Adoptive immunotherapy with donor lymphocyte infusions after allogeneic hematopoietic cell transplantation following nonmyeloablative conditioning

Immunotherapy for neuroblastoma by hematopoietic cell transplantation and post-transplant immunomodulation

Neuroblastoma represents a relatively common childhood tumor that imposes therapeutic difficulties. High risk neuroblastoma patients have poor prognosis, display limited response to radiochemotherapy and may be treated by hematopoietic cell transplantation. Allogeneic and haploidentical transplants have the distinct advantage of reinstitution of immune surveillance, reinforced by antigenic barriers. The key factors favorable to ignition of potent anti-tumor reactions are transition to adaptive immunity, recovery from lymphopenia and removal of inhibitory signals that inactivate immune cells at the local and systemic levels. Post-transplant immunomodulation may further foster anti-tumor reactivity, with positive but transient impact of infusions of lymphocytes and natural killer cells both from the donor, the recipient or third party. The most promising approaches include introduction of antigen-presenting cells in early post-transplant stages and neutralization of inhibitory signals. Further studies will likely shed light on the nature and actions of suppressor factors within tumor stroma and at the systemic level.

Newly diagnosed multiple myeloma: making sense of the menu

The development of new drugs and subsequent novel combinations for the treatment of newly diagnosed multiple myeloma (NDMM) has resulted in a plethora of treatment options that can make the choice of initial induction therapy a challenge. A greater understanding of both patient- and disease-specific factors can provide a personalized approach to help design a treatment course. Historically, the choice of an induction regimen has been tethered to an initial impression of transplant eligibility at the time of diagnosis. As more effective and better-tolerated induction regimens have emerged, there has been increasing overlap in the induction strategies used for all patients with NDMM, which increasingly provide the ultimate goal of deep and durable remissions. The current treatment options and strategies for the management of NDMM are evaluated using the best available data to provide a rationale for these decisions.

T cell receptor engineering of primary NK cells to therapeutically target tumors and tumor immune evasion

BACKGROUND

T cell receptor (TCR)-engineered cells can be powerful tools in the treatment of malignancies. However, tumor resistance by Human Leukocyte antigen (HLA) class I downregulation can negatively impact the success of any TCR-mediated cell therapy. Allogeneic natural killer (NK) cells have demonstrated efficacy and safety against malignancies without inducing graft-versus-host-disease, highlighting the feasibility for an 'off the shelf' cellular therapeutic. Furthermore, primary NK cells can target tumors using a broad array of intrinsic activation mechanisms. In this study, we combined the antitumor effector functions of NK cells with TCR engineering (NK-TCR), creating a novel therapeutic strategy to avoid TCR-associated immune resistance.

METHODS

BOB1, is a transcription factor highly expressed in all healthy and malignant B cell lineages, including multiple myeloma (MM). Expression of an HLA-B*07:02 restricted BOB1-specifc TCR in peripheral blood-derived NK cells was achieved following a two-step retroviral transduction protocol. NK-TCR was then compared with TCR-negative NK cells and CD8-T cells expressing the same TCR for effector function against HLA-B*07:02+ B-cell derived lymphoblastoid cell lines (B-LCL), B-cell acute lymphoblastic leukemia and MM cell lines in vitro and in vivo.

RESULTS

Firstly, TCR could be reproducibly expressed in NK cells isolated from the peripheral blood of multiple healthy donors generating pure NK-TCR cell products. Secondly, NK-TCR demonstrated antigen-specific effector functions against malignancies which were previously resistant to NK-mediated lysis and enhanced NK efficacy in vivo using a preclinical xenograft model of MM. Moreover, antigen-specific cytotoxicity and cytokine production of NK-TCR was comparable to CD8 T cells expressing the same TCR. Finally, in a model of HLA-class I loss, tumor cells with B2M KO were lysed by NK-TCR in an NK-mediated manner but were resistant to T-cell based killing.

CONCLUSION

NK-TCR cell therapy enhances NK cell efficacy against tumors through additional TCR-mediated lysis. Furthermore, the dual efficacy of NK-TCR permits the specific targeting of tumors and the associated TCR-associated immune resistance, making NK-TCR a unique cellular therapeutic.

Mixed T cell lineage chimerism in acute leukemia/MDS using pre-emptive donor lymphocyte infusion strategy-Is it prognostic?-a single-center retrospective study

Pre-emptive DLI (pDLI) is an effective strategy in lowering the risk of relapse without significantly increasing the risk of graft-versus-host disease (GVHD) in the case of T cell lineage mixed chimerism (MC) post allogeneic transplant in hematological malignancies. Many patients, however, fail to receive timely pDLI and have dismal outcomes, which are not taken into consideration. We compared long-term outcomes of 106 patients having T cell MC after day 60 and undergoing allogeneic stem cell allograft for acute leukemia from an unrelated donor (UD), with 111 patients having complete chimerism (CC). Fifty-three (56%) patients received prophylactic pDLI. Thirty-six patients (67%) had a response (RR), 17 (33%) had no response (NR), and fifty-two (54%) did not receive any pDLI (ND). OS was better in MC group as compared to CC (54% vs 43%, p = 0.04), mainly due to reduction in NRM (14% vs 25%, p = 0.05), and all grade acute and chronic GVHD. Within the MC group, response to pDLI was the only significant factor predicting OS, DFS, and relapses with NR and ND having unfavorable outcomes as compared to RR (p = 0.001). T cell MC in patients undergoing UD allografts with alemtuzumab is no longer an adverse prognostic factor, as compared to patients having CC, after timely implementation of pDLI.

Reversal of Low Donor Chimerism after Hematopoietic Cell Transplantation Using Pentostatin and Donor Lymphocyte Infusion: A Prospective Phase II Multicenter Trial

In a multicenter, prospective, phase II study we evaluated the safety and efficacy of pentostatin followed by donor lymphocyte infusion (DLI) in patients with low donor Tcell chimerism after allogeneic hematopoietic cell transplantation (HCT). Thirty-six patients with low donor blood CD3 chimerism were enrolled in this study. Thirty-five patients received a total of 41 DLIs after a dose of pentostatin, and 1 patient received pentostatin only. Median donor CD3 chimerism prompting the initiation of pentostatin and DLI was 28% (range, 5% to 47%). Responses (defined by increases in donor CD3 chimerism ≥10% maintained to day 56 post-DLI) were seen in 16 patients (44.4%) with a median rise in CD3 donor chimerism to 64% (range, 48% to 100%). There was a trend for better responses among 21 patients who received first treatment within 100 days after transplant (57% response rate) compared with15 patients who received first treatment more than 100 days after HCT (27% response rate, P = .07). Fourteen patients (39%) developed grades II to IV acute graft-versus-host disease (GVHD) at a median of 10 days (range, 0 to 83) after DLI. Ten patients (28%) developed extensive chronic GVHD. Seventeen patients (47%) developed new grade 4 cytopenias after DLI. There was no difference in relapse between nonresponders and responders. Twenty-eight patients (78%) died, most (n = 21) because of relapse. Five of 16 responders (31%) are alive, all disease-free, at a median of 60 months (range, 21 to 132) after DLI. Six of 20 nonresponders (30%) are alive at a median of 47 months (range, 16 to 100) after DLI, 3 in complete remission. Pentostatin and DLI had acceptable toxicity and appeared to increase low donor CD3 chimerism after HCT but had no impact on mortality.

