Donor lymphocyte infusion: the use of alloreactive and tumor-reactive lymphocytes for immunotherapy of malignant and nonmalignant diseases in conjunction with allogeneic stem cell transplantation

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.

Haematologic malignancies with unfavourable gene mutations benefit from donor lymphocyte infusion with/without decitabine for prophylaxis of relapse after allogeneic HSCT: A pilot study

Relapse is the main cause of treatment failure for leukaemia patients with unfavourable gene mutations who receive allogeneic haematopoietic stem cell transplantation (allo‐HSCT). There is no consensus on the indication of donor lymphocyte infusion (DLI) for prophylaxis of relapse after allo‐HSCT. To evaluate the tolerance and efficacy of prophylactic DLI in patients with unfavourable gene mutations such as FLT3‐ITD, TP53, ASXL1, DNMT3A or TET2, we performed a prospective, single‐arm study. Prophylactic use of decitabine followed by DLI was planned in patients with TP53 or epigenetic modifier gene mutations. The prophylaxis was planned in 46 recipients: it was administered in 28 patients and it was not administered in 18 patients due to contraindications. No DLI‐associated pancytopenia was observed. The cumulative incidences of grade II–IV and III–IV acute graft‐versus‐host disease (GVHD) at 100 days post‐DLI were 25.8% and 11.0%, respectively. The rates of chronic GVHD, non‐relapse mortality and relapse at 3 years post‐DLI were 21.6%, 25.0% and 26.1%, respectively. The 3‐year relapse‐free survival and overall survival (OS) rates were 48.9% and 48.2%, respectively. Acute GVHD (HR: 2.30, p = 0.016) and relapse (HR: 2.46, p = 0.003) after DLI were independently associated with inferior OS. Data in the current study showed the feasibility of prophylactic DLI with/without decitabine in the early stage after allo‐HSCT in patients with unfavourable gene mutations.

S1PR5 regulates NK cell responses in preventing graft-versus-host disease while preserving graft-versus-tumour activity in a murine allogeneic haematopoietic stem cell transplantation model

Graft-versus-host disease (GVHD) remains a major complication following allogeneic haematopoietic stem cell transplantation (allo-HSCT) leading to high transplant-related mortality. Natural killer (NK) cells have been found to mitigate GVHD without attenuating the graft-versus-tumour (GVT) activity in the murine model of haematopoietic stem cell transplantation. Sphingosine-1-phosphate receptor 5 (S1PR5) is a very important chemokine receptor on NK cells that governs NK cell distribution in vivo and trafficking at lesion sites. Our preliminary studies showed that the incidence of GVHD was negatively correlated with S1PR5 expression in the NK cells of patients after allo-HSCT. In the present study, we found that S1PR5 deficiency in murine NK cells blocked the migration of NK cells from the bone marrow to the GVHD target organs and attenuated the inhibitory effects on the alloreactive T cells, especially CD3⁺ CD8⁺ T cells, which may be the reason why the loss of S1PR5 in NK cells could aggravate GVHD in recipient mice. Furthermore, we also demonstrated that the absence of S1PR5 expression in NK cells did not interfere with the antitumour effects of NK cells and T cells in vivo. Taken together, our data indicate that S1PR5 plays an essential role in balancing GVHD and GVT activity.

Donor lymphocyte infusion for prevention of relapse after unmanipulated haploidentical PBSCT for very high-risk hematologic malignancies

Unmanipulated haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) has been an established treatment to cure high-risk leukemia/lymphoma. Relapse is the main cause of treatment failure for patients with relapsed/refractory disease or with very high-risk gene mutations such as TP53, TET2, and DNMT3a. In this study, we aimed to establish the tolerance and efficacy of prophylactic donor lymphocyte infusion (DLI) with G-CSF-primed peripheral blood progenitors for prevention of relapse in these very high-risk patients after haplo-PBSCT. The prophylactic DLI was given at a median of 77 days after transplantation in 31 of 45 consecutive patients with very high-risk leukemia/lymphoma. The median dose of CD3⁺ cells for infusion was 1.8 × 10⁷/kg. The 100-day incidences of acute graft-versus-host disease (GVHD) grades 2–4 and 3–4 after DLI were 55.3% and 10.2%. The 2-year incidences of chronic GVHD and severe chronic GVHD were 52.0% and 18.2%. The 2-year incidences of non-relapse mortality and relapse were 33.1% and 32.5%. The 2-year probabilities of overall survival and relapse-free survival were 40.1% and 31.9%. Poor-risk gene mutations (p = 0.029), disease in non-remission status prior to transplantation (p = 0.005), and donors older than 40 years of age (p = 0.043) were associated with relapse after DLI. In multivariate analysis, disease in non-remission status prior to transplantation was an independent risk factor of relapse (hazard ratio = 4.079; p = 0.035). These data showed the feasibility of the prophylactic DLI in the haplo-PBSCT setting and the anti-leukemic efficacy in very high-risk leukemia/lymphoma.

Stop and go: hematopoietic cell transplantation in the era of chimeric antigen receptor T cells and checkpoint inhibitors

PURPOSE OF REVIEW

For several decades, hematopoietic cell transplantation (HCT) has been considered the standard curative therapy for many patients with hematological malignancies. In addition to the cytotoxic effects of the chemotherapy and radiation used in the conditioning regimen, the benefits of HCT are derived from a reset of the immune system and harnessing the ability of donor T cells to eliminate malignant cells. With the dawn of the era of immunotherapies in the form of checkpoint inhibitors and chimeric antigen receptor (CAR) T cells, the role of HCT has evolved.

