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

Graft versus leukemia response without graft-versus-host disease elicited by adoptively transferred multivirus-specific T-cells

A 12-year-old boy with refractory acute lymphoblastic leukemia received a haploidentical transplant from his mother. As prophylaxis for Epstein-Barr virus (EBV), cytomegalovirus (CMV) and adenovirus, he received ex vivo expanded virus-specific donor T cells 3.5 months after transplant. Four weeks later leukemic blasts bearing the E2A deletion, identified by fluorescent in situ hybridization (FISH), appeared transiently in the blood followed by a FISH-negative hematological remission, which was sustained until a testicular relapse 3.5 months later. Clearance of the circulating leukemic cells coincided with a marked increase in circulating virus-specific T cells. The virus-specific cytotoxic T-cell (CTL) line showed strong polyfunctional reactivity with the patient's leukemic cells but not phytohemagglutinin (PHA) blasts, suggesting that virus-specific CTL lines may have clinically significant antileukemia activity.

Differential expression of THELPER 1 cytokines upon antigen stimulation predicts ex vivo proliferative potential and cytokine production of virus-specific T cells following re-stimulation

INTRODUCTION

Cytomegalovirus (CMV) and human adenovirus (ADV) infections are causes of morbidity after stem cell transplantation. Antigen (Ag)-specific T cells are essential for the control of viral infections. However, in vivo expansion potential of T-cell subpopulations is hardly predictable in humans. Furthermore, ex vivo identification of human T cells with repopulating capacity for adoptive T-cell transfer has been difficult.

METHODS

We analyzed Ag-specific T-cell populations, subdivided according to the expression of different THELPER- 1 (Th1) cytokines. Isolation by flow cytometry was based on interferon-gamma (IFN)-γ, interleukin (IL)-2, or tumor necrosis factor-alpha (TNF-α) secretion of T cells after ex vivo stimulation with the Ags hexon (for ADV) and pp65 (for CMV). Isolated T cells were expanded and examined for functional characteristics, expansion/differentiation potential, and naïve, effector memory, central memory, and late effector phenotypes.

RESULTS

Isolation based on IFN-γ production provides a T-cell population with a mixture of early, central memory, and effector memory T cells, high expansion potential, and effective cytokine production. Selection of T cells with Ag-specific expression of IL-2 or TNF-α, however, results in a T-cell population with reduced proliferation and lower effector potential after expansion.

CONCLUSION

We conclude that the exclusive secretion of IFN-γ in the human antiviral T-cell responses preferentially leads to higher repopulation capacities of antiviral T cells, compared to IL-2 or TNF-α secreting T-cell populations.

The time is now: moving toward virus-specific T cells after allogeneic hematopoietic stem cell transplantation as the standard of care

Adoptive immunotherapy-in particular, T-cell therapy-has recently emerged as a useful strategy with the potential to overcome many of the limitations of antiviral drugs for the treatment of viral complications after hematopietic stem cell transplantation. In this review, we briefly summarize the current methods for virus-specific T-cell isolation or selection and we report results from clinical trials that have used these techniques, focusing specifically on the strategies aimed to broaden the application of this technology.

Will post-transplantation cell therapies for pediatric patients become standard of care?

Although allogeneic hematopoietic stem cell transplantation (HSCT) is a curative approach for many pediatric patients with hematologic malignancies and some nonmalignant disorders, some critical obstacles remain to be overcome, including relapse, engraftment failure, graft-versus-host disease (GVHD), and infection. Harnessing the immune system to induce a graft-versus-tumor effect or rapidly restore antiviral immunity through the use of donor lymphocyte infusion (DLI) has been remarkably successful in some settings. Unfortunately, however, the responses to DLI can be variable, and GVHD is common. Thus, manipulations to minimize GVHD while restoring antiviral immunity and enhancing the graft-versus-tumor effect are needed to improve outcomes after allogeneic HSCT. Cellular therapies, defined as treatment modalities in which hematopoietic or nonhematopoietic cells are used as therapeutic agents, offer this promise for improving outcomes post-HSCT. This review presents an overview of the field for pediatric cell therapies in the transplant setting and discusses how we can broaden applicability beyond phase I.

A registry of HLA-typed donors for production of virus-specific CD4 and CD8 T lymphocytes for adoptive reconstitution of immune-compromised patients

BACKGROUND

Virus-specific CD4 and CD8 T lymphocytes from HLA-matched donors are effective for treatment and prophylaxis of viral infections in immune-compromised recipients of hematopoietic stem cell transplant recipients. Adoptive immune reconstitution is based on selection of specific T cells or on generation of specific T-cell lines from the graft donor. Unfortunately, the graft donor is not always immune to the relevant pathogen or the graft donor may not be available (registry-derived or cord blood donors).

STUDY DESIGN AND METHODS

Since the possibility of using T cells from a third-party subject is now established, we screened potential donors for T-cell responses against cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus, the viruses most frequently targeted by adoptive immune reconstitution. Specific T-cell responses against viral antigens were analyzed in 111 donors using a miniaturized interferon-γ release assay.

RESULTS

Responders to CMV were 64%, to EBV 40%, and to adenovirus 51%. Simultaneous responders to the three viruses were 49%. CMV-specific CD4 and CD8 T-cell lines could be generated from 11 of 12 donors defined as positive responders according to the T-cell assay.

CONCLUSIONS

These data demonstrate that a large fraction of volunteers can be recruited in a donor registry for selection or expansion of virus specific T cells and that our T-cell assay predicts the donors' ability to give rise to established T-cell lines endowed with proliferative potential and effector function for adoptive immune reconstitution.

