Extracorporeal photopheresis in chronic graft-versus-host disease

Despite significant advances in stem cell manipulation and post-transplant immunosuppression, chronic graft-versus-host disease (cGVHD) remains a cause of major long-term morbidity in survivors of allogeneic stem cell transplantation. Extracorporeal photopheresis (ECP) is a novel therapeutic intervention which has demonstrated efficacy in patients with refractory acute and chronic GVHD. Clinical responses have been reported in skin and visceral GVHD. While the long-term immunomodulatory effects of ECP in cGVHD are unknown, recent studies of patients undergoing a 6- to 12-month course of ECP treatment demonstrated an attenuation of Th1-mediated cytokine secretion by activated T-helper cells, a shift in the DC1/DC2 ratio favoring plasmacytoid rather than monocytoid dendritic cell profiles, and a decrease in antigen responsiveness by dendritic cells. The implications of these immunomodulatory effects of ECP on pathogenesis and clinical outcome remains a fertile area for future research.     

Extracorporeal photopheresis normalizes some lymphocyte subsets (including T regulatory cells) in chronic graft-versus-host-disease

Extracorporeal photopheresis (ECP) has been demonstrated to be clinically effective for the treatment of steroid-refractory graft-versus-host-disease (GvHD). Recently, a murine model suggested that ECP may modulate the allo-reactivity, seen in GvHD, by enhancement of T regulatory cells. T regulatory cells are an important component of immune tolerance and reduced levels of them have been observed in chronic GvHD. Samples were taken from eight chronic GvHD patients prior to receiving any ECP therapy and after three months of ECP. Samples were also obtained from eight age- and sex-matched normal controls. Each sample was evaluated for absolute levels of total lymphocytes and CD4(+) and CD8(+) T cells. T regulatory cell numbers were also assessed accordingly: CD4(+)CD25(high), CD4(+)CD25(high)CD69(-), CD4(+)CD25(high)CD152(+) and CD4(+)CD25(high)FOXP3(+). Following three months of ECP, increases in the absolute counts of total lymphocytes, CD4(+) and CD8(+) T cells and T regulatory cells were observed; however, no selective statistical increase in the percentage of T regulatory cell numbers was observed within the CD4(+) T cell compartment. ECP induces an increase in T regulatory cell numbers; however, this is not specific as there is also an enhancement of both total lymphocyte and CD4(+) T cell numbers. The positive effect of ECP may therefore depend on a more generic re-adjustment of immune homeostasis.     

Extracorporeal photopheresis induces apoptosis in the lymphocytes of cutaneous T-cell lymphoma and graft-versus-host disease patients

Extracorporeal photopheresis (ECP) is used in the treatment of T-cell-mediated disorders. However, the mechanism by which ECP achieves its effect remains illusive. Over recent years the ability of ECP to induce apoptosis has been demonstrated by cell culture experiments and retrospective histological analysis. We investigated if apoptosis could be determined in samples tested ex vivo from the UVAR:ECP system. Lymphocytes from 11 patients (six with cutaneous T-cell lymphoma, four with graft-versus-host disease, and one with scleredema) were isolated at three stages of the ECP process: immediately before ECP treatment, from the first buffy coat collected, and post UV irradiation, prior to re-infusion. Using flow cytometry each stage was tested for the early apoptotic markers; Annexin V, ApoptestTM and Carboxy-SNARF-1-AM. Comparisons of the pre-ECP and pre-infusion samples demonstrated a significant increase in apoptotic lymphocytes for all three flow cytometric techniques (P < 0.01). Increases between the pre-ECP and first buffy coat, used as a measure of the extracorporeal manipulation, were much lower. These results demonstrate that ECP directly induces significant levels of apoptosis in lymphocytes of CTCL, GvHD and scleredema patients. The apoptosis of these lymphocytes may contribute to the ECP effect.     

