T-cell therapy after hematopoietic stem cell transplantation

Iron overload as a risk factor for poor graft function following allogeneic hematopoietic stem cell transplantation

Hematological malignancies are increasingly treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Unfortunately, iron overload is a frequent adverse effect of allo-HSCT and is associated with poor prognosis. In the present study, we investigated hematopoiesis in iron-overloaded mice and elucidated the effects of iron overload on the bone marrow (BM) microenvironment. Iron-overloaded BALB/C mice were generated by injecting 20 mg/mL saccharated iron oxide intraperitoneally. Hematoxylin-eosin staining was performed to evaluate the effects of an iron overload in mice. BM cells obtained from C57BL/6 mice were transplanted into irradiated BALB/C mice (whole-body irradiation of 4 Gy, twice with a 4-hours interval) by tail vein injection. Two weeks after allo-HSCT, the hematopoietic reconstitution capacity was evaluated in recipients by colony-forming assays. Histopathological examinations showed brown-stained granular deposits, irregularly arranged lymphocytes in the liver tissues, and blue-stained blocks in the BM collected from mice received injections of high-dose saccharated iron oxide (20 mg/mL). Iron-overloaded mice showed more platelets, higher-hemoglobin (HGB) concentration, fewer granulocyte-macrophage colony-forming units (CFU-GM), erythrocyte colony-forming units (CFU-E), and mixed granulocyte/erythrocyte/monocyte/megakaryocyte colony-forming units (CFU-mix) than healthy mice. Iron-overloaded recipients presented with reduced erythrocytes and HGB concentration in peripheral blood, along with decreased marrow stroma cells, CFU-GM, CFU-E, and CFU-mix relative to healthy recipients. Taken together, our findings demonstrate that iron overload might alter the number of red blood cells after transplantation in mice by destroying the BM microenvironment, thereby affecting the recovery of BM hematopoietic function.

New strategies of DLI in the management of relapse of hematological malignancies after allogeneic hematopoietic SCT

DLI is an effective strategy for patients with recurrent hematological malignancies after allogeneic hematopoietic SCT (allo-HSCT). DLI has been widely applied to boost the graft vs tumor (GVT) or GVL effects. However, given the potentially severe complications associated with conventional DLI and transient GVL effect, new strategies for DLI are emerging. In this review, we have discussed the recent important studies on DLI as a prophylactic or therapeutic modality for relapsed hematological disorders after allo-HSCT. The strategies to separate GVL from GVHD have also been discussed. Leukemia-targeting therapy and lymphodepletion combined with DLI, and prophylactic DLI after allo-HSCT are often employed for patients with high risk of relapse, which has been reviewed as well. In addition, we have also discussed the issues on DLI to be further addressed, such as the doses, timing and frequency of DLI in different clinical settings, leukemic antigen-specific DLI as well as how to augment GVL effect while attenuating GVHD.

Sirolimus-based graft-versus-host disease prophylaxis promotes the in vivo expansion of regulatory T cells and permits peripheral blood stem cell transplantation from haploidentical donors

Hematopoietic stem cell transplantation (HSCT) from human leukocyte antigen (HLA) haploidentical family donors is a promising therapeutic option for high-risk hematologic malignancies. Here we explored in 121 patients, mostly with advanced stage diseases, a sirolimus-based, calcineurin-inhibitor-free prophylaxis of graft-versus-host disease (GvHD) to allow the infusion of unmanipulated peripheral blood stem cell (PBSC) grafts from partially HLA-matched family donors (TrRaMM study, Eudract 2007-5477-54). Conditioning regimen was based on treosulfan and fludarabine, and GvHD prophylaxis on antithymocyte globulin Fresenius (ATG-F), rituximab and oral administration of sirolimus and mycophenolate. Neutrophil and platelet engraftment occurred in median at 17 and 19 days after HSCT, respectively, and full donor chimerism was documented in patients' bone marrow since the first post-transplant evaluation. T-cell immune reconstitution was rapid, and high frequencies of circulating functional T-regulatory cells (Treg) were documented during sirolimus prophylaxis. Incidence of acute GvHD grade II-IV was 35%, and occurrence and severity correlated negatively with Treg frequency. Chronic GvHD incidence was 47%. At 3 years after HSCT, transpant-related mortality was 31%, relapse incidence 48% and overall survival 25%. In conclusion, GvHD prophylaxis with sirolimus-mycophenolate-ATG-F-rituximab promotes a rapid immune reconstitution skewed toward Tregs, allowing the infusion of unmanipulated haploidentical PBSC grafts.

