LPS antagonism reduces graft-versus-host disease and preserves graft-versus-leukemia activity after experimental bone marrow transplantation

Acute graft-versus-host disease (GVHD) and leukemic relapse remain the two major obstacles to successful outcomes after allogeneic bone marrow transplantation (BMT). Recent studies have demonstrated that the loss of gastrointestinal tract integrity, and specifically the translocation of LPS into the systemic circulation, is critical to the induction of cytokine dysregulation that contributes to GVHD. Using a mouse BMT model, we studied the effects of direct LPS antagonism on GVHD severity and graft-versus-leukemia (GVL) activity. Administration of B975, a synthetic lipid-A analogue from day 0 to day +6, reduced serum TNF-alpha levels, decreased intestinal histopathology, and resulted in significantly improved survival and a reduction in clinical GVHD, compared with control-treated animals. Importantly, B975 had no effect on donor T cell responses to host antigens in vivo or in vitro. When mice received lethal doses of P815 tumor cells at the time of BMT, administration of B975 did not impair GVL activity and resulted in significantly improved leukemia-free survival. These findings reveal a critical role for LPS in the early inflammatory events contributing to GVHD and suggest that a new class of pharmacologic agents, LPS antagonists, may help to prevent GVHD while preserving T cell responses to host antigens and GVL activity.

Pharmacologic blockade of JAK1/JAK2 reduces GvHD and preserves the graft-versus-leukemia effect

We have recently reported that interferon gamma receptor deficient (IFNγR-/-) allogeneic donor T cells result in significantly less graft-versus-host disease (GvHD) than wild-type (WT) T cells, while maintaining an anti-leukemia or graft-versus-leukemia (GvL) effect after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We demonstrated that IFNγR signaling regulates alloreactive T cell trafficking to GvHD target organs through expression of the chemokine receptor CXCR3 in alloreactive T cells. Since IFNγR signaling is mediated via JAK1/JAK2, we tested the effect of JAK1/JAK2 inhibition on GvHD. While we demonstrated that pharmacologic blockade of JAK1/JAK2 in WT T cells using the JAK1/JAK2 inhibitor, INCB018424 (Ruxolitinib), resulted in a similar effect to IFNγR-/- T cells both in vitro (reduction of CXCR3 expression in T cells) and in vivo (mitigation of GvHD after allo-HSCT), it remains to be determined if in vivo administration of INCB018424 will result in preservation of GvL while reducing GvHD. Here, we report that INCB018424 reduces GvHD and preserves the beneficial GvL effect in two different murine MHC-mismatched allo-HSCT models and using two different murine leukemia models (lymphoid leukemia and myeloid leukemia). In addition, prolonged administration of INCB018424 further improves survival after allo-HSCT and is superior to other JAK1/JAK2 inhibitors, such as TG101348 or AZD1480. These data suggest that pharmacologic inhibition of JAK1/JAK2 might be a promising therapeutic approach to achieve the beneficial anti-leukemia effect and overcome HLA-barriers in allo-HSCT. It might also be exploited in other diseases besides GvHD, such as organ transplant rejection, chronic inflammatory diseases and autoimmune diseases.

TGF-beta in allogeneic stem cell transplantation: friend or foe?

Donor treatment with granulocyte-colony-stimulating factor (G-CSF) attenuates the ability of donor T cells to induce acute graft-versus-host disease (aGVHD) but increases the severity of chronic GVHD (cGVHD). We investigated the role of the regulatory cytokine transforming growth factor beta (TGF-beta) in this paradox in well-established murine models of aGVHD and cGVHD wherein recipients undergo transplantation with splenocytes from donors treated with G-CSF. Neutralization of TGF-beta after stem-cell transplantation (SCT) significantly increased the severity of aGVHD, and the concurrent prevention of interleukin-10 (IL-10) production further exaggerated this effect. Early after SCT, donor T cells were the predominant source of TGF-beta and were able to attenuate aGVHD in a TGF-beta-dependent fashion. Although the neutralization of TGF-beta augmented the proliferation and expansion of donor T cells after SCT, it paradoxically impaired cellular cytotoxicity to host antigens and associated graft-versus-leukemia (GVL) effects. In cGVHD, neutralization of TGF-beta from day 14 after SCT attenuated histologic abnormalities, and CD11b+ mononuclear cells infiltrating sclerodermatous skin produced 50-fold more TGF-beta than corresponding T cells. Thus, though the production of TGF-beta by donor T cells early after transplantation attenuates aGVHD and is required for optimal GVL, the production of TGF-beta late after SCT is preferentially from mononuclear cells and mediates cGVHD. These data have important implications for the timing of therapeutic TGF-beta neutralization to prevent cGVHD after allogeneic SCT.

