Restoration of viral immunity in immunodeficient humans by the adoptive transfer of T cell clones

Glioblastoma-mediated Immune Dysfunction Limits CMV-specific T Cells and Therapeutic Responses: Results from a Phase I/II Trial

PURPOSE

Cytomegalovirus (CMV) antigens occur in glioblastoma but not in normal brains, making them desirable immunologic targets.

PATIENTS AND METHODS

Highly functional autologous polyclonal CMV pp65-specific T cells from patients with glioblastoma were numerically expanded under good manufacturing practice compliant conditions and administered after 3 weeks of lymphodepleting dose-dense temozolomide (100 mg/m²) treatment. The phase I component used a 3+3 design, ascending through four dose levels (5 × 10⁶-1 × 10⁸ cells). Treatment occurred every 6 weeks for four cycles. In vivo persistence and effector function of CMV-specific T cells was determined by dextramer staining and multiparameter flow cytometry in serially sampled peripheral blood and in the tumor microenvironment.

RESULTS

We screened 65 patients; 41 were seropositive for CMV; 25 underwent leukapheresis; and 20 completed ≥1 cycle. No dose-limiting toxicities were observed. Radiographic response was complete in 1 patient, partial in 2. Median progression-free survival (PFS) time was 1.3 months [95% confidence interval (CI), 0-8.3 months]; 6-month PFS was 19% (95% CI, 7%-52%); and median overall survival time was 12 months (95% CI, 6 months to not reached). Repeated infusions of CMV-T cells paralleled significant increases in circulating CMV⁺ CD8⁺ T cells, but cytokine production showing effector activity was suppressed, especially from T cells obtained directly from glioblastomas.

CONCLUSIONS

Adoptive infusion of CMV-specific T cells after lymphodepletion with dose-dense temozolomide was well tolerated. But apparently CMV seropositivity does not guarantee tumor susceptibility to CMV-specific T cells, suggesting heterogeneity in CMV antigen expression. Moreover, effector function of these T cells was attenuated, indicating a requirement for further T-cell modulation to prevent their dysfunction before conducting large-scale clinical studies.

Insufficient Antigen Presentation Due to Viral Immune Evasion Explains Lethal Cytomegalovirus Organ Disease After Allogeneic Hematopoietic Cell Transplantation

Reactivation of latent cytomegalovirus (CMV) poses a clinical problem in transiently immunocompromised recipients of hematopoietic cell (HC) transplantation (HCT) by viral histopathology that results in multiple organ manifestations. Compared to autologous HCT and to syngeneic HCT performed with identical twins as HC donor and recipient, lethal outcome of CMV infection is more frequent in allogeneic HCT with MHC/HLA or minor histocompatibility loci mismatch between donor and recipient. It is an open question if a graft-vs.-host (GvH) reaction exacerbates CMV disease, or if CMV exacerbates GvH disease (GvHD), or if interference is mutual. Here we have used a mouse model of experimental HCT and murine CMV (mCMV) infection with an MHC class-I mismatch by gene deletion, so that either HCT donor or recipient lack a single MHC class-I molecule, specifically H-2 Ld. This particular immunogenetic disparity has the additional advantage that it allows to experimentally separate GvH reaction of donor-derived T cells against recipient's tissues from host-vs.-graft (HvG) reaction of residual recipient-derived T cells against the transplanted HC and their progeny. While in HvG-HCT with Ld-plus donors and Ld-minus recipients almost all infected recipients were found to control the infection and survived, almost all infected recipients died of uncontrolled virus replication and consequent multiple-organ viral histopathology in case of GvH-HCT with Ld-minus donors and Ld-plus recipients. Unexpectedly, although anti-Ld-reactive CD8+ T cells were detected, mortality was not found to be associated with GvHD histopathology. By comparing HvG-HCT and GvH-HCT, investigation into the mechanism revealed an inefficient reconstitution of antiviral high-avidity CD8+ T cells, associated with lack of formation of protective nodular inflammatory foci (NIF) in host tissue, selectively in GvH-HCT. Most notably, mice infected with an immune evasion gene deletion mutant of mCMV survived under otherwise identical GvH-HCT conditions. Survival was associated with enhanced antigen presentation and formation of protective NIF by antiviral CD8+ T cells that control the infection and prevent viral histopathology. This is an impressive example of lethal viral disease in HCT recipients based on a failure of the immune control of CMV infection due to viral immune evasion in concert with an MHC class-I mismatch.

Moving Past Ganciclovir and Foscarnet: Advances in CMV Therapy

PURPOSE OF REVIEW

CMV DNA polymerase inhibitors such as ganciclovir and foscarnet have dramatically reduced the burden of CMV infection in the HCT recipient. However, their use is often limited by toxicities and resistance. Agents with novel mechanisms and favorable toxicity profiles are critically needed. We review recent developments in CMV antivirals and immune-based approaches to mitigating CMV infection.

RECENT FINDINGS

Letermovir, an inhibitor of the CMV terminase complex, was approved in 2017 for primary CMV prophylaxis in adult seropositive allogeneic HCT recipients. Maribavir, an inhibitor of the CMV UL97 kinase, is currently in two phase 3 treatment studies. Adoptive immunotherapy using third-party T cells has proven safe and effective in preliminary studies. Vaccine development continues, with several promising candidates currently under study. No longer limited to DNA polymerase inhibitors, the prevention and treatment of CMV infections in the HCT recipient is a rapidly evolving field which should translate into improvements in CMV-related outcomes.

The future of cellular immunotherapy for childhood leukemia

PURPOSE OF REVIEW

Exciting translational discoveries in recent years have brought realized promise of immunotherapy for children with high-risk leukemias. This review summarizes the current immunotherapeutic landscape with a focus on key clinical trials for patients with acute lymphoblastic leukemia or acute myeloid leukemia.

RECENT FINDINGS

Chemotherapy resistance remains a major barrier to cure in children with high-risk leukemias. Immunotherapy approaches have potential to overcome this resistance given alternative mechanisms of action. Based upon preclinical activity and/or success in adult patients, recent clinical trials have demonstrated safety and efficacy of various mAb, antibody-drug conjugate, bispecific T-cell-engaging antibody, natural killer cell, and chimeric antigen receptor-redirected T-cell immunotherapies for children with acute lymphoblastic leukemia or acute myeloid leukemia. Food and Drug Administration approval of several of these immunotherapies has increased the pediatric leukemia therapeutic portfolio and improved clinical outcomes for previously incurable patients.

SUMMARY

Several antibody-based or cellular immunotherapy modalities have demonstrated appreciable efficacy in children with relapsed or chemotherapy-refractory leukemia via early-phase clinical trials. Some studies have also identified critical biomarkers of treatment response and resistance that merit further investigation. Continued preclinical and clinical evaluation of novel immunotherapies is imperative to improve cure rates for children with high-risk leukemias.

Umbilical Cord Blood Transplants: Current Status and Evolving Therapies

Hematopoietic cell transplants using stem cells from umbilical cord blood are used worldwide for the treatment of malignant and non-malignant disorders. Transplant procedures from this stem cell source have shown promising outcomes in successfully treating various hematologic, immunologic, malignant, and inherited metabolic disorders. Rapid availability of these stem cells is an important advantage over other unrelated donor transplants, especially in situations where waiting can adversely affect the prognosis. The umbilical cord blood is rich in CD34+ stem cells, though with a limited cell dose and usually takes longer to engraft. Limitations around this have been addressed by in vivo and ex vivo expansion techniques as well as enhanced engraftment kinetics. Development of adoptive immunotherapy using other components of umbilical cord blood such as regulatory T cells, virus-specific T cells, and natural killer cells has further transformed the field and enhanced the utility of umbilical cord blood unit.