Augmented adenovirus transduction of murine T lymphocytes utilizing a bi-specific protein targeting murine interleukin 2 receptor

Adenoviruses are currently used in a variety of bench and bedside applications. However, their employment in gene delivery to lymphocyte lineages is hampered by the lack of coxsackie virus and adenovirus receptor (CAR) on the cell surface. Exploitation of an alternative receptor on the surface of T lymphocytes can allow for utilization of adenovirus in a variety of T lymphocyte-based diseases and therapies. Here, we describe how resistance to infection can be overcome by the utilization of a bi-specific fusion protein, soluble CAR murine interleukin 2 (sCAR-mIL-2), that retargets adenovirus to the murine IL-2 receptor (IL-2R). Infection of a murine T-cell line, CTLL-2, with a sCAR-mIL-2/Adenovirus conjugate provided a ninefold increase in both green fluorescence protein-positive cells and luciferase expression. In addition, this increase in infection was also seen in isolated primary murine T lymphocytes. In this context, the sCAR-mIL-2 adapter provided a fourfold gene transduction increase in activated primary murine T lymphocytes. Our results show that recombinant sCAR-mIL-2 fusion protein promotes IL-2R-targeted gene transfer to murine T lymphocytes and that alternative targeting can abrogate their native resistance to infection.

Enhanced transduction and replication of RGD-fiber modified adenovirus in primary T cells

Background

Adenoviruses are often used as vehicles to mediate gene delivery for therapeutic purposes, but their research scope in hematological cells remains limited due to a narrow choice of host cells that express the adenoviral receptor (CAR). T cells, which are attractive targets for gene therapy of numerous diseases, remain resistant to adenoviral infection because of the absence of CAR expression. Here, we demonstrate that this resistance can be overcome when murine or human T cells are transduced with an adenovirus incorporating the RGD-fiber modification (Ad-RGD).

Methodology/Principal Finding

A luciferase-expressing replication-deficient Ad-RGD infected 3-fold higher number of activated primary T cells than an adenovirus lacking the RGD-fiber modification in vitro. Infection with replication-competent Ad-RGD virus also caused increased cell cycling, higher E1A copy number and enriched hexon antigen expression in both human and murine T cells. Transduction with oncolytic Ad-RGD also resulted in higher titers of progeny virus and enhanced the killing of T cells. In vivo, 35–45% of splenic T cells were transduced by Ad-RGD.

Conclusions

Collectively, our results prove that a fiber modified Ad-RGD successfully transduces and replicates in primary T cells of both murine and human origin.

Concomitant tumor and minor histocompatibility antigen-specific immunity initiate rejection and maintain remission from established spontaneous solid tumors

Nonmyeloablative hematopoietic cell transplantation can cure patients with hematologic malignancies but has reported limited success against solid tumors. This is possibly because of profound peripheral tolerance mechanisms and/or suboptimal tumor recognition by effector T lymphocytes. We report that in mice developing spontaneous prostate cancer, nonmyeloablative minor histocompatibility mismatched hematopoietic stem cell transplantation, and donor lymphocyte infusion of unmanipulated lymphocytes combined with posttransplant tumor-specific vaccination circumvents tumor-specific tolerance, allowing acute tumor rejection and the establishment of protective immunosurveillance. Although donor-derived tumor-specific T cells readily differentiated into effector cells and infiltrated the tumor soon after infusion, they were alone insufficient for tumor eradication, which instead required the concomitance of minor histocompatibiltiy antigen-specific CD8(+) T-cell responses. The establishment of protective immunosurveillance was best induced by posttransplant tumor-specific vaccination. Hence, these results provide the proof of principle that tumor-specific T-cell responses have to be harnessed together with minor histocompatibility responses and sustained by posttransplant tumor-specific vaccination to improve the efficacy of allotransplantion for the cure of solid tumors.