Donor T-cell responses and disease progression patterns of multiple myeloma

Donor T-cells transferred after allogeneic stem cell transplantation (alloSCT) can result in long-term disease control in myeloma by the graft-versus-myeloma (GvM) effect. However, T-cell therapy may show differential effectiveness against bone marrow (BM) infiltration and focal myeloma lesions resulting in different control and progression patterns. Outcomes of 43 myeloma patients who underwent T-cell-depleted alloSCT with scheduled donor lymphocyte infusion (DLI) were analyzed with respect to diffuse BM infiltration and focal progression. For comparison, 12 patients for whom a donor search was started but no alloSCT was performed, were analyzed. After DLI, complete disappearance of myeloma cells in BM occurred in 86% of evaluable patients. The probabilities of BM progression-free survival (PFS) at 2 years after start of donor search, alloSCT and DLI, were 17% (95% confidence interval 0-38%), 51% (36-66%), and 62% (44-80%) respectively. In contrast, the probabilities of focal PFS at 2 years after start of donor search, alloSCT and DLI, were 17% (0-38%), 30% (17-44%) and 28% (11-44%), respectively. Donor-derived T-cell responses effectively reduce BM infiltration, but not focal progression in myeloma, illustrating potent immunological responses in BM with only limited effect of T-cells on focal lesions.

Possible Impact of Cytomegalovirus-Specific CD8+ T Cells on Immune Reconstitution and Conversion to Complete Donor Chimerism after Allogeneic Stem Cell Transplantation

Complete donor chimerism is strongly associated with complete remission after allogeneic stem cell transplantation (allo-SCT) in patients with hematologic malignancies. Donor-derived allo-immune responses eliminate the residual host hematopoiesis and thereby mediate the conversion to complete donor chimerism. Recently, cytomegalovirus (CMV) reactivation was described to enhance overall T cell reconstitution, to increase graft-versus-host disease incidence, and to reduce the leukemia relapse risk. However, the link between CMV and allo-immune responses is still unclear. Here, we studied the relationship between CMV-specific immunity, overall T cell reconstitution, and residual host chimerism in 106 CMV-seropositive patients transplanted after reduced-intensity conditioning including antithymocyte globulin. In accordance with previous reports, the recovery of CMV-specific cytotoxic T cells (CMV-CTLs) was more frequent in CMV-seropositive recipients (R) transplanted from CMV-seropositive than from seronegative donors (D). However, once CMV-CTLs were detectable, the reconstitution of CMV-specific CTLs was comparable in CMV R+/D- and R+/D+ patients. CD3⁺ and CD8⁺ T cell reconstitution was significantly faster in patients with CMV-CTLs than in patients without CMV-CTLs both in the CMV R+/D- and R+/D+ setting. Moreover, CMV-CTL numbers correlated with CD3⁺ and CD8⁺ T cell numbers in both settings. Finally, presence of CMV-CTLs was associated with low host chimerism levels 3 months after allo-SCT. In conclusion, our data provide a first indication that CMV-CTLs in CMV-seropositive patients might trigger the reconstitution of T cells and allo-immune responses reflected by the conversion to complete donor chimerism.

Prolonged Survival of Subcutaneous Allogeneic Islet Graft by Donor Chimerism without Immunosuppressive Treatment

The aim of this study was to investigate whether tolerance-induced protection of islets in the renal subcapsular space can also prevent subcutaneous allogeneic islets from being rejected. We used bone marrow stem cells from C57BL/6 (H2^b) mice to construct donor chimerism in conditioned diabetic BALB/c (H2^d) mice and investigated the effect of donor chimerism on engraftment and survival of subcutaneously transplanted allogeneic islets in streptozotocin-induced diabetic mice. We also studied the anti-inflammatory effect of mesenchymal stem cell on islet engraftment. Full but not low-grade or no donor chimerism was associated with successful engraftment of allogeneic islets and restoration of normoglycemia in the treated diabetic mice. The temporary hyperglycemia was 11 ± 1 versus 19 ± 5 days (p < 0.05) for the mice with full donor chimerism with transplanted islets in the renal subcapsular space versus the subcutaneous space, respectively. Cotransplantation of mesenchymal stem cell did not enhance alloislet engraftment. Full multilineage donor chimerism was associated with a higher transient expansion of CD11b⁺ and Gr-1⁺ myeloid progenitor cells and effector memory CD4 and CD8 T cells. In conclusion, full donor chimerism protected both renal subcapsular and subcutaneous allogeneic islets in this rodent transplantation model.

Efficacy of host-dendritic cell vaccinations with or without minor histocompatibility antigen loading, combined with donor lymphocyte infusion in multiple myeloma patients

Donor lymphocyte infusions (DLI) can induce durable remissions in multiple myeloma (MM) patients, but this occurs rather infrequently. As the graft-versus-tumor (GvT) effect of DLI depends on the presence of host-dendritic cells (DCs), we tested in a phase I/II trial whether the efficacy of DLI could be improved by simultaneous vaccination with host-DCs. We also analyzed the possibility of further improving the GvT effect by loading the DCs with peptides of mismatched hematopoietic cell-specific minor histocompatibility antigens (mHags). Fifteen MM patients not responding to a first DLI were included. Eleven patients could be treated with a second equivalent dose DLI combined with DC vaccinations, generated from host monocytes (moDC). For four patients, the DC products did not meet the quality criteria. In four of the treated patients the DCs were loaded with host mHag peptides. Toxicity was limited and no acute GvHD occurred. Most patients developed objective anti-host T-cell responses and in one patient a distinct mHag-specific T-cell response accompanied a temporary clinical response. These findings confirm that DLI combined with host-DC vaccination, either unloaded or loaded with mHag peptides, is feasible, safe and capable of inducing host-specific T-cell responses. The limited clinical effects may be improved by developing more immunogenic DC products or by combining this therapy with immune potentiating modalities like checkpoint inhibitors.