CMV Prevention and Treatment in Transplantation: What's New in 2019

PURPOSE OF REVIEW

Transplant recipients are at risk for cytomegalovirus (CMV) infection and associated morbidity and mortality. We summarize recently introduced or currently investigated modalities for prevention and treatment of CMV infection in hematopoietic cell (HCT) and solid organ transplant (SOT) recipients.

RECENT FINDINGS

Letermovir was recently approved for CMV prevention in HCT recipients. Data from real world studies support its role to improve outcomes in this population. Letermovir is currently under investigation for broader patient populations and indications. Maribavir is in late stages of development for CMV treatment and may provide a safer alternative to currently available anti-CMV drugs. Promising CMV vaccine candidates and adoptive cell therapy approaches are under evaluation. CMV immune monitoring assays are predicted to play a more central role in our clinical decision making. In recent years, major advances have been made in CMV prevention and treatment in transplant recipients. Rigorous research is ongoing and is anticipated to further impact our ability to improve outcomes in this population.

Single-Cell Transcriptome Analysis Reveals Gene Signatures Associated with T-cell Persistence Following Adoptive Cell Therapy

Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) can mediate responses in some patients with metastatic epithelial cancer. Identifying gene signatures associated with successful ACT might enable the development of improved therapeutic approaches. The persistence of transferred T cells in the peripheral blood is one indication of clinical effectiveness, but many T-cell and host factors may influence T-cell persistence. To limit these variables, we previously studied a patient with metastatic colorectal cancer treated with polyclonal TILs targeting the KRAS(G12D) hotspot mutation, who experienced a partial response for 9 months. Three dominant clonotypes specifically recognizing KRAS(G12D) epitopes were identified, but we found that only two clonotypes persisted 40 days after ACT. Because of these findings, in this study, we performed the single-cell transcriptome analysis of the infused TILs. The analysis revealed a total of 472 genes that were differentially expressed between clonotypes 9.1-NP and 9.2-P single cells, and 528 genes between 9.1-NP and 10-P. Following these clonotypes in the peripheral blood after ACT, the gene expression patterns changed, but IL7R, ITGB1, KLF2, and ZNF683 remained expressed in the persistent 9.2-P and 10-P cells, compared with the nonpersistent 9.1-NP cells. In addition, four autologous TILs, which were used for treatment but persisted poorly 1 month after ACT, did not express the gene profiles associated with persistence. These results suggest that certain TIL populations possess a unique gene expression profile that can lead to the persistence of T cells. Thus, this single-patient study provides insight into how to improve ACT for solid cancer.

T cell engineering for adoptive T cell therapy: safety and receptor avidity

Since the first bone marrow transplantation, adoptive T cell therapy (ACT) has developed over the last 80 years to a highly efficient and specific therapy for infections and cancer. Genetic engineering of T cells with antigen-specific receptors now provides the possibility of generating highly defined and efficacious T cell products. The high sensitivity of engineered T cells towards their targets, however, also bears the risk of severe off-target toxicities. Therefore, different safety strategies for engineered T cells have been developed that enable removal of the transferred cells in case of adverse events, control of T cell activity or improvement of target selectivity. Receptor avidity is a crucial component in the balance between safety and efficacy of T cell products. In clinical trials, T cells equipped with high avidity T cell receptor (TCR)/chimeric antigen receptor (CAR) have been mostly used so far because of their faster and better response to antigen recognition. However, over-activation can trigger T cell exhaustion/death as well as side effects due to excessive cytokine production. Low avidity T cells, on the other hand, are less susceptible to over-activation and could possess better selectivity in case of tumor antigens shared with healthy tissues, but complete tumor eradication may not be guaranteed. In this review we describe how 'optimal' TCR/CAR affinity can increase the safety/efficacy balance of engineered T cells, and discuss simultaneous or sequential infusion of high and low avidity receptors as further options for efficacious but safe T cell therapy.

Advances in the treatment of cytomegalovirus

BACKGROUND

Human cytomegalovirus (HCMV) is a threat to immunologically weak patients. HCMV cannot yet be eliminated with a vaccine, despite recent advances.

SOURCES OF DATA

Sources of data are recently published research papers and reviews about HCMV treatments.

AREAS OF AGREEMENT

Current antivirals target the UL54 DNA polymerase and are limited by nephrotoxicity and viral resistance. Promisingly, letermovir targets the HCMV terminase complex and has been recently approved by the FDA and EMA.

AREAS OF CONTROVERSY

Should we screen newborns for HCMV, and use antivirals to treat sensorineural hearing loss after congenital HCMV infection?

GROWING POINTS

Growing points are developing drugs against latently infected cells. In addition to small molecule inhibitors, a chemokine-based fusion toxin protein, F49A-FTP, has shown promise in killing both lytically and latently infected cells.

AREAS TIMELY FOR DEVELOPING RESEARCH

We need to understand what immune responses are required to control HCMV, and how best to raise these immune responses with a vaccine.

An update on the treatment of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Introduction: Human Cytomegalovirus (CMV) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Standard treatment options have for long been limited to a small number of effective drugs with significant toxicities.Areas covered: In this manuscript, the authors update a previous review summarizing recent developments in the virology lab and their possible implications for treatment strategies at bedside. In particular, the authors focused on new antiviral drugs already available and under investigation in clinical trials and innovative immunotherapeutic approaches, including adoptive T-cell therapy and vaccines.Expert opinion: Broader knowledge of CMV biology and its relationship with the host immune system is greatly contributing to the development of novel therapeutic approaches. The availability of new drugs, the improved techniques for virological testing and the more accurate patient risk stratification allow to better individualize treatment, limiting toxicity while sparing antiviral effects. The role of immunotherapy is clearly emerging and will further expand our treatment armamentarium.

Role of antibodies in confining cytomegalovirus after reactivation from latency: three decades' résumé

Cytomegaloviruses (CMVs) are highly prevalent herpesviruses, characterized by strict species specificity and the ability to establish non-productive latent infection from which reactivation can occur. Reactivation of latent human CMV (HCMV) represents one of the most important clinical challenges in transplant recipients secondary to the strong immunosuppression. In addition, HCMV is the major viral cause of congenital infection with severe sequelae including brain damage. The accumulated evidence clearly shows that cellular immunity plays a major role in the control of primary CMV infection as well as establishment and maintenance of latency. However, the efficiency of antiviral antibodies in virus control, particularly in prevention of congenital infection and virus reactivation from latency in immunosuppressed hosts, is much less understood. Because of a strict species specificity of HCMV, the role of antibodies in controlling CMV disease has been addressed using murine CMV (MCMV) as a model. Here, we review and discuss the role played by the antiviral antibody response during CMV infections with emphasis on latency and reactivation not only in the MCMV model, but also in relevant clinical settings. We provide evidence to conclude that antiviral antibodies do not prevent the initiating molecular event of virus reactivation from latency but operate by preventing intra-organ spread and inter-organ dissemination of recurrent virus.

Battle between Host Immune Cellular Responses and HCMV Immune Evasion

Human cytomegalovirus (HCMV) is ubiquitously prevalent. HCMV infection is typically asymptomatic and controlled by the immune system in healthy individuals, yet HCMV can be severely pathogenic for the fetus during pregnancy and in immunocompromised persons, such as transplant recipients or HIV infected patients. HCMV has co-evolved with the hosts, developed strategies to hide from immune effector cells and to successfully survive in the human organism. One strategy for evading or delaying the immune response is maintenance of the viral genome to establish the phase of latency. Furthermore, HCMV immune evasion involves the downregulation of human leukocyte antigens (HLA)-Ia molecules to hide infected cells from T-cell recognition. HCMV expresses several proteins that are described for downregulation of the HLA class I pathway via various mechanisms. Here, we review the wide range of immune evasion mechanisms of HCMV. Understanding the mechanisms of HCMV immune evasion will contribute to the development of new customized therapeutic strategies against the virus.

