Low-intensity allogeneic hematopoietic stem cell transplantation for myeloid malignancies: separating graft-versus-leukemia effects from graft-versus-host disease

[Second Survey on Patient-centred Care of Ocular Graft-versus-Host Disease in Germany]

BACKGROUND

graft-versus-host disease (GvHD) is a common complication after allogeneic haematopoietic stem cell transplantation (allo-SCT) and causes immunological rejection of host tissues, which can occur both acute or chronically. Approximately 40 - 80% of patients with the diagnosis of chronic GvHD (cGvHD) also develop ocular GvHD. For these patients, immediate and uncomplicated access to interdisciplinary patient-centred care is important. We performed this survey to improve understanding of the structure of patient-centred care in Germany.

METHODS

The GvHD working party of the Cornea Section of the German Society of Ophthalmology sent the "Survey of ocular GvHD 2016" to all university and specialised hospitals in Germany. We evaluated the data and compared the information with survey results from 2014, in order to draw conclusions about the structure and process of patient-centred care in ocular GvHD. Besides the questions from 2014 on the numbers of allo-SCT, frequency of examinations, etc. there were additional questions on the prescription of ciclosporin and autologous serum eye drops. The question on frequency examination was further expanded to include examinations of paediatric patients.

RESULTS

Of 30 participating hospitals, 22 had already taken part in the first survey. According to the information they provided, approx. 1860 allo-SCTs were performed in the transplantation units of the participating eye hospitals in 2016. This was more than half of the transplantations performed in Germany. Ophthalmologists examined between 2 and 250 Patients per year per centre. Eight clinics provide a specialised outpatient clinic for ocular GvHD. Nearly all the participating clinics prescribe ciclosporin eye drops. About ⅔ provide autologous serum eye drops, seven obtain them from external sources. Overall approx. 125 - 140 children were examined in 2016.

CONCLUSIONS

Due to the potential severity of ocular GvHD with immobilisation of the patients and the imminent loss of sight, further improvements in eye care are required. For example, offers such as special consultations, with expertise located close to any transplantation unit are recommended. This requires in particular ophthalmologists to participate in the patient care to enhance quality of life after allo-SCT. In summary, we conclude that the present structures are not sufficient to treat all patients suffering from ocular GvHD in Germany, but the situation has evidently improved.

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.

Antileukemia and antitumor effects of the graft-versus-host disease: a new immunovirological approach

In leukemic mice, the native host's explicit and well-defined immune reactions to the leukemia virus (a strong exogenous antigen) and to leukemia cells (pretending in their native hosts to be protected "self" elements) are extinguished and replaced in GvHD (graft-versus-host disease) by those of the immunocompetent donor cells. In many cases, the GvHD-inducer donors display genetically encoded resistance to the leukemia virus. In human patients only antileukemia and anti-tumor cell immune reactions are mobilized; thus, patients are deprived of immune reactions to a strong exogenous antigen (the elusive human leukemia-sarcoma retroviruses). The innate and adaptive immune systems of mice have to sustain the immunosuppressive effects of leukemia-inducing retroviruses. Human patients due to the lack of leukemiainducing retroviral pathogens (if they exist, they have not as yet been discovered), escape such immunological downgrading. After studying leukemogenic retroviruses in murine and feline (and other mammalian) hosts, it is very difficult to dismiss retroviral etiology for human leukemias and sarcomas. Since no characterized and thus recognized leukemogenic-sarcomagenic retroviral agents are being isolated from the vast majority of human leukemias-sarcomas, the treatment for these conditions in mice and in human patients vastly differ. It is immunological and biological modalities (alpha interferons; vaccines; adoptive lymphocyte therapy) that dominate the treatment of murine leukemias, whereas combination chemotherapy remains the main remission-inducing agent in human leukemias-lymphomas and sarcomas (as humanized monoclonal antibodies and immunotoxins move in). Yet, in this apparently different backgrounds in Mus and Homo, GvHD, as a treatment modality, appears to work well in both hosts, by replacing the hosts' anti-leukemia and anti-tumor immune faculties with those of the donor. The clinical application of GvHD in the treatment of human leukemias-lymphomas and malignant solid tumors remains a force worthy of pursuit, refinement and strengthening. Graft engineering and modifications of the inner immunological environment of the recipient host by the activation or administration of tumor memory T cells, selected Treg cells and natural killer (NKT) cell classes and cytokines, and the improved pharmacotherapy of GvHD without reducing its antitumor efficacy, will raise the value of GvHD to the higher ranks of the effective antitumor immunotherapeutical measures. Clinical interventions of HCT/HSCT (hematopoietic cell/stem cell transplants) are now applicable to an extended spectrum of malignant diseases in human patients, being available to elderly patients, who receive non-myeloablative conditioning, are re-enforced by post-transplant donor lymphocyte (NK cell and immune T cell) infusions and post-transplant vaccinations, and the donor cells may derive from engineered grafts, or from cord blood with reduced GvHD, but increased GvL/GvT-inducing capabilities (graft-versus leukemia/tumor). Post-transplant T cell transfusions are possible only if selected leukemia antigen-specific T cell clones are available. In verbatim quotation: "Ultimately, advances in separation of GvT from GvHD will further enhance the potential of allogeneic HCT as a curative treatment for hematological malignancies" (Rezvani, A.R. and Storb, R.F., Journal of Autoimmunity 30:172-179, 2008 (see in the text)). It may be added: for cure, a combination of the GvL/T effects with new targeted therapeutic modalities, as elaborated on in this article, will be necessary.

