Advances in clinical NK cell studies: Donor selection, manufacturing and quality control

Natural killer (NK) cells are increasingly used in clinical studies in order to treat patients with various malignancies. The following review summarizes platform lectures and 2013–2015 consortium meetings on manufacturing and clinical use of NK cells in Europe and United States. A broad overview of recent pre-clinical and clinical results in NK cell therapies is provided based on unstimulated, cytokine-activated, as well as genetically engineered NK cells using chimeric antigen receptors (CAR). Differences in donor selection, manufacturing and quality control of NK cells for cancer immunotherapies are described and basic recommendations are outlined for harmonization in future NK cell studies.

Combination of immunoglobulins and natural killer cells in the context of CMV and EBV infection

Cytomegalovirus (CMV)-specific hyperimmunoglobulin (CMV-HIG) is used to treat and prevent CMV infection in immunocompromised patients, and anti-CD20 monoclonal antibody is successfully used in the treatment for post-transplant lymphoproliferative disease caused by Epstein-Barr virus (EBV). Two immunological approaches have been suggested to further improve the control of viral reproduction in patients with active disease: first, the use of monoclonal antibodies with specificity against viral epitopes and second, coadministration of cells with the capacity to promote antibody-dependent cell-mediated cytotoxicity. Here, we have evaluated the effectiveness of these strategies in vitro (alone and in combination) with neutralization and cytotoxicity assays. Our results indicate that monoclonal antibodies (in particular SM5-1) can be as effective as CMV-HIG in neutralizing-cell-free CMV. Moreover, our data indicate that antibody-mediated elimination (either by moAb or by HIG) of EBV-infected cells can be significantly enhanced by NK cells. Using human NK cells that have been purified, cultured and expanded under GMP conditions, we were able to demonstrate that the combination of NK cells and antibodies could represent a feasible and highly effective clinical approach to achieve control of EBV infections. Especially in leukopenic patients with low numbers of ADCC-promoting cells, the combination of adoptively transferred NK cells and antiviral antibodies offers a promising strategy that should be tested in clinical trials.

Azacitidine and donor lymphocyte infusions as first salvage therapy for relapse of AML or MDS after allogeneic stem cell transplantation

The combination of azacitidine and donor lymphocyte infusions (DLI) as first salvage therapy for relapse after allogeneic transplantation (allo-HSCT) was studied in 30 patients with acute myeloid leukemia (AML; n=28) or myelodysplastic syndromes (MDS; n=2) within a prospective single-arm multicenter phase-II trial. Treatment schedule contained up to eight cycles azacitidine (100 mg/m(2)/day, days 1-5, every 28 days) followed by DLI (from 1-5 × 10(6) to 1-5 × 10(8) CD3(+)cells/kg) after every second azacitidine cycle. A median of three courses azacitidine (range 1-8) were administered, and 22 patients (73%) received DLI. Overall response rate was 30%, including seven complete remissions (CRs, 23%) and two partial remissions (7%). Five patients remain in CR for a median of 777 days (range 461-888). Patients with MDS or AML with myelodysplasia-related changes were more likely to respond (P=0.011), and a lower blast count (P=0.039) as well as high-risk cytogenetics (P=0.035) correlated with the likelihood to achieve CR. Incidence of acute and chronic graft-versus-host disease was 37% and 17%, respectively. Neutropenia and thrombocytopenia grade III/IV occurred during 65% and 63% of treatment cycles, while infections were the most common grade III/IV non-hematological toxicity. Azacitidine and DLI as salvage therapy is safe, induces long-term remissions and may become an alternative for patients with AML or MDS relapsing after allo-HSCT.

Detection of a novel HLA-A allele, designated A*02:334

We report a novel allele HLA-A*02:334 with the transition G→A at nucleotide position 282.

Allogeneic hematopoietic SCT in patients with AML following treosulfan/fludarabine conditioning

An alternative reduced-toxicity conditioning regimen for allogeneic transplantation, based on treosulfan and fludarabine, has recently been identified. The safety and efficacy of this new conditioning regimen has been investigated prospectively in patients with AML. A total number of 75 patients with AML in CR were treated with 3 × 14 g/m(2) treosulfan and 5 × 30 mg/m(2) fludarabine, followed by matched sibling or unrelated SCT. Patients were evaluated for engraftment, adverse events, GVHD, and for non-relapse mortality, relapse incidence, overall and disease-free survival (DFS). All patients showed primary engraftment of neutrophils after a median of 20 days. Non-hematological adverse events grade III-IV in severity included mainly infections (59%) and gastrointestinal symptoms (7%). Acute GVHD grade II-IV occurred in 21% and extensive chronic GVHD occurred in 16% of the patients. After a median follow-up of 715 days, the 2-year overall and DFS estimates were 61% and 55%, respectively. The 2-year incidences of relapse and non-relapse mortality reached 34% and 11%, respectively. In summary, our data confirm promising safety and efficacy of the treosulfan-based conditioning therapy in AML patients, ClinicalTrials.gov Identifier: NCT01063660.

A new HLA-B*52 allele, B*52:23, detected in a patient before bone marrow transplantation

The new allele HLA-B*52:23 differs from B*52:01:01 at position 208 in exon 2.

Immune reconstitution and cytomegalovirus infection after allogeneic stem cell transplantation: the important impact of in vivo T cell depletion

We analyzed cytomegalovirus (CMV) infection risk factors and immune reconstitution kinetics in 89 patients after allogeneic stem cell transplantation (allo-SCT). The use of alemtuzumab for in vivo T cell depletion (TCD) had, besides the donor/recipient CMV serostatus, the strongest influence on the CMV infection risk in univariate and multivariate analyses. In comparison to without use of in vivo TCD, the CMV infection risk [hazard ratio (HR)] was 4.82-fold after TCD with alemtuzumab, but only 1.40-fold after TCD with antithymocyte globulin (ATG). Alemtuzumab strongly depressed CD4(+) and CD8(+) T cell reconstitution, whereas ATG only delayed CD4(+) T cell reconstitution. Considering the reconstitution kinetics of CD4(+) and CD8(+) T cells, CMV-specific CD8(+) T cells, NK cells and the IgG concentration, only a low day +60 NK cell count (< or =161 versus >161/microl) was significantly associated with CMV infection development (HR 2.92, p = 0.034). CMV-specific CD8(+) T cells were detected in 57% of patients with a CMV-seropositive donor, but in none of the patients with a CMV-seronegative donor on day +30 (p = 0.01). Our data indicate that the type of in vivo TCD (alemtuzumab or ATG) differentially influences both the CMV infection risk and CD4(+)/CD8(+) T cell reconstitution kinetics in patients after allo-SCT.

Adoptive T-cell therapy of a lung transplanted patient with severe CMV disease and resistance to antiviral therapy

Infections with cytomegalovirus (CMV) can induce severe complications after transplantation, particularly in patients resistant to virostatic therapy. Adoptive transfer of CMV-specific T-cell lines has demonstrated promising results in patients after hematopoietic stem cell transplantation. However, the generation of specific T-cell lines ex vivo and their function in vivo is complicated in solid organ transplant (SOT) recipients. Here, we present the successful adoptive transfer of autologous CMV-specific T cells to a lung transplant recipient with ganciclovir-resistant CMV-pneumonia requiring mechanical ventilation. Infused T cells rapidly expanded in vivo and efficiently inhibited viral replication as confirmed by extensive longitudinal immunological monitoring. After full recovery, the patient was released from the clinic. After 4 weeks, the infection reappeared and persisted at a low level even after a second T-cell infusion. Our experimental data indicate that this could be the consequence of the late differentiated phenotype of the infused T cells and therefore their insufficient longevity in vivo. In summary, our report signifies the high therapeutic potential of adoptive immunotherapy in the treatment of SOT recipients when all other measures show no effect. Further studies have to elucidate the most potent strategies to generate antigen-specific T cells with high functional capacity and robust long-term persistence.

