Characterization of T cell repertoire in patients with graft-versus-leukemia after donor lymphocyte infusion

Donor lymphocyte infusion in Acute Myeloid Leukemia

Donor lymphocyte infusion (DLI) is an important treatment modality in the management of relapsed hematological malignancies after allogeneic hematopoietic cell transplantation (allo-HCT). Donor T lymphocytes can be used in a therapeutic, pre-emptive or prophylactic manner in an attempt to stimulate a graft versus leukemia (GVL) effect and eradicate residual disease or even prevent relapse in a high-risk setting. DLIs are not without complications, however, graft versus host disease (GVHD) in particular. Data to date is limited to retrospective and small prospective studies. This review summarizes the available literature on approaches to managing relapse, dosing and timing of DLI, complications and potential future therapies.

Healthy-like CD4+ Regulatory and CD4+ Conventional T-Cell Receptor Repertoires Predict Protection from GVHD Following Donor Lymphocyte Infusion

Donor lymphocyte infusion (DLI) can (re-)induce durable remission in relapsing patients after allogeneic hematopoietic stem-cell transplantation (alloHSCT). However, DLI harbors the risk of increased non-relapse mortality due to the co-occurrence of graft-versus-host disease (GVHD). GVHD onset may be caused or accompanied by changes in the clonal T-cell receptor (TCR) repertoire. To investigate this, we analyzed T cells in a cohort of 21 patients receiving DLI after alloHSCT. We performed deep T-cell receptor β (TRB) sequencing of sorted CD4+CD25+CD127low regulatory T cells (Treg cells) and CD4+ conventional T cells (Tcon cells) in order to track longitudinal changes in the TCR repertoire. GVHD following DLI was associated with less diverse but clonally expanded CD4+CD25+CD127low Treg and CD4+ Tcon TCR repertoires, while patients without GVHD exhibited healthy-like repertoire properties. Moreover, the diversification of the repertoires upon GVHD treatment was linked to steroid-sensitive GVHD, whereas decreased diversity was observed in steroid-refractory GVHD. Finally, the unbiased sample analysis revealed that the healthy-like attributes of the CD4+CD25+CD127low Treg TCR repertoire were associated with reduced GVHD incidence. In conclusion, CD4+CD25+CD127low Treg and CD4+ Tcon TRB repertoire dynamics may provide a helpful real-time tool to improve the diagnosis and monitoring of treatment in GVHD following DLI.

Clonal expansion of CD8+ T cells reflects graft-versus-leukemia activity and precedes durable remission following DLI

GVL activity in patients receiving DLI for relapse after allogeneic hematopoietic stem cell transplantation is associated with clonal expansion of CD8⁺ T cells.

Absence of clonal expansion of the CD8⁺TRB repertoire after DLI predicts relapse at a median time of 11.2 months before clinical diagnosis.

Donor lymphocyte infusion (DLI) is a standard of care for relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation. Currently it is poorly understood how and when CD8⁺ αβ T cells exert graft-versus-leukemia (GVL) activity after DLI. Also, there is no reliable biomarker to monitor GVL activity of the infused CD8⁺ T cells. Therefore, we analyzed the dynamics of CD8⁺ αβ T-cell clones in patients with DLI. In this prospective clinical study of 29 patients, we performed deep T-cell receptor β (TRB ) sequencing of sorted CD8⁺ αβ T cells to track patients’ repertoire changes in response to DLI. Upon first occurrence of GVL, longitudinal analyses revealed a preferential expansion of distinct CD8⁺TRB clones (n = 14). This did not occur in samples of patients without signs of GVL (n = 11). Importantly, early repertoire changes 15 days after DLI predicted durable remission for the 36-month study follow-up. Furthermore, absence of clonal outgrowth of the CD8⁺TRB repertoire after DLI was an early biomarker that predicted relapse at a median time of 11.2 months ahead of actual diagnosis. Additionally, unbiased sample analysis regardless of the clinical outcome revealed that patients with decreasing CD8⁺TRB diversity at day 15 after DLI (n = 13) had a lower relapse incidence (P = .0040) compared with patients without clonal expansion (n = 6). In conclusion, CD8⁺TRB analysis may provide a reliable tool for predicting the efficacy of DLI and holds the potential to identify patients at risk for progression and relapse after DLI.

Mapping the evolution of T cell states during response and resistance to adoptive cellular therapy

To elucidate mechanisms by which T cells eliminate leukemia, we study donor lymphocyte infusion (DLI), an established immunotherapy for relapsed leukemia. We model T cell dynamics by integrating longitudinal, multimodal data from 94,517 bone marrow-derived single T cell transcriptomes in addition to chromatin accessibility and single T cell receptor sequencing from patients undergoing DLI. We find that responsive tumors are defined by enrichment of late-differentiated T cells before DLI and rapid, durable expansion of early differentiated T cells after treatment, highly similar to "terminal" and "precursor" exhausted subsets, respectively. Resistance, in contrast, is defined by heterogeneous T cell dysfunction. Surprisingly, early differentiated T cells in responders mainly originate from pre-existing and novel clonotypes recruited to the leukemic microenvironment, rather than the infusion. Our work provides a paradigm for analyzing longitudinal single-cell profiling of scenarios beyond adoptive cell therapy and introduces Symphony, a Bayesian approach to infer regulatory circuitry underlying T cell subsets, with broad relevance to exhaustion antagonists across cancers.

Persistent donor derived Vδ4 T cell clones may improve survival for recurrent T cell acute lymphoblastic leukemia after HSCT and DLI

The outcome for T-cell acute lymphoblastic leukemia (T-ALL) in relapse after hematopoietic stem cell transplantation (HSCT) is quite poor, while, both donor lymphocytes infusion (DLI) and adoptively infusion of γδ T cells in leukemia patients after HSCT have demonstrated good results in prolonging survival time of patients. Here, we reported a T-ALL case who experienced three relapses and received HSCT and DLI with an overall survival (OS) time lasting for more than seven years. Based on our previous identification of a leukemic and reactive clone in this patient, continual γδ T cell repertoire monitoring affirmed that the same Vδ5 leukemic clone existed in most samples from the patient, particularly including a sample taken at the time of the third T-ALL relapse, while it could not be detected in the donor sample. In addition, an identical Vδ4 monoclonal T cell that proliferated in the recipient for several years was confirmed to come from the donor graft, and its expression level significantly increased in third leukemia recurrence. These results indicate that clonally expanded Vδ4 T cells may represent a reconstituted γδ T cell repertoire after HSCT, which also hints to a relatively better outcome for this case. Based on this case study, we recommend DLI should be as a treatment strategy for patients who achieve CR or relapse from HSCT. Moreover, dynamically monitoring the TCR repertoire in patients who receive HSCT will benefit in supervising of malignant clone evolution and residue, identifying T cell clones mediate anti-infection, GvHD or GvL.

Donor lymphocytes expressing the herpes simplex virus thymidine kinase suicide gene: detailed immunological function following add-back after haplo-identical transplantation

BACKGROUND AIMS

Haplo-identical hematopoietic stem cell transplantation (HSCT) with add-back of donor lymphocytes expressing the herpes simplex virus thymidine kinase suicide gene (TK cells) is one of the most widely applied promising new gene therapy approaches. However, the immunological status of added-back TK cells after HSCT has yet to be well characterized.