T-cell-based therapies for malignancy and infection in childhood

One major advance in T-cell-based immunotherapy in the last 20 years has been the molecular definition of numerous viral and tumor antigens. Adoptive T-cell transfer has shown definite clinical benefit in the prophylaxis and treatment of viral infections that develop in pediatric patients after allogeneic transplant and in posttransplant lymphoproliferative disease associated with the Epstein-Barr virus. Developing adoptive T-cell therapies for other malignancies presents additional challenges. This article describes the recent advances in T-cell-based therapies for malignancy and infection in childhood and strategies to enhance the effector functions of T cells and optimize the cellular product, including gene modification and modulation of the host environment.

Loss of mismatched HLA in leukemia after stem-cell transplantation

BACKGROUND

Transplantation of hematopoietic stem cells from partially matched family donors is a promising therapy for patients who have a hematologic cancer and are at high risk for relapse. The donor T-cell infusions associated with such transplantation can promote post-transplantation immune reconstitution and control residual disease.

METHODS

We identified 43 patients who underwent haploidentical transplantation and infusion of donor T cells for acute myeloid leukemia or myelodysplastic syndrome and conducted post-transplantation studies that included morphologic examination of bone marrow, assessment of hematopoietic chimerism with the use of short-tandem-repeat amplification, and HLA typing. The genomic rearrangements in mutant variants of leukemia were studied with the use of genomic HLA typing, microsatellite mapping, and single-nucleotide-polymorphism arrays. The post-transplantation immune responses against the original cells and the mutated leukemic cells were analyzed with the use of mixed lymphocyte cultures.

RESULTS

In 5 of 17 patients with leukemia relapse after haploidentical transplantation and infusion of donor T cells, we identified mutant variants of the original leukemic cells. In the mutant leukemic cells, the HLA haplotype that differed from the donor's haplotype had been lost because of acquired uniparental disomy of chromosome 6p. T cells from the donor and the patient after transplantation did not recognize the mutant leukemic cells, whereas the original leukemic cells taken at the time of diagnosis were efficiently recognized and killed.

CONCLUSIONS

After transplantation of haploidentical hematopoietic stem cells and infusion of donor T cells, leukemic cells can escape from the donor's antileukemic T cells through the loss of the mismatched HLA haplotype. This event leads to relapse.

Programming tumor-reactive effector memory CD8+ T cells in vitro obviates the requirement for in vivo vaccination

Naive and memory CD8(+) T cells can undergo programmed activation and expansion in response to a short T-cell receptor stimulus, but the extent to which in vitro programming can qualitatively substitute for an in vivo antigen stimulation remains unknown. We show that self-/tumor-reactive effector memory CD8(+) T cells (T(EM)) programmed in vitro either with peptide-pulsed antigen-presenting cells or plate-bound anti-CD3/anti-CD28 embark on a highly stereotyped response of in vivo clonal expansion and tumor destruction nearly identical to that of vaccine-stimulated T(EM) cells. This programmed response was associated with an interval of antigen-independent interferon-gamma (IFN-gamma) release that facilitated the dynamic expression of the major histocompatibility complex class I restriction element H-2D(b) on responding tumor cells, leading to recognition and subsequent tumor lysis. Delaying cell transfer for more than 24 hours after stimulation or infusion of cells deficient in IFN-gamma entirely abrogated the benefit of the programmed response, whereas transfer of cells unable to respond to IFN-gamma had no detriment to antitumor immunity. These findings extend the phenomenon of a programmable effector response to memory CD8(+) T cells and have major implications for the design of current adoptive-cell transfer trials.