Strategies for improving the efficacy of donor lymphocyte infusion following stem cell transplantation

Donor lymphocyte infusion (DLI) is an effective immunotherapeutic approach with significant activity in the treatment and prevention of relapse after allogeneic stem cell transplantation. DLI is associated with significant toxicity mainly due to graft-versus-host disease. Moreover, DLI does not produce durable responses in aggressive malignancies like acute leukemia. Improvement in DLI efficacy requires dissociation of graft-versus-leukemia effect from graft-versus-host disease. Minor histocompatibility antigens with tissue restriction and leukemia or tumor-associated antigens represent ideal antigenic targets. A brief overview of the existing methods of DLI administration is the topic of this article. T cells transduced with genes encoding for T-cell receptors with reactivity against minor histocompatibility antigens or leukemia-associated antigens is a promising option.

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.

High-Dose Sirolimus and Immune-Selective Pentostatin plus Cyclophosphamide Conditioning Yields Stable Mixed Chimerism and Insufficient Graft-versus-Tumor Responses

PURPOSE

We hypothesized that lymphoid-selective host conditioning and subsequent adoptive transfer of sirolimus-resistant allogeneic T cells (T-Rapa), when combined with high-dose sirolimus drug therapy in vivo, would safely achieve antitumor effects while avoiding GVHD.

EXPERIMENTAL DESIGN

Patients (n = 10) with metastatic renal cell carcinoma (RCC) were accrued because this disease is relatively refractory to high-dose conditioning yet may respond to high-dose sirolimus. A 21-day outpatient regimen of weekly pentostatin (P; 4 mg/m(2)/dose) combined with daily, dose-adjusted cyclophosphamide (C; ≤200 mg/d) was designed to deplete and suppress host T cells. After PC conditioning, patients received matched sibling, T-cell-replete peripheral blood stem cell allografts, and high-dose sirolimus (serum trough target, 20-30 ng/mL). To augment graft-versus-tumor (GVT) effects, multiple T-Rapa donor lymphocyte infusions (DLI) were administered (days 0, 14, and 45 posttransplant), and sirolimus was discontinued early (day 60 posttransplant).

RESULTS

PC conditioning depleted host T cells without neutropenia or infection and facilitated donor engraftment (10 of 10 cases). High-dose sirolimus therapy inhibited multiple T-Rapa DLI, as evidenced by stable mixed donor/host chimerism. No antitumor responses were detected by RECIST criteria and no significant classical acute GVHD was observed.

CONCLUSIONS

Immune-selective PC conditioning represents a new approach to safely achieve alloengraftment without neutropenia. However, allogeneic T cells generated ex vivo in sirolimus are not resistant to the tolerance-inducing effects of in vivo sirolimus drug therapy, thereby cautioning against use of this intervention in patients with refractory cancer.

Possible role of minor h antigens in the persistence of donor chimerism after stem cell transplantation; relevance for sustained leukemia remission

Persistent complete donor chimerism is an important clinical indicator for remissions of hematological malignancies after HLA-matched allogeneic stem cell transplantation (SCT). However, the mechanisms mediating the persistence of complete donor chimerism are poorly understood. The frequent coincidence of complete donor chimerism with graft-versus-leukemia effects and graft-versus-host disease suggests that immune responses against minor histocompatibility antigens (mHags) are playing an important role in suppressing the host hematopoiesis after allogeneic SCT. Here, we investigated a possible relationship between donor immune responses against the hematopoiesis-restricted mHag HA-1 and the long-term kinetics of host hematopoietic chimerism in a cohort of 10 patients after allogeneic HLA-matched, HA-1 mismatched SCT. Functional HA-1 specific CTLs (HA-1 CTLs) were detectable in 6/10 patients lysing host-type hematopoietic cells in vitro. Presence of HA-1 CTLs in the peripheral blood coincided with low host hematopoiesis levels quantified by highly sensitive mHag specific PCR. Additionally, co-incubation of host type CD34⁺ cells with HA-1 CTLs isolated after allogeneic SCT prevented progenitor and cobblestone area forming cell growth in vitro and human hematopoietic engraftment in immunodeficient mice. Conversely, absence or loss of HA-1 CTLs mostly coincided with high host hematopoiesis levels and/or relapse. In summary, in this first study, presence of HA-1 CTLs paralleled low host hematopoiesis levels. This coincidence might be supported by the capacity of HA-1 CTLs isolated after allogeneic SCT to specifically eliminate host type hematopoietic stem/progenitor cells. Additional studies involving multiple mismatched mHags in more patients are required to confirm this novel characteristic of mHag CTLs as factor for the persistence of complete donor chimerism and leukemia remission after allogeneic SCT.

Reduced-intensity conditioned allogeneic SCT in adults with AML

AML is currently the most common indication for reduced-intensity conditioned (RIC) allo-SCT. Reduced-intensity regimens allow a potent GVL response to occur with minimized treatment-related toxicity in patients of older age or with comorbidities that preclude the use of myeloablative conditioning. Whether RIC SCT is appropriate for younger and more standard risk patients is not well defined and the field is changing rapidly; a prospective randomized trial of myeloablative vs RIC (BMT-CTN 0901) was recently closed when early results indicated better outcomes for myeloablative regimens. However, detailed results are not available, and all patients in that study were eligible for myeloablative conditioning. RIC transplants will likely remain the standard of care as many patients with AML are not eligible for myeloablative conditioning. Recent publication of mature results from retrospective and prospective cohorts provide contemporary efficacy and toxicity data for these attenuated regimens. In addition, recent studies explore the use of alternative donors, introduce regimens that attempt to reduce toxicity without reducing intensity, and identify predictive factors that pave the way to personalized approaches. These studies paint a picture of the future of RIC transplants. Here we review the current status of RIC allogeneic SCT in AML.

Minimal residual disease before and after transplantation for childhood acute lymphoblastic leukaemia: is there any room for intervention?