METHODS

We investigated TK cells through the use of flow cytometry, T-cell receptor (TCR) Vβ repertoire spectratyping and linear amplification-mediated polymerase chain reaction followed by insertion site analysis in a patient enrolled in our clinical trial.

RESULTS

A comparison of onset with remission of acute graft-versus-host disease confirmed that TK cells were predominantly eliminated and that proliferative CD8(+) non-TK cells were also depleted in response to ganciclovir administration. The TCR Vβ-chain repertoire of both TK cells and non-TK cells markedly changed after administration of ganciclovir, and, whereas the TCR repertoire of non-TK cells returned to a normal spectratype long after transplantation, that of TK cells remained skewed. With the long-term prophylactic administration of acyclovir, TK cells oligoclonally expanded and the frequency of spliced variants of TK cells increased. Known cancer-associated genes were not evident near the oligoclonally expanded herpes simplex virus (HSV)-TK insertion sites.

CONCLUSIONS

We demonstrate obvious differences in immunological status between TK cells and non-TK cells. In addition, we speculate that long-term prophylactic administration of acyclovir increases the risk of oligoclonal expansion of spliced forms of TK cells.

Advances in haplo-identical stem cell transplantation in adults with high-risk hematological malignancies

Allogeneic bone marrow transplant is a life-saving procedure for adults and children that have high-risk or relapsed hematological malignancies. Incremental advances in the procedure, as well as expanded sources of donor hematopoietic cell grafts have significantly improved overall rates of success. Yet, the outcomes for patients for whom suitable donors cannot be found remain a significant limitation. These patients may benefit from a hematopoietic cell transplant wherein a relative donor is fully haplotype mismatched. Previously this procedure was limited by graft rejection, lethal graft-versus-host disease, and increased treatment-related toxicity. Recent approaches in haplo-identical transplantation have demonstrated significantly improved outcomes. Based on years of incremental pre-clinical research into this unique form of bone marrow transplant, a range of approaches have now been studied in patients in relatively large phase II trials that will be summarized in this review.

Leukemia Associated Clonal Expansion of TCR Vβ Subfamily T Cells

The analysis of the T cell receptor (TCR) Vbeta repertoire is one of the most sensitive methods to identify the clonal expansion T cells which respond to tumor associated antigens. Recently, studies have focused on clonally expanded T cells from patients or normal donors induced by leukemia associated antigens in vivo or in vitro. Understanding such clonality and restricted usage of TCR Vbeta repertoire of leukemia-associated expanded T cells may be useful for the design of new immuno-therapeutic strategy for leukemia.

Clinical Implications of T Cell Receptor Repertoire Analysis after Allogeneic Stem Cell Transplantation

Stem cell transplantation (SCT) constitutes a major challenge to the immune system. Long-term impairment of immunity against various common infectious stimuli leads to increased susceptibility to infectious diseases; in contrast, an immune response against the recipient may cause the devastating graft-versus-host disease (GvHD). Recovery of the immune system (both qualitative and quantitative) after SCT is perhaps the most important factor in determining the clinical outcome. Consequently, immune reconstitution has been extensively studied using different approaches, including quantitative analysis of immune cells as well as their phenotypic characterization. Analysis of diversity and clonality is an important tool in determining competence of the immune system, assuming that a broad diversity assures efficient response to different stimuli and clonal dominance reflects ongoing, potentially relevant immune responses. Detailed analysis of the immune repertoire through the flow cytometric and molecular study of the T cell receptor repertoire has been applied to gain quantitative and qualitative insights about the T cell immune competence and responsiveness. After SCT, a contraction of the T cell pool and a reduction in T cell receptor diversity is clearly associated with clinical immunodeficiency. Reconstitution of the immune system is often characterized by dominance of oligoclonal T cell populations, reflecting specific antigen-driven immune responses. Detailed characterization of T lymphocytes by T cell receptor analysis is possible, and may lead to the identification of individual clones involved in specific immune reactions, such as alloresponses in GvHD, the closely related graft-versus-leukemia effect and opportunistic viral agents such as CMV or EBV.

T-cell receptor repertoire usage in hematologic malignancies

Over the last few years several studies have addressed the possible influence of different immune mechanisms on the evolution of hematologic malignancies. More specifically, a fundamental role of reactive T-cells has now been demonstrated in the pathogenesis of many of these disorders as well as in the typical immunological milieu observed after stem cell transplantation in patients affected by these malignancies. In this context the study of the T-cell receptor (TCR) repertoire performed by different techniques, such as for instance flow cytometry and spectratyping, has undoubtedly provided a fundamental contribution. More recently, these seminal observations have even opened new potential therapeutic avenues based on the employment of adoptive T-cells somehow engineered toward potential neoplastic targets. This review will run through the most relevant studies which have tried to dissect the TCR repertoire usage in patients with different hematologic malignancies, especially focusing on the possible pathogenetic and therapeutic implications.

Multiple myeloma patients at peripheral blood stem cell harvest: restricted usage of TCR beta variable families

The immune systems of multiple myeloma patients are suppressed by the disease itself, and this immunosuppression is further enhanced by standard therapies. The aim of our study was to evaluate the effects of initial chemotherapy and a peripheral blood mobilisation regimen on T-cell population diversity. Reverse transcription-polymerase chain reaction (RT-PCR) with a new set of primers, in combination with capillary electrophoresis, was established. The methodology was used to analyse the relative expression of 27 T-cell receptor beta variable gene families (BV families) in multiple myeloma patients undergoing peripheral blood stem cell harvest. We found that the overall BV family usage in these patients was restricted; the relative expression of 10 BV families was significantly depressed in patients compared to healthy donors. These findings demonstrate that the preparative regimen for autologous stem cell transplantation affects the T-cell population in terms of the restriction of its T-cell receptor diversity.

Graft-versus-leukemia antigen CML66 elicits coordinated B-cell and T-cell immunity after donor lymphocyte infusion

PURPOSE

The target antigens of graft-versus-leukemia that are tumor associated are incompletely characterized.

EXPERIMENTAL DESIGN

We examined responses developing against CML66, an immunogenic antigen preferentially expressed in myeloid progenitor cells identified from a patient with chronic myelogenous leukemia who attained long-lived remission following CD4+ donor lymphocyte infusion (DLI).

RESULTS

From this patient, CML66-reactive CD8+ T-cell clones were detected against an endogenously presented HLA-B*4403-restricted epitope (HDVDALLW). Neither CML66-specific antibody nor T-cell responses were detectable in peripheral blood before DLI. However, by 1 month after DLI, CD8+ T cells were present in peripheral blood and at 10-fold higher frequency in marrow. Subsequently, plasma antibody to CML66 developed in association with disease remission. Donor-derived CML66-reactive T cells were detected at low levels in vivo in marrow before DLI by ELISpot and by a nested PCR-based assay to detect clonotypic T-cell receptor sequences but not in blood of the patient pre-DLI nor of the graft donor.

CONCLUSIONS

CD4+ DLI results in rapid expansion of preexisting marrow-resident leukemia-specific donor CD8+ T cells, followed by a cascade of antigen-specific immune responses detectable in blood. Our single-antigen analysis thus shows that durable posttransplant tumor immunity is directed in part against nonpolymorphic overexpressed leukemia antigens that elicit coordinated cellular and humoral immunity.

