Adoptive transfer of epstein-barr virus (EBV) nuclear antigen 1-specific t cells as treatment for EBV reactivation and lymphoproliferative disorders after allogeneic stem-cell transplantation

Mechanistic Understanding of EBV+Lymphoproliferative Disease Development After Transplantation

Posttransplant lymphoproliferative disorders (PTLDs) are among the most common malignant complications after transplantation, leading to a drastic reduction in patient survival rates. The majority of PTLDs are tightly linked to Epstein-Barr virus (EBV+PTLDs) and are the result of an uncontrolled proliferation of EBV-infected cells. However, although EBV infections are a common finding in transplant recipients, most patients with high EBV loads will never develop EBV+PTLD. Natural killer cells and EBV-specific CD8+ T lymphocytes are critical for controlling EBV-infected cells, and the impairment of these cytotoxic immune responses facilitates the unfettered proliferation of EBV-infected cells. Recent years have seen a considerable increase in available literature aiming to describe novel risk factors associated with the development of EBV+PTLD, which may critically relate to the strength of EBV-specific natural killer cell and EBV-CD8+ T lymphocyte responses. The accumulation of risk factors and the increased risk of developing EBV+PTLD go hand in hand. On the one hand, most of these risk factors, such as the level of immunosuppression or the EBV donor and recipient serologic mismatch, and distinct genetic risk factors are host related and affect cytotoxic EBV-specific immune responses. On the other hand, there is growing evidence that distinct EBV variants may have an increased malignant potential and are thus more likely to induce EBV+PTLD. Here, we aim to review, from a mechanistic point of view, the risk factors for EBV+PTLD in the host and the infecting EBV variants that may explain why only a minority of transplant recipients develop EBV+PTLD.

Advancing Allogeneic Hematopoietic Stem Cell Transplantation Outcomes through Immunotherapy: A Comprehensive Review of Optimizing Non-CAR Donor T-Lymphocyte Infusion Strategies

Optimized use of prophylactic or therapeutic donor lymphocyte infusions (DLI) is aimed at improving clinical outcomes in patients with malignant and non-malignant hematological diseases who have undergone allogeneic hematopoietic stem cell transplantation (allo-HSCT). Memory T-lymphocytes (CD45RA-/CD45RO+) play a crucial role in immune reconstitution post-HSCT. The infusion of memory T cells is proven to be safe and effective in improving outcomes due to the enhanced reconstitution of immunity and increased protection against viremia, without exacerbating graft-versus-host disease (GVHD) risks. Studies indicate their persistence and efficacy in combating viral pathogens, suggesting a viable therapeutic avenue for patients. Conversely, using virus-specific T cells for viremia control presents challenges, such as regulatory hurdles, cost, and production time compared to CD45RA-memory T lymphocytes. Additionally, the modulation of regulatory T cells (Tregs) for therapeutic use has become an important area of investigation in GVHD, playing a pivotal role in immune tolerance modulation, potentially mitigating GVHD and reducing pharmacological immunosuppression requirements. Finally, donor T cell-mediated graft-versus-leukemia immune responses hold promise in curbing relapse rates post-HSCT, providing a multifaceted approach to therapeutic intervention in high-risk disease scenarios. This comprehensive review underscores the multifaceted roles of T lymphocytes in HSCT outcomes and identifies avenues for further research and clinical application.

Phenotypic and functional characterization of posoleucel, a multivirus-specific T cell therapy for the treatment and prevention of viral infections in immunocompromised patients

BACKGROUND

Deficits in T cell immunity translate into increased risk of severe viral infection in recipients of solid organ and hematopoietic cell transplants. Thus, therapeutic strategies that employ the adoptive transfer of virus-specific T cells are being clinically investigated to treat and prevent viral diseases in these highly immunocompromised patients. Posoleucel is an off-the-shelf multivirus-specific T cell investigational product for the treatment and prevention of infections due to adenovirus, BK virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus 6 or JC virus.

METHODS

Herein we perform extensive characterization of the phenotype and functional profile of posoleucel to illustrate the cellular properties that may contribute to its in vivo activity.

RESULTS AND CONCLUSIONS

Our results demonstrate that posoleucel is enriched for central and effector memory CD4+ and CD8+ T cells with specificity for posoleucel target viruses and expressing a broad repertoire of T cell receptors. Antigen-driven upregulation of cell-surface molecules and production of cytokine and effector molecules indicative of proliferation, co-stimulation, and cytolytic potential demonstrate the specificity of posoleucel and its potential to mount a broad, polyfunctional, and effective Th1-polarized antiviral response upon viral exposure. We also show the low risk for off-target and nonspecific effects as evidenced by the enrichment of posoleucel in memory T cells, low frequency of naive T cells, and lack of demonstrated alloreactivity in vitro. The efficacy of posoleucel is being explored in four placebo-controlled clinical trials in transplant recipients to treat and prevent viral infections (NCT05179057, NCT05305040, NCT04390113, NCT04605484).

Adenovirus- and cytomegalovirus-specific adoptive T-cell therapy in the context of hematologic cell transplant or HIV infection - A single-center experience

BACKGROUND

Reactivation of viral infections, in particular cytomegalovirus (CMV) and adenovirus (ADV), cause morbidity and non-relapse-mortality in states of immune deficiency, especially after allogeneic hematopoietic cell transplantation (allo-HCT). Against the background of few available pharmacologic antiviral agents, limited by toxicities and resistance, adoptive transfer of virus-specific T-cells (VST) is a promising therapeutic approach.

METHODS

We conducted a single-center retrospective analysis of adult patients treated with ADV- or CMV-specific T-cells in 2012-2022. Information was retrieved by review of electronic health records. Primary outcome was a response to VST by decreasing viral load or clinical improvement. Secondary outcomes included overall survival and safety of VST infusion, in particular association with graft-versus-host disease (GVHD).

RESULTS

Ten patients were included, of whom four were treated for ADV, five for CMV, and one for ADV-CMV-coinfection. Cells were derived from stem cell donors (6/10) or third-party donors (4/10). Response criteria were met by six of 10 patients (4/4 ADV, 2/5 CMV, and 0/1 ADV-CMV). Overall survival was 40%. No infusion related adverse events were documented. Aggravation of GVHD after adoptive immunotherapy was observed in two cases, however in temporal association with a conventional donor lymphocyte infusion and a stem cell boost, respectively.

CONCLUSION

In this cohort, CMV- and ADV-specific T-cell therapy appear to be safe and effective. We describe the first reported case of virus-specific T-cell therapy for CMV reactivation not associated with transplantation but with advanced HIV infection. This encourages further evaluation of adoptive immunotherapy beyond the context of allo-HCT.

EBV-positive diffuse large B-cell lymphoma, not otherwise specified: 2024 update on the diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Epstein Barr virus-positive (EBV+) diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS) is an aggressive B-cell lymphoma associated with EBV infection included in the WHO classification of lymphoid neoplasms since 2016. Although historically associated to poor prognosis, outcomes seem to have improved in the era of chemoimmunotherapy.