RECENT FINDINGS

Immunotherapy with checkpoint inhibitors is increasingly being used for relapsed Hodgkin and non-Hodgkin lymphoma after autologous HCT. Checkpoint inhibitors are also being tested after allogeneic HCT with observable benefits in treating hematological malignancies, but with a potential risk of increased graft versus host disease and transplant-related mortality. Immunotherapy with Cluster of differentiation 19 CAR T cells are powerful options with aggressive B-cell malignancies both for therapy and as induction leading to allogeneic HCT.

SUMMARY

Although immunotherapies with checkpoint inhibition and CAR T cells are increasingly being used to treat hematological malignancies, HCT remains a standard of care for most of the diseases with the best chance of cure. Combination of these therapies with HCT has the potential to more effectively treat hematological malignancies.

Blocking tumor escape in hematologic malignancies: the anti-PD-1 strategy

Immunotherapy remains an important tool for treatment of hematologic malignancies. The Programmed Death-1 (PD-1) immune checkpoint pathway has emerged as a mechanism of tumor evasion from the anti-tumor immune response. The recent development of anti-PD-1 monoclonal antibodies has offered a targeted approach to cancer therapy. Several agents are in various stages of development and have shown clinical responses across a broad spectrum of both solid and hematologic malignancies. The use of anti-PD-1 therapy in hematologic malignancies is limited but has demonstrated clinical responses in relapsed/refractory disease following multiple lines of therapy. PD-1 blockade may reduce relapse rates for patients who fail to obtain a complete remission prior to autologous hematopoietic cell transplant. The role of the PD-1 pathway for tumor escape is reviewed. We explore the use of anti-PD-1 therapy in hematologic malignancies. The proposed mechanism of PD-1 blockade as a modulator of the innate and acquired immune response is considered. Finally, the challenges of anti-PD-1 therapy and the future direction of investigation in this area are reviewed.

Genetically engineered donor T cells to optimize graft-versus-tumor effects across MHC barriers

Hematopoietic stem cell transplantation has been used for more than 50 years to combat hematologic malignancies. In addition to being the first stem cell therapy, transplantation has provided evidence for the potent anti-tumor effects of T cells. Facilitating T-cell-based immunity against malignancies requires a careful balancing act between generating a robust response and avoiding off-target killing of healthy tissues, which is difficult to accomplish using bulk donor T cells. To address these issues, several approaches have been developed, drawing on basic T-cell biology, to potentiate graft-versus-tumor activity while avoiding graft-versus-host disease. Current strategies for anti-tumor cell therapies include: (i) selecting optimal T cells for transfer; (ii) engineering T cells to possess enhanced effector functions; and (iii) generating T-cell precursors that complete development after adoptive transfer. In this review, we assess the current state of the art in T-lineage cell therapy to treat malignancies in the context of allogeneic hematopoietic stem cell transplantation.

Cellular therapy following allogeneic stem-cell transplantation

Allogeneic hematopoietic stem-cell transplantation (HSCT) is the most effective approach for many patients with hematologic malignancies. Unfortunately, relapse remains the most common cause of death after allogeneic HSCT, and the prognosis of relapsed disease is poor for most patients. Induction of a graft-versus-leukemia (GVL), or graft-versus-tumor, effect through the use of donor leukocyte infusion (DLI), or donor lymphocyte infusion, has been remarkably successful for relapsed chronic myelogenous leukemia. Unfortunately, response to DLI in other hematologic malignancies is much less common and depends on many factors including histology, pace and extent of relapse, and time from HSCT to relapse. Furthermore, graft-versus-host disease (GVHD) is common after DLI and often limits successful immunotherapy. Ultimately, manipulations to minimize GVHD while preserving or enhancing GVL are necessary to improve outcomes for relapse after allogeneic HSCT.

Current immunotherapy for solid tumors

Explorative knowledge of cellular and molecular mechanisms of immune function and regulation has provided optimism in developing cancer immunotherapy. However, three decades of experimental and clinical investigations to offer powerful immunotherapeutic strategies against solid tumors, with the possible exception of monoclonal antibody-targeted therapies, have not succeeded in significantly prolonging patient survival. Nonspecific immune approaches, including cytokine-based therapies and allogeneic hematopoietic stem cell transplantation, have so far produced consistent, although limited, results. In this review, we present the developments of cell transfer-based strategies that, in preclinical studies, have demonstrated potential efficacy, but have only established tumor regression in limited numbers of patients. The key to success demands creative combinations of tumor antigens, adjuvance, gene modification and various administration strategies in the development of cell-based therapies together with other cancer-treatment principles, often in a stepwise 'space-rocket-type' approach. Combined efforts of several scientific disciplines, such as tumor biology and immunology, as well as cell and gene research in transplantation, will open new venues. New regulation for clinical trials with advanced therapy medicine products to ensure patient safety will be highlighted.

Successful treatment of refractory donor lymphocyte infusion-induced immune-mediated pancytopenia with rituximab

A 6-year-old male with chronic granulomatous disease, who was transplanted with bone marrow and exhibited increasing mixed chimerism, subsequently received two donor lymphocyte infusions (DLI). Two weeks after the second DLI, the patient developed acute graft-versus-host disease (GVHD) and progressive pancytopenia that was associated with autoantibody production. Conventional treatment did not improve the pancytopenia. However, administration of Rituximab (RTX) (375 mg/m(2)/week for four consecutive weeks) resulted in a rapid resolution of the pancytopenia. The patient achieved full donor chimerism without GVHD symptoms. RTX can be valuable for managing immune-mediated cytopenias that arise after DLI and are refractory to conventional therapies.

