Virus-specific T-cell banks for 'off the shelf' adoptive therapy of refractory infections

HLA reduction of human T cells facilitates generation of immunologically multicompatible cellular products

ABSTRACT

Adoptive cellular therapies have shown enormous potential but are complicated by personalization. Because of HLA mismatch, rejection of transferred T cells frequently occurs, compromising the T-cell graft's functionality. This obstacle has led to the development of HLA knock-out (KO) T cells as universal donor cells. Whether such editing directly affects T-cell functionality remains poorly understood. In addition, HLA KO T cells are susceptible to missing self-recognition through natural killer (NK) cells and lack of canonical HLA class I expression may represent a safety hazard. Engineering of noncanonical HLA molecules could counteract NK-cell recognition, but further complicates the generation of cell products. Here, we show that HLA KO does not alter T-cell functionality in vitro and in vivo. Although HLA KO abrogates allogeneic T-cell responses, it elicits NK-cell recognition. To circumvent this problem, we demonstrate that selective editing of individual HLA class I molecules in primary human T cells is possible. Such HLA reduction not only inhibits T-cell alloreactivity and NK-cell recognition simultaneously, but also preserves the T-cell graft's canonical HLA class I expression. In the presence of allogeneic T cells and NK cells, T cells with remaining expression of a single, matched HLA class I allele show improved functionality in vivo in comparison with conventional allogeneic T cells. Since reduction to only a few, most frequent HLA haplotypes would already be compatible with large shares of patient populations, this approach significantly extends the toolbox to generate broadly applicable cellular products.

Rejection resistant CD30.CAR-modified Epstein-Barr virus-specific T cells as an off-the-shelf platform for CD30+ lymphoma

Off-the-shelf (OTS) adoptive T cell therapies have many benefits such as immediate availability, improved access and reduced cost, but face the major challenges of graft-vs-host disease (GVHD) and graft rejection, mediated by alloreactive T cells present in the graft and host, respectively. We have developed a platform for OTS T cell therapies by using Epstein-Bar virus (EBV)-specific T cells (EBVSTs) expressing a chimeric antigen receptor (CAR) targeting CD30. Allogeneic EBVSTs have not caused GVHD in several clinical trials, while the CD30.CAR, that is effective for the treatment of lymphoma, can also target alloreactive T cells that upregulate CD30 on activation. Although EBVSTs express high levels of CD30, they were protected from fratricide in cis, by the CD30.CAR. Hence, they could proliferate extensively and maintained function both through their native EBV-specific T cell receptor and the CD30.CAR. The CD30.CAR enabled EBVSTs to persist in co-cultures with naive and primed alloreactive T cells and eliminate activated natural killer cells that can also be alloreactive. In conclusion, we show that CD30.CAR EBVSTs have the potential to be an effective OTS therapy against CD30+ tumors and, if successful, could then be used as a platform to target other tumor antigens.

Qualitative evaluation of connective tissue disease with cytomegalovirus infection: A meta-analysis of case reports

BACKGROUND

The primary therapies for connective tissue disease include glucocorticoids and immunosuppressants. However, their prolonged usage can precipitate opportunistic infections, such as cytomegalovirus infection. When managing connective tissue disease complicated by cytomegalovirus infection, judicious selection of treatment modalities is crucial. This involves assessing the necessity for antiviral therapy and contemplating the reduction or cessation of glucocorticoids and immunosuppressants.

OBJECTIVE

This investigation sought to methodically review existing literature regarding treating connective tissue disease patients with cytomegalovirus infection.

METHODS

On July 5, 2023, an exhaustive literature search was conducted. Data analysis utilized the Kruskal-Wallis test or one-way analysis of variance, supplemented by Bonferroni post hoc testing.

RESULTS

Our meta-analysis incorporated 88 studies encompassing 146 connective tissue disease patients with CMV infections. The results indicated that patients with connective tissue disease and cytomegalovirus disease benefitted more from antiviral therapy than those not receiving such treatment (P = 0.003, P < 0.005). Furthermore, the strategic reduction of glucocorticoids and/or immunosuppressants was beneficial (P = 0.037, P < 0.05). Poor clinical outcomes with glucocorticoid-immunosuppressant combination therapy compared to other treatment modalities. The findings also suggested that CMV infection patients fare better without Cyclosporine A than using it (P = 0.041, P < 0.05).

CONCLUSION

Antiviral therapy is a viable treatment option in cases of connective tissue disease co-occurring with cytomegalovirus disease. Additionally, when connective tissue disease is stable, there is potential merit in reducing glucocorticoids and/or immunosuppressants, especially avoiding the combination of these drugs. For all cytomegalovirus infection patients, Cyclosporine A may be avoided wherever possible for selecting immunosuppressive agents if its use is not deemed essential in the treatment regimen.

Development and characterization of a cell donor registry for virus-specific T cell manufacture in a blood bank

Adoptive cell therapy using virus-specific T cells (VST) is a strategy for treating common opportunistic viral infections after transplantation, particularly when these infections do not resolve through antiviral drug therapy. The availability of third-party healthy donors allows for the immediate use of cells for allogeneic therapy in cases where patients lack an appropriate donor. Here, we present the creation of a cell donor registry of human leukocyte antigen (HLA)-typed blood donors, REDOCEL, a strategic initiative to ensure the availability of compatible cells for donation when needed. Currently, the registry consists of 597 healthy donors with a median age of 29 years, 54% of whom are women. The most represented blood groups were A positive and O positive, with 36.52% and 34.51%, respectively. Also, donors were screened for cytomegalovirus (CMV) and Epstein-Barr virus (EBV). Almost 65% of donors were CMV-seropositive, while less than 5% were EBV-seronegative. Of the CMV-seropositive donors, 98% were also EBV-seropositive. High-resolution HLA-A, -B, -C, -DRB1 and -DQB1 allele and haplotype frequencies were determined in the registry. Prevalent HLA alleles and haplotypes were well represented to ensure donor-recipient HLA-matching, including alleles reported to present viral immunodominant epitopes. Since the functional establishment of REDOCEL, in May 2019, 87 effective donations have been collected, and the effective availability of donors with the first call has been greater than 75%. Thus, almost 89% of patients receiving an effective donation had available at least 5/10 HLA-matched cell donors (HLA-A, -B, -C, -DRB1, and -DQB1). To summarize, based on our experience, a cell donor registry from previously HLA-typed blood donors is a useful tool for facilitating access to VST therapy.

Effective virus-specific T-cell therapy for high-risk SARS-CoV-2 infections in hematopoietic stem cell transplant recipients: initial case studies and literature review

The COVID-19 pandemic has exacerbated mortality rates among immunocompromised patients, accentuating the need for novel, targeted therapies. Transplant recipients, with their inherent immune vulnerabilities, represent a subgroup at significantly heightened risk. Current conventional therapies often demonstrate limited effectiveness in these patients, calling for innovative treatment approaches. In immunocompromised transplant recipients, several viral infections have been successfully treated by adoptive transfer of virus-specific T-cells (VST). This paper details the successful application of SARS-CoV-2-specific memory T-cell therapy, produced by an interferon-γ cytokine capture system (CliniMACS® Prodigy device), in three stem cell transplant recipients diagnosed with COVID-19 (case 1: alpha variant, cases 2 and 3: delta variants). These patients exhibited persistent SARS-CoV-2 PCR positivity accompanied by bilateral pulmonary infiltrates and demonstrated only partial response to standard treatments. Remarkably, all three patients recovered and achieved viral clearance within 3 to 9 weeks post-VST treatment. Laboratory follow-up investigations identified an increase in SARS-CoV-2-specific T-cells in two of the cases. A robust anti-SARS-CoV-2 S (S1/S2) IgG serological response was also recorded, albeit with varying titers. The induction of memory T-cells within the CD4 + compartment was confirmed, and previously elevated interleukin-6 (IL-6) and IL-8 levels normalized post-VST therapy. The treatment was well tolerated with no observed adverse effects. While the need for specialized equipment and costs associated with VST therapy present potential challenges, the limited treatment options currently available for COVID-19 within the allogeneic stem cell transplant population, combined with the risk posed by emerging SARS-CoV-2 mutations, underscore the potential of VST therapy in future clinical practice. This therapeutic approach may be particularly beneficial for elderly patients with multiple comorbidities and weakened immune systems.

Allogeneic CAR-T Therapy Technologies: Has the Promise Been Met?