DIAGNOSIS

The diagnosis is established through meticulous pathological evaluation. Detection of EBV-encoded RNA (EBER) is the standard diagnostic method. The ICC 2022 specifies EBV+ DLBCL, NOS as occurring when >80% of malignant cells express EBER, whereas the WHO-HAEM5 emphasizes that the majority of tumor cells should be EBER positive without setting a defined threshold. The differential diagnosis includes plasmablastic lymphoma, DLBCL associated with chronic inflammation, primary effusion lymphoma, among others.

RISK-STRATIFICATION

The International Prognostic Index (IPI) and the Oyama score can be used for risk-stratification. The Oyama score includes age >70 years and presence of B symptoms. The expression of CD30 and PD-1/PD-L1 are emerging as potential adverse but targetable biomarkers.

MANAGEMENT

Patients with EBV+ DLBCL, NOS, should be staged and managed following similar guidelines than patients with EBV-negative DLBCL. EBV+ DLBCL, NOS, however, might have a worse prognosis than EBV-negative DLBCL in the era of chemoimmunotherapy. Therefore, inclusion of patients in clinical trials when available is recommended. There is an opportunity to study and develop targeted therapy in the management of patients with EBV+ DLBCL, NOS.

EBV T-cell immunotherapy generated by peptide selection has enhanced effector functionality compared to LCL stimulation

Adoptive immunotherapy with Epstein-Barr virus (EBV)-specific T cells is an effective treatment for relapsed or refractory EBV-induced post-transplant lymphoproliferative disorders (PTLD) with overall survival rates of up to 69%. EBV-specific T cells have been conventionally made by repeated stimulation with EBV-transformed lymphoblastoid cell lines (LCL), which act as antigen-presenting cells. However, this process is expensive, takes many months, and has practical risks associated with live virus. We have developed a peptide-based, virus-free, serum-free closed system to manufacture a bank of virus-specific T cells (VST) for clinical use. We compared these with standard LCL-derived VST using comprehensive characterization and potency assays to determine differences that might influence clinical benefits. Multi-parameter flow cytometry revealed that peptide-derived VST had an expanded central memory population and less exhaustion marker expression than LCL-derived VST. A quantitative HLA-matched allogeneic cytotoxicity assay demonstrated similar specific killing of EBV-infected targets, though peptide-derived EBV T cells had a significantly higher expression of antiviral cytokines and degranulation markers after antigen recall. High-throughput T cell receptor-beta (TCRβ) sequencing demonstrated oligoclonal repertoires, with more matches to known EBV-binding complementary determining region 3 (CDR3) sequences in peptide-derived EBV T cells. Peptide-derived products showed broader and enhanced specificities to EBV nuclear antigens (EBNAs) in both CD8 and CD4 compartments, which may improve the targeting of highly expressed latency antigens in PTLD. Importantly, peptide-based isolation and expansion allows rapid manufacture and significantly increased product yield over conventional LCL-based approaches.

SOHO State of the Art Updates and Next Questions | CTLs for Infections Following Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (AHSCT) is an important modality in the treatment of acute leukemia and other hematologic disorders. The post-transplant period is associated with prolonged periods of impaired immune function. Delayed T-cell immune reconstitution is correlated with increased risk of viral, bacterial, and fungal infections. This risk increases with high intensity inductions regimens often required for alternative donor sources. Current therapies for prophylaxis and treatment of these infections are limited by poor efficacy and significant toxicity. Adoptive cell therapy with cytotoxic T lymphocytes (CTL) has proven to be both efficacious and safe in the management of post-transplant viral infections. Recent advances have led to faster production of CTLs and broadened applications for their use. In particular, the generation of third party CTLs has helped ameliorate the problems related to donor availability and product generation time. In this review we aim to describe both the history of CTL use and current advances in the field.

Altered EBV specific immune control in multiple sclerosis

Since the 1980s it is known that immune responses to the Epstein-Barr virus (EBV) are elevated in multiple sclerosis (MS) patients. Recent seroepidemiologial data have shown that this alteration after primary EBV infection identifies individuals with a more than 30-fold increased risk to develop MS. The mechanisms by which EBV infection might erode tolerance for the central nervous system (CNS) in these individuals, years prior to clinical MS onset, remain unclear. In this review I will discuss altered frequencies of EBV life cycle stages and their tissue distribution, EBV with CNS autoantigen cross-reactive immune responses and loss of immune control for autoreactive B and T cells as possible mechanisms. This discussion is intended to stimulate future studies into these mechanisms with the aim to identify candidates for interventions that might correct EBV specific immune control and/or resulting cross-reactivities with CNS autoantigens in MS patients and thereby ameliorate disease activity.

Single-cell sequencing of tumour infiltrating T cells efficiently identifies tumour-specific T cell receptors based on the T cell activation score

Adoptively transferred T cell receptor-engineered T cells are a promising cancer treatment strategy, and the identification of tumour-specific TCRs is essential. Previous studies reported that tumour-reactive T cells and TCRs could be isolated based on the expression of activation markers. However, since T cells with different cell states could not respond uniformly to activation but show a heterogeneous expression profile of activation and effector molecules, isolation of tumour-reactive T cells based on single activation or effector molecules could result in the absence of tumour-reactive T cells; thus, combinations of multiple activation and effector molecules could improve the efficiency of isolating tumour-specific TCRs. We enrolled two patients with lung adenocarcinoma and obtained their tumour infiltrating lymphocytes (TILs) and autologous tumour cells (ATCs). TILs were cocultured with the corresponding ATCs for 12 h and subjected to single-cell RNA sequencing. First, we identified three TCRs with the highest expression levels of IFNG and TNFRSF9 mRNA for each patient, yet only the top one or two recognized the corresponding ATCs in each patient. Next, we defined the activation score based on normalized expression levels of IFNG, IL2, TNF, IL2RA, CD69, TNFRSF9, GZMB, GZMA, GZMK, and PRF1 mRNA for each T cell and then identified three TCRs with the highest activation score for each patient. We found that all three TCRs in each patient could specifically identify corresponding ATCs. In conclusion, we established an efficient approach to isolate tumour-reactive TCRs based on combinations of multiple activation and effector molecules through single-cell RNA sequencing.

Antiviral cellular therapy for enhancing T-cell reconstitution before or after hematopoietic stem cell transplantation (ACES): a two-arm, open label phase II interventional trial of pediatric patients with risk factor assessment

Viral infections remain a major risk in immunocompromised pediatric patients, and virus-specific T cell (VST) therapy has been successful for treatment of refractory viral infections in prior studies. We performed a phase II multicenter study (NCT03475212) for the treatment of pediatric patients with inborn errors of immunity and/or post allogeneic hematopoietic stem cell transplant with refractory viral infections using partially-HLA matched VSTs targeting cytomegalovirus, Epstein-Barr virus, or adenovirus. Primary endpoints were feasibility, safety, and clinical responses (>1 log reduction in viremia at 28 days). Secondary endpoints were reconstitution of antiviral immunity and persistence of the infused VSTs. Suitable VST products were identified for 75 of 77 clinical queries. Clinical responses were achieved in 29 of 47 (62%) of patients post-HSCT including 73% of patients evaluable at 1-month post-infusion, meeting the primary efficacy endpoint (>52%). Secondary graft rejection occurred in one child following VST infusion as described in a companion article. Corticosteroids, graft-versus-host disease, transplant-associated thrombotic microangiopathy, and eculizumab treatment correlated with poor response, while uptrending absolute lymphocyte and CD8 T cell counts correlated with good response. This study highlights key clinical factors that impact response to VSTs and demonstrates the feasibility and efficacy of this therapy in pediatric HSCT.

