Virus-specific T-cell Therapy Research Articles

Evaluation of CMV T-cell Mediated Immunity in Children with CMV DNAemia After Allogeneic Hematopoietic Cell Transplantation

Abstract Background Cytomegalovirus (CMV) is among the most common infectious complications following allogeneic hematopoietic cell transplantation (allo-HCT). A commercially available CMV T-cell immune panel (CMV-TCIP, Viracor®), reported as percentages of CMV-specific interferon gamma releasing CD4 and CD8 cells (%CMV-CD4 or %CMV-CD8 IFN-γ), may be used to assess CMV cell-mediated immunity (CMV-CMI). However, the utility of this assay among pediatric allo-HCT recipients remains unknown. Methods A retrospective analysis among pediatric allo-HCT recipients (age ≤18 years) from 1/2020 to 11/2023 who developed CMV DNAemia and had CMV-TCIP testing was performed. Per institutional protocol, weekly quantitative plasma CMV PCR was performed until day +100. Clinically significant CMV infection (csCMVi) was defined as CMV viral load (VL) ≥500IU/ml and pre-emptive therapy (PET) was provided for csCMVi. The most frequent indications for CMV-TCIP testing were to evaluate CMV-CMI to inform the need of CMV virus-specific T-cell therapy (CMV-VST) in the setting of resistant/refractory CMV, to monitor CMV-CMI as a proxy of VST expansion post CMV-VST, or to evaluate the need of ongoing secondary antiviral prophylaxis. A %CMV-CD4 or %CMV-CD8 IFN-γ ≤0.2% was categorized as a poor response, whereas a result >0.2% was classified as an adequate response. Specimens with insufficient quality, high background, or discrepant results from %CMV-CD4 or %CMV-CD8 were classified as a discordant response. Demographics, underlying condition, HCT type, conditioning regimen, antiviral agents and use of VST, VL, and CMV-TCIP results were recorded. Descriptive and nonparametric statistics (median, interquartile range [IQR]) were used for analysis. Results Twenty-seven CMV-TCIP results from 10 unique allo-HCT recipients were analyzed. The median age at transplant was 8.5 years (IQR 2.75-14.3), predominantly for hematologic malignancy (70%). CMV donor/recipient (D/R) serostatus were D+/R+ (60%), D-/R+ (30%) and D+/R- (10%). CMV DNAemia developed post-HCT in 80% (8/10) with median onset of 4 days post-HCT (IQR 3-40) and 2 subjects had known DNAemia prior to HCT. Nine (90%) subjects were started on PET for csCMVi, whereas 1 (10%) received antiviral therapy when VL was <500IU/ml. The first CMV-TCIP was obtained at median of 112 days (IQR 42-130) post-HCT. Despite appropriate antiviral therapy, patients with a peak VL ≥500 IU/mL (obtained within 1 week before and after CMV-TCIP testing) demonstrated significantly lower absolute CD4 (median 12 vs. 198 cells/uL, p=0.02) and CD8 (median 79 vs. 443 cells/uL, p=0.04) counts and %CMV-CD4 IFN-γ (0.04% vs. 0.36%, p=0.02) compared to those with a peak VL <500 IU/mL. Conclusion Our results suggest that CMV-CMI, particularly %CMV-CD4 IFN-γ >0.2%, was observed concurrently with downward trending VL, and may serve as a proxy of VST expansion in patients receiving CMV-VSTs. Figure 1A. The distribution of peak VLs over time based on %CMV-CD4 and %CMV-CD8 IFN-γ are demonstrated in Figure 1B. CMV peak VLs were lower with TCIP testing results reported as adequate combined responses compared to those with poor combined responses. In five subjects (50%) who received CMV-VSTs as part of CMV therapy, increased %CMV-CD4 and %CMV-CD8 IFN-γ were observed post-infusion with an observed downward trend in VL.