IL-12-secreting CD19-targeted cord blood-derived T cells for the immunotherapy of B-cell acute lymphoblastic leukemia

Disease relapse or progression is a major cause of death following umbilical cord blood (UCB) transplantation (UCBT) in patients with high-risk, relapsed or refractory acute lymphoblastic leukemia (ALL). Adoptive transfer of donor-derived T cells modified to express a tumor-targeted chimeric antigen receptor (CAR) may eradicate persistent disease after transplantation. Such therapy has not been available to UCBT recipients, however, due to the low numbers of available UCB T cells and the limited capacity for ex vivo expansion of cytolytic cells. We have developed a novel strategy to expand UCB T cells to clinically relevant numbers in the context of exogenous cytokines. UCB-derived T cells cultured with interleukin (IL)-12 and IL-15 generated >150-fold expansion with a unique central memory/effector phenotype. Moreover, UCB T cells were modified to both express the CD19-specific CAR, 1928z, and secrete IL-12. 1928z/IL-12 UCB T cells retained a central memory-effector phenotype and had increased antitumor efficacy in vitro. Furthermore, adoptive transfer of 1928z/IL-12 UCB T cells resulted in significantly enhanced survival of CD19(+) tumor-bearing SCID-Beige mice. Clinical translation of CAR-modified UCB T cells could augment the graft-versus-leukemia effect after UCBT and thus further improve disease-free survival of transplant patients with B-cell ALL.

The effects of age and latent cytomegalovirus infection on the redeployment of CD8+ T cell subsets in response to acute exercise in humans

Dynamic exercise evokes a rapid redeployment of cytotoxic T cell subsets with high expression of β2 adrenergic receptors, presumably to enhance immunosurveillance during acute stress. As this response is affected by age and infection history, this study examined latent CMV infection as a potential confounder to age-related differences in blood CD8+ T-cell responses to exercise. Healthy young (n=16) and older (n=16) humans counterbalanced by CMV IgG serostatus (positive or negative) exercised for 30-min at ∼80% peak cycling power. Those with CMV redeployed ∼2-times more CD8+ T-cells and ∼6-times more KLRG1+/CD28- and CD45RA+/CCR7- CD8+ subsets than non-infected exercisers. Seronegative older exercisers had an impaired redeployment of total CD8+ T-cells, CD45RA+/CCR7+ and KLRG1-/CD28+ CD8+ subsets compared to young. Redeployed CD8+ T-cell numbers were similar between infected young and old. CMVpp65 specific CD8+ cells in HLA/A2(∗) subjects increased ∼2.7-fold after exercise, a response that was driven by the KLRG1+/CD28-/CD8+ subset. Stimulating PBMCs before and after exercise with CMVpp65 and CMV IE-1 antigens and overlapping peptide pools revealed a 2.1 and 4.4-fold increases in CMVpp65 and CMV IE-1 IFN-γ secreting cells respectively. The breadth of the T cell response was maintained after exercise with the magnitude of the response being amplified across the entire epitope repertoire. To conclude, latent CMV infection overrides age-related impairments in CD8+ T-cell redeployment with exercise. We also show for the first time that many T-cells redeployed with exercise are specific to CMVpp65 and CMV IE-1 antigens, have broad epitope specificity, and are mostly of a high-differentiated effector memory phenotype.

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

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

Controlling cytomegalovirus: helping the immune system take the lead

Cytomegalovirus, of the Herpesviridae family, has evolved alongside humans for thousands of years with an intricate balance of latency, immune evasion, and transmission. While upwards of 70% of humans have evidence of CMV infection, the majority of healthy people show little to no clinical symptoms of primary infection and CMV disease is rarely observed during persistent infection in immunocompetent hosts. Despite the fact that the majority of infected individuals are asymptomatic, immunologically, CMV hijacks the immune system by infecting and remaining latent in antigen-presenting cells that occasionally reactivate subclinically and present antigen to T cells, eventually causing the inflation of CMV-specific T cells until they can compromise up to 10% of the entire T cell repertoire. Because of this impact on the immune system, as well as its importance in fields such as stem cell and organ transplant, the relationship between CMV and the immune response has been studied in depth. Here we provide a review of many of these studies and insights into how CMV-specific T cells are currently being used therapeutically.

Impact of T cell selection methods in the success of clinical adoptive immunotherapy

Chemotherapy and/or radiotherapy regular regimens used for conditioning of recipients of hematopoietic stem cell transplantation (SCT) induce a period of transient profound immunosuppression. The onset of a competent immunological response, such as the appearance of viral-specific T cells, is associated with a lower incidence of viral infections after haematopoietic transplantation. The rapid development of immunodominant peptide virus screening together with advances in the design of genetic and non-genetic viral- and tumoural-specific cellular selection strategies have opened new strategies for cellular immunotherapy in oncologic recipients who are highly sensitive to viral infections. However, the rapid development of cellular immunotherapy in SCT has disclosed the role of the T cell selection method in the modulation of functional cell activity and of in vivo secondary effects triggered following immunotherapy.

Low rate of infusional toxicity after expanded cord blood transplantation

BACKGROUND AIMS

Umbilical cord blood (CB) is used with increasing frequency to restore hematopoiesis in patients with bone marrow transplant who lack a suitable human leukocyte antigen-matched donor. CB transplantation is limited by low cell doses and delays in neutrophil and platelet engraftment. CB progenitors expanded ex vivo before transplantation provide more rapid hematopoietic and immune reconstitution as well as less engraftment failure compared with unmanipulated CB. However, the safety of infusing double and ex vivo-expanded CB has not been systematically examined.