Graft versus neuroblastoma reaction is efficiently elicited by allogeneic bone marrow transplantation through cytolytic activity in the absence of GVHD

Continuous efforts are dedicated to develop immunotherapeutic approaches to neuroblastoma (NB), a tumor that relapses at high rates following high-dose conventional cytotoxic therapy and autologous bone marrow cell (BMC) reconstitution. This study presents a series of transplant experiments aiming to evaluate the efficacy of allogeneic BMC transplantation. Neuro-2a cells were found to express low levels of class I major histocompatibility complex (MHC) antigens. While radiation and syngeneic bone marrow transplantation (BMT) reduced tumor growth (P < 0.001), allogeneic BMT further impaired subcutaneous development of Neuro-2a cells (P < 0.001). Allogeneic donor-derived T cells displayed direct cytotoxic activity against Neuro-2a in vitro, a mechanism of immune-mediated suppression of tumor growth. The proliferation of lymphocytes from congenic mice bearing subcutaneous tumors was inhibited by tumor lysate, suggesting that a soluble factor suppresses cytotoxic activity of syngeneic lymphocytes. However, the growth of Neuro-2a cells was impaired when implanted into chimeric mice at various times after syngeneic and allogeneic BMT. F1 (donor-host) splenocytes were infused attempting to foster immune reconstitution, however they engrafted transiently and had no effect on tumor growth. Taken together, these data indicate: (1) Neuro-2a cells express MHC antigens and immunogenic tumor associated antigens. (2) Allogeneic BMT is a significantly better platform to develop graft versus tumor (GVT) immunotherapy to NB as compared to syngeneic (autologous) immuno-hematopoietic reconstitution. (3) An effective GVT reaction in tumor bearing mice is primed by MHC disparity and targets tumor associated antigens.

The immunological impact of genetic drift in the B10.BR congenic inbred mouse strain

The MHC-matched, minor histocompatibility Ag (miHA)-mismatched B10.BR-->CBA strain combination has been used to elucidate the immunobiology of graft-vs-host disease (GVHD) following allogeneic bone marrow transplantation. Studies conducted in the 1980s had established that B10.BR CD8+ T cells were capable of mediating GVHD in the absence of CD4+ T cells, and that CD4+ T cells were unable to induce lethal disease. In more recent studies with this GVHD model, we detected etiological discrepancies with the previously published results, which suggested that genetic drift might have occurred within the B10.BR strain. In particular, there was increased allorecognition of CBA miHA by B10.BR CD4+ T cells, as determined by both TCR Vbeta spectratype analysis and the induction of lethal GVHD in CBA recipients. Additionally, alloreactivity was observed between the genetically drifted mice (B10.BR/Jdrif) and mice rederived from frozen embryos of the original strain (B10.BR/Jrep) using Vbeta spectratype analysis and IFN-gamma ELISPOT assays, suggesting that new miHA differences had arisen between the mice. Furthermore, T cell-depleted B10.BR/Jdrif bone marrow cells were unable to provide long-term survival following either allogeneic or syngeneic bone marrow transplantation. Gene expression analysis revealed several genes involved in hematopoiesis that were overexpressed in the lineage-negative fraction of B10.BR/Jdrif bone marrow, as compared with B10.BR/Jrep mice. Taken together, these results suggest that genetic drift in the B10.BR strain has significantly impacted the immune alloreactive response in the GVHD model by causing altered expression of miHA and diminished capacity for survival following transplantation into lethally irradiated recipients.

A pilot study of allogeneic cellular therapy for patients with advanced hematologic malignancies

Allogeneic hematopoietic stem cell transplantation provides curative therapy for some patients with advanced hematologic malignancies. Disease response after allogeneic transplant is, at least in part, mediated by donor immune cells. In this report we describe a cellular therapy using haploidentical peripheral blood stem cells administered after very low dose total body irradiation (TBI) (100cGy). The donor cells were anticipated to be rejected, so no graft-versus-host (GVHD) prophylaxis was used. Patients with persistent disease beyond 8 weeks could be further treated with infusions of irradiated haploidentical donor cells. Of the 10 patients enrolled in the study, durable engraftment of allogeneic cells was seen in one patient. Two patients with resistant relapsed acute myelogenous leukemia (AML) had a disease response. Analysis of T cell reactivity from one patient who achieved a complete response but did not have durable engraftment of donor cells indicated that disease response was associated with the generation of host-derived anti-leukemic cytotoxic CD8+ T cells that reacted with an AML-associated proteinase 3 epitope. Results from this patient suggest that allogeneic therapy induced a host anti-tumor response associated with cytotoxic T cells reactive with a low affinity self-antigen.

Inter-strain tissue-infiltrating T cell responses to minor histocompatibility antigens involved in graft-versus-host disease as determined by Vbeta spectratype analysis

Lethal graft-vs-host disease (GVHD) can be induced between MHC-matched murine strains expressing multiple minor histocompatibility Ag differences. In the B6->BALB.B model, both CD4(+) and CD8(+) donor T cells can mediate lethal GVHD, whereas in the B6->CXB-2 model, only CD8(+) T cells are lethal. TCR Vbeta CDR3-size spectratyping was previously used to analyze CD8(+) and CD4(+) T cell responses in lethally irradiated BALB.B and CXB-2 recipients, which showed significant overlap in the reacting repertoires. However, CD4(+) T cells exhibited unique skewing of the Vbeta2 and 11 families in only BALB.B recipients. These Vbeta family reactivities were confirmed by immunohistochemical staining of lingual epithelial infiltrates, and by positive and negative selection Vbeta family transfer experiments for GVHD induction in BALB.B recipients. We have now extended these studies to examine the T cell repertoire responses involved in target tissue damage. Infiltrating B6 host-presensitized CD8(+) and CD4(+) T cells were isolated 8-10 days post-transplant from the spleens, intestines and livers of CXB-2 and BALB.B transplant recipients. For both T cell subsets, the results indicated overlapping tissue skewings between the recipients, also between the tissues sampled within the respective recipients as well as tissue specific responses unique to both the BALB.B and CXB-2 infiltrates. Most notably, the CD4(+) Vbeta 11(+) family was skewed in the intestines of BALB.B but not CXB-2 recipients. Taken together, these data suggest that there are likely to be target tissue-related anti-multiple minor histocompatibility Ag-specific responses in each of the strain recipients, which may also differ from those found in peripheral lymphoid organs.