Conservation of molecular and cellular phenotypes of invariant NKT cells between humans and non-human primates

Invariant NKT (iNKT) cells in both humans and non-human primates are activated by the glycolipid antigen, α-galactosylceramide (α-GalCer). However, the extent to which the molecular mechanisms of antigen recognition and in vivo phenotypes of iNKT cells are conserved among primate species has not been determined. Using an evolutionary genetic approach, we found a lack of diversifying selection in CD1 genes over 45 million years of evolution, which stands in stark contrast to the history of the MHC system for presenting peptide antigens to T cells. The invariant T cell receptor (TCR)-α chain was strictly conserved across all seven primate clades. Invariant NKT cells from rhesus macaques (Macaca mulatta) bind human CD1D-α-GalCer tetramer and are activated by α-GalCer-loaded human CD1D transfectants. The dominant TCR-β chain cloned from a rhesus-derived iNKT cell line is nearly identical to that found in the human iNKT TCR, and transduction of the rhesus iNKT TCR into human Jurkat cells show that it is sufficient for binding human CD1D-α-GalCer tetramer. Finally, we used a 20-color flow cytometry panel to probe tissue phenotypes of iNKT cells in a cohort of rhesus macaques. We discovered several tissue-resident iNKT populations that have not been previously described in non-human primates but are known in humans, such as TCR-γδ iNKTs. These data reveal a diversity of iNKT cell phenotypes despite convergent evolution of the genes required for lipid antigen presentation and recognition in humans and non-human primates.

T cell receptor gene therapy targeting WT1 prevents acute myeloid leukemia relapse post-transplant

Relapse after allogeneic hematopoietic cell transplantation (HCT) is the leading cause of death in patients with acute myeloid leukemia (AML) entering HCT with poor-risk features^1-3. When HCT does produce prolonged relapse-free survival, it commonly reflects graft-versus-leukemia effects mediated by donor T cells reactive with antigens on leukemic cells⁴. As graft T cells have not been selected for leukemia specificity and frequently recognize proteins expressed by many normal host tissues, graft-versus-leukemia effects are often accompanied by morbidity and mortality from graft-versus-host disease⁵. Thus, AML relapse risk might be more effectively reduced with T cells expressing receptors (TCRs) that target selected AML antigens⁶. We therefore isolated a high-affinity Wilms' Tumor Antigen 1-specific TCR (TCR_C4) from HLA-A2⁺ normal donor repertoires, inserted TCR_C4 into Epstein-Bar virus-specific donor CD8⁺ T cells (T_TCR-C4) to minimize graft-versus-host disease risk and enhance transferred T cell survival^7,8, and infused these cells prophylactically post-HCT into 12 patients ( NCT01640301 ). Relapse-free survival was 100% at a median of 44 months following infusion, while a concurrent comparative group of 88 patients with similar risk AML had 54% relapse-free survival (P = 0.002). T_TCR-C4 maintained TCR_C4 expression, persisted long-term and were polyfunctional. This strategy appears promising for preventing AML recurrence in individuals at increased risk of post-HCT relapse.

A novel simplified method of generating cytomegalovirus-specific cytokine-induced killer cells of high specificity and superior potency with GMP compliance

We describe a method of rendering polyclonal cytokine-induced killer cells (CIK) specific against cytomegalovirus (CMV), focusing on GMP compliance. Peripheral blood mononuclear cells (PBMNC) are stimulated with pooled CMV peptides pp65 and IE-1 for 16-24 h and the reactive T cell subset which up-regulate CD137 is further co-stimulated with anti-CD137, followed by expansion in G-Rex flasks under standard CIK culture condition. This method generates a large number CMV-specific CIK with superior potency compared to published method currently in clinical trials. The cytotoxicity as measured by chromium release assay correlates with the upregulation of CD107a upon peptide re-challenge as measured by flow cytometry. CMV-CIK at maturity consist of mainly late effector memory CD8 T cells and have a skewed TCR repertoire with preferential expansion of a few families. Such CMV-CIK retain their function after freezing and thawing. CMV-CIK thus generated is ready for clinical trial against drug-resistant CMV disease.

Infusion of cytotoxic T lymphocytes for the treatment of viral infections in hematopoetic stem cell transplant patients

PURPOSE OF REVIEW

Allogeneic hematopoietic stem cell transplantation has proven curative for a range of malignant and nonmalignant disorders. However, the clinical success of this therapy is marred by the morbidity associated with viral infections, which are frequent (cytomegalovirus 15.6-28%, adenovirus 3-21%, BK virus 18.5-20.7%) post-transplant. These infections occur as a consequence of transplant conditioning regimens designed to eliminate not only malignant cells but also host immune cells that might interfere with stem cell engraftment. The result is a transient period of immune compromise when hematopoietic stem cell transplant recipients are at risk of infectious complications associated with both latent (cytomegalovirus, Epstein-Barr virus, BK virus, human herpes virus 6, herpes simplex virus, varicella-zoster virus) and community-acquired viruses including adenovirus, respiratory syncytial virus, and parainfluenza virus.

RECENT FINDINGS

Current standard of care for many of these infections involves pharmacologic agents, which are often ineffective and associated with side effects including nephrotoxicity and hepatotoxicity. Ultimately, because these agents do not address the underlying immune compromise, viral rebound often occurs. Thus, a number of groups have explored the clinical potential of adoptively transferred virus-specific T cells (VSTs) as an approach to prevent/treat virus-associated complications.

SUMMARY

The current review will highlight recent publications showcasing VST manufacturing technologies and clinical experience with such cells.

At the Intersection of Biomaterials and Gene Therapy: Progress in Non-viral Delivery of Nucleic Acids

Biomaterials play a critical role in technologies intended to deliver therapeutic agents in clinical settings. Recent explosion of our understanding of how cells utilize nucleic acids has garnered excitement to develop a range of older (e.g., antisense oligonucleotides, plasmid DNA and transposons) and emerging (e.g., short interfering RNA, messenger RNA and non-coding RNAs) nucleic acid agents for therapy of a wide range of diseases. This review will summarize biomaterials-centered advances to undertake effective utilization of nucleic acids for therapeutic purposes. We first review various types of nucleic acids and their unique abilities to deliver a range of clinical outcomes. Using recent advances in T-cell based therapy as a case in point, we summarize various possibilities for utilizing biomaterials to make an impact in this exciting therapeutic intervention technology, with the belief that this modality will serve as a therapeutic paradigm for other types of cellular therapies in the near future. We subsequently focus on contributions of biomaterials in emerging nucleic acid technologies, specifically focusing on the design of intelligent nanoparticles, deployment of mRNA as an alternative to plasmid DNA, long-acting (integrating) expression systems, and in vitro/in vivo expansion of engineered T-cells. We articulate the role of biomaterials in these emerging nucleic acid technologies in order to enhance the clinical impact of nucleic acids in the near future.

Cytomegalovirus Infections after Hematopoietic Stem Cell Transplantation: Current Status and Future Immunotherapy

Cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT) is one of the critical infectious complications related to host immune recovery. The spectrum of CMV infection is quite extensive, from asymptomatic CMV reactivation presenting mainly as CMV DNAemia to fatal CMV diseases involving gut, liver, lungs, or brain. In addition to organ involvement, CMV reactivation can exert indirect effects such as immunosuppression or graft failure that may result in the development of concurrent infectious complications. Currently, preemptive therapy, which is based on PCR-based monitoring of CMV from blood, is a mainstay enabling improvement in CMV-related outcomes. During the past decades, new antiviral drugs, clinical trials for prophylaxis in high-risk groups, and vaccines for preventing CMV infection have been introduced. In addition, data for immunologic monitoring and adoptive immunotherapy have also been accumulated. Here, we review the current status and recent updates in this field, with future perspectives including immunotherapy in HSCT recipients.

