Transfer of hematopoietic stem cells encoding autoantigen prevents autoimmune diabetes

111 years of allergen-immunotherapy: A long and successful history of the only available disease-modifier in allergic diseases

The great milestones in medicine almost always have their precursors, which help the great event to break through. So it was with allergen-specific immunotherapy (AIT) and the great work of Noon and Freeman and their world-renowned publication in 1911. In this article, we want to outline AIT's long journey, from early attempts to achieve tolerance to allergens in the environment. Many very different methods were used; from homeopathy to the use of recombinant allergens. Initially, the allergen extracts were given only subcutaneously, but then also through other routes, such as nasal, rectal, intradermal, epicutaneous, in lymph nodes, or oral. It was the great merit of Bill Franklin, whom many of us still experienced as active participants in congresses, to point out that the effect of AIT must be documented not only by clinical observation but in a controlled form including placebo injections. AIT was thus transferred to evidence-based medicine, which we successfully apply today. We would like to express our gratitude to Bill Franklin himself and all others involved in the development of AIT with this summary of 111 years of immunotherapy.

Hematopoietic Stem Cells in Type 1 Diabetes

Despite the increasing knowledge of pathophysiological mechanisms underlying the onset of type 1 diabetes (T1D), the quest for therapeutic options capable of delaying/reverting the diseases is still ongoing. Among all strategies currently tested in T1D, the use of hematopoietic stem cell (HSC)-based approaches and of teplizumab, showed the most encouraging results. Few clinical trials have already demonstrated the beneficial effects of HSCs in T1D, while the durability of the effect is yet to be established. Investigators are also trying to understand whether the use of selected and better-characterized HSCs subsets may provide more benefits with less risks. Interestingly, ex vivo manipulated HSCs showed promising results in murine models and the recent introduction of the humanized mouse models accelerated the translational potentials of such studies and their final road to clinic. Indeed, immunomodulatory as well as trafficking abilities can be enhanced in genetically modulated HSCs and genetically engineered HSCs may be viewed as a novel "biologic" therapy, to be further tested and explored in T1D and in other autoimmune/immune-related disorders.

The dark side of insulin: A primary autoantigen and instrument of self-destruction in type 1 diabetes

Background

Since its discovery 100 years ago, insulin, as the ‘cure’ for type 1 diabetes, has rescued the lives of countless individuals. As the century unfolded and the autoimmune nature of type 1 diabetes was recognised, a darker side of insulin emerged. Autoimmunity to insulin was found to be an early marker of risk for type 1 diabetes in young children. In humans, it remains unclear if autoimmunity to insulin is primarily due to a defect in the beta cell itself or to dysregulated immune activation. Conversely, it may be secondary to beta-cell damage from an environmental agent (e.g., virus). Nevertheless, direct, interventional studies in non-obese diabetic (NOD) mouse models of type 1 diabetes point to a critical role for (pro)insulin as a primary autoantigen that drives beta cell pathology.

Scope of review

Modelled on Koch's postulates for the pathogenicity of an infectious agent, evidence for a pathogenic role of (pro)insulin as an autoantigen in type 1 diabetes, particularly applicable to the NOD mouse model, is reviewed. Evidence in humans remains circumstantial. Additionally, as (pro)insulin is a target of autoimmunity in type 1 diabetes, its application as a therapeutic tool to elicit antigen-specific immune tolerance is assessed.

Major conclusions

Paradoxically, insulin is both a ‘cure’ and a potential ‘cause’ of type 1 diabetes, actively participating as an autoantigen to drive autoimmune destruction of beta cells - the instrument of its own destruction.

