Increased efficacy of dual proinflammatory cytokine blockade on acute GVHD while maintaining GVT effects

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a potential curative option for treating a variety of hematologic diseases, but acute and chronic graft-versus-host disease (GVHD) remain major barriers limiting efficacy. Acute gut GVHD occurs with marked increases in proinflammatory cytokines (including TNF and IL-6), which we recently demonstrated was exacerbated in obesity resulting in severe gastrointestinal pathology. Given the pleiotropic and overlapping effects of these 2 cytokines, we assessed the impact of dual TNF and IL-6R blockade on GVHD as well as graft-versus tumor (GVT) effects in different mouse GVHD models. Early administration of combined blockade resulted in greater protection and survival from acute gut GVHD compared with single blockade regimens and even development of later chronic skin GVHD. Importantly, double cytokine blockade preserved GVT effects reinforcing that GVT and GVHD can be delineated and may result in greater efficacy in allo-HSCT.

Allogeneic MHC gene transfer enhances antitumor activity of allogeneic hematopoietic stem cell transplantation without exacerbating graft-versus-host disease

Enhancement of the specific antitumor activity of allogeneic hematopoietic stem cell transplantation (alloHSCT) against solid cancers is a major issue in the clinical oncology. In this study, we examined whether intratumoral allogeneic MHC (alloMHC) gene transfer can enhance the recognition of tumor-associated antigens by donor T cells and augment the antitumor activity of alloHSCT. In minor histocompatibility antigen-mismatched alloHSCT (DBA/2-->BALB/c: H-2(d)) recipients, alloMHC gene (H-2K(b)) was transduced directly into a s.c. tumor of CT26 colon cancer cells. Because CT26 cells have an aggressive tumorigenicity in syngeneic BALB/c mice, an H-2K(b) gene transfer provides only a limited antitumor effect after syngeneic (BALB/c-->BALB/c) HSCT. By contrast, the H-2K(b) gene transfer caused significant tumor suppression in the alloHSCT recipients, and this suppression was evident not only in the gene-transduced tumors but also in simultaneously inoculated distant tumors without gene transduction. In vitro cytotoxicity assay showed specific tumor cell lysis by donor T cells responding to the H-2K(b) gene transfer. Graft-versus-host disease was not exacerbated serologically or clinically in the treated mice, demonstrating that alloMHC gene transfer enhances the antitumor effects of alloHSCT without exacerbating graft-versus-host disease. This combination strategy has important implications for the development of therapies for human solid cancers.

Sustained molecular remission by non-myeloablative stem cell transplantation after autologous hematopoietic stem cell transplantation in a patient with multiple myeloma

Multiple myeloma (MM) is refractory to conventional chemotherapy. To achieve a sustained complete remission, we performed planned non-myeloablative allogeneic stem cell transplantation (NST) after autologous hematopoietic stem cell transplantation (HSCT) in a patient with stage III MM. Autologous HSCT was performed using high-dose melphalan after conventional chemotherapy, followed by NST from an HLA-identical sibling using low-dose total body irradiation (200 cGy) for conditioning. Cyclosporine and mycophenolate mofetil were used for graft-vs-host disease (GVHD) prophylaxis. Acute GVHD was transiently seen in the skin and intestine, while, in addition, mild chronic GVHD was seen in the oral mucosa and skin. Complete donor chimerism was achieved and the disappearance of tumor-derived monoclonal B cells was confirmed based on an analysis of immunoglobulin light chain messenger signals on day 156 when chronic GVHD occurred. The clinical course in this case strongly suggested the existence of a graft-vs-myeloma effect.