Guidelines for the management of cytomegalovirus infection in patients with haematological malignancies and after stem cell transplantation from the 2017 European Conference on Infections in Leukaemia (ECIL 7)

Cytomegalovirus is one of the most important infections to occur after allogeneic haematopoietic stem cell transplantation (HSCT), and an increasing number of reports indicate that cytomegalovirus is also a potentially important pathogen in patients treated with recently introduced drugs for hematological malignancies. Expert recommendations have been produced by the 2017 European Conference on Infections in Leukaemia (ECIL 7) after a review of the literature on the diagnosis and management of cytomegalovirus in patients after HSCT and in patients receiving other types of therapy for haematological malignancies. These recommendations cover diagnosis, preventive strategies such as prophylaxis and pre-emptive therapy, and management of cytomegalovirus disease. Antiviral drugs including maribavir and letermovir are in development and prospective clinical trials have recently been completed. However, management of patients with resistant or refractory cytomegalovirus infection or cytomegalovirus disease is a challenge. In this Review we summarise the reviewed literature and the recommendations of the ECIL 7 for management of cytomegalovirus in patients with haematological malignancies.

Adoptive immunotherapy with antiviral T cells: Methods and results

Viral infections and reactivations are one of the main causes of morbidity and mortality in patients who undergo allogeneic haematopoietic progenitor cell transplantation. Adoptive immunotherapy with virus-specific Tcells (from donor to patient) has shown efficacy in the antiviral treatment of patients who have undergone transplantation and whose immune system has not yet been reconstituted. Currently, and according to the requirements of the corresponding agencies that regulate the production of these advanced personalised therapies, the production and application of these cell products are being optimised in such a way that they comply with good manufacturing practice standards and are safe and effective for treating patients. To facilitate their implementation, we need to understand the foundations of producing and using virus-specific Tcells. This study reviews the evolution of the methodology for producing antiviral Tcells and the studies that support their therapeutic efficacy. The study covers up to the current production platforms, whose commercialisation has begun in Spain. These platforms will help obtain virus-specific Tcells and chimeric antigen receptor Tcells, among others, in a completely automated manner and under good manufacturing practice conditions. The implementation of these new methodologies in the Spanish healthcare system will undoubtedly facilitate patients' access to a new repertoire of advanced therapies.

Human Cytomegalovirus Latency and Reactivation in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Human cytomegalovirus (HCMV) reactivation is a major infectious cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). HCMV is a ubiquitous beta-herpesvirus which asymptomatically infects immunocompetent individuals but establishes lifelong latency, with the potential to reactivate to a life-threatening productive infection when the host immune system is suppressed or compromised. Opportunistic HCMV reactivation is the most common viral complication following engraftment after HSCT and is associated with a marked increase in non-relapse mortality, which appears to be linked to complex effects on post-transplant immune recovery. This minireview explores the cellular sites of HCMV latency and reactivation in HSCT recipients and provides an overview of the risk factors for HCMV reactivation post-HSCT. The impact of HCMV in shaping post-transplant immune reconstitution and its relationship with patient outcomes such as relapse and graft-versus-host disease will be discussed. Finally, we survey current and emerging strategies to prevent and control HCMV reactivation in HSCT recipients, with recent developments including adoptive T cell therapies to accelerate HCMV-specific T cell reconstitution and new anti-HCMV drug therapy for HCMV reactivation after HSCT.

Comprehensive Characterization of a Next-Generation Antiviral T-Cell Product and Feasibility for Application in Immunosuppressed Transplant Patients

Viral infections have a major impact on morbidity and mortality of immunosuppressed solid organ transplant (SOT) patients because of missing or failure of adequate pharmacologic antiviral treatment. Adoptive antiviral T-cell therapy (AVTT), regenerating disturbed endogenous T-cell immunity, emerged as an attractive alternative approach to combat severe viral complications in immunocompromised patients. AVTT is successful in patients after hematopoietic stem cell transplantation where T-cell products (TCPs) are manufactured from healthy donors. In contrast, in the SOT setting TCPs are derived from/applied back to immunosuppressed patients. We and others demonstrated feasibility of TCP generation from SOT patients and first clinical proof-of-concept trials revealing promising data. However, the initial efficacy is frequently lost long-term, because of limited survival of transferred short-lived T-cells indicating a need for next-generation TCPs. Our recent data suggest that Rapamycin treatment during TCP manufacture, conferring partial inhibition of mTOR, might improve its composition. The aim of this study was to confirm these promising observations in a setting closer to clinical challenges and to deeply characterize the next-generation TCPs. Using cytomegalovirus (CMV) as model, our next-generation Rapamycin-treated (Rapa-)TCP showed consistently increased proportions of CD4⁺ T-cells as well as CD4⁺ and CD8⁺ central-memory T-cells (T_CM). In addition, Rapamycin sustained T-cell function despite withdrawal of Rapamycin, showed superior T-cell viability and resistance to apoptosis, stable metabolism upon activation, preferential expansion of T_CM, partial conversion of other memory T-cell subsets to T_CM and increased clonal diversity. On transcriptome level, we observed a gene expression profile denoting long-lived early memory T-cells with potent effector functions. Furthermore, we successfully applied the novel protocol for the generation of Rapa-TCPs to 19/19 SOT patients in a comparative study, irrespective of their history of CMV reactivation. Moreover, comparison of paired TCPs generated before/after transplantation did not reveal inferiority of the latter despite exposition to maintenance immunosuppression post-SOT. Our data imply that the Rapa-TCPs, exhibiting longevity and sustained T-cell memory, are a reasonable treatment option for SOT patients. Based on our success to manufacture Rapa-TCPs from SOT patients under maintenance immunosuppression, now, we seek ultimate clinical proof of efficacy in a clinical study.

CTL-mediated immunotherapy can suppress SHIV rebound in ART-free macaques

A major barrier to human immunodeficiency virus (HIV) cure is the existence of viral reservoirs that lead to viral rebound following discontinuation of antiretroviral therapy (ART). We postulate that enhancing cytotoxic T lymphocytes (CTL) targeting conserved envelope (Env) regions can eliminate HIV infected cells in latency. Here, we evaluate the use of adoptively transferred HIV vaccine-induced subtype C Env-specific CTLs in a macaque subtype B simian-human immunodeficiency virus (SHIV) model to determine whether plasma viremia can be controlled after ART interruption. We demonstrate that adoptive cellular therapy (ACT) using autologous Env-specific T cells augmented by therapeutic vaccination can suppress ART-free viral rebound in the SHIV model. Furthermore, phenotypic and functional characterization of adoptively transferred cells in ACT-responsive and nonresponsive animals support a critical role for cross-reactive central memory T cells in viremia control. Our study offers an approach to potentiate immunological suppression of HIV in the absence of antiviral drugs.

Viral rebound following discontinuation of antiretroviral therapy (ART) is a major obstacle for HIV cure. Here, the authors show that adoptive cellular therapy using autologous Env-specific T cells augmented by therapeutic vaccination can control viral rebound after ART interruption in a SHIV macaque model.

Releasing the concept of HLA-allele specific peptide anchors in viral infections: A non-canonical naturally presented human cytomegalovirus-derived HLA-A*24:02 restricted peptide drives exquisite immunogenicity

T‐cell receptors possess the unique ability to survey and respond to their permanently modified ligands, self HLA‐I molecules bound to non‐self peptides of various origin. This highly specific immune function is impaired following hematopoietic stem cell transplantation (HSCT) for a timespan of several months needed for the maturation of T‐cells. Especially, the progression of HCMV disease in immunocompromised patients induces life‐threatening situations. Therefore, the need for a new immune system that delivers vital and potent CD8+ T‐cells carrying TCRs that recognize even one human cytomegalovirus (HCMV) peptide/HLA molecule and clear the viral infection long term becomes obvious. The transcription and translation of HCMV proteins in the lytic cycle is a precisely regulated cascade of processes, therefore, it is a highly sensitive challenge to adjust the exact time point of HCMV‐peptide recruitment over self‐peptides. We utilized soluble HLA technology in HCMV‐infected fibroblasts and sequenced naturally sHLA‐A*24:02 presented HCMV‐derived peptides. One peptide of 14 AAs length derived from the IE2 antigen induced the strongest T‐cell responses; this peptide can be detected with a low ranking score in general peptide prediction databanks. These results highlight the need for elaborate and HLA‐allele specific peptide selection.