Adaptive Immunity and Pathogenesis of Diabetes: Insights Provided by the α4-Integrin Deficient NOD Mouse

Background: The spontaneously diabetic “non-obese diabetic” (NOD) mouse is a faithful model of human type-1 diabetes (T1D). Methods: Given the pivotal role of α4 integrin (CD49d) in other autoimmune diseases, we generated NOD mice with α4-deficient hematopoiesis (NOD.α4-/-) to study the role of α4 integrin in T1D. Results: NOD.α4-/- mice developed islet-specific T-cells and antibodies, albeit quantitatively less than α4+ counterparts. Nevertheless, NOD.α4-/- mice were completely and life-long protected from diabetes and insulitis. Moreover, transplantation with isogeneic α4-/- bone marrow prevented progression to T1D of pre-diabetic NOD.α4+ mice despite significant pre-existing islet cell injury. Transfer of α4+/CD3+, but not α4+/CD4+ splenocytes from diabetic to NOD.α4-/- mice induced diabetes with short latency. Despite an only modest contribution of adoptively transferred α4+/CD3+ cells to peripheral blood, pancreas-infiltrating T-cells were exclusively graft derived, i.e., α4+. Microbiota of diabetes-resistant NOD.α4-/- and pre-diabetic NOD.α4+ mice were identical. Co- housed diabetic NOD.α4+ mice showed the characteristic diabetic dysbiosis, implying causality of diabetes for dysbiosis. Incidentally, NOD.α4-/- mice were protected from autoimmune sialitis. Conclusion: α4 is a potential target for primary or secondary prevention of T1D.

Transfer of antigen-encoding bone marrow under immune-preserving conditions deletes mature antigen-specific B cells in recipients and inhibits antigen-specific antibody production

BACKGROUND AIMS

Pathological activation and collaboration of T and B cells underlies pathogenic autoantibody responses. Existing treatments for autoimmune disease cause non-specific immunosuppression, and induction of antigen-specific tolerance remains an elusive goal. Many immunotherapies aim to manipulate the T-cell component of T-B interplay, but few directly target B cells. One possible means to specifically target B cells is the transfer of gene-engineered BM that, once engrafted, gives rise to widespread specific and tolerogenic antigen expression within the hematopoietic system.

METHODS

Gene-engineered bone marrow encoding ubiquitous ovalbumin expression was transferred after low-dose (300-cGy) immune-preserving irradiation. B-cell responsiveness was monitored by analyzing ovalbumin-specific antibody production after immunization with ovalbumin/complete Freund's adjuvant. Ovalbumin-specific B cells and their response to immunization were analyzed using multi-tetramer staining. When antigen-encoding bone marrow was transferred under immune-preserving conditions, cognate antigen-specific B cells were purged from the recipient's preexisting B-cell repertoire and the repertoire that arose after bone marrow transfer.

RESULTS

OVA-specific B-cell deletion was apparent within the established host B-cell repertoire as well as that developing after gene-engineered bone marrow transfer. OVA-specific antibody production was substantially inhibited by transfer of OVA-encoding BM and activation of OVA-specific B cells, germinal center formation and subsequent OVA-specific plasmablast differentiation were all inhibited. Low levels of gene-engineered bone marrow chimerism were sufficient to limit antigen-specific antibody production.

RESULTS

These data show that antigen-specific B cells within an established B-cell repertoire are susceptible to de novo tolerance induction, and this can be achieved by transfer of gene-engineered bone marrow. This adds further dimensions to the utility of antigen-encoding bone marrow transfer as an immunotherapeutic tool.

Antigen presenting cell-targeted proinsulin expression converts insulin-specific CD8+ T-cell priming to tolerance in autoimmune-prone NOD mice

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing pancreatic β cells. Therapies need to incorporate strategies to overcome the genetic defects that impair induction or maintenance of peripheral T-cell tolerance and contribute to disease development. We tested whether the enforced expression of an islet autoantigen in antigen-presenting cells (APC) counteracted peripheral T-cell tolerance defects in autoimmune-prone NOD mice. We observed that insulin-specific CD8⁺ T cells transferred to mice in which proinsulin was transgenically expressed in APCs underwent several rounds of division and the majority were deleted. Residual insulin-specific CD8⁺ T cells were rendered unresponsive and this was associated with TCR downregulation, loss of tetramer binding and expression of a range of co-inhibitory molecules. Notably, accumulation and effector differentiation of insulin-specific CD8⁺ T cells in pancreatic lymph nodes was prominent in non-transgenic recipients but blocked by transgenic proinsulin expression. This shift from T-cell priming to T-cell tolerance exemplifies the tolerogenic capacity of autoantigen expression by APC and the capacity to overcome genetic tolerance defects.