Eighty-two children and adolescents who underwent allogeneic transplantation for acute lymphoblastic leukaemia in remission (period 2001-2011, median follow-up 4·9 years) had been assessed for minimal residual disease (MRD) by real-time quantitative polymerase chain reaction before and at 1, 3, 6, 9 and 12 months after transplantation. Five-year event-free survival (EFS) and cumulative incidence of relapse were 77·7% [standard error (SE) 5·7] and 11·4% (SE 4·4), respectively, for patients with pre-transplant MRD <1 × 10(-4) (68%), versus 30·8% (SE 9·1; P < 0·001) and 61·5% (SE 9·5; P < 0·001), respectively, for those with MRD ≥1 × 10(-4) (32%). Pre-transplant MRD ≥1 × 10(-4) was associated with a 9·2-fold risk of relapse [95% confidence interval (CI) 3·54-23·88; P < 0·001] compared with patients with MRD <1 × 10(-4). Patients who received additional chemotherapy pre-transplant to reduce MRD had a fivefold reduction of risk of failure (hazard ratio 0·19, CI 0·05-0·70, P = 0·01). Patients who experienced MRD positivity post-transplant did not necessarily relapse (5-year EFS 40·3%, SE 9·3), but had a 2·5-fold risk of failure (CI 1·05-5·75; P = 0·04) if any MRD was detected in the first 100 d, which increased to 7·8-fold (CI 2·2-27·78; P = 0·002) if detected after 6 months. Anticipated immunosuppression-tapering according to MRD may have improved outcome, nevertheless all patients with post-transplant MRD ≥1 × 10(-3) ultimately relapsed, regardless of immunosuppression discontinuation or donor-lymphocyte-infusion. In conclusion, MRD before transplantation had the strongest impact on relapse and MRD positivity after transplantation, mostly if detected early and at low levels, did not necessarily imply relapse. Additional intensified chemotherapy and modulation of immunosuppression may reduce relapse risk and improve ultimate outcome.

Allogeneic chimeric antigen receptor-modified cells for adoptive cell therapy of cancer

INTRODUCTION

Chimeric antigen (or antibody) receptors (CAR) are fusion proteins typically combining an antibody-derived targeting fragment with signaling domains capable of activating immune cells. Recent clinical trials have shown the tremendous potential of adoptive cell transfer (ACT) of autologous T cells engineered to express a CD19-specific CAR targeting B-cell malignancies. Building on this approach, ACT therapies employing allogeneic CAR-expressing cytotoxic cells are now being explored.

AREAS COVERED

The basic principles of CAR-ACT are introduced. The potential benefits as well as problems of using allogeneic CAR-modified cells against tumor antigens are discussed. Various approaches to allogeneic CAR therapy are presented, including donor leukocyte infusion, CAR-redirected γδ T cells and natural killer cells, strategies to avoid graft-versus-host disease, modulation of lymphocyte migration, and exploitation of graft-versus-host reactivity.

EXPERT OPINION

CAR-modified allogeneic cells have the potential to act as universal effector cells, which can be administered to any patient regardless of MHC type. Such universal effector cells could be used as an 'off-the-shelf' cell-mediated treatment for cancer.

Chemotherapy followed by modified donor lymphocyte infusion as a treatment for relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation without in vitro T-cell depletion: superior outcomes compared with chemotherapy alone and an analysis of prognostic factors

We retrospectively compared the antileukemic effects of chemotherapy alone and chemotherapy followed by modified donor lymphocyte infusion (DLI) in 82 patients with relapsed acute leukemia after haploidentical hematopoietic stem cell transplantation (HSCT) without in vitro T-cell depletion. We also investigated prognostic factors in patients receiving chemotherapy followed by modified DLI. Thirty-two patients received chemotherapy alone, and the remaining 50 patients received chemotherapy followed by modified DLI. In patients receiving chemotherapy followed by modified DLI, complete remission rate was significantly higher (64.0% vs. 12.5%, P = 0.000), the incidence of relapse was significantly lower (50.0% vs. 100.0%, P = 0.000), and disease-free survival was significantly improved (36.0% vs. 0.0%, P = 0.000) compared with patients receiving chemotherapy alone. Multivariate analysis demonstrated that patients with chronic graft-versus-host disease (GVHD) after intervention (P = 0.000) and patients receiving chemotherapy followed by modified DLI (P = 0.037) were associated with a lower relapse rate. Furthermore, in patients receiving chemotherapy followed by modified DLI, multivariate analysis demonstrated that chronic GVHD after modified DLI (P = 0.039) and duration of minimal residual disease (MRD) (-) ≥4 months after modified DLI (P = 0.001) were associated with a lower relapse rate. Our study is the first to suggest that chemotherapy followed by modified DLI is associated with stronger antileukemic effects and better survival in relapsed acute leukemia after haploidentical HSCT without in vitro T-cell depletion. Furthermore, our study suggests that lack of chronic GVHD and duration of MRD (-) <4 months after modified DLI are associated with higher relapse rates in patients receiving chemotherapy followed by modified DLI.

Promising role of reduced-toxicity hematopoietic stem cell transplantation (PART-I)

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potential curative option for many patients with hematological malignancies (HM). However, the high rate of transplantation-related mortality (TRM) restricted the use of standard myeloablative HSCT to a minority of young and fit patients. Over the past few years, it has become evident that the alloreactivity of the immunocompetent donor cells mediated anti-malignancy effects independent of the action of high dose chemoradiotherapy. The use of reduced intensity conditioning (RIC) regimens has allowed a graft-versus-malignancy (GvM) effect to be exploited in patients who were previously ineligible for HSCT on the grounds of age and comorbidity. Retrospective analysis showed that RIC has been associated with lower TRM but a higher relapse rate leading to similar intermediate term overall and progression-free survivals when compared to standard myeloablative HSCT. However, the long term antitumor effect of this approach is less well established. Prospective studies are ongoing to define which patients might most benefit from reduced toxicity stem cell transplant (RT-SCT) and which transplant protocols are suitable for the different types of HM. The advent of RT-SCT permits the delivery of a potentially curative GvM effect to the majority of patients with HM whose outcome with conventional chemotherapy would be dismal. Remaining challenges include development of effective strategies to reduce relapse rates by augmenting GvM effects without increasing toxicity.