Virus-Specific T Cells for the Treatment of Systemic Infections Following Allogeneic Hematopoietic Cell and Solid Organ Transplantation

Viral infections are a major source of morbidity and mortality in the context of immune deficiency and immunosuppression following allogeneic hematopoietic cell (allo-HCT) and solid organ transplantation (SOT). The pharmacological treatment of viral infections is challenging and often complicated by limited efficacy, the development of resistance, and intolerable side effects. A promising strategy to rapidly restore antiviral immunity is the adoptive transfer of virus-specific T cells (VST). This therapy involves the isolation and ex vivo expansion or direct selection of antigen-specific T cells from healthy seropositive donors, followed by infusion into the patient. This article provides a practical guide to VST therapy by reviewing manufacturing techniques, donor selection, and treatment indications. The safety and efficacy data of VSTs gathered in clinical trials over nearly 30 years is summarized. Current challenges and limitations are discussed, as well as opportunities for further research and development.

Targeting latent viral infection in EBV-associated lymphomas

Epstein-Barr virus (EBV) contributes to the development of a significant subset of human lymphomas. As a herpes virus, EBV can transition between a lytic state which is required to establish infection and a latent state where a limited number of viral antigens are expressed which allows infected cells to escape immune surveillance. Three broad latency programs have been described which are defined by the expression of viral proteins RNA, with latency I being the most restrictive expressing only EBV nuclear antigen 1 (EBNA1) and EBV-encoded small RNAs (EBERs) and latency III expressing the full panel of latent viral genes including the latent membrane proteins 1 and 2 (LMP1/2), and EBNA 2, 3, and leader protein (LP) which induce a robust T-cell response. The therapeutic use of EBV-specific T-cells has advanced the treatment of EBV-associated lymphoma, however this approach is only effective against EBV-associated lymphomas that express the latency II or III program. Latency I tumors such as Burkitt lymphoma (BL) and a subset of diffuse large B-cell lymphomas (DLBCL) evade the host immune response to EBV and are resistant to EBV-specific T-cell therapies. Thus, strategies for inducing a switch from the latency I to the latency II or III program in EBV+ tumors are being investigated as mechanisms to sensitize tumors to T-cell mediated killing. Here, we review what is known about the establishment and regulation of latency in EBV infected B-cells, the role of EBV-specific T-cells in lymphoma, and strategies to convert latency I tumors to latency II/III.

[Anything that can go wrong: cytotoxic cells and their control of Epstein-Barr virus]

Epstein-Barr virus (EBV) is an gamma of herpes virus affecting exclusively humans, was the first oncogenic virus described and is associated with over seven different cancers. Curiously, the exchange of genes during viral infections has enabled the evolution of other cellular organisms, favoring new functions and the survival of the host. EBV has been co-evolving with mammals for hundreds of millions of years, and more than 95% of adults have been infected in one moment of their life. The infection is acquired primarily during childhood, in most cases as an asymptomatic infection. However, during adolescence or young adulthood, around 10 to 30% develop infectious mononucleosis. The NK and CD8+ T cells are the cytotoxic cells of the immune system that focus on antiviral responses. Importantly, an essential role of NK and CD8+ T cells has been demonstrated during the control and elimination of EBV-infected cells. Nonetheless, when the cytotoxic function of these cells is compromised, the infection increases the risk of developing lymphoproliferative diseases and cancer, often fatal. In this review, we delineate EBV infection and the importance of cytotoxic responses by NK and CD8+ T cells during the control and elimination of EBV-infected cells. Furthermore, we briefly discuss the main inborn errors of immunity that compromise cytotoxic responses by NK and CD8+ T cells, and how this scenario affects the antiviral response during EBV infection. Finally, we conclude the review by underlying the need for an effective EBV vaccine capable of preventing infection and the consequent development of malignancies and autoimmune diseases.

Nasopharyngeal carcinoma: current views on the tumor microenvironment's impact on drug resistance and clinical outcomes

The incidence of nasopharyngeal carcinoma (NPC) exhibits significant variations across different ethnic groups and geographical regions, with Southeast Asia and North Africa being endemic areas. Of note, Epstein-Barr virus (EBV) infection is closely associated with almost all of the undifferentiated NPC cases. Over the past three decades, radiation therapy and chemotherapy have formed the cornerstone of NPC treatment. However, recent advancements in immunotherapy have introduced a range of promising approaches for managing NPC. In light of these developments, it has become evident that a deeper understanding of the tumor microenvironment (TME) is crucial. The TME serves a dual function, acting as a promoter of tumorigenesis while also orchestrating immunosuppression, thereby facilitating cancer progression and enabling immune evasion. Consequently, a comprehensive comprehension of the TME and its intricate involvement in the initiation, progression, and metastasis of NPC is imperative for the development of effective anticancer drugs. Moreover, given the complexity of TME and the inter-patient heterogeneity, personalized treatment should be designed to maximize therapeutic efficacy and circumvent drug resistance. This review aims to provide an in-depth exploration of the TME within the context of EBV-induced NPC, with a particular emphasis on its pivotal role in regulating intercellular communication and shaping treatment responses. Additionally, the review offers a concise summary of drug resistance mechanisms and potential strategies for their reversal, specifically in relation to chemoradiation therapy, targeted therapy, and immunotherapy. Furthermore, recent advances in clinical trials pertaining to NPC are also discussed.

Virus-specific T-cells from third party or transplant donors for treatment of EBV lymphoproliferative diseases arising post hematopoietic cell or solid organ transplantation

EBV+ lymphomas constitute a significant cause of morbidity and mortality in recipients of allogeneic hematopoietic cell (HCT) and solid organ transplants (SOT). Phase I and II trials have shown that in HCT recipients, adoptive transfer of EBV-specific T-cells from the HCT donor can safely induce durable remissions of EBV+ lymphomas including 70->90% of patients who have failed to respond to treatment with Rituximab. More recently, EBV-specific T-cells generated from allogeneic 3rd party donors have also been shown to induce durable remission of EBV+ lymphomas in Rituximab refractory HCT and SOT recipients. In this review, we compare results of phase I and II trials of 3rd party and donor derived EBV-specific T-cells. We focus on the attributes and limitations of each product in terms of access, safety, responses achieved and durability. The limited data available regarding donor and host factors contributing to T cell persistence is also described. We examine factors contributing to treatment failures and approaches to prevent or salvage relapse. Lastly, we summarize strategies to further improve results for virus-specific immunotherapies for post-transplant EBV lymphomas.