Opportunities to Target the Life Cycle of Epstein-Barr Virus (EBV) in EBV-Associated Lymphoproliferative Disorders

Many lymphoproliferative disorders (LPDs) are considered "EBV associated" based on detection of the virus in tumor tissue. EBV drives proliferation of LPDs via expression of the viral latent genes and many pre-clinical and clinical studies have shown EBV-associated LPDs can be treated by exploiting the viral life cycle. After a brief review of EBV virology and the natural life cycle within a host we will discuss the importance of the viral gene programs expressed during specific viral phases, as well as within immunocompetent vs. immunocompromised hosts and corresponding EBV-associated LPDs. We will then review established and emerging treatment approaches for EBV-associated LPDs based on EBV gene expression programs. Patients with EBV-associated LPDs can have a poor performance status, multiple comorbidities, and/or are immunocompromised from organ transplantation, autoimmune disease, or other congenital or acquired immunodeficiency making them poor candidates to receive intensive cytotoxic chemotherapy. With the emergence of EBV-directed therapy there is hope that we can devise more effective therapies that confer milder toxicity.

TCR repertoire evolution during maintenance of CMV-specific T-cell populations

During infections and cancer, the composition of the T-cell receptor (TCR) repertoire of antigen-specific CD8⁺ T cells changes over time. TCR avidity is thought to be a major driver of this process, thereby interacting with several additional regulators of T-cell responses to form a composite immune response architecture. Infections with latent viruses, such as cytomegalovirus (CMV), can lead to large T-cell responses characterized by an oligoclonal TCR repertoire. Here, we review the current status of experimental studies and theoretical models of TCR repertoire evolution during CMV infection. We will particularly discuss the degree to which this process may be determined through structural TCR avidity. As engineered TCR-redirected T cells have moved into the spotlight for providing more effective immunotherapies, it is essential to understand how the key features of a given TCR influence T-cell expansion and maintenance in settings of infection or malignancy. Deeper insights into these mechanisms will improve our basic understanding of T-cell immunology and help to identify optimal TCRs for immunotherapy.

Strategies of adoptive T -cell transfer to treat refractory viral infections post allogeneic stem cell transplantation

Background

Allogeneic hematopoietic stem cell transplantation (HSCT) can expose patients to a transient but marked immunosuppression, during which viral infections are an important cause of morbidity and mortality. Adoptive transfer of virus-specific T cells is an attractive approach to restore protective T -cell immunity in patients with refractory viral infections after allogeneic HSCT.

Objectives

This narrative review summarizes clinical evidence and developments of almost 30 years of adoptive T -cell transfer. The review is based on evidence extracted from PubMed searches and the clinical and experimental work of the authors.

Content

Viral infections after HSCT are frequently caused by the endogenous reactivation of persistent pathogens such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus (AdV). Current antiviral medication is not satisfactory and does not treat the underlying pathophysiology which is the lack of specific T -cell immunity. Adoptive transfer of virus-specific T cells could be a potentially curative, pathogen-specific, and non-toxic treatment providing long-term immunity against the virus. The isolation of virus-specific T cells from a healthy donor and infusion into a recipient is known as adoptive T -cell transfer and has been performed in many patients using different treatment protocols. Based on basic research, new isolation protocols aim at a safe and fast availability of cellular products for adoptive T -cell transfer. We summarize preclinical and clinical data on each of the main pathogens and on the technical approaches currently available to target either single antigens or even multiple pathogens.

Conclusion

Cellular therapy is considered as one of the major recent breakthroughs in medicine. Translation of this individualized treatment into first-line clinical routine is still limited. Main hurdles are availability of the technique, limited compatibility of classical phase III designs with cellular therapy, and regulatory restrictions. Multinational efforts are required to clarify the status of cellular treatment in first-line clinical routine with the overall objective to strengthen evidence-based treatment guidelines for the treatment of refractory viral infections post HSCT.

Specific T-cell receptor gene transfer enhances immune response: A potential therapeutic strategy for the control of human cytomegalovirus infection in immunocompromised patients

Human cytomegalovirus (HCMV) infection is a leading cause of morbidity and mortality in immunocompromised patients, but no specific therapeutic strategy is effective clinically, despite recent achievements. HCMV-specific T-cell therapy was thought to be helpful for the management of HCMV infection. To conduct a deep exploration, we investigated the possibility of engineering peripheral blood mononuclear cells (PBMCs) from immunocompetent and immunocompromised subjects with specific T-cell receptor (TCR) genes. CD8-positive T cells that specifically bind to NLV pentamers could be generated by transferring TCR genes to PBMCs from immunocompetent and immunocompromised subjects. The generation of functional T cells varied among transduction of different PBMCs. The numbers of IFN-γ-secreting T cells increased significantly in immunocompetent and immunodeficient PBMCs, but were unchanged in immune-reconstituted PBMCs. TCR gene transfer is a potential therapeutic strategy for controlling HCMV infection in immunocompromised patients. The transfer of TCR genes into immunocompetent and immunodeficient PBMCs would be more meaningful in response to HCMV infection than would the transfer into immune-reconstituted PBMCs.

Mouse Model of Cytomegalovirus Disease and Immunotherapy in the Immunocompromised Host: Predictions for Medical Translation that Survived the "Test of Time"

Human Cytomegalovirus (hCMV), which is the prototype member of the β-subfamily of the herpesvirus family, is a pathogen of high clinical relevance in recipients of hematopoietic cell transplantation (HCT). hCMV causes multiple-organ disease and interstitial pneumonia in particular upon infection during the immunocompromised period before hematopoietic reconstitution restores antiviral immunity. Clinical investigation of pathomechanisms and of strategies for an immune intervention aimed at restoring antiviral immunity earlier than by hematopoietic reconstitution are limited in patients to observational studies mainly because of ethical issues including the imperative medical indication for chemotherapy with antivirals. Aimed experimental studies into mechanisms, thus, require animal models that match the human disease as close as possible. Any model for hCMV disease is, however, constrained by the strict host-species specificity of CMVs that prevents the study of hCMV in any animal model including non-human primates. During eons of co-speciation, CMVs each have evolved a set of "private genes" in adaptation to their specific mammalian host including genes that have no homolog in the CMV virus species of any other host species. With a focus on the mouse model of CD8 T cell-based immunotherapy of CMV disease after experimental HCT and infection with murine CMV (mCMV), we review data in support of the phenomenon of "biological convergence" in virus-host adaptation. This includes shared fundamental principles of immune control and immune evasion, which allows us to at least make reasoned predictions from the animal model as an experimental "proof of concept." The aim of a model primarily is to define questions to be addressed by clinical investigation for verification, falsification, or modification and the results can then give feedback to refine the experimental model for research from "bedside to bench".

Virotherapy as Potential Adjunct Therapy for Graft-Vs-Host Disease

PURPOSE OF REVIEW

This review discusses the pathophysiology, risk factors, and the advances in the prevention or treatment of graft-vs-host disease (GvHD) by exploiting adjunct virotherapy. In addition, nonviral adjunct therapeutic options for the prevention of GvHD in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) are discussed. The role of oncolytic viruses to treat different HSCT-eligible hematological cancers is also considered and correlated with the issue of GvHD in the context of allo-HSCT.