APC-targeted proinsulin expression inactivates insulin-specific memory CD8+ T cells in NOD mice

Type 1 diabetes (T1D) results from T-cell-mediated autoimmune destruction of pancreatic β cells. Effector T-cell responses emerge early in disease development and expand as disease progresses. Following β-cell destruction, a long-lived T-cell memory is generated that represents a barrier to islet transplantation and other cellular insulin-replacement therapies. Development of effective immunotherapies that control or ablate β-cell destructive effector and memory T-cell responses has the potential to prevent disease progression and recurrence. Targeting antigen expression to antigen-presenting cells inactivates cognate CD8⁺ effector and memory T-cell responses and has therapeutic potential. Here we investigated this in the context of insulin-specific responses in the non-obese diabetic mouse where genetic immune tolerance defects could impact on therapeutic tolerance induction. Insulin-specific CD8⁺ memory T cells transferred to mice expressing proinsulin in antigen-presenting cells proliferated in response to transgenically expressed proinsulin and the majority were rapidly deleted. A small proportion of transferred insulin-specific Tmem remained undeleted and these were antigen-unresponsive, exhibited reduced T cell receptor (TCR) expression and H-2K^d/insB_15-23 tetramer binding and expressed co-inhibitory molecules. Expression of proinsulin in antigen-presenting cells also abolished the diabetogenic capacity of CD8⁺ effector T cells. Therefore, destructive insulin-specific CD8⁺ T cells are effectively inactivated by enforced proinsulin expression despite tolerance defects that exist in diabetes-prone NOD mice. These findings have important implications in developing immunotherapeutic approaches to T1D and other T-cell-mediated autoimmune diseases.

Allergen-encoding bone marrow transfer inactivates allergic T cell responses, alleviating airway inflammation

Memory Th2 cell responses underlie the development and perpetuation of allergic diseases. Because these states result from immune dysregulation, established Th2 cell responses represent a significant challenge for conventional immunotherapies. New approaches that overcome the detrimental effects of immune dysregulation are required. We tested whether memory Th2 cell responses were silenced using a therapeutic approach where allergen expression in DCs is transferred to sensitized recipients using BM cells as a vector for therapeutic gene transfer. Development of allergen-specific Th2 responses and allergen-induced airway inflammation was blocked by expression of allergen in DCs. Adoptive transfer studies showed that Th2 responses were inactivated by a combination of deletion and induction of T cell unresponsiveness. Transfer of BM encoding allergen expression targeted to DCs terminated, in an allergen-specific manner, Th2 responses in sensitized recipients. Importantly, when preexisting airway inflammation was present, there was effective silencing of Th2 cell responses, airway inflammation was alleviated, and airway hyperreactivity was reversed. The effectiveness of DC-targeted allergen expression to terminate established Th2 responses in sensitized animals indicates that exploiting cell-intrinsic T cell tolerance pathways could lead to development of highly effective immunotherapies.

Short-course rapamycin treatment enables engraftment of immunogenic gene-engineered bone marrow under low-dose irradiation to permit long-term immunological tolerance

Background

Application of genetically modified hematopoietic stem cells is increasingly mooted as a clinically relevant approach to protein replacement therapy, immune tolerance induction or conditions where both outcomes may be helpful. Hematopoietic stem and progenitor cell (HSPC)-mediated gene therapy often requires highly toxic pretransfer recipient conditioning to provide a ‘niche’ so that transferred HSPCs can engraft effectively and to prevent immune rejection of neoantigen-expressing engineered HSPCs. For widespread clinical application, reducing conditioning toxicity is an important requirement, but reduced conditioning can render neoantigen-expressing bone marrow (BM) and HSC susceptible to immune rejection if immunity is retained.