Donor lymphocyte infusion for relapsed hematological malignancies after allogeneic hematopoietic cell transplantation: prognostic relevance of the initial CD3+ T cell dose

The impact of donor lymphocyte infusion (DLI) initial cell dose on its outcome is known in patients with chronic myeloid leukemia but limited in patients with other hematological malignancies. In this retrospective study, we evaluated the effect of initial DLI CD3(+) cell dose on graft-versus-host disease (GVHD) and overall survival after DLI given for relapse of any hematological malignancies after allogeneic hematopoietic cell transplantation (HCT) with high- or reduced-intensity conditioning. The cohort included 225 patients. Initial DLI CD3(+) cell dose per kilogram of recipient body weight was ≤ 1 × 10(7) (n = 84; group A), >1.0 to <10 × 10(7) (n = 58; group B), and ≥ 10 × 10(7) (n = 66; group C). The initial cell dose was unknown for the remaining 17 patients. Cumulative incidence rates of GVHD at 12 months after DLI were 21%, 45%, and 55% for groups A, B, and C, respectively. Multivariate analysis showed that initial DLI CD3(+) cell ≥ 10 × 10(7) dose per kilogram is associated with an increased risk of GVHD after DLI (P = .03). Moreover, an initial DLI CD3(+) cell dose of 10 × 10(7) or higher did not decrease the risk of relapse and did not improve overall survival. Thus, these results support the use of less than 10 × 10(7) CD3(+) cell per kilogram as the initial cell dose of DLI for treatment of persistent or recurrent hematological malignancy after HCT.

Donor lymphocyte infusions for relapse after allogeneic transplantation: when, if and for whom?

Donor lymphocyte infusion (DLI) using unstimulated leukapheresis is one of the most effective treatment strategies for patients with hematological malignancies; its graft-versus-leukemia effects make it especially effective in chronic myeloid leukemia patients who relapsed after allogeneic stem cell transplantation (allo-HSCT). However, DLI application is limited by the development of graft-versus-host disease and aplasia, and thus cannot be routinely applied for prophylaxis. Therefore, important questions remain to be answered, such as when, and whom to DLI? Recent advances enable DLI using allografts of granulocyte colony-stimulating factor-mobilized peripheral blood progenitor cells; allodepleted donor T cells; and infusions of donor-derived, ex vivo-expanded, CD8(+) cytotoxic T lymphocyte, which can decrease relapse and improve transplant outcomes. Preemptive immunotherapy of relapse was also introduced based on the determination of mixed chimerism and minimal residual disease. In this review, we summarize the latest developments in recent strategies that will affect future DLI efficacy - focusing on the disadvantages and advantages of each protocol for the treatment, preemptive therapy, and prophylaxis of relapse.

Reduced-intensity hematopoietic stem cell transplants for malignancies: harnessing the graft-versus-tumor effect

Allogeneic hematopoietic cell transplantation combines the power of cytotoxic chemo/radiotherapy with the ability of the new immune system to seek out and destroy tumor cells. However, administration of such myeloablative transplants is fraught with risks, some of which are related to the intensive conditioning regimens. Reductions in the intensity of the administered cytotoxic therapy have demonstrated that under some circumstances, the burden of fighting tumor and enhancing stem cell engraftment can be shouldered mostly by the transplanted immune system. Reduced intensity has allowed a potentially curative therapy for hematologic malignancies to be offered to an expanded patient population. Ongoing research seeks to enhance the safety and power of this form of allogeneic immunotherapy.

High alloreactivity of low-dose prophylactic donor lymphocyte infusion in patients with acute leukemia undergoing allogeneic hematopoietic cell transplantation with an alemtuzumab-containing conditioning regimen

The value of prophylactic donor lymphocyte infusion (pDLI) is unclear and differs among diseases and transplantation protocols. Experience with this approach in patients with acute leukemia undergoing hematopoietic cell transplantation (HCT) with an alemtuzumab-incorporating conditioning protocol is lacking. We conducted a single-center prospective study to investigate the applicability and efficacy of prophylactic donor lymphocyte infusion (pDLI) in patients with leukemia undergoing HCT with a low-dose alemtuzumab-containing conditioning regimen. Inclusion criteria were high-risk acute myelogenous leukemia, acute lymphoblastic leukemia, or increasing mixed chimerism. All patients included were tapered off of immunotherapy. Exclusion criteria were a history of ≥ grade II or active graft-versus-host disease (GVHD). Of the 56 consecutive patients who underwent HCT with an alemtuzumab-containing regimen, 15 patients (8 with acute myelogenous leukemia and 7 with acute lymphoblastic leukemia) met the study inclusion criteria and received prophylactic DLI (total of 45 infusions) from 7 sibling donors and 8 unrelated donors. The first infusion was given at a median of 162 days posttransplantation. The median number of DLIs was 3, and the median cumulative CD3(+) cell dose was 2 × 10(6)cells/kg. Six of the 8 patients (75%) who received pDLI while in mixed chimerism converted to stable, complete donor chimerism. Some 47% of DLI recipients developed GVHD (4 acute GVHD and 3 with chronic GVHD) after a median cumulative dose of 2 × 10(6) CD3(+) cells/kg. After a median follow-up of 575 days, 11 (73%) pDLI recipients were alive. All 4 deaths were due to GVHD-related causes. None of the patients who received pDLIs relapsed. Patients with leukemia who received low-dose pDLI after conditioning with alemtuzumab are at low risk for relapse; however, this approach is associated with a relatively high incidence of severe GVHD.

Novel transplant strategies in adults with acute leukemia

Autologous and allogeneic hematopoietic cell transplantation (HCT) is regularly used as a curative treatment option for patients with various disorders, including acute leukemia in adults. The past decade has witnessed dramatic improvements in the reduction of treatment-related mortality (TRM), in part attributable to improved supportive care but also due to better graft selection and donor-to-recipient matching regimens, and the emergence of reduced-intensity conditioning in place of myeloablative conditioning. Despite these advances, HCT remains plagued by the risk of relapse or failure due to graft-versus-host disease, infectious complications, and TRM. This article reviews new approaches that may improve overall patient outcome.

Preemptive immunotherapy in childhood acute myeloid leukemia for patients showing evidence of mixed chimerism after allogeneic stem cell transplantation

Previous studies have shown that children with acute myeloid leukemia (AML) who developed mixed chimerism (MC) were at high risk for relapse after allogeneic stem-cell transplantation (allo-SCT). We investigated the feasibility of intensified preemptive immunotherapy in children receiving allo-SCT for AML. Eighty-four children were registered in our trial from May 2005 to April 2009; of these, 71 fulfilled the inclusion criteria and were treated according to the study protocol. Serial and semiquantitative analyses of posttransplantation chimerism were performed. Defined immunotherapy approaches were considered in MC patients. Continuous complete chimerism (CC) was observed in 51 of 71 patients. MC was detected in 20 patients and was followed by immunotherapy in 13. Six of 13 MC patients returned to CC without toxicity and remained in long-term remission. Overall, the probability of event-free survival (pEFS) was 66% (95% confidence interval [95% CI] = 53%-76%) for all patients and 46% (95% CI = 19%-70%) in MC patients with intervention; however, this number increased to 71% (95% CI = 26%-92%) in 7 of 13 MC patients on immunotherapy who were in remission at the time of transplantation. All MC patients without intervention relapsed. These results suggest that MC is a prognostic factor for impending relapse in childhood AML, and that preemptive immunotherapy may improve the outcome in defined high-risk patients after transplantation.