Rituximab for posttransplant lymphoproliferative disorder - therapeutic, preemptive, or prophylactic?

To minimize mortality due to posttransplant lymphoproliferative disorder (PTLD), the following strategies have been used: (1) Therapy without EBV Monitoring, i.e., administration of rituximab after PTLD diagnosis, usually by biopsy, in the absence of routine Epstein-Barr virus (EBV) DNAemia monitoring, (2) Prompt Therapy, i.e., monitoring EBV DNAemia, searching for PTLD by imaging when the DNAemia has exceeded a pre-specified threshold, and administration of rituximab if the imaging is consistent with PTLD, (3) Preemptive Therapy, i.e., monitoring EBV DNAemia and administration of rituximab when the DNAemia has exceeded a pre-specified threshold, and (4) Prophylaxis, i.e., administration of rituximab to all transplant recipients. The superiority of one of these strategies over the other strategies has not been established. Here we review the pros and cons of each strategy. Preemptive therapy or prophylaxis may currently be preferred for patients who are at a high risk of dying due to PTLD. However, Therapy without EBV Monitoring may be used for both high- and low-risk patients in the future, if effective and relatively non-toxic therapies for rituximab-refractory PTLD (e.g., EBV-specific T cells) have become easily available.

Antibody-mediated delivery of viral epitopes to redirect EBV-specific CD8+ T-cell immunity towards cancer cells

Antibody-mediated delivery of immunogenic epitopes to redirect virus-specific CD8+ T-cells towards cancer cells is an emerging and promising new therapeutic strategy. These so-called antibody-epitope conjugates (AECs) rely on the proteolytic release of the epitopes close to the tumor surface for presentation by HLA class I molecules to eventually redirect and activate virus-specific CD8+ T-cells towards tumor cells. We fused the immunogenic EBV-BRLF1 epitope preceded by a protease cleavage site to the C-terminus of the heavy and/or light chains of cetuximab and trastuzumab. We evaluated these AECs and found that, even though all AECs were able to redirect the EBV-specific T-cells, AECs with an epitope fused to the C-terminus of the heavy chain resulted in higher levels of T-cell activation compared to AECs with the same epitope fused to the light chain of an antibody. We observed that all AECs were depending on the presence of the antibody target, that the level of T-cell activation correlated with expression levels of the antibody target, and that our AECs could efficiently deliver the BRLF1 epitope to cancer cell lines from different origins (breast, ovarian, lung, and cervical cancer and a multiple myeloma). Moreover, in vivo, the AECs efficiently reduced tumor burden and increased the overall survival, which was prolonged even further in combination with immune checkpoint blockade. We demonstrate the potential of these genetically fused AECs to redirect the potent EBV-specific T-cells towards cancer in vitro and in vivo.

Modulation of Epstein-Barr-Virus (EBV)-Associated Cancers by Co-Infections

The oncogenic and persistent Epstein Barr virus (EBV) is carried by more than 95% of the human adult population. While asymptomatic in most of these, EBV can cause a wide variety of malignancies of lymphoid or epithelial cell origin. Some of these are also associated with co-infections that either increase EBV-induced tumorigenesis or weaken its immune control. The respective pathogens include Kaposi-sarcoma-associated herpesvirus (KSHV), Plasmodium falciparum and human immunodeficiency virus (HIV). In this review, I will discuss the respective tumor entities and possible mechanisms by which co-infections increase the EBV-associated cancer burden. A better understanding of the underlying mechanisms could allow us to identify crucial features of EBV-associated malignancies and defects in their immune control. These could then be explored to develop therapies against the respective cancers by targeting EBV and/or the respective co-infections with pathogen-specific therapies or vaccinations.

Virus-Specific T Cells: Promising Adoptive T Cell Therapy Against Infectious Diseases Following Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a life-saving therapy for various hematologic disorders. Due to the bone marrow suppression and its long recovery period, secondary infections, like cytomegalovirus (CMV), Epstein-Bar virus (EBV), and adenovirus (AdV), are the leading causes of morbidity and mortality in HSCT cases. Drug resistance to the antiviral pharmacotherapies makes researchers develop adoptive T cell therapies like virus-specific T cell therapy. These studies have faced major challenges such as finding the most effective T cell expansion methods, isolating the expected subtype, defining the functionality of the end-cell population, product quality control, and clinical complications after the injection. This review discusses the viral infections after HSCT, T cells characteristics during chronic viral infection, application of virus-specific T cells (VSTs) for refractory infections, standard methods for producing VSTs and their limitation, clinical experiences on VSTs, focusing on outcomes and side effects that can be helpful in decision-making for patients and further researches.

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.

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.

Adoptive T-cell therapy targeting Epstein-Barr virus as a treatment for multiple sclerosis

Emergence of a definitive link between Epstein-Barr virus (EBV) and multiple sclerosis has provided an impetus to develop immune-based therapies to target EBV-infected B cells. Initial studies with autologous EBV-specific T-cell therapy demonstrated that this therapy is safe with minimal side effects and more importantly multiple patients showed both symptomatic and objective neurological improvements including improved quality of life, reduction of fatigue and reduced intrathecal IgG production. These observations have been successfully extended to an 'off-the-shelf' allogeneic EBV-specific T-cell therapy manufactured using peripheral blood lymphocytes of healthy seropositive individuals. This adoptive immunotherapy has also been shown to be safe with encouraging clinical responses. Allogeneic EBV T-cell therapy overcomes some of the limitations of autologous therapy and can be rapidly delivered to patients with improved therapeutic potential.

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.

The role of viruses in HIV-associated lymphomas

Lymphomas are among the most common cancers in people with HIV (PWH). The lymphoma subtypes and pathogenesis of lymphoma in PWH are different from the immunocompetent population. It is well-known that HIV causes severe CD4+ T cell lymphopenia in the absence of antiretroviral therapy (ART); however, the risk of developing certain subtypes of lymphoma remains elevated even in people receiving ART with preserved CD4+ T cells. HIV contributes to lymphomagenesis and causes decreased immune surveillance via T cell depletion and dysregulation, B cell dysregulation, and the potential contribution of HIV-encoded proteins. The oncogenic gammaherpesviruses, Epstein-Barr virus (EBV) and Kaposi sarcoma herpesvirus (KSHV, also known as human herpesvirus 8), are the causative agents in the majority of HIV-associated lymphomas. HIV-associated T cell depletion and dysregulation allows EBV and KSHV to proliferate in infected B cells. Specific EBV- and KSHV-encoded proteins participate in B cell activation, and proliferation leading to B cell transformation. Understanding the distinct pathogenesis of HIV-associated lymphomas affords opportunities to develop therapies that specifically target these unique aspects and improve lymphoma outcomes in PWH. Agents being studied that target the specific roles of HIV, EBV, and KSHV in lymphomagenesis include immunotherapies, targeted agents, and cellular therapies.

Therapeutic approaches to Epstein-Barr virus cancers

Epstein-Barr virus (EBV) establishes a lifelong latent infection that can be a causal agent for a diverse spectrum of cancers and autoimmune disease. A complex and dynamic viral lifecycle evades eradication by the host immune system and confounds antiviral therapeutic strategies. To date, there are no clinically approved vaccines or therapies that selectively target EBV as the underlying cause of EBV-associated disease. Here, we review the challenges and recent advances in the development of EBV-specific therapeutics for treatment of EBV-associated cancers.