Immune reconstitution and cidofovir administration rescue human adenovirus hepatitis after allogeneic hematopoietic cell transplantation

Human adenovirus infection (HAdV) may be fatal in patients undergoing allogeneic hematopoietic cell transplantation (HCT). Cidofovir is effective in only a part of the post-HCT HAdV infection. Therefore, posttransplant immune reconstitution is important for HAdV clearance. We describe the detailed immune reconstitution and response of adenovirus-specific T cells in a patient with inborn errors of immunity who had disseminated HAdV infection with hepatitis post-HCT and was treated with cidofovir.Though the patient received cidofovir for only 19 days starting from Day 72 after HCT because of renal dysfunction, we observed T-cell reconstitution, a decrease in HAdV copy number, and amelioration of the symptoms of HAdV infection after Day 90. We initially observed expanded NK and CD8+CD45RO+ memory subsets and later gradual increase of naïve T cells eveloped after cessation of cidofovir treatment. An increase in adenovirus-specific IFN-γ secretion from 2 to 4 months after HCT was confirmed by ELISpot assay.The progression of immune reconstitution and cidofovir treatment are considered to have contributed to survival in this patient. Optimization of transplantation methods, prompt appropriate antiviral medication, and virus-specific T-cell therapy would be necessary as the better strategy for systemic HAdV infection.

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

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. 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). 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. 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.

Viral specific T cell therapy in kidney transplant recipients - A single-center experience.

Viral infections such as adenovirus (ADV), BK virus (BKV), and cytomegalovirus (CMV) after kidney transplantation negatively impact outcomes in transplant recipients despite advancements in screening and antiviral therapy. We describe our experience of using the virus-specific T cell therapy (VSTs) in kidney transplant recipients (KTR) at our transplant center. This is a retrospective, single center review of KTR with ADV, BKV and CMV infections between June 2021 and December 2022. These patients received third party VSTs as part of the management of infections. The immunosuppression, details of infection and outcome data were obtained from electronic medical records. Two cases of ADV infection resolved after one infusion of VSTs. The response rate of BKV and CMV infection was not as robust with close to 50% reduction in median viral load after VSTs. Out of 23 patients, two patients developed chronic allograft nephropathy from membranoproliferative glomerulonephritis and acute rejection. Patients that are resistant to antivirals or who have worsening viremia despite conventional management may benefit from VSTs therapy to treat underlying viral infection. Additional studies are needed to ascertain efficacy and short- and long-term risks secondary to VSTs.

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

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

Update on COVID-19 Therapeutics for Solid Organ Transplant Recipients, Including the Omicron Surge.

Major changes have occurred in therapeutics for coronavirus-19 (COVID-19) infection over the past 12–18 mo, most notably in early outpatient therapy. In most cases, solid organ transplant recipients were not included in the original clinical trials of these agents, so studies of real-world outcomes have been important in building our understanding of their utility. This review examines what is known about clinical outcomes in solid organ transplant recipients with newer therapies. SARS-CoV-2 monoclonal antibodies for early treatment or prophylaxis have likely prevented many hospitalizations and deaths. In addition, convalescent plasma, the oral drugs nirmatrelvir/ritonavir and molnupiravir, remdesivir for early outpatient treatment, anti-inflammatory therapy, and investigational virus-specific T-cell therapy will be discussed. Finally, the later consequences of COVID-19, such as secondary infections, long COVID symptoms, and persistent active infection, are identified as areas for future research.

Epstein Barr virus–positive B-cell lymphoma is highly vulnerable to MDM2 inhibitors in vivo

AbstractEpstein-Barr virus–positive (EBV-positive) B-cell lymphomas are common in immunocompromised patients and remain an unmet medical need. Here we report that MDM2 inhibitors (MDM2is) navtemadlin and idasanutlin have potent in vivo activity in EBV-positive B-cell lymphoma established in immunocompromised mice. Tumor regression was observed in all 5 EBV-positive xenograft–associated B-cell lymphomas treated with navtemadlin or idasanutlin. Molecular characterization showed that treatment with MDM2is resulted in activation of p53 pathways and downregulation of cell cycle effectors in human lymphoma cell lines that were either EBV-positive or had undetectable expression of BCL6, a transcriptional inhibitor of the TP53 gene. Moreover, treatment with navtemadlin resulted in tumor regression and prevented systemic dissemination of EBV-positive lymphoma derived from 2 juvenile patients with posttransplant lymphoproliferative diseases, including 1 whose tumor was resistant to virus-specific T-cell therapy. These results provide proof-of-concept for targeted therapy of EBV-positive lymphoma with MDM2is and the feasibility of using EBV infection or loss of BCL6 expression to identify responders to MDM2is.