Methods

BM or HSPC-expressing OVA ubiquitously (actin.OVA) or targeted to MHC II+ cells was transferred using low-dose (300 cGy) total body irradiation. Recipients were administered rapamycin, cyclosporine or vehicle for 3 weeks commencing at BM transfer. Engraftment was determined using CD45 congenic donors and recipients. Induction of T-cell tolerance was tested by immunising recipients and analysing in-vivo cytotoxic T-lymphocyte (CTL) activity. The effect of rapamycin on transient effector function during tolerance induction was tested using an established model of tolerance induction where antigen is targeted to dendritic cells.

Results

Immune rejection of neoantigen-expressing BM and HSPCs after low-dose irradiation was prevented by a short course of rapamycin, but not cyclosporine, treatment. Whereas transient T-cell tolerance developed in recipients of OVA-expressing BM administered vehicle, only when engraftment of neoantigen-expressing BM was facilitated with rapamycin treatment did stable, long-lasting T-cell tolerance develop. Rapamycin inhibited transient effector function development during tolerance induction and inhibited development of CTL activity in recipients of OVA-expressing BM.

Conclusions

Rapamycin acts to suppress acquisition of transient T-cell effector function during peripheral tolerance induction elicited by HSPC-encoded antigen. By facilitating engraftment, short-course rapamycin permits development of long-term stable T-cell tolerance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0508-3) contains supplementary material, which is available to authorized users.

Inducing Specific Immune Tolerance to Prevent Type 1 Diabetes in NOD Mice

OBJECTIVES

Proinsulin is the first autoantigen in type 1 diabetes (T1D). We reasoned that coupling hematopoietic stem cells (HSCs) transplantation with ex vivo transduction of syngeneic HSCs with lentiviral vectors to express proinsulin II could prevent T1D in nonobese diabetic (NOD) mice.

METHODS

Hematopoietic stem cells were isolated from 6- to 8-week-old NOD female mice and transduced in vitro with lentiviral vectors encoding proinsulin II. Preconditioned 3- to 4-week-old female NOD mice were transplanted with transduced or nontransduced HSCs and compared with age-matched unmanipulated control. The insulitis, T1D development, and immune reconstitution were assessed.

RESULTS

The mean (SD) insulitis score was significantly reduced (1.156 [0.575] vs 2.156 [0.892] or 3.043 [0.728], P = 0.009 or <0.001), and diabetes was nearly completely prevented (1/13 vs 5/12 or 4/9, P = 0.031 or 0.013) in recipients of transduced HSCs expressing proinsulin II as compared with recipients of nontransduced HSCs or unmanipulated control. Sialitis, reconstitution of peripheral blood leukocytes, and in vitro recall responses to ovalbumin were not different between 3 groups of mice.

CONCLUSIONS

Syngeneic transplantation of HSCs transduced ex vivo with lentiviral vectors to encode proinsulin II is a novel strategy to prevent T1D.

Antigen-encoding bone marrow terminates islet-directed memory CD8+ T-cell responses to alleviate islet transplant rejection

Islet-specific memory T cells arise early in type 1 diabetes (T1D), persist for long periods, perpetuate disease and are rapidly reactivated by islet transplantation. As memory T cells are poorly controlled by 'conventional' therapies, memory T-cell mediated attack is a substantial challenge in islet transplantation and this will extend to application of personalized approaches using stem-cell derived replacement β cells. New approaches are required to limit memory autoimmune attack of transplanted islets or replacement β cells. Here we show that transfer of bone marrow encoding cognate antigen directed to dendritic cells, under mild, immune-preserving conditions inactivates established memory CD8⁺ T-cell populations and generates a long-lived, antigen-specific tolerogenic environment. Consequently, CD8⁺ memory T cell-mediated targeting of islet-expressed antigens is prevented and islet graft rejection alleviated. The immunological mechanisms of protection are mediated through deletion and induction of unresponsiveness in targeted memory T-cell populations. The data demonstrate that hematopoietic stem cell-mediated gene therapy effectively terminates antigen-specific memory T-cell responses and this can alleviate destruction of antigen-expressing islets. This addresses a key challenge facing islet transplantation and importantly, the clinical application of personalized β-cell replacement therapies using patient-derived stem cells.