Extracorporeal photopheresis (ECP) in the treatment of chronic graft-versus-host disease (GVHD)

The aim of our study was to assess the efficacy of extracorporeal photopheresis (ECP) in chronic graft-versus-host disease (GVHD). Eleven patients with chronic cutaneous GVHD were studied. Four had mucosal involvement and five had pulmonary involvement. All had failed to improve on first- and second-line therapy. Three patients received ECP alone; the remainder continued to receive steroids and/or immunosuppressive therapy. Patients received ECP twice monthly for 4 months and then once monthly for 3 months. They were evaluated by serial skin scores, mucosal and skin photography, pulmonary function tests, biochemical and haematological parameters. Nine patients showed objective evidence of cutaneous improvement with a mean reduction in skin score of 48% overall. In the 10th patient, skin scores and oral involvement improved on twice monthly ECP but deteriorated when reduced to once monthly. The final patient died from renal failure secondary to cyclosporin toxicity. Two out of five patients with lung involvement showed a mild improvement in pulmonary function tests. Liver function tests were abnormal in five patients; they improved in one and deteriorated in three. All patients receiving concomitant immunosuppressive/steroid therapy were able to reduce drug dosages by trial completion. Our results indicate that ECP can benefit patients with cutaneous and mucosal chronic GVHD who have failed on first- and second-line therapies. The effect on the systemic manifestations of GVHD is less consistent.     

Extracorporeal photopheresis as second-line treatment for acute graft-versus-host disease: impact on six-month freedom from treatment failure

Second-line therapy for corticosteroid-refractory or -dependent acute graft-versus-host disease remains ill-defined, due to limited efficacy of drugs and evolving clinical trial endpoints. Six-month freedom from treatment failure has been proposed as a novel clinical trial endpoint and is defined by the absence of death, malignancy relapse/progression, or addition of a next line of systemic immunosuppressive therapy within 6 months of intervention and prior to diagnosis of chronic graft-versus-host disease. We analyzed the 6-month freedom from treatment failure endpoint in 128 patients enrolled from three centers who were treated with extracorporeal photopheresis as second-line therapy for acute graft-versus-host disease. The incidence of 6-month freedom from treatment failure was 77.3% with a 2-year survival rate of 56%. Corticosteroid dose or response status at onset of second-line therapy did not influence outcome. Higher grade of acute graft-versus-host disease (grade 2 versus grades 3–4) at onset of photopheresis predicted for poor outcome as measured by survival (hazard ratio 2.78, P<0.001), non-relapse mortality (hazard ratio 2.78, P=0.001) and 6-month freedom from treatment failure (hazard ratio 3.05, P<0.001). For the 91 patients who achieved 6-month freedom from treatment failure, 1-year, 2-year and 3-year survival rates were 78.9%, 70.8% and 69.5%, respectively. Six-month freedom from treatment failure is a reasonable early surrogate for outcome and should be considered as a clinical trial endpoint. This study demonstrates the durable effect of photopheresis as second-line therapy for corticosteroid-refractory or -dependent acute graft-versus-host disease using 6-month freedom from treatment failure as the primary endpoint.     

Critical role of host gammadelta T cells in experimental acute graft-versus-host disease

Gammadelta T cells localize to target tissues of graft-versus-host disease (GVHD) and therefore we investigated the role of host gammadelta T cells in the pathogenesis of acute GVHD in several well-characterized allogeneic bone marrow transplantation (BMT) models. Depletion of host gammadelta T cells in wild-type (wt) B6 recipients by administration of anti-T-cell receptor (TCR) gammadelta monoclonal antibody reduced GVHD, and gammadelta T-cell-deficient (gammadelta-/-) BM transplant recipients experienced markedly improved survival compared with normal controls (63% vs 10%, P < .001). gammadelta T cells were responsible for this difference because reconstitution of gammadelta-/- recipients with gammadelta T cells restored GVHD mortality. gammadelta-/- recipients showed decreased serum levels of tumor necrosis factor alpha (TNF-alpha), less GVHD histopathologic damage, and reduced donor T-cell expansion. Mechanistic analysis of this phenomenon demonstrated that dendritic cells (DCs) from gammadelta-/- recipients exhibited less allostimulatory capacity compared to wt DCs after irradiation. Normal DCs derived from BM caused greater allogeneic T-cell proliferation when cocultured with gammadelta T cells than DCs cocultured with medium alone. This enhancement did not depend on interferon gamma (IFN-gamma), TNF-alpha, or CD40 ligand but did depend on cell-to-cell contact. These data demonstrated that the host gammadelta T cells exacerbate GVHD by enhancing the allostimulatory capacity of host antigen-presenting cells.     