Completely mismatched allogeneic CD3/CD28 cross-linked Th1 memory cells elicit anti-leukemia effects in unconditioned hosts without GVHD toxicity

Fully allogeneic CD3/CD28 cross-linked Th1 cells were found to elicit host-mediated anti-leukemia effects without GVHD toxicity. Mice inoculated with a lethal dose of BCL1 leukemia demonstrated significantly enhanced survival after allogeneic Th1 treatment. Cure rates of 12.5% with a single allogeneic cell infusion and 31.25% with multiple infusions were demonstrated. Cured mice were able to reject rechallenge with a lethal dose of tumor without further treatment. These results suggest that use of intentionally mis-matched, Th1 memory cells infused with cross-linked CD3/CD28 could represent a novel clinical approach to eliciting potent anti-tumor effects in patients without conditioning and without GVHD toxicity.

Donor leukocyte infusions for the treatment of relapsed acute leukemia after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (SCT) offers the only hope for cure for many adults with acute leukemia. Unfortunately, many patients relapse and die of their disease even after transplantation. Although in some cases, allogeneic SCT is effective because the intensive conditioning therapy eradicates all malignant cells, it has long been recognized that the adoptive transfer of donor immunity plays a critically important role in the induction and maintenance of remission. Recognition of the graft-versus-leukemia (GVL) effect of allogeneic SCT has prompted attempts at remission re-induction by adoptive immunotherapy with donor lymphocyte infusions (DLIs) in patients with relapsed disease after allogeneic SCT. In some cases, DLI-induced remissions are sustained and patients cured when no other treatment modality was effective. This review discusses the rationale, biology, complications and future applications of DLI in acute leukemia patients after allogeneic SCT.

Pretransplant treatment of donors with immunomodulators to control graft-versus-host disease (GVHD) in transplant recipients

OBJECTIVE

Prevention of graft-versus-host disease (GVHD) by pretransplant donor treatment with known immunomodulators like complete Freund's adjuvant (CFA) and synthetic oligo-deoxynucleotides expressing CpG motifs (CpG).

METHODS

Induction of GVHD by inoculation of C57BL/6 (C57) splenocytes into sublethally irradiated (BALB/c x C57BL/6) F1 (F1) mice. Splenocytes were derived from either naive C57 mice or from C57 mice that were treated previously with the immunomodulators.

RESULTS

Inoculation of CFA or CpG into C57 mice led to an increase in the total number of spleen cells and resulted in activation of immunoregulatory cells that significantly suppressed mixed allogeneic lymphocyte reaction in vitro. CFA-treated C57 splenocytes led to GVHD-related death in only 14 out of 61 F1 recipients while the remaining 47 mice survived without disease for more than 200 days. Pretransplant treatment of donor C57 mice with GpG emulsified in incomplete Freund's adjuvant resulted in 19/20 GVHD-free survivors of sublethally irradiated F1 mice for more than 200 days. In contrast, naive C57 splenocytes injected into sublethally irradiated F1 recipients induced severe GVHD, which resulted in the death of 77/78 recipient mice (median of survival was 16 days).

CONCLUSION

Our results suggest that adjuvant-induced immunoregulation of donor cells prior to allogeneic cell therapy may augur a new strategy that will bring the benefits of safe cellular immunotherapy aiming to eradicate malignant and nonmalignant pathological cells while avoiding or minimizing the risk of GVHD.

Hematopoietic mixed chimerism derived from allogeneic embryonic stem cells prevents autoimmune diabetes mellitus in NOD mice

Embryonic stem cell (ESC)-derived hematopoietic stem cells (HSC), unlike HSC harvested from the blood or marrow, are not contaminated by lymphocytes. We therefore evaluated whether ESC-derived HSC could produce islet cell tolerance, a phenomenon termed graft versus autoimmunity (GVA), without causing the usual allogeneic hematopoietic stem cell transplant complication, graft-versus-host disease (GVHD). Herein, we demonstrate that ESC-derived HSC may be used to prevent autoimmune diabetes mellitus in NOD mice without GVHD or other adverse side effects. ESC were cultured in vitro to induce differentiation toward HSC, selected for c-kit expression, and injected either i.v. or intra-bone marrow (IBM) into sublethally irradiated NOD/LtJ mice. Nine of 10 mice from the IBM group and 5 of 8 from the i.v. group did not become hyperglycemic, in contrast to the control group, in which 8 of 9 mice developed end-stage diabetes. All mice with >5% donor chimerism remained free of diabetes and insulitis, which was confirmed by histology. Splenocytes from transplanted mice were unresponsive to glutamic acid decarboxylase isoform 65, a diabetic-specific autoantigen, but responded normally to third-party antigens. ESC-derived HSC can induce an islet cell tolerizing GVA effect without GVHD. This study represents the first instance, to our knowledge, of ESC-derived HSC cells treating disease in an animal model.