The unexpected effect of cyclosporin A on CD56+CD16- and CD56+CD16+ natural killer cell subpopulations

Cyclosporin A (CSA) is commonly used to prevent graft-versus-host disease. The influence of CSA on T-cell function has been extensively investigated; however, the effect of CSA on natural killer (NK) cells is less understood. NK cells were cultured with IL-2 and IL-15 with and without CSA for 1 week. Compared with controls, CSA-treated cultures showed fewer CD56(+)CD16(+)KIR(+) NK cells and a reciprocal increase in CD56(+)CD16(-)KIR(-) cells. These changes were due mainly to a reduced proliferation of the CD56(dim) NK-cell subpopulation and a relative resistance of CD56(bright) NK cells to CSA. Following coculture with K562 targets, CSA-exposed NK cells differed from controls and lacked Ca(2+) oscillations, nuclear factor of activated T cells (NFAT) dephosphorylation, and NFAT nuclear translocation. NK cells cultured in CSA retained cytotoxicity against K562, Raji, and KIR ligand-expressing lymphoblastoid cells. NK cells cultured in CSA showed increases in NKp30 and reductions in NKp44 and NKG2D. Following IL-12 and IL-18 stimulation, CSA-treated NK cells showed more IFN-gamma-producing cells. Using in vitro NK-cell differentiation, progenitor cells gave rise to more CD56(+)KIR(-) NK cells in the presence of CSA than controls. Collectively, these studies show that CSA influences NK-cell function and phenotype, which may have important implications for graft-versus-leukemia effects.

IL-2 activated NK cell immunotherapy of three children after haploidentical stem cell transplantation

Natural killer (NK) cells are thought to be of benefit in HLA-mismatched hematopoietic transplantation (H-SCT). Therefore, we developed a protocol for clinical-use expansion of highly enriched and IL-2-stimulated NK cells. Purification of unstimulated leukaphereses by a two-step T cell depletion with a final CD56 enrichment procedure leads to a mean purity of 95% CD56(+)CD3- NK cells with a four- to five-log depletion of T cells. So far, three pediatric patients with multiply relapsed acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML) were treated with repeated transfusions post-H-SCT. Directed killer immunoglobulin-like receptor (KIR) mismatches were demonstrated in all three cases. Although all patients showed blast persistence at the time of transplant, they reached complete remission and complete donor chimerism within 1 month post-H-SCT. NK cell therapy was tolerated well without graft-versus-host disease (GvHD) induction or other adverse events. The AML patient died of early relapse on day +80, while the ALL patients died of thrombotic-thrombocytopenic purpura and atypical viral pneumonia on days +45 and +152, respectively. This initial trial showed the feasibility of good manufacturing practice (GMP)-compliant NK cell isolation and expansion for clinical applications. We now launch a clinical phase I trial with activated NK cells post-H-SCT.

NKT cell-dependent leukemia eradication following stem cell mobilization with potent G-CSF analogs

NKT cells have pivotal roles in immune regulation and tumor immunosurveillance. We report that the G-CSF and FMS-like tyrosine kinase 3 ligand (Flt-3L) chimeric cytokine, progenipoietin-1, markedly expands the splenic and hepatic NKT cell population and enhances functional responses to alpha-galactosylceramide. In a murine model of allogeneic stem cell transplantation, donor NKT cells promoted host DC activation and enhanced perforin-restricted CD8+ T cell cytotoxicity against host-type antigens. Following leukemic challenge, donor treatment with progenipoietin-1 significantly improved overall survival when compared with G-CSF or control, attributable to reduced graft-versus-host disease mortality and paradoxical augmentation of graft-versus-leukemia (GVL) effects. Enhanced cellular cytotoxicity was dependent on donor NKT cells, and leukemia clearance was profoundly impaired in recipients of NKT cell-deficient grafts. Enhanced cytotoxicity and GVL effects were not associated with Flt-3L signaling or effects on DCs but were reproduced by prolonged G-CSF receptor engagement with pegylated G-CSF. Thus, modified G-CSF signaling during stem cell mobilization augments NKT cell-dependent CD8+ cytotoxicity, effectively separating graft-versus-host disease and GVL and greatly expanding the potential applicability of allogeneic stem cell transplantation for the therapy of malignant disease.

Stem cell mobilization with G-CSF analogs: a rational approach to separate GVHD and GVL?

