4% and 22 ± 5% respectively, and early-transduced VSTs maintained higher frequencies of T cells with central memory or intermediate memory phenotypes. Early-transduced VSTs also had higher proliferative capacity and produced higher levels of TH1 cytokines IL-2, TNF-α, IFN-γ, MIP-1α, MIP-1β and other cytokines in vitro.

CONCLUSIONS

We developed a rapid and GMP compliant method for the early transduction of multivirus-specific T-cells that allowed stable expression of high levels of a tumor directed CAR. Since a proportion of early-transduced CAR-VSTs had a central memory phenotype, they should expand and persist in vivo, simultaneously protecting against infection and targeting residual malignancy. This manufacturing strategy is currently under clinical investigation in patients receiving allogeneic HSCT for relapsed neuroblastoma and B-cell malignancies (NCT01460901 using a GD2.CAR and NCT00840853 using a CD19.CAR).

K562-Derived Whole-Cell Vaccine Enhances Antitumor Responses of CAR-Redirected Virus-Specific Cytotoxic T Lymphocytes In Vivo

PURPOSE

Adoptive transfer of Epstein-Barr virus (EBV)-specific and cytomegalovirus (CMV)-specific cytotoxic T cells (CTL) genetically modified to express a chimeric antigen receptor (CAR) induces objective tumor responses in clinical trials. In vivo expansion and persistence of these cells are crucial to achieve sustained clinical responses. We aimed to develop an off-the-shelf whole-cell vaccine to boost CAR-redirected virus-specific CTLs in vivo after adoptive transfer. As proof of principle, we validated our vaccine approach by boosting CMV-specific CTLs (CMV-CTLs) engineered with a CAR that targets the GD2 antigen.

EXPERIMENTAL DESIGN

We generated the whole-cell vaccine by engineering the K562 cell line to express the CMV-pp65 protein and the immune stimulatory molecules CD40L and OX40L. Single-cell-derived clones were used to stimulate CMV-CTLs in vitro and in vivo in a xenograft model. We also assessed whether the in vivo boosting of CAR-redirected CMV-CTLs with the whole-cell vaccine enhances the antitumor responses. Finally, we addressed potential safety concerns by including the inducible safety switch caspase9 (iC9) gene in the whole-cell vaccine.

RESULTS

We found that K562-expressing CMV-pp65, CD40L, and OX40L effectively stimulate CMV-specific responses in vitro by promoting antigen cross-presentation to professional antigen-presenting cells (APCs). Vaccination also enhances antitumor effects of CAR-redirected CMV-CTLs in xenograft tumor models. Activation of the iC9 gene successfully induces growth arrest of engineered K562 implanted in mice.

CONCLUSIONS

Vaccination with a whole-cell vaccine obtained from K562 engineered to express CMV-pp65, CD40L, OX40L and iC9 can safely enhance the antitumor effects of CAR-redirected CMV-CTLs.

Epstein Barr virus-associated lymphoproliferative diseases: the virus as a therapeutic target

Epstein Barr virus (EBV)-associated lymphoproliferative diseases (LPDs) express all EBV latent antigens (type III latency) in immunodeficient patients and limited antigens (type I and II latencies) in immunocompetent patients. Post-transplantation lymphoproliferative disease (PTLD) is the prototype exhibiting type III EBV latency. Although EBV antigens are highly immunogenic, PTLD cell proliferation remains unchecked because of the underlying immunosuppression. The restoration of anti-EBV immunity by EBV-specific T cells of either autologous or allogeneic origin has been shown to be safe and effective in PTLDs. Cellular therapy can be improved by establishing a bank of human leukocyte antigen-characterized allogeneic EBV-specific T cells. In EBV+ LPDs exhibiting type I and II latencies, the use of EBV-specific T cells is more limited, although the safety and efficacy of this therapy have also been demonstrated. The therapeutic role of EBV-specific T cells in EBV+ LPDs needs to be critically reappraised with the advent of monoclonal antibodies and other targeted therapy. Another strategy involves the use of epigenetic approaches to induce EBV to undergo lytic proliferation when expression of the viral thymidine kinase renders host tumor cells susceptible to the cytotoxic effects of ganciclovir. Finally, the prophylactic use of antiviral drugs to prevent EBV reactivation may decrease the occurrence of EBV+ LPDs.