Gene therapy for β-thalassaemia: the continuing challenge

The β-thalassaemias are inherited anaemias that form the most common class of monogenic disorders in the world. Treatment options are limited, with allogeneic haematopoietic stem cell transplantation offering the only hope for lifelong cure. However, this option is not available for many patients as a result of either the lack of compatible donors or the increased risk of transplant-related mortality in subjects with organ damage resulting from accumulated iron. The paucity of alternative treatments for patients that fall into either of these categories has led to the development of a revolutionary treatment strategy based on gene therapy. This approach involves replacing allogeneic stem cell transplantation with the transfer of normal globin genes into patient-derived, autologous haematopoietic stem cells. This highly attractive strategy offers several advantages, including bypassing the need for allogeneic donors and the immunosuppression required to achieve engraftment of the transplanted cells and to eliminate the risk of donor-related graft-versus-host disease. This review discusses the many advances that have been made towards this endeavour as well as the hurdles that must still be overcome before gene therapy for β-thalassaemia, as well as many other gene therapy applications, can be widely applied in the clinic.

Ocular graft-versus-host disease after allogeneic stem cell transplantation

PURPOSE

To determine the prevalence and manifestations of ocular graft-versus-host disease (GvHD) after allogeneic stem cell transplantation (allo-SCT).

METHODS

Prospective study of 101 consecutive patients who received allo-SCT from 2004 to 2007. All patients received ophthalmologic examination for 3 months after allo-SCT, and those with ocular complaints were evaluated at 12 and 24 months thereafter. We registered ophthalmologic and hematological data, including the indication for allo-SCT, occurrence of systemic and ocular GvHDs, ocular manifestations, and various ocular treatments.

RESULTS

Over time, ocular GvHD developed in 54% of patients and consisted mainly of dry eyes and conjunctivitis, which increased in severity during follow-up; blepharitis and uveitis were less often encountered. Acute systemic GvHD, especially the involvement of mouth and skin, was strongly associated with ocular GvHD at 3 months (P = 0.000). Chronic GvHD was associated with the occurrence of ocular GvHD (P = 0.000), especially with the development of the dry eye. Although eye symptoms affecting activities of daily living were reported in 24 of 54 patients (44%) and 16 of 54 patients (30%) experienced temporary loss of visual acuity of more than 2 Snellen lines, only 1 developed permanent unilateral loss (counting fingers) because of ischemic vasculopathy. Cataract development was not encountered, and only 1 eye developed intraocular infection.

CONCLUSION

Ocular GvHD develops in a substantial part of patients after allo-SCT and decreases the activities of daily living.