The separation of graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) remains the "holy grail" of allogeneic stem cell transplantation, and improvements are urgently needed to allow more effective therapy of malignant disease. The use of G-CSF-mobilized peripheral blood as a clinical stem cell source is associated with enhanced GVL effects without amplification of significant acute GVHD. Preclinical studies have demonstrated that G-CSF modulates donor T cell function before transplantation, promoting T(H)2 differentiation and regulatory T cell function. In addition, the expansion of immature antigen-presenting cells (APCs) and plasmacytoid dendritic cells (DCs) favors the maintenance of this pattern of T cell differentiation after transplantation. Although these patterns of T cell differentiation attenuate acute GVHD, they do not have an impact on the cytolytic pathways of the CD8(+) T cells that are critical for effective GVL. Recently, it has been demonstrated that modification of G-CSF, either by pegylation of the native cytokine or conjugation to Flt-3L, results in the expansion and activation of donor iNKT cells, which significantly augment CD8(+) T cell-mediated cytotoxicity and GVL effects after transplantation. Given that these cytokines also enhance the expansion of regulatory T cells and APCs, they further separate GVHD and GVL, offering potential clinical advantages for the transplant recipient.

Role of tumor necrosis factor-alpha in graft-versus-host disease and graft-versus-leukemia responses

Tumor necrosis factor-alpha (TNF-alpha) antagonist therapy has proven effective in inflammatory conditions such as rheumatoid arthritis and Crohn's disease. There is substantial evidence that TNF-alpha also plays a role in the development of graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation, which along with leukemia relapse remains one of the 2 major impediments to success of the approach. Using a recently developed potent rat/mouse chimeric monoclonal antibody directed against murine TNF-alpha (CNTO2213), the authors investigated the effect of TNF-alpha blockade on GVHD mediated by either CD4(+) or CD8(+) donor T cells. The results indicated that the treatment had only a moderate effect on both a CD8(+) T cell-mediated major histocompatibility complex-matched GVHD model involving multiple minor histocompatibility antigens and a p-->F(1) acute GVHD model directed against a haplo-mismatched major histocompatibility complex barrier involving both CD4(+) and CD8(+) T cells. In contrast, treatment with the anti-TNF-alpha antibody had a highly significant effect (100% survival rate) on the CD4(+) T cell-mediated component of this latter model. Importantly, anti-TNF-alpha antibody did not block the development of a graft-versus-leukemia effect against a murine myeloid leukemia challenge in either a syngeneic or allogeneic p-->F(1) setting. This suggests that the inhibition of TNF-alpha during allogeneic hematopoietic cell transplantation may be able to diminish the inflammatory GVHD reaction without hindering effective graft-versus-leukemia responses.

Donor lymphocyte infusion-mediated graft-versus-leukemia effects in mixed chimeras established with a nonmyeloablative conditioning regimen: extinction of graft-versus-leukemia effects after conversion to full donor chimerism

BACKGROUND

We investigated an approach to separating graft-versus-lymphoma (GVL) effects from graft-versus-host disease (GVHD) in mice receiving a nonmyeloablative conditioning regimen allowing establishment of mixed hematopoietic chimerism.

METHODS

We evaluated the ability of donor lymphocyte infusions (DLI) to mediate GVL effects without GVHD in mixed chimeras prepared with cyclophosphamide, anti-T-cell antibodies, and thymic irradiation. To examine the fate of GVH-reactive donor CD8+ T cells, we used the 2C T-cell receptor (TCR) transgenic mouse strain, which carries an Ld-specific transgenic TCR on the B6 background.

RESULTS

Administration of DLI on day 35 post-BMT led to conversion from mixed to full donor chimerism and mediated a powerful GVL effect with complete protection (100% survival) against mortality induced by a host-type lymphoma (EL4) administered 7 days later (100% mortality in non-DLI controls; P<0.001). No GVHD occurred in DLI recipients. Rechallenging the surviving DLI recipients, which had converted to full chimerism, with the same tumor dose 17 weeks later led to rapid tumor mortality. Long-term DLI recipients had anti-host proliferative responses, but not CTL responses in vitro. When given as DLI together with wild-type spleen cells, marked expansion of GVH-reactive 2C CD8+ T cells was observed on day 10, followed by a marked decline in their numbers by week 10 post-DLI.

CONCLUSIONS

Nonmyeloablative induction of mixed chimerism followed by administration of DLI can mediate powerful GVL effects. The late loss of DLI-mediated GVL effects may reflect the eventual loss of donor-derived GVH-reactive CTL, which occurs in association with conversion to full donor chimerism.