Complementation of antigen-presenting cells to generate T lymphocytes with broad target specificity

Antigen-specific T cells provide a therapy for cancer that is highly specific, self-replicating, and potentially devoid of toxicity. Ideally, tumor-specific T cells should recognize multiple epitopes on multiple antigens to prevent tumor immune escape. However the large-scale expansion of such broad-spectrum T cells has been limited by the availability of potent autologous antigen-presenting cells that can present antigens on the polymorphic array of each patient's HLA allotype. We evaluated a novel antigen-presenting complex (KATpx) in which antigens in the form of peptide libraries can be presented by autologous activated T cells, whereas costimulation is complemented in trans by an HLA-negative K562 cell line genetically modified to express CD80, CD83, CD86, and 4-1BBL (K562cs). The additional costimulation provided by K562cs significantly enhanced T-cell expansion in culture over autologous activated T cells alone while maintaining antigen specificity. We validated this antigen-presenting system by generating Epstein-Barr virus (EBV) antigen-specific T cells from healthy donors and from patients with EBV-positive malignancies including nasopharyngeal carcinoma and multiply relapsed EBV-positive lymphoma. These T cells were specific for EBNA1, LMP1, and LMP2, the viral antigens expressed in these type 2 latency EBV-associated malignancies. The KATpx system consistently activated and expanded antigen-specific T cells both from healthy donors and from 5 of 6 patients with lymphoma and 6 of 6 with nasopharyngeal carcinoma, while simplifying the process for generating APCs by eliminating the need for live virus (EBV) or viral vectors to force expression of transgenic EBV antigens. Hence, KATpx provides a robust, reliable, and scalable process to expand tumor-directed T cells for the treatment of virus-associated cancers.

T lymphocytes targeting native receptors

The adoptive transfer of T cells specific for native tumor antigens (TAs) is an increasingly popular cancer treatment option because of the ability of these cells to discriminate between normal and tumor tissues and the corresponding lack of short or long-term toxicities. Infusions of antigen-specific CD4(+) and CD8(+) T cells targeting viral antigens derived from Epstein-Barr virus (EBV) induce sustained complete tumor remissions in patients with highly immunogenic tumors such as post-transplant lymphoproliferative disease, although resistance occurred when the infused T-cell population had restricted antigen specificity. T cells specific for EBV antigens have also produced complete remissions of EBV-positive nasopharyngeal carcinomas and lymphomas developing in immunocompetent individuals, even though in these patients tumor survival is dependent on their ability to evade T-cell immunity. Adapting this strategy to non-viral tumors is more challenging, as the target antigens expressed are less immunogenic and the tumors lack the potent danger signals that are characteristic of viruses. The goals of current studies are to define conditions that promote expansion of antigen-specific T cells ex vivo and to ensure their in vivo persistence and survival by combining with maneuvers such as lymphodepletion, checkpoint inhibition, cytokine infusions, or genetic manipulations. More pragmatic goals are to streamline manufacturing to facilitate the transition of these therapies to late phase trials and to evaluate closely histocompatibility antigen (HLA)-matched banked antigen-specific T cells so that T-cell therapies can be made more broadly available.

Cellular immunotherapy for patients with reactivation of JC and BK polyomaviruses after transplantation

Immunosuppression of patients after hematopoietic stem cell or kidney transplantation potentially leads to reactivation of JC and BK polyomaviruses. In hematopoietic stem cell transplantation, the reactivation rate of BKV can be up to 60%, resulting in severe complications of the urogenital tract, particularly hemorrhagic cystitis and renal dysfunction. After kidney transplantation, BKV reactivation can cause a loss of the graft. JCV can cause progressive multifocal leukoencephalopathy, a lethal disease. Adoptive transfer of donor-derived polyomavirus-specific T cells is an attractive and promising treatment that restores virus-specific cellular immunity. Pioneering work in the early 1990s on the reconstitution of cellular immunity against cytomegalovirus and recent development in the field of monitoring and isolation of antigen-specific T cells paved the way toward a personalized T-cell therapy. Multimer technology and magnetic beads are available to produce untouched T cells in a single-step, good manufacturing practice-compliant procedure. Another exciting aspect of T-cell therapy against polyomaviruses is the fact that both JCV and BKV can be targeted simultaneously because of their high sequence homology. Finally, "designer T cells" can be redirected to recognize polyomavirus antigens with high-affinity T-cell receptors. This review summarizes the state-of-the art technologies and gives an outlook of future developments in the field.

Virus and autoantigen-specific CD4+ T cells are key effectors in a SCID mouse model of EBV-associated post-transplant lymphoproliferative disorders

Polyclonal Epstein-Barr virus (EBV)-infected B cell line (lymphoblastoid cell lines; LCL)-stimulated T-cell preparations have been successfully used to treat EBV-positive post-transplant lymphoproliferative disorders (PTLD) in transplant recipients, but function and specificity of the CD4+ component are still poorly defined. Here, we assessed the tumor-protective potential of different CD4+ T-cell specificities in a PTLD-SCID mouse model. Injection of different virus-specific CD4+ T-cell clones showed that single specificities were capable of prolonging mouse survival and that the degree of tumor protection directly correlated with recognition of target cells in vitro. Surprisingly, some CD4+ T-cell clones promoted tumor development, suggesting that besides antigen recognition, still elusive functional differences exist among virus-specific T cells. Of several EBV-specific CD4+ T-cell clones tested, those directed against virion antigens proved most tumor-protective. However, enriching these specificities in LCL-stimulated preparations conferred no additional survival benefit. Instead, CD4+ T cells specific for unknown, probably self-antigens were identified as principal antitumoral effectors in LCL-stimulated T-cell lines. These results indicate that virion and still unidentified cellular antigens are crucial targets of the CD4+ T-cell response in this preclinical PTLD-model and that enriching the corresponding T-cell specificities in therapeutic preparations may enhance their clinical efficacy. Moreover, the expression in several EBV-negative B-cell lymphoma cell lines implies that these putative autoantigen(s) might also qualify as targets for T-cell-based immunotherapy of virus-negative B cell malignancies.