Immunological Basis for Rapid Progression of Diabetes in Older NOD Mouse Recipients Post BM-HSC Transplantation

Type I diabetes (T1D), mediated by autoreactive T cell destruction of insulin-producing islet beta cells, has been treated with bone marrow-derived hematopoietic stem cell (BM-HSC) transplantation. Older non-obese diabetic (NOD) mice recipients (3m, at disease-onset stage) receiving syngeneic BM-HSC progressed more rapidly to end-stage diabetes post-transplantation than younger recipients (4-6w, at disease-initiation stage). FACS analyses showed a higher percentage and absolute number of regulatory T cells (Treg) and lower proportion of proliferating T conventional cells (Tcon) in pancreatic lymph nodes from the resistant mice among the younger recipients compared to the rapid progressors among the older recipients. Treg distribution in spleen, mesenteric lymph nodes (MLN), blood and thymus between the two groups was similar. However, the percentage of thymic Tcon and the proliferation of Tcon in MLN and blood were lower in the young resistants. These results suggest recipient age and associated disease stage as a variable to consider in BM-HSC transplantation for treating T1D.

CD201 and CD27 identify hematopoietic stem and progenitor cells across multiple murine strains independently of Kit and Sca-1

Identification and isolation of hematopoietic stem cells (HSCs) in mice is most commonly based on the expression of surface molecules Kit and Sca-1 and the absence of markers of mature lineages. However, Sca-1 is absent or weakly expressed in hematopoietic progenitors in many strains, including nonobese diabetic (NOD), BALB/c, C3H, and CBA mice. In addition, both Kit and Sca-1 levels are modulated following bone marrow injury. In these cases, other markers and dye exclusion methods have been employed to identify HSCs, yet there is no antibody-based stain that enables identification of HSCs and early progenitors when Kit and Sca-1 are inadequate. CD201 is a marker that is highly restricted to HSCs and progenitors, and CD27 is expressed at moderate-to-high levels on HSCs. We show here that combining CD201 and CD27 enables highly efficient isolation of long-term HSCs in NOD mice as well as in other strains, including SJL, FVB, AKR, BALB/c, C3H, and CBA. We also find that HSCs appear to maintain expression of CD201 and CD27 after hematopoietic injury when Kit expression is downregulated. These results suggest a widely applicable yet simple alternative for HSC isolation in settings where Kit and Sca-1 expression are insufficient.

Antigen presentation in the autoimmune diabetes of the NOD mouse

This paper reviews the presentation of peptides by major histocompatibility complex (MHC) class II molecules in the autoimmune diabetes of the nonobese diabetic (NOD) mouse. Islets of Langerhans contain antigen-presenting cells that capture the proteins and peptides of the beta cells' secretory granules. Peptides bound to I-A(g7), the unique MHC class II molecule of NOD mice, are presented in islets and in pancreatic lymph nodes. The various beta cell-derived peptides interact with selected CD4 T cells to cause inflammation and beta cell demise. Many autoreactive T cells are found in NOD mice, but not all have a major role in the initiation of the autoimmune process. I emphasize here the evidence pointing to insulin autoreactivity as a seminal component in the diabetogenic process.

Self-antigen expression in the peripheral immune system: roles in self-tolerance and type 1 diabetes pathogenesis

Type 1 diabetes (T1D) may result from a breakdown in peripheral tolerance that is partially controlled by the ectopic expression of peripheral tissue antigens (PTAs) in lymph nodes. Various subsets of lymph node stromal cells and certain hematopoietic cells play a role in maintaining T cell tolerance. These specialized cells have been shown to endogenously transcribe, process, and present a range of PTAs to naive T cells and mediate the clonal deletion or inactivation of autoreactive cells. During the progression of T1D, inflammation leads to reduced PTA expression in the pancreatic lymph nodes and the production of novel islet antigens that T cells are not tolerized against. These events allow for the escape and activation of autoreactive T cells and may contribute to the pathogenesis of T1D. In this review, we discuss recent findings in this area and propose possible therapies that may help reestablish self-tolerance during T1D.