This last decade, chimeric antigen receptor (CAR) T-cell therapy has become a real treatment option for patients with B-cell malignancies, while multiple efforts are being made to extend this therapy to other malignancies and broader patient populations. However, several limitations remain, including those associated with the time-consuming and highly personalized manufacturing of autologous CAR-Ts. Technologies to establish "off-the-shelf" allogeneic CAR-Ts with low alloreactivity are currently being developed, with a strong focus on gene-editing technologies. Although these technologies have many advantages, they have also strong limitations, including double-strand breaks in the DNA with multiple associated safety risks as well as the lack of modulation. As an alternative, non-gene-editing technologies provide an interesting approach to support the development of allogeneic CAR-Ts in the future, with possibilities of fine-tuning gene expression and easy development. Here, we will review the different ways allogeneic CAR-Ts can be manufactured and discuss which technologies are currently used. The biggest hurdles for successful therapy of allogeneic CAR-Ts will be summarized, and finally, an overview of the current clinical evidence for allogeneic CAR-Ts in comparison to its autologous counterpart will be given.

The paths and challenges of "off-the-shelf" CAR-T cell therapy: An overview of clinical trials

The advent of chimeric antigen receptor T cells (CAR-T cells) has made a tremendous revolution in the era of cancer immunotherapy, so that since 2017 eight CAR-T cell products have been granted marketing authorization. All of these approved products are generated from autologous sources, but this strategy faces several challenges such as time-consuming and expensive manufacturing process and reduced anti-tumor potency of patients' T cells due to the disease or previous therapies. The use of an allogeneic source can overcome these issues and provide an industrial, scalable, and standardized manufacturing process that reduces costs and provides faster treatment for patients. Nevertheless, for using allogeneic CAR-T cells, we are faced with the challenge of overcoming two formidable impediments: severe life-threatening graft-versus-host-disease (GvHD) caused by allogeneic CAR-T cells, and allorejection of allogeneic CAR-T cells by host immune cells which is called "host versus graft" (HvG). In this study, we reviewed recent registered clinical trials of allogeneic CAR-T cell therapy to analyze different approaches to achieve a safe and efficacious "off-the-shelf" source for chimeric antigen receptor (CAR) based immunotherapy.

iPSC-derived hypoimmunogenic tissue resident memory T cells mediate robust anti-tumor activity against cervical cancer

Functionally rejuvenated human papilloma virus-specific cytotoxic T lymphocytes (HPV-rejTs) generated from induced pluripotent stem cells robustly suppress cervical cancer. However, autologous rejT generation is time consuming, leading to difficulty in treating patients with advanced cancer. Although use of allogeneic HPV-rejTs can obviate this, the major obstacle is rejection by the patient immune system. To overcome this, we develop HLA-A24&-E dual integrated HPV-rejTs after erasing HLA class I antigens. These rejTs effectively suppress recipient immune rejection while maintaining more robust cytotoxicity than original cytotoxic T lymphocytes. Single-cell RNA sequencing performed to gain deeper insights reveal that HPV-rejTs are highly enriched with tissue resident memory T cells, which enhance cytotoxicity against cervical cancer through TGFβR signaling, with increased CD103 expression. Genes associated with the immunological synapse also are upregulated, suggesting that these features promote stronger activation of T cell receptor (TCR) and increased TCR-mediated target cell death. We believe that our work will contribute to feasible "off-the-shelf" T cell therapy with robust anti-cervical cancer effects.

Mechanisms of resistance to chimeric antigen receptor-T cells in haematological malignancies

Chimeric antigen receptor (CAR)-T cells have recently emerged as a powerful therapeutic approach for the treatment of patients with chemotherapy-refractory or relapsed blood cancers, including acute lymphoblastic leukaemia, diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma and multiple myeloma. Nevertheless, resistance to CAR-T cell therapies occurs in most patients. In this Review, we summarize the resistance mechanisms to CAR-T cell immunotherapy by analysing CAR-T cell dysfunction, intrinsic tumour resistance and the immunosuppressive tumour microenvironment. We discuss current research strategies to overcome multiple resistance mechanisms, including optimization of the CAR design, improvement of in vivo T cell function and persistence, modulation of the immunosuppressive tumour microenvironment and synergistic combination strategies.

Infections after chimeric antigen receptor (CAR)-T-cell therapy for hematologic malignancies

BACKGROUND

Chimeric antigen receptor (CAR)-T-cell therapies have revolutionized the management of acute lymphoblastic leukemia, non-Hodgkin lymphoma, and multiple myeloma but come at the price of unique toxicities, including cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and long-term "on-target off-tumor" effects.

METHODS

All of these factors increase infection risk in an already highly immunocompromised patient population. Indeed, infectious complications represent the key determinant of non-relapse mortality after CAR-T cells. The temporal distribution of these risk factors shapes different infection patterns early versus late post-CAR-T-cell infusion. Furthermore, due to the expression of their targets on B lineage cells at different stages of differentiation, CD19, and B-cell maturation antigen (BCMA) CAR-T cells induce distinct immune deficits that could require different prevention strategies. Infection incidence is the highest during the first month post-infusion and subsequently decreases thereafter. However, infections remain relatively common even a year after infusion.

RESULTS

Bacterial infections predominate early after CD19, while a more equal distribution between bacterial and viral causes is seen after BCMA CAR-T-cell therapy, and fungal infections are universally rare. Cytomegalovirus (CMV) and other herpesviruses are increasingly breported, but whether routine monitoring is warranted for all, or a subgroup of patients, remains to be determined. Clinical practices vary substantially between centers, and many areas of uncertainty remain, including CMV monitoring, antibacterial and antifungal prophylaxis and duration, use of immunoglobulin replacement therapy, and timing of vaccination.

CONCLUSION

Risk stratification tools are available and may help distinguish between infectious and non-infectious causes of fever post-infusion and predict severe infections. These tools need prospective validation, and their integration in clinical practice needs to be systematically studied.

Therapy With Allogeneic Severe Acute Respiratory Syndrome Coronavirus-2-Specific T Cells for Persistent Coronavirus Disease 2019 in Immunocompromised Patients

We administered severe acute respiratory syndrome coronavirus-2 viral-specific T cells (VSTs) under emergency investigational new drug applications to 6 immunocompromised patients with persistent coronavirus disease 2019 (COVID-19) and characterized clinical and virologic responses. Three patients had partial responses after failing other therapies but then died. Two patients completely recovered, but the role of VSTs in recovery was unclear due to concomitant use of other antivirals. One patient had not responded to 2 courses of remdesivir and experienced sustained recovery after VST administration. The use of VSTs in immunocompromised patients with persistent COVID-19 requires further study.

The two-step approach to allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) provides the only potentially curative option for multiple hematological conditions. However, allogeneic HSCT outcomes rely on an optimal balance of effective immune recovery, minimal graft-versus-host disease (GVHD), and lasting control of disease. The quest to attain this balance has proven challenging over the past few decades. The two-step approach to HSCT was conceptualized and pioneered at Thomas Jefferson University in 2005 and remains the main platform for allografting at our institution. Following administration of the transplant conditioning regimen, patients receive a fixed dose of donor CD3+ cells (HSCT step one-DLI) as the lymphoid portion of the graft on day -6 with the aim of optimizing and controlling T cell dosing. Cyclophosphamide (CY) is administered after the DLI (days -3 and -2) to induce donor-recipient bidirectional tolerance. On day 0, a CD34-selected stem cell graft is given as the myeloid portion of the graft (step two). In this two-step approach, the stem cell graft is infused after CY tolerization, which avoids exposure of the stem cells to an alkylating agent, allowing rapid count recovery. Here, the two-step platform is described with a focus on key results from studies over the past two decades. Finally, this review details lessons learned and current strategies to optimize the graft-versus-tumor effect and limit transplant-related toxicities.

SARS-CoV-2-specific T cell therapy for severe COVID-19: a randomized phase 1/2 trial

Despite advances, few therapeutics have shown efficacy in severe coronavirus disease 2019 (COVID-19). In a different context, virus-specific T cells have proven safe and effective. We conducted a randomized (2:1), open-label, phase 1/2 trial to evaluate the safety and efficacy of off-the-shelf, partially human leukocyte antigen (HLA)-matched, convalescent donor-derived severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells (CoV-2-STs) in combination with standard of care (SoC) in patients with severe COVID-19 compared to SoC during Delta variant predominance. After a dose-escalated phase 1 safety study, 90 participants were randomized to receive CoV-2-ST+SoC (n = 60) or SoC only (n = 30). The co-primary objectives of the study were the composite of time to recovery and 30-d recovery rate and the in vivo expansion of CoV-2-STs in patients receiving CoV-2-ST+SoC over SoC. The key secondary objective was survival on day 60. CoV-2-ST+SoC treatment was safe and well tolerated. The study met the primary composite endpoint (CoV-2-ST+SoC versus SoC: recovery rate 65% versus 38%, P = 0.017; median recovery time 11 d versus not reached, P = 0.052, respectively; rate ratio for recovery 1.71 (95% confidence interval 1.03-2.83, P = 0.036)) and the co-primary objective of significant CoV-2-ST expansion compared to SοC (CoV-2-ST+SoC versus SoC, P = 0.047). Overall, in hospitalized patients with severe COVID-19, adoptive immunotherapy with CoV-2-STs was feasible and safe. Larger trials are needed to strengthen the preliminary evidence of clinical benefit in severe COVID-19. EudraCT identifier: 2021-001022-22 .