Treatment of autoimmune diseases in MRL/lpr mice by allogenic bone marrow transplantation plus adult thymus transplantation

MRL/lpr mice (H-2(k)) with Fas gene mutation develop severe autoimmune diseases, and their haematolymphoid cells such as bone marrow and spleen cells showed a low apoptotic activity by irradiation. Therefore, conventional bone marrow transplantation (BMT) cannot be used to treat autoimmune diseases in these mice (chimeric resistance). In the present study, we examine the effects of additional adult thymus transplantation (TT) from the same donor on successful BMT. When the MRL/lpr mice were lethally irradiated (9 x 5Gy) and reconstituted with 3 x 10(7) of C57BL/6 mouse (H-2b) bone marrow cells (BMCs) in conjunction with TT, the mice significantly survived long term and showed a high donor-derived chimerism in comparison with those treated with BMT alone. Interestingly, the numbers of not only donor-derived T cells but also B cells increased significantly in the mice treated with BMT plus TT, even at the early phase of BMT. The number of aberrant CD3+B220+ cells decreased significantly, and the numbers of lymphocyte subsets were also normalized 4 weeks after the treatment. Finally, the autoimmune diseases in MRL/lpr mice could be cured by BMT with TT. These results indicate that the combination of BMT plus TT can overcome the chimeric resistance and treat the autoimmune diseases in MRL/lpr mice.

Early detection and rapid isolation of leukemia-reactive donor T cells for adoptive transfer using the IFN-gamma secretion assay

PURPOSE

The poor immunogenicity of most leukemias and the lack of specificity of the donor T cells limit the in vivo effectiveness of conventional donor lymphocyte infusions in many patients suffering from persistent or recurrent leukemia after allogeneic stem cell transplantation. These limitations may be overcome by the adoptive transfer of in vitro generated leukemia-reactive T cells. Although the potential clinical efficacy of this approach has been shown previously, lack of reproducibility of the procedure and the inability to show persistence and survival of the transferred T cells hampered further clinical application. The purpose of this study was to develop a new, broadly applicable strategy for the efficient generation and isolation of leukemia-reactive T cells with a better probability to survive and expand in vivo.

EXPERIMENTAL DESIGN

Myeloid and B-cell leukemias were modified into professional immunogenic antigen-presenting cells, and used to stimulate HLA-matched donor T cells. After two stimulations, responding donor T cells were isolated based on their secretion of IFN-gamma and tested for their capacity to recognize and kill the primary leukemia.

RESULTS

Using one universal stimulation and isolation protocol for various forms of leukemia, T-cell populations containing high frequencies of leukemia-reactive T cells could reproducibly be generated and early isolated under mild stimulatory conditions. Isolated T cells still had high proliferative potential and their reactivity seemed to be restricted to cells of the patient's hematopoiesis.

CONCLUSION

We here show a new robust procedure for the generation and isolation of leukemia-reactive T cells for adoptive transfer.

Allogeneic bone marrow transplantation in models of experimental autoimmune encephalomyelitis: evidence for a graft-versus-autoimmunity effect

Autologous hematopoietic stem cell transplantation (HSCT) is being explored in the treatment of severe multiple sclerosis (MS), and is based on the concept of "resetting" the immune system. The use of allogeneic HSCT may offer additional advantages, such as the replacement of the autoreactive immune compartment by healthy allogeneic cells and development of a graft-versus-autoimmunity (GVA) effect. However, in clinical practice, the genetic susceptibility to MS of allogeneic stem cell donors is generally unknown, and GVA may therefore be an important mechanism of action. Experimental autoimmune encephalomyelitis (EAE)-susceptible and -resistant mouse strains were used to determine the roles of genetic susceptibility, level of donor-chimerism, and alloreactivity in the therapeutic potential of syngeneic versus allogeneic bone marrow transplant (BMT) for EAE. After transplantation and EAE induction, animals were evaluated for clinical EAE and ex vivo myelin oligodendrocyte glycoprotein-specific proliferation. Early after BMT, both syngeneic and allogeneic chimeras were protected from EAE development. On the longer term, allogeneic but not syngeneic BMT conferred protection, but this required high-level donor-chimerism from EAE-resistant donors. Importantly, when EAE-susceptible donors were used, robust protection from EAE was obtained when active alloreactivity, induced by donor lymphocyte infusions, was provided. Our findings indicate the requirement of a sufficient level of donor-chimerism from a nonsusceptible donor in the therapeutic effect of allogeneic BMT. Importantly, the data indicate that, independently of genetic susceptibility, active alloreactivity is associated with a GVA effect, thereby providing new evidence to support the potential role of allogeneic BMT in the treatment of MS.

Allogeneic Intrabone Marrow-Bone Marrow Transplantation plus Donor Lymphocyte Infusion Suppresses Growth of Colon Cancer Cells Implanted in Skin and Liver of Rats