METHODS

We reviewed the immediate adverse events (AE) associated with the infusion of CB occurring within 24 hours in 137 patients enrolled in clinical CB transplant trials at the MD Anderson Cancer Center from February 2004 to May 2010. All patients received an unmanipulated CB unit followed by infusion of a second unmanipulated CB unit or a second CB unit expanded ex vivo with the use of cytokines in a liquid culture system or in mesenchymal stromal cell co-cultures.

RESULTS

A total of three grade 2 and two grade 3 infusion reactions occurred within 24 hours of CB transplantation. This resulted in an AE rate of 3.7%. The majority of AEs manifested as signs of hypertension. No association with patient age, sex, disease status, premedication, ABO compatibility or total infusion volume was observed. In summary, the incidence of infusion-related toxicities in patients who receive unmanipulated and ex vivo-expanded double CB transplantation is low.

CONCLUSIONS

We conclude that the infusion of unmanipulated followed by expanded CB products is a safe procedure associated with a low probability of inducing severe reactions.

Accelerating immune reconstitution after hematopoietic stem cell transplantation

Viral infections remain a significant cause of morbidity and mortality after hematopoietic stem cell transplantation. Pharmacologic agents are effective against some pathogens, but they are costly and can be associated with significant toxicities. Thus, many groups have investigated adoptive T-cell transfer as a means of hastening immune reconstitution and preventing and treating viral infections. This review discusses the immunotherapeutic strategies that have been explored.

Adoptive immunotherapy for cancer or viruses

Adoptive immunotherapy, or the infusion of lymphocytes, is a promising approach for the treatment of cancer and certain chronic viral infections. The application of the principles of synthetic biology to enhance T cell function has resulted in substantial increases in clinical efficacy. The primary challenge to the field is to identify tumor-specific targets to avoid off-tumor, on-target toxicity. Given recent advances in efficacy in numerous pilot trials, the next steps in clinical development will require multicenter trials to establish adoptive immunotherapy as a mainstream technology.

Immunologic special forces: anti-pathogen cytotoxic T-lymphocyte immunotherapy following hematopoietic stem cell transplantation

Anti-pathogen adoptive T-cell immunotherapy has been proven to be highly effective in preventing or controlling viral infections following hematopoietic stem cell transplantation. Recent advances in manufacturing protocols allow an increased number of targeted pathogens, eliminate the need for viral transduction, broaden the potential donor pool to include pathogen-naïve sources, and reduce the time requirement for production. Early studies suggest that anti-fungal immunotherapy may also have clinical benefit. Future advances include further broadening of the pathogens that can be targeted and development of T-cells with resistance to pharmacologic immunosuppression.

T-cell therapy for viral infections

Viral infections remain a major cause of morbidity in patients with immunodeficiency, such as recipients of hemopoietic stem cell transplantation. Adoptive transfer of donor-derived virus-specific cytotoxic T lymphocytes is a strategy to restore virus-specific immunity to prevent or treat viral diseases and has been tested in the clinical setting for more than 20 years. Several different groups have used expanded virus-specific T-cell products specific for one or multiple viruses to both reconstitute antiviral immunity after transplantation and to treat active viral infections. Response rates are encouraging, although resistance has been seen when the infused cell population has had restricted specificity or has targeted antigens expressed in donor-infected but not virally infected recipient cells. The goal of current trials is to make this approach more broadly applicable using more rapidly available products from the donor, such as directly selected or briefly expanded cells or closely matched banked cells.

CD4 CTL: living up to the challenge

During thymic development, thymocytes expressing a T cell receptor consisting of an alpha and beta chain (TCRαβ), commit to either the cytotoxic- or T helper-lineage fate. This lineage dichotomy is controlled by key transcription factors, including the T helper (Th) lineage master regulator, the Th-inducing BTB/POZ domain-containing Kruppel-like zinc-finger transcription factor, ThPOK, (formally cKrox or Zfp67; encoded by Zbtb7b), which suppresses the cytolytic program in major histocompatibility complex (MHC) class II-restricted CD4(+) thymocytes and the Runt related transcription factor 3 (Runx3), which counteracts ThPOK in MHC class I restricted precursor cells and promotes the lineage commitment of CD8αβ(+) cytolytic T lymphocytes (CTL). ThPOK continues to repress the CTL gene program in mature CD4(+) T cells, even as they differentiate into effector Th cell subsets. The Th cell fate however is not fixed and two recent studies showed that mature, antigen-stimulated CD4(+) T cells have the flexibility to terminate the expression of ThPOK and functionally reprogram to cytotoxic effector cells. This unexpected plasticity of CD4(+) T cells results in the post-thymic termination of the Th lineage fate and the functional differentiation of distinct MHC class II-restricted CD4(+) CTL. The recognition of CD4 CTL as a defined separate subset of effector cells and the identification of the mechanisms and factors that drive their reprogramming finally create new opportunities to explore the physiological relevance of these effector cells in vivo and to determine their pivotal roles in both, protective immunity as well as in immune-related pathology.