Trans-population graph-based coverage optimization of allogeneic cellular therapy

Background

Pre-clinical development and in-human trials of 'off-the-shelf' immune effector cell therapy (IECT) are burgeoning. IECT offers many potential advantages over autologous products. The relevant HLA matching criteria vary from product to product and depend on the strategies employed to reduce the risk of GvHD or to improve allo-IEC persistence, as warranted by different clinical indications, disease kinetics, on-target/off-tumor effects, and therapeutic cell type (T cell subtype, NK, etc.).

Objective

The optimal choice of candidate donors to maximize target patient population coverage and minimize cost and redundant effort in creating off-the-shelf IECT product banks is still an open problem. We propose here a solution to this problem, and test whether it would be more expensive to recruit additional donors or to prevent class I or class II HLA expression through gene editing.

Study design

We developed an optimal coverage problem, combined with a graph-based algorithm to solve the donor selection problem under different, clinically plausible scenarios (having different HLA matching priorities). We then compared the efficiency of different optimization algorithms - a greedy solution, a linear programming (LP) solution, and integer linear programming (ILP) -- as well as random donor selection (average of 5 random trials) to show that an optimization can be performed at the entire population level.

Results

The average additional population coverage per donor decrease with the number of donors, and varies with the scenario. The Greedy, LP and ILP algorithms consistently achieve the optimal coverage with far fewer donors than the random choice. In all cases, the number of randomly-selected donors required to achieve a desired coverage increases with increasing population. However, when optimal donors are selected, the number of donors required may counter-intuitively decrease with increasing population size. When comparing recruiting more donors vs gene editing, the latter was generally more expensive. When choosing donors and patients from different populations, the number of random donors required drastically increases, while the number of optimal donors does not change. Random donors fail to cover populations different from their original populations, while a small number of optimal donors from one population can cover a different population.

Discussion

Graph-based coverage optimization algorithms can flexibly handle various HLA matching criteria and accommodate additional information such as KIR genotype, when such information becomes routinely available. These algorithms offer a more efficient way to develop off-the-shelf IECT product banks compared to random donor selection and offer some possibility of improved transparency and standardization in product design.

αβ and γδ T-cell responses to Epstein-Barr Virus: insights in immunocompetence, immune failure and therapeutic augmentation in transplant patients

Epstein-Barr Virus (EBV) is a human gamma herpes virus, which causes several diseases in immunocompetent (mononucleosis, chronic fatigue syndrome, gastric cancer, endemic Burkitt's lymphoma, head and neck cancer) and immunosuppressed (post-transplant lymphoproliferative disease, EBV-associated soft tissue tumors) patients. It elicits a complex humoral and cellular immune response with both innate and adaptive immune components. Substantial progress has been made in understanding the interplay of immune cells in EBV-associated diseases in recent years, and several therapeutic approaches have been developed to augment cellular immunity toward EBV for control of EBV-associated malignancy. This review will focus on recent developments in immunosuppressed transplant recipients.

Antigen-Specific T Cells and SARS-CoV-2 Infection: Current Approaches and Future Possibilities

COVID-19, a significant global health threat, appears to be an immune-related disease. Failure of effective immune responses in initial stages of infection may contribute to development of cytokine storm and systemic inflammation with organ damage, leading to poor clinical outcomes. Disease severity and the emergence of new SARS-CoV-2 variants highlight the need for new preventative and therapeutic strategies to protect the immunocompromised population. Available data indicate that these people may benefit from adoptive transfer of allogeneic SARS-CoV-2-specific T cells isolated from convalescent individuals. This review first provides an insight into the mechanism of cytokine storm development, as it is directly related to the exhaustion of T cell population, essential for viral clearance and long-term antiviral immunity. Next, we describe virus-specific T lymphocytes as a promising and efficient approach for the treatment and prevention of severe COVID-19. Furthermore, other potential cell-based therapies, including natural killer cells, regulatory T cells and mesenchymal stem cells are mentioned. Additionally, we discuss fast and effective ways of producing clinical-grade antigen-specific T cells which can be cryopreserved and serve as an effective "off-the-shelf" approach for rapid treatment of SARS-CoV-2 infection in case of sudden patient deterioration.

Features of cytomegalovirus infection and evaluation of cytomegalovirus-specific T cells therapy in children’s patients following allogeneic hematopoietic stem cell transplantation: A retrospective single-center study

Cytomegalovirus (CMV) infection remains a critical cause of mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT), despite improvement by pre-emptive antivirus treatment. CMV-specific cytotoxic T lymphocytes (CMV-CTL) are universally used and proven well-tolerance after allo-HSCT in adult clinical trials. However, it is not comprehensively evaluated in children’s patients. Herein, we conducted a retrospective study to determine the risk factors of CMV infection and evaluation of CMV-CTL in children patients who underwent allo-HSCT. As result, a significantly poor 5-year overall survival was found in the CMV infection group (87.3 vs. 94.6%, p=0.01). Haploidentical HSCT (haplo-HSCT) was identified as an independent risk factor for CMV infection through both univariate and multivariate analyses (p<0.001, p=0.027, respectively). Furthermore, the cumulative incidence of CMV infection was statistically higher in the haplo-HSCT group compared to the HLA-matched donor group (44.2% vs. 21.6%, p<0.001). Finally, the overall response rate of CMV-CTL was 89.7% (26/29 patients) in CMV infection after allo-HSCT. We concluded that CMV infection following allo-HSCT correlated with increased mortality in children’s patients, and haplo-HSCT was an independent risk factor for CMV infection. Adoptive CMV-CTL cell therapy was safe and effective in pediatric patients with CMV infection.

Resolving SARS-CoV-2 CD4+ T cell specificity via reverse epitope discovery

The current strategy to detect immunodominant T cell responses focuses on the antigen, employing large peptide pools to screen for functional cell activation. However, these approaches are labor and sample intensive and scale poorly with increasing size of the pathogen peptidome. T cell receptors (TCRs) recognizing the same epitope frequently have highly similar sequences, and thus, the presence of large sequence similarity clusters in the TCR repertoire likely identify the most public and immunodominant responses. Here, we perform a meta-analysis of large, publicly available single-cell and bulk TCR datasets from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals to identify public CD4+ responses. We report more than 1,200 αβTCRs forming six prominent similarity clusters and validate histocompatibility leukocyte antigen (HLA) restriction and epitope specificity predictions for five clusters using transgenic T cell lines. Collectively, these data provide information on immunodominant CD4+ T cell responses to SARS-CoV-2 and demonstrate the utility of the reverse epitope discovery approach.

Viral infection in hematopoietic stem cell transplantation: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee review on the role of cellular therapy in prevention and treatment

Despite recent advances in the field of HSCT, viral infections remain a frequent causeof morbidity and mortality among HSCT recipients. Adoptive transfer of viral specific T cells has been successfully used both as prophylaxis and treatment of viral infections in immunocompromised HSCT recipients. Increasingly, precise risk stratification of HSCT recipients with infectious complications should incorporate not only pretransplant clinical criteria, but milestones of immune reconstitution as well. These factors can better identify those at highest risk of morbidity and mortality and identify a population of HSCT recipients in whom adoptive therapy with viral specific T cells should be considered for either prophylaxis or second line treatment early after inadequate response to first line antiviral therapy. Broadening these approaches to improve outcomes for transplant recipients in countries with limited resources is a major challenge. While the principles of risk stratification can be applied, early detection of viral reactivation as well as treatment is challenging in regions where commercial PCR assays and antiviral agents are not readily available.

In Vitro Generation of BK polyomavirus-specific T cells for adoptive cell therapy in refractory cystitis hemorrhagic patients after hematopoietic stem cell transplantation

Introduction

BKPyV associated hemorrhagic cystitis (BKPyV-HC) is a major and prevalent outcome of hematopoietic stem cell transplantation (HSCT) with no standard treatment option. Adoptive T cell therapy (ACT) against transplant-associated viruses has shown promising potential. We sought to produce virus-specific T cells (VSTs) against BKPyV with the aim of treating refractory HSCT-associated HC.

Methods

Peripheral blood mononuclear cells (PBMC) from healthy donors were isolated by Ficoll-Hypaque density gradient centrifugation. BKPyV-pulsed, monocyte-derived dendritic cells (mo-DCs) and T cells were co-cultured and expanded over 2–3 weeks with the addition of IL-2. The T cells were examined for various functional assays.

Results

Comparison analysis of Carboxyfluorescein diacetate succinimidyl ester (CFSE) indicated that the percentage of proliferated cells were significantly higher in donors (49.62 ± 7.09%) than controls (7.96 ± 4.55%). Furthermore, expanded T cells exhibited specificity to BKPyV antigens by IFN-γ ELISPOT assay. The expanded cells showed cytotoxic function versus human lymphoblastoid cell line (LCL). Final VST products mainly comprised of CD8/CD69 double-positive T cells, which were significantly higher in donors (46.8 ± 7.1%) than controls (16.91 ± 3.40%).