In vivo diagnosis of acute intestinal graft-versus-host disease by confocal endomicroscopy

BACKGROUND AND STUDY AIMS

Conventional histology with hematoxylin and eosin (H&E) staining is the accepted standard for diagnosing acute intestinal graft-versus-host disease (GvHD). Confocal endomicroscopy (CEM) is a noninvasive method that allows in vivo histology to be performed during endoscopy. The aim of this study was to evaluate CEM for the diagnosis of acute intestinal GvHD.

PATIENTS AND METHODS

This observational pilot study conducted between September 2006 and August 2008 included patients with acute diarrhea after stem cell transplantation, infectious diarrhea, or active ulcerative colitis. CEM (EC-3870CIFK, Pentax, Tokyo, Japan) was performed after intravenous injection of fluorescein 10% and topical application of acriflavine 0.05%.

RESULTS

A total of 35 patients with acute diarrhea after stem cell transplantation were examined. In 16 patients, CEM and histology showed no evidence of GvHD. In 14/19 patients with histologically confirmed GvHD, the diagnosis could already be established by CEM during ongoing endoscopy. In GvHD grade IV, near complete destruction of the colonic crypts ("flat mucosa") was visible. Control patients with infectious colitis (N = 15) or ulcerative colitis (N = 15) displayed inflammatory changes but no evidence of GvHD. Altogether, sensitivity of CEM was 74% and specificity was 100 %.

CONCLUSIONS

CEM improves rapid diagnosis of acute intestinal GvHD with high accuracy while performing endoscopy. Platelet transfusions and unnecessary biopsy acquisition can be avoided once acute intestinal GvHD has been diagnosed in vivo.

Intensified strategies to control vancomycin-resistant enterococci in immunocompromised patients

Increasing colonization and infection with vancomycin-resistant enterococci (VRE) in immunocompromised patients are associated with increased mortality. Despite contact precautions for VRE control, rapid limitation of its spread is often impossible. We report on a VRE outbreak in a hematologic/oncologic unit including 33 patients. Although 28 of the patients had only VRE colonization, VRE-related infection was probable in 4 patients, and VRE infection of the bloodstream occurred in 1 case. Two patients were identified by VRE screening on admission, 20 were identified by weekly routine VRE screening, and 6 were identified from specimens taken to clarify infections (eg, urine, bronchoalveolar lavage). Five individuals acquired VRE colonization as inpatients (contact patients). Multiple-locus variable-number tandem repeat analysis (MLVA) proved that the outbreak was caused by VanA gene-positive Enterococcus faecium belonging to MLVA genogroup C1(MLVA types 1, 7, 12). The outbreak strains exhibited the potential virulence factor esp(enterococcus surface protein). The outbreak was terminated within 2 months by intensified infection-control measures, including quarantine and the cohorting of patients who tested positive for VRE; however, VRE spread recurred after the measures were discontinued but was again limited by resuming the measures. We conclude that intensive infection-control strategies enable the timely termination of VRE outbreaks, even those involving VRE strains with high epidemic potential on "high-risk wards" (eg, hematologic/oncologic units). Premature discontinuation of infection-control measures may cause recurrence of the VRE spread.

Phase II trial of vaccination with WT1 peptide, GM-CSF, and KLH in patients with acute myeloid leukemia and myelodysplasia: Final immunological, molecular, and clinical results

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Purpose: A phase II trial of vaccination with the HLA-A2-restricted WT1.126–134 peptide was performed in patients (pts) with AML and MDS and overexpression of WT1 to determine toxicity, immunogenicity, and molecular and clinical activity. Methods: Patients received intra/subcut. vaccinations of 0.2 mg WT1.126–134 peptide (day 3), 62.5 mcg GM-CSF (days 1–4) as DC-stimulant and 1 mg keyhole limpet hemocyanin (day 3) as T helper protein. Vaccination was biweekly x 4 followed by 4-weekly in the first 13 patients and continuously biweekly in the subsequent 13. Early disease progression until vaccine # 6 was allowed, if not requiring chemotherapy. WT1-specific T cell responses were measured by tetramer and cytokine flow cytometry. WT1 levels were assessed by qRT-PCR. Clinical response assessment followed IWG-MDS criteria, capturing stable disease and hematologic improvement. Statistical analysis was performed by frequency tables and exploratory comparisons using Fishers test. Results: Of 29 pts enrolled 25 were evaluable, 23 with AML and 2 with RAEB. 15 AML pts had >5% marrow blasts and 8 had high-risk CR with detectable WT1 mRNA. A median of 11 (range 3 - 25) vaccinations was administered, 3 pts are ongoing. No relevant toxicity occurred. There were no obvious differences in outcome parameters between the 2 vaccination schedules. The percentage of patients with WT1 tetramer response increased from 28% prior to vaccination to 80% at week 10 (p=0.003), while the WT1 peptide specific cytokine response increased from 20% to 57% (p=0.012) of patients. WT1 mRNA-levels increased in 22% of patients, were stable in 26%, and decreased in 52% (2 to>50-fold). One CR (514 days) and 13 SD (99 to 339 days) were observed, 5 SD with >50% blast reduction and 3 with hematologic improvement. The CR and 3 SD occurred after initial PD. The median time to treatment failure (TTF) was 143 days. There was a significant association between decrease in WT1 mRNA levels and TTF (p=0.026). Conclusions: This study proves immunological, molecular and clinical efficacy of WT1 peptide vaccination in AML. Further investigations are indicated in WT1 expressing carcinomas and in combination with agents targeting CTLA4 or PD1.

No significant financial relationships to disclose.

Reduced-toxicity conditioning with fludarabine and treosulfan prior to allogeneic stem cell transplantation in multiple myeloma

In recent years, reduced-intensity conditioning (RIC) regimens before allogeneic stem cell transplantation (SCT) are increasingly used in patients not eligible for conventional conditioning. We did a retrospective, multicenter analysis to assess the feasibility of conditioning with fludarabine and treosulfan before allogeneic SCT in multiple myeloma patients. Thirty-four patients with a median age of 51.5 years were included in the analysis. All patients underwent myeloablation after conditioning followed by stable engraftment, and 29 of 31 evaluable patients (94%) showed early complete hematopoietic chimerism. Non-hematological toxicities were limited and encompassed mainly fever in neutropenia and infections. Grade II-IV acute and chronic graft-versus-host disease was observed in 33 and 39%, respectively. With a median follow-up of 708 days (range 60-1729 days), the median progression-free survival was 180 days. The treatment-related mortality was 10% on day 100 and 25% after 1 year. The median overall survival has not yet been reached. Our data indicate that conditioning with fludarabine and treosulfan before allogeneic SCT is feasible in intensively pretreated multiple myeloma patients and leads to stable engraftment and complete hematopoietic chimerism. Randomized trials are warranted to determine if this approach might be incorporated in an algorithm of multiple myeloma treatment.