NCI First International Workshop on The Biology, Prevention, and Treatment of Relapse After Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on the Biology Underlying Recurrence of Malignant Disease following Allogeneic HSCT: Graft-versus-Tumor/Leukemia Reaction

The success of allogeneic hematopoietic stem cell transplantation (HSCT) depends on the infusion of benign stem cells as well as lymphocytes capable of participating in a graft-versus-tumor/leukemia (GVL) reaction. Clinical proof of concept is derived from studies showing increased relapse after the infusion of lymphocyte depleted hematopoietic grafts as well as the therapeutic efficacy of donor lymphocyte infusions without chemotherapy to treat relapse in some diseases. Despite this knowledge, relapse after allogeneic HSCT is common with rates approaching 40% in those with high-risk disease. In this review, we cover the basic biology and potential application to exploit adaptive T cell responses, minor histocompatibility antigens, contraction and suppression mechanisms that hinder immune responses, adaptive B cell responses and innate NK cell responses, all orchestrated in a GVL reaction. Optimal strategies to precisely balance immune responses to favor GVL without harmful graft-versus-host disease (GVHD) are needed to protect against relapse, treat persistent disease and improve disease-free survival after HSCT.

Induction of tumor immunity following allogeneic stem cell transplantation

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

Early recovery of CD4 T cell receptor diversity after "lymphoablative" conditioning and autologous CD34 cell transplantation

T cell diversity posttransplantation is thought to be severely restricted, based on T cell receptor beta-chain immunophenotyping or spectratyping. Using beta-chain sequencing, we studied CD4 T cell diversity in 2 adult patients undergoing "lymphoablative" conditioning with cyclophosphamide (Cy), total body irradiation (TBI), and antithymocyte globulin (ATG) and autologous transplantation of hematopoietic cells depleted of T cells by enrichment for CD34 cells. The indication for the transplantation was systemic sclerosis (SSc) or multiple sclerosis (MS). Pretransplantation, the estimated number of distinct beta chains (the minimum number of CD4 T cell clones) in the 2 patients was 600,000 to 700,000, similar to the number in a healthy control. This number was 200,000 to 500,000 at 1 month posttransplantation and 400,000 to 1,600,000 at 12 months posttransplantation. In conclusion, the number of T cells early after lymphoablative conditioning and autologous CD34 cell transplantation may be more diverse than previously appreciated, possibly because many T cell clones survive the conditioning or are reinfused with the graft. Thus, the therapy may not be completely T cell lymphoablative.

Immunotherapy of AML

The applications of chemotherapy for the treatment of AML have been unchanged over the past three decades, with only 30% of patients demonstrating disease-free survival (DFS) [118]. Despite achieving CR following induction chemotherapy, the majority of patients relapse and succumb to their disease [6]. In view of the limitations encountered by cytarabine/anthracycline based regimes, attention has shifted to immunotherapy as a means to treat AML and provide significant long-term DFS. This chapter will discuss the role of the immune system and recent advances in immunotherapy for the treatment of AML, focusing on cellular and non-cellular approaches.

Standardized analysis for the quantification of Vbeta CDR3 T-cell receptor diversity

Assessment of the diversity of the T-cell receptor (TCR) repertoire is often determined by measuring the frequency and distribution of individually rearranged TCRs in a population of T cells. Spectratyping is a common method used to measure TCR repertoire diversity, which examines genetic variation in the third complementarity-determining region (CDR3) region of the TCR Vbeta chain using RT-PCR length-distribution analysis. A variety of methods are currently used to analyze spectratype data including subjective visual measures, qualitative counting measures, and semi-quantitative measures that compare the original data to a standard, control data set. Two major limitations exist for most of these approaches: data files become very wieldy and difficult to manage, and current analytic methods generate data which are difficult to compare between laboratories and across different platforms. Here, we introduce a highly efficient method of analysis that is based upon a normal theoretical Gaussian distribution observed in cord blood and recent thymic emigrants. Using this analysis method, we demonstrate that PBMC obtained from patients with various diseases have skewed TCR repertoire profiles. Upon in vitro activation with anti-CD3 and anti-CD28 coated beads (Xcyte Dynabeads) TCR diversity was restored. Moreover, changes in the TCR repertoire were dynamic in vivo. We demonstrate that use of this streamlined method of analysis in concert with a flexible software package makes quantitative assessment of TCR repertoire diversity straightforward and reproducible, enabling reliable comparisons of diversity values between laboratories and over-time to further collaborative efforts. Analysis of TCR repertoire by such an approach may be valuable in the clinical setting, both for prognostic potential and measuring clinical responses to therapy.

The TCR Vbeta repertoire usage of T-cells from cord blood induced by chronic myelogenous leukemia associated antigen

Understanding the clonality and restricted usage of the TCR Vbeta repertoire of expanded T-cells induced by the chronic myelogenous leukemia (CML) associated antigen may be useful in helping design new immunotherapeutic strategies specifically for CML. T-cells from cord blood that had been stimulated by different stimulators (IL-2, PHA, CML cells, K562 cells and bcr-abl peptide) were amplified in vitro by liquid T-cell culture and the mixed lymphocyte and tumor cell culture (MLTC) method. By using the RT-PCR, the CDR3 segments of 24 variable region genes of TCR beta was analyzed in T-cells from 22 cases of cord blood before and after T-cell culture, to observe the usage of TCR Vbeta repertoire. The PCR products were further labeled with fluorescence and analyzed by the Genescan technique for the CDR3 size, to evaluating clonality of the detectable TCR Vbeta T-cells. Only a part of 24 Vbeta subfamily T-cells (3-15 subfamilies) could be detected, however, all of the 24 TCR Vbeta subfamily of T-cells were detected after in vitro culture with PHA or IL-2+anti-CD3 antibody. The number of expressed TCR Vbeta subfamilies was gradually reduced by prolonging the time of culture with CML-associated antigens. The restricted expression of TCR Vbeta subfamilies and oligoclonal expansion of Vbeta21 T-cells were found in cultured T-cells induced by CML cells, K562 cells or bcr-abl peptide. In conclusion, T-cells from cord blood may have the potential capability of proliferation in different TCR Vbeta subfamily T-cells, and the ability for restricted expression and clonal expansion, when T-cells were induced by CML associated antigen.

Evidence for involvement of clonally expanded CD8+ T cells in anticancer immune responses in CLL patients following nonmyeloablative conditioning and hematopoietic cell transplantation

We have analyzed the clonotype composition of CD8+ T cells following nonmyeloablative (NMA) conditioning and hematopoietic cell transplantation (HCT), of patients with chronic lymphocytic leukemia (CLL). Consecutive analyses of blood samples taken up to 2 years following HCT, demonstrated that CD8+ T-cell clonality was highly dynamic in the early phases after HCT, but became more stable after 4-5 months. Moreover, donor lymphocyte infusion (DLI) given for disease progression in one of the patients led to establishment of recurrent as well as new T-cell clonotypes. This coincided with disease remission, strongly suggesting that these T cells were engaged with anti-CLL cytotoxicity. To examine the functional capacity of stable clonally expanded T cells after HCT, CD8+ T cells isolated post-transplant from the recipients were stimulated ex vivo with CLL cells and subsequently analyzed by FACS for surface expression of the marker for cytotoxic activity, CD107a. Stimulation with CLL cells indeed led to surface expression of CD107a, and clonotype analyses of sorted cells demonstrated that CD107a positive T cells were stably expanded following HCT. Our data suggest that clonally expanded CD8+ T-cell clones participate in the ongoing T-cell response against CLL cells following HCT with NMA conditioning.