Conclusion

In this study we demonstrated the feasibility of producing functional BKPyV-specific T cells in healthy donors using BKPyV PepMixes. These functional cells were able to proliferate and produce IFN-γ cytokine in response to BKPyV PepMixes. In addition, these T cells had cytotoxic ability against BKPyV antigen-expressing target cells.

Tacrolimus-resistant SARS-CoV-2-specific T cell products to prevent and treat severe COVID-19 in immunosuppressed patients

Solid organ transplant (SOT) recipients receive therapeutic immunosuppression that compromises their immune response to infections and vaccines. For this reason, SOT patients have a high risk of developing severe coronavirus disease 2019 (COVID-19) and an increased risk of death from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Moreover, the efficiency of immunotherapies and vaccines is reduced due to the constant immunosuppression in this patient group. Here, we propose adoptive transfer of SARS-CoV-2-specific T cells made resistant to a common immunosuppressant, tacrolimus, for optimized performance in the immunosuppressed patient. Using a ribonucleoprotein approach of CRISPR-Cas9 technology, we have generated tacrolimus-resistant SARS-CoV-2-specific T cell products from convalescent donors and demonstrate their specificity and function through characterizations at the single-cell level, including flow cytometry, single-cell RNA (scRNA) Cellular Indexing of Transcriptomes and Epitopes (CITE), and T cell receptor (TCR) sequencing analyses. Based on the promising results, we aim for clinical validation of this approach in transplant recipients. Additionally, we propose a combinatory approach with tacrolimus, to prevent an overshooting immune response manifested as bystander T cell activation in the setting of severe COVID-19 immunopathology, and tacrolimus-resistant SARS-CoV-2-specific T cell products, allowing for efficient clearance of viral infection. Our strategy has the potential to prevent severe COVID-19 courses in SOT or autoimmunity settings and to prevent immunopathology while providing viral clearance in severe non-transplant COVID-19 cases.

Adoptive therapy with cytomegalovirus-specific T cells for cytomegalovirus infection after haploidentical stem cell transplantation and factors affecting efficacy

Adoptive therapy with cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CMV-CTLs) has emerged as an effective method for CMV infection. However, the efficacy reportedly ranges from 50% to 90%, and factors affecting anti-CMV efficacy have not been established. We investigated the safety and efficacy of adoptive therapy with CMV-CTLs for CMV infection in 190 patients after haploidentical stem cell transplantation (haplo-SCT), and importantly, we analyzed the main factors affecting antiviral efficacy. The CMV peak titer decreased from 19 (range, 1.0-503.0) × 10³  copies/mL to 3.9 (range, 0-112) × 10³  copies/mL after CMV-CTL infusion. The cumulative complete response (CR) rates in the first, fourth, and sixth weeks after the first CMV-CTL infusion were 37.9% (95% CI 35.0-40.8), 76.8% (95% CI 70.7-82.9), and 89.5% (95% CI 85.2-93.8), respectively. In multivariate analysis, persistent CMV infection prior to CMV-CTL infusion (hazard ratio [HR] 2.29, 95% CI 1.29-4.06, p = .005) and basiliximab treatment within 2 weeks of CMV-CTL infusion (HR 1.87, 95% CI 1.06-3.81, p = .031) were independent predictors of poor antiviral efficacy of CMV-CTL therapy. Our data showed that adoptive therapy with CMV-CTLs is a safe and effective treatment for CMV infection after haplo-SCT. Persistent CMV infection and basiliximab treatment are correlated with poor anti-CMV efficacy of CMV-CTL therapy.

Engineering-Induced Pluripotent Stem Cells for Cancer Immunotherapy

Simple Summary

Induced pluripotent stem cells (iPSCs) that can be genetically engineered and differentiated into different types of immune cells, providing an unlimited resource for developing off-the-shelf cell therapies. Here, we present a comprehensive review that describes the current stages of iPSC-based cell therapies, including iPSC-derived T, nature killer (NK), invariant natural killer T (iNKT), gamma delta T (γδ T), mucosal-associated invariant T (MAIT) cells, and macrophages (Mφs).

Abstract

Cell-based immunotherapy, such as chimeric antigen receptor (CAR) T cell therapy, has revolutionized the treatment of hematological malignancies, especially in patients who are refractory to other therapies. However, there are critical obstacles that hinder the widespread clinical applications of current autologous therapies, such as high cost, challenging large-scale manufacturing, and inaccessibility to the therapy for lymphopenia patients. Therefore, it is in great demand to generate the universal off-the-shelf cell products with significant scalability. Human induced pluripotent stem cells (iPSCs) provide an “unlimited supply” for cell therapy because of their unique self-renewal properties and the capacity to be genetically engineered. iPSCs can be differentiated into different immune cells, such as T cells, natural killer (NK) cells, invariant natural killer T (iNKT) cells, gamma delta T (γδ T), mucosal-associated invariant T (MAIT) cells, and macrophages (Mφs). In this review, we describe iPSC-based allogeneic cell therapy, the different culture methods of generating iPSC-derived immune cells (e.g., iPSC-T, iPSC-NK, iPSC-iNKT, iPSC-γδT, iPSC-MAIT and iPSC-Mφ), as well as the recent advances in iPSC-T and iPSC-NK cell therapies, particularly in combinations with CAR-engineering. We also discuss the current challenges and the future perspectives in this field towards the foreseeable applications of iPSC-based immune therapy.

Comparable anti-CMV responses of transplant donor and third-party CMV-specific T cells for treatment of CMV infection after allogeneic stem cell transplantation

Adoptive transfer of cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CMV-CTLs) from original transplant donors or third-party donors was effective for the treatment of CMV infection after allogenic stem cell transplantation (allo-SCT), but the antiviral activity of CMV-CTL types has not been compared. To determine whether third-party CMV-CTLs provide comparable long-term antiviral efficacy to transplant donor CMV-CTLs, we first compared the antiviral abilities of transplant donors and third-party CMV-CTLs for treatment of CMV infection in two mouse models, compared the in vivo recovery of CMV-specific immunity, and analyzed the underlying mechanisms driving sustained antiviral immunity. The results showed that both donor and third-party CMV-CTLs effectively combated systemic CMV infection by reducing CMV pathology and tumor burden 28 days postinfusion. The in vivo recovery of CMV-specific immunity after CMV-CTL infusion was comparable in both groups. A detailed analysis of the source of recovered CMV-CTLs showed the proliferation and expansion of graft-derived endogenous CMV-CTLs in both groups. Our clinical study, which enrolled 31 patients who received third-party CMV-CTLs and 62 matched pairs of individuals who received transplant donor CMV-CTLs for refractory CMV infection, further showed that adoptive therapy with donor or third-party CMV-CTLs had comparable clinical responses without significant therapy-related toxicity. We observed strong expansion of CD8⁺ tetramer⁺ T cells and proliferation of recipient endogenous CMV-CTLs after CMV-CTL infusion, which were associated with a reduced or cleared viral load. Our data confirmed that adoptive therapy with third-party or transplant donor CMV-CTLs triggered comparable antiviral responses to CMV infection that might be mediated by restoration of endogenous CMV-specific immunity.

Cellular therapies for the treatment and prevention of SARS-CoV-2 infection

Patients with blood disorders who are immune suppressed are at increased risk for infection with severe acute respiratory syndrome coronavirus 2. Sequelae of infection can include severe respiratory disease and/or prolonged duration of viral shedding. Cellular therapies may protect these vulnerable patients by providing antiviral cellular immunity and/or immune modulation. In this recent review of the field, phase 1/2 trials evaluating adoptive cellular therapies with virus-specific T cells or natural killer cells are described along with trials evaluating the safety, feasibility, and preliminary efficacy of immune modulating cellular therapies including regulatory T cells and mesenchymal stromal cells. In addition, the immunologic basis for these therapies is discussed.

Allogeneic Chimeric Antigen Receptor Therapy in Lymphoma

The therapeutic armamentarium has significantly expanded since the approval of various CD19-targeting chimeric antigen receptor T cell (CAR-T) therapies in non-Hodgkin lymphoma (NHL). These CAR-Ts are patient-specific and require a complex, resource, and time-consuming process. While this appears promising, autologous CAR-Ts are limited due to the lack of accessibility, manufacturing delays, and variable product quality. To overcome these, allogeneic (allo) CARs from healthy donors appear appealing. These can be immediately available as “off the shelf” ready-to-use products of standardized and superior quality exempt from the effects of an immunosuppressive tumor microenvironment and prior treatments, and potentially with lower healthcare utilization using industrialized scale production. Allogeneic CARs, however, are not devoid of complications and require genomic editing, especially with αβ T cells to avoid graft versus host disease (GvHD) and allo-rejection by the recipient’s immune system. Tools for genomic editing such as TALEN and CRISPR provide promise to develop truly “off the shelf” universal CARs and further advance the field of cellular immunotherapy. Several allogeneic CARs are currently in early phase clinical trials, and preliminary data is encouraging. Longer follow-up is required to truly assess the feasibility and safety of these techniques in the patients. This review focuses on the strategies for developing allogeneic CARs along with cell sources and clinical experience thus far in lymphoma.