Comparison of transduction efficiency among various lentiviruses containing GFP reporter in bone marrow hematopoietic stem cell transplantation

HIV-derived lentiviral vectors have been used widely to transduce non-dividing cells, such as hematopoietic stem cells (HSCs), in the setting of gene therapy. In this study, we screened lentiviral vectors for their ability to drive expression of the murine MHC class II chaperone, invariant chain (Ii) and a GFP reporter. The vectors included T2A vector with T2A-separated Ii and GFP under the same MSCV promoter, dual-promoter vectors with separate promoters for Ii and GFP (called MSCV or EF1a according to the promoter driving Ii expression), and a vector with EF1a driving a fusion of Ii/GFP (called Fusion vector). T2A and MSCV induced the highest levels of Ii and GFP expression, respectively, after direct transfection of 293T cells. All vectors except the Fusion vector drove expression of functional Ii, based on the enhancement of MHC class II level, which is a known consequence of Ii expression. Comparing the vectors after they were packaged into lentiviruses and used to transduce 293T, we found that MSCV and EF1a vectors mediated higher Ii and GFP expression. In ckit(+) bone marrow (BM) cells, MSCV still induced the highest Ii and GFP expression, whereas EF1a induced only robust Ii expression. Regardless of the vector, both Ii and GFP levels were significantly reduced in BM cells compared to 293T cells. When in vivo expression was assessed in cells derived from MSCV-transduced BM-HSCs, up to 80% of myeloid cells were GFP(+), but no Ii expression was observed. In contrast, transplantation of EF1a-transduced BM-HSCs led to much higher in vivo Ii expression. Thus, among those compared, dual-promoter vector-based lentivirus with the EF1a promoter driving the gene of interest is optimal for murine BM-HSC transduction.

The site of allergen expression in hematopoietic cells determines the degree and quality of tolerance induced through molecular chimerism

The transplantation of allergens (e.g. Phl p 5 or Bet v 1) expressed on BM cells as membrane-anchored full-length proteins leads to permanent tolerance at the T-cell, B-cell, and effector-cell levels. Since the exposure of complete allergens bears the risk of inducing anaphylaxis, we investigated here whether expression of Phl p 5 in the cytoplasm (rather than on the cell surface) is sufficient for tolerance induction. Transplantation of BALB/c BM retrovirally transduced to express Phl p 5 in the cytoplasm led to stable and durable molecular chimerism in syngeneic recipients (∼20% chimerism at 6 months). Chimeras showed allergen-specific T-cell hyporesponsiveness. Further, Phl p 5-specific TH 1-dependent humoral responses were tolerized in several chimeras. Surprisingly, Phl p 5-specific IgE and IgG1 levels were significantly reduced but still detectable in sera of chimeric mice, indicating incomplete B-cell tolerance. No Phl p 5-specific sIgM developed in cytoplasmic chimeras, which is in marked contrast to mice transplanted with BM expressing membrane-anchored Phl p 5. Thus, the expression site of the allergen substantially influences the degree and quality of tolerance achieved with molecular chimerism in IgE-mediated allergy.

Molecular chimerism in IgE-mediated allergy: B-and T-cell tolerance toward highly immunogenic exogenous antigens

Specific immunotherapy is the only curative treatment currently available for IgE-mediated allergy and preventive strategies are lacking altogether. We have recently reported that molecular chimerism induces durable tolerance in experimental models of allergy, thus potentially providing a new approach for the treatment and prevention of allergic diseases. Molecular chimerism is a gene-therapy approach for tolerance induction toward defined disease-causing antigens. In proof-of-concept studies, we introduced a clinically relevant grass pollen allergen into hematopoietic stem cells and transplanted those modified cells into preconditioned syngeneic mice. Long-lasting and robust tolerance toward the allergen was achieved. In our most recent studies published in Clinical and Experimental Allergy we demonstrated that milder, non-myeloablative conditioning is sufficient to induce tolerance. Our results revealed that, in contrast to other rodent models of chimerism, persistent microchimerism suffices to induce lasting tolerance at the T cell, B cell and effector cell levels in IgE-mediated allergy. This article addendum provides a summary of the recent paper and its implications.