Regulatory functions of TRAIL in hematopoietic progenitors: human umbilical cord blood and murine bone marrow transplantation

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) signaling pathway has selective toxicity to malignant cells. The TRAIL receptors DR4 and DR5 are expressed at low levels in human umbilical cord blood cells (3-15%) and are upregulated by incubation with the cognate ligand, triggering apoptosis in 70-80% of receptor-positive cells (P<0.001). Apoptosis is not induced in hematopoietic progenitors, as determined from sustained severe combined immunodeficiency reconstituting potential and clonogenic activity. Furthermore, elimination of dead cells after incubation with TRAIL for 72 h results in a threefold enrichment in myeloid progenitors. Exposure to TRAIL in semisolid cultures showed synergistic activity of DR4 and granulocyte/macrophage colony-stimulating factor in recruiting lineage-negative (lin(-)) and CD34(+) progenitors and in promoting the formation of large colonies. In murine bone marrow, approximately 30% of lin(-) cells express TRAIL-R2 (the only murine receptor), and the receptor is upregulated after transplantation in cycling and differentiating donor cells that home to the host marrow. However, this receptor is almost ubiquitously expressed in the most primitive (lin(-)SCA-1(+)c-kit(+)) progenitors, and stimulates the clonogenic activity of lin(-) cells (P<0.001), suggesting a tropic function after transplantation. It is concluded that TRAIL does not trigger apoptosis in hematopoietic progenitors, and upregulation of its cognate receptors under stress conditions mediates tropic signaling that supports recovery from hypoplasia.

Corticosteroids for preventing graft-versus-host disease after allogeneic myeloablative stem cell transplantation

BACKGROUND

Despite ongoing progress, acute and chronic GvHD still represent major drawbacks in the context of allogeneic myeloablative haematopoietic stem cell transplantation (HSCT) due to their high morbidity and mortality. Corticosteroids are used as first-line treatment of acute and chronic GvHD. However, their role for preventing GvHD is unclear as the published study results are controversial.

OBJECTIVES

To determine the effectiveness of corticosteroids used for the prophylaxis of GvHD in adults following allogeneic myeloablative HSCT. in improving overall survival, disease-free survival, relapse incidence, non-relapse mortality, acute GvHD grade I to IV, II to IV and III to IV, chronic GvHD, incidence of infectious complications, other adverse effects and cause of deaths.

SEARCH STRATEGY

We searched the Cochrane Haematological Malignancies Group trials register, CENTRAL (The Cochrane Library Issue 2, 2004), MEDLINE (January 1999 to February 2006), EMBASE (January 1999 to 2004), LILACS covering publications until 2004, as well as handsearched conference proceedings, including citations until 2005.

SELECTION CRITERIA

Randomised controlled trials (RCT) comparing the addition of corticosteroids to a GvHD prophylaxis regimen in adult patients having undergone allogeneic myeloablative HSCT were included into the review. All types and stages of the underlying disease as well as all types of possible HLA-matching were considered.

DATA COLLECTION AND ANALYSIS

Trial eligibility and quality assessment, data extraction and analysis were done in duplicate.

MAIN RESULTS

Five RCTs involving 604 people were included. The pooled results revealed that the addition of corticosteroids reduces statistically significant the risk for acute GvHD grade I to IV (HR 0.58; 95% CI 0.45 to 0.76) and II to IV (HR 0.69; 95% CI 0.51 to 0.92). No evidence was found that it has any clinical relevance on overall survival (HR 0.99; 95% CI 0.79 to 1.25) or disease-free survival (HR 0.95; 95% CI 0.74 to 1.23). As well, no statistically significant influence was found for acute GvHD grade III to IV (HR 0.78; 95% CI 0.52 to 1.15), chronic GvHD (HR 1.21;95% CI 0.89 to 1.65]), relapse incidence (HR 0.82; 95% CI 0.57 to 1.18) or non-relapse mortality (HR 0.88;95% CI 0.61 to 1.26). No clear evidence was found that the rate of infectious complications (under the concomitant use of antiviral or antibacterial medication or both) increases with the addition of corticosteroids. With respect to the other outcomes no significant differences could be detected.

AUTHORS' CONCLUSIONS

The addition of corticosteroids reduces the incidences of acute GvHD grade I to IV and II to IV. This reduction, however, did not show any effect on overall survival and disease-free survival. Further randomised controlled studies are needed to evaluate if the timing of steroid administration has a significant influence on the outcome; data on quality of life should be assessed systematically.