Intensive Chemotherapy with Autologous Peripheral Blood Stem Cell Transplantation During a 10-Year Period in 64 Patients with Germ Cell Tumor

Despite gratifying cure rates in germ cell tumors, conventional-dose chemotherapy achieves long-term remissions in less than 50% of patients at high risk. High-dose chemotherapy followed by autologous (auto) peripheral blood stem cell transplantation (PBSCT) has shown impressive remission rates in high-risk and relapsed germ cell tumors. We report on 64 consecutive patients with high- (n=39), intermediate- (n=18), and refractory or relapsed low- (n=7) risk germ cell tumors who underwent auto-PBSCT between January 1993 and February 2003. PBSCTs were performed as a single (n=40) or repeated (n=24) transplantation using either etoposide, ifosfamide, and carboplatin (n=80) or related protocols (paclitaxel, ifosfamide, carboplatin, etoposide [n=7]; carboplatin, etoposide, thiotepa [n=4]). With a median follow-up of 6 years, estimated 2- and 5-year overall survivals were 77.2% (95% confidence interval [CI] 66.7-87.7) and 73.1% (95% CI 61.7-84.5), respectively. We observed unfavorable results in those patients showing refractoriness to cisplatin (hazard ratio 20.36; 95% CI 6.64-62.47) or no response to induction chemotherapy (hazard ratio 10.67; 95% CI 1.37-83.37). Auto-PBSCT was well tolerated, showed objective antitumor activity, and achieved long-term survival in patients at high risk and with relapse. Our data suggest that auto-PBSCT can increase response rates and may improve the outcome in these patients.

A Revision of Billingham’s Tenets: The Central Role of Lymphocyte Migration in Acute Graft-versus-Host Disease

The migration of cells from vascular to extravascular compartments effects a sequential cascade of events, involving an interplay between adhesion molecules and chemokines. All T cell-mediated immune responses, of which acute graft-versus-host disease (GVHD) is an example, require that effector cells reach their target tissues. Lymphocytes do not enter specific tissues because they "see" a given antigen; they enter because they possess the requisite combination of homing receptors and chemokine receptors to engage the endothelium at the target tissue(s). Billingham's tenets on the immunobiology of GVHD must be expanded to accommodate this obligatory homing component. Because GVHD is relatively organ specific--principally affecting the skin, gut, and liver-our increasing knowledge of the pertinent adhesion molecules and chemokines directing effector cell trafficking to these sites offers novel therapeutic approaches for prevention or treatment of GVHD. The potential efficiency of this form of therapy could eliminate the use of graft manipulations (eg, T-cell depletion) and broad immunosuppressives, thereby lessening infectious complications and preserving the potent graft-versus-malignancy effect of allogeneic hematopoietic stem cell transplantation.

Poor outcome of two children with relapsed state stage IV alveolar rhabdomyosarcoma after allogeneic stem cell transplantation

The authors report on 2 boys, 11(1/2) and 13 years old, who received allogeneic stem cell transplantation (alloSCT) from their HLA-identical sibling after relapse of stage IV alveolar rhabdomyosarcoma. Both patients were transplanted in a non-remission status. After alloSCT both patients experienced disease progression at the primary tumor location sites and died due to the underlying disease 146 and 379 days after transplantation. The authors conclude that an alloSCT derived graft versus tumor effect might not be effective enough to overcome alveolar rhabdomyosarcoma when transplantation is carried out in a nonremission status.

Ex vivo rapamycin generates donor Th2 cells that potently inhibit graft-versus-host disease and graft-versus-tumor effects via an IL-4-dependent mechanism

Rapamycin (sirolimus) inhibits graft-vs-host disease (GVHD) and polarizes T cells toward Th2 cytokine secretion after allogeneic bone marrow transplantation (BMT). Therefore, we reasoned that ex vivo rapamycin might enhance the generation of donor Th2 cells capable of preventing GVHD after fully MHC-disparate murine BMT. Using anti-CD3 and anti-CD28 costimulation, CD4+ Th2 cell expansion was preserved partially in high-dose rapamycin (10 microM; Th2.rapa cells). Th2.rapa cells secreted IL-4 yet had reduced IL-5, IL-10, and IL-13 secretion relative to control Th2 cells. BMT cohorts receiving wild-type (WT) Th2.rapa cells, but not Th2.rapa cells generated from IL-4-deficient (knockout) donors, had marked Th2 skewing post-BMT and greatly reduced donor anti-host T cell alloreactivity. Histologic studies demonstrated that Th2.rapa cell recipients had near complete abrogation of skin, liver, and gut GVHD. Overall survival in recipients of WT Th2.rapa cells, but not IL-4 knockout Th2.rapa cells, was constrained due to marked attenuation of an allogeneic graft-vs-tumor (GVT) effect against host-type breast cancer cells. Delay in Th2.rapa cell administration until day 4, 7, or 14 post-BMT enhanced GVT effects, moderated GVHD, and improved overall survival. Therefore, ex vivo rapamycin generates enhanced donor Th2 cells for attempts to balance GVHD and GVT effects.