RECENT FINDINGS

Emerging therapies focused on the prevention or treatment of GvHD include the use of regulatory T cells (Tregs), mesenchymal stem cells (MSCs), microbiome manipulation, B cell inhibitors, among others. Our lab and others have reported that an oncolytic DNA virus from the Poxviridae family, called myxoma virus (MYXV), not only exhibits oncolytic activity against various hematologic malignancies like multiple myeloma (MM) or acute myeloid leukemia (AML) but also, in addition, ex vivo MYXV treatment of human allogeneic-bone marrow transplants (allo-BMT), or allo-peripheral blood mononuclear cell (allo-PBMC) transplants can abrogate GvHD in xenografted mice without impairing graft-vs-tumor (GvT) effects against residual cancer. To date, this is the first and the only oncolytic virus with a dual potential of mediating oncolysis against a residual cancer target and also inhibiting or preventing GvHD following allo-HSCT.

SUMMARY

This review discusses how oncolytic virotherapy can be applied as a potential adjunct therapy for the potential treatment of GvHD. In addition, we highlight major emerging nonviral therapies currently studied for the treatment or prevention of GvHD. We also review the emerging oncolytic virotherapies against different hematological cancers currently eligible for allo-HSCT and highlight the potential role of the oncolytic virus MYXV to decrease GvHD while maintaining or enhancing the positive benefits of GvT.

Major TCR Repertoire Perturbation by Immunodominant HLA-B*44:03-Restricted CMV-Specific T Cells

Lack of disease during chronic human cytomegalovirus (CMV) infection depends on the maintenance of a high-frequency CMV-specific T cell response. The composition of the T cell receptor (TCR) repertoire underlying this response remains poorly characterised, especially within African populations in which CMV is endemic from infancy. Here we focus on the immunodominant CD8+ T cell response to the immediate-early 2 (IE-2)-derived epitope NEGVKAAW (NW8) restricted by HLA-B^*44:03, a highly prevalent response in African populations, which in some subjects represents >10% of the circulating CD8+ T cells. Using pMHC multimer staining and sorting of NW8-specific T cells, the TCR repertoire raised against NW8 was characterised here using high-throughput sequencing in 20 HLA-B^*44:03 subjects. We found that the CD8+ T cell repertoire raised in response to NW8 was highly skewed and featured preferential use of a restricted set of V and J gene segments. Furthermore, as often seen in immunity against ancient viruses like CMV and Epstein-Barr virus (EBV), the response was strongly dominated by identical TCR sequences shared by multiple individuals, or “public” TCRs. Finally, we describe a pair “superdominant” TCR clonotypes, which were germline or nearly germline-encoded and produced at remarkably high frequencies in certain individuals, with a single CMV-specific clonotype representing up to 17% of all CD8+ T cells. Given the magnitude of the NW8 response, we propose that this major skewing of CMV-specific immunity leads to massive perturbations in the overall TCR repertoire in HLA-B^*44:03 individuals.

Restoring antiviral immunity with adoptive transfer of ex-vivo generated T cells

PURPOSE OF REVIEW

Latent viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV) and adenovirus (ADV) often reactivate in immunocompromised patients, contributing to poor clinical outcomes. A rapid reconstitution of antiviral responses via adoptive transfer of virus-specific T cells (VSTs) can prevent or eradicate even refractory infections. Here, we evaluate this strategy and the associated methodological, manufacturing and clinical advances.

RECENT FINDINGS

From the early pioneering but cumbersome efforts to isolate CMV-specific T cell clones, new approaches and techniques have been developed to provide quicker, safer and broader-aimed ex-vivo antigen-specific cells. New manufacturing strategies, such as the use of G-Rex flasks or 'priming' with a library of overlapping viral peptides, allow for culturing greater numbers of cells that could be patient-specific or stored in cell banks for off-the-shelf applications. Rapid isolation of T cells using major histocompatibility complex tetramer or cytokine capture approaches, or genetic reprogramming of cells to target viral antigens can accelerate the generation of potent cellular products.

SUMMARY

Advances in the ex-vivo generation of VSTs in academic medical centres and as off-the-shelf blood bank-based or commercially produced reagents are likely to result in broader accessibility and possible manufacturing cost reduction of these cell products, and will open new therapeutic prospects for vulnerable and critically ill immunocompromised patients.

Acquired cancer resistance to combination immunotherapy from transcriptional loss of class I HLA

Understanding mechanisms of late/acquired cancer immunotherapy resistance is critical to improve outcomes; cellular immunotherapy trials offer a means to probe complex tumor-immune interfaces through defined T cell/antigen interactions. We treated two patients with metastatic Merkel cell carcinoma with autologous Merkel cell polyomavirus specific CD8+ T cells and immune-checkpoint inhibitors. In both cases, dramatic remissions were associated with dense infiltration of activated CD8+s into the regressing tumors. However, late relapses developed at 22 and 18 months, respectively. Here we report single cell RNA sequencing identified dynamic transcriptional suppression of the specific HLA genes presenting the targeted viral epitope in the resistant tumor as a consequence of intense CD8-mediated immunologic pressure; this is distinguished from genetic HLA-loss by its reversibility with drugs. Transcriptional suppression of Class I loci may underlie resistance to other immunotherapies, including checkpoint inhibitors, and have implications for the design of improved immunotherapy treatments.

Cytomegalovirus Infection: Mouse Model

This unit describes procedures for infecting newborn and adult mice with murine cytomegalovirus (MCMV). Methods are included for propagating MCMV in cell cultures and for preparing a more virulent form of MCMV from salivary glands of infected mice. A plaque assay is provided for determining MCMV titers of infected tissues or virus stocks. Also, a method is described for preparing the murine embryonic fibroblasts used for propagating MCMV and for the plaque assay. © 2018 by John Wiley & Sons, Inc.

Efficient Delivery of Human Cytomegalovirus T Cell Antigens by Attenuated Sendai Virus Vectors

Human cytomegalovirus (HCMV) represents a major cause of clinical complications during pregnancy as well as immunosuppression, and the licensing of a protective HCMV vaccine remains an unmet global need. Here, we designed and validated novel Sendai virus (SeV) vectors delivering the T cell immunogens IE-1 and pp65. To enhance vector safety, we used a replication-deficient strain (rdSeV) that infects target cells in a nonproductive manner while retaining viral gene expression. In this study, we explored the impact that transduction with rdSeV has on human dendritic cells (DCs) by comparing it to the parental, replication-competent Sendai virus strain (rcSeV) as well as the poxvirus strain modified vaccinia Ankara (MVA). We found that wild-type SeV is capable of replicating to high titers in DCs while rdSeV infects cells abortively. Due to the higher degree of attenuation, IE-1 and pp65 protein levels mediated by rdSeV after infection of DCs were markedly reduced compared to those of the parental Sendai virus recombinants, but antigen-specific restimulation of T cell clones was not negatively affected by this. Importantly, rdSeV showed reduced cytotoxic effects compared to rcSeV and MVA and was capable of mediating DC maturation as well as secretion of alpha interferon and interleukin-6. Finally, in a challenge model with a murine cytomegalovirus (MCMV) strain carrying an HCMV pp65 peptide, we found that viral replication was restricted if mice were previously vaccinated with rdSeV-pp65. Taken together, these data demonstrate that rdSeV has great potential as a vector system for the delivery of HCMV immunogens.IMPORTANCE HCMV is a highly prevalent betaherpesvirus that establishes lifelong latency after primary infection. Congenital HCMV infection is the most common viral complication in newborns, causing a number of late sequelae ranging from impaired hearing to mental retardation. At the same time, managing HCMV reactivation during immunosuppression remains a major hurdle in posttransplant care. Since options for the treatment of HCMV infection are still limited, the development of a vaccine to confine HCMV-related morbidities is urgently needed. We generated new vaccine candidates in which the main targets of T cell immunity during natural HCMV infection, IE-1 and pp65, are delivered by a replication-deficient, Sendai virus-based vector system. In addition to classical prophylactic vaccine concepts, these vectors could also be used for therapeutic applications, thereby expanding preexisting immunity in high-risk groups such as transplant recipients or for immunotherapy of glioblastomas expressing HCMV antigens.