GMP production and testing of Xcellerated T Cells for the treatment of patients with CLL

BACKGROUND

Pre-clinical studies suggest Xcellerated T Cells have the potential to produce a potent anti-tumor effect, restore broad immune function and reduce the risk of infectious complications in patients with CLL. Unlike other cancer settings, T cells constitute only a small fraction of CLL patients' PBMC. To generate large numbers of Xcellerated T Cells of high purity from CLL patients' PBMC, a reproducible, streamlined and cost-effective good manufacturing process (GMP) is required.

METHODS

The 10-L volume Wave Bioreactor-based Xcellerate III Process using Xcyte Dynabeads in a single custom 20-L Cellbag container was adapted, qualified and implemented for GMP operations.

RESULTS

For n=17 CLL patients, starting with approximately 1.34 x 10(9) CD3+ T cells at 6.8+/-7.5% purity in the PBMC leukapheresis products, using the 10-L volume Wave Bioreactor-based Xcellerate III Process, it was feasible to manufacture 137.0+/-34.3 x 10(9) Xcellerated T Cells at 98.5+/-1.0% CD3+ T-cell purity. An average 400-fold clearance of malignant B cells was documented during the manufacturing process. The Xcellerated T Cells produced from the Xcellerate III Process exhibited high in vitro biologic activity and have their T-cell receptor repertoire restored to a normal diversity. In-process T-cell activation was reproducibly robust, as measured by increase in cell size, up-regulation of CD25 and CD154 expression and the secretion of IL-2, IFN-gamma and tumor necrosis factor (TNF)-alpha.

DISCUSSION

A low-volume, high-yield bioreactor-based process has been developed, qualified and implemented for the reproducible, GMP manufacture of high purity, biologically active Xcellerated T Cells for the treatment of CLL patients in clinical trials.

CD8+ cell depletion of donor lymphocyte infusions using cd8 monoclonal antibody-coated high-density microparticles (CD8-HDM) after allogeneic hematopoietic stem cell transplantation: a pilot study

A CD8 murine monoclonal antibody-coated high-density microparticle (HDM) has been developed, which allows for the rapid depletion of CD8+ T cells from apheresis products by gravity sedimentation. We conducted a study to determine the efficacy and safety of CD8 depletion of donor lymphocyte infusions (DLI) to treat relapse after stem cell transplantation using the Eligix CD8-HDM Cell Separation System. Patients were targeted to receive 3 x 10(7) CD4+ T cells/kg. Nine patients were enrolled, three with CML, three myeloma, two CLL, and one NHL. A median of 1 x 10(10) mononuclear cells were obtained by apheresis and processed. The median depletion of CD8+ cells was 99.3% (97.8->99.5%). CD8 depletion was highly specific, with a median recovery of CD4+ cells of 75%. A median of 2.9 x 10(7) CD4+ cells/kg was infused. No infusional toxicity was noted. All CML patients achieved a complete molecular remission. A CLL patient demonstrated a complete response. One patient developed GVHD (grade II acute GVHD and subsequently chronic GVHD). The CD8-HDM Cell Separation System appears to be highly selective and effective in depleting CD8+ T cells from DLI apheresis products, and CD8-depleted DLI is capable of mediating a graft-versus-leukemia effect while minimizing GVHD.

Resistant pure red cell aplasia after allogeneic stem cell transplantation with major ABO mismatch treated by escalating dose donor leukocyte infusion

We report a case of pure red cell aplasia (PRCA) following allogeneic stem cell transplantation (SCT) with major ABO mismatch which proved resistant to all standard treatment options such as change in immunosuppressive treatment, high-dose erythropoietin (EPO) or plasma exchange. We therefore proceeded to administer five cycles of Rituximab therapy, without success. Finally, escalating doses of donor-derived leukocyte infusion (DLI) resolved the PRCA of our patient 415 d after bone-marrow transplantation (BMT) and 140 d after the first infusion of donor leukocytes. A review of the literature shows the efficacy of various treatments; the role of DLI and other treatment options are discussed. Furthermore, the underlying pathophysiological mechanisms especially with regard to the role of NK cells in alloreactivity after allogeneic SCT are explained.

Immunological effects of donor lymphocyte infusion in patients with chronic myelogenous leukemia relapsing after bone marrow transplantation

Allogeneic bone marrow transplantation (alloBMT) is the only curative therapy for chronic myelogenous leukemia (CML). This success is explained by the delivery of high doses of antineoplastic agents followed by the rescue of marrow function and the induction of graft-versus-leukemia reaction mediated by allogeneic lymphocytes against host tumor cells. This reaction can also be induced by donor lymphocyte infusion (DLI) producing remission in most patients with CML who relapse after alloBMT. The immunological mechanisms involved in DLI therapy are poorly understood. We studied five CML patients in the chronic phase, who received DLI after relapsing from an HLA-identical BMT. Using flow cytometry we evaluated cellular activation and apoptosis, NK cytotoxicity, lymphocytes producing cytokines (IL-2, IL-4 and IFN-gamma), and unstimulated (in vivo) lymphocyte proliferation. In three CML patients who achieved hematological and/or cytogenetic remission after DLI we observed an increase of the percent of activation markers on T and NK cells (CD3/DR, CD3/CD25 and CD56/DR), of lymphocytes producing IL-2 and IFN-gamma, of NK activity, and of in vivo lymphocyte proliferation. These changes were not observed consistently in two of the five patients who did not achieve complete remission with DLI. The percent of apoptotic markers (Fas, FasL and Bcl-2) on lymphocytes and CD34-positive cells did not change after DLI throughout the different study periods. Taken together, these preliminary results suggest that the therapeutic effect of DLI in the chronic phase of CML is mediated by classic cytotoxic and proliferative events involving T and NK cells but not by the Fas pathway of apoptosis.

Graft-versus-leukemia reactions in allogeneic chimeras

There is a strong graft-versus-leukemia (GVL) effect of allogeneic stem cell transplantation (SCT) due to elimination of tumor cells by alloimmune effector lymphocytes. When leukemia relapses after allogeneic SCT, donor lymphocyte transfusions (DLTs) can induce sustained remissions in some patients. This review summarizes the current status on clinical use of DLT, the basis of GVL reactions, problems associated with this therapy, and new strategies to improve DLT. Several multicenter surveys demonstrated that the GVL effect of DLT is most effective in chronic myelogenous leukemia (CML), whereas it is less pronounced in acute leukemia and myeloma. Cytokine stimulation to induce differentiation of myeloid progenitor cells or to up-regulate costimulatory molecules on tumor cells may improve the efficacy of DLT. Infections and graft-versus-host disease (GVHD) are major complications of DLT. Control of GVHD may be improved using suicide gene-modified T cells for DLT, allowing T-cell elimination if severe GVHD develops. Hopefully, in the future, GVL effect can be separated from GVHD through adoptive transfer of selected T cells that recognize leukemia-specific antigens or minor histocompatibility antigens, which are expressed predominantly on hematopoietic cells, thereby precluding attack of normal tissues. In patients with leukemia and lymphomas with fast progression, tumor growth may outpace development of effector T cells. Here it may be preferable to select stem cell transplant donors with HLA-mismatches that allow alloreactive natural killer cells, which appear early after transplantation, to retain their cytolytic function. New approaches for adoptive immune therapy of leukemia, which promise a better prognosis for these patients, are being developed.