DC homeostasis in hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation is an important experimental tool and therapeutic modality. Its efficacy and toxicity are both linked to a GvH reaction that is initiated by donor T cells recognizing recipient APC, of which DC are the most potent. In most tissues recipient DC are replaced after transplantation because they turnover rapidly from BM-derived precursors. However, in a number of sites, notably the skin, recipient DC may persist and even self-renew for many months after transplantation. Understanding the homeostasis of different APC populations and how they are related to the induction of alloreactivity may help to improve the therapeutic benefit of transplantation.

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.

Comorbidity and disease status based risk stratification of outcomes among patients with acute myeloid leukemia or myelodysplasia receiving allogeneic hematopoietic cell transplantation

PURPOSE

Retrospective studies have shown similar survival among patients with acute myeloid leukemia (AML) and myelodysplasia (MDS) after nonmyeloablative compared with myeloablative conditioning. Refined risk stratification is required to design prospective trials.

PATIENTS AND METHODS

We stratified outcomes among patients with AML (n = 391) or MDS (n = 186) who received either nonmyeloablative (n = 125) or myeloablative (n = 452) allogeneic hematopoietic cell transplantation (HCT) based on comorbidities, as assessed by a HCT-specific comorbidity index (HCT-CI), as well as disease status. Patients receiving nonmyeloablative conditioning were older, more frequently pretreated, more often received unrelated grafts, and more often had HCT-CI scores of 3 compared with patients who received myeloablative conditioning.

RESULTS

Patients with HCT-CI scores of 0 to 2 and either low or high disease risks had probabilities of overall survival at 2 years of 70% and 57% after nonmyeloablative conditioning compared with 78% and 50% after myeloablative conditioning, respectively. Patients with HCT-CI scores of 3 and either low or high disease risks had probabilities of overall survival of 41% and 29% with nonmyeloablative conditioning compared with 45% and 24% with myeloablative regimens, respectively. After adjusting for pretransplantation differences, stratified outcomes were not significantly different among patients receiving nonmyeloablative compared with myeloablative conditioning, with the exception of lessened nonrelapse mortality (hazard ratio, 0.50; P = .05) in the highest risk group.

CONCLUSION

Patients with low comorbidity scores could be candidates for prospective randomized trials comparing nonmyeloablative and myeloablative conditioning regardless of disease status. Additional data are required for patients with low-risk diseases and high comorbidity scores. Novel antitumor agents combined with nonmyeloablative HCT should be explored among patients with high comorbidity scores and advanced disease.

Minor histocompatibility antigens as targets for immunotherapy using allogeneic immune reactions

Minor histocompatibility antigens (mHag) were originally identified as antigens causing graft rejection or graft-versus-host disease in human leukocyte antigen (HLA)-matched allogeneic transplantation. Molecular identification has revealed most to be major histocompatibility complex (MHC)-bound short peptide fragments encoded by genes which are polymorphic due to single nucleotide polymorphisms (SNP). Genotypic disparity of SNP between transplantation donors and recipients gives rise to mHag as non-self antigens for both the donor and the recipient. Subsequently, mHag have been explored as immunotherapeutic antigens for use against recurring hematological malignancies after allogeneic hematopoietic cell transplantation (HCT), because mHag expressed only on hematopoietic cells are considered to augment graft-versus-leukemia/lymphoma (GVL) effects without increasing the risk of life-threatening graft-versus-host disease (GVHD). Accumulating evidence suggests that T-cell responses to mHag aberrantly expressed on solid tumor cells are also involved in the eradication of sensitive tumors such as renal cell carcinomas following HCT. Over the past decade, the number of putative GVL-directed mHag has increased to a level that covers more than 30% of the Japanese patient population, so that clinical trials may now be executed in the setting of either vaccination or adoptive immunotherapy. As it is expected that immune responses to alloantigens are more powerful than to tumor antigens mostly derived from overexpressed self-proteins, mHag-based immunotherapy may lead to a new treatment modality for high-risk malignancies following allogeneic HCT.