Epstein-Barr virus infection induces indoleamine 2,3-dioxygenase expression in human monocyte-derived macrophages through p38/mitogen-activated protein kinase and NF-κB pathways: impairment in T cell functions

Epstein-Barr virus (EBV) infection has been observed in tumor-infiltrated macrophages, but its infection effects on macrophage immune functions are poorly understood. Here, we showed that some macrophages in the tumor stroma of nasopharyngeal carcinoma (NPC) tissue expressed the immunosuppressive protein indoleamine 2,3-dioxygenase (IDO) more strongly than did tumor cells. EBV infection induced mRNA, protein, and enzymatic activity of IDO in human monocyte-derived macrophages (MDMs). Infection increased the production of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), whereas the neutralizing antibodies against TNF-α and IL-6 inhibited IDO induction. EBV infection also activated the mitogen-activated protein kinase (MAPK) p38 and NF-κB, and the inhibition of these two pathways with SB202190 and SN50 almost abrogated TNF-α and IL-6 production and inhibited IDO production. Moreover, the activation of IDO in response to EBV infection of MDMs suppressed the proliferation of T cells and impaired the cytotoxic activity of CD8(+) T cells, whereas the inhibition of IDO activity with 1-methyl-l-tryptophan (1-MT) did not affect T cell proliferation and function. These findings indicate that EBV-induced IDO expression in MDMs is substantially mediated by IL-6- and TNF-α-dependent mechanisms via the p38/MAPK and NF-κB pathways, suggesting that a possible role of EBV-mediated IDO expression in tumor stroma of NPC may be to create a microenvironment of suppressed T cell immune responses.

IMPORTANCE

CD8(+) cytotoxic T lymphocytes (CTLs) play an important role in the control of viral infections and destroy tumor cells. Activation of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) in cancer tissues facilitates immune escape by the impairment of CTL functions. IDO expression was observed in some macrophages of the tumor stroma of nasopharyngeal carcinoma (NPC) tissue, and IDO could be induced in Epstein-Barr virus (EBV)-infected human monocyte-derived macrophages (MDMs). NPC cells and macrophages have been found to produce IDO in a gamma interferon (IFN-γ)-dependent manner. Instead, EBV-induced IDO expression in MDMs is substantially mediated by IL-6- and TNF-α-dependent mechanisms via the p38/MAPK and NF-κB pathways, which suppressed the proliferation of T cells and impaired the cytotoxic activity of CD8(+) T cells. This finding provides a new interpretation of the mechanism of immune escape of EBV and shows the immunosuppressive role of EBV-mediated IDO expression in tumor stroma of NPC.

Infusion of donor-derived CD19-redirected virus-specific T cells for B-cell malignancies relapsed after allogeneic stem cell transplant: a phase 1 study

Autologous T cells expressing a CD19-specific chimeric antigen receptor (CD19.CAR) are active against B-cell malignancies, but it is unknown whether allogeneic CD19.CAR T cells are safe or effective. After allogeneic hematopoietic stem cell transplantation (HSCT), infused donor-derived virus-specific T cells (VSTs) expand in vivo, persist long term, and display antiviral activity without inducing graft-vs-host disease; therefore, we determined whether donor VSTs, engineered to express CD19.CAR, retained the characteristics of nonmanipulated allogeneic VSTs while gaining antitumor activity. We treated 8 patients with allogeneic (donor-derived) CD19.CAR-VSTs 3 months to 13 years after HSCT. There were no infusion-related toxicities. VSTs persisted for a median of 8 weeks in blood and up to 9 weeks at disease sites. Objective antitumor activity was evident in 2 of 6 patients with relapsed disease during the period of CD19.CAR-VST persistence, whereas 2 patients who received cells while in remission remain disease free. In 2 of 3 patients with viral reactivation, donor CD19.CAR-VSTs expanded concomitantly with VSTs. Hence CD19.CAR-VSTs display antitumor activity and, because their number may be increased in the presence of viral stimuli, earlier treatment post-HSCT (when lymphodepletion is greater and the incidence of viral infection is higher) or planned vaccination with viral antigens may enhance disease control.