Tolerance induction with gene-modified stem cells and immune-preserving conditioning in primed mice: restricting antigen to differentiated antigen-presenting cells permits efficacy

Bone marrow (BM) or hematopoietic stem cell (HSC) transplantation is used as curative therapy for hematologic malignancies. Incorporation of gene therapy to drive tolerogenic expression of antigens is a promising strategy to overcome the limited long-term efficacy of autologous HSC transplantation for autoimmune diseases. HSC engraftment and tolerance induction is readily achieved after myeloablative or immune-depleting conditioning regardless of the cellular compartment in which antigen is expressed. It is unclear whether the efficiency of engraftment and tolerance induction is influenced by targeting antigen to specific cellular compartments. This is particularly important when using clinically feasible low-intensity conditioning aimed at preserving infectious immunity in individuals where immunologic memory exists to the autoantigen to be expressed. Here we demonstrate that, under immune-preserving conditions, confining expression of a transgenically expressed antigen to dendritic cells permits stable, long-term engraftment of genetically modified BM even when recipients are immune to the expressed antigen. In contrast, broader expression within the hematopoietic compartment leads to graft rejection and therapeutic failure because of antigen expression in HSCs. These findings are relevant to the clinical application of genetically engineered HSCs and provide evidence that careful selection of promoters for HSC-mediated gene therapy is important, particularly where tolerance is sought under immune-preserving conditions.

Induction of antigen-specific tolerance through hematopoietic stem cell-mediated gene therapy: the future for therapy of autoimmune disease?

Based on the principle that immune ablation followed by HSC-mediated recovery purges disease-causing leukocytes to interrupt autoimmune disease progression, hematopoietic stem cell transplantation (HSCT) has been increasingly used as a treatment for severe autoimmune diseases. Despite clinically-relevant outcomes, HSCT is associated with serious iatrogenic risks and is suitable only for the most serious and intractable diseases. A further limitation of autologous HSCT is that relapse rates can be high, suggesting disease-causing leukocytes are incompletely purged or the environmental and genetic determinants that drive disease remain active. Incorporation of antigen-specific tolerance approaches that synergise with autologous HSCT could reduce or prevent relapse. Further, by reducing the requirement for highly toxic immune-ablation and instead relying on antigen-specific tolerance, the clinical utility of HSCT could be significantly diversified. Substantial progress has been made exploring HSCT-mediated induction of antigen-specific tolerance in animal models but studies have focussed on primarily on prevention of autoimmune diseases. However, as diagnosis of autoimmune disease is often not made until autoimmune disease is well developed and populations of autoantigen-specific pathogenic effector and memory T cells have become well established, immunotherapies must be developed to address effector and memory T-cell responses which have traditionally been considered the key impediment to immunotherapy. Here, focusing on T-cell mediated autoimmune diseases we review progress made in antigen-specific immunotherapy using HSCT-mediated approaches, induction of tolerance in effector and memory T cells and the challenges for progression and clinical application of antigen-specific 'tolerogenic' HSCT therapy.