We have recently found that allogeneic intrabone marrow-bone marrow transplantation (IBM-BMT) + donor lymphocyte infusion (DLI) using CD4(+) cell-depleted spleen cells (CD4(-) cells) can prevent graft-versus-host disease (GvHD) but suppress tumor growth (Meth A: fibrosarcoma) in mice. In the present study, we show that allogeneic IBM-BMT + DLI using CD4(-) cells also has suppressive effects on the growth of colon cancer cells implanted not only in the skin but also in the liver of rats. First, we examined the effects of allogeneic IBM-BMT + DLI on the subcutaneously inoculated ACL-15 (rat colon cancer cell line). Lethally irradiated Fischer rats (F344 rats) were transplanted with T-cell-depleted bone marrow cells (BMCs) from Brown Norway (BN) rats. Simultaneously, DLI was performed using whole spleen cells (whole cells), CD4(+) cell-depleted spleen cells (CD4(-) cells) or CD8(+) cell-depleted spleen cells (CD8(-) cells) of BN rats. Although allogeneic IBM-BMT + DLI suppressed tumor growth, a considerable number of rats treated with allogeneic IBM-BMT + DLI using whole cells or CD8(-) cells died due to GvHD. In contrast, allogeneic IBM-BMT + DLI using CD4(-) cells also suppressed tumor growth, but there was no GvHD. Based on these findings, we next examined the effects of allogeneic IBM-BMT + DLI using CD4(-) cells on the cancer cells implanted in the liver. Allogeneic IBM-BMT + DLI using CD4(-) cells via the portal vein significantly prolonged the survival. These results suggest that allogeneic IBM-BMT + DLI using CD4(-) cells could become a new strategy for the treatment of solid tumors.

Highly Sensitive Patient-Specific Real-Time PCR SNP Assay for Chimerism Monitoring after Allogeneic Stem Cell Transplantation

Chimerism analysis after allogeneic stem cell transplantation (allo-SCT) is an important diagnostic tool for the documentation of engraftment, early detection of graft failure, and recurrence of the disease. Current assays rely on the genetic polymorphism between the donor and the recipient, and allow semiquantitative or quantitative analysis of chimerism. The most common method in use is based on the amplification of the short tandem repeats (STR). This method, with 1% to 5 sensitivity, is useful for the documentation of engraftment, but is insufficient for the detection of minimal residual disease or early relapse, when medical intervention is urgently needed. Recently, single-nucleotide polymorphism (SNP) has been suggested as an alternative, more accurate system to monitor chimerism. The purpose of our study was to develop an easy, economical, and sensitive method for the detection of chimerism following allo-SCT using the SNP technology. Our approach is based on SNP patient-specific quantitative real-time polymerase chain reaction (PCR) using nonlabeled primers. Our results show that this allele-specific SNP real-time PCR approach is sensitive, relatively cheap, and offers a fast and reliable assay for the monitoring of hematopoietic engraftment and for the detection of minimal residual disease in patients after allo-SCT.

Revisiting the role of hematopoietic stem cell transplantation in chronic lymphocytic leukemia

Since the advent of hematopoietic stem cell transplantation more than 40 years ago, numerous methods of transplantation have been developed, modified and improved upon. Although hematopoietic stem cell transplantation has been used in a variety of malignant diseases since then, its use in the treatment of chronic lymphocytic leukemia has recently started to gain interest. Patients with chronic lymphocytic leukemia are generally elderly, and because of its relatively benign course, they were not considered suitable candidates for hematopoietic stem cell transplantation. Nonetheless, there have been marked improvements in transplantation techniques, including better conditioning regimens that have decreased treatment-related morbidity and mortality. In this article, the authors review the most recent data on hematopoietic stem cell transplantation in chronic lymphocytic leukemia as well as the change in risk stratification based on newer prognostic factors and its impact on treatment decisions in chronic lymphocytic leukemia.

Effect of KRN7000 on induced graft-vs-host disease

OBJECTIVE

Graft-vs-host disease (GVHD) is a serious complication of allogeneic stem cell transplantation (SCT) and donor lymphocyte infusion (DLI), for which no effective therapy exists. In our study, KRN7000, a synthetic analog of alpha-galactosylceramide, known for its ability to activate natural killer T cells, was tested for its ability to prevent onset of GVHD in a murine model of haploidentical major histocompatible (MHC) mismatched hematopoietic cells.

METHODS

Irradiated (BALB/cXC57BL/6)F1 mice were inoculated with parental C57BL/6 splenocytes with or without SCT. KRN7000 was given intraperitoneally as single or multiple doses at 100 microg/kg/dose and mice were followed up for GVHD clinical symptoms and for survival. The effect of KRN7000 treatment was also tested in vitro for the induction of suppression of alloreactivity in mixed lymphocyte reaction (MLR).

RESULTS

KRN7000 prevented development of GVHD symptoms in almost all mice and 52/53 mice maintained a healthy profile for more than 235 days. Most vehicle-treated mice or untreated controls died of GVHD within a median of 3 weeks. KRN7000 treatment did not prevent engraftment of donor cells following sublethal total-body irradiation (TBI) and allowed durable persistence of donor cells following lethal TBI and SCT. Splenocytes derived from KRN7000-treated mice suppressed efficiently mixed lymphocyte reaction (MLR) in vitro.

CONCLUSION

GVHD induced by alloreactive lymphocytes can be prevented by KRN7000. GVHD prevention may be accomplished by regulation of T cell function and might thus provide a new modality for safer SCT and DLI.

The impact of granulocyte colony stimulating factor at content of donor lymphocytes collected for cellular immunotherapy

BACKGROUND AND OBJECTIVES

Donor lymphocyte infusions (DLI) have become widely used for prevention or treatment of relapse after allogeneic hematopoietic stem cell transplantation. Increasing use of reduced intensity conditioning regimens (RICR) and subsequent application of DLI forced the hemapheresis centers to collect donor lymphocytes in certain quantity and quality. The place of growth factors especially granulocyte colony stimulating factor (rhG-CSF, filgrastim) in allogeneic hemapoietic stem cell (HSC) collection is established, but there is no consensus about the role of rhG-CSF. We aimed to clarify the dose effect of rhG-CSF on lymphocyte subpopulations (CD3+, CD3+4+, CD3+8+, CD19+, CD3-16+56+) cells and CD34+ HSC.