Tumor antigen immunization of sibling stem cell transplant donors in multiple myeloma

The unique antigenic determinants (idiotype (Id)) of the immunoglobulin secreted by myeloma tumor can serve as a tumor-specific antigen for active immunotherapy. Our objective was to induce tumor-specific T-cell immunity in bone marrow transplant (BMT) donors to enhance antitumor effects of allografts. We vaccinated five HLA-matched sibling donors with myeloma Id proteins isolated from recipient plasma before bone marrow harvest. Recipients were administered booster Id immunizations following transplantation. Vaccination induced donor Id and carrier-specific cellular and/or humoral immune responses. Two recipients died within 30 days of BMT from transplant-related complications. Id and carrier-specific T-cell responses were detected in all three remaining patients post-, but not pre-BMT and persisted for 18 months. All three surviving patients converted from partial to complete responses following BMT. Two of the three patients remain disease-free 7 years and 8 years after BMT, and the third died of renal failure after 5.5 years while in complete remission from myeloma. Our results suggest that myeloma Id vaccination induces specific T-cell immunity in healthy donors which may be transferable by BMT, is associated with prolonged disease-free survival of recipients, and may represent a general strategy to enhance graft-versus-tumor effect in other malignancies for which defined tumor-specific antigens exist.

Graft-versus-tumor effects after allogeneic hematopoietic cell transplantation with nonmyeloablative conditioning

PURPOSE

We have used a nonmyeloablative conditioning regimen consisting of total-body irradiation (2 Gy) with or without fludarabine (30 mg/m(2)/d for 3 days) for related and unrelated hematopoietic cell transplantation (HCT) in patients with hematologic malignancies who were not candidates for conventional HCT because of age, medical comorbidities, or preceding high-dose HCT. This approach relied on graft-versus-tumor (GVT) effects for control of malignancy.

PATIENTS AND METHODS

We analyzed GVT effects in 322 patients given grafts from HLA-matched related (n = 192) or unrelated donors (n = 130).

RESULTS

Of the 221 patients with measurable disease at HCT, 126 (57%) achieved complete (n = 98) or partial (n = 28) remissions. In multivariate analysis, there was a higher probability trend of achieving complete remissions in patients with chronic extensive graft-versus-host disease (GVHD; P = .07). One hundred eight patients (34%) relapsed or progressed. In multivariate analysis, achievement of full donor chimerism was associated with a decreased risk of relapse or progression (P = .002). Grade 2 to 4 acute GVHD had no significant impact on the risk of relapse or progression but was associated with increased risk of nonrelapse mortality and decreased probability of progression-free survival (PFS). Conversely, extensive chronic GVHD was associated with decreased risk of relapse or progression (P = .006) and increased probability of PFS (P = .003).

CONCLUSION

New approaches aimed at reducing the incidence of grade 2 to 4 acute GVHD might improve survival after allogeneic HCT after nonmyeloablative conditioning.

Reconstructing immunity after allogeneic transplantation

A major goal of our research is to reduce the graft-vs-host disease (GVHD) activity of allogeneic donor T cells in bone marrow transplantation (BMT), while preserving graft-vs-tumor (GVT) effects. Using ex vivo immunosuppressive strategies and cell-separation techniques to modulate the graft prior to transplantation, we examined the roles of different donor immune cells on GVHD and GVT effects in allogeneic mouse models. Our results demonstrate that donor-memory CD4 T cells facilitate posttransplant immunological reconstitution without causing GVHD, whereas transplantation of equal numbers of donor naïve CD4 T cells leads to fatal GVHD. The initial events of donor T cells interacting with antigen-presenting cells (APCs) in the transplant recipient appear to be critical to the development of GVT, GVHD, or anergy to alloantigens. In the setting of clinical BMT, increased numbers of donor type 2 dendritic cells (DCs) were associated with an increased rate of posttransplant relapse, and decreased rates of chronic GVHD. In a mouse transplant model, manipulation of the DC content of bone marrow grafts was achieved by depletion of CD11b+ cells. Mice transplanted with CD11b- depleted marrow showed enhanced posttransplant expansion of memory T cells with markedly improved GVT activity and limited GVHD compared to recipients of unmanipulated marrow. A model that differentiates GVT from GVHD based on interaction of T-cell subsets with DC subsets is proposed.