Dendritic cell homeostasis and trafficking in transplantation

Hematopoietic cell transplantation and solid organ transplantation are definitive therapies for several otherwise fatal conditions. Post-transplant immune reactions are the major cause of morbidity after transplantation and limit the extended use of these critical therapies. Post-transplant immune complications include graft rejection by the host and injury to the host mediated by the graft. Dendritic cells (DCs), a population of professional antigen-presenting cells, are thought to be crucial in triggering primary immune responses against both the graft and the host. Here, we review studies on DC homeostasis and trafficking after transplantation, and examine the role of the host and graft DC in post-transplant immune responses. We also discuss the therapeutic implications of these studies.

In vivo selection and chemoprotection after drug resistance gene therapy in a nonmyeloablative allogeneic transplantation setting in dogs

We have previously demonstrated successful in vivo selection, chemoprotection, and modulation of donor chimerism in dogs that received myeloablative allogeneic stem cell transplantation with cells expressing the P140K mutant of the DNA repair enzyme methylguanine methyltransferase (MGMTP140K). Here, we wished to investigate whether in vivo selection, chemoprotection, and modulation of donor chimerism could also be achieved after nonmyeloablative transplantation, which could allow for less toxic transplantation regimens for patients with malignant and genetic diseases. Three dogs received a nonmyeloablative conditioning regimen and infusion of allogeneic stem cells transduced with MGMTP140K. All three dogs had stable gene marking and donor chimerism before receiving a course of O(6) -benzylguanine (O(6) BG)/1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) between days 210 and 589 after transplantation. One to four doses led to a marked increase in gene marking in all dogs. Furthermore, the transduced cells conferred chemoprotection and prevented severe neutropenia. Our results suggest that drug resistance gene therapy is feasible and safe in the nonmyeloablative transplantation setting.

EBV-related disease following haematopoietic stem cell transplantation with reduced intensity conditioning

The use of reduced intensity regimens has decreased early mortality following stem cell transplantation. However, the increased immunosuppression following these protocols results in profound and often prolonged lymphopenia, resulting in an increased incidence of viral reactivation. We and others have observed a high incidence of EBV viraemia and post-transplant lymphoproliferative disease (PTLD) following reduced-intensity conditioning regimens, reflecting the delayed recovery of EBV-specific immunity after such transplants. The clinical and histological features at presentation are similar to that seen after conventional intensity conditioning. Given the increasing use of reduced intensity conditioning (RIC) transplants, we review the risk factors for EBV related disease following transplantation with RIC, the potential for pre-emptive therapy of PTLD based on monitoring EBV viraemia and management options in such patients.

Histological evaluation of acute mucocutaneous graft-versus-host disease in nonmyeloablative hematologic stem cell transplants with an observation predicting an increased risk of progression to chronic graft-versus-host disease

The incorporation of nonmyeloablative conditioning prior to the transplantation of allogeneic hematopoietic cells has emerged as an alternative to myeloablative chemo- and/or radiotherapy for the treatment of hematologic malignancies. Graft-versus-host disease (GVHD) remains a significant complication of both types of hematopoietic cell transplantation (HCT). The clinical phenomenon of late-onset (>100 days after HCT) acute GVHD recently has been described following nonmyeloablative allogeneic transplantation (NMAT); however, there has been no detailed histologic description of acute GVHD in this setting. We sought to characterize the histopathologic features of acute GVHD following NMAT. The clinical and pathologic features of 20 patients with acute GVHD following NMAT over a three-year period were reviewed. Late-onset acute GVHD was diagnosed in 10 of 20 patients with a mean onset of 109.8 days (range 8-410 days); eight (40%) of these subjects with acute GVHD also had concomitant histologic features of chronic lichenoid chronic GVHD. Cases with "composite" histologic features were more likely to progress to fully developed chronic GVHD compared to those without this finding (87.5% vs 25%, P < 0.01). These findings support the existence of late-occurring mucocutaneous GVHD after NMAT and define a strong clinical/laboratory predictor for the subsequent development of chronic GVHD. Patients with composite skin GVHD may benefit from an earlier, more aggressive immunosuppressive interventional strategy.