T-cell homeostasis in humans with thymic hypoplasia due to chromosome 22q11.2 deletion syndrome

Patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome) typically exhibit thymic hypoplasia, conotruncal cardiac defects, and hypoparathyroidism. The immunodeficiency that results from the thymic hypoplasia has been extensively described and consists primarily of T-cell lymphopenia. A curious feature of the T-cell lymphopenia is that the age-related rate of decline of T-cell numbers is slower in patients than controls. This leads to T-cell numbers in adulthood that are minimally decreased compared with controls. This suggests that homeostatic mechanisms might be acting to preserve the peripheral blood T-cell numbers in patients. We characterized changes in CD4/CD45RA and CD4/CD45RO T-cell populations in patients and controls of various ages and determined T-cell recombination excision circles and telomere length within the CD4/CD45RA population. Patients had evidence of accelerated conversion of naive to memory cells and had evidence of more extensive replicative history within the CD4/CD45RA compartment compared with controls. Oligoclonal T-cell receptor (TCR) Vbeta families and missing Vbeta families were seen more often in patients than controls. These data are consistent with homeostatic proliferation of T cells in patients with limited T-cell production due to thymic hypoplasia.

The presence and longevity of peripherally expanded donor-derived TCRalphabeta+ mature T lymphocyte clones after allogeneic bone marrow transplantation for adult myeloid leukemias

There are two major pathways for T-cell regeneration after allogeneic bone marrow transplantation; thymus-dependent T-cell differentiation of T-cell progenitors, and peripheral expansion of mature T cells in the graft. In order to learn to what extent the peripheral expansion of donor-derived mature T lymphocytes contributes to reconstitution of the TCRalphabeta+ T-cell repertoire after allogeneic bone marrow transplantation for adult myeloid leukemias, we pursued the fate of donor-derived T-cell clones using the amino-acid sequences of the complementarity-determining region 3 (CDR3) of the TCR-beta chain as a clonal marker. Clonal expansion of TCRalphabeta+ T lymphocytes with specific TCRBV subfamilies was identified in donor blood. Identical T-cell clones were not found in blood from recipients before transplantation. The donor-derived T-cell clones were identified in the circulating blood from recipients a few months after allogeneic bone marrow transplantation, and they remained in the blood for 18 months after transplant in two recipients, and for 56 months in one. These results suggest that the peripheral expansion of mature T lymphocytes in the graft makes a significant contribution to post-transplant T-cell regeneration during the early period of transplantation in humans, and that mature T cells can survive in recipients for several years. Further investigation will be required to explore which antigens drive the expansion of T-cell clones in donors and recipients, and the mechanisms of maintaining homeostatic balance between the thymus-dependent pathway and the peripheral expansion of mature T cells in post-transplant T-cell regeneration.

Hematopoietic stem cell graft manipulation as a mechanism of immunotherapy

Hematopoietic stem cell transplants (SCT) are used in the treatment of neoplastic diseases, in addition to congenital, autoimmune, and inflammatory disorders. Both autologous and allogeneic SCT are used, depending on donor availability and the type of disease being treated, resulting in different morbidity and outcomes. In both types of SCT, immune regulation via graft manipulation is being studied, although with highly different targeted outcomes. In general, autologous SCT have lower treatment-related morbidity and mortality, but a higher incidence of tumor relapse, and graft manipulation targets immune augmentation and/or the reduction of immune tolerance. In contrast, allogeneic SCT have a higher incidence of treatment-related morbidity and mortality and a significantly longer time of disease progression, and the targeted outcomes or graft manipulation focus on a reduction in graft versus host disease (GVHD). One source of the increased relapse rate and shorter overall survival (OS) following high dose chemotherapy (HDT) and autologous SCT is the immune tolerance that limits host response, both innate and antigen (Ag) specific, against the tumor. The immune tolerance that is observed is due in part to the tumor burden and prior cytotoxic therapy. Therefore, graft manipulation, as an adjuvant therapeutic approach in autologous SCT, is primarily focused on non-specific or specific immune augmentation using cytokines and vaccines. Recently, manipulation of the infused product as a form of cellular therapy has begun to also focus on approaches to reduce immune tolerance found in transplant patients, both prior to and following HDT and SCT. To this end, graft manipulation to reduce the presence of Fas Ligand (FasL)-expressing cells or interleukin (IL)10 and tumor growth factor (TGF)beta production has been proposed. In contrast to autologous transplantation, graft manipulation during allogeneic transplantation is used extensively. This includes limiting the infusion of T cells within the product or as a donor leukocyte infusion (DLI), resulting in a reduction in GVHD and the induction of long-term survivors. Indeed, allogeneic SCT provide the only curative therapy for patients with chronic myelogenous leukemia (CML), refractory acute leukemia, and myelodysplasia. The curative potential of allogeneic SCT is reduced, however, by the development of GVHD, a potentially lethal T-cell-mediated immune response targeting host tissues [Int. Arch. Allergy Immunol. 102 (1993) 309, J. Exp. Med. 183 (1996) 589]. The morbidity and mortality associated with GVHD limit this technology, resulting focus on those patients who have no alternative therapeutic options or who have advanced disease. Thus, allogeneic SCT provide one of the few statistically supported demonstrations of therapeutic efficacy by T cells (comparison of allogeneic to autologous transplantation). In contrast to autologous transplantation, control of GVHD following allogeneic SCT focuses on immune suppression and the induction of tolerance. Here too, graft manipulation is appropriate, and there are numerous studies of T-cell depletion to reduce GVHD, with or without the isolation and infusion of T cells as DLI. Additional strategies are examining the isolation and infusion of T cells with graft versus leukemia (GVL) activity to reduce GVHD and/or the infusion of genetically manipulated and/or selected cellular populations (monocytes or dendritic cells (DC)) to induce tolerance. Therefore, depending upon the type of transplant, the goals associated with graft manipulation can be radically different. In this review, we emphasize using graft manipulation to regulate immune tolerance and anergy in association with SCT. Although this paper focuses on hematopoietic SCT, it should be noted that these strategies are relevant to conditions other than neoplastic and congenital diseases, including solid organ transplants, and autoimmune and inflammatory diseases.

CD4(+) bias in T cells cloned from a CML patient with active graft versus leukemia effect

BACKGROUND

The ability to generate a GvL response by infusion of donor leukocytes (DL) in patients following relapse after BMT is now well documented and has been demonstrated to be particularly effective in patients with CML.

METHODS

We generated T-cell lines from a patient who was undergoing an active GvL response following withdrawal of immunosuppression for cytogenetic relapse of CML. Cryopreserved pre-transplant leukemic cells were used as stimulators, to generate T-cell lines and oligoclonal lines from the lymphocytes. In total 38 sub-lines were generated from different bulk cultures. The lines were tested for their proliferative and cytotoxic capability to patient pre-transplant leukemic cells, PHA-transformed lymphoblasts, allogeneic CML cells, and autologous and allogeneic B-LCL.

RESULTS

Four of the cloned lines tested recognized the patient's pre-transplant leukemic cells. Specifically, two were both cytotoxic and proliferative in response to patient leukemic cells and two were cytotoxic only. Six clonal lines recognized PHA blasts only and were proliferative; one was specific for PHA blasts and CML cells. The sub-lines were phenotyped for cell-surface markers and all were CD4(+) CD8(-) CD 16/56(-). The proliferative response of the leukemia-specific clonal lines could be blocked with anti-MHC Class II MAbs.