Dissecting graft-versus-leukemia from graft-versus-host-disease using novel strategies

The intrinsic anti-leukemic effect of allogeneic hematopoietic cell transplantation (HCT) is dependent on genetic disparity between donor and recipient, intimately associated with graft-versus-host disease (GVHD), and mediated by lymphocytes contained in or derived from the donor hematopoietic cell graft. Three decades of intense effort have not identified clinical strategies that can reliably separate the graft-versus-leukemia (GVL) effect from the alloimmune reaction that drives clinical GVHD. For patients who require HCT and for whom two or more human leukocyte antigen (HLA)-A, -B, -C, and -DRB1-matched donor candidates can be identified, consideration of donor and recipient genotype at additional genetic loci both within and outside the major histocompatibility complex may offer the possibility of selecting the donor [candidate(s)] that poses the lowest probability of GVHD and the highest probability of a potent GVL effect. Strategies for engineering conventional donor lymphocyte infusion also hold promise for prevention or improved treatment of post-transplant relapse. The brightest prospects for selectively enhancing the anti-leukemic efficacy of allogeneic HCT, however, are likely to be interventions that are designed to enhance specific antitumor immunity via vaccination or adoptive cell transfer, rather than those that attempt to exploit donor alloreactivity against the host. Adoptive transfer of donor-derived T cells genetically modified for tumor-specific reactivity, in particular, has the potential to transform the practice of allogeneic HCT by selectively enhancing antitumor immunity without causing GVHD.

Mixed functional characteristics correlating with TCR-ligand koff -rate of MHC-tetramer reactive T cells within the naive T-cell repertoire

The low frequency of antigen-specific naïve T cells has challenged numerous laboratories to develop various techniques to study the naïve T-cell repertoire. Here, we combine the generation of naïve repertoire-derived antigen-specific T-cell lines based on MHC-tetramer staining and magnetic-bead enrichment with in-depth functional assessment of the isolated T cells. Cytomegalovirus (CMV) specific T-cell lines were generated from seronegative individuals. Generated T-cell lines consisted of a variety of immunodominant CMV-epitope-specific oligoclonal T-cell populations restricted to various HLA-molecules (HLA-A1, A2, B7, B8, and B40), and the functional and structural avidity of the CMV-specific T cells was studied. Although all CMV-specific T cells were isolated based on their reactivity toward a specific peptide-MHC complex, we observed a large variation in the functional avidity of the MHC-tetramer positive T-cell populations, which correlated with the structural avidity measured by the recently developed Streptamer koff -rate assay. Our data demonstrate that MHC-tetramer staining is not always predictive for specific T-cell reactivity, and challenge the sole use of MHC-tetramers as an indication of the peripheral T-cell repertoire, independent of the analysis of functional activity or structural avidity parameters.

Highlights of the third International Conference on Immunotherapy in Pediatric Oncology

The third International Conference on Immunotherapy in Pediatric Oncology was held in Frankfurt/Main, Germany, October 1-2, 2012. Major topics of the conference included (i) cellular therapies using antigen-specific and gene-modified T cells for targeting leukemia and pediatric solid tumors; (ii) overcoming hurdles and barriers with regard to immunogenicity, immune escape, and the role of tumor microenvironment; (iii) vaccine strategies and antigen presentation; (iv) haploidentical transplantation and innate immunity; (v) the role of immune cells in allogeneic transplantation; and (vi) current antibody/immunoconjugate approaches for the treatment of pediatric malignancies. During the past decade, major advances have been made in improving the efficacy of these modalities and regulatory hurdles have been taken. Nevertheless, there is still a long way to go to fully exploit the potential of immunotherapeutic strategies to improve the cure of children and adolescents with malignancies. This and future meetings will support new collaborations and insights for further translational and clinical immunotherapy studies.

Generation of tumor antigen-specific T cell lines from pediatric patients with acute lymphoblastic leukemia--implications for immunotherapy

PURPOSE

Although modern cure rates for childhood acute lymphoblastic leukemia (ALL) exceed 80%, the outlook remains poor in patients with high-risk disease and those who relapse, especially when allogeneic hematopoietic stem cell transplantation is not feasible. Strategies to improve outcome and prevent relapse are therefore required. Immunotherapy with antigen-specific T cells can have antileukemic activity without the toxicities seen with intensive chemotherapy, and therefore represents an attractive strategy to improve the outcome of high-risk patients with ALL. We explored the feasibility of generating tumor antigen-specific T cells ex vivo from the peripheral blood of 50 patients with ALL [26 National Cancer Institute (NCI) high-risk and 24 standard-risk] receiving maintenance therapy.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells were stimulated with autologous dendritic cells pulsed with complete peptide libraries of WT1, Survivin, MAGE-A3, and PRAME, antigens frequently expressed on ALL blasts.

RESULTS

T-cell lines were successfully expanded from all patients, despite low lymphocyte counts and irrespective of NCI risk group. Antigen-specificity was observed in more than 50% of patients after the initial stimulation and increased to more than 90% after three stimulations as assessed in IFN-γ-enzyme-linked immunospot (ELISpot) and (51)Cr-release assays. Moreover, tumor-specific responses were observed by reduction of autologous leukemia blasts in short- and long-term coculture experiments.

CONCLUSION

This study supports the use of immunotherapy with adoptively transferred autologous tumor antigen-specific T cells to prevent relapse and improve the prognosis of patients with high-risk ALL.

The immunogenicity of virus-derived 2A sequences in immunocompetent individuals

Genetic engineering of T cells for adoptive immunotherapy in cancer patients has shown significant promise. To ensure optimal antitumor activity and safety, the simultaneous expression of multiple genes is frequently required, and short viral-derived 2A sequences are increasingly preferred for this purpose. Concerns exist, however, that these virus-derived sequences may induce unwanted immune responses, and thus diminish persistence of the gene-modified cells after adoptive transfer. Whereas such responses were absent in immunocompromised recipients, potential immunogenicity in immunocompetent individuals remains a concern. We now address whether ex vivo T cell responses can be elicited against the most widely used 2A sequences (2A-Thosea asigna virus (TAV) or 2A-equine rhinitis virus (ERAV), specifically) in immunocompetent individuals. We used a potent ex vivo culture system previously validated to induce T cell responses even against weakly immunogenic antigens. Of the sixteen donors tested, only five released very low levels of interferon-γ in response to 2A-TAV peptide mixtures (single peptide specificity in three donors, adjacent self-antigen peptide specificity in one donor and nonspecific reactivity in one donor). None of them produced cytotoxic activity or responded to 2A-ERAV. These results suggest that exposure to viral-derived 2A sequences is unlikely to produce unwanted T cell responses in immunocompetent individuals and further supports their continued use for studies of human gene therapy.