Robust and cost effective expansion of human regulatory T cells highly functional in a xenograft model of graft-versus-host disease

The low frequency of naturally occurring regulatory T cells (nTregs) in peripheral blood and the suboptimal protocols available for their ex vivo expansion limit the development of clinical trials based on the adoptive transfer of these cells. We have, therefore, generated a simplified, robust and cost-effective platform for the large-scale expansion of nTregs using a gas permeable static culture flask (G-Rex) in compliance with Good Manufacturing Practice. More than 10(9) putative Tregs co-expressing CD25 and CD4 molecules (92 ± 5%) and FoxP3 (69 ± 19%) were obtained within 21 days of culture. Expanded Tregs showed potent regulatory activity in vitro (80 ± 13% inhibition of CD8(+) cell division) and in vivo (suppression or delay of graft-versus-host disease in a xenograft mouse model) indicating that the cost-effective and simplified production of nTregs we propose will facilitate the implementation of clinical trials based on their adoptive transfer.

T-cell therapy in the treatment of post-transplant lymphoproliferative disease

Post-transplant lymphoproliferative diseases (PTLD) associated with Epstein-Barr virus (EBV) infection often develop after organ and haematopoietic stem-cell transplantation. These lymphoproliferative diseases are tumours that usually express all latent EBV viral proteins, and are therefore amenable to T-cell-based immune therapies, such as donor lymphocyte infusions and the adoptive transfer of EBV-specific cytotoxic T lymphocytes. In this Review, we describe current approaches of T-cell-based therapies to treat PTLD, and describe strategies that improve the feasibility of such treatment.

EBNA3B-deficient EBV promotes B cell lymphomagenesis in humanized mice and is found in human tumors

Epstein-Barr virus (EBV) persistently infects more than 90% of the human population and is etiologically linked to several B cell malignancies, including Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B cell lymphoma (DLBCL). Despite its growth transforming properties, most immune-competent individuals control EBV infection throughout their lives. EBV encodes various oncogenes, and of the 6 latency-associated EBV-encoded nuclear antigens, only EBNA3B is completely dispensable for B cell transformation in vitro. Here, we report that infection with EBV lacking EBNA3B leads to aggressive, immune-evading monomorphic DLBCL-like tumors in NOD/SCID/γc-/- mice with reconstituted human immune system components. Infection with EBNA3B-knockout EBV (EBNA3BKO) induced expansion of EBV-specific T cells that failed to infiltrate the tumors. EBNA3BKO-infected B cells expanded more rapidly and secreted less T cell-chemoattractant CXCL10, reducing T cell recruitment in vitro and T cell-mediated killing in vivo. B cell lines from 2 EBV-positive human lymphomas encoding truncated EBNA3B exhibited gene expression profiles and phenotypic characteristics similar to those of tumor-derived lines from the humanized mice, including reduced CXCL10 secretion. Screening EBV-positive DLBCL, HL, and BL human samples identified additional EBNA3B mutations. Thus, EBNA3B is a virus-encoded tumor suppressor whose inactivation promotes immune evasion and virus-driven lymphomagenesis.

Targeting cytomegalovirus-infected cells using T cells armed with anti-CD3 × anti-CMV bispecific antibody

Human cytomegalovirus (CMV) reactivation and infection can lead to poor outcomes after allogeneic stem cell transplantation. We hypothesized that anti-CD3 activated T cells (ATCs) armed with chemically heteroconjugated anti-CD3 × polyclonal anti-CMV bispecific antibody (CMVBi) will target and eliminate CMV-infected cells. Arming doses of CMVBi as low as 0.01 ng/10(6) ATCs was able to mediate specific cytotoxicity (SC) directed at CMV-infected target cells significant above unarmed ATCs at mutiplicities of infection (MOI) between 0.01 and 1. At effector-to-target ratios (E:T) of 25:1, 12.5:1, 6.25:1, and 3.125:1, armed ATCs significantly enhanced killing of CMV-infected targets compared with unarmed ATCs. At an MOI of 1.0, the mean % SC directed at CMV-infected targets cells for CMVBi-armed ATCs at E:T of 3.12, 6.25, and 12.5 were 79%, 81%, and 82%, respectively; whereas the mean % SC for unarmed ATCs at the same E:T were all <20%. ATCs, Cytogam(®), or CMVBi alone did not lyse uninfected or CMV-infected targets. Co-cultures of CMVBi-armed ATCs with CMV-infected targets induced cytokine and chemokine release from armed ATCs. This nonmajor histocompatibility complex restricted strategy for targeting CMV could be used to prevent or treat CMV infections after allogeneic stem cell transplantation or organ transplantation.