DISCUSSION

These data suggest that CD4(+) cells play a crucial role in mediating the GvL effect in CML patients. Our observations can be used to delineate strategies for enhancing and investigating the GvL effect in CML.

Definitive separation of graft-versus-leukemia- and graft-versus-host-specific CD4+ T cells by virtue of their receptor beta loci sequences

Although graft-versus-host (GVH) disease (GVHD) is usually associated with graft versus leukemia (GVL), GVL can occur in the absence of clinical GVHD. There is evidence to suggest that GVL and GVH are mediated by different clones of T cells. The objective of this study was to identify the two types of T cells based on their receptor sequences. To this end we used irradiated nonleukemic cells from recipients as stimulator cells in a primary mixed leukocyte reaction (MLR). The activated CD4(+) donor T cells that expressed CD25 were purified by cell sorting. To prepare GVL-specific T cells, alloreactive T cells in the primary MLR were first depleted with an anti-CD25 immunotoxin. The remaining T cells had negligible alloreactivity in a secondary MLR. The allodepleted cells were then stimulated by using purified leukemia cells from the same individual as stimulator cells, and the CD25(+)-activated cells were purified by cell sorting. The GVL- and GVH-specific T cells were analyzed for their T cell receptor (TCR) clonality by using anchored RT-PCR of all the TCRbeta locus complementarity-determining region 3 (CDR3) sequences. By comparing TCRbeta CDR3 sequences from transformed bacterial colonies, we were able to demonstrate that T cells mediating GVH were different from those mediating GVL in each of the eight HLA-mismatched and one HLA-matched donor/recipient pairs. By using the appropriate TCRbeta CDR3-specific primers and probes, the GVH- and GVL-specific clones were monitored in a recipient undergoing an allogeneic stem cell transplant from her HLA-matched related donor.

Allogeneic stem cell transplantation for multiple myeloma

The sensitivity of myeloma cells to high dose chemotherapy has led to the use of allogeneic hematopoietic stem cell transplantation (HSCT) as a therapeutic modality in this disease. In addition to providing more effective chemotherapy, the transplantation of allogeneic stem cells also initiates the development of an allogeneic immune response directed against residual myeloma cells. Direct evidence for a graft vs. myeloma (GVM) effect is provided by the ability of donor lymphocyte infusion (DLI) to induce significant responses in 30-50% of patients with myeloma who have relapsed after allogeneic HSCT. Nevertheless, allogeneic stem cell transplantation is also associated with a high incidence of transplant related toxicities, including regimen-related toxicities, graft vs. host disease (GVHD) and opportunistic infections. DLI has been shown to enhance immune reconstitution after allogeneic HSCT in addition to inducing a GVM response. Current efforts are directed at reducing the toxicities associated with allogeneic HSCT, identification of the target antigens of GVM and the development of new strategies to selectively enhance the immune response to myeloma cells.

In vitro and in vivo characterization of graft-versus-tumor responses in melanoma patients after allogeneic peripheral blood stem cell transplantation

It has been shown that after allogeneic peripheral blood stem cell transplantation (PBSCT), donor T cells can induce potent graft-versus-tumor (GVT) effects in hematologic malignancies and possibly solid tumors such as renal cell carcinoma. Two patients (27 and 30 years old) with metastatic melanoma received allogeneic PBSCT from an HLA-identical sibling donor after reduced conditioning with fludarabine, carmustine and melphalan. One patient showed a delayed mixed response with complete regression of lymph node metastases but persistent liver metastasis at day +60 and +120, consistent with a GVT response. In order to generate donor-derived tumor-reactive cytotoxic T lymphocytes (CTLs), peripheral blood mononuclear cells were stimulated with donor dendritic cells (DCs) loaded with host tumor lysate. Using these culture conditions, a marked increase in CD8(+) CTLs was observed in both donors exhibiting a strong MHC class I-restricted cytotoxic activity against the host tumor without cross-reactivity against nonmalignant host cells. CDR3 spectratyping was used to analyze the complexity of T-cell subpopulations in both CTL lines. Results demonstrate that oligoclonal T cells are expanded in vitro, exhibiting a marked overexpression of TCRVbeta3 (donor 1) and TCRVbeta4/Vbeta11 (donor 2) subfamilies. Functional (ELISPOT assay) and phenotypic (CDR3 spectratyping, sequencing Vbeta transcripts) analysis of patients' T cells at different time points after transplantation demonstrated an expansion of alloreactive T cells with a limited TCR Vbeta pattern. The Vbeta3 cDNA clone, being predominant in the CTL line from donor 1, could not be identified in patient 1 peripheral blood lymphocytes after transplant. Altogether, our results provide the first evidence that GVT effects against melanoma can induce tumor regression and that oligoclonal donor-derived CTLs specific against host tumor cells can be generated in vitro that may be used for adoptive T-cell transfer after allogeneic transplantation.

Immunologic effects of prophylactic donor lymphocyte infusion after allogeneic marrow transplantation for multiple myeloma

Reconstitution of T-cell immunity after bone marrow transplantation (BMT) is often delayed, resulting in a prolonged period of immunodeficiency. Donor lymphocyte infusion (DLI) has been used to enhance graft-versus-leukemia activity after BMT, but the effects of DLI on immune reconstitution have not been established. We studied 9 patients with multiple myeloma who received myeloablative therapy and T-cell-depleted allogeneic BMT followed 6 months later by infusion of lymphocytes from the same donor. DLI consisted of 3 x 10(7) CD4(+) donor T cells per kilogram obtained after in vitro depletion of CD8(+) cells. Cell surface phenotype of peripheral lymphocytes, T-cell receptor (TCR) V beta repertoire, TCR rearrangement excision circles (TRECs), and hematopoietic chimerism were studied in the first 6 months after BMT and for 1 year after DLI. These studies were also performed in 7 patients who received similar myeloablative therapy and BMT but without DLI. Phenotypic reconstitution of T and natural killer cells was similar in both groups, but patients who received CD4(+) DLI developed increased numbers of CD20(+) B cells. TCR V beta repertoire complexity was decreased at 3 and 6 months after BMT but improved more rapidly in patients who received DLI (P =.01). CD4(+) DLI was also associated with increased numbers of TRECs in CD3(+) T cells (P <.001) and with conversion to complete donor hematopoiesis (P =.05). These results provide evidence that prophylactic infusion of CD4(+) donor lymphocytes 6 months after BMT enhances reconstitution of donor T cells and conversion to donor hematopoiesis as well as promoting antitumor immunity.

Changes in T-cell receptor VB repertoire in aplastic anemia: effects of different immunosuppressive regimens

We studied the degree and the pattern of skewing of the variable region of beta-chain (VB) T-cell receptor (TCR) repertoire in aplastic anemia (AA) at initial presentation and after immunosuppression using a high-resolution analysis of the TCR VB complementarity-determining region 3 (CDR3). Age-matched healthy individuals and multitransfused patients with non-immune-mediated hematologic diseases were used as controls. In newly diagnosed AA, the average frequency of CDR3 size distribution deviation indicative of oligoclonal T-cell proliferation was increased (44% +/- 33% vs 9% +/- 9%; P =.0001); AA patients with human leukocyte antigen (HLA)-DR2 and those with expanded paroxysmal nocturnal hemoglobinuria clones showed more skewed VB repertoires. Nonrandom oligoclonal patterns were found for VB6, VB14-16, VB21, VB23, and VB24 subfamilies in more than 50%, and for VB15, VB21, and VB24 in more than 70% of AA patients with HLA-DR2. Patients received immunosuppression with antithymocyte globulin (ATG)/cyclosporine (CsA) or cyclophosphamide (CTX) with CsA in combination, and their VB repertoire was reanalyzed after treatment. Whereas no significant change in the degree of VB skewing in patients who had received ATG was seen, patients treated with CTX showed a much higher extent of oligoclonality within all VB families, consistent with a profound and long-lasting contraction of the T-cell repertoire. VB analysis did not correlate with the lymphocyte count prior to lymphocytotoxic therapy; however, after therapy the degree of VB skewing was highly reflective of the decrease in lymphocyte numbers, suggesting iatrogenic gaps in the VB repertoire rather than the emergence of clonal dominance. Our data indicate that multiple specific clones mediate the immune process in AA.