Regulatory dendritic cells protect against cutaneous chronic graft-versus-host disease mediated through CD4+CD25+Foxp3+ regulatory T cells

Chronic graft-versus-host disease (cGVHD) is a common cause of morbidity and mortality in allogeneic bone marrow transplantation (alloBMT). However, effective strategies for the treatment of cGVHD have not been established. In this study, we examined the therapeutic utility of modified dendritic cells (DCs) with a greater capacity to regulate immune responses than previously known tolerogenic DCs, regulatory DCs (DC(regs)), in the major histocompatibility complex-compatible, and multiple minor histocompatibility antigen-incompatible model of cGVHD in alloBMT. Treatment of the recipient mice after alloBMT with the recipient-type DC(regs) led to greater suppression of the incidence and severity of cutaneous cGVHD than rapamycin, whereas treatment with the recipient-type mature DCs promoted the pathogenesis. Analysis of the recipient mice suggested that the protective effect of the recipient-type DC(regs) involved the peripheral generation of alloreactive CD4(+)CD25(+)Foxp3(+)regulatory T (T(R)) cells from donor-derived CD4(+)CD25(-)Foxp3(-) T cells. Thus, immunotherapy with DC(regs) is a promising strategy for the treatment of cGVHD in alloBMT mediated through the induction of a dominant tolerance involving CD4(+)CD25(+)Foxp3(+) T(R) cells.     

Donor-derived thymic-dependent T cells cause chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) is the most common cause of poor long-term outcomes after allogeneic bone marrow transplantation (BMT), but the pathophysiology of chronic GVHD still remains poorly understood. We tested the hypothesis that the impaired thymic negative selection of the recipients will permit the emergence of pathogenic T cells that cause chronic GVHD. Lethally irradiated C3H/HeN (H-2k) recipients were reconstituted with T-cell-depleted bone marrow cells from major histocompatibility complex [MHC] class II-deficient (H2-Ab1-/-) B6 (H-2b) mice. These mice developed diseases that showed all of the clinical and histopathological features of human chronic GVHD. Thymectomy prevented chronic GVHD, thus confirming the causal association of the thymus. CD4+ T cells isolated from chronic GVHD mice were primarily donor reactive, and adoptive transfer of CD4+ T cells generated in these mice caused chronic GVHD in C3H/HeN mice in the presence of B6-derived antigen-presenting cells. Our results demonstrate for the first time that T cells that escape from negative thymic selection could cause chronic GVHD after allogeneic BMT. These results also suggest that self-reactivity of donor T cells plays a role in this chronic GVHD, and improvement in the thymic function may have a potential to decrease chronic GVHD.     

