Mesenchymal stromal cells transiently alter the inflammatory milieu post-transplant to delay graft-versus-host disease

BACKGROUND

Multipotent mesenchymal stromal cells suppress T-cell function in vitro, a property that has underpinned their use in treating clinical steroid-refractory graft-versus-host disease after allogeneic hematopoietic stem cell transplantation. However the potential of mesenchymal stromal cells to resolve graft-versus-host disease is confounded by a paucity of pre-clinical data delineating their immunomodulatory effects in vivo.

DESIGN AND METHODS

We examined the influence of timing and dose of donor-derived mesenchymal stromal cells on the kinetics of graft-versus-host disease in two murine models of graft-versus-host disease (major histocompatibility complex-mismatched: UBI-GFP/BL6 [H-2(b)]→BALB/c [H-2(d)] and the sibling transplant mimic, UBI-GFP/BL6 [H-2(b)]→BALB.B [H-2(b)]) using clinically relevant conditioning regimens. We also examined the effect of mesenchymal stromal cell infusion on bone marrow and spleen cellular composition and cytokine secretion in transplant recipients.

RESULTS

Despite T-cell suppression in vitro, mesenchymal stromal cells delayed but did not prevent graft-versus-host disease in the major histocompatibility complex-mismatched model. In the sibling transplant model, however, 30% of mesenchymal stromal cell-treated mice did not develop graft-versus-host disease. The timing of administration and dose of the mesenchymal stromal cells influenced their effectiveness in attenuating graft-versus-host disease, such that a low dose of mesenchymal stromal cells administered early was more effective than a high dose of mesenchymal stromal cells given late. Compared to control-treated mice, mesenchymal stromal cell-treated mice had significant reductions in serum and splenic interferon-γ, an important mediator of graft-versus-host disease.

CONCLUSIONS

Mesenchymal stromal cells appear to delay death from graft-versus-host disease by transiently altering the inflammatory milieu and reducing levels of interferon-γ. Our data suggest that both the timing of infusion and the dose of mesenchymal stromal cells likely influence these cells' effectiveness in attenuating graft-versus-host disease.

Interleukin-1 polymorphisms and graft-vs-host disease

Graft-vs-host disease (GVHD) remains a key limiting factor in the success of hematopoietic stem cell transplantation (HSCT). One of the key cytokines known to have a role in the pathogenesis of GVHD is interleukin-1 (IL-1). The IL-1 gene family consists of 10 members, of which 3 genes encode for the proteins IL-1a, IL-1ss and IL-1Ra (IL-1 receptor antagonist). Polymorphisms in these genes have been associated with variability in the production of the respective cytokines and have been implicated in patient susceptibility to inflammatory diseases, including GVHD. A number of reports have detailed genetic associations between members of the IL-1 gene family and HSCT outcomes. Despite these encouraging reports, a simple exploitation of these findings is probably naive. Differences in transplant practice between centers and within centers over time mean that directly comparable studies are rare. This combined with the complexity of IL-1-related transplant biology means that our understanding of this topic remains limited. This review details the current state of knowledge of IL-1 genetics and transplantation and discusses these issues in the context of the changing practice of transplantation.

Antibody to the dendritic cell surface activation antigen CD83 prevents acute graft-versus-host disease

Allogeneic (allo) hematopoietic stem cell transplantation is an effective therapy for hematological malignancies but it is limited by acute graft-versus-host disease (GVHD). Dendritic cells (DC) play a major role in the allo T cell stimulation causing GVHD. Current immunosuppressive measures to control GVHD target T cells but compromise posttransplant immunity in the patient, particularly to cytomegalovirus (CMV) and residual malignant cells. We showed that treatment of allo mixed lymphocyte cultures with activated human DC-depleting CD83 antibody suppressed alloproliferation but preserved T cell numbers, including those specific for CMV. We also tested CD83 antibody in the human T cell-dependent peripheral blood mononuclear cell transplanted SCID (hu-SCID) mouse model of GVHD. We showed that this model requires human DC and that CD83 antibody treatment prevented GVHD but, unlike conventional immunosuppressants, did not prevent engraftment of human T cells, including cytotoxic T lymphocytes (CTL) responsive to viruses and malignant cells. Immunization of CD83 antibody-treated hu-SCID mice with irradiated human leukemic cell lines induced allo antileukemic CTL effectors in vivo that lysed (51)Cr-labeled leukemic target cells in vitro without further stimulation. Antibodies that target activated DC are a promising new therapeutic approach to the control of GVHD.