In Vitro and In Vivo Antitumor Effect of Anti-CD33 Chimeric Receptor-Expressing EBV-CTL against CD33 Acute Myeloid Leukemia

Genetic engineering of T cells with chimeric T-cell receptors (CARs) is an attractive strategy to treat malignancies. It extends the range of antigens for adoptive T-cell immunotherapy, and major mechanisms of tumor escape are bypassed. With this strategy we redirected immune responses towards the CD33 antigen to target acute myeloid leukemia. To improve in vivo T-cell persistence, we modified human Epstein Barr Virus-(EBV-) specific cytotoxic T cells with an anti-CD33.CAR. Genetically modified T cells displayed EBV and HLA-unrestricted CD33 bispecificity in vitro. In addition, though showing a myeloablative activity, they did not irreversibly impair the clonogenic potential of normal CD34(+) hematopoietic progenitors. Moreover, after intravenous administration into CD33(+) human acute myeloid leukemia-bearing NOD-SCID mice, anti-CD33-EBV-specific T cells reached the tumor sites exerting antitumor activity in vivo. In conclusion, targeting CD33 by CAR-modified EBV-specific T cells may provide additional therapeutic benefit to AML patients as compared to conventional chemotherapy or transplantation regimens alone.

PiggyBac-mediated cancer immunotherapy using EBV-specific cytotoxic T-cells expressing HER2-specific chimeric antigen receptor

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) can be modified to function as heterologous tumor directed effector cells that survive longer in vivo than tumor directed T cells without virus specificity, due to chronic stimulation by viral antigens expressed during persistent infection in seropositive individuals. We evaluated the nonviral piggyBac (PB) transposon system as a platform for modifying EBV-CTLs to express a functional human epidermal growth factor receptor 2-specific chimeric antigen receptor (HER2-CAR) thereby directing virus-specific, gene modified CTLs towards HER2-positive cancer cells. Peripheral blood mononuclear cells (PBMCs) were nucleofected with transposons encoding a HER2-CAR and a truncated CD19 molecule for selection followed by specific activation and expansion of EBV-CTLs. HER2-CAR was expressed in ~40% of T cells after CD19 selection with retention of immunophenotype, polyclonality, and function. HER2-CAR-modified EBV-CTLs (HER2-CTLs) killed HER2-positive brain tumor cell lines in vitro, exhibited transient and reversible increases in HER2-CAR expression following antigen-specific stimulation, and stably expressed HER2-CAR beyond 120 days. Adoptive transfer of PB-modified HER2-CTLs resulted in tumor regression in a murine xenograft model. Our results demonstrate that PB can be used to redirect virus-specific CTLs to tumor targets, which should prolong tumor-specific T cell survival in vivo producing more efficacious immunotherapy.

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 role of virus-specific CD4+ T cells in the control of Epstein-Barr virus infection

Epstein-Barr virus (EBV) establishes lifelong persistent infections in humans and has been implicated in the pathogenesis of several human malignancies. Protective immunity against EBV is mediated by T cells, as indicated by an increased incidence of EBV-associated malignancies in immunocompromised patients, and by the successful treatment of EBV-associated post-transplant lymphoproliferative disease (PTLD) in transplant recipients by the infusion of polyclonal EBV-specific T cell lines. To implement this treatment modality as a conventional therapeutic option, and to extend this protocol to other EBV-associated diseases, generic and more direct approaches for the generation of EBV-specific T cell lines enriched in disease-relevant specificities need to be developed. To this aim, we studied the poorly defined EBV-specific CD4+ T cell response during acute and chronic infection.

In vitro and in vivo model of a novel immunotherapy approach for chronic lymphocytic leukemia by anti-CD23 chimeric antigen receptor

Chronic lymphocytic leukemia (CLL) is characterized by an accumulation of mature CD19(+)CD5(+)CD20(dim) B lymphocytes that typically express the B-cell activation marker CD23. In the present study, we cloned and expressed in T lymphocytes a novel chimeric antigen receptor (CAR) targeting the CD23 antigen (CD23.CAR). CD23.CAR(+) T cells showed specific cytotoxic activity against CD23(+) tumor cell lines (average lysis 42%) and primary CD23(+) CLL cells (average lysis 58%). This effect was obtained without significant toxicity against normal B lymphocytes, in contrast to CARs targeting CD19 or CD20 antigens, which are also expressed physiologically by normal B lymphocytes. Moreover, CLL-derived CD23.CAR(+) T cells released inflammatory cytokines (1445-fold more TNF-β, 20-fold more TNF-α, and 4-fold more IFN-γ). IL-2 was also produced (average release 2681 pg/mL) and sustained the antigen-dependent proliferation of CD23.CAR(+) T cells. Redirected T cells were also effective in vivo in a CLL Rag2(-/-)γ(c)(-/-) xenograft mouse model. Compared with mice treated with control T cells, the infusion of CD23.CAR(+) T cells resulted in a significant delay in the growth of the MEC-1 CLL cell line. These data suggest that CD23.CAR(+) T cells represent a selective immunotherapy for the elimination of CD23(+) leukemic cells in patients with CLL.