Immunocompromised host section: Adoptive T-cell therapy for dsDNA viruses in allogeneic hematopoietic cell transplant recipients

PURPOSE OF REVIEW

Double-stranded DNA (dsDNA) viruses remain important causes of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). As treatment options are limited, adoptive therapy with virus-specific T cells (VST) is promising in restoring immunity and thereby preventing and treating virus infections. Here we review current evidence and recent advances in the field of VST for dsDNA viruses in allogeneic HCT recipients.

RECENT FINDINGS

Four different protocols for VST generation are currently used in clinical trials, and various products including multivirus-specific and off-the-shelf products are under investigation for prophylaxis, preemptive therapy or treatment. Data from nearly 1400 dsDNA-VST applications in allogeneic HCT patients have been published and demonstrated its safety. Although Epstein-Barr virus, cytomegalovirus, and adenovirus-specific T-cell therapy studies have predominated over the past 25 years, additional human herpes viruses were added to multivirus-specific T cells over the last decade and clinical evidence for polyomavirus-specific VST has just recently emerged. Response rates of around 70-80% have been reported, but cautious interpretation is warranted as data are predominantly from phase 1/2 studies and clinical efficacy needs to be confirmed in phase 3 studies.

SUMMARY

Investigation on the 'ideal' composition of VST is ongoing. Several products recently entered phase 3 trials and may allow widespread clinical use in the near future.

EBV-positive diffuse large B-cell lymphoma, not otherwise specified: 2022 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Epstein Barr virus-positive (EBV+) diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS) is an entity included in the WHO classification of lymphoid neoplasms since 2016. EBV+ DLBCL, NOS, is an aggressive B-cell lymphoma associated with EBV infection, and a poor prognosis with standard chemotherapeutic approaches.

DIAGNOSIS

The diagnosis is made through a careful pathological evaluation. Detection of EBV-encoded RNA (EBER) is considered standard for diagnosis; however, a clear cutoff for percentage of positive cells has not been defined. The differential diagnosis includes plasmablastic lymphoma (PBL), DLBCL associated with chronic inflammation, primary effusion lymphoma (PEL), among others.

RISK-STRATIFICATION

The International Prognostic Index (IPI) and the Oyama score can be used for risk-stratification. The Oyama score includes age >70 years and presence of B symptoms. The expression of CD30 and PD-1/PD-L1 are emerging as potential adverse but targetable biomarkers.

MANAGEMENT

Patients with EBV+ DLBCL, NOS, should be staged and managed following similar guidelines than patients with EBV-negative DLBCL. EBV+ DLBCL, NOS, however, might have a worse prognosis than EBV-negative DLBCL in the era of chemoimmunotherapy. Therefore, the inclusion of patients in clinical trials when available is recommended. There is an opportunity to study and develop targeted therapy in the management of patients with EBV+ DLBCL, NOS.

Utility of Epstein-Barr Viral Load in Blood for Diagnosis and Predicting Prognosis of Lymphoma: A Comparison with Epstein-Barr Virus-Encoded RNA in Situ Hybridization

Epstein-Barr virus (EBV) is a ubiquitous pathogen that persists in a small portion of B cells after primary infection and is etiologically associated with multiple lymphoma subtypes. Herein, we evaluated the clinical utility of EBV real-time quantitative PCR in comparison with the widely used Epstein-Barr virus-encoded RNA (EBER) in situ hybridization (ISH) method in 912 patients with four lymphoma subtypes: diffuse large B-cell lymphoma (DLBCL), extranodal natural killer/T-cell lymphoma (ENKTCL), peripheral T-cell lymphoma (PTCL), and Hodgkin lymphoma. We also assessed the impact of EBV positivity determined from each method or a combination of both methods on mortality using Kaplan-Meier survival analysis and Cox proportional hazard regression. EBV real-time quantitative PCR identified more positive cases than EBER-ISH for all subtypes, except ENKTCL. EBV DNA-positive patients with ENKTCL and PTCL displayed poorer overall survival (OS) than EBV DNA-negative patients (P = 0.0016 and P = 0.0013, respectively). In addition, among those with EBER-positive DLBCL and ENKTL and those with EBER-negative PTCL, OS was significantly worse for EBV DNA-positive patients (P = 0.027, P = 0.0016, and P = 0.0018, respectively). EBER positivity was associated with worse OS for DLBCL (P = 0.037), in reanalyses including only the 862 patients with unambiguous EBER-ISH results. Overall, EBV DNA positivity is a more effective prognostic marker than EBER-ISH status for patients with certain lymphoma subtypes.

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.

The generation and application of antigen-specific T cell therapies for cancer and viral-associated disease

Immunotherapy with antigen-specific T cells is a promising, targeted therapeutic option for patients with cancer as well as for immunocompromised patients with virus infections. In this review, we characterize and compare current manufacturing protocols for the generation of T cells specific to viral and non-viral tumor-associated antigens. Specifically, we discuss: (1) the different methodologies to expand virus-specific T cell and non-viral tumor-associated antigen-specific T cell products, (2) an overview of the immunological principles involved when developing such manufacturing protocols, and (3) proposed standardized methodologies for the generation of polyclonal, polyfunctional antigen-specific T cells irrespective of donor source. Ex vivo expanded cells have been safely administered to treat numerous patients with virus-associated malignancies, hematologic malignancies, and solid tumors. Hence, we have performed a comprehensive review of the clinical trial results evaluating the safety, feasibility, and efficacy of these products in the clinic. In summary, this review seeks to provide new insights regarding antigen-specific T cell technology to benefit a rapidly expanding T cell therapy field.

Reconstitution of EBV-directed T cell immunity by adoptive transfer of peptide-stimulated T cells in a patient after allogeneic stem cell transplantation for AITL

Reconstitution of the T cell repertoire after allogeneic stem cell transplantation is a long and often incomplete process. As a result, reactivation of Epstein-Barr virus (EBV) is a frequent complication that may be treated by adoptive transfer of donor-derived EBV-specific T cells. We generated donor-derived EBV-specific T cells by stimulation with peptides representing defined epitopes covering multiple HLA restrictions. T cells were adoptively transferred to a patient who had developed persisting high titers of EBV after allogeneic stem cell transplantation for angioimmunoblastic T-cell lymphoma (AITL). T cell receptor beta (TCRβ) deep sequencing showed that the T cell repertoire of the patient early after transplantation (day 60) was strongly reduced and only very low numbers of EBV-specific T cells were detectable. Manufacturing and in vitro expansion of donor-derived EBV-specific T cells resulted in enrichment of EBV epitope-specific, HLA-restricted T cells. Monitoring of T cell clonotypes at a molecular level after adoptive transfer revealed that the dominant TCR sequences from peptide-stimulated T cells persisted long-term and established an EBV-specific TCR clonotype repertoire in the host, with many of the EBV-specific TCRs present in the donor. This reconstituted repertoire was associated with immunological control of EBV and with lack of further AITL relapse.