SARS-CoV-2-specific T cells generated for adoptive immunotherapy are capable of recognizing multiple SARS-CoV-2 variants

Adoptive T-cell immunotherapy has provided promising results in the treatment of viral complications in humans, particularly in the context of immunocompromised patients who have exhausted all other clinical options. The capacity to expand T cells from healthy immune individuals is providing a new approach to anti-viral immunotherapy, offering rapid off-the-shelf treatment with tailor-made human leukocyte antigen (HLA)-matched T cells. While most of this research has focused on the treatment of latent viral infections, emerging evidence that SARS-CoV-2-specific T cells play an important role in protection against COVID-19 suggests that the transfer of HLA-matched allogeneic off-the-shelf virus-specific T cells could provide a treatment option for patients with active COVID-19 or at risk of developing COVID-19. We initially screened 60 convalescent individuals and based on HLA typing and T-cell response profile, 12 individuals were selected for the development of a SARS-CoV-2-specific T-cell bank. We demonstrate that these T cells are specific for up to four SARS-CoV-2 antigens presented by a broad range of both HLA class I and class II alleles. These T cells show consistent functional and phenotypic properties, display cytotoxic potential against HLA-matched targets and can recognize HLA-matched cells infected with different SARS-CoV-2 variants. These observations demonstrate a robust approach for the production of SARS-CoV-2-specific T cells and provide the impetus for the development of a T-cell repository for clinical assessment.

Since the emergence of SARS-CoV-2 variants that reduce the effectiveness of vaccines, it is evident that other interventional strategies will be needed to treat COVID-19, particularly in patients with a compromised immune system who are at an increased risk of developing severe COVID-19. Off-the-shelf T-cell immunotherapy is proving to be a powerful tool to treat viral disease in patients with a compromised immune system. Here, we report here that a small number of SARS-CoV-2 exposed individuals can be used generate a bank of specific T cells that provide broad population coverage. Importantly, we demonstrate that most of the epitopes recognized by these T cells remain unchanged in different variants and that the T cells can recognize cells infected with three different variants of SARS-CoV-2. We believe these observations provide critical proof-of-concept that T-cell based immunotherapy may offer an option for the future treatment of immunocompromised patients who remain susceptible to the severe complications associated with COVID-19.

Cytomegalovirus and other herpesviruses after hematopoietic cell and solid organ transplantation: From antiviral drugs to virus-specific T cells

Herpesviruses can either cause primary infection or may get reactivated after both hematopoietic cell and solid organ transplantations. In general, viral infections increase post-transplant morbidity and mortality. Prophylactic, preemptive, or therapeutically administered antiviral drugs may be associated with serious side effects and may induce viral resistance. Virus-specific T cells represent a valuable addition to antiviral treatment, with high rates of response and minimal side effects. Even low numbers of virus-specific T cells manufactured by direct selection methods can reconstitute virus-specific immunity after transplantation and control viral replication. Virus-specific T cells belong to the advanced therapy medicinal products, and their production is regulated by appropriate legislation; also, strict safety regulations are required to minimize their side effects.

Off-the-Shelf Partial HLA Matching SARS-CoV-2 Antigen Specific T Cell Therapy: A New Possibility for COVID-19 Treatment

Background

Immunological characteristics of COVID-19 show pathological hyperinflammation associated with lymphopenia and dysfunctional T cell responses. These features provide a rationale for restoring functional T cell immunity in COVID-19 patients by adoptive transfer of SARS-CoV-2 specific T cells.

Methods

To generate SARS-CoV-2 specific T cells, we isolated peripheral blood mononuclear cells from 7 COVID-19 recovered and 13 unexposed donors. Consequently, we stimulated cells with SARS-CoV-2 peptide mixtures covering spike, membrane and nucleocapsid proteins. Then, we culture expanded cells with IL-2 for 21 days. We assessed immunophenotypes, cytokine profiles, antigen specificity of the final cell products.

Results

Our results show that SARS-CoV-2 specific T cells could be expanded in both COVID-19 recovered and unexposed groups. Immunophenotypes were similar in both groups showing CD4+ T cell dominance, but CD8+ and CD3+CD56+ T cells were also present. Antigen specificity was determined by ELISPOT, intracellular cytokine assay, and cytotoxicity assays. One out of 14 individuals who were previously unexposed to SARS-CoV-2 failed to show antigen specificity. Moreover, ex-vivo expanded SARS-CoV-2 specific T cells mainly consisted of central and effector memory subsets with reduced alloreactivity against HLA-unmatched cells suggesting the possibility for the development of third-party partial HLA-matching products.

Discussion

In conclusion, our findings show that SARS-CoV-2 specific T cell can be readily expanded from both COVID-19 and unexposed individuals and can therefore be manufactured as a biopharmaceutical product to treat severe COVID-19 patients.

One Sentence Summary

Ex-vivo expanded SARS-CoV-2 antigen specific T cells developed as third-party partial HLA-matching products may be a promising approach for treating severe COVID-19 patients that do not respond to previous treatment options.

Protective T cell receptor identification for orthotopic reprogramming of immunity in refractory virus infections

Viral infections cause life-threatening disease in immunocompromised patients and especially following transplantation. T cell receptor (TCR) engineering redirects specificity and can bring significant progress to emerging adoptive T cell transfer (ACT) approaches. T cell epitopes are well described, although knowledge is limited on which TCRs mediate protective immunity. In this study, refractory adenovirus (AdV) infection after hematopoietic stem cell transplantation (HSCT) was treated with ACT of highly purified Hexon5-specific T cells using peptide major histocompatibility complex (pMHC)-Streptamers against the immunodominant human leukocyte antigen (HLA)-A∗0101-restricted peptide LTDLGQNLLY. AdV was successfully controlled through this oligoclonal ACT. Novel protective TCRs were isolated ex vivo and preclinically engineered into the TCR locus of allogeneic third-party primary T cells by CRISPR-Cas9-mediated orthotopic TCR replacement. Both TCR knockout and targeted integration of the new TCR in one single engineering step led to physiological expression of the transgenic TCR. Reprogrammed TCR-edited T cells showed strong virus-specific functionality such as cytokine release, effector marker upregulation, and proliferation capacity, as well as cytotoxicity against LTDLGQNLLY-presenting and AdV-infected targets. In conclusion, ex vivo isolated TCRs with clinical proven protection through ACT could be redirected into T cells from naive third-party donors. This approach ensures that transgenic TCRs are protective with potential off-the-shelf use and widened applicability of ACT to various refractory emerging viral infections.

[Development of allogeneic CAR T-cells]

Chimeric antigen receptor (CAR) T-cell therapy represents a major breakthrough in the field of hematology. "Off-the-shelf" allogeneic CAR T-cells from donors have many potential advantages over autologous approaches, such as the immediate availability of cryopreserved batches, possible standardization of the cell product, time for multiple cell modifications, redosing and decreased cost. However, allogeneic T-cells possess foreign immunological identities that can lead to graft-versus-host disease (GvHD) and their rejection by the host immune system. In this review, we describe the different approaches to produce allogeneic CAR T-cells with limited potential for GvHD and that can persist in the recipient. The preliminary clinical results obtained with the first generation of allogeneic CAR T-cells are presented as well as the perspectives in hematological malignancies and solid tumors.

Immunoinformatic Analysis Reveals Antigenic Heterogeneity of Epstein-Barr Virus Is Immune-Driven

Whole genome sequencing of Epstein-Barr virus (EBV) isolates from around the world has uncovered pervasive strain heterogeneity, but the forces driving strain diversification and the impact on immune recognition remained largely unknown. Using a data mining approach, we analyzed more than 300 T-cell epitopes in 168 published EBV strains. Polymorphisms were detected in approximately 65% of all CD8+ and 80% of all CD4+ T-cell epitopes and these numbers further increased when epitope flanking regions were included. Polymorphisms in CD8+ T-cell epitopes often involved MHC anchor residues and resulted in changes of the amino acid subgroup, suggesting that only a limited number of conserved T-cell epitopes may represent generic target antigens against different viral strains. Although considered the prototypic EBV strain, the rather low degree of overlap with most other viral strains implied that B95.8 may not represent the ideal reference strain for T-cell epitopes. Instead, a combinatorial library of consensus epitopes may provide better targets for diagnostic and therapeutic purposes when the infecting strain is unknown. Polymorphisms were significantly enriched in epitope versus non-epitope protein sequences, implicating immune selection in driving strain diversification. Remarkably, CD4+ T-cell epitopes in EBNA2, EBNA-LP, and the EBNA3 family appeared to be under negative selection pressure, hinting towards a beneficial role of immune responses against these latency type III antigens in virus biology. These findings validate this immunoinformatics approach for providing novel insight into immune targets and the intricate relationship of host defense and virus evolution that may also pertain to other pathogens.