Environmental factors and not genotype influence the plasma level of interleukin-1 receptor antagonist in normal individuals

Cytokine production may be regulated by both genotypic (single nucleotide or tandem repeat polymorphisms) and non-genotypic factors relating to the environment and inherent biology (i.e. gender). Interleukin (IL)-1 is one of the body's most highly proinflammatory cytokines and is implicated in the pathophysiology of numerous diseases, but also in the maintenance of homeostasis in a number of tissues. The cytokine IL-1 receptor antagonist (IL-1Ra) is the competitive inhibitor of the IL-1 agonists IL-1alpha and IL-1beta. In vivo IL-1Ra was measured in a cohort of 200 + blood donors and the effect of the IL-1 gene polymorphisms, environmental and biological factors assessed. In this study, we observed that possession of particular alleles of 5 IL-1 gene polymorphisms (IL1A-889, IL1Alpha VNTR, IL1B -511, IL1B +3953 and the IL1RN VNTR) did not correlate with higher plasma IL-1Ra levels. Environmental factors such as smoking and non-steroidal anti-inflammatory drug ingestion were associated with higher in vivo IL-1Ra levels (P = 0.015 and 0.022, respectively), but biological factors such as gender, age and menstruation status did not have any impact upon in vivo IL-1Ra levels. Genotypic associations of IL-1 gene family polymorphisms with disease features may reflect characteristics of stressed rather than normal control circuits for cytokine production.

Polymorphisms of interleukin-1alpha constitute independent risk factors for chronic graft-versus-host disease after allogeneic bone marrow transplantation

The interleukin-1 (IL-1) family of cytokines is widely involved in inflammatory processes and diseases with an inflammatory component. Polymorphisms of the IL-1alpha, IL-1beta and IL-1Ra genes have been implicated in a number of autoimmune or inflammatory conditions, with polymorphism of the IL-1Ra gene showing association with severity of graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT). We compared the clinical outcomes (GVHD and survival) of 115 patients after human leucocyte antigen (HLA)-identical sibling allogeneic BMT with their genotype for two polymorphisms present in the IL-1alpha gene, which have been implicated in immune-related pathology. Possession of allele 2 of the IL-1alpha-889 polymorphism and allele 2 of the IL-1alpha variable number tandem repeat (VNTR) polymorphism in the donor genotype was associated with the occurrence of chronic, but not acute GVHD. A local normal population was also genotyped for these polymorphisms, and subsequent analysis identified conserved haplotypes in this gene region. Haplotypes containing allele 2 at both IL-1alpha-889 and IL-1alpha VNTR loci were extremely uncommon, suggesting that both risk alleles would be inherited independently. Both loci could therefore function as independent disease association markers. The polymorphisms of the IL-1alpha gene could be used to predict chronic GVHD in HLA-matched sibling transplants alongside clinical risk factors.