Characterization of in vitro antimurine thymocyte globulin-induced regulatory T cells that inhibit graft-versus-host disease in vivo

Antithymocyte/antilymphocyte globulins are polyclonal antihuman T-cell antibodies used clinically to treat acute transplant rejection. These reagents deplete T cells, but a rabbit antihuman thymocyte globulin has also been shown to induce regulatory T cells in vitro. To examine whether antithymocyte globulin-induced regulatory cells might be functional in vivo, we generated a corresponding rabbit antimurine thymocyte globulin (mATG) and tested its ability to induce regulatory cells in vitro and whether those cells can inhibit acute graft-versus-host disease (GVHD) in vivo upon adoptive transfer. In vitro, mATG induces a population of CD4(+)CD25(+) T cells that express several cell surface molecules representative of regulatory T cells. These cells do not express Foxp3 at either the protein or mRNA level, but do show suppressive function both in vitro and in vivo when adoptively transferred into a model of GVHD. These results demonstrate that in a murine system, antithymocyte globulin induces cells with suppressive activity that also function in vivo to protect against acute GVHD. Thus, in both murine and human systems, antithymocyte globulins not only deplete T cells, but also appear to generate regulatory cells. The in vitro generation of regulatory cells by anti-thymocyte globulins could provide ad-ditional therapeutic modalities for immune-mediated disease.     

In vivo-activated CD103+CD4+ regulatory T cells ameliorate ongoing chronic graft-versus-host disease

CD103 (alphaEbeta7) has been shown to be an excellent marker for identifying in vivo-activated FoxP3(+)CD4(+) regulatory T (Treg) cells. It is unknown whether reinfusion of in vivo-activated donor-type CD103(+) Treg cells from recipient can ameliorate ongoing chronic graft-versus-host disease (GVHD). Here, we showed that, in a chronic GVHD model of DBA/2 (H-2(d)) donor to BALB/c (H-2(d)) recipient, donor-type CD103(+) Treg cells from recipients were much more potent than CD25(hi) natural Treg cells from donors in reversing clinical signs of GVHD and tissue damage. Furthermore, in contrast to CD25(hi) natural Treg cells, CD103(+) Treg cells expressed high levels of CCR5 but low levels of CD62L and directly migrated to GVHD target tissues. In addition, the CD103(+) Treg cells strongly suppressed donor CD4(+) T-cell proliferation; they also induced apoptosis of in vivo-activated CD4(+) T and B cells and significantly reduced pathogenic T and B cells in GVHD target tissues. These results indicate that CD103(+) Treg cells from chronic GVHD recipients are functional, and reinfusion of the CD103(+) Treg cells can shift the balance between Treg cells and pathogenic T cells in chronic GVHD recipients and ameliorate ongoing disease.     

Extracorporeal photopheresis therapy in the management of steroid-refractory or steroid-dependent cutaneous chronic graft-versus-host disease after allogeneic stem cell transplantation: feasibility and results

We conducted a retrospective analysis of all allogeneic stem cell transplantation (ASCT) patients started on extracorporeal photopheresis (ECP) for the management of steroid-dependent (SD) or steroid-refractory (SR) cutaneous chronic graft-versus-host disease (cGVHD) following ASCT during a 36-month period (9/98-8/01). Only SD or SR patients who were treated by ECP after day 100 and who received at least 4 weeks of ECP were considered evaluable for this analysis. Out of 64 ASCT patients reviewed, 32 patients met the inclusion criteria. All 32 patients had been previously treated with systemic corticosteroids with 11 (34%) being SR and 21 (66%) SD. Cutaneous cGVHD was extensive in 28 patients (88%) and was accompanied by visceral (hepatic, gastrointestinal) cGVHD in 23 patients (72%). The 32 evaluated patients had received a median of three prior therapies before ECP, most commonly systemic corticosteroids, tacrolimus, and mycophenolate mofetil. Patients received a median of 36 ECP sessions (range 12-98) over a median of 5.3 months (range 1-28), with a median of six sessions per month. The complete response (CR) rate was 22% (n=7) and the partial response rate was 34% (n=11). In all, 28 patients were on systemic corticosteroid therapy at ECP initiation and 18 patients achieved 50% dose reduction while on ECP, yielding a 64% steroid-sparing response rate. Of seven CRs, five are ongoing. A total of 11 (34%) patients have died after ECP, with all cases due to visceral cGVHD or cGVHD-related infectious complications. All 21 surviving patients remain on at least some immunosuppressive cGVHD therapy (including ECP in eight). Overall, ECP displays a substantial response rate and, in particular, steroid-sparing activity in SR/SD extensive cutaneous cGVHD. However, most patients continue to require at least some chronic therapy and cGVHD-related morbidity and mortality remain high.     