Targeting Sirt-1 controls GVHD by inhibiting T-cell allo-response and promoting Treg stability in mice

Graft-versus-host disease (GVHD) remains one of the major complications after allogeneic bone marrow transplantation (allo-BMT). Sirtuin-1 (Sirt-1) plays a crucial role in various biological processes including cellular senescence, metabolism, and inflammatory responses. Sirt-1 deacetylation regulates different transcription factors that are important for modulating immune responses. In the current study, we addressed the role of Sirt-1 in GVHD induction by employing Sirt-1 conditional knockout mice as well as a pharmacological Sirt-1 inhibitor. Using major histocompatibility complex (MHC)-mismatched and MHC-matched murine BMT models, we found that Sirt-1-/- T cells had a reduced ability to induce acute GVHD (aGVHD) via enhanced p53 acetylation. Sirt-1-deficient T cells also promoted induced regulatory T cell (iTreg) differentiation and inhibited interferon-γ production after allo-BMT. Sirt-1 deletion in iTregs increased Foxp3 stability and restrained iTreg conversion into pathogenic T cells. Furthermore, we found that administration with a Sirt-1 inhibitor, Ex-527, significantly improved recipient survival and clinical scores, with no signs of tumor relapse. These results indicate that Sirt-1 inhibition can attenuate GVHD while preserving the graft-versus-leukemia effect. Consistently, Sirt-1-deficient T cells also displayed a remarkably reduced ability to induce chronic GVHD (cGVHD). Mechanistic studies revealed that Sirt-1 deficiency in T cells enhanced splenic B-cell reconstitution and reduced follicular T helper cell development. Sirt-1 deficiency in T cells modulated donor B-cell responses reducing both B-cell activation and plasma cell differentiation. In addition, therapeutic Sirt-1 inhibition could both prevent cGVHD and reduce established cGVHD. In conclusion, Sirt-1 is a promising therapeutic target for the control of aGVHD and cGVHD pathogenesis and possesses high potential for clinical application.

Pretreatment of donors with interleukin-18 attenuates acute graft-versus-host disease via STAT6 and preserves graft-versus-leukemia effects

Interleukin-18 (IL-18) is a unique cytokine that modulates both T(H)1/T(H)2 responses, but its ability to modulate diseases through induction of T(H)2 cytokines is unclear. It has been shown to play an important role in allogeneic bone marrow transplantation (BMT). Because immune responses of allogeneic BM donors may affect acute graft-versus-host disease (GVHD), we investigated the effect of pretreating BM transplant donors with IL-18 on the severity of acute GVHD using a well-characterized experimental BMT model (BALB/c-->B6). Pretreatment of allogeneic BM transplant donors with IL-18 significantly improved survival (80% vs 0%; P <.001), and reduced clinical, biochemical, and pathologic indices of acute GVHD in BM transplant recipients. IL-18 pretreatment was associated with reduced interferon gamma (IFN-gamma) and greater IL-4 secretion by donor T cells after BMT. Acute GVHD mortality was reduced when IL-18 was administered to donors deficient in IFN-gamma and signal transducer and activator of transcription 4 (STAT4) but not STAT6 signaling molecules, suggesting a critical role for STAT6 signaling in IL-18's protective effect. IL-18 treatment did not alter donor CD8(+) cytotoxic T-lymphocyte (CTL) activity and preserved graft-versus-leukemia (GVL) effects after allogeneic BMT (70% vs 10%; P <.01). Together these data illustrate that pretreatment of donors with IL-18 prior to allogeneic BMT attenuates acute GVHD in a STAT6-dependent mechanism while preserving GVL effects.

Risk assessment in haematopoietic stem cell transplantation: GvHD prevention and treatment

Graft-versus-host disease (GvHD) is the major cause of transplant-related mortality and morbidity. As it is closely related to the major therapeutic principle, graft-versus-leukaemia (GvL) effect, risk assessment has to balance both risks depending on the pre-transplant status. This is clearly demonstrated when comparing the two major strategies for prevention of GvHD. While the majority of approaches aiming at T-cell depletion show efficacy in reducing acute and chronic GvHD and transplant-related mortality, T-cell depletion also affects graft-versus-leukaemia effects and thus results in a higher relapse rate. Thus, standard prophylaxis relying on calcineurin inhibitors frequently results in at least equivalent or even superior long-term disease-free survival, and the risk of relapse has to be considered when selecting regimens for prevention of GvHD. In addition to this general dilemma, drug-specific side-effects and risks have to be considered when selecting regimens for GvHD prevention and treatment.

Graft-versus-host disease is enhanced by selective CD73 blockade in mice

CD73 functions as an ecto-5'-nucleotidase to produce extracellular adenosine that has anti-inflammatory and immunosuppressive activity. We here demonstrate that CD73 helps control graft-versus-host disease (GVHD) in mouse models. Survival of wild-type (WT) recipients of either allogeneic donor naïve CD73 knock-out (KO) or WT T cells was similar suggesting that donor naïve T cell CD73 did not contribute to GVHD. By contrast, donor CD73 KO CD4(+)CD25(+) regulatory T cells (Treg) had significantly impaired ability to mitigate GVHD mortality compared to WT Treg, suggesting that CD73 on Treg is critical for GVHD protection. However, compared to donor CD73, recipient CD73 is more effective in limiting GVHD. Pharmacological blockade of A2A receptor exacerbated GVHD in WT recipients, but not in CD73 KO recipients, suggesting that A2 receptor signaling is primarily implicated in CD73-mediated GVHD protection. Moreover, pharmacological blockade of CD73 enzymatic activity induced stronger alloreactive T cell activity, worsened GVHD and enhanced the graft-versus-leukemia (GVL) effect. These findings suggest that both donor and recipient CD73 protects against GVHD but also limits GVL effects. Thus, either enhancing or blocking CD73 activity has great potential clinical application in allogeneic bone marrow transplants.