Viral infections after hematopoietic cell transplantation and treatment with virus-specific T-cell therapies

Viral infections are one of the leading causes of death in hematopoietic cell transplantation (HCT) and are a problem that should be resolved. For post-HCT viral infections, reduction of antiviral treatment or immunosuppressive drug dose is generally performed; however, the effect of antiviral drug is sometimes limited, and reduction of immunosuppressive treatment might worsen the graft-versus-host disease. Therefore, appropriate infection preventive measures and early diagnosis and therapeutic intervention for viral infections are important. In addition, virus-specific T-cell (VST) therapy is attracting attention as a new treatment method for intractable and refractory post-HCT viral infections. Various methods have been developed to establish VSTs, from a single- to multiple-virus targeting and from related- to third-party-derived donors. Its safety and efficacy have already been reported in clinical trials, and thereby, it is expected to be established as one of the important treatments for post-HCT viral infections.

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

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

Complement inhibition does not impair the clinical antiviral capabilities of virus-specific T-cell therapy

Key Points The use of terminal complement blockade is compatible with virus-specific T-cell (VST) expansion and clinical effectiveness. VST and complement-blocking agent concurrent therapy may be safely used in patients with thrombotic microangiopathy and viral infections.

Progressive multifocal leukoencephalopathy in a patient post allo-HCT successfully treated with JC virus specific donor lymphocytes

BackgroundProgressive multifocal leukoencephalopathy is a demyelinating CNS disorder. Reactivation of John Cunningham virus leads to oligodendrocyte infection with lysis and consequent axonal loss due to demyelination. Patients usually present with confusion and seizures. Late diagnosis and lack of adequate therapy options persistently result in permanent impairment of brain functions. Due to profound T cell depletion, impairment of T-cell function and potent immunosuppressive factors, allogeneic hematopoietic cell transplantation recipients are at high risk for JCV reactivation. To date, PML is almost universally fatal when occurring after allo-HCT.MethodsTo optimize therapy specificity, we enriched JCV specific T-cells out of the donor T-cell repertoire from the HLA-identical, anti-JCV-antibody positive family stem cell donor by unstimulated peripheral apheresis [1]. For this, we selected T cells responsive to five JCV peptide libraries via the Cytokine Capture System technology. It enables the enrichment of JCV specific T cells via identification of stimulus-induced interferon gamma secretion.ResultsDespite low frequencies of responsive T cells, we succeeded in generating a product containing 20 000 JCV reactive T cells ready for patient infusion. The adoptive cell transfer was performed without complication. Consequently, the clinical course stabilized and the patient slowly went into remission of PML with JCV negative CSF and containment of PML lesion expansion.ConclusionWe report for the first time feasibility of generating T cells with possible anti-JCV activity from a seropositive family donor, a variation of virus specific T-cell therapies suitable for the post allo transplant setting. We also present the unusual case for successful treatment of PML after allo-HCT via virus specific T-cell therapy.

Adverse Effects of Virus-Specific T-Cell Therapy: An Integrative Review

Allogeneic hematopoietic stem cell transplant (HSCT) remains the mainstay in treating many hematologic malignancies. T-cell-depleted grafts designed to reduce graft-vs.-host disease (GVHD) may be complicated by severe viral infections that increase morbidity and mortality. Despite the use of antiviral pharmacologic therapy, challenges in controlling viral infections include drug resistance and/or side-effect intolerability. Virus-specific T-cell (VST) therapy is a promising targeted therapy for treating severe or drug-refractory viral infections after HSCT. An integrative review was conducted to inform advanced practitioners of the adverse effects associated with VST. A total of 836 articles were identified using PubMed, Scopus, and CINAHL databases, with 7 included in this review. Studies reviewed indicate that the adverse effects associated with VST therapy are limited and generally treatable. These studies reported low rates of adverse events of mild to moderate severity, including acute, recurrent, chronic, and de novo GVHD; cytokine release syndrome; infusion toxicity; and other adverse events. No deaths were attributed to VSTs in these studies.