Patients at high risk for CMV infection and disease show delayed CD8+ T-cell immune recovery after allogeneic stem cell transplantation

Human cytomegalovirus (CMV) is a major cause of death after transplantation. The frequency of pp65-specific T cells was examined in 38 HLA-A2+ stem cell recipients during the first year after transplantation. Patients were divided into four groups based on donor/recipient serostatus: d+/r+ (n=17), d+/r- (n=7), d-/r+ (n=9) and d-/r- (n=5). Peripheral blood mononuclear cells were stimulated with the CMVpp65 peptide NLVPMVATV, and the specific T-cell frequency was assessed by interferon gamma (IFN-gamma) ELISPOT assay. Responding T cells were characterized by flow cytometry revealing a terminal differentiated effector phenotype. Surveillance of CMV infection was carried out by real-time polymerase chain reaction (n=26) or immunofluorescence (n=12). Infection was present in 7/9 d-/r+ high-risk patients, and CMV disease occurred exclusively in this group with delayed or absent virus-specific T-cell recovery. In contrast, 16/24 intermediate-risk patients showed CMV-specific T cells. Our data suggest that CMV infection and disease rates are elevated in high-risk patients with delayed CMV-specific T-cell immune reconstitution and lower in those with early recovery of T-cell immunity. We recommend preferring CMV seropositive donors for CMV seropositive recipients, as this should lead to durable CMV-specific T-cell responses soon after transplantation with consecutive protection from CMV disease.

Replacement of calcineurin inhibitors with daclizumab in patients with transplantation-associated microangiopathy or renal insufficiency associated with graft-versus-host disease

Transplantation-associated microangiopathy (TAM) or renal insufficiency (RI) after allogeneic hematopoietic stem cell transplantation is associated with a high mortality. As calcineurin inhibitors (CI) may contribute to TAM or RI, we evaluated the efficacy of replacing CI by daclizumab in patients with graft-versus-host disease (GVHD). Thirteen patients with GVHD-associated TAM and five patients with RI were treated with daclizumab 1 mg/kg intravenous (i.v.)/week, discontinuation of the CI and continuation of the remaining GVHD treatment. All patients had acute GVHD (steroid-sensitive (n=4), steroid-refractory (n=10)) or chronic GVHD (n=4) and were treated with CI before the start of daclizumab. Nine of 13 patients with TAM treated with daclizumab and discontinuation of CI achieved complete remission of TAM, two had stable disease, and one patient did not respond. Patients receiving daclizumab for RI without TAM showed stabilization (2/5) or improvement (3/5) of renal function. Four of 14 patients with acute GVHD achieved CR, two partial remission, eight patients did not respond and 11/14 died at a median of 39 days after start of the daclizumab. Our data demonstrate that replacement of CI by daclizumab can improve TAM and RI. However, mortality remains high in patients with acute GVHD.

Clinical and immune responses of WT1-peptide vaccination in patients with acute myeloid leukemia

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Background: The transcription factor Wilms tumor protein (WT) 1 belongs to a new generation of tumor antigens, as it is essential for tumor cell proliferation. WT1 is highly expressed both in myeloid leukemias and many carcinomas. This phase 2 proof-of-concept trial was initiated to determine immunogenicity and toxicity of vaccination with a novel HLA-A2-restricted WT1 peptide vaccine. Methods: Sixteen HLA-A2-positive patients with acute myeloid leukemia and one patient with myelodysplasia received 3–18 vaccinations (median 8) of WT1. 126–134 peptide (0.2 mg) together with the T helper protein keyhole limpet hemocyanin (1 mg) and in addition GM-CSF (75 mcg for four days) and. Twelve patients had elevated blast counts at study entry and 5 patients complete remission with high risk for relapse. Results: Six of 12 patients with presence of leukemic blasts had evidence of antileukemic activity. One patient achieved complete remission for 12 months. The patient with myelodysplasia RAEB II had a major response of neutrophils and platelets. Two patients had minor responses with transient clearance of peripheral blasts or improvement of hematopoiesis, and two patients achieved disease stabilization for 3 and 14 months. WT1 transcripts as molecular disease marker decreased in 5 of these 6 patients and also in 4 of 5 high-risk patients. No significant toxicity occurred. The generation of a WT1-specific T cell response in peripheral blood and bone marrow was detected in 9 of 13 patients by tetramer analysis and 8 of 13 patients by intracellular cytokine staining. Conclusion: These results show that WT1 vaccination can induce functional T cell responses associated with antileukemic activity and warrant trials of WT1 vaccination in patients at high risk of relapse and with WT1-expressing carcinomas.

No significant financial relationships to disclose.

Allogeneic hematopoietic cell transplantation following conditioning with 90Y-ibritumomab-tiuxetan

Radioimmunotherapy (RIT) of relapsed lymphoma is gaining increasing importance. Especially the commercially available anti-CD20 antibody 90Y-ibritumomab tiuxetan is currently under investigation in various trials including dose escalation and autologous hematopoietic progenitor cell support. It is not clear, however, whether the implementation of this radiolabeled antibody into another treatment option for relapsed or poor risk lymphoma patients-allogeneic hematopoietic cell transplantation-interferes with or delays successful engraftment. This study reports encouraging results with 2 relapsed lymphoma patients (1 transformed marginal zone lymphoma and 1 mantle cell lymphoma) who underwent allogeneic hematopoietic cell transplantation from HLA-matched donors. The conditioning regimen consisted of Rituximab 250 mg m(-2) on days -21 and -14, 0.4 mCi kg(-1) body weight 90Y-ibritumomab tiuxetan on day -14 and fludarabine (30 mg m(-2)) plus cyclophosphamide (500 mg m(-2)) on days -7 to -3. The data demonstrate that engraftment is fast and reliable with leukocytes >1 x 10(9) L(-1) on day 12 and platelets >50 x 10(9) L(-1) on day 10. Thus, the incorporation of radioimmunotherapy into allogeneic transplant protocols combines established modalities with proven anti-lymphoma activity and, hence, offers an attractive new therapeutic option for relapsed lymphoma patients.

Graft-vs-leukemia activity and graft-vs-host disease induced by allogeneic Th1- and Th2-type CD4+ T cells in mice

INTRODUCTION

The transfer of allogeneic lymphocytes contained in a hematopoietic stem cell graft confers an immune-mediated antileukemic effect, termed the graft-vs-leukemia (GVL) effect. Graft-vs-host disease (GVHD), the most detrimental complication of allogeneic BMT, largely resides within the same lymphocyte population. Therefore, separation of GVL- and GVH-reactions is a long-standing goal of experimental studies dealing with allogeneic transplantation of hematopoietic stem cells.

MATERIALS AND METHODS

The objective of the current study was to assess the potential of Th1- and Th2-type CD4+ T cells in mediating GVHD and GVL effects in a fully allogeneic murine transplant model. BALB/c (H-2d) mice were given a dose of A20 (H-2d, B-cell leukemia) cells two days prior to lethal total body irradiation (TBI) and transplantation of fully mismatched (C57BL/6, H-2b) T-cell depleted (anti-Thy1.2, CD90) bone marrow (TCD-BM) cells. Graded numbers of either unmanipulated, Th1- or Th2-polarized highly enriched CD4+ donor type T cells (10(6) or 10(7)) were administered 2 h posttransplant. Infusion of 10(6) of unmanipulated, Th1-, or Th2-primed CD4+ T cells resulted in moderate GVHD-related mortality (40%, 50%, 10%) and significantly improved long-term survival (50%, 45%, 46% surviving the observation period of 120 days) as compared to animals receiving TCD-BM alone (18%).

RESULTS

The administration of 10(7) unmanipulated or Th1-type CD4+ T cells given shortly after transplantation led to death of all mice within 50 days due to fatal acute GVHD. In contrast, the adoptive transfer of 10(7) Th2-primed CD4+ T cells resulted in significant improvement of long-term survival (80%) compared to the TCD-BM group. This powerful GVL effect was associated with a substantially lower incidence of lethal acute GVHD (10%) if compared to the results of transplantation of Th1-type CD4+ T cells.

