Blood TRANSPLANTATION

Autologous bone marrow transplantation in autoimmune arthritis restores immune homeostasis through CD4+CD25+Foxp3+ regulatory T cells

2008-05-08

Despite the earlier use of potent immunosuppressive or cytostatic drugs and the recent emergence of biologicals as treatment for human autoimmune diseases (AIDs), some patients still remain unresponsive to treatment. To those severely ill patients, autologous bone marrow transplantation (aBMT) is applied as a last resource, leading to disease remission in a majority of patients. The underlying mechanism of action of aBMT is still largely unknown. Here, we showed that regulatory T cells (Tregs) play a role in the natural disease course of proteoglycan-induced arthritis (PGIA) and in disease remission by aBMT. aBMT led to an initial phase of rapid disease improvement corresponding with a relative increase in CD4⁺CD25⁺ T cells. At this time, the CD4⁺CD25⁺ cells did not yet show an increase in Foxp3 expression and showed less potent suppression. After this initial improvement, disease relapsed but stabilized at a level below the severity before aBMT. This second phase was actively regulated by potently suppressive CD4⁺CD25⁺Foxp3⁺ Tregs. This work provided further insight into the role of Tregs in restoration of the immune balance by aBMT and can open the way to explore therapeutic interventions to further improve treatment of AID and disease relapses.

Effects of donor T-cell trafficking and priming site on graft-versus-host disease induction by naive and memory phenotype CD4 T cells

2008-05-08

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality in allogeneic stem cell transplantation. Effector memory T cells (T_EM) do not cause GVHD but engraft and mount immune responses, including graft-versus-tumor effects. One potential explanation for the inability of T_EM to cause GVHD is that T_EM lack CD62L and CCR7, which are instrumental in directing naive T cells (T_N) to lymph nodes (LN) and Peyer patches (PP), putative sites of GVHD initiation. Thus T_EM should be relatively excluded from LN and PP, possibly explaining their inability to cause GVHD. We tested this hypothesis using T cells deficient in CD62L or CCR7, transplant recipients lacking PNAd ligands for CD62L, and recipients without LN and PP or LN, PP, and spleen. Surprisingly, CD62L and CCR7 were not required for T_N-mediated GVHD. Moreover, in multiple strain pairings, GVHD developed in recipients that lacked LN and PP. Mild GVHD could even be induced in mice lacking all major secondary lymphoid tissues (SLT). Conversely, enforced constitutive expression of CD62L on T_EM did not endow them with the ability to cause GVHD. Taken together, these data argue against the hypothesis that T_EM fail to induce GVHD because of inefficient trafficking to LN and PP.

Complete molecular responses are achieved after reduced intensity stem cell transplantation and donor lymphocyte infusion in chronic myeloid leukemia

2008-05-08

Patients with newly diagnosed chronic phase chronic myeloid leukemia were treated with imatinib mesylate (IM) for 6 to 12 months to establish disease control, before reduced intensity stem cell transplantation (RISCT). Escalating doses of donor lymphocyte infusions were given from 6 months after transplantation to eradicate residual disease. A total of 18 patients entered the study and 15 received RISCT (median follow-up, 31 months). RISCT was well tolerated with rapid engraftment, short inpatient stays, and few readmissions. Viral reactivation was common, although extensive graft-versus-host disease occurred infrequently. Donor lymphocyte infusions were given as part of the RISCT protocol in 13 of 15 patients. BCR-ABL transcripts continued to decrease after RISCT, and 8 (53%) patients achieved sustained undetectable levels. All patients are currently off IM. Although IM is now established as first-line therapy for chronic phase chronic myeloid leukemia, this protocol is a safe, well-tolerated, and effective strategy in these patients. This study is registered at http://www.controlled-trials.com as ISRCTN86187144.