American Society for Transplantation and Cellular Therapy Series: #4 - Cytomegalovirus treatment and management of resistant or refractory infections after hematopoietic cell transplantation

The Practice Guidelines Committee of the American Society of Transplantation and Cellular Therapy (ASTCT) partnered with its Transpl. Infect. Dis. Special Interest Group (TID-SIG) to update its 2009 compendium-style infectious disease guidelines for hematopoietic cell transplantation (HCT). A new approach was employed with the goal of better serving clinical providers by publishing each standalone topic in the infectious diseases series as a concise format of frequently asked questions (FAQ), tables, and figures. Adult and pediatric infectious diseases and HCT content experts developed and answered FAQs. Topics were finalized with harmonized recommendations that were made by assigning an A through E strength of recommendation paired with a level of supporting evidence graded I through III. The fourth topic in the series focuses on the management and treatment of cytomegalovirus (CMV) resistant and refractory infections. The diagnosis, definitions of resistant and refractory CMV, risk factors, virological genotypes and treatment algorithms are reviewed.

Epstein-Barr virus posttransplant lymphoproliferative disorder: update on management and outcomes

PURPOSE OF REVIEW

Management of Epstein-Barr virus posttransplant lymphoproliferative disorder (EBV PTLD) is complex, involving risk stratification, prevention and/or preemptive measures involving monitoring EBV DNAemia and balancing treatment options, using a combination of reduction of immune suppression, anti-B cell therapy, and cytotoxic T lymphocytes (CTLs).

RECENT FINDINGS

The highest risk factor for the development of EBV PTLD in hematopoietic cell transplant (HCT) remains T cell depletion, with increasing use of antithymocyte globulin (ATG) or alemtuzumab in conditioning. In solid organ transplantation (SOT), the incidence of PTLD is highest among EBV seronegative recipients who are at risk for primary EBV infection following transplant in the first 12 months. Prevention is a critical component of the management of EBV PTLD. Although preemptive therapy remains standard of care, there continues to be heterogenicity and debate over the optimal choice of EBV DNA quantification and the threshold to use. Novel therapies such as donor-derived multipathogen and EBV specific CTLs for the prevention and third party CTLs for the treatment of EBV PTLD are promising, with rapidly expanding evidence, including large scale Phase III trials currently underway.

SUMMARY

With an increasing number of risk groups for developing EBV PTLD in HCT and SOT, management strategies using prophylaxis or preemptive therapy remain standard of care, however the use of prophylactic or preemptive EBV specific or multipathogen CTLs show promising results and safety profiles.

Characterization of SARS-CoV-2 public CD4+ αβ T cell clonotypes through reverse epitope discovery

The amount of scientific data and level of public sharing produced as a consequence of the COVID-19 pandemic, as well as the speed at which these data were produced, far exceeds any previous effort against a specific disease condition. This unprecedented situation allows for development and application of new research approaches. One of the major technical hurdles in immunology is the characterization of HLA-antigen-T cell receptor (TCR) specificities. Most approaches aim to identify reactive T cells starting from known antigens using functional assays. However, the need for a reverse approach identifying the antigen specificity of orphan TCRs is increasing. Utilizing large public single-cell gene expression and TCR datasets, we identified highly public CD4 ⁺ T cell responses to SARS-CoV-2, covering >75% of the analysed population. We performed an integrative meta-analysis to deeply characterize these clonotypes by TCR sequence, gene expression, HLA-restriction, and antigen-specificity, identifying strong and public CD4 ⁺ immunodominant responses with confirmed specificity. CD4 ⁺ COVID-enriched clonotypes show T follicular helper functional features, while clonotypes depleted in SARS-CoV-2 individuals preferentially had a central memory phenotype. In total we identify more than 1200 highly public CD4+ T cell clonotypes reactive to SARS-CoV-2. TCR similarity analysis showed six prominent TCR clusters, for which we predicted both HLA-restriction and cognate SARS-CoV-2 immunodominant epitopes. To validate our predictions we used an independent cohort of TCR repertoires before and after vaccination with ChAdOx1 , a replication-deficient simian adenovirus-vectored vaccine, encoding the SARS-CoV-2 spike protein. We find statistically significant enrichment of the predicted spike-reactive TCRs after vaccination with ChAdOx1 , while the frequency of TCRs specific to other SARS-CoV-2 proteins remains stable. Thus, the CD4-associated TCR repertoire differentiates vaccination from natural infection. In conclusion, our study presents a novel reverse epitope discovery approach that can be used to infer HLA- and antigen-specificity of orphan TCRs in any context, such as viral infections, antitumor immune responses, or autoimmune disease.

HIGHLIGHTS

Identification of highly public CD4+ T cell responses to SARS-CoV-2Systematic prediction of exact immunogenic HLA class II epitopes for CD4+ T cell responseMethodological framework for reverse epitope discovery, which can be applied to other disease contexts and may provide essential insights for future studies and clinical applications.

Cytomegalovirus in Haematological Tumours

The exquisite coupling between herpesvirus and human beings is the result of millions of years of relationship, coexistence, adaptation, and divergence. It is probably based on the ability to generate a latency that keeps viral activity at a very low level, thereby apparently minimising harm to its host. However, this evolutionary success disappears in immunosuppressed patients, especially in haematological patients. The relevance of infection and reactivation in haematological patients has been a matter of interest, although one fundamentally focused on reactivation in the post-allogeneic stem cell transplant (SCT) patient cohort. Newer transplant modalities have been progressively introduced in clinical settings, with successively more drugs being used to manipulate graft composition and functionality. In addition, new antiviral drugs are available to treat CMV infection. We review the immunological architecture that is key to a favourable outcome in this subset of patients. Less is known about the effects of herpesvirus in terms of mortality or disease progression in patients with other malignant haematological diseases who are treated with immuno-chemotherapy or new molecules, or in patients who receive autologous SCT. The absence of serious consequences in these groups has probably limited the motivation to deepen our knowledge of this aspect. However, the introduction of new therapeutic agents for haematological malignancies has led to a better understanding of how natural killer (NK) cells, CD4+ and CD8+ T lymphocytes, and B lymphocytes interact, and of the role of CMV infection in the context of recently introduced drugs such as Bruton tyrosine kinase (BTK) inhibitors, phosphoinosytol-3-kinase inhibitors, anti-BCL2 drugs, and even CAR-T cells. We analyse the immunological basis and recommendations regarding these scenarios.

From Hematopoietic Stem Cell Transplantation to Chimeric Antigen Receptor Therapy: Advances, Limitations and Future Perspectives

Chimeric antigen receptor (CAR) T-cell therapy was envisioned as a mechanism to re-direct effector T-cells to eliminate tumor cells. CARs are composed of the variable region of an antibody that binds a native cancer antigen coupled to the signaling domain of a TCR and co-stimulatory molecules. Its success and approval by the U.S. Food and Drug Administration for the treatment of B-cell malignancies revolutionized the immunotherapy field, leading to extensive research on its possible application for other cancer types. In this review, we will focus on the evolution of CAR-T cell therapy outlining current technologies as well as major obstacles for its wide application. We will highlight achievements, the efforts to increase efficacy and to evolve into an off-the-shelf treatment, and as a possible future treatment for non-cancer related diseases.

Driving Out Chronic Lymphocytic Leukemia With CAR T Cells

Chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in the Western hemisphere. The recent availability of novel targeted therapies, namely Bruton's tyrosine kinase, phosphoinositide-3 kinase, and BCL-2 inhibitors, have revolutionized the treatment algorithm for CLL but have not yet resulted in cure. Advances in the field of immuno-oncology and T cell engineering brought chimeric antigen receptor (CAR) T cell therapy from the laboratory to the clinic for treatment of B cell lymphoid malignancies and has improved the disease response and survival outcomes of various types of relapsed and/or refractory B cell lymphomas. While acknowledging that there are no approved CAR T cell therapies for CLL at this time, in this comprehensive review we explore novel targets for CAR T cell therapy in CLL and highlight the promising results of CAR T cell trials reported to date. Furthermore, we shed light on future areas of development, including multitarget CAR T cell products for this disease.