Intravenous Busulfan and Melphalan, Tacrolimus, and Short-Course Methotrexate Followed by Unmodified HLA-Matched Related or Unrelated Hematopoietic Stem Cell Transplantation for the Treatment of Advanced Hematologic Malignancies

Results of allogeneic hematopoietic stem cell transplantation (HCT) to treat advanced leukemia or myelodysplastic syndrome (MDS) remain poor due to excessive relapse and transplant-related mortality. To improve transplant outcome in this patient population, 43 patients (median age, 46.1 years) with high-risk or advanced lymphoid (n = 5) or myeloid malignancy (n = 38) were prospectively enrolled on a pilot trial of cytoreduction with intravenous busulfan and melphalan followed by an unmodified HLA-A, -B, and -DRbeta1-matched related (n = 18) or unrelated (n = 25) HCT. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus and methotrexate. Thirty-four patients had > or = 5% blasts at the time of HCT; 12 of these had > 20% blasts. Seventeen patients had unfavorable cytogenetics, 8 patients underwent transplantation for secondary MDS or acute myelogenous leukemia, and 4 patients had relapsed after a previous allogeneic transplantation. Although mucositis was the most significant regimen-related toxicity, requiring the addition of folinic acid rescue and failure to receive all 4 doses of methotrexate in 23 patients, the nonrelapse mortality at 30 and 100 days was low at 0% and 16%, respectively. The cumulative incidence of grade II-IV acute GVHD was 24%, and that of extensive chronic GVHD was 7%. With a minimum follow-up of 18 months, the estimated 3-year overall survival is 37% and the estimated disease-free survival (DFS) is 33%. For 18 patients with MDS (< or = RAEB-2) or high-risk myeloproliferative disorder, the estimated 3 year DFS is 61%. These data demonstrate the curative potential of this regimen in patients with high-risk myeloid malignancies.

DC-based vaccine loaded with acid-eluted peptides in acute myeloid leukemia: the importance of choosing the best elution method

Tumor-associated peptides isolated by acid elution are frequently used for therapeutic immunization against various tumors both in mice and in humans. In acute myeloid leukemia (AML), the frequent accessibility of a large tumor burden allows for extraction of peptides from leukemia cells by using either citrate-phosphate (CP) or trifluoroacetic acid (TFA) buffer. To develop an optimal immunotherapeutic protocol for AML patients, we evaluated both in mice and in humans, the immunogenicity of peptides eluted from leukemia cells with the two acids (TFA or CP). Although ex vivo studies in mice showed that both prophylactic immunizations with mature dendritic cells (DC) loaded with TFA-peptides (DC/TFA), or CP-peptides (DC/CP), were able to stimulate specific antileukemia immune responses, only vaccination with DC/TFA was able to prevent leukemia outgrowth. Moreover, in humans, only DC/TFA generated significant antileukemia CD4(+) and cytotoxic CD8(+) T cell responses in vitro. In summary, these data demonstrate that the choice of the acid elution procedure to isolate immunogenic peptides strongly influences the efficacy of the antileukemia immune responses. These finding raise essential considerations for the development of immunotherapeutic protocols for cancer patients. In our model, our results argue for the use of the TFA elution method to extract immunogenic AML-associated peptides.

MiHA reactive CD4 and CD8 T-cells effect resistance to hematopoietic engraftment following reduced intensity conditioning

Reduced intensity conditioning (RIC) prior to allogeneic hematopoietic cell transplantation (HCT) has shown promise in lowering the incidence of post-transplant complications including infection and graft-versus-host disease. T-cell-mediated graft rejection, however, remains a crucial factor in determining how 'mild' a level of immunosuppression can be administered. Understanding the kinetics of resistance responses as well as the role of CD4+ and CD8+ T cells underlies the development of protocols to circumvent resistance and support hematopoietic engraftment. In these studies, a major histocompatibility complex (MHC)-matched/minor histocompatibility antigen (MiHA) disparate RIC HCT model was developed in which resistance against donor hematopoietic progenitors as well as mature peripheral blood cells could be assessed. Interestingly, resistance was diminished in the absence of either host CD4+ or CD8+ T cells. However, its impairment was more severe in CD4-/- mice where resistance was not detected. Host CD4+ T cells were required for optimal expansion of specific (H60) T-cell receptor (TCR) expressing host anti-donor MiHA reactive CD8+ T cells following HCT. These observations demonstrate a critical role for host CD4+ T cells in resistance against MiHA disparate HCT. This RIC HCT resistance model will be useful for the analysis of the barrier to engraftment mediated by host T cells and the development of strategies to support engraftment.