Allogeneic Haematopoietic Stem Cell Transplantation without a Matched Sibling Donor: Current Options and Future Potential

Introduction: Allogeneic haematopoietic stem cell transplantation (HSCT) has been used to treat a variety of malignant and non-malignant diseases. For patients who do not have a matched sibling donor or a optimally matched unrelated donor (MUD) for transplantation, other graft sources have been used, including mismatched haploidentical related donors and umbilical cord blood (CB). Materials and Methods: A literature review and comparison of HSCT with MUD, haploidentical donors and CB donors was performed. The relative value of MUD and CB donor recruitment was calculated based on search-hit ratios of respective registries. Results: The choice of haematopoietic stem cell (HSC) source for transplantation remains difficult, and is dependent on disease stage, the centre’s experience, HLA-matching and cell dose. It remains a lengthy procedure to identify and procure HSC from an acceptably matched unrelated donor, which may lead to disease progression in some patients. In these cases, alternatives such as haploidentical transplants or CB transplants can offer a chance for timely treatment. Although results of haploidentical transplant have improved in some centres, this approach is less successful in many other centres embarking on this transplant technique. However, there is the prospect of availability of HSC donors for almost every patient if the challenges of haploidentical HSCT can be overcome. CB transplantation has been established as a valid alternative for patients who cannot identify a suitably matched unrelated donor quickly enough. Some centres even prefer CB as a HSC source to unrelated donor bone marrow (BM) for paediatric patients. Conclusion: Further increases in the size and diversity of CB inventories may realise the potential of every patient having access to at least a 5/6 matched CB unit of adequate cell dose (70-fold relative value for each CB unit banked versus each BM donor recruited). Prospective comparisons of MUD, CB, and haploidentical HSCT are needed to validate the optimal HSC source for transplant in specific diseases. Key words: Cord blood banking, HLA matching

Adoptive transfer of allogeneic tumor-specific T cells mediates effective regression of large tumors across major histocompatibility barriers

Graft-versus-tumor effects can be achieved after allogeneic bone marrow transplantation in patients with malignancies of the kidney or hematopoietic system but are often accompanied by severe graft-versus-host-disease (GVHD). We sought to maximize graft-versus-tumor while minimizing GVHD using tumor-specific allogeneic effector T cells rather than open-repertoire T cells. We transferred allogeneic CD8(+) pmel-1 or CD4(+) TRP-1 T cells specific for the melanoma-associated antigens, glycoprotein 100 (gp100) and tyrosinase-related protein-1 (TRP-1), respectively, into B16-melanoma-bearing mice. Mice receiving a preparative regimen of nonmyeloablating (5 Gy) total body irradiation experienced the rapid rejection of tumor-specific allogeneic lymphocytes with no impact on tumor growth. However, when mice were given more intense total body irradiation conditioning regimens combined with autologous bone marrow transplantation, adoptively transferred allogeneic tumor-specific T lymphocytes persisted at detectable levels for several weeks and mediated significant regression of large, vascularized tumors. We found that the risk of GVHD was low when tumor-specific T cells were transferred and significant toxicity was observed only when substantial numbers of open repertoire allogeneic naive T cells were mixed with the tumor-specific lymphocytes. Taken together, these data indicate that the use of tumor-specific allogeneic CD8(+) T cells or CD4(+) can result in significant antitumor effects in the absence of measurable GVHD.

Immunotherapy for myeloid leukemias: current status and future directions

Myeloid leukemias, although a heterogeneous group of hematopoietic stem cell neoplasms, are arguably among the most suited for active specific immunotherapy. Nevertheless, clinical development of myeloid leukemia vaccine lagged behind similar approaches in other solid and hematological malignancies. The recent identification of apparently specific leukemia antigens and advances in understanding the fundamentals of tumor immunology have helped initiate a number of early phase clinical studies evaluating the safety and clinical efficacy of this approach. Here we review the recently identified and characterized putative leukemia antigens, the main vaccination strategies employed by most investigators and the results of clinical studies of immunotherapy of myeloid leukemias. Although these studies are early and often difficult to interpret, they offer evidence that effective immunity to leukemia could be induced following vaccination, and that clinical benefit can sometimes be observed, thus setting the stage for future development of this strategy and in the combinatorial approaches to treatment of myeloid leukemias that incorporate immunotherapy.