CONCLUSION

These results demonstrate that allogeneic Th2-type CD4+ T cells given post BMT can induce GVL effects in a cell-dose-dependent manner without increasing the risk of severe acute GVHD.

CD56dimCD16neg cells are responsible for natural cytotoxicity against tumor targets

The activation of natural killer (NK) cells leads to degranulation and secretion of cytotoxic granula. During this process, the lytic granule membrane protein CD107a becomes detectable at the cell surface. Based on this phenomenon, we have analyzed by a novel flow cytometry-based assay, the number and phenotype of NK cells responding to tumor targets. Using human leukemia and lymphoma cell lines, we observed a close correlation between CD107a surface expression and target cell lysis, indicating that NK cell cytotoxicity can be assessed by this method. The number of degranulating NK cells was closely related to the ratio of effector and target cells and showed a maximum at a ratio of 1:1. Moreover, we were able to show that the population of CD56(dim)/CD16(neg) NK cells is primarily responsible for the cytotoxic activity against tumor targets whereas neither CD56(dim)/CD16(pos) nor CD56(bright) NK cells degranulated in response to the cell lines. Our results indicate that the CD107a assay represents a promising new method for the quantification and characterization of cells exhibiting natural cytotoxicity.

Use of natural killer cells in hematopoetic stem cell transplantation

Adoptive immunotherapy using natural killer (NK) cells may prove useful, especially in situations where infusion of T cells is impractical such as in recipients of haploidentical stem cell transplantation (HSCT) from haploidentical donors. NK cells may induce potent antileukemic and possibly antirejection activity and may even mitigate graft versus host disease (GvHD). Whether such effects are clinically important and whether they are mediated mainly or exclusively by KIR-HLA class I interactions remains to be determined. Recent advances in graft engineering provide for methods to isolate large numbers of purified NK cells. Several groups have shown that clinical grade NK cells up to a dose of 10(7)/kg may be collected and purified for the purpose of infusion to patients. Early results, in a limited number of patients, show that these cell doses may be administered without adverse events and without inducing GvHD. Whether such infusions will be useful in preventing graft rejection, or exerting graft versus leukemia effects and hastening immune recovery requires further study.

BCR-ABL transcripts are early predictors for hematological relapse in chronic myeloid leukemia after hematopoietic cell transplantation with reduced intensity conditioning

Kinetics of BCR-ABL transcript elimination and its prognostic implications on relapse were analyzed in patients with chronic myeloid leukemia (CML) after reduced intensity hematopoietic cell transplantation (HCT). In all, 19 CML patients were conditioned with 2 Gy total-body irradiation in combination with (n=14) or without (n=3) fludarabine 3 x 30 mg/m(2) (Flu) or 4.5 Gy total lymphoid irradiation (TLI) with Flu and OKT3 3 x 5 mg (n=2) and were treated with cyclosporine (CSP) and mycophenolate mofetil after allogeneic HCT. BCR-ABL transcripts were analyzed by nested RT-PCR and Taqman((R)) RT-PCR on days +28, +56 and +84 after HCT and were evaluated for their association with relapse. Of the 19 patients, 14 achieved sustained remissions of which six had a negative RT-PCR 28 days after HCT. Five patients relapsed +41, +54, +57, +136 and +234 days after HCT. Predictors for relapse were advanced disease stage (P=0.02) and slow reduction of BCR-ABL transcripts at day 28 (P=0.006) and day 56 (P=0.047) post-transplant. We conclude that a complete clearance of BCR-ABL transcripts is achievable within 4 weeks from HCT even after minimal conditioning and that early kinetics of BCR-ABL transcripts significantly correlate with the probability of hematological relapse.

Enhanced antileukemic activity of allogeneic peripheral blood progenitor cell transplants following donor treatment with the combination of granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) in a murine transplantation model

Allogeneic peripheral blood progenitor cells (PBPCs) have mostly been mobilized by granulocyte colony-stimulating factor (G-CSF). There is neither clinical nor experimental data available addressing the question if other hematopoietic growth factors or combinations thereof might influence engraftment, graft-versus-host disease (GvHD), and graft-versus-leukemia (GvL) effects after allogeneic peripheral blood progenitor cell transplantation (PBPCT). We used a murine model to investigate these parameters after transplantation of PBPCs mobilized with G-CSF and SCF either alone or in combination. Treatment of splenectomized DBA and Balb/c mice with 250 microg/kg/day G-CSF for 5 days resulted in an increase of CFU-gm from 0 to 53/microl. The highest progenitor cell numbers (147/microl) were observed after treatment with 100 microg/kg/day SCF administered in conjunction with G-SCF. No differences were detected with regard to the number of T cells (CD3+), T cell subsets (CD4+, CD8+), B cells (CD19+) and NK cells (NK1.1+) in PBPC grafts mobilized by G-CSF plus SCF compared to those mobilized with G-CSF alone. The antileukemic activity of syngeneic and MHC-identical allogeneic PBPC grafts was investigated in lethally irradiated Balb/c mice bearing the B-lymphatic leukemia cell line A20. In this model, PBPCs mobilized by G-CSF plus SCF exerted a significantly higher antileukemic activity compared to grafts mobilized by G-CSF alone (94 vs 71% freedom from leukemia at day 100, P<0.05). The antileukemic effect was lowest after BMT (38% freedom from leukemia). Since significant differences in the incidence of lethal GvHD were not observed, improved GVL-activity resulted in superior overall survival. Our data demonstrate that the utilization of specific hematopoietic growth factors not only improve the yield of hematopoietic progenitor cells but can also significantly enhance the immunotherapeutic potential of allografts.

Idiotype protein-pulsed dendritic cells produce strong anti-myeloma effects after syngeneic stem cell transplantation in mice

Dendritic cell (DC) vaccination represents an interesting immunotherapeutic option in the treatment of several malignancies. In multiple myeloma (MM) patients, vaccination with autologous idiotype (Id) protein-pulsed DC is feasible, but their antitumoral effectiveness was rather limited. To improve the therapeutic potential of DC therapy, we studied the immunological effects of syngeneic peripheral blood stem cell transplantation (PBSCT) given in conjunction with Id-loaded DC. Balb/c mice were inoculated i.p. with 5 x 10(5) of HOPC myeloma cells (Balb/c origin). Animals were immunized with three injections of 5 x 10(5) DC pulsed with the IgG2a(HOPC) or with a control immunoglobulin (Ig(control)). Some experimental groups of myeloma-bearing animals received total body irradiation (7.5 Gy) and a subsequent transplant of 2 x 10(7)syngeneic peripheral blood progenitor cells (PBPC) followed by DC therapy beginning at day 10 post transplant. Animals receiving DC therapy or syngeneic PBPCT alone neither induce long-term survival nor tumor-specific CTL reactivity in vitro. In marked contrast, combination of syngeneic PBPC transplantation and subsequent DC therapy resulted in 78% survival after a follow-up of 180 days. In addition, this treatment modality conferred a generation of Id peptide-specific CD8-mediated T cell reactivity. These data provide a rationale for DC-based vaccination in multiple myeloma patients administered post syngeneic transplantation.