A characteristic feature of all herpesviruses is their persistence in the host’s body after primary infection. Hence, the host’s immune system is confronted with the problem to control these viruses life-long. When the immune system is severely compromised, for example after stem cell transplantation from a foreign (allogeneic) donor, these viruses can reappear, as they persist in the host’s body life-long after primary infection. Epstein-Barr virus (EBV) is a herpesvirus that can cause life-threatening complications after stem cell transplantation and only reinforcement of the host’s immune system can reestablish control over the virus. Here we show that ex vivo manufactured EBV-specific T cells can reestablish long-term control of EBV and that these cells persist in the host’s body over months. These results give us a better understanding of viral immune reconstitution post-transplant and of clinically-relevant T cell populations against EBV.

Post-transplant Lymphoproliferative Disorder Following Cardiac Transplantation

Post-transplant lymphoproliferative disorder (PTLD) is a spectrum of lymphoid conditions frequently associated with the Epstein Barr Virus (EBV) and the use of potent immunosuppressive drugs after solid organ transplantation. PTLD remains a major cause of long-term morbidity and mortality following heart transplantation (HT). Epstein-Barr virus (EBV) is a key pathogenic driver in many PTLD cases. In the majority of PTLD cases, the proliferating immune cell is the B-cell, and the impaired T-cell immune surveillance against infected B cells in immunosuppressed transplant patients plays a key role in the pathogenesis of EBV-positive PTLD. Preventive screening strategies have been attempted for PTLD including limiting patient exposure to aggressive immunosuppressive regimens by tailoring or minimizing immunosuppression while preserving graft function, anti-viral prophylaxis, routine EBV monitoring, and avoidance of EBV seromismatch. Our group has also demonstrated that conversion from calcineurin inhibitor to the mammalian target of rapamycin (mTOR) inhibitor, sirolimus, as a primary immunosuppression was associated with a decreased risk of PTLD following HT. The main therapeutic measures consist of immunosuppression reduction, treatment with rituximab and use of immunochemotherapy regimens. The purpose of this article is to review the potential mechanisms underlying PTLD pathogenesis, discuss recent advances, and review potential therapeutic targets to decrease the burden of PTLD after HT.

Impact of Epstein-Barr Virus on Peripheral T-Cell Lymphoma Not Otherwise Specified and Angioimmunoblastic T-Cell Lymphoma

Purpose

The significance of Epstein-Barr virus (EBV) infections for the prognosis of patients with peripheral T-cell lymphomas (PTCLs), specifically angioimmunoblastic T-cell lymphoma (AITL) and PTCL not otherwise specified (PTCL-NOS), remains unclear. The Epstein-Barr encoding region can be used to detect EBV in tissue sections by in situ hybridization (ISH) and by polymerase chain reaction (PCR) assays of peripheral blood samples from patients with PTCLs. This study compared the outcomes patients with AITL or PTCL-NOS for whom the presence of EBV infection was assessed by these two methods.

Patients and Methods

This was a retrospective study of patients newly diagnosed with AITL or PTCL-NOS. All patients were selected from a single transplantation center. EBV-positive lymphomas were detected at the time of diagnosis in tissue sections by ISH or in the blood by PCR.

Results

Out of a cohort of 140 patients with histologically confirmed AITL or PTCL-NOS, 105 were EBV-positive. The 3-year overall survival of patients with EBV-positive TCL was 43.3% compared to 68.6% in patients with EBV-negative TCL (p = .01). Patients who were treated with autologous or allogeneic hematopoietic stem cell transplantation (n = 28 and n = 11, respectively) or chemotherapy alone (n = 66) had 3-year survival rates of 67.0%, 62.3%, and 30.2%, respectively (p <.02). Patients with EBV-positive TCL had a better prognosis after treatment with hematopoietic stem cell transplantation compared to chemotherapy alone, but no difference was seen among patients with EBV-negative TCL.

Conclusions

EBV infection was shown to negatively affect the clinical outcomes of patients with TCL. Stem cell transplantation has been found to be an effective treatment for EBV-associated lymphomas. Further investigations are warranted to determine the optimal treatment for these patients.

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.

Burkitt lymphoma with a granulomatous reaction: an M1/Th1-polarised microenvironment is associated with controlled growth and spontaneous regression

AIMS

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that, in some instances, may show a granulomatous reaction associated with a favourable prognosis and occasional spontaneous regression. In the present study, we aimed to define the tumour microenvironment (TME) in four such cases, two of which regressed spontaneously.

METHODS AND RESULTS

All cases showed aggregates of tumour cells with the typical morphology, molecular cytogenetics and immunophenotype of BL surrounded by a florid epithelioid granulomatous reaction. All four cases were Epstein-Barr virus (EBV)-positive with type I latency. Investigation of the TME showed similar features in all four cases. The analysis revealed a proinflammatory response triggered by Th1 lymphocytes and M1 polarised macrophages encircling the neoplastic cells with a peculiar topographic distribution.

CONCLUSIONS

Our data provide an in-vivo picture of the role that specific immune cell subsets might play during the early phase of BL, which may be capable of maintaining the tumour in a self-limited state or inducing its regression. These novel results may provide insights into new potential therapeutic avenues in EBV-positive BL patients in the era of cellular immunotherapy.

Co-Stimulatory Molecules during Immune Control of Epstein Barr Virus Infection

The Epstein Barr virus (EBV) is one of the prominent human tumor viruses, and it is efficiently immune-controlled in most virus carriers. Cytotoxic lymphocytes strongly expand during symptomatic primary EBV infection and in preclinical in vivo models of this tumor virus infection. In these models and patients with primary immunodeficiencies, antibody blockade or deficiencies in certain molecular pathways lead to EBV-associated pathologies. In addition to T, NK, and NKT cell development, as well as their cytotoxic machinery, a set of co-stimulatory and co-inhibitory molecules was found to be required for EBV-specific immune control. The role of CD27/CD70, 4-1BB, SLAMs, NKG2D, CD16A/CD2, CTLA-4, and PD-1 will be discussed in this review. Some of these have just been recently identified as crucial for EBV-specific immune control, and for others, their important functions during protection were characterized in in vivo models of EBV infection and its immune control. These insights into the phenotype of cytotoxic lymphocytes that mediate the near-perfect immune control of EBV-associated malignancies might also guide immunotherapies against other tumors in the future.

Genome-Wide Profiling of Epstein-Barr Virus (EBV) Isolated from EBV-Related Malignancies

Epstein–Barr virus (EBV) is the cause of certain cancers, such as Burkitt lymphoma, Hodgkin lymphoma, NK/T cell lymphoma, nasopharyngeal carcinoma, and a subset of gastric carcinomas. The genome-wide characteristics of EBV are essential to understand the diversity of strains isolated from EBV-related malignancies, provide the first opportunity to test the general validity of the EBV genetic map and explore recombination, geographic variation, and the major features of variation in this virus. Moreover, understanding more about EBV sequence variations isolated from EBV-related malignancies might give important implications for the development of effective prophylactic and therapeutic vaccine approaches targeting the personalized or geographic-specific EBV antigens in these aggressive diseases. In this chapter, we will mainly focus on the EBV genome-wide profiling in three common EBV-related cancers in Asia, including nasopharyngeal carcinoma, EBV-associated gastric carcinoma, and NK/T-cell lymphoma.