Graft-versus-myeloma effect following antithymocyte globulin-based reduced intensity conditioning allogeneic stem cell transplantation

In all, 41 multiple myeloma (MM) patients received an antithymocyte globulin (ATG), fludarabine, and busulfan-based reduced intensity conditioning (RIC) for allogeneic stem cell transplantation (allo-SCT) from HLA-identical siblings. In total, 29 patients (70%) were in partial remission, one patient in complete remission, and 11 (27%) with progressive disease at the time of allo-SCT. Median time between diagnosis and allo-SCT was 24 months. The cumulative incidences of grade II-IV and grade III-IV acute graft-versus-host disease (GVHD) were 36% (95% CI, 21-51%) and 7% (95% CI, 2-20%), respectively. Overall, 10 patients developed limited chronic GVHD, whereas seven developed an extensive form (cumulative incidence, 41% (95% CI, 26-56%) at 2 years). With a median follow-up of 389 days, the overall cumulative incidence of transplant-related mortality (TRM) was 17% (95% CI, 6-28%). In all, 11 patients (27%) are in continuous complete remission, and the Kaplan-Meier estimates of overall survival (OS) and progression-free survival (PFS) at 2 years were 62% (95% CI, 47-76%) and 41% (95% CI, 23-62%), respectively. PFS and OS were significantly higher in patients with chronic GVHD as compared to patients without chronic GVHD (P=0.006 for PFS and P=0.01 for OS). Collectively, these data demonstrate that RIC allo-SCT can mediate a potentially curative graft-versus-myeloma effect with an acceptable incidence of toxicity and TRM.

Graft-versus-host disease, donor chimerism, and organ toxicity in stem cell transplantation after conditioning with fludarabine and melphalan

Hematopoietic stem cell transplantation may be used to induce a graft-versus-tumor effect against a range of malignancies. Pretransplantation conditioning regimens vary considerably in their degree of myelosuppression and immunosuppression, which may result in marked differences in the rate of T-cell engraftment and, as a consequence, the onset and severity of graft-versus-host disease (GVHD). We have examined the development of T-cell chimerism and the onset of GVHD following fludarabine and melphalan conditioning in 39 patients undergoing stem cell allografts from matched-sibling donors. Cyclosporin and short-course methotrexate were used as GVHD prophylaxis. Fatal regimen-related toxicity occurred in 4 patients. Rapid T-cell engraftment was found in all but 1 of the patients assessed, with more than 90% donor T-cell chimerism at 1 month posttransplantation. Of the evaluable patients, 43% developed grade 2-4 acute GVHD and 87% developed chronic GVHD (70% extensive). Overall, the combination of fludarabine and melphalan is intensely immunosuppressive, leads to rapid T-cell engraftment and results in substantial toxicity and GVHD, particularly in heavily pretreated patients.

Graft-versus-host disease can be separated from graft-versus-lymphoma effects by control of lymphocyte trafficking with FTY720

Graft-versus-host disease (GvHD) mediated by donor T cells recognizing host alloantigens is associated with beneficial graft-versus-tumor effects in recipients of allogeneic hematopoietic cell transplants. Since leukemias and lymphomas reside largely within the lymphohematopoietic system, we have proposed that the desired graft-versus-leukemia or graft-versus-lymphoma effect can be separated from the complication of GvHD by confinement of the graft-versus-host alloresponse to the lymphohematopoietic tissues. Since the new sphingosine-1-phosphate receptor agonist immunosuppressive drug FTY720 leads to trapping of T cells in secondary lymphoid tissues, we evaluated the possibility that this drug could diminish GvHD, a disease involving epithelial target tissues, while permitting a beneficial alloresponse to take place within the lymphohematopoietic system, leading to graft-versus-lymphoma effects. We demonstrate here that FTY720 markedly reduces GvHD in a clinically relevant, haploidentical strain combination, while permitting antitumor effects against a T cell lymphoma of unshared host MHC haplotype to proceed unhindered. These results establish a potential new immunotherapeutic approach to separating graft-versus-leukemia effects from GvHD.