Chimerism and outcomes after allogeneic hematopoietic cell transplantation following nonmyeloablative conditioning

Allogeneic hematopoietic cell transplantation (HCT) following nonmyeloablative conditioning has been extensively evaluated in patients with hematologic malignancies who are ineligible for conventional HCT because of age or medical comorbidities. Nonmyeloablative regimens have led to an initial state of mixed hematopoietic chimerism defined as coexistence of donor- and host-derived hematopoiesis. While nonmyeloablative regimens have been associated with reduced regimen-related toxicities in comparison with conventional myeloablative conditioning, graft rejection, graft-versus-host disease (GVHD), and disease progression have remained significant challenges. In this article, after briefly introducing current techniques for chimerism assessment, we describe factors affecting donor chimerism levels after nonmyeloablative conditioning, and then review data suggesting that chimerism assessment early after HCT might help identify patients at risk for graft rejection, GVHD and relapse/progression. Finally, we discuss how these observations have opened the way to further research protocols evaluating manipulation of postgrafting immunosuppression, and/or infusion of donor immune cells.

Allogeneic T cells induce rapid CD34+ cell differentiation into CD11c+CD86+ cells with direct and indirect antigen-presenting function

Dendritic cells (DCs) derive from CD34+ cells or monocytes and stimulate alloimmune responses in transplantation. We hypothesized that the interaction between CD34+ cells and allogeneic T cells would influence the function of hematopoietic stem cells (HSCs). Cord blood (CB) CD34+ cells proliferated briskly in response to allogeneic, but not autologous, T cells when mixed with irradiated T cells for 6 days in vitro. This proliferation was significantly inhibited by an anti-HLA class II monoclonal antibody (mAb), by an anti-TNFalpha mAb, or by CTLA4-Ig. Allogeneic T cells induced the differentiation of CD34+ progenitors into cells with the morphology of dendritic monocytic precursors and characterized by the expression of HLA-DR, CD86, CD40, CD14, and CD11c, due to an endogenous release of TNFalpha. Cotransplantation of CD34+ cells with allogeneic T cells into nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice resulted in a greater engraftment of myeloid CD1c+ dendritic cells compared with cotransplantation with autologous T cells. In vitro, CD34+ cell-derived antigen-presenting cells (APCs) were functionally capable of both direct and indirect presentation of alloantigens. Based on these findings, we hypothesize that in HSC transplantation the initial cross talk between allogeneic T cells and CD34+ cells may result in the increased generation of APCs that can present host alloantigens and possibly contribute to the development of graft-versus-host disease.

Comparative outcome of reduced intensity and myeloablative conditioning regimen in HLA identical sibling allogeneic haematopoietic stem cell transplantation for patients older than 50 years of age with acute myeloblastic leukaemia: a retrospective survey from the Acute Leukemia Working Party (ALWP) of the European group for Blood and Marrow Transplantation (EBMT)

Results of reduced intensity conditioning regimen (RIC) in the HLA identical haematopoietic stem cell transplantation (HSCT) setting have not been compared to those after myeloablative (MA) regimen HSCT in patients with acute myeloblastic leukaemia (AML) over 50 years of age. With this aim, outcomes of 315 RIC were compared with 407 MA HSCT recipients. The majority of RIC was fludarabine-based regimen associated to busulphan (BU) (53%) or low-dose total body irradiation (24%). Multivariate analyses of outcomes were used adjusting for differences between both groups. The median follow-up was 13 months. Cytogenetics, FAB classification, WBC count at diagnosis and status of the disease at transplant were not statistically different between the two groups. However, RIC patients were older, transplanted more recently, and more frequently with peripheral blood allogeneic stem cells as compared to MA recipients. In multivariate analysis, acute GVHD (II-IV) and transplant-related mortality were significantly decreased (P=0.01 and P<10(-4), respectively) and relapse incidence was significantly higher (P=0.003) after RIC transplantation. Leukaemia-free survival was not statistically different between the two groups. These results may set the grounds for prospective trials comparing RIC with other strategies of treatment in elderly AML.