Next-generation leukemia immunotherapy

Allogeneic hematopoietic cell transplantation led to the discovery of the allogeneic GVL effect, which remains the most convincing evidence that immune cells can cure cancer in humans. However, despite its great paradigmatic and clinical relevance, induction of GVL by conventional allogeneic hematopoietic cell transplantation remains a quite rudimentary form of leukemia immunotherapy. It is toxic and its efficacy is far from optimal. It is therefore sobering that since the discovery of the GVL effect 3 decades ago, the way GVL is induced and manipulated has practically not changed. Preclinical and clinical studies suggest that injection of T cells primed against a single Ag present on neoplastic cells could enhance the GVL effect without causing any GVHD. We therefore contend that Ag-targeted adoptive T-cell immunotherapy represents the future of leukemia immunotherapy, and we discuss the specific strategies that ought to be evaluated to reach this goal. Differences between these strategies hinge on 2 key elements: the nature of the target Ag and the type of Ag receptor expressed on T cells.

Adoptive T-cell therapy for B-cell malignancies

The success of allogeneic hematopoietic cell transplantation (HCT) for B-cell malignancies is evidence that these tumors can be eliminated by T lymphocytes. This has encouraged the development of specific adoptive T-cell therapy, both for augmenting the anti-tumor effect of HCT and for patients not undergoing HCT. T cells that are capable of recognizing antigens expressed on malignant B cells may be recruited from the endogenous repertoire or engineered to express tumor-targeting receptors. Critical insights into the qualities of T cells that enable their persistence and function in vivo have been derived, and obstacles to effective T-cell-mediated tumor eradication are being elucidated. These advances provide the tools to translate adoptive T-cell transfer into reliable clinical therapies.

Gene-modified T lymphocytes in the setting of hematopoietic cell transplantation: potential benefits and possible risks

INTRODUCTION

Allogeneic hematopoietic cell transplantation (HCT) is a consolidated treatment for several hematologic malignancies. Donor T lymphocytes can mediate a graft versus tumor (GVT) effect and control opportunistic infections but can also cause severe graft versus host disease (GVHD). Gene-transfer strategies are appealing tools to modulate T cell functions when infused after HCT.

AREAS COVERED

The current and potential future applications of T cell gene-transfer approaches to HCT. This review is not limited to GVHD control but covers the issues of GVT and immune reconstitution. Clinical data are used to discuss more general issues, perspectives and concerns common to gene-modification of T cells. An overview of the results and limitations emerging from clinical trials with herpes simplex virus-thymidine kinase (HSV-TK) engineered lymphocytes is provided. The review provides perspectives on additional gene-transfer strategies, currently at preclinical level or that have just entered clinical trials, to increase the efficacy and safety of HCT.

EXPERT OPINION

Gene-transfer can positively interfere with T cell functions after HCT. TK-lymphocytes have proven effective in controlling GVHD while retaining an acceptable GVT effect. Strategies exploiting new suicide molecules or engineered T cell receptors (TCRs) should be further explored to address current limitations with TK-lymphocytes and augment the efficacy and specificity of GVT and antiviral activity.

Relapse of lymphoma after allogeneic hematopoietic cell transplantation: management strategies and outcome

The outcome and management of relapsed lymphoma after allogeneic hematopoietic cell transplantation (HCT) is difficult. Therapeutic options may include donor lymphocyte infusion (DLI), reduction of immunosuppression (RIS), chemotherapy, radiation, immunotherapy, second HCT, and experimental treatments, but reported data contrasting the response and efficacy of these salvage treatments are limited. We describe the treatments, response, prognosis, and long-term survival of 72 patients with relapse of lymphoma after allogeneic HCT. Between 1991 and 2007, 227 lymphoma patients underwent allogeneic HCT. Of these, 72 (32%) developed relapse/progression after their HCT at a median of 99 days (0-1898 days); 37 had early (<100 days) post-HCT relapse. Forty-four had non-Hodgkin lymphoma (7 mantle cell, 5 indolent, 15 diffuse large B cell, 4 Burkitt's, and 13 T/Natural Killer cell), and 28 patients had Hodgkin lymphoma. At the time of HCT, 62 patients were in remission (22 in complete [CR] and 40 in partial [PR]), 1 had stable whereas 9 had progressive disease. Seventeen cases received myeloablative and 55 received a reduced-intensity conditioning regimen. At relapse, most patients had generalized lymphadenopathy, extranodal organ involvement, and advanced disease. Five patients received no intervention for the post-HCT relapse. Immunosuppressive treatment was reduced or withdrawn as the first-line therapy in 58 patients (80.5%); 47 were treated using combinations of conventional chemotherapy (n = 22), rituximab (n = 27), interferon (IFN) (n = 1), DLI (n = 7), second HCT (n = 2), local radiation (n = 23), and other therapy (n = 6). Thirty-eight patients had an objective response (CR in 30, PR in 8), and 2 had stable disease (SD). At the post-HCT relapse, favorable prognostic factors for survival after HCT included good ECOG performance status (0-2), normal lactate dehydrogenase (LDH), early stage disease (stage I-III), isolated extranodal organ involvement, and later relapse (>100 days) post-HCT. Three-year survival after HCT was significantly better in late than early relapse (53%; 95% confidence interval [CI] [34%-69%] versus 36%, [20%-52%], P = .02). Of 72 relapsed patients, 29 (40%) survived at a median of 34 (3-148) months posttransplant. The most common cause of death was underlying lymphoma (79%). The overall prognosis of relapsed/progressive lymphoma after allogeneic HCT is disappointing, yet half of patients respond to withdrawal of immunosuppression and additional therapies. Novel treatments can control lymphoma with acceptable morbidity. Particularly for patients with later relapse, ongoing treatment after relapse can yield meaningful benefit and prolonged survival.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

Graft-versus-leukemia effect of nonmyeloablative stem cell transplantation

Nonmyeloablative stem cell transplantation (NST) is increasingly used with beneficial effects because it can be applied to older patients with hematological malignancies and those with various complications who are not suitable for conventional myeloablative stem cell transplantation (CST). Various conditioning regimens differ in their myeloablative and immunosuppressive intensity. Regardless of the type of conditioning regimen, graft-versus- host disease (GVHD) in NST occurs almost equally in CST, although a slightly delayed development of acute GVHD is observed in NST. Although graft-versus-hematological malignancy effects (i.e., graft-versus-leukemia effect, graft-versus-lymphoma effect, and graft-versus-myeloma effect) also occur in NST, completely eradicating residual malignant cells through allogeneic immune responses is insufficient in cases with rapidly growing disease or uncontrolled progressive disease. Donor lymphocyte infusion (DLI) is sometimes combined to support engraftment and to augment the graft-versus-hematological malignancy effect, such as the graft-versus-leukemia effect. DLI is especially effective for controlling relapse in the chronic phase of chronic myelogenous leukemia, but not so effective against other diseases. Indeed, NST is a beneficial procedure for expanding the opportunity of allogeneic hematopoietic stem cell transplantation to many patients with hematological malignancies. However, a more sophisticated improvement in separating graft-versus-hematological malignancy effects from GVHD is required in the future.