Molecular remission of chronic myeloid leukaemia following a non-myeloablative allogeneic peripheral blood stem cell transplant: in vivo and in vitro evidence for a graft-versus-leukaemia effect

Two patients with chronic myeloid leukaemia (CML) received a non-myeloablative preparative regimen of cyclophosphamide and fludarabine, followed by an unmanipulated, G-CSF-mobilized, peripheral blood stem cell transplant from an HLA-identical sibling. Chimaerism, evaluated in myeloid and T-lymphoid lineages by PCR of minisatellite variable regions, showed day 14 post-transplant haemopoietic recovery to be 90% autologous in both patients. On day 30 the bone marrow showed only 1/20 and 2/18 donor metaphases. By day 100 post transplant both had 100% donor myeloid and lymphoid lineages as assessed by karyotype and minisatellite chimaerism analysis. They subsequently became RT-PCR negative for BCR-ABL. Both survive 7 and 14 months post transplant in molecular remission of CML. In one, donor T cells, stimulated with pre-transplant CML cells, induced 30-50% inhibition of pre-transplant leukaemic CFU-GM, but did not inhibit CFU-GM in the day 60 marrow (46% Ph-negative recipient, 54% donor). These results show that a non-myeloablative allotransplant can induce molecular remissions of CML through a graft-versus-leukaemia effect.

Janus kinase 3 inhibitor WHI-P131/JANEX-1 prevents graft-versus-host disease but spares the graft-versus-leukemia function of the bone marrow allografts in a murine bone marrow transplantation model

The purpose of the present study was to evaluate the effects of graft-versus-host disease (GVHD) prophylaxis with the Janus kinase 3 (JAK3) inhibitor WHI-P131/JANEX-1 on the graft-versus-leukemic (GVL) function of marrow allografts in mice undergoing bone marrow transplantation (BMT) after being challenged with an otherwise invariably fatal dose of BCL-1 leukemia cells. GVHD prophylaxis using WHI-P131 markedly improved the survival outcome after BMT. The probability of survival at 30 days after BMT was 11% +/- 6% for vehicle-treated recipients (median survival time, 25 days) versus 63% +/- 12% for recipients treated with WHI-P131 (median survival time, 36 days; P <.0001). Because WHI-P131 is devoid of antileukemic activity against BCL-1 leukemia cells, this marked improvement in survival outcome was due to reduced incidence of GVHD-associated fatalities combined with sustained GVL function of the allografts in the WHI-P131 group. Notably, adoptive transfer experiments demonstrated that the spleens of WHI-P131-treated allograft recipients contained less than 0.001% BCL-1 cells. Notably, GVHD prophylaxis with WHI-P131 plus methotrexate resulted in 100% survival of mice receiving allotransplants challenged with an otherwise invariably fatal dose of BCL-1 leukemia. Taken together, our results provide strong experimental evidence that GVHD prophylaxis using WHI-P131 does not impair the GVL function of the allografts and consequently contributes to an improved post-BMT survival outcome of the recipient mice.

Hepatocyte growth factor preserves graft-versus-leukemia effect and T-cell reconstitution after marrow transplantation

Graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation (BMT). When GVHD is controlled by T-cell–depleted grafts or immunosuppressants, BM transplant recipients often suffer from an increased rate of leukemic relapse and impaired reconstitution of immunity. Using a mouse BMT model, we investigated the effects of hepatocyte growth factor (HGF) gene transfection on the severity of GVHD, the graft-versus-leukemia effect, and the reconstitution of T cells after BMT. After HGF gene transfer, acute GVHD was reduced, while mature donor T-cell responses to host antigens were preserved, resulting in a significant improvement of leukemia-free survival. HGF gene transfer promoted regeneration of bone marrow–derived T cells and the responsiveness of these cells to alloantigens. Furthermore, HGF preserved the thymocyte phenotype and thymic stromal architecture in mice with GVHD. This suggested that HGF exerts a potent protective effect on the thymus, which in turn promotes reconstitution of bone marrow–derived T cells after allogeneic BMT. These results indicate that HGF gene transfection can reduce acute GVHD preserving the graftversus-leukemia effect, while promoting thymic-dependent T-cell reconstitution after allogeneic BMT.