Activation of natural killer cells with interleukin 2 (IL-2) and IL-12 increases perforin binding and subsequent lysis of tumour cells

Natural killer (NK) cells can lyse a variety of different tumour cells by exocytosis of perforin, subsequent binding of perforin to the target cell membrane and formation of lytic pores. Some tumour cells, however, are resistant to cellular cytotoxicity. Using the NK-resistant tumour cell lines ML-2, MONOMAC-1, RPMI and L540Cy, we demonstrated that activation of NK cells with interleukin 2 (IL-2) and IL-12 resulted in significant lysis of these tumour targets. To investigate the underlying mechanisms, we isolated the cytotoxic granules from non-activated and IL-2-/IL-12-activated NK cells and compared the killing of K562 leukaemia cells (sensitive to NK cell-mediated lysis) and ML-2 leukaemia cells (resistant to NK cell-mediated lysis). In contrast to K562 cells, which were easily killed by NK-cell granules, ML-2 cells were resistant to granules from non-activated NK cells. However, granules from NK cells activated with IL-2 and IL-12 were able to induce significant tumour cell lysis. Cell death of both K562 and ML-2 cells by granules from activated NK cells was completely blocked by anti-perforin antibodies, indicating that perforin mainly accounts for the lysis induced by NK granules. Comparing granules from non-activated and IL-2-/IL-12-activated NK cells, the increased cell death of ML-2 cells was caused by an improved binding of perforin to the target cell membrane. Functional assays, however, indicated that the differences in perforin binding were not as a result of an augmented production of perforin by activated NK cells. We conclude that activation of NK cells results in an increased binding of perforin and subsequent lysis of tumour cells.

Transfer of idiotypic protein primed allogeneic marrow grafts elicits potent graft-versus-myeloma effects in mice

The active immunization of bone marrow (BM) donors with myeloma immunoglobulin (Ig) results in an idiotypic T cell response that can be transferred to the recipient. Using a murine model we evaluated the effectiveness, side-effects and underlying mechanisms of this approach. Balb/c (H-2d) mice were given a dose of HOPC-1F myeloma cells secreting the monoclonal IgG2a followed by lethal total body irradiation (7.5 Gy) 2 days later and a subsequent transplantation of 2 x 10(7) allogeneic MHC-matched DBA/2-derived marrow cells. Donors were pre-immunized with three i.p. injections of HOPC(IgG2a) or control Ig given with incomplete Freund's adjuvants (IFA) spaced 1 week apart. In some experiments, donor-spleen cells were additionally transferred 2 h post transplant. Injection of HOPC-myeloma led to death of all animals after a median survival time (MST) of 42 days. A lethal dose of TBI followed by transfer of unmanipulated marrow grafts plus splenocytes resulted in moderate antimyeloma effects with 8% of mice achieving long-term survival. Nearly the same results were obtained after transplantation of BM immunized with the control Ig. In contrast, transplantation of marrow grafts from HOPC(IgG2a) immunized donors exerted a significant GVM effect with 63% long-term survival for more than 180 days. The additional transfer of 2 x 10(7) immune splenocytes derived from the same donor resulted in even stronger anti-myeloma effects (FFR 87%). No increase in the incidence of severe acute GVHD was observed. In vitro data suggest that allogeneic CD8+ idiotype-specific T cells may be the major effector cells. Our results demonstrate that active immunization of the donor with the myeloma-specific Ig can induce powerful graft-versus-myeloma effects after allogeneic BMT.

Impaired binding of perforin on the surface of tumor cells is a cause of target cell resistance against cytotoxic effector cells

Exocytosis of perforin, subsequent binding of perforin to the target cell membrane, and formation of lytic pores form an important pathway involved in the induction of tumor cell death by cytotoxic effector cells. Here we describe a novel escape mechanism employed by tumor cells to protect themselves from granule-mediated cell death: We were able to demonstrate that the resistance of the human leukemia cell line ML-2 to natural killer (NK)-cell-mediated killing is not caused by impaired NK-cell activation but by resistance against effector molecules contained in the granules of cytotoxic cells. No resistance was observed against other pore-forming agents like complement and streptolysin O. By using the NK-susceptible leukemia cell line K562, we could show that the induction of cell death by cytotoxic granules can be blocked completely by anti-perforin antibodies, indicating that perforin is essentially involved in this process. Flow cytometric data revealed that an impaired binding of perforin on the tumor cell membrane is mainly responsible for target cell resistance, because perforin turned out to bind well on K562 cells but is not able to attach to the surface of ML-2 cells. After impaired binding of perforin was identified as a potential mechanism of tumor cell resistance, leukemia cells from 6 patients with acute myeloid leukemia (AML) were examined. As predicted, AML cells that failed to bind perforin on their surface demonstrated complete resistance toward NK-cell-mediated cytotoxicity. Thus, perforin resistance could represent an important tumor escape mechanism that should be considered when cytotoxic effector cells are used for cellular immunotherapy. (Blood. 2000;96:594-600)

Autografting of highly purified peripheral blood progenitor cells following myeloablative therapy in patients with lymphoma: a prospective study of the long-term effects on tumor eradication, reconstitution of hematopoiesis and immune recovery

In a prospective study, we have investigated CD34+ selection of peripheral blood progenitor cells (PBPC) for autotransplantation in patients with lymphoma. Twenty-six consecutive patients (10 follicular lymphomas, seven mantle cell lymphomas, seven B-CLL, two immunocytomas) were mobilized using chemotherapy plus G-CSF. Sufficient numbers of PBPC could be collected from 24 patients and were immunoselected with the semiautomated Isolex 300 (n = 17) or the fully integrated Isolex 300i (n = 7) devices. The selection products were assayed by PCR amplification of clonal CDRIII or t(14;18) rearrangements for residual tumor cell content. Residual disease and long-term hematopoietic and immune recovery were studied by assessing the following parameters at 3, 6, and 12 months post-transplant: CDRIII or t(14;18) PCR, platelet count, lymphocyte subsets, serum IgG, serum IgA, and measles titer. With the Isolex 300 device 26% (10-65) of input CD34+ cells were recovered with a median purity of 89.2% (49.4-98.9) after CD34+ selection. The Isolex 300i device allowed significantly better recoveries (46% (22-86)) and purities of CD34+ cells (98.8% (92.2-99.2)). The overall purging efficacy was 3.2 (0.6-5.1) log. Twenty patients have been reinfused with CD34+ selected grafts after myeloablative preparation. Rapid engraftment occurred in all patients. With a median follow-up of 28 (19-42) months, 14 patients are alive without clinical or molecular evidence of disease recurrence, whereas five have relapsed and one additional patient shows persistent presence of the disease-specific molecular marker without clinical progression. Cellular and serological parameters of hematopoietic and immune functions were largely normal at 12 months post-transplant including the measles titer which was present in all patients. Kinetics of immunohematopoietic recovery were similar to those of 12 control patients who had received unmanipulated PBPC during the same time period except for the recovery of CD4+ CD45RA+ T cells which was significantly delayed in the CD34+ group. During the first year post-transplant, transient monoclonal or oligoclonal gammopathies were observed in seven of 16 study patients. We conclude that CD34+ selection with the Isolex system allows preparation of highly purified CD34+ fractions and effective tumor cell depletion. The CD34+ products can be reinfused safely after myeloablative treatment and result in sustained hematopoietic and immune recovery. The fact that all patients retained their specific measles immunity suggests that myeloablative treatment with reinfusion of highly purified CD34+ PBPC is not immunoablative.