DDX3Y encodes a class I MHC-restricted H-Y antigen that is expressed in leukemic stem cells

2008-04-25

The Y chromosome encodes male-specific minor histocompatibility (H-Y) antigens that stimulate T- and B-lymphocyte responses after sex-mismatched allogeneic hematopoietic cell transplantation (HCT). A CD8⁺ cytotoxic T lymphocyte (CTL) clone that recognizes a novel HLA-B*2705–restricted H-Y antigen encoded by the DDX3Y gene was isolated from a male who had received a hematopoietic cell graft from his human leukocyte antigen (HLA)–identical sister. The antigenic peptide is a decamer that differs from the homologous DDX3X-encoded peptide at 4 positions. Expression of DDX3Y and of the H-Y epitope that it encodes was examined by quantitative polymerase chain reaction (PCR) and by CTL recognition assays. Expression of DDX3Y is detected in all myeloid and lymphoid leukemic cells that carry an intact Y chromosome. Moreover, the DDX3Y-encoded H-Y epitope is presented on the surface of both myeloid and lymphoid leukemic cells from male HLA-B*2705⁺ patients. DDX3Y-specific CTLs prevent engraftment of human acute leukemia in nonobese diabetic/severe combined immune deficient mice, demonstrating that the DDX3Y-encoded H-Y antigen is also expressed in leukemic stem cells. These results demonstrate that CD8⁺ T-cell responses against DDX3Y have the potential to contribute to graft-versus-leukemia (GVL) activity after female into male allogeneic HCT. This study is registered at http://clinicaltrials.gov as NCT00107354.

Donor cell-derived osteopoiesis originates from a self-renewing stem cell with a limited regenerative contribution after transplantation

2008-04-08

In principle, bone marrow transplantation should offer effective treatment for disorders originating from defects in mesenchymal stem cells. Results with the bone disease osteogenesis imperfecta support this hypothesis, although the rate of clinical improvement seen early after transplantation does not persist long term, raising questions as to the regenerative capacity of the donor-derived mesenchymal progenitors. We therefore studied the kinetics and histologic/anatomic pattern of osteopoietic engraftment after transplantation of GFP-expressing nonadherent marrow cells in mice. Serial tracking of donor-derived GFP⁺ cells over 52 weeks showed abundant clusters of donor-derived osteoblasts/osteocytes in the epiphysis and metaphysis but not the diaphysis, a distribution that paralleled the sites of initial hematopoietic engraftment. Osteopoietic chimerism decreased from approximately 30% to 10% by 24 weeks after transplantation, declining to negligible levels thereafter. Secondary transplantation studies provided evidence for a self-renewing osteopoietic stem cell in the marrow graft. We conclude that a transplantable, primitive, self-renewing osteopoietic cell within the nonadherent marrow cell population engrafts in an endosteal niche, like hematopoietic stem cells, and regenerates a significant fraction of all bone cells. The lack of durable donor-derived osteopoiesis may reflect an intrinsic genetic program or exogenous environmental signaling that suppresses the differentiation capacity of the donor stem cells.

A clinical-scale selective allodepletion approach for the treatment of HLA-mismatched and matched donor-recipient pairs using expanded T lymphocytes as antigen-presenting cells and a TH9402-based photodepletion technique

2008-04-08

Selective allodepletion is a strategy to eliminate host-reactive donor T cells from hematopoietic stem cell allografts to prevent graft-versus-host disease while conserving useful donor immune functions. To overcome fluctuations in activation-based surface marker expression and achieve a more consistent and effective allodepletion, we investigated a photodepletion process targeting activation-based changes in p-glycoprotein that result in an altered efflux of the photosensitizer TH9402. Expanded lymphocytes, generated using anti-CD3 and IL-2, were cocultured with responder cells from HLA-matched or -mismatched donors. Optimal results were achieved when cocultured cells were incubated with 7.5 µM TH9402, followed by dye extrusion and exposure to 5 Joule/cm² light energy at 5 x 10⁶ cells/mL. In mismatched stimulator-responder pairs, the median reduction of alloreactivity was 474-fold (range, 43-fold to 864-fold) compared with the unmanipulated responder. Third-party responses were maintained with a median 1.4-fold (range, 0.9-fold to 3.3-fold) reduction. In matched pairs, alloreactive helper T-lymphocyte precursors were reduced to lower than 1:100 000, while third-party responses remained higher than 1:10 000. This establishes a clinical-scale process capable of highly efficient, reproducible, selective removal of alloreactive lymphocytes from lymphocyte transplant products performed under current Good Manufacturing Practice. This procedure is currently being investigated in a clinical trial of allotransplantation.