Confirmation of High Resolution Antiviral HLA Restrictions Correlates with Antiviral Responses Following Virus-Specific T-Cell Therapy

Background Adoptive immunotherapy using virus-specific T-lymphocytes (VSTs) have been successful in treating viral infections in immunocompromised patients, and use of VSTs from healthy third-party donors have improved the accessibility and timeliness of this therapy. However, best methods of donor/recipient matching of HLA-mismatched VST products remain unclear. Objective To determine the factors influencing the chances of antiviral responses following VST therapy between HLA-mismatched donor/recipient pairs. Design/Methods Patients who received HLA-mismatched VST infusions for active infections with CMV, Epstein-Barr virus, or adenovirus were analyzed for response. Antiviral response was defined as >1 log decrease in viral load within 3 months of VST infusion. Degree of high and low resolution HLA match was determined, and presence of confirmed antiviral HLA restrictions in the utilized VST products was recorded. Unpaired, 2-tailed T-tests were performed for group comparisons. Results Twenty one patients received 30 VST infusions with 27 T-cell products (20 from third-party donors, and 7 from mismatched related donors). Eleven patients were treated for CMV, 8 for adenovirus, and 2 for EBV infection. All patients had persistent viral infections in spite of standard antiviral therapy prior to study enrollment. Seven patients were admitted to intensive care units due to severe viral disease and received VSTs under expanded access for emergency treatment. Overall, of this poor prognosis patient cohort, 12 achieved antiviral responses within 3 months of infusion (2 of 7 patients who received VST derived from MMRD, and 10 of 20 patients who received third-party VSTs). Of 25 evaluable infusions, chances of antiviral response following VST infusion were greater when utilizing a VST product with a confirmed antiviral HLA restriction that is shared at high resolution with the recipient (p=0.02). There was no difference in overall degree of HLA match between responders and non-responders (p=0.83). Conclusions VST matching based on sharing of high resolution HLA alleles that mediate target antiviral restrictions is more successful than overall degree of HLA match. Further testing of this methodology for VST therapy is ongoing in a current phase II trial (PBMTC SUP1701).

Early Experience With CliniMACS Prodigy CCS (IFN-gamma) System in Selection of Virus-specific T Cells From Third-party Donors for Pediatric Patients With Severe Viral Infections After Hematopoietic Stem Cell Transplantation.

Viral reactivation is a frequent complication of allogeneic hematopoietic stem cell transplantation especially in children. For refractory cases, rapid virus-specific T-cell therapy would be ideally implemented within a few days. Over the course of a year in our pediatric cohort of 43 allogeneic transplantation, 9 patients fulfilled criteria for virus-specific T-cell therapy. Viral infections were due to cytomegalovirus (CMV) in 3, Epstein-Barr virus (EBV) in 2, and adenovirus (AdV) in 1 case, whereas >1 virus was detected in 3 cases. Viral diseases necessitating a T-cell therapy were CMV pneumonitis and colitis, AdV enteritis and cystitis, and EBV-induced posttransplantation lymphoproliferative disease. Cells were produced by the CliniMACS Prodigy CCS (IFN-gamma) System within 24 hours after mononuclear leukapheresis. Eight patients became completely asymptomatic, whereas 7 also cleared the virus. Six patients are alive without viral illness or sequelae demonstrating viral DNA clearance in peripheral blood with a median follow-up of 535 (350-786) days. One patient with CMV pneumonitis died of respiratory insufficiency. In 2 cases the viral illness improved or cleared, however, the patients died of invasive aspergillosis. No cases of graft-versus-host disease, rejection, organ toxicity, or recurrent infection were noticed. Virus-specific T-cell therapy implemented by the CliniMACS Prodigy CCS (IFN-gamma) System is an automated, fast, safe, and probably effective way to control resistant viral diseases after pediatric hematopoietic stem cell transplantation.