DONORS AND METHODS

Major indications for DLI (mean volume: 180+/-52 ml) were for relapse or transplants using RICR mainly in patients with acute leukemia (n=20) or chronic myeloid leukemia (n=15). In four years we performed 40 lymphocyte apheresis (LA) on 30 healthy (med. age 28, M/F 21/9) donors using continuous flow cell separators by processing 2-2.5 times of their total blood volume (TBV). The apheresis data is divided into three groups according to rhG-CSF dose used for priming. Donors in Group I (n=18), Group II (n=9) and Group III (n=13) received no rhG-CSF (steady state), rhG-CSF 5 microg/kg/dsc x 5 days and rhG-CSF 10 microg/kg/dsc x 5 days, respectively. There was no difference within groups concerning TBV processed and recipient body weight.

RESULTS

A total of 11,565 ml (+/-3700) of blood was processed in 216 min (+/-36.5) at an inlet of 56.8 ml/min (+/-10.6) using 999 ml (+/-307) ACD. The CD34+ HSC increased with increasing rhG-CSF dose as expected. Median CD3+ lymphocyte yield per recipient body weight in Group I, II and III were 0.9 x 10e8/kg (range: 0.1-2.1), 2.9 x 10e8/kg (range: 1.6-4.3) and 2.1 x 10e8/kg (range: 0.6-6.9), respectively. The primed donors T lymphocyte yield was 2-3-fold more in comparison to Group I. This gain was most significant between Group I and III in terms of mean CD3+ (1.09 x 10e8/kg vs 2.41 x 10e8/kg, p=0.02), CD3+4+ (0.64 x 10e8/kg vs 1.44 x 10e8/kg, p=0.02) and CD3+8+ (0.42 x 10e8/kg vs 0.89 x 10e8/kg, p=0.03) cells, respectively.

CONCLUSION

Though the yield of lymphocyte subsets in G-CSF primed donors exceeds the non-primed donors, the target range of 1 x 10e7-1 x 10e8/kg CD3+ lymphocytes could be achieved in the majority of the apheresis procedures without rhG-CSF priming. The yield of T and B lymphocyte subsets are increased by G-CSF stimulation but not on a logarithmic scale, which did not correlate into a clinical relevance.

Allogeneic versus syngeneic killer splenocytes as effector cells for the induction of graft-versus-tumor effect

The effect of allogeneic versus syngeneic killer cells derived from normal or severe combined immunodeficiency disease (SCID) mice was evaluated for induction of antitumor reaction in a murine model of mammary carcinoma. Tumor cells of H-2d origin were injected intravenously into H-2(d/b) mice 24 hours after total body irradiation (4 Gy). On the following day, lymphokine-activated killer (LAK) splenocytes, derived from either minor (H-2d) or major (H-2b) histocompatibility complex (MHC)-mismatched parental normal mice or MHC (H-2b)-mismatched SCID mice, were given intravenously. LAK cells of H-2d normal or SCID mice, syngeneic to the tumor, were inoculated in parallel. The results show that LAK cells derived from minor histocompatibility complex-mismatched or MHC-mismatched parental normal mice improved the probability of tumor-free survival as compared with LAK cells syngeneic to the tumor cells, but they aggravated the severity of graft-versus-host disease. SCID splenocytes serving as a source of natural killer (NK) cells were expanded and activated in vitro by rIL-2 to obtain a sufficient number of DX5+ CD3- CD8- NK cells (SCID-LAK). H-2b SCID-LAK cells did not cause graft-versus-host disease and significantly delayed tumor growth compared with syngeneic H-2d SCID-LAK cells, as indicated by tumor colony assays in vitro and adoptive transfer experiments. However, the graft-versus-tumor effect was not long lasting, and treated mice finally died of tumor. Our results show an advantage of allogeneic over syngeneic cell therapy for achieving a graft-versus-tumor effect by rIL-2-activated T cells and NK cells. Periodic repetition of NK treatments may be required to achieve more durable antitumor effects.

Prompt initiation of immunotherapy in children with an increasing number of autologous cells after allogeneic HCT can induce complete donor-type chimerism: a report of 14 children

Immunotherapy consisting of withdrawal of immunosuppression and/or donor lymphocyte infusions was initiated in 14 children (10 acute lymphoblastic leukemia, three acute myeloblastic leukemia and one myelodysplastic syndrome) with an increasing amount of autologous DNA (increasing mixed chimerism, inMC) detected after allogeneic hematopoietic cell transplantation (HCT). Two children were in relapse when inMC was detected, 12 remained in CR. Children with overt relapse at the time of cessation of cyclosporine A (CsA) received "debulking" chemotherapy. One of them developed acute grade III graft-versus-host disease, converted to complete donor chimerism (CC) and achieved remission. Another patient did not respond and died due to disease progression. Among 12 children treated in remission, 11 responded with conversion to CC, seven after CsA withdrawal and four after DLI. One patient did not respond, rejected the graft and died due to pulmonary aspergillosis. In one patient, the response was transient, inMC reappeared and frank relapse occurred. One patient developed isolated CNS relapse despite conversion to CC, but achieved CR after conventional treatment. One child died in CC due to infection. No graft-versus-host disease (GvHD)-related death occurred. A total of 10 patients are alive in remission with median follow-up of 338 days. Our results support the hypothesis that chimerism-guided immunotherapy after alloHCT may prevent progression to hematological relapse.