Allogeneic virus-specific T cells with HLA alloreactivity do not produce GVHD in human subjects

Adoptive transfer of viral antigen-specific memory T cells can reconstitute antiviral immunity, but in a recent report a majority of virus-specific cytotoxic T-lymphocyte (CTL) lines showed in vitro cross-reactivity against allo-human leukocyte antigen (HLA) molecules as measured by interferon-γ secretion. We therefore reviewed our clinical experience with adoptive transfer of allogeneic hematopoietic stem cell transplantation donor-derived virus-specific CTLs in 153 recipients, including 73 instances where there was an HLA mismatch. There was no de novo acute graft-versus-host disease after infusion, and incidence of graft-versus-host disease reactivation was low and not significantly different in recipients of matched or mismatched CTL. However, we found that virus-specific T cell lines recognized up to 10% of a panel of 44 HLA disparate targets, indicating that virus-specific T cells can have cross-reactivity with HLA-mismatched targets in vitro. These data indicate that the adoptive transfer of partially HLA-mismatched virus-specific CTL is safe despite in vitro recognition of recipient HLA molecules.

Comparison of polyclonal expansion methods to improve the recovery of cervical cytobrush-derived T cells from the female genital tract of HIV-infected women

Cervical cytobrushing is a useful and non-invasive method for obtaining mucosal mononuclear cells from the female genital tract, but yields few cells. The aim of this study was to compare in vitro expansion protocols (anti-CD3, anti-CD3/CD28 or Dynal anti-CD3/CD28 beads) and cytokine combinations (IL-2, IL-7 and IL-15) to improve cervical T cell yields and viability. Eighteen HIV-infected women were included in this study to compare methods for polyclonal expansion of T cells from the female genital tract and blood. Comparison of T cell yields, viability and maturational status (by differential staining with CD45RO, CCR7 and CD27) was determined following 7 days of in vitro expansion. Anti-CD3 and IL-2 resulted in a 4.5-fold (range 3.7–5.3) expansion of cervical CD3+ T cells in 7 days compared to day 0. Inclusion of anti-CD28 or addition of IL-7 and IL-15 to this combination did not improve expansion. Culturing cells with Dynal beads (1:1) and IL-2, IL-7 and IL-15 gave rise to the highest yields after 7 days in both blood (7.1-fold) and cervix (5.6-fold). While expansion with anti-CD3 led to the accumulation of effector memory T cells (CD45RO+CCR7−CD27−), expansion with Dynabeads selected for accumulation of central memory T cells (CD45RO+CCR7+CD27+). We conclude that in vitro expansion with Dynabeads (1:1) in the presence of IL-2, IL-7 and IL-15 resulted in the greatest increase in viable T cells from both blood and cytobrush. Irrespective of the expansion method used, the T cell memory profile was altered following expansion.

Derivation of human T lymphocytes from cord blood and peripheral blood with antiviral and antileukemic specificity from a single culture as protection against infection and relapse after stem cell transplantation

Viral infections and leukemic relapse account for the majority of treatment failures in patients with B-cell acute lymphoblastic leukemia (B-ALL) receiving allogeneic hematopoietic stem cell (HSC) or cord blood (CB) transplants. Adoptive transfer of virus-specific cytotoxic T lymphocytes (CTLs) provides protection against common viruses causing serious infections after HSC transplantation without concomitant graft-versus-host disease. We have now generated CTL lines from peripheral blood (PB) or CB units that recognize multiple common viruses and provide antileukemic activity by transgenic expression of a chimeric antigen receptor (CAR) targeting CD19 expressed on B-ALL. PB-derived CAR(+) CTLs produced interferon-gamma (IFNgamma) in response to cytomegalovirus-pp65, adenovirus-hexon, and Epstein-Barr virus pepmixes (from 205 +/- 104 to 1034 +/- 304 spot-forming cells [SFCs]/10(5) T cells) and lysed primary B-ALL blasts in (51)Cr-release assays (mean, 66% +/- 5% specific lysis; effector-target [E/T] ratio, 40:1) and the CD19(+) Raji cell line (mean, 78% +/- 17%) in contrast to nontransduced controls (8% +/- 8% and 3% +/- 2%). CB-derived CAR(+) CTLs showed similar antiviral and antitumor function and both PB and CB CAR(+) CTLs completely eliminated B-ALL blasts over 5 days of coculture. This approach may prove beneficial for patients with high-risk B-ALL who have recently received an HSC or CB transplant and are at risk of infection and relapse.