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.

Double-refractory Hodgkin lymphoma: tackling relapse after brentuximab vedotin and checkpoint inhibitors

The approval of brentuximab vedotin (BV) and checkpoint inhibitors (CPI) has revolutionized the management of relapsed/refractory classical Hodgkin lymphoma (cHL) patients. In recent years these agents have rapidly moved to earlier lines of therapy, including post-autologous hematopoietic cell transplant (auto-HCT) consolidation, pre-HCT salvage, and the frontline treatment setting. This shift in practice means that double-refractory (refractory to both BV and CPI) cHL is becoming an increasingly common clinical problem. In patients who are not eligible for clinical trials, conventional cytotoxic and targeted therapies (off label) may be a potential option. In patients who are transplant eligible, early referral to allogeneic HCT should be considered given the significant improvement in transplant outcomes in the contemporary era. Cellular therapy options including CD30.chimeric antigen receptor T cells, Epstein-Barr virus-directed cytotoxic T cells, and CD16A/30 bispecific natural killer cell engagers appear promising and are currently in clinical trials.

Clinical and Therapeutic Implications of Epstein-Barr Virus in HIV-Related Lymphomas

The incidence of lymphomas is increased in people living with HIV (PLWH). Aggressive B-cell non-Hodgkin lymphomas (NHLs) are the most common and are considered an AIDS-defining cancer (ADC). Although Hodgkin lymphoma (HL) is not considered an ADC, its incidence is also increased in PLWH. Among all HIV-related lymphomas (HRL), the prevalence of Epstein-Barr virus (EBV) is high. It has been shown that EBV is involved in different lymphomagenic mechanisms mediated by some of its proteins, contributing to the development of different lymphoma subtypes. Additionally, cooperation between both HIV and EBV can lead to the proliferation of aberrant B-cells, thereby being an additional lymphomagenic mechanism in EBV-associated HRL. Despite the close relationship between EBV and HRL, the impact of EBV on clinical aspects has not been extensively studied. These lymphomas are treated with the same therapeutic regimens as the general population in combination with cART. Nevertheless, new therapeutic strategies targeting EBV are promising for these lymphomas. In this article, the different types of HRL are extensively reviewed, focusing on the influence of EBV on the epidemiology, pathogenesis, clinical presentation, and pathological characteristics of each lymphoma subtype. Moreover, novel therapies targeting EBV and future strategies to treat HRL harboring EBV are discussed.

Cytometric analysis of T cell phenotype using cytokine profiling for improved manufacturing of an EBV-specific T cell therapy

Adoptive immunotherapy using Epstein–Barr Virus (EBV)‐specific T cells is a potentially curative treatment for patients with EBV‐related malignancies where other clinical options have proved ineffective. We describe improved good manufacturing practice (GMP)‐compliant culture and analysis processes for conventional lymphoblastoid cell line (LCL)‐driven EBV‐specific T cell manufacture, and describe an improved phenotyping approach for analysing T cell products. We optimized the current LCL‐mediated clinical manufacture of EBV‐specific T cells to establish an improved process using xenoprotein‐free GMP‐compliant reagents throughout, and compared resulting products with our previous banked T cell clinical therapy. We assessed effects of changes to LCL:T cell ratio in T cell expansion, and developed a robust flow cytometric marker panel covering T cell memory, activation, differentiation and intracellular cytokine release to characterize T cells more effectively. These data were analysed using a t‐stochastic neighbour embedding (t‐SNE) algorithm. The optimized GMP‐compliant process resulted in reduced cell processing time and improved retention and expansion of central memory T cells. Multi‐parameter flow cytometry determined the optimal protocol for LCL stimulation and expansion of T cells and demonstrated that cytokine profiling using interleukin (IL)‐2, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ was able to determine the differentiation status of T cells throughout culture and in the final product. We show that fully GMP‐compliant closed‐process culture of LCL‐mediated EBV‐specific T cells is feasible, and profiling of T cells through cytokine expression gives improved characterization of start material, in‐process culture conditions and final product. Visualization of the complex multi‐parameter flow cytometric data can be simplified using t‐SNE analysis.

Epstein-Barr virus-associated post-transplant lymphoproliferative disorders: beyond chemotherapy treatment

Post-transplant lymphoproliferative disorder (PTLD) is a rare but life-threatening complication of both allogeneic solid organ (SOT) and hematopoietic cell transplantation (HCT). The histology of PTLD ranges from benign polyclonal lymphoproliferation to a lesion indistinguishable from classic monoclonal lymphoma. Most commonly, PTLDs are Epstein-Barr virus (EBV) positive and result from loss of immune surveillance over EBV. Treatment for PTLD differs from the treatment for typical non-Hodgkin lymphoma because prognostic factors are different, resistance to treatment is unique, and there are specific concerns for organ toxicity. While recipients of HCT have a limited time during which they are at risk for this complication, recipients of SOT have a lifelong requirement for immunosuppression, so approaches that limit compromising or help restore immune surveillance are of high interest. Furthermore, while EBV-positive and EBV-negative PTLDs are not intrinsically resistant to chemotherapy, the poor tolerance of chemotherapy in the post-transplant setting makes it essential to minimize potential treatment-related toxicities and explore alternative treatment algorithms. Therefore, reduced-toxicity approaches such as single-agent CD20 monoclonal antibodies or bortezomib, reduced dosing of standard chemotherapeutic agents, and non-chemotherapy-based approaches such as cytotoxic T cells have all been explored. Here, we review the chemotherapy and non-chemotherapy treatment landscape for PTLD.

Nanocarrier vaccines for SARS-CoV-2

The SARS-CoV-2 global pandemic has seen rapid spread, disease morbidities and death associated with substantive social, economic and societal impacts. Treatments rely on re-purposed antivirals and immune modulatory agents focusing on attenuating the acute respiratory distress syndrome. No curative therapies exist. Vaccines remain the best hope for disease control and the principal global effort to end the pandemic. Herein, we summarize those developments with a focus on the role played by nanocarrier delivery.

Virus-specific T cells for malignancies - then, now and where to?

Purpose of Review

Virus-associated malignancies are a global health burden, constituting 10-12% of cancers worldwide. As these tumors express foreign viral antigens that can elicit specific T cell responses, virus-directed immunotherapies are a promising treatment strategy. Specifically, adoptive cell transfer of virus-specific T cells (VSTs) has demonstrated the potential to eradicate cancers associated with certain viruses.

Recent Findings

Initial studies in 1990s first showed that VSTs specific for the Epstein-Barr virus (EBVSTs) can induce complete remissions in patients with post-transplant lymphoproliferative disease. Since then, studies have validated the specificity and safety of VSTs in multiple lymphomas and solid malignancies. However, challenges remain to optimize this platform for widespread use, including enhancing potency and persistence, overcoming the immunosuppressive tumor microenvironment, and streamlining manufacturing processes that comply with regulatory requirements.