Immunotherapy for refractory viral infections

Various antiviral agents have been developed, which are sometimes associated with toxicity, development of virus-resistant strain, and high cost. Virus-specific T-cell (VST) therapy provides an alternative curative therapy that can be effective for a prolonged time without eliciting drug resistance. VSTs can be directly separated using several types of capture devices and can be obtained by stimulating peripheral blood mononuclear cells with viral antigens (virus, protein, or peptide) loaded on antigen-presenting cells (APC). APC can be transduced with virus-antigen coding plasmid or pulsed with overlapping peptides. VST therapy has been studied in drug non-responsive viral infections after hematopoietic cell transplantation (HCT). Several previous studies have demonstrated the efficacy of VST therapy without significant severe GVHD. In addition, VSTs from a third-party donor have been prepared and administered for post-HCT viral infection. Although target viruses of VSTs include herpes virus species and polyomavirus species, a wide variety of pathogens, such as papillomavirus, intracellular bacteria, and fungi, can be treated by pathogen-specific T-cells. Perhaps, these specific T-cells could be used for opportunistic infections in other immunocompromised hosts in the near future.

Immunotherapy using T cells for treating viral infections

Recipients of hematopoietic stem cell transplantation suffering from severe immunosuppression and immune dysregulation because of GVHD or other causes are at higher risk of viral infection. Often, cytomegalovirus and EB virus are reactivated from their latent state in these patients ; viral infections thus remain a primary cause of severe morbidity and mortality. Since the 1990s, virus-specific T cells have been generated by different methods using immunogenic epitope peptides or EBV-LCL from transplant donors, and studies have demonstrated the efficacy of these methods. However, establishing such order-made, virus-specific T cells requires 8-10 weeks, which is not feasible for application in the frontline of clinics. Recent advances, such as direct donor T cell selection using peptide-HLA multimers or cytokine capture method and virus-specific T cells bank generated using third-party donors, facilitated the broadening of the applicability of this method. The clinical development of virus-specific T-cell therapy is considered as the prototype of future T-cell immunotherapy for various infections or malignant diseases.

Human parainfluenza virus-3 can be targeted by rapidly ex vivo expanded T lymphocytes

Background aimsHuman parainfluenza virus-3 (HPIV) is a common cause of respiratory infection in immunocompromised patients and currently has no effective therapies. Virus-specific T-cell therapy has been successful for the treatment or prevention of viral infections in immunocompromised patients but requires determination of T-cell antigens on targeted viruses. MethodsHPIV3-specific T cells were expanded from peripheral blood of healthy donors using a rapid generation protocol targeting four HPIV3 proteins. Immunophenotyping was performed by flow cytometry. Viral specificity was determined by interferon (IFN)-γ ELISpot, intracellular cytokine staining and cytokine measurements from culture supernatants by Luminex assay. Cytotoxic activity was tested by 51Cr release and CD107a mobilization assays. Virus-specific T cells targeting six viruses were then produced by rapid protocol, and the phenotype of HPIV3-specific T cells was determined by immunomagnetic sorting for IFN-γ-producing cells. ResultsHPIV3-specific T cells were expanded from 13 healthy donors. HPIV3-specific T cells showed a CD4+ predominance (mean CD4:CD8 ratio 2.89) and demonstrated specificity for multiple HPIV3 antigens. The expanded T cells were polyfunctional based on cytokine production but only had a minor cytotoxic component. T cells targeting six viruses in a single product similarly showed HPIV3 specificity, with a predominant effector memory phenotype (CD3+/CD45RA–/CCR7–) in responder cells. DiscussionHPIV3-specific T cells can be produced using a rapid ex vivo protocol from healthy donors and are predominantly CD4+ T cells with Th1 activity. HPIV3 epitopes can also be successfully targeted alongside multiple other viral epitopes in production of six-virus T cells, without loss of HPIV3 specificity. These products may be clinically beneficial to combat HPIV3 infections by adoptive T-cell therapy in immune-compromised patients.

Virus-specific T-cell therapy in solid organ transplantation.

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

Simple and efficient generation of virus-specific T cells for adoptive therapy using anti-4-1BB antibody.