Influence of tumor vaccines on graft versus tumor activity and graft versus host disease in allogeneic bone marrow transplantation

Powerful immunologically-mediated antitumor efforts can be observed in allogeneic hematopoietic stem cell transplantation. In the absence of specific immune interventions, this graft versus tumor effect is closely associated with graft versus host disease. In the work summarized here, the influence of cellular tumor vaccines on graft versus tumor activity and graft versus host disease is examined in a murine model of MHC-matched, minor histocompatibility antigen-mismatched bone marrow transplantation. The experiments have generated the following conclusions. First, complex cellular vaccines, which include recipient minor histocompatibility antigens, when administered to allogeneic donors generate powerful graft versus tumor effects but also induce unacceptable exacerbations of graft versus host disease. Second, cellular tumor vaccines, which contain recipient minor histocompatibility antigens, can be administered to transplant recipients after transplant without significant exacerbation of GVHD and with retention of clinically significant graft versus tumor effects. Third, immunization of donors with molecularly defined tumor-associated antigens, which are not recipient minor histocompatibility antigens, can be coupled with post-transplant immunization of recipients with cellular vaccines without exacerbation of GVHD.

Reducing transplant toxicity

Conventional myeloablative allogeneic hematopoietic cell transplantation produces considerable morbidity and mortality. These generally limit this treatment to patients in good medical condition who are younger than 55 years of age. T-cell-mediated graft-versus-tumor effects play a key role in the elimination of malignancy after allografting. Several investigators have sought to reduce regimen-related toxicities while optimizing graft-versus-tumor effects. Strategies can be broadly classified as (1) reduced-intensity regimens that retain some toxicity, and (2) minimally myelosuppressive regimens that rely on immunosuppression for allogeneic engraftment and resultant graft-versus-tumor effects. Although follow-up has been short, preliminary results are encouraging. Current challenges include defining a regimen that will facilitate full donor engraftment while minimizing toxicities and graft-versus-host disease. If long-term efficacy is demonstrated, such strategies will expand the options for patients who would not qualify for conventional allogeneic transplants.

Reduced intensity conditioning: enhanced graft-versus-tumor effect following dose-reduced conditioning and allogeneic transplantation for refractory lymphoid malignancies after high-dose therapy

Non-myeloablative regimens have been proven to allow engraftment following allogeneic stem cells transplantation (allo-SCT) with minimal procedure-related toxicity. Conventional allo-SCT may produce remissions in patients with relapsed and refractory lymphoid malignancies (LM) but these good results may be achieved at the cost of high treatment-related morbidity and mortality. Application of allo-SCT using less intensive regimens may temper the frequency of these complications, allowing a potent graft-versus-tumor effect (GVT). We present our data on 11 patients with LM receiving allo-SCT with a reduced regimen. Ten patients had received previous high-dose therapy, and were at high risk for toxicity, thus precluding the use of allo-SCT. A fludarabine and low-dose busulfan combination facilitated engraftment while exerting GVT. Hematological recovery was quick, and full donor T cell chimerism preceded acute GVHD. GVHD and infections were the major problems. Spontaneous acute GVHD occurred in eight patients (72%). Five patients (45%) achieved complete remission, and the GVT effect was closely associated with GVHD. These results support the concept that GVT is effective against LM in patients who have been heavily pretreated. Further studies are needed to investigate strategies to generate more specific alloreactive effects providing optimal GVT and an acceptable risk of GVHD and infections.