CCL8 is a potential molecular candidate for the diagnosis of graft-versus-host disease

2008-04-08

Although graft-versus-host disease (GVHD) is a life-threatening complication of hematopoietic stem-cell transplantation (HSCT), its current diagnosis depends mainly on clinical manifestations and invasive biopsies. Specific biomarkers for GVHD would facilitate early and accurate recognition of this grave condition. Using proteomics, we screened for plasma proteins specific for GVHD in a mouse model. One peak with 8972-Da molecular mass (m/z) retained a discriminatory value in 2 diagnostic groups (GVHD and normal controls) with increased expression in the disease and decreased expression during cyclosporin A treatment, and was barely detectable in syngeneic transplantation. Purification and mass analysis identified this molecule as CCL8, a member of a large chemokine family. In human samples, the serum concentration of CCL8 correlated closely with GVHD severity. All non-GVHD samples contained less than 48 pg/mL (mean ± SE: 22.5 ± 5.5 pg/mL, range: 12.6-48.0 pg/mL, n = 7). In sharp contrast, CCL8 was highly up-regulated in GVHD sera ranging from 52.0 to 333.6 pg/mL (mean ± SE: 165.0 ± 39.8 pg/mL, n = 7). Strikingly, 2 patients with severe fatal GVHD had extremely high levels of CCL8 (333.6 and 290.4 pg/mL. CCL8 is a promising specific serum marker for the early and accurate diagnosis of GVHD.

CD8+ but not CD4+ T cells require cognate interactions with target tissues to mediate GVHD across only minor H antigens, whereas both CD4+ and CD8+ T cells require direct leukemic contact to mediate GVL

Matte-Martone, C., Liu, J., Jain, D., McNiff, J., Shlomchik, W. D. — 2008-03-24

Whether T-cell antigen receptors (TCR) on donor T cells require direct interactions with major histocompatibility complex class I or class II (MHCI/MHCII) molecules on target cells to mediate graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) is a fundamental question in allogeneic stem-cell transplantation (alloSCT). In MHC-mismatched mouse models, these contacts were not required for GVHD. However, this conclusion may not apply to MHC-matched, multiple minor histocompatibility antigen-mismatched alloSCT, the most common type performed clinically. To address this, we used wild-type (wt)->MHCI^–/– or wt->MHCII^–/– bone marrow chimeras as recipients in GVHD experiments. For GVL experiments, we used MHCI^–/– or MHCII^–/– chronic-phase CML cells created by expressing the BCR-ABL cDNA in bone marrow from MHCI^–/– or MHCII^–/– mice. TCR/MHCI contact was obligatory for both CD8-mediated GVHD and GVL. In contrast, CD4 cells induced GVHD in wt->MHCII^–/– chimeras, whereas MHCII^–/– mCP-CML was GVL-resistant. Donor CD4 cells infiltrated affected skin and bowel in wt->MHCII^–/– recipients, indicating that they mediated GVHD by acting locally. Thus, CD4 cells use distinct effector mechanisms in GVHD and GVL: direct cytolytic action is required for GVL but not for GVHD. If these noncytolytic pathways can be inhibited, then GVHD might be ameliorated while preserving GVL.

The monoclonal anti-VLA-4 antibody natalizumab mobilizes CD34+ hematopoietic progenitor cells in humans

Zohren, F., Toutzaris, D., Klarner, V., Hartung, H.-P., Kieseier, B., Haas, R. — 2008-03-24

We investigated the role of adhesion molecule VLA-4 in CD34⁺ blood stem-cell mobilization. Therefore, we examined 20 patients with multiple sclerosis (MS) who were treated with the anti–VLA-4 antibody natalizumab. Treated patients had received a median number of 4 natalizumab infusions (range: 2-9 infusions). Blood samples were taken 4 weeks following the last infusion. With a median proportion of 7.6 CD34⁺ cells/µL (range: 2.2-30.4 cells/µL), these patients had a significantly higher (P = .003) amount of circulating CD34⁺ cells compared with 5 healthy volunteers (median: 1.4/µL; range: 0.6-2.4/µL) and 5 untreated MS patients (median: 1.0/µL; range: 0.5-1.7/µL) (P = .001). Serial measurements in 4 patients receiving their first natalizumab infusion showed a maximal significant increase in circulating CD34⁺ cells from 3.3/µL (range: 1.6-4.8/µL) to 10.4/µL (range: 7.5-12.04/µL) 72 hours following natalizumab infusion (P = .001), including pluripotent cells in colony-forming assays. This mobilizing ability of natalizumab might be useful for patients with poor response to granulocyte colony-stimulating factor (G-CSF)–based protocols.