Role of Epstein-Barr Virus in the Pathogenesis of Head and Neck Cancers and Its Potential as an Immunotherapeutic Target

The role of Epstein-Barr virus (EBV) infection in the development and progression of tumor cells has been described in various cancers. Etiologically, EBV is a causative agent in certain variants of head and neck cancers such as nasopharyngeal cancer. Proteins expressed by the EVB genome are involved in invoking and perpetuating the oncogenic properties of the virus. However, these protein products were also identified as important targets for therapeutic research in the past decades, particularly within the context of immunotherapy. The adoptive transfer of EBV-targeted T-cells as well as the development of EBV vaccines has opened newer lines of research to conceptualize novel therapeutic approaches toward the disease. This review addresses the most important aspects of the association of EBV with head and neck cancers from an immunological perspective. It also aims to highlight the current and future prospects of enhanced EBV-targeted immunotherapies.

Validation of a CD1b tetramer assay for studies of human mycobacterial infection or vaccination

CD1 tetramers loaded with lipid antigens facilitate the identification of rare lipid-antigen specific T cells present in human blood and tissue. Because CD1 proteins are structurally non-polymorphic, these tetramers can be applied to genetically diverse human populations, unlike MHC-I and MHC-II tetramers. However, there are no standardized assays to quantify and characterize lipid antigen-specific T cells present within clinical samples. We incorporated CD1b tetramers loaded with the mycobacterial lipid glucose monomycolate (GMM) into a multi-parameter flow cytometry assay. Using a GMM-specific T-cell line, we demonstrate that the assay is linear, reproducible, repeatable, precise, accurate, and has a limit of detection of approximately 0.007%. Having formally validated this assay, we performed a cross-sectional study of healthy U.S. controls and South African adolescents with and without latent tuberculosis infection (LTBI). We show that GMM-specific T cells are specifically detected in South African subjects with LTBI and not in U.S. healthy controls. This assay can be expanded to include additional tetramers or phenotypic markers to characterize GMM-specific T cells in studies of mycobacterial infection, disease, or vaccination.

Cytokine Networks and Survivin Peptide-Specific Cellular Immune Responses Predict Improved Survival in Patients With Glioblastoma Multiforme

PURPOSE

We investigated serum cytokine and T-cell responses directed against tumour-associated antigens (TAAs) in association with survival of patients with glioblastoma multiforme (GBM).

PATIENTS AND METHODS

Peripheral blood from 205 treatment-naïve patients with glioma (GBM = 145; non-GBM = 60) was obtained on the day of surgery to measure (i) circulating T-cells reacting to viral antigens and TAAs, in the presence or absence of cytokine conditioning with IL-2/IL-15/IL-21 or IL-2/IL-7, and (ii) serum cytokine levels (IL-4, IL-5, IL-6, TNF-α, IFN-γ and IL-17A). Patients were followed-up for at least 1000 days post-surgery. Survivin protein and gene expression in resected GBM tumour tissue were confirmed by immunohistochemistry and real-time polymerase chain reaction, respectively. Antigen-specific T-cell responses were gauged by ICS (intracellular cytokine production). Associations between patient survival and immunological reactivity patterns were analysed using univariate and multivariate statistics.

RESULTS

Approximately 2% of patients with GBM and 18% of patients with non-GBM glioma, were alive beyond 1000 days of surgery. Univariate analysis indicated that the combination of three cytokines (IL-4/IL-5/IL-6, p = .0022; IFN-γ/TNF-α/IL-17A, p = .0083) but not a 'partial' combination of these cytokines, the IFN-γ immune response to EBV-EBNA-1 (p < .0001) as well as T-cell responses to the survivin_97-111 peptide (p = .0152) correlated with longer survival among patients with GBM. Multivariate analysis identified survivin_97-111-directed IFN-γ production with IL-2/IL-15/IL-21 conditioning (p = .024), and the combined presence of serum IFN-γ/TNF-α/IL-17a (p = .003) as independent predictors of survival.

CONCLUSION

Serum cytokine patterns and lymphocyte reactivity to survivin_97-111, particularly with IL-2, IL-15 and IL-21 conditioning may be instrumental in predicting survival among patients with GBM. This has implications for clinical follow-up of patients with GBM and the targeted development of immunotherapy for patients with CNS tumours.

A Diverse Lipid Antigen-Specific TCR Repertoire Is Clonally Expanded during Active Tuberculosis

Human T cells that recognize lipid Ags presented by highly conserved CD1 proteins often express semi-invariant TCRs, but the true diversity of lipid Ag-specific TCRs remains unknown. We use CD1b tetramers and high-throughput immunosequencing to analyze thousands of TCRs from ex vivo-sorted or in vitro-expanded T cells specific for the mycobacterial lipid Ag, glucose monomycolate. Our results reveal a surprisingly diverse repertoire resulting from editing of germline-encoded gene rearrangements analogous to MHC-restricted TCRs. We used a distance-based metric (TCRDist) to show how this diverse TCR repertoire builds upon previously reported conserved motifs by including subject-specific TCRs. In a South African cohort, we show that TCRDist can identify clonal expansion of diverse glucose monomycolate-specific TCRs and accurately distinguish patients with active tuberculosis from control subjects. These data suggest that similar mechanisms govern the selection and expansion of peptide and lipid Ag-specific T cells despite the nonpolymorphic nature of CD1.

Rapid reconstitution of CMV-specific T-cells after stem-cell transplantation

OBJECTIVE

As reconstitution of virus-specific T-cells is critical to control cytomegalovirus (CMV)-viremia following stem-cell transplantation (SCT), we characterized the dynamics in CMV-specific T-cell reconstitution after SCT.

METHODS

Cytomegalovirus-specific T-cells from 51 SCT-recipients were prospectively quantified and phenotypically characterised by intracellular cytokine-staining after specific stimulation and HLA class-I-specific pentamers using flow cytometry.

RESULTS

Cytomegalovirus-specific CD4 T-cells reconstituted after a median of 2.3 (IQR, 2.0-3.0) weeks following autografting, and 4.0 (IQR, 3.0-5.6) weeks after allografting, with CMV-specific T-cells originating from donors and/or recipients. The time for reconstitution of CMV-specific CD4 and CD8 T-cells did not differ (P = .58). Factors delaying the time to initial reconstitution of CMV-specific CD4 T-cells included a negative recipient serostatus (P = .016) and CMV-viremia (P = .026). Percentages of CMV-specific CD4 T-cells significantly increased over time and reached a plateau after 90 days (P = .043). Relative CMV-specific CD4 T-cell levels remained higher in long-term transplant recipients compared with those in controls (P < .0001). However, due to persisting lymphopenia, absolute numbers of CMV-specific T-cells were similar as in controls.

CONCLUSION

Cytomegalovirus-specific T-cells rapidly reconstitute after SCT and their percentages remain high in the long term. In the face of persistent lymphopenia, this results in similar absolute numbers of CMV-specific T-cells as in controls to ensure sufficient pathogen control.