Mixed chimerism: preclinical studies and clinical applications

Traditional approaches to allogeneic stem cell transplantation have relied on the use of toxic high-dose conditioning therapy to achieve allogeneic engraftment and control of underlying disease. Preclinical observations have shown that, for engraftment purposes, conditioning regimens can be reduced in intensity, resulting in reduced treatment toxicities. In preclinical canine studies, the use of potent pre- and postgrafting immunosuppression allowed for reduction in conditioning regimens and development of stable mixed chimerism. If these newer approaches using attenuated conditioning regimens can be successfully applied to human transplantation, an improved safety profile will allow potentially curative treatment of patients not currently offered such therapy. Mixed chimerism per se could prove curative of disease manifestation for various nonmalignant disturbances of the hematopoietic and immune systems. For patients with malignancy, infusion of additional donor lymphocytes may be needed to effectively treat underlying disease.

Keratinocyte growth factor separates graft-versus-leukemia effects from graft-versus-host disease

The major obstacles to successful outcome after allogeneic bone marrow transplantation (BMT) for leukemia remain graft-versus-host disease (GVHD) and leukemic relapse. Improved survival after BMT therefore requires more effective GVHD prophylaxis that does not impair graft-versus-leukemia (GVL) effects. We studied the administration of human recombinant keratinocyte growth factor (KGF) in a well- characterized murine BMT model for its effects on GVHD. KGF administration from day -3 to +7 significantly reduced GVHD mortality and the severity of GVHD in the gastrointestinal (GI) tract, reducing serum lipopolysaccharide (LPS) and tumor necrosis factor (TNF)alpha levels, but preserving donor T-cell responses (cytotoxic T lymphocyte [CTL] activity, proliferation, and interleukin [IL]-2 production) to host antigens. When mice received lethal doses of P815 leukemia cells at the time of BMT, KGF treatment significantly decreased acute GVHD compared with control-treated allogeneic mice and resulted in a significantly improved leukemia-free survival (42% v 4%, P <.001). KGF administration thus offers a novel approach to the separation of GVL effects from GVHD.

Induction of a graft-versus-leukemia reaction by cyclosporin A withdrawal as immunotherapy for leukemia relapsing after allogeneic bone marrow transplantation

We studied the immunomodulating effect of withdrawal of immunosuppression with cyclosporin A (CsA) in 42 patients with leukemic relapse of chronic myelogenous leukemia (CML) (n = 24), acute myeloid leukemia (AML) (n = 13) and acute lymphoblastic leukemia (ALL) (n = 5) after allogeneic unmanipulated bone marrow (BMT) or peripheral blood stem cell transplantation (PBSCT). Response to CsA withdrawal was monitored molecularly by the polymerase chain reaction for elimination of CML cells containing the bcr-abl messenger RNA (mRNA) transcript (n = 24), or mll-af4 mRNA transcript characteristic of leukemic cells with a 11q23 chromosomal abnormality (n = 1). Rapid tapering of CsA resulted in subsequent achievement of cytogenetic remission in 11 of 14 CML patients (79%) who relapsed in early disease phase (n = 9 cytogenetic relapse, n = 2 hematological relapse) after a median of 57 days. Three of 13 AML patients and one of five ALL patients achieved complete remission. CsA withdrawal was accompanied by the development of acute graft-versus-host disease (GVHD) grade II in most of the 24 patients with CML. Two patients who achieved remission of AML or ALL died from severe GVHD grade III-IV. We calculated a probability of 84% for achieving and remaining in remission with early relapse of CML 4 years after relapse post BMT, whereas patients with AML have only a probability of about 10% of achieving and remaining in remission after 3 years. Patients with advanced CML and ALL had no chance of achieving and remaining in remission in the same time period.

A metalloproteinase inhibitor prevents acute graft-versus-host disease while preserving the graft-versus-leukaemia effect of allogeneic bone marrow transplantation