Although recent studies of virus-specific T-cell (VST) therapy for viral infections after allogeneic hematopoietic stem cell transplantation have shown promising results, simple and less time-intensive and labor-intensive methods are required to generate VSTs for the wider application of VST therapy. We investigated the efficacy of anti-CD28 and anti-4-1BB antibodies, which can provide T cells with costimulatory signals similar in strength to those of antigen-presenting cells, in generating VSTs. When peripheral blood mononuclear cells were stimulated with viral peptides together with isotype control, anti-CD28, or anti-4-1BB antibodies, anti-4-1BB antibodies yielded the highest numbers of VSTs, which were on an average 7.9 times higher than those generated with isotype control antibody. The combination of anti-CD28 and anti-4-1BB antibodies did not result in increased numbers of VSTs compared with anti-4-1BB antibody alone. Importantly, the positive effect of anti-4-1BB antibody was observed regardless of the epitopes of the VSTs. In contrast, the capacity of dendritic cells (DCs) to generate VSTs differed considerably depending on the epitopes of the VSTs. Furthermore, the numbers of VSTs generated with DCs were at most similar to those generated with the anti-4-1BB antibody. Generation of VSTs with anti-4-1BB antibody did not result in excessive differentiation or deteriorated function of the generated VSTs compared with those generated with control antibody or DCs. In conclusion, VSTs can be generated rapidly and efficiently by simply stimulating peripheral blood mononuclear cells with viral peptide and anti-4-1BB antibody without using antigen-presenting cells. We propose using anti-4-1BB antibody as a novel strategy to generate VSTs for adoptive therapy.

Moving Successful Virus-specific T-cell Therapy for Hematopoietic Stem Cell Recipients to Late Phase Clinical Trials

There are now multiple effective strategies for the activation and expansion, or direct selection of virus-specific T cells that may be able to eliminate a range of virus infections in the immunocompromised host. In this mini-review, we explain how the stage is set for their rigorous evaluation in large-scale clinical trials. Virus infections are the cause of 30% or more of transplant-related deaths in recipients of T-cells depleted, allogeneic hematopoietic stem cell transplants (HSCT).1 Epstein-Barr virus (EBV), cytomegalovirus (CMV), and adenoviruses (AdV) are the most common culprits, but other common viruses like parainfluenza virus, respiratory syncytial virus, influenza viruses, polyomaviruses, and human herpesvirus 6 together contribute significant morbidity and mortality (Figure 1).2,3,4 Small molecule therapies are often ineffectual, always costly and frequently produce significant adverse effects. Figure 1 Relative frequency of viral infections after HSCT. Adv, adenovirus; BK, JC, KI, and WU (polyomaviruses); CMV, cytomegalovirus; H1N1, influenza strain Hemagglutinnin 1 Neuraminidase 1); HHV, human herpes virus; HSCT, hematopoietic stem cell transplant; ... Virus-specific T-cells derived from stem cell donors can prevent and treat post-transplant viral infections, in the recipients for whom they were intended, and also in partially human leukocyte antigen (HLA)-matched, third party recipients.5,6,7 The low toxicity and long-term protection provided by virus-specific T-cells compares favorably with the significant toxicities and short-term effects of most antivirals.5,6,8,9,10 Is it time, therefore, to begin the transfer of T-cell manufacturing from academic phase I/II clinical trials into hospital or industry-supported facilities so that virus-specific T-cells can be made available to all high-risk HSCT recipients? Several barriers prevent the broader use of virus-specific T-cell therapies after stem cell transplantation. While T-cell therapies for EBV, CMV, and AdV have clearly demonstrated their safety and efficacy both as prophylaxis and as therapy, for many other viruses, the antigens that induce protective T-cells have yet to be identified. Moreover, these infections may occur in <5% of patients making it difficult to perform the rigorous comparative effectiveness studies that will be required to show lower overall cost, fewer adverse effects, and equivalent or superior efficacy. Before any of these barriers can be breached effectively by the academic institutions who are the major developers of these T-cells therapeutics, we must select and optimize manufacturing strategies that are robust and scalable and have the lowest possible cost. Finally, the leap to late phase trials cannot be accomplished by academic institutions alone, but requires partnership with industry. This article will largely deal with selection and optimization of virus-specific T-cell manufacturing strategies.