Oestrogen receptor alpha gene polymorphism associates with occurrence of graft-versus-host disease and reduced survival in HLA-matched sib-allo BMT

Oestrogen receptors mediate the cellular response to oestrogens and related compounds and promote a wide range of effects on haemopoiesis. Polymorphisms of the oestrogen receptor genes have previously been associated with variation in bone mineral density, likelihood of fractures, risk of developing Alzheimer's disease, endometrial cancer and response to hormone replacement therapy. We examined the polymorphisms in both ERalpha and ERbeta genes in 108 patients receiving a bone marrow transplant from an HLA-matched sibling donor, and compared ER genotype with outcomes of occurrence of graft-versus-host disease (GVHD) and survival using logistic regression analysis. Polymorphism of ERalpha (presence of the PX haplotype (PvuII-XbaI RFLP) of intron 1), but not ERbeta, in the patient genotype associates with occurrence of acute GVHD and with lower overall survival, following correction for known clinical and genotypic risk features. Analysis of ER genotype prior to transplant might therefore inform on a patient's likelihood of developing post-transplant complications. Variation in transplant performance because of ER genotype suggests an underlying role for oestrogens in the pathophysiology of transplant-related complications, and suggests that oestrogen-related therapy may offer a new modality of post-transplant support.

Predicting outcome in hematological stem cell transplantation

This review summarizes recent results investigating the role of certain cytokine gene polymorphisms, including those of TNF-alpha, IFN-gamma, IL-6, IL-10 and IL-1 receptor antagonist (IL-1Ra), in allogeneic stem cell transplantation. It discusses their role in predicting outcome and the development of a genetic risk index for graft versus host disease (GvHD) in HLA-matched sibling transplants. By the comparative use of an in vitro human skin explant model, initial results suggest that certain cytokine gene polymorphisms may be associated with more severe disease.

New Developments in Allotransplant Immunology

After allogeneic stem cell transplantation, the establishment of the donor’s immune system in an antigenically distinct recipient confers a therapeutic graft-versus-malignancy effect, but also causes graft-versus-host disease (GVHD) and protracted immune dysfunction. In the last decade, a molecular-level description of alloimmune interactions and the process of immune recovery leading to tolerance has emerged. Here, new developments in understanding alloresponses, genetic factors that modify them, and strategies to control immune reconstitution are described.

In Section I, Dr. John Barrett and colleagues describe the cellular and molecular basis of the alloresponse and the mechanisms underlying the three major outcomes of engraftment, GVHD and the graft-versus-leukemia (GVL) effect. Increasing knowledge of leukemia-restricted antigens suggests ways to separate GVHD and GVL. Recent findings highlight a central role of hematopoietic-derived antigen-presenting cells in the initiation of GVHD and distinct properties of natural killer (NK) cell alloreactivity in engraftment and GVL that are of therapeutic importance. Finally, a detailed map of cellular immune recovery post-transplant is emerging which highlights the importance of post-thymic lymphocytes in determining outcome in the critical first few months following stem cell transplantation. Factors that modify immune reconstitution include immunosuppression, GVHD, the cytokine milieu and poorly-defined homeostatic mechanisms which encourage irregular T cell expansions driven by immunodominant T cell–antigen interactions.

In Section II, Prof. Anne Dickinson and colleagues describe genetic polymorphisms outside the human leukocyte antigen (HLA) system that determine the nature of immune reconstitution after allogeneic stem cell transplantation (SCT) and thereby affect transplant outcomethrough GVHD, GVL, and transplant-related mortality. Polymorphisms in cytokine gene promotors and other less characterized genes affect the cytokine milieu of the recipient and the immune reactivity of the donor. Some cytokine gene polymorphisms are significantly associated with transplant outcome. Other non-HLA genes strongly affecting alloresponses code for minor histocompatibility antigens (mHA). Differences between donor and recipient mHA cause GVHD or GVL reactions or graft rejection. Both cytokine gene polymorphisms (CGP) and mHA differences resulting on donor-recipient incompatibilities can be jointly assessed in the skin explant assay as a functional way to select the most suitable donor or the best transplant approach for the recipient.