Innate immune defense in visceral leishmaniasis: cytokine mediated protective role by allogeneic effector cell

Antileishmanial role of mouse splenic natural killer (NK) cell was studied in allogeneic condition. In vitro data indicates that NK cells of allogeneic (C57BL/6, H2(b)) non-leishmania exposed mouse have strong antileishmanial effect against Leishmania donovani infected BALB/c (H2(d)) macrophages. Physical contact between the effector (NK cell) and the target cells (infected macrophages) is essential in this system since; cell free supernatant generated after coculturing of effector cells with infected target cells fails to elicit any antileishmanial effect. Although NK cells from allogeneic mouse are strongly attached to the infected macrophages but unable to kill it in such interaction. The antileishmanial effect of allogeneic NK cells is mediated by TNF-alpha and not by IFN-gamma. In vivo cellular therapy of established infection with NK cells from non-leishmania exposed allogeneic mouse significantly reduces the total parasite burden in the spleen of infected animal.

Cytokine induced killer cells as adoptive immunotherapy strategy to augment graft versus tumor after hematopoietic cell transplantation

Donor lymphocyte infusion (DLI) is used to increase the graft versus tumor (GVT) effect after allogeneic hematopoietic cell transplant (HCT). The limited spectrum of activity and high risk of graft versus host disease (GVHD) remain major limitations of this approach. The finding of new cell populations for adoptive immunotherapy, with the ability to separate GVT from GVHD, would be useful. Here we review the main basic, preclinical and clinical research on cytokine-induced killer (CIK) cells, highlighting the aspects of their antitumor and alloreactive potentials that might favourably affect the balance between GVT and GVHD. CIK cells are ex vivo-expanded T lymphocytes sharing NK markers and endowed with a potent MHC-unrestricted antitumor activity against haematological and solid malignancies. Studies in preclinical animal models have demonstrated their low GVHD potential when infused across MHC-barriers, and recent clinical studies seem to confirm these findings in patients with hematological malignancies relapsing after HCT. If consolidated with larger clinical trials, adoptive immunotherapy with CIK cells might represent an effective alternative to classic DLI, helping HCT to succesfully meet current challenges like the extension across major HLA-barriers and application to solid tumors.

What is the role for donor natural killer cells after nonmyeloablative conditioning?

We investigated the impacts of the tempo of early (days 14, 28, and 42) donor T cell and natural killer (NK) cell engraftment, missing recipient killer cell immunoglobulin-like receptor (KIR) ligands, and numbers of donor inhibitory and activating KIR genes on hematopoietic cell transplantation (HCT) outcomes in 282 patients with hematologic malignancies given nonmyeloablative conditioning. Modeling chimerism levels as a continuous linear variable, we found that high early donor T cell chimerism was significantly associated with acute graft-versus-host disease (aGVHD) (P = .01), whereas high donor NK cell chimerism levels had no such association (P = .38). Conversely, high donor NK cell chimerism levels were significantly associated with low relapse risk (P = .0009), whereas no significant association was seen with high donor T cell chimerism (P = .10). The qualitative associations between donor T cell and NK cell chimerism levels and GVHD and relapse did not change after adjustment for the presence of recipient KIR ligands or numbers of donor inhibitory or activating KIR genes. Our data indicate that prompt engraftment of donor NK cells correlated with lessened risks of relapse, but not with GVHD, whereas the converse was true for T cells.

Induction of tumor immunity following allogeneic stem cell transplantation

The curative potential of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for many hematologic malignancies derives in large part from reconstitution of normal donor immunity and the development of a potent graft-versus-leukemia (GVL) immune response capable of rejecting tumor cell in vivo. Elucidation of the mechanisms of GVL by studies of animal models and analysis of clinical data has yielded important insights into how clinically effective tumor immunity is generated following allo-HSCT. These studies have identified NK cells and B cells as well as T cells as important mediators of the GVL response. A variety of antigenic targets of the GVL response have also been identified, and include tumor-associated antigens as well as minor histocompatibility antigens. The principles of effective GVL can now be applied to the development of novel therapies that enhance the therapeutic benefit of allogeneic HSCT while minimizing the toxicities associated with treatment. Moreover, many components of this approach that result in elimination of tumor cells following allogeneic HSCT can potentially be adapted to enhance the effectiveness of tumor immunity in the autologous setting.

Donor T cells primed on leukemia lysate-pulsed recipient APCs mediate strong graft-versus-leukemia effects across MHC barriers in full chimeras

Antigen-presenting cells (APCs) of host origin drive graft-versus-leukemia (GVL) effects but can also trigger life-threatening graft-versus-host disease (GVHD) after hematopoietic cell transplantation (HCT) across major histocompatibility complex (MHC) barriers. We show that in vitro priming of donor lymphocytes can circumvent the need of recipient-derived APCs in vivo for mediating robust GVL effects and significantly diminishes the risk of severe GVHD. In vitro, generated and expanded T cells (ETCs) mediate anti-leukemia effects only when primed on recipient-derived APCs. Loading of APCs in vitro with leukemia cell lysate, chimerism status of the recipient, and timing of adoptive transfer after HCT are important factors determining the outcome. Delayed transfer of ETCs resulted in strong GVL effects in leukemia-bearing full chimera (FC) and mixed chimera (MC) recipients, which were comparable with the GVL/GVHD rates observed after the transfer of naive donor lymphocyte infusion (DLI). Upon early transfer, GVL effects were more pronounced with ETCs but at the expense of significant GVHD. The degree of GVHD was most severe in MCs after transfer of ETCs that had been in vitro primed either on nonpulsed recipient-derived APCs or with donor-derived APCs.