A broad T-cell repertoire diversity and an efficient thymic function indicate a favorable long-term immune reconstitution after cord blood stem cell transplantation

Cord blood (CB) is used increasingly as a source of hematopoietic stem cells because of a lower risk of acute and chronic graft-versus-host disease (GVHD). However, there is some concern regarding the ability to adequately reconstitute host immune response due to the immaturity and naivety of CB T cells. This study was designed to evaluate T-cell reconstitution using combined approaches of phenotyping, analysis of alphabeta T-cell receptor (TCR) diversity, and assessment of ex vivo thymic function by measuring TCR rearrangement excision circles (TRECs). Ten patients who underwent CB transplantation for high-risk hematologic disorders were compared to a reference group of 19 age- and GVHD-matched patients who underwent transplantation with non-T cell-depleted bone marrow from an HLA-identical sibling donor. TREC values correlated with the relative number of naive T cells and with TCR repertoire polyclonality. During the first year after transplantation, TCR repertoires were highly abnormal and TREC values low in both groups. Notably, 2 years after transplantation onward TREC values as well as TCR diversity were higher in CB recipients than in recipients of bone marrow transplants. These data indicate an efficient thymic regeneration pathway from CB lymphoid progenitors despite the low number of cells infused compared to bone marrow, arguing for a complete clinical immune recovery after CB transplantation.

Ex vivo expansion of polyclonal and antigen-specific cytotoxic T lymphocytes by artificial APCs expressing ligands for the T-cell receptor, CD28 and 4-1BB

The ex vivo priming and expansion of human cytotoxic T lymphocytes (CTLs) has potential for use in immunotherapy applications for cancer and infectious diseases. To overcome the difficulty in obtaining sufficient numbers of CTLs, we have developed artificial antigen-presenting cells (aAPCs) expressing ligands for the T-cell receptor (TCR) and the CD28 and 4-1BB co-stimulatory surface molecules. These aAPCs reproducibly activate and rapidly expand polyclonal or antigen-specific CD8(+) T cells. The starting repertoire of CD8+ T cells was preserved during culture. Furthermore, apoptosis of cultured CD8(+) T cells was diminished by this approach. This approach may have important therapeutic implications for adoptive immunotherapy.

Immune haemolytic anaemia following T cell-depleted allogeneic bone marrow transplantation for chronic myeloid leukaemia: association with leukaemic relapse and treatment with donor lymphocyte infusions

Immune haemolytic anaemia (IHA) is a recognised complication after allogeneic stem cell transplantation (SCT) and occurs more frequently if marrow cells have been subjected to T cell depletion (TCD). Among 58 consecutive patients who underwent TCD-allogeneic SCT from volunteer unrelated donors for the treatment of CML at the Hammersmith Hospital during a 3-year period (1 March 1996 to 28 February 1999) we identified nine cases of IHA. All patients had a strongly positive direct and indirect antiglobulin test and in eight patients the serological findings were typical of warm-type haemolysis often with antibody specificities within the Rh system. All nine cases had clinically significant haemolysis and were treated initially with prednisolone and immunoglobulin. The onset of IHA coincided with the occurrence of leukaemic relapse in six cases, and the presence of host haemopoiesis confirmed by lineage-specific chimerism in all four cases studied. Five patients received donor lymphocyte infusions (DLI); in three molecular remission and the restoration of full donor chimerism coincided with resolution of haemolysis. We conclude that in the context of leukaemic relapse, DLI is an effective therapy for IHA following allografts involving TCD.

Quantitation of T-cell neogenesis in vivo after allogeneic bone marrow transplantation in adults

Following myeloablative therapy, it is unknown to what extent age-dependent thymic involution limits the generation of new T cells with a diverse repertoire. Normal T-cell receptor gene rearrangement in T-cell progenitors results in the generation of T-cell receptor rearrangement excision circles (TRECs). In this study, a quantitative assay for TRECs was used to measure T-cell neogenesis in adult patients with leukemia who received myeloablative therapy followed by transplantation of allogeneic hematopoietic stem cells. Although phenotypically mature T cells had recovered by 1 to 2 months after bone marrow transplantation (BMT), TREC levels remained low for 3 months after BMT. T-cell neogenesis became evident by 6 months, and normal levels of adult thymic function were restored at 6 to 12 months after BMT. Subsequent leukemia relapse in some patients was associated with reduced TREC levels, but infusion of mature donor CD4(+) T cells resulted in rapid restoration of thymic function. These studies demonstrate that T-cell neogenesis contributes to immune reconstitution in adult patients and suggest that thymic function can be manipulated in vivo. (Blood. 2001;98:1116-1121)

In vitro T-cell receptor V beta repertoire analysis may identify which T-cell V beta families mediate graft-versus-leukaemia and graft-versus-host responses after human leucocyte antigen-matched sibling stem cell transplantation

We studied oligoclonal T-cell expansions of 24 T-cell receptor (TCR) V beta families in normal donor lymphocytes stimulated with patient's cells and in recipient blood after transplant, using a polymerase chain reaction-based assay (spectratyping). T cells from donor blood were incubated with separated myeloid leukaemia cells or T cells from the HLA-identical sibling recipient. In five of the six patients tested, the T-cell V beta skewing pattern observed in vitro was seen in vivo after transplant. After transplant, the myeloid-specific V beta skewing coincided with the disappearance of residual disease in three patients and in one patient skewing was lost at the time of leukaemic relapse. In functional tests, T cells generated against leukaemic cells in vitro produced interferon gamma in response to the leukaemia. Removal of the leukaemia-expanded skewed V beta families significantly decreased cytotoxic killing of the leukaemia. However, while there was a general concordance in the V beta family exhibiting clonal expansion in vitro and in vivo, the exact clonotype expanded in vitro and in vivo differed. These findings suggest that alloresponses involve multiple T-cell clones within a restricted TCR V beta repertoire that undergo different selection pressures in vitro and in vivo.

CML66, a broadly immunogenic tumor antigen, elicits a humoral immune response associated with remission of chronic myelogenous leukemia

This report describes a tumor-associated antigen, termed CML66, initially cloned from a chronic myelogenous leukemia (CML) cDNA expression library. CML66 encodes a 583-aa protein with a molecular mass of 66 kDa and no significant homology to other known genes. CML66 gene is localized to human chromosome 8q23, but the function of this gene is unknown. CML66 is expressed in leukemias and a variety of solid tumor cell lines. When examined by Northern blot, expression in normal tissues was restricted to testis and heart, and no expression was found in hematopoietic tissues. When examined by quantitative reverse transcription-PCR, expression in CML cells was 1.5-fold higher than in normal peripheral blood mononuclear cells. The presence of CML66-specific antibody in patient serum was confirmed by Western blot and the development of high titer IgG antibody specific for CML66 correlated with immune induced remission of CML in a patient who received infusion of normal donor lymphocytes for treatment of relapse. CML66 antibody also was found in sera from 18-38% of patients with lung cancer, melanoma, and prostate cancer. These findings suggest that CML66 may be immunogenic in a wide variety of malignancies and may be a target for antigen-specific immunotherapy.