In Section III, Dr. Nelson Chao describes non-pharmaceutical techniques to control immune reconstitution post-transplant. T cells stimulated by host alloantigens can be distinguished from resting T cells by the expression of a variety of activation markers (IL-2 receptor, FAS, CD69, CD71) and by an increased photosensitivity to rhodamine dyes. These differences form the basis for eliminating GVHD-reactive T cells in vitro while conserving GVL and anti-viral immunity. Other attempts to control immune reactions post-transplant include the insertion of suicide genes into the transplanted T cells for effective termination of GVHD reactions, the removal of CD62 ligand expressing cells, and the modulation of T cell reactivity by favoring Th2, Tc2 lymphocyte subset expansion. These technologies could eliminate GVHD while preserving T cell responses to leukemia and reactivating viruses.

Vitamin D receptor gene polymorphism associates with graft-versus-host disease and survival in HLA-matched sibling allogeneic bone marrow transplantation

We investigated the role of polymorphism of the vitamin D receptor (VDR) gene in HLA-matched sibling BMT for polymorphisms previously associated with human disease pathology. In intron 8 of the VDR gene, the B and A alleles of the BsmI and ApaI RFLPs were found to associate with reduced aGVHD when present in the patient's genotype. Logistic regression analysis demonstrated that patient VDR genotype, along with previously identified IL-10(-1064) and IFN-gamma genotype to be risk factors for severe acute GVHD. The A allele also associates with increased likelihood of death when present in the donor genotype (AA vs Aa or aa, hazard ratio 2.03, P = 0.0232). In patients who received increased prophylaxis with multi-agent therapy, patients whose graft was from a donor with an AA genotype had a substantially worse survival than patients whose graft was from a donor with a non-AA genotype (hazard ratio 12.93, P < 0.0001). Analysis of VDR genotype in prospective BMT recipients could indicate patients at risk of severe aGVHD. Analysis of VDR genotype in prospective BMT donors may identify individuals who have greater transplant-related mortality, and also allow appropriately restricted use of increased immunosuppressive prophylaxis.

GvHD risk assessment in hematopoietic stem cell transplantation: role of cytokine gene polymorphisms and an in vitro human skin explant model

This present review concentrates on the recent results investigating the role of certain cytokine gene polymorphisms, including tumor necrosis factor alpha, interferon gamma, interleukin-6 (IL-6), IL-10, and IL-1 receptor antagonist, in allogeneic stem cell transplantation. The review discusses their potential role in predicting outcome and the development of a genetic risk index for graft-versus-host disease in human leukocyte antigen matched sibling transplants. By the comparative use of an in vitro human skin explant model, initial results suggest that certain polymorphisms may be associated with more severe disease.

Donor interleukin 1 receptor antagonist genotype associated with acute graft-versus-host disease in human leucocyte antigen-matched sibling allogeneic transplants

Interleukin 1 (IL-1) is involved in various autoimmune and inflammatory diseases. IL-1 receptor antagonist (IL-1Ra) is the naturally occurring antagonist to IL-1alpha and -1beta. Polymorphisms of IL-1beta have been associated with variations in IL-1beta production (nucleotides +3953 and -511). A variable number tandem repeat (VNTR) polymorphism in the IL-1Ra gene has been associated (allele 2) with increased IL-1Ra production. We examined these polymorphisms in human leucocyte antigen (HLA)-matched allogeneic bone marrow transplant patients and donors. IL-1Ra VNTR (allele 2) in the donor genotype was more frequent with milder acute graft-versus-host disease (aGvHD) grades 0-II (29 out of 59 transplants) than severe GvHD grades III-IV (2 out of 18 transplants) (P = 0.0032). This association was confirmed in a subgroup with cyclosporine monotherapy prophylaxis: donor possession of allele 2 was again associated with milder aGvHD, grades 0-II (19 out of 38 transplants), than grades III-IV (1 out of 14) (P = 0.0042) transplants. No association was found between the IL-1beta -511 or IL-1beta +3953 polymorphism and severity of GvHD. Recipient IL-1Ra VNTR genotype (allele 2) showed a strong trend towards association with aGvHD severity (P = 0.0697). Thus, the donor genotype for the IL-1Ra polymorphism has an apparent protective role against acute GvHD following transplantation and may be an additional factor for individual risk assessment for complications, including GvHD, post transplant.