We examined the effect of a hydroxamic acid-based matrix metalloproteinase inhibitor (KB-R7785), which we previously demonstrated to have a potent ameliorating effect on acute graft-versus-host disease (GVHD), and on the graft-versus-leukaemia (GVL) effect of allogeneic bone marrow transplantation (BMT). KB-R7785 was administered to (C57BL/6 x BALB/c) F1 (CBF1) mice that had been inoculated with IgE-producing B53 hybridoma cells of BALB/c origin as a model tumour, along with or without transplantation of C57BL/6 (B6) bone marrow cells and spleen cells (BMS). Administration of KB-R7785 without BMS significantly prolonged the survival of B53-inoculated CBF1 mice by inhibiting the infiltration of B53 cells into the liver and spleen. Transplantation of B6 BMS without KB-R7785 resulted in the death of most recipients due to acute GVHD while efficiently eliminating B53 cells. Administration of KB-R7785 along with B6 BMS resulted in a 50% survival of B53-inoculated CBF1 mice over 50 d without histological manifestations of acute GVHD or residual B53 cells. These results indicate the beneficial effects of KB-R7785 that inhibit tumour infiltration and prevent acute GVHD while preserving the GVL effect of allogeneic BMT.

Antileukemic effects of rapid cyclosporin withdrawal in patients with relapsed chronic myeloid leukemia after allogeneic bone marrow transplantation

The results of rapid tapering of Cyclosporin therapy in 7 patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML) in relapse after allogeneic bone marrow transplantation are reported. All patients had cytogenetically-documented relapse within 6 months of transplant, and were on oral Cyclosporin therapy. Rapid tapering of Cyclosporin resulted in moderately severe acute GVHD in 2 cases, and in extensive chronic GVHD in a further 2 patients (fatal in 1 case). An antileukemic effect was observed in 6 patients, with complete haematological and cytogenetic remission observed in all cases. The seventh patient did not respond, and died after infusion of donor leucocytes. Four of the responders remain in complete remission of CML 30 to 120 months after BMT. One patient died in remission of chronic GVHD, and one patient had a complete response lasting 5 months, but relapsed and died 13 months post transplant. Rapid withdrawal of Cyclosporin therapy appears to be an effective means of treatment of early relapse of CML after transplant, and is an alternative to the use of donor leucocyte infusions for those patients still receiving Cyclosporin at the time of relapse.

Antagonistic effects of systemic interleukin 2 on immune Tcell-mediated graft-versus-leukemia reactivity

This study demonstrates that systemic interleukin 2 (IL-2) can decrease the homing of syngeneic immune T cells to the target organ of metastases and accelerate unwanted side effects of allogeneic immune T cells. As a tumor system, we used the well-characterized highly aggressive DBA/2 mouse leukemia ESb and its less aggressive adhesion variant, ESb-MP. Systemic IL-2 treatment was performed with recombinant human interleukin-2 (Proleukin), which was slowly released via an implanted osmotic pump or was modified with polyethylene glycol (PEG-IL-2) to achieve constant plasma levels. Allogeneic B10.D2 antitumor immune spleen cells (ISPL cells) exerted strong graft-versus-leukemia (GvL) reactivity after adoptive transfer into late-stage ESb-MP tumor-bearing DBA/2 mice. Mls(a) superantigen-reactive vbeta6 donor T cells were not eliminated or tolerized by in vivo priming with the tumor cells and were present in active proliferation in liver infiltrates. When exogenous PEG-IL-2 or Proleukin was applied in addition to ISPL cells in such mice, the strong GvL-mediated protective immunity was converted into a fatal graft-versus-host disease. IL-2 treatment alone had no toxic effect and caused a moderate protection effect in the absence of an effect on local tumor growth. Potentiation of GvH reactivity of B10.D2 ISPL by PEG-IL-2 was proven in non-tumor-bearing DBA/2 mice, in which graft-versus-host disease was characterized by: (a) heavy hepatic lymphocytic infiltration, (b) irreversible increase of serum glutamate-oxalacetate-transaminase and glutamate-pyruvate-transaminase levels, (c) weight loss, and (d) death. Antagonistic effects of systemic IL-2 on GvL were observed with syngeneic DBA/2 anti-ESb immune peritoneal effector cells (PECs). There was a detrimental effect of systemic IL-2 on liver target organ infiltration by immune T cells causing, at day 6 after transfer, a drop from 20-30 CD4 or CD8 T cells per liver lobule in the PEC group to <5 in the PEC plus IL-2 group. The results emphasize the importance of a better understanding of IL-2 function in vivo and of its interaction with immune cell function to improve protocols for optimal application in the clinic to achieve maximal GvL effects.

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.