A CD4+ T CELL CLONE SELECTED FROM A CML PATIENT AFTER DONOR LYMPHOCYTE INFUSION RECOGNIZES BCR-ABL BREAKPOINT PEPTIDES BUT NOT TUMOR CELLS1

BACKGROUND

In patients with chronic myelocytic leukemia (CML), the breakpoint cluster region and fusion between the BCR and the c-ABL genes (BCR-ABL) oncogen product is a potential tumor-specific antigen. Previous studies have shown that T cells specific for the junctional region peptides of the BCR-ABL oncoprotein can be detected in healthy individuals as well as in patients with CML in chronic phase. We assessed whether BCR-ABL- specific T cells could be found in a patient achieving a complete cytogenetic remission after CD4+ donor lymphocyte infusion.

METHODS

Using dendritic cells pulsed with BCR-ABL breakpoint peptides as antigen-presenting cells, we stimulated patient peripheral blood lymphocytes to isolate peptide-specific T cell clones present at the time of the cytogenetic response. T cell clones were isolated and the cellular specificity of these cells was examined.

RESULTS

A CD3+ CD4+ T cell clone (1F7) that recognizes overlapping p210 junctional peptides presented by HLA-DR molecules was identified and expanded in vitro. Clone 1F7 failed to recognize autologous tumor cells as well as dendritic cells derived from patient CML cells. Clone 1F7 did not inhibit the growth and differentiation of CML precursor cells in a standard colony formation assay. Finally, using a clone-specific probe, 1F7 cells could not be detected in patient peripheral blood at the time of the donor lymphocyte infusion response.

CONCLUSIONS

These results suggest that clone 1F7 was selected in vitro using highly potent peptide pulsed dendritic cells but was not representative of the anti-leukemia immune response in vivo. Based on these findings, CD4+ T cells with BCR-ABL specificity do not appear to be mediators of the anti-leukemia response in vivo after donor lymphocyte infusion.

Identification of T-cell clones showing expansion associated with graft-vs-leukemia effect on chronic myelogenous leukemia in vivo and in vitro

Although the graft-vs-leukemia (GVL) effect induced by donor leukocyte infusion (DLI) is thought to be mediated by T cells, their features, as well as target molecules, remain unknown. To characterize T cells that mediate the GVL effect on chronic myelogenous leukemia (CML), we studied T-cell repertoire in peripheral blood (PB) of two patients treated with DLI for relapsed CML after allogeneic bone marrow transplantation. Peripheral blood mononuclear cells (PBMCs) were obtained at 2-week intervals following DLI and examined for the presence of antigen-driven T-cell proliferation using complementarity-determining region (CDR) 3 size spectratyping of T-cell receptor beta chain subfamilies. Both patients exhibited transient proliferation of a limited number of T cells at a certain point in time (day 132 for patient 1 and day 75 for patient 2) after DLI in association with a decrease in the proportion of Philadelphia chromosome (Ph)-positive cells. In patient 2, who showed expansion of a BV16(+) T cell in PB, expansion of BV16(+) T cells with a similar CDR3 motif containing QDR to that of PB was demonstrated in the bone marrow (BM) sampled on day 33 and in the buccal mucosal tissue, showing chronic graft-vs-host disease (GVHD) on day 138 after DLI. When PBMCs obtained from patient 2 in remission were cultured with cryopreserved CML cells for 2 weeks, proliferation of a BV16(+) T cell with a CDR3 motif of QIR was induced in vitro. These findings indicate that transient proliferation of a limited number of T cells detected in PB 3-5 months after DLI probably reflects the GVL response against CML cells and may serve as a marker for the appearance of the GVL effect induced by DLI.

Induction of MTG8-specific cytotoxic T-cell lines: MTG8 is probably a tumour antigen that is recognized by cytotoxic T cells in AML1-MTG8-fused gene-positive acute myelogenous leukaemia

Several reports have demonstrated the persistent detection of AML1-MTG8 fusion products, representing minimal residual disease (MRD), in patients with t(8;21) acute myelogenous leukaemia (AML) who are in long-term remission. It is probable that immune-mediated mechanisms that are able to suppress the expansion of MRD may result in the continuance of remission. It was previously shown that some t(8;21) AML patients had high anti-MTG8 antibody titres. MTG8 expression in normal adult tissues is limited to the brain or heart in which human leucocyte antigen (HLA) class I cell-surface antigens are either not or are only faintly detectable. We hypothesized that the overexpression of the MTG8 gene in t(8;21) AML cells could act as a possible tumour antigen, which might be able to induce the immune-mediated suppression of the expansion of MRD. We were able to induce HLA-A0201-restricted cytotoxic T-lymphocyte (CTL) lines against an MTG8 peptide (MTG8b amino acids 182-191) using monocyte-derived dendritic cells from a healthy donor. T-cell receptor (TCR)Valpha17, TCRVbeta14 and 15, and TCRJbeta2.1 and 2.3 are predominantly used in these CTL lines. Our data, which suggest that the MTG8 protein could be one of the tumour antigens recognized by CTLs, may be helpful in further investigations of TCR analysis in t(8;21) AML patients with HLA-A0201 who are in long-term remission.

Donor lymphocyte infusions for relapsed multiple myeloma after allogeneic stem-cell transplantation: predictive factors for response and long-term outcome

PURPOSE

To determine the efficacy, toxicity, and long-term outcome and prognostic factors of donor lymphocyte infusions (DLI) in patients with relapsed multiple myeloma (MM) after allogeneic stem-cell transplantation (AlloSCT).

MATERIALS AND METHODS

Twenty-seven patients received 52 DLI courses at a median of 30 months after the previous AlloSCT. Reinduction therapy was administered to 13 patients before DLI.

RESULTS

Reinduction therapy was successful in eight of 13 patients. Fourteen patients (52%) responded to DLI, including six patients (22%) who achieved a complete remission (CR). Five patients responded after T-cell dose escalation in subsequent DLIs. Four patients experienced relapse or disease progression (three from partial response and one from CR). Five patients remain in remission more than 30 months after DLI. Major toxicity was acute and chronic graft-versus-host disease (GVHD), which was present in 55% and 26% of patients, respectively. Two patients died from bone marrow aplasia. Median overall survival of all patients was 18 months. Overall survival was 11 months for DLI-resistant patients and has not been reached for the responding patients. In two patients, sustained molecular remission was observed. The factors that were correlated with response to DLI were a T-cell dose of more than 1.10(8) cells/kg, response to reinduction therapy, and chemotherapy-sensitive disease before AlloSCT.

CONCLUSION

These data confirm the potential and durable graft-versus-myeloma effect of DLI in patients with relapsed MM after AlloSCT. Future studies should be aimed at increasing response rates, especially in patients with chemoresistant disease, and reducing toxicity by limiting GVHD. Adjuvant DLI seems an attractive and promising approach for patients who do not achieve a molecular remission after AlloSCT.