Allogeneic hematopoietic stem-cell transplantation in AML and MDS using myeloablative versus reduced-intensity conditioning: the role of dose intensity

Allogeneic stem-cell transplantation (SCT) with both myeloablative and reduced-intensity conditioning (RIC) is an effective therapy in AML/MDS. However, the relative merits of each may differ in different settings. To define the role of dose intensity, we analyzed SCT outcomes of 112 consecutive patients with AML/MDS. A total of 45 patients met eligibility criteria for standard myeloablative conditioning and were given intravenous-busulfan (12.8 mg/kg) and cyclophosphamide (ivBuCy). A total of 67 noneligible patients were given RIC with fludarabine and intravenous-busulfan (6.4 mg/kg, FB2, n=41) or a modified myeloablative regimen with fludarabine and myeloablative doses of intravenous-busulfan (12.8 mg/kg, FB4, n=26). The overall survival (OS) at 2 years was 50, 49 and 47% after ivBuCy, FB4 and FB2, respectively (P=NS). Nonrelapse mortality was higher after ivBuCy, 22 vs 8% (P=0.05), but relapse rates were lower. Active disease at SCT was the most significant predictor of reduced survival in multivariable analysis (HR 4.5, P=0.0001). Myeloablative and RIC regimens had similar outcomes when leukemia was in remission at SCT; however, patients with active disease could only be salvaged by myeloablative conditioning. Among the latter, OS was 45% after ivBuCy but no FB2 recipient survived (P=0.02). Patients with active disease, ineligible for standard myeloablation, could tolerate modified myeloablation well; however, long-term outcome cannot be determined yet.

Allogeneic hematopoietic cell transplantation following nonmyeloablative conditioning as treatment for hematologic malignancies and inherited blood disorders

Allogeneic hematopoietic cell transplantation (HCT) after myeloablative conditioning regimens has been an effective treatment for many patients with hematologic malignancies or inherited blood disorders. Unfortunately, such regimens have been associated with significant toxicity, limiting their use to otherwise healthy, relatively young patients. In an attempt to extend treatment by allogeneic HCT to older patients and those with comorbid conditions, several groups of investigators have developed reduced-intensity or truly nonmyeloablative conditioning regimens, lacking such toxicity. Analogous to conventional regimens, reduced-intensity regimens both eliminated host-versus-graft (rejection) reactions and produced major anti-tumor effects. In contrast, nonmyeloablative regimens have relied on optimizing both pre-and posttransplant immunosuppression to overcome host-versus-graft reactions, while anti-tumor responses have depended mainly on immune-mediated graft-versus-tumor effects. In this review, we define reduced-intensity and truly nonmyeloablative regimens, describe the preclinical development and clinical application of a very low intensity nonmyeloablative regimen, and review results with reduced-intensity regimens in patients with hematologic malignancies or inherited blood disorders.

Current status of hematopoietic stem cell transplantation after nonmyeloablative conditioning

PURPOSE OF REVIEW

Allogeneic hematopoietic stem cell transplantation was originally developed as a form of rescue from high-dose chemoradiotherapy, which is given both to eradicate malignancy and provide sufficient immunosuppression for allogeneic engraftment. However, it was observed that allogeneic immunocompetent cells transplanted with the stem cells, or arising from them, mediated therapeutic antitumor effects independent of the action of the high-dose therapy. This was termed a graft-versus-tumor effect. This has prompted the recent development of nonmyeloablative conditioning regimens for allogeneic hematopoietic stem cell transplantation that have opened the way to include elderly patients and those with comorbid conditions.

RECENT FINDINGS

Recent retrospective studies comparing hematopoietic stem cell transplantation after myeloablative or nonmyeloablative regimens suggested that the use of nonmyeloablative conditioning might be associated with lower transplant-related toxicity, lower nonrelapse mortality, and at least similar intermediate-term progression-free survival.

SUMMARY

Hematopoietic stem cell transplantation after nonmyeloablative conditioning might become the procedure of choice also for younger patients. Phase 3 studies are needed to determine outcomes for different diseases and age groups.