Summary

This review focuses on data from clinical trials evaluating VSTs directed against three viruses (EBV, HPV and MCPyV), as well as recent preclinical and clinical advances, and potential future directions.

Innate and Adaptive Immune Correlates of Chronic and Self-limiting EBV DNAemia in Solid-organ Transplant Recipients

BACKGROUND

Epstein-Barr virus (EBV) DNAemia is a major risk factor for posttransplant lymphoproliferative disorder; however, immune correlates of EBV DNAemia in the transplant setting are limited.

METHODS

Peripheral blood mononuclear cells were collected from 30 transplant recipients with self-limiting EBV DNAemia (SLD; n = 11) or chronic EBV DNAemia (CD; n = 19) at enrollment and 4-8 weeks later. Mass cytometry was used to characterize innate and T-cell immune correlates of EBV DNAemia. Furthermore, flow cytometry was used to measure the frequency of EBV-specific T-cell responses between groups following stimulation with an EBV-infected cell lysate.

RESULTS

Unsupervised analysis of the innate compartment (CD3CD19 cells) identified 5 CD11c clusters at higher abundance in the SLD group (false discovery rate ≤ 1%). These clusters expressed CD11b, CD45RO, CD14, CD123, CD127, and CD38, among others. Unsupervised profiling of the T-cell compartment (CD3CD19) revealed 2 CD4 T-cell clusters at higher frequency among those with SLD (false discovery rate ≤ 1%), which expressed CD45RA, CCR7, CD27, CD28, and CD40L-suggestive of a naive T cell (TN). Manual biaxial gating confirmed increased frequencies of conventional dendritic cells (3.1% versus 2.1%; P = 0.023) and CD4 TN (4.4% versus 1.9%; P = 0.018) among those with SLD. Last, frequencies of interferon-γ-producing EBV-specific CD4 T cells were significantly lower in the CD group relative to those with SLD (4243 versus 250 cells/10 cells; P = 0.015).

CONCLUSIONS

CD is associated with a reduction of CD11c cells, CD4 TN, and interferon-γ-producing EBV-specific CD4 T cells, suggesting an interplay between innate and adaptive immune compartments may be important for regulating EBV DNAemia.

T-Cell Dysfunction as a Limitation of Adoptive Immunotherapy: Current Concepts and Mitigation Strategies

Simple Summary

T cells are immune cells that can be used to target infections or cancers. Adoptive T-cell immunotherapy leverages these properties and/or confers new features to T cells through ex vivo manipulations prior to their use in patients. However, as a “living drug,” the function of these cells can be hampered by several built-in physiological constraints and external factors that limit their efficacy. Manipulating T cells ex vivo can impart dysfunctional features to T cells through repeated stimulations and expansion, but it also offers many opportunities to improve the therapeutic potential of these cells, including emerging interventions to prevent or reverse T-cell dysfunction developing ex vivo or after transfer in patients. This review outlines the various forms of T-cell dysfunction, emphasizes how it affects various types of T-cell immunotherapy approaches, and describes current and anticipated strategies to limit T-cell dysfunction.

Abstract

Over the last decades, cellular immunotherapy has revealed its curative potential. However, inherent physiological characteristics of immune cells can limit the potency of this approach. Best defined in T cells, dysfunction associated with terminal differentiation, exhaustion, senescence, and activation-induced cell death, undermine adoptive cell therapies. In this review, we concentrate on how the multiple mechanisms that articulate the various forms of immune dysfunction impact cellular therapies primarily involving conventional T cells, but also other lymphoid subtypes. The repercussions of immune cell dysfunction across the full life cycle of cell therapy, from the source material, during manufacturing, and after adoptive transfer, are discussed, with an emphasis on strategies used during ex vivo manipulations to limit T-cell dysfunction. Applicable to cellular products prepared from native and unmodified immune cells, as well as genetically engineered therapeutics, the understanding and potential modulation of dysfunctional features are key to the development of improved cellular immunotherapies.

Modeling, optimization, and comparable efficacy of T cell and hematopoietic stem cell gene editing for treating hyper-IgM syndrome

Precise correction of the CD40LG gene in T cells and hematopoietic stem/progenitor cells (HSPC) holds promise for treating X‐linked hyper‐IgM Syndrome (HIGM1), but its actual therapeutic potential remains elusive. Here, we developed a one‐size‐fits‐all editing strategy for effective T‐cell correction, selection, and depletion and investigated the therapeutic potential of T‐cell and HSPC therapies in the HIGM1 mouse model. Edited patients’ derived CD4 T cells restored physiologically regulated CD40L expression and contact‐dependent B‐cell helper function. Adoptive transfer of wild‐type T cells into conditioned HIGM1 mice rescued antigen‐specific IgG responses and protected mice from a disease‐relevant pathogen. We then obtained ~ 25% CD40LG editing in long‐term repopulating human HSPC. Transplanting such proportion of wild‐type HSPC in HIGM1 mice rescued immune functions similarly to T‐cell therapy. Overall, our findings suggest that autologous edited T cells can provide immediate and substantial benefits to HIGM1 patients and position T‐cell ahead of HSPC gene therapy because of easier translation, lower safety concerns and potentially comparable clinical benefits.

Failure of Viral-Specific T Cells Administered in Pre-transplant Settings in Children with Inborn Errors of Immunity

PURPOSE

Use of adoptive immunotherapy with virus-specific T cells (VST) in patients with inborn errors of immunity prior to hematopoietic stem cell transplantation (HSCT) has been reported in few patients. We report our experience, reviewing all the cases previously reported.

METHODS

We report four children with inborn errors of immunity who received VST infusion in a pre-HSCT setting in two reference centers in Spain and review all inborn errors of immunity cases previously reported.

RESULTS

Taking into account our four cases, nine children have been reported to receive VST prior to HSCT to date: 3 severe combined immunodeficiency, 2 CTPS1 deficiency, 1 dyskeratosis congenital, 1 ORAI1 deficiency, 1 Rothmund-Thomson syndrome, and 1 combined immunodeficiency without confirmed genetic defect. In four patients, immunotherapy resulted in clinical improvement, allowing to proceed to HSCT. In these cases, the infusion was started closely to viral diagnosis [mean time 28 days (IQR; 17-52 days)], and the VST was followed shortly thereafter by HSCT [mean time 28 days (IQR; 10-99 days)]. Viremia was controlled after HSCT in two cases (performed 7 and 36 days after the infusion). Multiple infusions were required in many cases. Five out of nine patients died before receiving HSCT. These patients presented with a prolonged and uncontrolled infection before VST administration [mean time from viral diagnosis to VST infusion was 176 days (IQR; 54-1687)].

CONCLUSIONS

In patients with inborn errors of immunity, the efficacy of VST for treating disseminated viral infections in pre-transplant settings seems to have a limited efficacy. However, this therapy could be used in a pre-emptive setting before severe viral disease occurs or closely to HSCT.