The graft-versus-leukemia effect of nonmyeloablative stem cell allografts may not be sufficient to cure chronic myelogenous leukemia

We treated 12 patients with chronic myelogenous leukemia (CML) with a low-intensity preparative regimen followed by allogeneic stem cell transplantation in an attempt to confer a curative graft-versus-leukemia (GVL) effect with minimum morbidity. Seven patients in first chronic phase (CP1) and five in second chronic phase (CP2) (age 15-68 years) received a nonmyeloablative conditioning regimen of fludarabine and cyclophosphamide, followed by a G-CSF-mobilized peripheral blood stem cell (PBSC) transplant from an HLA-identical sibling. Cyclosporine (CsA) was used for graft-versus-host disease (GVHD) prophylaxis. Median follow-up was 384 days. Neutrophil recovery occurred at a median of 12 days. There was no transplant-related mortality. Of the seven CP1 patients transplanted, seven achieved a stable molecular remission; two with no post-transplant intervention, three after donor lymphocytes, imatinib and interferon, and two after a myeloablative stem cell transplant. Four of five CP2 patients died in blast crisis and one survived in molecular remission. Of the 12 patients with durable engraftment, six had Grades II-IV acute GVHD; six had limited chronic GVHD. These results suggest that cytoreduction is required to optimize the curative effect of allogeneic stem cell transplantation for CML.

Ex vivo fludarabine exposure inhibits graft-versus-host activity of allogeneic T cells while preserving graft-versus-leukemia effects

Allogeneic donor T cells in bone marrow transplantation (BMT) can contribute to beneficial graft-versus-leukemia (GVL) effects but can also cause detrimental graft-versus-host disease (GVHD). A successful method for the ex vivo treatment of donor T cells to limit their GVHD potential while retaining GVL activity would have broad clinical applications for patients undergoing allogeneic hematopoietic cell transplantation for malignant diseases. We hypothesized that donor lymphocyte infusions treated with fludarabine, an immunosuppressive nucleoside analog, would have reduced GVHD potential in a fully major histocompatibility complex-mismatched C57BL/6 --> B10.BR mouse BMT model. Recipients of fludarabine-treated donor lymphocyte infusions (F-DLI) had significantly reduced GVHD mortality, reduced histopathologic evidence of GVHD, and lower inflammatory serum cytokine levels than recipients of untreated DLI. Combined comparisons of GVHD incidence and donor-derived hematopoietic chimerism indicated that F-DLI had a therapeutic index superior to that of untreated DLI. Furthermore, adoptive immunotherapy of lymphoblastic lymphoma using F-DLI in the C57BL/6 --> B10.BR model demonstrated a broad therapeutic index with markedly reduced GVHD activity and preservation of GVL activity compared with untreated allogeneic T cells. Fludarabine exposure markedly reduced the CD4+CD44(low)-naive donor T-cell population within 48 hours of transplantation and altered the relative representation of cytokine-producing CD4+ T cells, consistent with T-helper type 2 polarization. However, proliferation of fludarabine-treated T cells in allogeneic recipient spleens was equivalent to that of untreated T cells. The results suggest that fludarabine reduces the GVHD potential of donor lymphocytes through effects on a CD4+CD44(low) T-cell population, with less effect on alloreactive T cells and CD4+CD44(high) memory T cells that are able to mediate GVL effects. Thus, F-DLI represents a novel method of immune modulation that may be useful to enhance immune reconstitution among allograft recipients with reduced risk of GVHD while retaining beneficial GVL effects.

Invariant natural killer T cell-natural killer cell interactions dictate transplantation outcome after alpha-galactosylceramide administration

Invariant natural killer T cells (iNKT cells) have pivotal roles in graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effects. iNKT cells are activated through their T-cell receptors by glycolipid moieties (typically the alpha-galactosylceramide [alpha-GalCer] derivative KRN7000) presented within CD1d. We investigated the ability of modified alpha-GalCer molecules to differentially modulate alloreactivity and GVL. KRN7000 and the N-acyl variant, C20:2, were administered in multiple well-established murine models of allogeneic stem cell transplantation. The highly potent and specific activation of all type I NKT cells with C20:2 failed to exacerbate and in most settings inhibited GVHD late after transplantation, whereas effects on GVL were variable. In contrast, the administration of KRN7000 induced hyperacute GVHD and early mortality in all models tested. Administration of KRN7000, but not C20:2, was found to result in downstream interleukin (IL)-12 and dendritic cell (DC)-dependent natural killer (NK)- and conventional T-cell activation. Specific depletion of host DCs, IL-12, or donor NK cells prevented this pathogenic response and the induction of hyperacute GVHD. These data demonstrate the ability of profound iNKT activation to modulate both the innate and adaptive immune response via the DC-NK-cell interaction and raise concern for the use of alpha-GalCer therapeutically to modulate GVHD and GVL effects.