Allogeneic cell therapy from immunized donors with tumor antigen peptide enhances the antitumor effect after cyclophosphamide-using non-myeloablative allogeneic hematopoietic cell transplantation

Non-myeloablative allogeneic stem cell transplantation is an option for the treatment of hematological malignancies as well as solid tumors. We recently proposed a cyclophosphamide-using non-myeloablative cell therapy in which donor lymphocytes infusion (DLI) was carried out after tolerance induction to donor cells. In this study, we tested the possibility that the cyclophosphamide-using cell therapy could be augmented by pre-immunization of donors before DLI. We initially assessed whether or not the cyclophosphamide-using cell therapy could also show antitumor effect against subcutaneously established colon 26 carcinoma. As a tumor antigen-derived peptide for colon 26, we used AH1, an immunodominant H-2Ld-binding peptide derived from the envelope protein (gp70) of an endogenous murine leukemia virus. The cyclophosphamide-using cell therapy with the DLI from donors which were pre-immunized with the AH1 peptide was compared with that from non-immunized mice. The cyclophosphamide-using cell therapy significantly suppressed subcutaneously established colon 26 carcinoma, and the tumor-rejected mice acquired the tumor-specific protective immunity. When combined with the DLI from donors that were immunized with AH1, antitumor effect of the cyclophosphamide-using cell therapy was significantly augmented. The DLI from tumor peptide-immunized donors showed no influence on donor chimerism and bodyweight of the treated mice, indicating no increased risk of graft-versus-host disease. Tumor-specific cytotoxic T lymphocytes could be generated from tumor-rejected mice. Our results indicate that the cyclophosphamide-using non-myeloablative cell therapy with the DLI from tumor peptide-immunized donors is a useful protocol to augment graft-versus-tumor effect without exacerbation of graft-versus-host disease.

Donor lymphocyte infusions for acute myeloid leukaemia

The success of donor lymphocyte infusion (DLI) in treating chronic myeloid leukaemia that had recurred after allogeneic haematopoietic stem cell transplantation provided direct evidence for the existence of an immunologically mediated graft-vs-leukaemia effect and led to the development of non-myeloablative transplantation. For patients with acute myeloid leukaemia (AML), DLI has been less effective, both as a result of its rapid growth kinetics and its decreased susceptibility to alloimmune-mediated effects. This chapter reviews the historical experience with DLI for AML, both as treatment for and prophylaxis of relapse. New approaches aimed at improving the efficacy of DLI are discussed, including administration of chemotherapy prior to DLI, use of immunomodulatory cytokines to bolster the cytotoxic effector response, priming of donor lymphocytes to recipient tumour antigens ex vivo, and infusions of alloreactive natural killer cells.

Allogeneic bone marrow transplantation and donor lymphocyte infusion in a mouse model of irradiation-induced myelodysplastic/myeloproliferation syndrome (MD/MPS): evidence for a graft-versus-MD/MPS effect

The role of graft-versus-malignancy reactivity in the effects of allogeneic hematopoietic stem cell transplantation and donor lymphocyte infusion (DLI) for myelodysplastic syndromes is as yet not well established. Clinical data are limited and animal models are scarce. Here, we report on the effects of allogeneic bone marrow transplantation (alloBMT) and DLI in a novel model of irradiation-induced murine myelodysplastic/myeloproliferation syndrome (MD/MPS). Total body irradiation with 8.5 Gy in SJL/J mice gave rise to a lethal wasting syndrome in 60% of mice, characterized by 1 degrees normocellular bone marrow with dysplastic features in erythroid, myeloid and megakaryocytic cell lineages, 2 degrees lymphosplenomegaly with spleens harboring a prominent extramedullary hematopoiesis with erythroid, myeloid and megakaryocytic lineages exhibiting dysplastic features, and foci of dysplastic hematomyelopoiesis in the liver, 3 degrees peripheral thrombocytopenia and 4 degrees evidence of disseminated infection or leukemic transformation in selected animals. This clinicopathological picture was consistent with a murine form of MD/MPS. Syngeneic or allogeneic (BALB/c) T cell-depleted BMT could not prevent the occurrence of lethal MD/MPS. In contrast, DLI at weeks 2-4 after BMT led to restoration of the dysbalanced hematomyelopoiesis. However, severe DLI-induced acute graft-versus-host disease occurred, precluding a survival advantage. We present evidence of the existence of a post-alloBMT DLI-induced graft-versus-MD/MPS effect in murine irradiation-induced MD/MPS.

Graft-versus-host disease after donor leukocyte infusions: presentation and management

Donor leukocyte infusion (DLI) is used after both myeloablative and non-myeloablative stem-cell transplantation to treat and prevent relapse, to establish full donor chimerism, and to treat and prevent infections. The major treatment-related complication of DLI is graft-versus-host disease (GVHD). The presentation and treatment of GVHD after DLI is similar to its presentation and treatment after stem-cell transplantation, with some notable exceptions. While GVHD and graft-versus-tumor (GVT) effects are highly correlated after DLI, some patients experience remission without GVHD. Studies to define tumor-specific target antigens and GVT effector cells, as well as strategies of donor T-cell manipulation and optimization of DLI dose and schedule, may ultimately lead to the consistent ability to separate GVHD from GVT activity, improvement in the safety and specificity of DLI, and enhancement of the anti-tumor activity of donor T cells.

Outcome of second allogeneic transplants using reduced-intensity conditioning following relapse of haematological malignancy after an initial allogeneic transplant

Disease relapse following an allogeneic transplant remains a major cause of treatment failure, often with a poor outcome. Second allogeneic transplant procedures have been associated with high TRM, especially with myeloablative conditioning. We hypothesized that the use of reduced-intensity conditioning (RIC) would decrease the TRM. We performed a retrospective national multicentre analysis of 71 patients receiving a second allogeneic transplant using RIC after disease relapse following an initial allogeneic transplant. The majority of patients had leukaemia/myelodysplasia (MDS) (N=57), nine had lymphoproliferative disorders, two had myeloma and three had myeloproliferative diseases. A total of 25% of patients had unrelated donors. The median follow-up was 906 days from the second allograft. The predicted overall survival (OS) and TRM at 2 years were 28 and 27%, respectively. TRM was significantly lower in those who relapsed late (>11 months) following the first transplant (2 years: 17 vs 38% in early relapses; P=0.03). Two factors were significantly associated with a better survival: late relapse (P=0.014) and chronic GVHD following the second transplant (P=0.014). These data support our hypothesis that the second RIC allograft results in a lower TRM than using MA. A proportion of patients achieved a sustained remission even when relapsing after a previous MA transplant.