Investigating the lysis of small-cell lung cancer cell lines by activated natural killer (NK) cells with a fluorometric assay for NK-cell-mediated cytotoxicity

Activation of natural killer (NK) cells with interleukin-2 (IL-2) and IL-12 leads to an enhanced lysis of tumour cells. We investigated the ability of NK cells, with or without prior activation, to lyse a variety of small-cell lung cancer (SCLC) target cells. Specific lysis was measured with a fluorometric assay for NK-cell-mediated cytotoxicity: target cells were labelled with 3,3'-dioctadecyloxacarbocyanine, a green membrane dye. After co-incubation with NK cells, dead target cells were stained with propidium iodide, a red DNA dye that only penetrates dead cells. Of all eight SCLC cell lines tested, three were susceptible to lysis by non-activated NK cells, three were only susceptible to lysis by NK cells activated with IL-2 and IL-12 and two were not even susceptible to lysis by activated NK cells. The differences in target cell susceptibility showed no correlation with the expression of MHC-I on the surface of the target cells or with the expression of the adhesion molecules CD50, CD54, CD58 or CD102. Comparing the kinetics of the lysis of one SCLC cell line sensitive to non-activated NK cells and one sensitive only to activated NK cells, we found that maximum lysis of the former was obtained after 1 h, whereas significant lysis of the latter was only obtained after 4 h of incubation. This might be due to different mechanisms engaged in target cell lysis.

Eradication of residual disease by administration of leukemia-specific T cells after experimental allogeneic bone marrow transplantation

It is now well established that allogeneic lymphocytes can mediate a potent graft-vs.-leukemia (GVL) reaction when administered to bone marrow transplant (BMT) recipients. The benefit of allogeneic lymphocyte transfusion is limited because many patients develop graft-vs.-host disease (GVHD) with prolonged pancytopenia, which sometimes proves fatal. The object of the present study was to determine the antileukemic potential and GVHD risk of in vivo-generated tumor-specific allogeneic T cells given shortly after BMT. BALB/C (H-2d) mice were inoculated with different cell doses (10(5) and 5 x 10(5)) of the A20 leukemia (BALB/C origin) 2 days prior to lethal total-body irradiation (TBI) and transplantation of allogeneic, major histocompatibility complex (MHC)-matched DBA marrow grafts (H-2d, minor difference to BALB/C). Donors of BM grafts and T cells were allogeneic, MHC-matched mice (DBA, H-2d, minor difference to BALB/C). Donor-type T cells were generated from mice immunized with irradiated A20 leukemia cells or nonmalignant BALB/C splenocytes and restimulated in vitro. Whereas no significant immunotherapeutic effect was seen in mice with high tumor burden (5 x 10(5)), allogeneic BMT in mice inoculated with 1 x 10(5) A20 cells resulted in a modest antileukemic effect. This survival rate remained unchanged when 10(6) T cells obtained from donors immunized with nonmalignant BALB/C derived cells were given posttransplantation. In contrast, a single injection of 10(6) T cells from leukemia-immunized donors led to potent GVL effects without mediating clinically overt GVHD. Our data provide evidence for the hypothesis that minimal residual disease can be eradicated without inducing GVHD by administering small amounts of specific allogeneic cytotoxic T cells after BMT.

Immunotherapeutic aspects of allogeneic peripheral progenitor cells

In a newly developed murine model of allogeneic peripheral progenitor transplantation (PBPCT) we investigated the immunotherapeutic potential of allogeneic peripheral stem cells. The following topics were addressed by our experiments: (1) comparison of the graft-versus-leukemia effect exerted by allogeneic PBPCT compared to allogeneic BMT; (2) the influence of T-lymphocytes on GVL activity; (3) the possibility to enhance the GVL activity of allogeneic PBPCT grafts by ex vivo cytokine incubation. Balb/c mice received cells of the syngeneic B-lymphatic leukemia A20 2 days prior to TBI (7.5 Gy) and the respective graft. The recipients received allogeneic bone marrow grafts or allogeneic peripheral progenitor cells obtained after mobilization of the donors (DBA/2) with either G-CSF in a dose of 250 microg/kg/day for 5 days. In some experiments T lymphocytes were removed by immunomagnetic depletion with CD3-coated beads. An additional group received T cell-depleted and IL-2/IL12-activated PBPCT grafts. The antileukemic activity of an allogeneic PBPCT graft was significantly greater than the antileukemic activity of an allogeneic BMT graft of the same size. Relapse rates were 80% in syngeneic PBPCT, 60% after allogeneic BMT and 34% after allogeneic PBPCT. This rise in antileukemic activity is not accompanied by a rise in GVHD mortality. Depletion of T lymphocytes by CD3-coated beads resulted in a nearly complete loss of the GVL activity with a relapse rate of 75%. Incubation of the T-depleted graft with IL-2 and IL-12 to enhance NK-based GVL activity has only limited success after MHC-matched transplantation with a relapse rate of 55%. Allogeneic PBPC exert a pronounced antileukemic effect. After MHC-matched PBPCT, this GVL effect resides mostly on the T cells of the graft. Ex vivo activation of T cell-depleted grafts by IL-2 and IL-12 is accompanied by an only limited reduction of relapse rate. PBPC are a valuable modality for primary transplantation in situations with high risk of relapse and for the treatment of relapse after BMT.

Superior antileukemic activity of murine peripheral blood progenitor cell (PBPC) grafts mobilized by G-CSF and stem cell factor (SCF) as compared to G-CSF alone

We have established a murine model to compare the antileukemic effect of PBPC grafts obtained after treatment with SCF + G-CSF and G-CSF alone. C57/BL6, DBA and Balb/c mice were splenectomized and injected with optimal doses of rhG-CSF (250 microg/kg/day s.c.) or rrSCF (100 microg/kg/day s.c.) or with a combination thereof. On day 5, we determined the hematopoietic potential (number of CD34+ cells, CFUs, total CFC, CFU-gm), the proportion of lymphoid (T, NK and B cells) and myeloid components and graft-versus-leukemia activity after allogeneic and syngeneic PBPCT and BMT in Balb/c mice bearing a B-lymphoblastic leukemia cell line (A20). The absolute number of progenitor cells increased two-fold after administering a combination of G-CSF and SCF as compared to G-CSF alone (1500 vs 940 CD34+ cells/microl; 190 vs 70 total CFC/microl; 150 vs 50 CFU-gm/microl and 6600 vs 3000 CFUs/ml). Although no differences could be detected in the cellular composition, especially in the number of T cells, PBPC grafts mobilized by the combination of G-CSF + SCF demonstrated significantly higher antileukemic activity compared to G-CSF alone (94% vs 71% freedom from leukemia, P < 0.05). Because the incidence of lethal GVHD was similar in both groups, improved GVL activity resulted in superior overall survival. Our data suggest that the higher number of progenitor cells can be harvested after G-CSF + SCF and that grafts mobilized by G-CSF + SCF exert significantly enhanced antileukemic activity compared to those harvested after treatment with G-CSF alone.

Early stem cell transplantation for chronic lymphocytic leukaemia: a chance for cure?