Functionally active virus-specific T cells that target CMV, adenovirus, and EBV can be expanded from naive T-cell populations in cord blood and will target a range of viral epitopes

The naive phenotype of cord blood (CB) T cells may reduce graft-versus-host disease after umbilical cord blood transplantation, but this naivety and their low absolute numbers also delays immune reconstitution, producing higher infection-related mortality that is predominantly related to CMV, adenovirus (Adv), and EBV. Adoptive immunotherapy with peripheral blood-derived virus-specific cytotoxic T lymphocytes (CTLs) can effectively prevent viral disease after conventional stem cell transplantation, and we now describe the generation of single cultures of CTLs from CB that are specific for multiple viruses. Using EBV-infected B cells transduced with a clinical-grade Ad5f35CMVpp65 adenoviral vector as sources of EBV, Adv, and CMV antigens, we expanded virus-specific T cells even from CB T cells with a naive phenotype. After expansion, each CTL culture contained both CD8(+) and CD4(+) T-cell subsets, predominantly of effector memory phenotype. Each CTL culture also had HLA-restricted virus-specific cytotoxic effector function against EBV, CMV, and Adv targets. The CB CTLs recognized multiple viral epitopes, including CD4-restricted Adv-hexon epitopes and immunosubdominant CD4- and CD8-restricted CMVpp65 epitopes. Notwithstanding their naive phenotype, it is therefore possible to generate trivirus-specific CTLs in a single culture of CB, which may be of value to prevent or treat viral disease in CB transplant recipients. This study is registered at www.clinicaltrials.gov as NCT00078533.

Developing T-cell therapies for cancer in an academic setting

T-cell immunotherapies have great potential because of their exquisite targeting ability and high efficacy, but are more complex to implement since they do not readily fit the pharmaceutical model. Nonetheless, recent improvements in gene-transfer technology allow T cells directed to tumor-associated antigens to effectively eradicate even bulky malignancies. T lymphocytes also have the potential to target tumor stem cells, provided the target antigens are appropriately identified and expressed on the components used to generate the effector T-cells. Numerous problems remain before these approaches can be widely implemented, but as the success rate increases, willingness to commit the necessary resources will correspondingly increase.

Standardized and highly efficient expansion of Epstein-Barr virus-specific CD4+ T cells by using virus-like particles

Epstein-Barr virus (EBV)-specific T-cell lines generated by repeated stimulation with EBV-immortalized lymphoblastoid B-cell lines (LCL) have been successfully used to treat EBV-associated posttransplant lymphoproliferative disease (PTLD) in hematopoietic stem cell transplant recipients. However, PTLD in solid-organ transplant recipients and other EBV-associated malignancies respond less efficiently to this adoptive T-cell therapy. LCL-stimulated T-cell preparations are polyclonal and contain CD4(+) and CD8(+) T cells, but the composition varies greatly between lines. Because T-cell lines with higher CD4(+) T-cell proportions show improved clinical efficacy, we assessed which factors might compromise the expansion of this T-cell population. Here we show that spontaneous virus production by LCL and, hence, the presentation of viral antigens varies intra- and interindividually and is further impaired by acyclovir treatment of LCL. Moreover, the stimulation of T cells with LCL grown in medium supplemented with fetal calf serum (FCS) caused the expansion of FCS-reactive CD4(+) T cells, whereas human serum from EBV-seropositive donors diminished viral antigen presentation. To overcome these limitations, we used peripheral blood mononuclear cells pulsed with nontransforming virus-like particles as antigen-presenting cells. This strategy facilitated the specific and rapid expansion of EBV-specific CD4(+) T cells and, thus, might contribute to the development of standardized protocols for the generation of T-cell lines with improved clinical efficacy.

Complete responses of relapsed lymphoma following genetic modification of tumor-antigen presenting cells and T-lymphocyte transfer

Epstein-Barr virus (EBV)-associated tumors developing in immunocompetent individuals present a challenge to immunotherapy, since they lack expression of immunodominant viral antigens. However, the tumors consistently express viral proteins including LMP2, which are immunologically "weak" but may nonetheless be targets for immune T cells. We previously showed that a majority of cytotoxic T lymphocytes (CTLs) reactivated using EBV-transformed B-lymphoblastoid cells lines (LCLs) contained minor populations of LMP2-specific T cells and homed to tumor sites. However, they did not produce remissions in patients with bulky disease. We have now used gene transfer into antigen-presenting cells (APCs) to augment the expression and immunogenicity of LMP2. These modified APCs increased the frequency of LMP2-specific CTLs by up to 100-fold compared with unmodified LCL-APCs. The LMP2-specific population expanded and persisted in vivo without adverse effects. Nine of 10 patients treated in remission of high-risk disease remain in remission, and 5 of 6 patients with active relapsed disease had a tumor response, which was complete in 4 and sustained for more than 9 months. It is therefore possible to generate immune responses to weak tumor antigens by ex vivo genetic modification of APCs and the CTLs so produced can have substantial antitumor activity. This study is registered at http://www.cancer.gov/clinicaltrials (protocol IDs: BCM-H-9936, NCT00062868, NCT00070226).