The Impact of Chimerism Patterns and Predonor Leukocyte Infusion Lymphopenia on Survival following T Cell-Depleted Reduced Intensity Conditioned Transplants

Donor leukocyte infusions (DLI) are frequently required following reduced intensity conditioned (RIC) allografts to convert mixed chimerism (MC) to full donor chimerism (FDC). The rationale is to break tolerance and maximize the graft-versus-leukemia responses. We analyzed the impact of chimerism in 125 recipients of RIC (Alemtuzumab containing) transplants. Four patterns of chimerism were seen: (1) always 100% donor chimerism (54%), (2) persisting MC (22%), (3) MC with subsequent development of FDC (18%), (4) lost donor chimerism (6%). Forty-five (36%) patients received DLI. Chimerism patterns and pre-DLI lymphocyte counts (pDLI[Ly]) were significantly associated with DLI responsiveness. Complete disease responses were seen in 6 of 17 (35%) group A patients, 9 of 10 (90%) group C patients, and 0 of 6 group B patients (P = .027), supporting reports that chimerism response is a surrogate marker for disease response. In those with MC, pDLI(Ly) were significantly lower in DLI responsive than nonresponsive patients (P = .044). At 2 years, group C patients had a significant survival advantage (P = .009) compared to all other groups. In conclusion, the chimerism pattern was the best indicator of improved survival in this cohort (ie, MC later converting to FDC). In those with MC, response to DLI therapy was associated with a low lymphocyte count pre-DLI.

Elimination of alloreactive T cells using photodynamic therapy

GvHD, the most important cause of morbidity and mortality after allogeneic stem cell transplantation, depends primarily on the ability of a donor T-cell subset to react to immunogenic host Ag. Recently developed culture conditions and treatment strategies may bring us closer to the selective elimination of such alloreactive T cells, often considered the holy grail of transplantation. Among the various therapeutic modalities, photodynamic therapy (PDT) offers a biological and global approach to the eradication of unwanted allo-activated T cells by combining mitochondrial targeting, P-glycoprotein inhibition and reactive oxygen species production. Indeed, the high potency of PDT against malignant cells has been harnessed to exert selective and extensive elimination of alloreactive T-cell subsets mediating GvHD, while preserving resting T cells with the ability to reconstitute the immune system for GvL activity and prevent or suppress viruses and fungi. The present paper reviews the basis of the PDT strategy, and the methodology employed. In vitro and in vivo studies that formed the proof of principle as a basis for human studies to investigate the clinical potential of PDT in the context of GvHD will be presented together with insights into future clinical applications of this versatile treatment platform.

Interleukin 18 preserves a perforin-dependent graft-versus-leukemia effect after allogeneic bone marrow transplantation

We have recently shown that early administration of interleukin 18 (IL-18) after bone marrow transplantation (BMT) attenuates acute graft-versus-host disease (GVHD) in a lethally irradiated parent into F1 (B6-->B6D2F1) BMT model. In this study, we investigated whether IL-18 can maintain graft-versus-leukemia (GVL) effect in this context. B6D2F1 mice received transplants of T-cell-depleted (TCD) bone marrow (BM) and splenic T cells from either syngeneic (H2(b/d)) or allogeneic B6 (H2(b)) donors. Recipient mice were treated with recombinant murine IL-18 or the control diluent. Initial studies demonstrated that IL-18 treatment did not affect the proliferative responses or the cytolytic effector functions of T cells after BMT. In subsequent experiments, animals also received host-type P815 mastocytoma cells at the time of BMT. All syngeneic BM transplant recipients died from leukemia by day 18. The allogeneic BM transplant recipients effectively rejected their leukemia regardless of treatment and IL-18 significantly reduced GVHD-related mortality. Examination of the cytotoxic mechanisms with perforin-deficient donor T cells demonstrated that perforin is critical for the GVL effect. Taken together these data demonstrate that IL-18 can attenuate acute GVHD without impairing the in vitro cytolytic function or the in vivo GVL activity after allogeneic BMT.

Chemotherapy and granulocyte colony stimulating factor-mobilized blood cell infusion followed by interferon-alpha for relapsed malignancy after allogeneic bone marrow transplantation

BACKGROUND

Interferon-alpha (IFN) is known to promote graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (allo BMT). This property may also be used to enhance a graft-versus-leukaemia effect (GVL) after donor leucocyte infusion (DLI), a mode of therapy increasingly offered to patients relapsing after allo BMT.