New strategies in cord blood cells transplantation

For patients lacking a human leucocyte antigen-matched donor, umbilical cord blood (UCB) is an ideal, alternative source of haematopoietic stem cells (HSCs) for transplantation purposes. UCB has many advantages over bone marrow or peripheral blood taken from volunteer donors. UCB is also an important source of other stem cells, including endothelial progenitors, mesenchymal stem cells, very small embryonic/epiblast-like (VSEL) stem cells, and unrestricted somatic stem cells, which are potentially suitable for regenerative medicine. However, a significant clinical problem is that the number of HSCs in one cord-blood unit is not enough for an adult transplantation. The development of new approaches including use of multiple donors, ex vivo expansion, increasing efficiency of homing and engraftment, retrieving more cells from the placenta and cord blood is of crucial importance for the delayed engraftment after UCB transplantation. In the future, UCB will emerge as a source of cells for cellular therapies associated with tissue repair and regeneration.

Modeling dendritic cell vaccination for influenza prophylaxis: potential applications for niche populations

BACKGROUND

Cancer patients can exhibit negligible responses to prophylactic vaccinations, including influenza vaccination. To help address this issue, we developed in vitro and in vivo models of dendritic cell (DC) immunotherapy for the prevention of influenza virus infection.

METHODS

Human cord blood (CB)-derived or mouse splenocyte-derived DCs were loaded with purified recombinant hemagglutinin (rHA). T-cell responses to HA-loaded CB-derived DCs were determined by ELISpot. Protective efficacy was determined by vaccination of BALB/c mice with a single injection of 10(6) autologous DCs. DC migration to peripheral lymphoid organs was verified by carboxyfluorescein succinimidyl ester staining, and HA-specific antibody titers were determined by enzyme-linked immunosorbent assay. Mice were then challenged intranasally with BALB/c-adapted A/New Caledonia influenza virus derived from four consecutive lung pool passages. Antigen-presenting cell (APC) dysfunction was modeled using the MAFIA transgenic system, in which the Csf1r promoter conditionally drives AP20178-inducible Fas.

RESULTS

CB-derived human DCs were able to generate de novo T-cell responses against rHA, as determined by a system of rigorous controls. Mice vaccinated intraperitoneally developed HA titers detectable at serum dilutions of >1:1000. HA seroconverters survived virus challenge, whereas unvaccinated controls and vaccinated nonseroconverters lost weight and died. Furthermore, use of a model of APC-specific immunosuppression revealed that DC vaccination could generate HA-specific antibody titers under conditions in which protein vaccination could not.

CONCLUSIONS

The model demonstrates that DC immunotherapy for the prevention of influenza is feasible, and studies are underway to determine whether populations of immunosuppressed individuals might ultimately benefit from the procedure.

Generation of multi-leukemia antigen-specific T cells to enhance the graft-versus-leukemia effect after allogeneic stem cell transplant

Adoptive immunotherapy with ex vivo expanded T cells is a promising approach to prevent or treat leukemia. Myeloid leukemias express tumor-associated antigens (TAA) that induce antigen-specific cytotoxic T lymphocyte (CTL) responses in healthy individuals. We explored the feasibility of generating TAA-specific CTLs from stem cell donors of patients with myeloid leukemia to enhance the graft-versus-leukemia effect after stem cell transplantation. CTL lines were manufactured from peripheral blood of 10 healthy donors by stimulation with 15mer peptide libraries of five TAA (proteinase 3 (Pr3), preferentially expressed antigen in melanoma, Wilms tumor gene 1 (WT1), human neutrophil elastase (NE) and melanoma-associated antigen A3) known to be expressed in myeloid leukemias. All CTL lines responded to the mix of five TAA and were multi-specific as assessed by interferon-γ enzyme-linked immunospot. Although donors showed individual patterns of antigen recognition, all responded comparably to the TAAmix. Immunogenic peptides of WT1, Pr3 or NE could be identified by epitope mapping in all donor CTL lines. In vitro experiments showed recognition of partially human leukocyte antigen (HLA)-matched myeloid leukemia blasts. These findings support the development of a single clinical grade multi-tumor antigen-specific T-cell product from the stem cell source, capable of broad reactivity against myeloid malignancies for use in donor-recipient pairs without limitation to a certain HLA-type.

Cytomegalovirus pneumonia in hematopoietic stem cell recipients

Cytomegalovirus (CMV) is a frequently encountered infection following hematopoietic cell transplantation, and tissue invasive pneumonia is a dreaded complication of the virus in this population. In this review of CMV pneumonia, we address epidemiology, pathogenesis, diagnostics, current therapy, and strategies to prevent the development of CMV. We also review emerging treatment and prevention options for this challenging disease.

Umbilical cord blood transplantation: a maturing technology

The use of umbilical cord blood (CB) as a source of hematopoietic progenitor cells for patients with high-risk hematologic disorders receiving allogeneic hematopoietic cell transplantations (HCTs) has increased significantly. Single-institution and registry studies have shown a decreased relapse rate and an increased transplantation-related mortality rate with similar overall survival rates after allogeneic HCT with CB compared with other donor sources. The transplantation of double CB units has overcome the dose limitation inherent in a single CB unit and thus has markedly extended the use of CB to larger children and adults. Similarly, the use of reduced intensity conditioning in the CB transplantation setting has allowed the treatment of older patients who would be unable to tolerate the myeloablative regimens used in the original CB transplantation protocols.