Ikaros-Notch axis in host hematopoietic cells regulates experimental graft-versus-host disease

Host hematopoietically derived APCs play a vital role in the initiation of GVH responses. However, the APC autonomous molecular mechanisms that are critical for the induction of GVHD are not known. We report here that the Ikaros-Notch axis in host hematopoietically derived APCs regulates the severity of acute GVHD across multiple clinically relevant murine models of experimental bone marrow transplantation. In the present study, Ikaros deficiency (Ik(-/-)) limited to host hematopoietically derived APCs enhanced donor T-cell expansion and intensified acute GVHD, as determined by survival and other GVHD-specific parameters. The Ik(-/-) conventional CD8(+) and CD8(-)CD11c(+) dendritic cells (DCs), the most potent APCs, showed no increase in the expression of activation markers or in response to TLR stimulation compared with wild-type controls. However, Ik(-/-) DCs demonstrated an enhanced stimulation of allogeneic T cells. Deficiency of Ikaros in the conventional CD8(+) and CD8(-)CD11c(+) DCs was associated with an increase in Notch signaling, the blockade of which mitigated the enhanced in vitro and in vivo allostimulatory capacity. Therefore, the Ikaros-Notch axis is a novel pathway that modulates DC biology in general, and targeting this pathway in host hematopoietically derived APCs may reduce GVHD.     

Allo-HLA-reactive T cells inducing graft-versus-host disease are single peptide specific

T-cell alloreactivity directed against non-self-HLA molecules has been assumed to be less peptide specific than conventional T-cell reactivity. A large variation in degree of peptide specificity has previously been reported, including single peptide specificity, polyspecificity, and peptide degeneracy. Peptide polyspecificity was illustrated using synthetic peptide-loaded target cells, but in the absence of confirmation against endogenously processed peptides this may represent low-avidity T-cell reactivity. Peptide degeneracy was concluded based on recognition of Ag-processing defective cells. In addition, because most investigated alloreactive T cells were in vitro activated and expanded, the previously determined specificities may have not been representative for alloreactivity in vivo. To study the biologically relevant peptide specificity and avidity of alloreactivity, we investigated the degree of peptide specificity of 50 different allo-HLA-reactive T-cell clones which were activated and expanded in vivo during GVHD. All but one of the alloreactive T-cell clones, including those reactive against Ag-processing defective T2 cells, recognized a single peptide allo-HLA complex, unique for each clone. Down-regulation of the expression of the recognized Ags using silencing shRNAs confirmed single peptide specificity. Based on these results, we conclude that biologically relevant alloreactivity selected during in vivo immune response is peptide specific.     

Robust and cost effective expansion of human regulatory T cells highly functional in a xenograft model of graft-versus-host disease

The low frequency of naturally occurring regulatory T cells (nTregs) in peripheral blood and the suboptimal protocols available for their ex vivo expansion limit the development of clinical trials based on the adoptive transfer of these cells. We have, therefore, generated a simplified, robust and cost-effective platform for the large-scale expansion of nTregs using a gas permeable static culture flask (G-Rex) in compliance with Good Manufacturing Practice. More than 10⁹ putative Tregs co-expressing CD25 and CD4 molecules (92±5%) and FoxP3 (69±19%) were obtained within 21 days of culture. Expanded Tregs showed potent regulatory activity in vitro (80±13% inhibition of CD8⁺ cell division) and in vivo (suppression or delay of graft-versus-host disease in a xenograft mouse model) indicating that the cost-effective and simplified production of nTregs we propose will facilitate the implementation of clinical trials based on their adoptive transfer.