BK Polyomavirus Immune Response With Stress on BK-Specific T Cells

Polyomavirus-associated nephropathy is a pertinent cause of poor renal allograft survival. Absence of defensive immunity toward BK polyomavirus may favor the occurrence of BK polyomavirus-active infection and influence the progression to polyomavirus-associated nephropathy. Humoral immune responses may offer incomplete protection. In this review, available data on both humoral and cellular immunity were examined, with a concentration on BK polyomavirus-specific T cells; in addition, their roles in BK polyomavirus cellular immune response and immunotherapy were discussed. This traditional narrative review used PubMed and Medline searches for English language reports on BK polyomavirus immune response and BK-specific T cells published between January 1990 and November 2017. The search included the key words BK virus, BK polyomavirus, immune and response, and specific T cells. Monitoring BK polyomavirus-specific T cells has both therapeutic and prognostic value. Innovative cellular immunotherapy approaches, including development of vaccinations and infectious recombinant BK polyomavirus, could further contribute to the prevention of BK polyomavirus infection and related diseases.

Clinical-grade generation of peptide-stimulated CMV/EBV-specific T cells from G-CSF mobilized stem cell grafts

Background

A major complication after allogeneic hematopoietic stem cell transplantation (aSCT) is the reactivation of herpesviruses such as cytomegalovirus (CMV) and Epstein–Barr virus (EBV). Both viruses cause significant mortality and compromise quality of life after aSCT. Preventive transfer of virus-specific T cells can suppress reactivation by re-establishing functional antiviral immune responses in immunocompromised hosts.

Methods

We have developed a good manufacturing practice protocol to generate CMV/EBV-peptide-stimulated T cells from leukapheresis products of G-CSF mobilized and non-mobilized donors. Our procedure selectively expands virus-specific CD8+ und CD4+ T cells over 9 days using a generic pool of 34 CMV and EBV peptides that represent well-defined dominant T-cell epitopes with various HLA restrictions. For HLA class I, this set of peptides covers at least 80% of the European population.

Results

CMV/EBV-specific T cells were successfully expanded from leukapheresis material of both G-CSF mobilized and non-mobilized donors. The protocol allows administration shortly after stem cell transplantation (d30+), storage over liquid nitrogen for iterated applications, and protection of the stem cell donor by avoiding a second leukapheresis.

Conclusion

Our protocol allows for rapid and cost-efficient production of T cells for early transfusion after aSCT as a preventive approach. It is currently evaluated in a phase I/IIa clinical trial.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1498-3) contains supplementary material, which is available to authorized users.

Early Env-specific CTLs effectively suppress viral replication in SHIV controller macaques

Early immunological events in acute HIV infection are thought to fundamentally influence long-term disease outcomes. Though the contribution of Gag-specific CD8 T cell responses to early viral control is well established, little is known about the role of Env-specific CD8 T cell responses in controlling viral replication during acute infection. In a macaque simian-human immunodeficiency virus (SHIV) model, some macaques who were able to control SHIV replication after ART interruption showed expansion of Env-specific CD8 T cell responses during acute infection, compared to macaques who progressed to viral rebound. To better understand the function of early Env-specific CD8 T cells, we isolated, expanded and examined their ability to act as effectors in vitro. We observed that Env-specific CD8 T cell clones have the capacity to directly recognize and kill SHIV-infected CD4 T cells, but failed to reduce viral replication in SHIV-infected macrophages. Our data suggest that early Env-specific CD8 T cell responses during acute SHIV infection contribute substantially to the control of viral replication. The T-cell clones composing of Env-specific effector cells demonstrates in vitro phenotypic and functional characteristics with the potentials to provide longlasting clinical benefit of in vivo HIV study.

Novel Immunotherapy Options for Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma (ENKTCL) is a highly aggressive mature NK/T-cell neoplasm marked by NK-cell phenotypic expression of CD3ε and CD56. While the disease is reported worldwide, there is a significant geographic variation with its highest incidence in East Asian countries possibly related to the frequent early childhood exposure of Epstein-Barr virus (EBV) and specific ethnic-genetical background, which contributes to the tumorigenesis. Historically, anthracycline-based chemotherapy such as CHOP (cyclophosphamide, adriamycin, vincristine, and prednisone) was used, but resulted in poor outcomes. This is due in part to intrinsic ENKTCL resistance to anthracycline caused by high expression levels of P-glycoprotein. The recent application of combined modality therapy with concurrent or sequential radiation therapy for early stage disease, along with non-anthracycline-based chemotherapy regimens consisting of drugs independent of P-glycoprotein have significantly improved clinical outcomes. Particularly, this neoplasm shows high sensitivity to l-asparaginase as NK-cells lack asparagine synthase activity. Even still, outcomes of patients with advanced stage disease or those with relapsed/recurrent disease are dismal with overall survival of generally a few months. Thus, novel therapies are needed for this population. Clinical activity of targeted antibodies along with antibody-drug conjugates, such as daratumumab (naked anti-CD38 antibody) and brentuximab vedotin (anti-CD30 antibody conjugated with auristatin E), have been reported. Further promising data have been shown with checkpoint inhibitors as high levels of programmed death-ligand 1 expression are observed in ENKTCL due to EBV-driven overexpression of the latent membrane proteins [latent membrane protein 1 (LMP1) and LMP2] with activation of the NF-κB/MAPK pathways. Initial case series with programmed death 1 inhibitors showed an overall response rate of 100% in seven relapsed patients including five with a complete response (CR). Furthermore, cellular immunotherapy with engineered cytotoxic T lymphocytes targeted against LMP1 and LMP2 have shown encouraging results with durable CRs as either maintenance therapy after initial induction chemotherapy or in the relapsed/refractory setting. In this paper, we review this exciting field of novel immunotherapy options against ENKTCL that hopefully will change the treatment paradigm in this deadly disease.

Hematopoietic stem cell transplantation in its 60s: A platform for cellular therapies

Over the last 60 years, more than a million patients received hematopoietic cell transplantation. Having incorporated multiple changes in clinical practices, it remains a complex procedure facing a dual challenge: cure of the underlying disease and prevention of relapse while controlling potentially severe complications. Improved understanding of underlying biological processes resulted in the design of innovative therapies engineered from defined cell populations and testing of these therapies as addition or substitution at virtually every step of the procedure. This review provides an overview of these developments, many of them now applied outside the historical field of hematopoietic cell transplantation.

Cytomegalovirus-Specific CD8+ T-Cells With Different T-Cell Receptor Affinities Segregate T-Cell Phenotypes and Correlate With Chronic Graft-Versus-Host Disease in Patients Post-Hematopoietic Stem Cell Transplantation

Virus-specific T-cell responses are crucial to control cytomegalovirus (CMV) infections/reactivation in immunocompromised individuals. Adoptive cellular therapy with CMV-specific T-cells has become a viable treatment option. High-affinity anti-viral cellular immune responses are associated with improved long-term immune protection against CMV infection. To date, the characterization of high-affinity T-cell responses against CMV has not been achieved in blood from patients after allogeneic hematopoietic stem cell transplantation (HSCT). Therefore, the purpose of this study was to describe and analyze the phenotype and clinical impact of different CMV-specific CD8+ cytotoxic T-lymphocytes (CMV-CTL) classes based on their T-cell receptor (TCR) affinity. T-cells isolated from 23 patients during the first year following HSCT were tested for the expression of memory markers, programmed cell death 1 (PD-1), as well as TCR affinity, using three different HLA-A*02:01 CMVNLVPMVATV-Pp65 tetramers (wild-type, a245v and q226a mutants). High-affinity CMV-CTL defined by q226a tetramer binding, exhibited a higher frequency in CD8+ T-cells in the first month post-HSCT and exhibited an effector memory phenotype associated with strong PD-1 expression as compared to the medium- and low-affinity CMV-CTLs. High-affinity CMV-CTL was found at higher proportion in patients with chronic graft-versus-host disease (p < 0.001). This study provides a first insight into the detailed TCR affinities of CMV-CTL. This may be useful in order to improve current immunotherapy protocols using isolation of viral-specific T-cell populations based on their TCR affinity.