Characterization of latent membrane protein 2 specificity in CTL lines from patients with EBV-positive nasopharyngeal carcinoma and lymphoma

Viral proteins expressed by EBV-associated tumors provide target Ags for immunotherapy. Adoptive T cell therapy has proven effective for posttransplant EBV-associated lymphoma in which all EBV latent Ags are expressed (type III latency). Application of immunotherapeutic strategies to tumors such as nasopharyngeal carcinoma and Hodgkin's lymphoma that have a restricted pattern of EBV Ag expression (type II latency) is under investigation. Potential EBV Ag targets for T cell therapy expressed by these tumors include latent membrane proteins (LMP) 1 and 2. A broad panel of epitopes must be identified from these target Ags to optimize vaccination strategies and facilitate monitoring of tumor-specific T cell populations after immunotherapeutic interventions. To date, LMP2 epitopes have been identified for only a limited number of HLA alleles. Using a peptide library spanning the entire LMP2 sequence, 25 CTL lines from patients with EBV-positive malignancies expressing type II latency were screened for the presence of LMP2-specific T cell populations. In 21 of 25 lines, T cell responses against one to five LMP2 epitopes were identified. These included responses to previously described epitopes as well as to newly identified HLA-A*0206-, A*0204/17-, A29-, A68-, B*1402-, B27-, B*3501-, B53-, and HLA-DR-restricted epitopes. Seven of the nine newly identified epitopes were antigenically conserved among virus isolates from nasopharyngeal carcinoma tumors. These new LMP2 epitopes broaden the diversity of HLA alleles with available epitopes, and, in particular, those epitopes conserved between EBV strains provide valuable tools for immunotherapy and immune monitoring.

Superior depletion of alloreactive T cells from peripheral blood stem cell and umbilical cord blood grafts by the combined use of trimetrexate and interleukin-2 immunotoxin

Acute graft-versus-host disease, a major obstacle to the overall success of allogeneic hematopoietic stem cell transplantation, is primarily induced by a subset of donor T cells. Most strategies to prevent acute graft-versus-host disease target all T cells regardless of their specificity, and this leads to prolonged posttransplantation immunodeficiency. Selective depletion of alloreactive T cells could spare protective immunity and facilitate engraftment and graft-versus-leukemia effects. Recently described depletion strategies target activation markers such as CD25 that are expressed by alloreactive T cells. However, incomplete depletion may occur when a single surface epitope or pathway of apoptosis is targeted that may not be fully and concurrently expressed among all alloreactive cells. We now report on a novel strategy effective in both cord blood and peripheral blood stem cell alloreactive T cells that simultaneously induces 2 independent pathways of apoptosis after stimulation by recipient dendritic cells or Epstein-Barr virus-transformed B cells. First, we demonstrate that the folate antagonist trimetrexate selectively depletes proliferating alloreactive precursors in vitro in a dose- and time-dependent manner. Similarly, a second agent, denileukin diftitox, kills activated alloreactive T cells expressing CD25. Most importantly, these 2 agents can exert their effects in concert with superior efficacy while sparing resting bystander T cells, which remain available to mount antimicrobial or third-party responses.

Cytotoxic T lymphocyte therapy for Epstein-Barr virus+ Hodgkin's disease

Epstein Barr virus (EBV)⁺ Hodgkin's disease (HD) expresses clearly identified tumor antigens derived from the virus and could, in principle, be a target for adoptive immunotherapy with viral antigen–specific T cells. However, like most tumor-associated antigens in immunocompetent hosts, these potential targets are only weakly immunogenic, consisting primarily of the latent membrane protein (LMP)1 and LMP2 antigens. Moreover, Hodgkin tumors possess a range of tumor evasion strategies. Therefore, the likely value of immunotherapy with EBV-specific cytotoxic effector cells has been questioned. We have now used a combination of gene marking, tetramer, and functional analyses to track the fate and assess the activity of EBV cytotoxic T lymphocyte (CTL) lines administered to 14 patients treated for relapsed EBV⁺ HD. Gene marking studies showed that infused effector cells could further expand by several logs in vivo, contribute to the memory pool (persisting up to 12 mo), and traffic to tumor sites. Tetramer and functional analyses showed that T cells reactive with the tumor-associated antigen LMP2 were present in the infused lines, expanded in peripheral blood after infusion, and also entered tumor. Viral load decreased, demonstrating the biologic activity of the infused CTLs. Clinically, EBV CTLs were well tolerated, could control type B symptoms (fever, night sweats, and weight loss), and had antitumor activity. After CTL infusion, five patients were in complete remission at up to 40 mo, two of whom had clearly measurable tumor at the time of treatment. One additional patient had a partial response, and five had stable disease. The performance and fate of these human tumor antigen–specific T cells in vivo suggests that they might be of value for the treatment of EBV⁺ Hodgkin lymphoma.