Adenovirus viremia and disease: comparison of T cell-depleted and conventional hematopoietic stem cell transplantation recipients from a single institution

Adenovirus (ADV) is an important cause of viral mortality in hematopoietic stem cell transplantation (HSCT). Recipients of T cell-depleted (TCD) HSCT are at increased risk for viral infections. We compared the rates and outcomes of ADV viremia and disease between TCD and conventional (CONV) HSCT at our institution. This was an observational study of 624 adult and pediatric recipients of myeloablative HSCT at Memorial Sloan-Kettering Cancer Center between January 1, 2006, and March 11, 2011. Viral cultures and ADV PCR were ordered as clinically indicated. ADV viremia by quantitative PCR assay was defined as 1 or more positive values ≥1,000 copies/mL or 2 or more consecutive positive values. Competing-risk regression analyses were used to identify predictors for ADV viremia. ADV viremia at 1 year after HSCT occurred in 8% of TCD HSCT recipients and in 4.0% of CONV HSCT recipients (P = .041). Among the TCD recipients, ADV viremia was seen in 15% of children, compared with 5% of adults (P = .008). Young age (hazard ratio [HR], 3.0; P < .001) and acute graft-versus-host disease (GVHD) (HR, 3.2; P = .001) were identified as risk factors for ADV viremia. ADV viremia was predictive of mortality (HR, 6.0; P < .001). ADV disease developed in 3.5% of TCD HSCT recipients and in 0.4% of CONV HSCT recipients (P = .022), with an attributable mortality of 27%. Among TCD HSCY recipients, grade II to IV GVHD was a risk factor for ADV disease (HR, 13; P < .001), but age was not. More than 90% of the cases of ADV disease involved a viral load of ≥10,000 copies/mL. Rates of ADV disease were 10-fold greater in TCD HSCT recipients compared with CONV HSCT recipients, predominantly in patients who developed acute GVHD. The benefit of preemptive therapy for an ADV viral load ≥10,000 copies/mL for preventing ADV disease in TCD HSCT recipients should be evaluated in prospective clinical trials.

Cytotoxic T lymphocytes for the treatment of viral infections and posttransplant lymphoproliferative disorders in transplant recipients

PURPOSE OF REVIEW

The continuous and successful expansion of organ transplants is unfortunately associated with increased incidence of severe opportunistic viral infections and Epstein-Barr virus (EBV)-related lymphomas secondary to immunosuppression. Here, we review the strengths and limitations of T-cell-based strategies used to treat viral infections in immunocompromised individuals.

RECENT FINDINGS

While current antiviral drugs are often suboptimal because of associated toxicities, a promising approach in the management of infections with viruses like cytomegalovirus (CMV), adenovirus (AdV) and EBV is the adoptive transfer of T cells targeting these viruses that can be directly isolated from the peripheral blood of the donor or expanded ex vivo prior to infusions in patients.

SUMMARY

T-cell-based immunotherapies are now being included in the clinical practice of transplant recipients to prevent and treat infections and complications associated with CMV, AdV and EBV. Improvement of current limitations will enable the extension of these approaches to all patients at risk and to other clinically relevant viruses and pathogens that are emerging as significant complications for immunocompromised patients.

Reconstitution of protective immune responses against cytomegalovirus and varicella zoster virus does not require disease development in pediatric recipients of umbilical cord blood transplantation

CMV and varicella zoster virus (VZV) are significant causes of morbidity and mortality following umbilical cord blood transplantation (UCBT). However, the kinetics of reconstitution and protective potential of antiviral cell-mediated immune responses following UCBT remain poorly characterized. In this study, the reconstitution of CMV- and VZV-specific T cell responses was assessed using IFN-γ ELISPOT in 28 children who underwent UCBT to treat hematological or inherited disorders. Barely detectable in the first 3 mo posttransplantation, CMV- and VZV-specific T cell responses were observed in 30.4% and 40.3% of study subjects after 36 mo of follow-up. Four of five CMV-seropositive subjects developed detectable levels of circulating CMV DNA (DNAemia), and 5 of 17 VZV-seropositive patients experienced herpes zoster during the posttransplant period. Four CMV-seronegative subjects developed IFN-γ responses against CMV, and four subjects developed a VZV-specific IFN-γ response without clinical signs of infection. No CMV- or VZV-related events were observed in study subjects following the development of CMV- or VZV-specific responses > 150 spot-forming units/10(6) PBMCs, consistent with T cell-mediated protection. Finally, famciclovir prophylaxis did not strictly prevent the reconstitution of the VZV-specific T cell repertoire, because the frequency of T cells producing IFN-γ in response to VZV Ags reached levels consistent with protection in two nonzoster subjects. Monitoring of CMV- and VZV-specific cell-mediated immunity could inform immunocompetence and guide the initiation and cessation of antiherpetic prophylaxis in UCBT recipients.

Therapeutic strategies for the prevention and treatment of cytomegalovirus infection

INTRODUCTION

CMV remains a significant cause of morbidity and mortality in immunosuppressed patients, particularly following allogeneic haematopoietic transplantation. This reflects the inability of depressed host immunity to contain viral replication, principally through the loss of T-cell function. There is a clear rationale for the restoration of CMV-specific immunity using adoptive T-cell immunotherapy.