Retrospective comparison of CD34-selected allogeneic peripheral blood stem cell transplantation followed by CD8-depleted donor lymphocyte infusions with unmanipulated bone marrow transplantation

We have previously reported the feasibility of allogeneic CD34-selected PBSC transplantation followed by pre-emptive CD8-depleted DLI (study group). In this report, we retrospectively compare the clinical outcome of the 24 patients included in this study with an historical group of 35 patients receiving unmanipulated marrow (BMT group). Patients in the study group had significantly faster neutrophil and platelet recovery and were discharged earlier than BMT patients. The actuarial 150-day (after DLI) probability of developing grade II-IV acute GVHD was 28% for the study group versus 62% for the BMT group (p=0.002). The actuarial 2-year probability of developing chronic GVHD was similar (37 versus 36% (NS)) but chronic GVHD was significantly delayed in the study group (p=0.003). The actuarial 2-year probability of relapse was 30% in the study group versus 33% in the BMT group (NS). The actuarial 2-year probability of survival was 45% in the study group versus 43% in the BMT group (NS). We conclude that allogeneic transplantation of CD34-selected PBSC followed by pre-emptive CD8-depleted DLI is feasible with rapid engraftment and minimizes the risk of severe GVHD. Large prospective trials are required to confirm these results.

Immunotherapy of cancer by active vaccination: does allogeneic bone marrow transplantation after non-myeloablative conditioning provide a new option?

The critical role of antigen-specific T cells in cancer immunotherapy has been amply demonstrated in many model systems. Though success of clinical trials still remains far behind expectation, the continuous improvement in our understanding of the biology of the immune response will provide the basis of optimized cancer vaccines and allow for new modalities of cancer treatment. This review focuses on the current status of active therapeutic vaccination and future prospects. The latter will mainly be concerned with allogeneic bone marrow cell transplantation after non-myeloablative conditioning, because it is my belief that this approach could provide a major breakthrough in cancer immunotherapy. Concerning active vaccination protocols the following aspects will be addressed: i) the targets of immunotherapeutic approaches; ii) the response elements needed for raising a therapeutically successful immune reaction; iii) ways to achieve an optimal confrontation of the immune system with the tumor and iv) supportive regimen of immunomodulation. Hazards which one is most frequently confronted with in trials to attack tumors with the inherent weapon of immune defense will only be briefly mentioned. Many question remain to be answered in the field of allogeneic bone marrow transplantation after non-myeloablative conditioning to optimize the therapeutic setting for this likely very powerful tool of cancer therapy. Current considerations to improve engraftment and to reduce graft versus host disease while strengthening graft versus tumor reactivity will be briefly reviewed. Finally, I will discuss whether tumor-reactive T cells can be "naturally" maintained during the process of T cell maturation in the allogeneic host. Provided this hypothesis can be substantiated, a T cell vaccine will meet a pool of virgin T cells in the allogeneically reconstituted host, which are tolerant towards the host, but not anergised towards tumor antigens presented by MHC molecules of the host.

Localized relapse in bone marrow in a posttransplantation patient with t(6;9) acute myeloid leukemia

We report a 38-year-old woman with t(6;9) acute myeloid leukemia who relapsed with localized leukemic cell growth in the bone marrow after she had undergone allogeneic bone marrow transplantation. The localized cell growth was first recognized by an apparent discrepancy in the DEK-CAN fusion transcript levels between the aspirates from the left and right iliac bone marrow. Magnetic resonance imaging of the iliac bone revealed localized cell accumulation in the left side. The nonhomogeneous and localized leukemic cell growth in this case may have been due to the graft-versus-leukemia effect following allogeneic transplantation with donor lymphocyte infusion. Serial monitoring of molecular markers for leukemia at different sites or magnetic resonance imaging of the bone marrow may be of value in detecting this type of relapse.

Emerging cancer-targeted therapies

There is reason to believe that the unfolding revolution in molecular biology and translational research will allow selective targeting of tumor cells, and radically change the way general practitioners and pediatric oncologists treat and follow children with cancer. This article highlights some of the most promising approaches being tested in the field. By learning about the underlying biology, the remaining hurdles, the projected timeline, and the possible impact of new therapies on the practice of pediatric oncology, health care professionals and patients should be better prepared for the future of pediatric oncology.

Non-myeloablative transplantation

The concept of utilizing enhanced immunosuppression rather than myeloablative cytotoxic conditioning has allowed the engraftment of allogeneic stem cells from related and unrelated donors with lower early transplant-related mortality (TRM) and morbidity. This approach shifts tumor eradication to the graft-vs-host immune response directed against minor histocompatibility antigens expressed on tumor cells. This is not without risk, as the long-term effects of graft-versus-host disease (GVHD), it's treatment, or resulting complications and immunodeficiency may be life threatening. However, this approach does allow the application of a potentially curative procedure to elderly or medically infirm patients who would not tolerate high-dose conditioning regimens. Section I, by Dr. Sandmaier, describes the current use of nonmyeloablative regimens and matched related or unrelated donors for the treatment of patients with CLL, CML, acute leukemia, MDS, lymphoma, and myeloma. In Section II, Dr. Maloney discusses the use of cytoreductive autologous followed by planned non-myeloablative allografts as treatment for patients with myeloma or NHL. This tandem transplant approach has a lower TRM than conventional high dose allografting. The nonmyeloablative allograft may allow the graft-versus-tumor (GVT) immune response to eradicate the minimal residual disease that causes nearly all patients with low-grade NHL or myeloma to relapse following autologous transplantation. In Section III, Dr. Mackinnon discusses the risks and benefits of T cell depletion strategies to prevent acute GVHD, while retaining GVT activity by planned donor lymphocyte infusions. Finally, in Section IV, Dr. Shizuru discusses the relationship between GVHD and GVT activity. Future studies, employing a greater understanding of these issues and the separation of GVHD from GVT activity by immunization or T cell cloning, may allow nonmyeloablative allogeneic transplantation to be safer and more effective.