An outlook on antigen-specific adoptive immunotherapy for viral infections with a focus on COVID-19

Although not a standard-of-care yet, adoptive immunotherapeutic approaches have gradually earned a place within the list of antiviral therapies for some of fatal and hard-to-treat viral diseases. To maintain robust antiviral immunity and to effectively target the viral particles and virally-infected cells, immune cells capable of recognizing the viral antigens are required. While conventional vaccination can induce these cells in vivo; another option is to prime and generate antigen-specific immune cells ex vivo. This approach has been successfully trialed for virulent opportunistic viral infections after bone marrow transplantation. Amid the crisis of SARS-CoV2 pandemic, which has been followed by the success of certain early-authorized vaccines; some institutions and companies have explored the effects of viral-specific adoptive cell transfers (ACTs) in trials, as alternative treatments. Aimed at outlining a perspective on antigen-specific adoptive immunotherapy for viral infections, this review article specifically provides an appraisal of ACT-based studies/trials on SARS-CoV2 infection.

Identification of novel HLA-restricted preferentially expressed antigen in melanoma peptides to facilitate off-the-shelf tumor-associated antigen-specific T-cell therapies

BACKGROUND AIMS

Preferentially expressed antigen in melanoma (PRAME) is a cancer/testis antigen that is overexpressed in many human malignancies and poorly expressed or absent in healthy tissues, making it a good target for anti-cancer immunotherapy. Development of an effective off-the-shelf adoptive T-cell therapy for patients with relapsed or refractory solid tumors and hematological malignancies expressing PRAME antigen requires the identification of major histocompatibility complex (MHC) class I and II PRAME antigens recognized by the tumor-associated antigen (TAA) T-cell product. The authors therefore set out to extend the repertoire of HLA-restricted PRAME peptide epitopes beyond the few already characterized.

METHODS

Peptide libraries of 125 overlapping 15-mer peptides spanning the entire PRAME protein sequence were used to identify HLA class I- and II-restricted epitopes. The authors also determined the HLA restriction of the identified epitopes.

RESULTS

PRAME-specific T-cell products were successfully generated from peripheral blood mononuclear cells of 12 healthy donors. Ex vivo-expanded T cells were polyclonal, consisting of both CD4+ and CD8+ T cells, which elicited anti-tumor activity in vitro. Nine MHC class I-restricted PRAME epitopes were identified (seven novel and two previously described). The authors also characterized 16 individual 15-mer peptide sequences confirmed as CD4-restricted epitopes.

CONCLUSIONS

TAA T cells derived from healthy donors recognize a broad range of CD4+ and CD8+ HLA-restricted PRAME epitopes, which could be used to select suitable donors for generating off-the-shelf TAA-specific T cells.

Distinct immunopathological mechanisms of EBV-positive and EBV-negative posttransplant lymphoproliferative disorders

EBV-positive and EBV-negative posttransplant lymphoproliferative disorders (PTLDs) arise in different immunovirological contexts and might have distinct pathophysiologies. To examine this hypothesis, we conducted a multicentric prospective study with 56 EBV-positive and 39 EBV-negative PTLD patients of the K-VIROGREF cohort, recruited at PTLD diagnosis and before treatment (2013-2019), and compared them to PTLD-free Transplant Controls (TC, n = 21). We measured absolute lymphocyte counts (n = 108), analyzed NK- and T cell phenotypes (n = 49 and 94), and performed EBV-specific functional assays (n = 16 and 42) by multiparameter flow cytometry and ELISpot-IFNγ assays (n = 50). EBV-negative PTLD patients, NK cells overexpressed Tim-3; the 2-year progression-free survival (PFS) was poorer in patients with a CD4 lymphopenia (CD4⁺ <300 cells/mm³ , p <  .001). EBV-positive PTLD patients presented a profound NK-cell lymphopenia (median = 60 cells/mm³ ) and a high proportion of NK cells expressing PD-1 (vs. TC, p = .029) and apoptosis markers (vs. TC, p < .001). EBV-specific T cells of EBV-positive PTLD patients circulated in low proportions, showed immune exhaustion (p = .013 vs. TC) and poorly recognized the N-terminal portion of EBNA-3A viral protein. Altogether, this broad comparison of EBV-positive and EBV-negative PTLDs highlight distinct patterns of immunopathological mechanisms between these two diseases and provide new clues for immunotherapeutic strategies and PTLD prognosis.

Generation of glucocorticoid-resistant SARS-CoV-2 T cells for adoptive cell therapy

Adoptive cell therapy with virus-specific T cells has been used successfully to treat life-threatening viral infections, supporting application of this approach to coronavirus disease 2019 (COVID-19). We expand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) T cells from the peripheral blood of COVID-19-recovered donors and non-exposed controls using different culture conditions. We observe that the choice of cytokines modulates the expansion, phenotype, and hierarchy of antigenic recognition by SARS-CoV-2 T cells. Culture with interleukin (IL)-2/4/7, but not under other cytokine-driven conditions, results in more than 1,000-fold expansion in SARS-CoV-2 T cells with a retained phenotype, function, and hierarchy of antigenic recognition compared with baseline (pre-expansion) samples. Expanded cytotoxic T lymphocytes (CTLs) are directed against structural SARS-CoV-2 proteins, including the receptor-binding domain of Spike. SARS-CoV-2 T cells cannot be expanded efficiently from the peripheral blood of non-exposed controls. Because corticosteroids are used for management of severe COVID-19, we propose an efficient strategy to inactivate the glucocorticoid receptor gene (NR3C1) in SARS-CoV-2 CTLs using CRISPR-Cas9 gene editing.

Microfluidics sorting enables the isolation of an intact cellular pair complex of CD8+ T cells and antigen-presenting cells in a cognate antigen recognition-dependent manner

Adaptive immune responses begin with cognate antigen presentation-dependent specific interaction between T cells and antigen-presenting cells. However, there have been limited reports on the isolation and analysis of these cellular complexes of T cell-antigen-presenting cell (T/APC). In this study, we successfully isolated intact antigen-specific cellular complexes of CD8+ T/APC by utilizing a microfluidics cell sorter. Using ovalbumin (OVA) model antigen and OT-I-derived OVA-specific CD8+ T cells, we analyzed the formation of antigen-specific and antigen-non-specific T/APC cellular complexes and revealed that the antigen-specific T/APC cellular complex was highly stable than the non-specific one, and that the intact antigen-specific T/APC complex can be retrieved as well as enriched using a microfluidics sorter, but not a conventional cell sorter. The single T/APC cellular complex obtained can be further analyzed for the sequences of T cell receptor Vα and Vβ genes as well as cognate antigen information simultaneously. These results suggested that this approach can be applied for other antigen and CD8+ T cells of mice and possibly those of humans. We believe that this microfluidics sorting method of the T/APC complex will provide useful information for future T cell immunology research.

Virus-specific T-cell therapy to treat BK polyomavirus infection in bone marrow and solid organ transplant recipients

BK polyomavirus (BKPyV) infection is a major complication of hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT). Treatment options are limited, poorly effective, and have significant toxicities. Cellular therapy using T cells directed against BKPyV is an emerging therapy, and we report efficacy in controlling BKPyV-associated disease in highly immunocompromised patients. Virus-specific T cells (VSTs) against BKPyV were manufactured using either blood from the patient's stem cell donor (donor-derived VSTs) or from unrelated donors (third-party VSTs). VSTs were used to treat BKPyV in 38 HSCT recipients and 3 SOT recipients between June 2017 and December 2019. Overall response rate was 86% in patients treated for BK viremia, 100% in patients treated for hemorrhagic cystitis, and 87% in patients treated for both BK viremia and hemorrhagic cystitis. No infusional toxicity, de novo graft-versus-host disease, or rejection of the organ occurred attributable to the VST infusion. BKPyV-specific immune responses were demonstrated by interferon-γ production by peripheral blood mononuclear cells postinfusion in response to BKPyV antigens. VSTs are a safe and potentially effective strategy to treat BKPyV and associated symptoms in recipients of HSCT and SOT. Cellular therapy should be considered for all patients with BKPyV and underlying immune suppression at risk of complications. This trial was registered at www.clinicaltrials.gov as #NCT02532452.

Adoptive therapy with CMV-specific cytotoxic T lymphocytes depends on baseline CD4+ immunity to mediate durable responses

Adoptive cell therapy using cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CMV-CTLs) has demonstrated efficacy posttransplant. Despite the predicted limited engraftment of CMV-CTLs derived from third-party donors, partially matched third-party donor-derived CMV-CTLs have demonstrated similar response rates to those derived from primary hematopoietic cell transplantation donors. Little is known about the mechanisms through which adoptive cellular therapies mediate durable responses. We performed a retrospective analysis of patients receiving CMV-CTLs for treatment of CMV viremia and/or disease after allogeneic transplant between September of 2009 and January of 2018. We evaluated whether response to adoptively transferred CMV-CTLs correlated with immune reconstitution (IR), using validated CD4+ IR milestones of 50 × 106/L and 200 × 106/L. In this analysis, a cohort of 104 patients received CMV-CTLs derived from a primary transplant donor (n = 25), a third-party donor (n = 76), or both (n = 3). Response to therapy did not increase the likelihood of achieving CD4+ IR milestones at 1 (P = .53 and P > .99) or 2 months (P = .12 and P = .33). The origin of CMV-CTLs did not impact subsequent CD4+ IR. CMV-CTLs appeared to interact with host immunity in mediating responses. Recipients with a baseline CD4 >50 × 106/L had higher response to therapy (P = .02), improved overall survival (P < .001), and protection from CMV-related death (P = .002). Baseline endogenous immunity appears to improve CMV-related and overall survival in this cohort and can be an important marker at the initiation of therapy.