AREAS COVERED

This review analyses current treatment strategies for prophylaxis and preemptive treatment of CMV with a particular focus on patients following allogeneic haematopoietic transplantation. The main emphasis of this review is the role of adoptive T-cell therapy, particularly some of the newer direct selection technologies that allow the rapid generation of a GMP-compliant cellular product. Relevant studies were selected from PubMed. Search terms: allogeneic transplant, cytomegalovirus, multidrug-resistant virus, adoptive T-cell therapy.

EXPERT OPINION

A number of early studies showed that T-cell therapies can be delivered safely and are efficacious. However, they relied on culture techniques that make wider application difficult. Newer direct selection techniques have allowed production of cellular products more rapidly, cheaply, and to GMP standards. Clinical trials will help define the role of these cellular products, which have the potential to alter our entire approach to the treatment of CMV infection.

Transmaternal cell flow leads to antigen-experienced cord blood

Umbilical cord blood (UCB) is used for HSCT. It is known that UCB can comprise Ag-specific T cells. Here we question whether solely transmaternal cell flow may immunize UCB. Twenty-three female UCB samples were collected from healthy mothers and analyzed for minor histocompatibility Ag HY-specific responses. Forty-two of 104 tetramer(pos) T-cell clones, isolated from 16 of 17 UCB samples, showed male-specific lysis in vitro. Male microchimerism was present in 6 of 12 UCB samples analyzed. In conclusion, female UCB comprises HY-specific cytotoxic T cells. The immunization is presumably caused by transmaternal cell flow of male microchimerism present in the mother. The presence of immune cells in UCB that are not directed against maternal foreign Ags is remarkable and may explain the reported clinical observation of improved HSCT outcome with younger sibling donors.

Expanding cytotoxic T lymphocytes from umbilical cord blood that target cytomegalovirus, Epstein-Barr virus, and adenovirus

Virus infections after stem cell transplantation are among the most common causes of death, especially after cord blood (CB) transplantation (CBT) where the CB does not contain appreciable numbers of virus-experienced T cells which can protect the recipient from infection. We and others have shown that virus-specific CTL generated from seropositive donors and infused to the recipient are safe and protective. However, until recently, virus-specific T cells could not be generated from cord blood, likely due to the absence of virus-specific memory T cells. In an effort to better mimic the in vivo priming conditions of naïve T cells, we established a method that used CB-derived dendritic cells (DC) transduced with an adenoviral vector (Ad5f35pp65) containing the immunodominant CMV antigen pp65, hence driving T cell specificity towards CMV and adenovirus. At initiation, we use these matured DCs as well as CB-derived T cells in the presence of the cytokines IL-7, IL-12, and IL-15. At the second stimulation we used EBV-transformed B cells, or EBV-LCL, which express both latent and lytic EBV antigens. Ad5f35pp65-transduced EBV-LCL are used to stimulate the T cells in the presence of IL-15 at the second stimulation. Subsequent stimulations use Ad5f35pp65-transduced EBV-LCL and IL-2. From 50x10(6) CB mononuclear cells we are able to generate upwards of 150 x 10(6) virus-specific T cells that lyse antigen-pulsed targets and release cytokines in response to antigenic stimulation. These cells were manufactured in a GMP-compliant manner using only the 20% fraction of a fractionated cord blood unit and have been translated for clinical use.

Immunotherapy highlights from the 2011 meeting of the American Society of Hematology

The world's largest hematology society, the American Society for Hematology, meets annually, gathering physicians, scientists, administrators, medical students, graduate students, allied health professionals and exhibitors. The meeting this year was held in San Diego, CA, USA, and included a plethora of basic, translational and clinical research.

Natural and adoptive T-cell immunity against herpes family viruses after allogeneic hematopoietic stem cell transplantation

Reactivated infections with herpes family-related cytomegalovirus, Epstein-Barr virus and varicella zoster virus are serious and sometimes life-threatening complications for patients undergoing allogeneic hematopoietic stem cell transplantation. The pathogenesis of these infections critically involves the slow and inefficient recovery of antiviral T-cell immunity after transplantation. Although efficient drugs to decrease viral load during this vulnerable period have been developed, long-term control of herpes viruses and protection from associated diseases require the sufficient reconstitution of virus-specific memory T cells. To heal the deficiency by immunotherapeutic means, numerous research groups have developed antiviral vaccines and strategies based on the adoptive transfer of virus-specific T cells. This article summarizes the substantial progress made in this field during the past two decades and gives future perspectives about challenges that need to be addressed before antigen-specific immunotherapy against herpes family viruses can be implemented in general clinical practice.

Concise review: expanding roles for hematopoietic cellular therapy and the blood transfusion services

Hematopoietic stem cells (HSCs) have remained at the forefront of stem cell research for the past 50 years, since the therapeutic potential of bone marrow transplantation was realized. Uniquely, among stem and progenitor cells, research progress has been made in parallel between the laboratory benchtop and hospital bedside during this period. Integral to this work has been the role of the transfusion medicine services in the collection, storage, and processing of HSCs. The next decade promises to bring further developments: with new fields of cellular therapies, stem cell vaccination, and stem cell drug testing opening up. This article summarizes exciting areas of research concerning the behavior and potential clinical applications of HSCs. For the purposes of clarity, we describe in turn the trafficking and transfer of HSCs; ex vivo expansion of HSC units from different sources; and finally, applications of specifically selected subsets of hematopoietic cells and their progeny.