AIM

The aims of the present study were to examine the efficacy and toxicity of IFN therapy administered after granulocyte colony-stimulating factor (G-CSF)-stimulated blood cells given as DLI in patients with acute myeloid leukaemia (AML), chronic myeloid leukaemia (CML), acute lymphoblastic leukaemia (ALL), acute undifferentiated leukaemia (AUL) and multiple myeloma relapsing after allo BMT.

METHODS

Between October 1996 and September 1999, 27 patients (16 AML, four ALL, three CML, three multiple myeloma, one AUL) who relapsed after allo BMT were treated with chemotherapy followed by DLI, collected after G-CSF stimulation in all but two cases. Subsequently, IFN was given to patients without significant GVHD or rapidly progressive disease. The outcome after DLI with regard to remission rate, disease-free survival and GVHD was analysed.

RESULTS

Eighteen patients received IFN following DLI, 14 of whom developed significant GVHD (grade II-IV acute or extensive chronic); thereafter, GVHD resolved with cessation of IFN alone in four patients, but 10 required systemic immunosuppression. Twenty-three patients were given chemotherapy and DLI as initial treatment of relapse; 10 achieved complete remission (CR), in four patients this was only after the onset of GVHD. The other four patients received chemotherapy and DLI as a consolidation of a chemotherapy-induced remission. The CR was durable only in patients with CML (3 of 3) and AML (4 of 8).

CONCLUSIONS

Treatment with IFN induced GVHD in the majority of patients receiving DLI. The induction of GVHD and GVL by this approach produced excellent results in patients with CML and modest results in AML, but appeared to be less effective in myeloma and ALL.

Unrelated bone marrow transplantation for high-risk anaplastic large cell lymphoma in pediatric patients: a single center case series

OBJECTIVES

The use of allogeneic stem cell transplantation in NHL patients is not yet clearly defined, especially in children and adolescents, but this option offers the advantages of a tumor-free graft and the possible induction of a graft-vs.-tumor effect.

PATIENTS AND METHODS

We report the results of four consecutive pediatric patients affected by anaplastic large cell lymphoma (ALCL) and treated with allogeneic stem cell transplantation from an unrelated donor. The conditioning regimen was based on total body irradiation given in association with etoposide in three patients, and with thiotepa and cyclophoshamide in one patient. Graft-vs.-host disease (GVHD) prophylaxis consisted of cyclosporin, a short course of methotrexate and rabbit antithymocyte globulin.

RESULTS

All patients had rapid engraftment within 3-4 wk for neutrophils and platelets, and achieved a stable full donor chimerism that has been maintained to the last follow-up visit. One patient later developed a restrictive pneumonopathy. This patient had been heavily pretreated during the course of the disease having suffered four relapses and had received a cumulative dose of bleomycin of 160 mg/m(2). After a follow-up of 11-42 months, all patients are alive in complete hematological and molecular remission; and three of them without any chronic GVHD.

CONCLUSIONS

The increasing number of volunteer bone marrow donors and the reduced toxicity of unrelated stem cell transplantation, especially in children, make this therapeutic option worth more extensive investigation in the treatment of high-risk failure ALCL, although more data is needed to evaluate the long-term benefits. In this regard, the presence of factors predictive of worst outcome such as an early relapse (within 12 months from diagnosis), a refractory or relapsing ALCL and the persistent detection on blood or bone marrow of nucleophosmin-anaplastic lymphoma kinase protein (NPM-ALK) transcript may help select the patients eligible to allogeneic related or unrelated stem cell transplantation.

Differential graft-versus-leukaemia effect by CD28 and CD40 co-stimulatory blockade after graft-versus-host disease prophylaxis

Co-stimulatory blockade may be a promising strategy for tolerance induction in transplantation. In allogeneic bone marrow transplantation (BMT) for leukaemia treatment, however, preservation of the graft-versus-leukaemia (GVL) effect is another critical requirement for clinical application. In this study, we have compared the effect on GVL of using CD28 and CD40 co-stimulatory blockades as graft-versus-host disease (GVHD) prophylaxis in a murine allogeneic BMT model with simultaneous transfer of BCL1 leukaemia. Despite the relative improvement of GVHD as assessed by survival and body weight in both treatment regimes, treatment with anti-CD154 moAb clearly diminished the GVL effect, whereas treatment with anti-CD80 and CD86 MoAbs maintained this effect. Although T cell-mediated effector function at 14 days post-BMT assessed by IFNgamma expression and cytotoxicity against host alloantigen was comparable between both co-stimulatory blockades, IL-12 mRNA expression was preferentially reduced by CD40 blockade. Our results suggest the differential involvement of the CD28 and CD40 co-stimulatory pathways in the development of GVHD and GVL effects. CD28 blockade may be a favourable strategy for tolerance induction in leukaemia patients undergoing BMT.