Vaccinated and convalescent donor-derived SARS-CoV-2-specific T cells as adoptive immunotherapy for high-risk COVID-19 patients

Background

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic poses an urgent need for the development of effective therapies for coronavirus disease 2019 (COVID-19).

Methods

We first tested SARS-CoV-2–specific T-cell (CοV-2-ST) immunity and expansion in unexposed donors, COVID-19–infected individuals (convalescent), asymptomatic polymerase chain reaction (PCR)–positive subjects, vaccinated individuals, non–intensive care unit (ICU) hospitalized patients, and ICU patients who either recovered and were discharged (ICU recovered) or had a prolonged stay and/or died (ICU critical). CoV-2-STs were generated from all types of donors and underwent phenotypic and functional assessment.

Results

We demonstrate causal relationship between the expansion of endogenous CoV-2-STs and the disease outcome; insufficient expansion of circulating CoV-2-STs identified hospitalized patients at high risk for an adverse outcome. CoV-2-STs with a similarly functional and non-alloreactive, albeit highly cytotoxic, profile against SARS-CoV-2 could be expanded from both convalescent and vaccinated donors generating clinical-scale, SARS-CoV-2–specific T-cell products with functional activity against both the unmutated virus and its B.1.1.7 and B.1.351 variants. In contrast, critical COVID-19 patient-originating CoV-2-STs failed to expand, recapitulating the in vivo failure of CoV-2–specific T-cell immunity to control the infection. CoV-2-STs generated from asymptomatic PCR-positive individuals presented only weak responses, whereas their counterparts originating from exposed to other seasonal coronaviruses subjects failed to kill the virus, thus disempowering the hypothesis of protective cross-immunity.

Conclusions

Overall, we provide evidence on risk stratification of hospitalized COVID-19 patients and the feasibility of generating powerful CoV-2-ST products from both convalescent and vaccinated donors as an “off-the shelf” T-cell immunotherapy for high-risk patients.

Adoptive transfer of ex vivo expanded SARS-CoV-2-specific cytotoxic lymphocytes: A viable strategy for COVID-19 immunosuppressed patients?

Cellular and humoral response to acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections is on focus of research. We evaluate herein the feasibility of expanding virus‐specific T cells (VST) against SARS‐CoV‐2 ex vivo through a standard protocol proven effective for other viruses. The experiment was performed in three different donors' scenarios: (a) SARS‐CoV‐2 asymptomatic infection/negative serology, (b) SARS‐CoV‐2 symptomatic infection/positive serology, and (c) no history of SARS‐CoV‐2 infection/negative serology. We were able to obtain an expanded VST product from donors 1 and 2 (1.6x and 1.8x increase of baseline VST count, respectively) consisting in CD3 + cells (80.3% and 62.7%, respectively) with CD4 + dominance (60% in both donors). Higher numbers of VST were obtained from the donor 2 as compared to donor 1. T‐cell clonality test showed oligoclonal reproducible peaks on a polyclonal background for both donors. In contrast, VST could be neither expanded nor primed in a donor without evidence of prior infection. This proof‐of‐concept study supports the feasibility of expanding ex vivo SARS‐CoV‐2‐specific VST from blood of convalescent donors. The results raise the question of whether the selection of seropositive donors may be a strategy to obtain cell lines enriched in their SARS‐CoV‐2‐specificity for future adoptive transfer to immunosuppressed patients.

Allogeneic CAR T Cells: An Alternative to Overcome Challenges of CAR T Cell Therapy in Glioblastoma

Chimeric antigen receptor (CAR) T cell therapy has emerged as one of the major breakthroughs in cancer immunotherapy in the last decade. Outstanding results in hematological malignancies and encouraging pre-clinical anti-tumor activity against a wide range of solid tumors have made CAR T cells one of the most promising fields for cancer therapies. CAR T cell therapy is currently being investigated in solid tumors including glioblastoma (GBM), a tumor for which survival has only modestly improved over the past decades. CAR T cells targeting EGFRvIII, Her2, or IL-13Rα2 have been tested in GBM, but the first clinical trials have shown modest results, potentially due to GBM heterogeneity and to the presence of an immunosuppressive microenvironment. Until now, the use of autologous T cells to manufacture CAR products has been the norm, but this approach has several disadvantages regarding production time, cost, manufacturing delay and dependence on functional fitness of patient T cells, often reduced by the disease or previous therapies. Universal “off-the-shelf,” or allogeneic, CAR T cells is an alternative that can potentially overcome these issues, and allow for multiple modifications and CAR combinations to target multiple tumor antigens and avoid tumor escape. Advances in genome editing tools, especially via CRISPR/Cas9, might allow overcoming the two main limitations of allogeneic CAR T cells product, i.e., graft-vs.-host disease and host allorejection. Here, we will discuss how allogeneic CAR T cells could allow for multivalent approaches and alteration of the tumor microenvironment, potentially allowing the development of next generation therapies for the treatment of patients with GBM.

Autologous CMV-specific T cells are a safe adjuvant immunotherapy for primary glioblastoma multiforme

BACKGROUNDThe recent failure of checkpoint-blockade therapies for glioblastoma multiforme (GBM) in late-phase clinical trials has directed interest toward adoptive cellular therapies (ACTs). In this open-label, first-in-human trial, we have assessed the safety and therapeutic potential of cytomegalovirus-specific (CMV-specific) ACT in an adjuvant setting for patients with primary GBM, with an ultimate goal to prevent or delay recurrence and prolong overall survival.METHODSTwenty-eight patients with primary GBM were recruited to this prospective study, 25 of whom were treated with in vitro-expanded autologous CMV-specific T cells. Participants were monitored for safety, progression-free survival, overall survival (OS), and immune reconstitution.RESULTSNo participants showed evidence of ACT-related toxicities. Of 25 evaluable participants, 10 were alive at the completion of follow-up, while 5 were disease free. Reconstitution of CMV-specific T cell immunity was evident and CMV-specific ACT may trigger a bystander effect leading to additional T cell responses to nonviral tumor-associated antigens through epitope spreading. Long-term follow-up of participants treated before recurrence showed significantly improved OS when compared with those who progressed before ACT (median 23 months, range 7-65 vs. median 14 months, range 5-19; P = 0.018). Gene expression analysis of the ACT products indicated that a favorable T cell gene signature was associated with improved long-term survival.CONCLUSIONData presented in this study demonstrate that CMV-specific ACT can be safely used as an adjuvant therapy for primary GBM and, if offered before recurrence, this therapy may improve OS of GBM patients.TRIAL REGISTRATIONanzctr.org.au: ACTRN12615000656538.FUNDINGPhilanthropic funding and the National Health and Medical Research Council (Australia).

'Off-the-shelf' allogeneic antigen-specific adoptive T-cell therapy for the treatment of multiple EBV-associated malignancies

Background

Epstein-Barr virus (EBV), an oncogenic human gammaherpesvirus, is associated with a wide range of human malignancies of epithelial and B-cell origin. Recent studies have demonstrated promising safety and clinical efficacy of allogeneic ‘off-the-shelf’ virus-specific T-cell therapies for post-transplant viral complications.

Methods

Taking a clue from these studies, we developed a highly efficient EBV-specific T-cell expansion process using a replication-deficient AdE1-LMPpoly vector that specifically targets EBV-encoded nuclear antigen 1 (EBNA1) and latent membrane proteins 1 and 2 (LMP1 and LMP2), expressed in latency II malignancies.

Results

These allogeneic EBV-specific T cells efficiently recognized human leukocyte antigen (HLA)-matched EBNA1-expressing and/or LMP1 and LMP2-expressing malignant cells and demonstrated therapeutic potential in a number of in vivo models, including EBV lymphomas that emerged spontaneously in humanized mice following EBV infection. Interestingly, we were able to override resistance to T-cell therapy in vivo using a ‘restriction-switching’ approach, through sequential infusion of two different allogeneic T-cell therapies restricted through different HLA alleles. Furthermore, we have shown that inhibition of the programmed cell death protein-1/programmed death-ligand 1 axis in combination with EBV-specific T-cell therapy significantly improved overall survival of tumor-bearing mice when compared with monotherapy.

Conclusion

These findings suggest that restriction switching by sequential infusion of allogeneic T-cell therapies that target EBV through distinct HLA alleles may improve clinical response.