B-cell chronic lymphocytic leukaemia (CLL) cannot be cured by conventional therapy. To improve the prognosis of patients with CLL, we have designed a sequential treatment strategy that comprises intensive chemotherapy for mobilization of peripheral blood progenitor cells (PBPCs) and induction of minimal disease, followed by high-dose radiochemotherapy with stem cell reinfusion and post-transplant molecular monitoring by polymerase chain reaction (PCR) amplification of the complementary determining region III (CDRIII) gene. In a prospective study, we have evaluated this protocol in 18 patients with CLL, also including early stages of the disease. The median age was 49 (29-61) years; Binet stages were A, six; B, nine; and C, three. Adverse prognostic factors [high lymphocyte count and/or diffuse bone marrow (BM) infiltration] were present in 16 out of 18 patients. All patients showed a clone-specific molecular marker as demonstrated by PCR amplification of CDRIII rearrangements. For stem cell mobilization and reduction of tumour load, one to two cycles of Dexa-BEAM chemotherapy were administered, resulting in minimal disease (circulating lymphoma cells <1 x 10(9) l(-1); BM infiltration <20%; lymphomas <2 cm) in 16 out of 18 patients, including four patients who already had minimal disease before Dexa-BEAM. Stem cell harvesting was successful in 14 patients. All grafts [three BM, 11 peripheral blood (PB)] were purged from leukaemic cells using immunomagnetic methods. Thirteen patients having achieved minimal disease were reinfused with purged autologous stem cells (ASC) after preparation with total body irradiation and cyclophosphamide. Engraftment was delayed in patients receiving BM (n = 3) but prompt [neutrophils >0.5 x 10(9) l(-1) after 10 (9-13) days, platelets >20 x 10(9) l(-1) after 11 (9-214) days] in patients restored with PBPCs (n = 10). Procedure-related deaths did not occur. Although the results of CDRIII PCR suggest persistence or recurrence of the leukaemic clone in at least three cases, to date only one patient has relapsed, whereas all others survive without clinical evidence of disease with a maximum follow-up of 48 months. We conclude that sequential high-dose therapy using Dexa-BEAM and autologous stem cell transplantation is a safe and highly effective treatment for patients with CLL. However, a longer follow-up is needed to assess whether definite cures can be achieved using this strategy.

Abrogation of graft-vs.-leukemia activity after depletion of CD3+ T cells in a murine model of MHC-matched peripheral blood progenitor cell transplantation (PBPCT)

Using a murine transplantation model, we simulated a clinical situation in which major histocompatibility complex (MHC)-identical allogeneic peripheral blood progenitor cells (PBPCs) are transplanted for the treatment of a malignant disease that is resistant to resting natural killer (NK) cells but sensitive to cytokine-activated NK cells and T cell-mediated antitumor activity. We determined the influence of selective T cell depletion of allogeneic PBPC grafts on graft-vs.-leukemia (GVL) activity and investigated the effectiveness of ex vivo treatment with NK cell-activating cytokines to compensate for the putative loss of T cell-derived factors stimulating natural cytotoxicity. After pretreatment of Balb/c (H-2d) recipients with 7.5 Gy of total body irradiation, 2x10(7) rhG-CSF-mobilized PBPCs of splenectomized syngeneic or MHC-identical DBA (H-2d) mice were transferred. Selective T cell depletion (TCD) was performed by immunomagnetic purging with a mononoclonal antibody directed against CD3. In some experimental groups, T cell-depleted PBPCs were incubated with 200 U/mL interleukin (IL)-2 and 100 U/mL IL-12 for 24 hours. To investigate antileukemic activity in vivo, recipient mice were inoculated with 1x10(5) A20 cells (a B-lymphoblastic leukemia of Balb/c origin) 2 days before PBPC transplantation (PBPCT). After transplantation of unmanipulated allogeneic cells, 25% of the animals died with signs of graft-vs.-host disease (GVHD) but 71% were free from relapse 100 days after PBPCT. After TCD of allogeneic grafts with anti-CD3, the incidence of GVH-related mortality was below 5% but the leukemia-free survival rate was significantly (p < 0.05) decreased to 25% and thus was similar to that observed after syngeneic PBPCT (17%). When CD3-depleted grafts were incubated with IL-2 and IL-12, 45% of the animals remained free from leukemia; however, the difference was not statistically significant. Our results suggest that ex vivo activation of residual NK cells with IL-2 and IL-12 does not fully compensate for the abrogation of GVL activity after depletion of CD3+ T cells from MHC-matched PBPCT.

Allogeneic peripheral blood progenitor cell transplantation in a murine model: evidence for an improved graft-versus-leukemia effect

Peripheral blood progenitor cells (PBPCs) are increasingly being used to replace bone marrow cells (BMCs) as a source of hematopoietic stem cells also in the field of allogeneic transplantation. Whereas it is well known that PBPC grafts and BM differ significantly in progenitor cell content and lymphocyte dose, the clinical consequences of these differences with respect to engraftment, graft-versus-host disease (GVHD), and the graft-versus-leukemia (GVL) effect are more difficult to assess. We present a murine model that allows us to evaluate engraftment, GVHD, and GVL effect of allogeneic PBPC transplantation (PBPCT). Balb/c mice (H-2d) served as recipients. Donors were major histocompatibility complex-matched DBA/2 mice or syngeneic Balb/c mice, respectively. Experiments with increasing numbers of BMCs or Filgastrim-mobilized PBPCs showed that the number of progenitor cells in the graft was correlated with the probability to engraft, irrespective of the graft type. With identically high cell numbers transferred (1 x 10(9) nucleated cells/kg body weight [BW]), the mortality rates due to GVHD (25%) were about the same after allogeneic BM transplantation (BMT) and allogeneic PBPCT, although PBPC grafts contained four times more CD3+ T cells as compared with BM grafts (6.2 x 10(8) v 1.4 x 10(8)/kg BW). For investigation of GVL activity, Balb/c recipients were injected with syngeneic cells of the B-lymphocytic leukemia cell line A20 2 days before transplantation. After total body irradiation to a dose of 7.5 Gy, 1 x 10(9)/kg BW Balb/c PBPCs, DBA BMCs, or DBA PBPCs were infused. The relapse rates observed were 80% after syngeneic PBPCT (n = 22), 60% after allogeneic BMT (n = 23), and 34% after allogeneic PBPCT (n = 26) (allogeneic BMT v PBPCT, P = .032). We conclude that transplantation of allogeneic PBPCs instead of BM may enhance the GVL effect without an increase of GVHD.

Allogenic transplantation of mobilized peripheral blood progenitor cells: towards tailored cell therapy

Mobilized peripheral blood prognitor cells (PBPC) are increasingly being used instead of bone marrow for allogeneic transplantation. The present article will briefly review important aspects of allogeneic PBPCT including, donor safety, timing of leukapheresis, factors influencing the yield, cellular composition of PBPC allografts, hematopoietic capacity of allogeneic PBPC, and graft-versus-host and graft-versus-leukemia activities. It will particularly focus on the perspectives opened by PBPC for graft engineering and cell therapy.

Sequential high-dose therapy and autologous stem cell transplantation for treatment of mantle cell lymphoma

BACKGROUND

Mantle cell lymphoma (MC) is not curable with conventional chemotherapy. To improve the prognosis of patients with this disease, we prospectively studied an intensive sequential therapy consisting of the Dexa-BEAM regimen (dexamethasone, BCNU, etoposide, ara-C, melphalan) followed by myeloablative therapy with autologous stem cell reinfusion.

PATIENTS AND METHODS

Nine consecutive patients with stage III/IV MC were included. Two had untreated disease, four were in first remission, whereas three had more advanced disease. All patients underwent one to two cycles of Dexa-BEAM chemotherapy to reduce the tumor load and to mobilize peripheral blood progenitor cells (PBPC). Subsequently, patients were treated with high-dose radiochemotherapy followed by PBPC reinfusion and were prospectively analyzed for residual disease by clinical methods as well as by PCR amplification clonal CDRIII rearrangements.

RESULTS

With an overall response rate of 100%, the initial Dexa-BEAM cycles effectively reduced the tumor load. All patients proceeded to high-dose therapy and subsequent stem cell rescue. Engraftment was prompt, and procedure-related deaths did not occur. With a median follow-up of 12 (3-33) months post transplant, all patients are alive in continuing clinical and molecular remission.

CONCLUSIONS

Sequential intensive therapy consisting of Dexa-BEAM and high-dose radiochemotherapy appears to be a highly effective treatment for patients with MC. However, the data are still preliminary, and larger patient numbers and a longer follow-up are required.