Early CD3 peripheral blood chimerism predicts the long-term engrafting unit following myeloablative double-cord blood transplantation

After double-cord blood transplantation, long-term hematopoietic dominance of a single-cord blood donor graft is established in the majority of patients; however, the mechanism behind this observation remains largely unknown. Beginning at day 7 posttransplantation, we prospectively measured weekly lineage-specific peripheral blood donor chimerisms in patients undergoing myeloablative double-cord blood transplantation to evaluate whether the degree of early donor contribution to specific lineage(s) would predict the long-term engrafting unit. Our results demonstrate that the donor unit with higher CD3 chimerism at day 7 became the dominant engrafting unit in 26 of 31 evaluable patients (P = .0002) and in 34 of 34 evaluable patients at day 14 (P < .0001). Similarly, higher donor unit CD33 chimerism was associated with dominant engraftment in 8 of 8 (day 7) and in 31 of 32 (day 14) evaluable patients. No statistically significant correlation between the dominant unit and order of infusion, infused total nucleated cells, CD34, or CD3 cell doses, unit viability, or HLA disparity was observed. The correlation of higher early posttransplantation donor CD3 peripheral blood chimerism with the dominant unit suggests a rapid immune-mediated response as a primary mechanism of action for long-term single-donor dominance. This finding may have clinical implications for early selection of the winning unit after double-cord blood transplantation and for novel cord blood manipulation strategies.

Immunology in the clinic review series; focus on cancer: double trouble for tumours: bi-functional and redirected T cells as effective cancer immunotherapies

Cancer is one of the most important pathological conditions facing mankind in the 21st century, and is likely to become the most important cause of death as improvements continue in health, diet and life expectancy. The immune response is responsible for controlling nascent cancer through immunosurveillance. If tumours escape this control, they can develop into clinical cancer. Although surgery and chemo- or radiotherapy have improved survival rates significantly, there is a drive to reharness immune responses to treat disease. As T cells are one of the key immune cells in controlling cancer, research is under way to enhance their function and improve tumour targeting. This can be achieved by transduction with tumour-specific T cell receptor (TCR) or chimaeric antigen receptors (CAR) to generate redirected T cells. Virus-specific cells can also be transduced with TCR or CAR to create bi-functional T cells with specificity for both virus and tumour. In this review we outline the development and optimization of redirected and bi-functional T cells, and outline the results from current clinical trials using these cells. From this we discuss the challenges involved in generating effective anti-tumour responses while avoiding concomitant damage to normal tissues and organs.

Improving T-cell therapy for relapsed EBV-negative Hodgkin lymphoma by targeting upregulated MAGE-A4

PURPOSE

Patients with Hodgkin lymphoma (HL) relapsing after hematopoietic stem cell transplant have limited options for long-term cure. We have shown that infused cytotoxic T cells (CTL) targeting Epstein Barr virus (EBV)-derived proteins induced complete remissions in EBV(+) HL patients. A limitation of this approach is that up to 70% of relapsed HL tumors are EBV-negative. For these patients, an alternative is to target the cancer/testis antigen MAGE-A4 present in EBV antigen-negative HL tumors. Furthermore, epigenetic modification by clinically available demethylating agents can enhance MAGE-A4 expression in previously MAGE-negative tumors.

EXPERIMENTAL DESIGN

We explored the feasibility of combining adoptive T cell therapy with epigenetic modification of tumor antigen expression. We further characterized MAGE-A4-specific T-cell phenotype and function, and examined the effects of the epigenetic modifying drug decitabine on these T cells.

RESULTS

Cytotoxic T cells were generated specifically recognizing MAGE-A4 expressed by autologous HL targets and tumor cell lines. Decitabine-previously shown to increase tumor antigen expression in HL-did not compromise MAGE-A4-specific T-cell phenotype and function. In patients treated with decitabine, expanded MAGE-A4-specific T cells had a broader antitumor T cell repertoire, consistent with increased antigen stimulation in vivo.

CONCLUSIONS

Adoptive transfer of MAGE-A4-specific T cells, combined with epigenetic modifying drugs to increase expression of the protein, may improve treatment of relapsed HL.

Expansion of T cells targeting multiple antigens of cytomegalovirus, Epstein-Barr virus and adenovirus to provide broad antiviral specificity after stem cell transplantation

BACKGROUND AIMS

Hematopoietic stem cell transplant (HSCT) is the treatment of choice for a proportion of patients with hematologic malignancies as well as for non-malignant diseases. However, viral infections, particularly Epstein-Barr virus (EBV), cytomegalovirus (CMV) and adenovirus (Ad), remain problematic after transplant despite the use of antiviral drugs. We have shown that cytotoxic T lymphocytes (CTL) generated against CMV-pp65, EBV and Ad antigens in a single culture are capable of controlling infections with all three viruses after HSCT. Although pp65-specific CTL have proved efficacious for the control of CMV infection, several reports highlight the importance of targeting additional CMV antigens.

METHODS

To expand multivirus-specific T cells with activity against both CMV-pp65 and CMV-IE-1, peripheral blood mononuclear cells (PBMC) were transduced with the adenoviral vector (Ad5f35-IE-1-I-pp65). After 9-12 days the CTL were restimulated with autologous EBV-transformed B cells transduced with the same Ad vector.

RESULTS

After 18 days in culture nine CTL lines expanded from less than 1.5 × 10(7) PBMC to a mean of 6.1 × 10(7) T cells that recognized CMV antigens pp65 [median 273 spot-forming cells (SFC), range 47-995] and IE-1 (median 154 SFC, range 11-505), the Ad antigens hexon (median 153 SFC, range 26-465) and penton (median 37 SFC, range 1-353), as well as EBV lymphoblastoid cell lines (median 55 SFC, range 9-301). Importantly, the T cells recognized at least two antigens per virus and lysed virus peptide-pulsed targets.

CONCLUSIONS

CTL that target at least two antigens each of CMV, EBV and Ad should have clinical benefit with broad coverage of all three viruses and enhanced control of CMV infections compared with current protocols.