Allogeneic MHC-mismatched activated natural killer cells administered after bone marrow transplantation provide a strong graft-versus-leukaemia effect in mice

Allogeneic lymphocytes administered with an unmanipulated bone marrow transplant provide a strong antileukaemic effect, the so-called graft-versus-leukaemia (GVL) effect. On the other hand, T-cell-mediated graft-versus-host-disease (GVHD) observed after transplantation of unmanipulated BM graft causes substantial morbidity and mortality. The aim of the present study was to determine the antileukaemic potential of enriched IL-2 activated NK cells administered 2 h after BMT. Balb/c (H-2d) mice were given a dose of A20 (H-2d, B-cell leukaemia) cells 2 d prior to lethal total body irradiation (TBI) and transplantation of either syngeneic or allogeneic anti-Thy1.2 (CD90) depleted bone marrow cells. Either syngeneic (Balb/c, H-2d) or allogeneic (C57BL/6, H-2b) enriched and IL-2 (200 U/ml for 24 h) activated NK cells were given 2 h after BMT. Injection of A20 leukaemia into normal Balb/c recipients led to death after a median of 14 d. A lethal dose of TBI followed by either syngeneic or allogeneic Thy1.2-depleted BMT resulted in a modest antileukaemic effect. The adoptive transfer of syngeneic enriched and IL-2 preincubated NK cells given at time of BMT exerted a significantly better GVL effect. However, the infusion of allogeneic enriched NK cells resulted in a stronger GVL effect. These results clearly demonstrate that allogeneic NK cells are superior to syngeneic NK cells in their potential to eradicate residual leukaemia cells after BMT without mediating clinical overt GVHD. This experimental setting may offer a strategy for treatment of haematological malignancies in a phase of minimal residual disease.

High lytic activity against human leukemia cells after activation of allogeneic NK cells by IL-12 and IL-2

IL-12 is a novel cytokine with interesting features regarding its potential usefulness in peripheral blood stem cell transplantation and leukemia immunotherapy. We used cryopreserved leukemia cells of 18 patients with acute myelogenous (n= 14) or lymphocytic (n= 4) leukemia to investigate the effect of IL-12, alone or in combination with IL-2, on the cytolytic activity of NK cells against human leukemia targets. Effector cells were peripheral blood mononuclear cells from healthy donors which were depleted from CD3+ T cells by immunomagnetic separation. CD3-negative effector cells (mainly CD56+ NK cells) were treated for 24 h with various concentrations of IL-2 (100 U/ml to 1000 U/ml) and IL-12 (1 U/ml to 100 U/ml). Cytotoxicity was measured in a 4 h 51Cr-release assay. Whereas a two-fold enhancement of cytotoxic activity was observed after incubation with optimal doses of IL-2 or IL-12, the combination of both cytokines (500 U/ml IL-2, 100 U/ml IL-12) increased the lytic activity more than six-fold. This effect was accompanied by increased expression of cellular adhesion molecules (CD2, CD18) and CD25 on CD56+ effector cells. Of 18 leukemias investigated, five were completely resistant to lysis by effector cells activated with IL-2 or IL-12 alone. In three of these five cases, however, high cytolytic activity was observed after coincubation with IL-2 and IL-12. In comparison to allogeneic NK cells, autologous cells of three patients in remission demonstrated significantly lower cytotoxic activity. No killing of nonmalignant cells (PHA blasts) by allogeneic NK cells was observed. Our data demonstrate that IL-12 can enhance or even induce MHC-unrestricted cytotoxicity of IL-2-activated allogeneic natural killer cells. Since IL-12 has also been shown to have stem-cell mobilizing capacities, it could be used for the recruitment of both stem cells and antileukemic effector cells in the context of peripheral blood stem cell transplantation.

Allogeneic peripheral blood progenitor cells: current status and future directions

Increasing use is being made of mobilized peripheral blood as a source of hematopoietic stem and progenitor cells for transplantation. Initially, these efforts were focused on autologous applications. However, many centers are now using cells derived from normal donors mobilized with recombinant hematopoietic growth factors for allogeneic transplantation. This article reviews the key issues associated with the use of these cells for hematologic reconstitution and summarizes important recent developments in the field.

Graft-versus-leukaemia activity can be predicted by natural cytotoxicity against leukaemia cells

We have investigated graft-versus-leukaemia (GVL) effects after allogeneic bone marrow transplantation (BMT), using three murine leukaemia models, A20 (B lymphocytic), WEHI-3 (myelomonocytic) and PU5-1R (myeloid). Injection of leukaemia cells in a high number (10(6) cells) into syngeneic Balb/c mice (H-2d) invariably led to death with a median survival time of 22 d (A20), 18 d (WEHI-3) and 45 d (PU5-1R). A lower tumour load of A20 (5 x 10(5) cells) was used in some experiments resulting in a leukaemic death rate of 94%. Lethal total-body irradiation followed by syngeneic BMT prolonged survival (P<0.05) for animals bearing the leukaemia A20 and WEHI-3 but was unsuccessful for animals injected with cells from the monocytic leukaemia PU5-1R. Graft-versus-host (GVH)-nonreactive marrow of (C57 x Balb/c)F1 mice (H2bxd) exerted a significant GVL-effect with reduced relapse rate and improved survival in mice receiving the leukaemia cell line A20. In animals with low tumour load a significant reduction of the relapse rate from 82% following syngeneic BMT to 47% following allogeneic, GVH-nonreactive BMT could be achieved. Depletion of natural killer (NK) cells from the GVL-reactive semi-allogenic bone marrow graft enhances the relapse rate of the leukaemia A20 to 65%. In mice bearing the leukaemias WEHI-3 or PU5-1R allogeneic GVH-nonreactive BMT did not improve survival compared to syngeneic BMT. Transplantation of GVH-reactive bone marrow from DBA mice (MHC identical to Balb/c, minor difference) caused only a limited and insignificant reduction of relapse rate for animals with the leukaemia A20. These in vivo data are in close correlation with in vitro natural killer cell (NK) activity of the donor strains against the respective leukaemia targets. Depletion of NK cells from the GVL-reactive (C57 x Balb/c)F1 bone marrow resulted in a significant loss of GVL activity. We conclude that NK cells are involved in graft-versus-leukaemia effects independent of graft-versus-host disease (GVHD).

Allogeneic mouse T cell lines distinguish three Balb/c leukemias from each other and from non-leukemic lymphocytes

In order to separate graft-versus-leukemia (GVL) effect from graft-versus-host (GVH) reactions in allogeneic cell therapy, we established cytotoxic T cell lines (CTL) against irradiated A20, WEHI-3 and PU cells, ie cells from 3 hematopoietic tumors of Balb/c origin. Immunization with these cell lines did not lead to prolonged survival in Balb/c mice. The cytotoxic activity of the CTL was tested against the 3 leukemias. In all 9 combinations the highest specific lysis was achieved against the stimulating tumor. Cold target inhibition experiments showed that the activity against 51Cr-labelled leukemia cells could be almost completely inhibited by adding a sufficient amount of unlabelled target cells. On the other hand, when unlabelled concanavalin A-induced Balb/c blast cells were added, the inhibition was incomplete. By means of flow cytometry it was excluded that the different susceptibilities and inhibitory potentials of tumor cells and nonmalignant blasts are caused solely by differences in the MHC expression of the target cells. These findings confirm that allogeneic CTL are capable of discriminating malignant from nonmalignant cells, even if the tumor is nonimmunogenic in syngeneic animals.