Nonmyeloablative conditioning generates autoantigen-encoding bone marrow that prevents and cures an experimental autoimmune disease

Autoimmune diseases result from chronic targeted immune responses that lead to tissue pathology and disease. The potential of autologous hematopoietic stem cells transplantation as a treatment for autoimmunity is currently being trialled but disease relapse is an issue. We have previously shown in a mouse model of experimental autoimmune encephalomyelitis (EAE) that the transplantation of bone marrow (BM) transduced to encode the autoantigen myelin oligodendrocyte glycoprotein (MOG) can prevent disease induction. However these studies were performed using lethal irradiation to generate BM chimeras and a critical factor for translation to humans would be the ability to utilize low toxic preconditioning regimes. In this study, treosulfan was used as a nonmyeloablative agent to generate BM chimeras encoding MOG and assessed in models of EAE induction and reversal. We find that treosulfan conditioning can promote a low degree of chimerism that is sufficient to promote antigen specific tolerance and protect mice from EAE. When incorporated into a curative protocol for treating mice with established EAE, nonmyeloablative conditioning and low chimerism was equally efficient in maintaining disease resistance. These studies further underpin the potential and feasibility of utilizing a gene therapy approach to treat autoimmune disease.

Tolerance to MHC class II disparate allografts through genetic modification of bone marrow

Induction of molecular chimerism through genetic modification of bone marrow is a powerful tool for the induction of tolerance. Here we demonstrate for the first time that expression of an allogeneic MHC class II gene in autologous bone marrow cells, resulting in a state of molecular chimerism, induces tolerance to MHC class II mismatched skin grafts, a stringent test of transplant tolerance. Reconstitution of recipients with syngeneic bone marrow transduced with retrovirus encoding H-2I-A^b (I-A^b) resulted the long-term expression of the retroviral gene product on the surface of MHC class II-expressing bone marrow derived cell types. Mechanistically, tolerance was maintained by the presence of regulatory T cells, which prevented proliferation and cytokine production by alloreactive host T cells. Thus, the introduction of MHC class II genes into bone marrow derived cells through genetic engineering results in tolerance. These results have the potential to extend the clinical applicability of molecular chimerism for tolerance induction.

Tackling autoimmunity with gene therapy

Autoimmune diseases result from an aberrant response of the immune system that target self-tissues. Our understanding of normal immune development has been used to subvert this self-reactivity and involves exposing self-antigen to the developing immune system. This can be achieved through bone marrow derived cells, thus introducing potential clinical application. We have used the mouse model of multiple sclerosis to demonstrate that the transfer of bone marrow encoding a target autoantigen can be used to promote immune tolerance. The process of preconditioning recipients for hematopoietic stem cell transfer is critical for potential human translation. Thus, we have directly addressed if our model can also be applied in non-myeloablative and less toxic conditioning to promote tolerance and reverse established disease. Our studies to date indicate that this can indeed be achieved and that only low levels of chimerism are required to achieve tolerance.

Essential roles of insulin expression in Aire+ tolerogenic dendritic cells in maintaining peripheral self-tolerance of islet β-cells

Anti-insulin autoimmunity is one of the primary forces in initiating and progressing β-cell destruction in type 1 diabetes. While insulin expression in thymic medullary epithelial cells has been shown to be essential for establishing β-cell central tolerance, the function of insulin expression in antigen-presenting cells (APCs) of hematopoietic lineage remains elusive. With a Cre-lox reporter approach, we labeled Aire-expressing cells with enhanced yellow fluorescent proteins, and found that insulin expression in the spleen was restricted predominantly to a population of Aire(+)CD11c(int)B220(+) dendritic cells (DCs). Targeted insulin deletion in APCs failed to induce anti-islet autoimmunity in B6 mice. In contrast, elevated levels of T cell infiltration into islets were observed in B6(g7) congenic mice when insulin was specifically deleted in their CD11c-expressing DCs (B6(g7)·CD11c-ΔIns mice). Thus, insulin expression in BM-derived, Aire(+) tolerogenic DCs may play an essential role to prevent the activation and expansion of insulin-reactive T cells in the periphery.

100 years of hyposensitization: history of allergen-specific immunotherapy (ASIT)

Hundred years ago, Leonhard Noon and John Freeman published their pioneering works on allergen-specific immunotherapy (ASIT) using grass pollen extracts. To honor their contribution to the development of ASIT as the only causal treatment of IgE-mediated allergies, we review the history of ASIT that started with the anecdotal descriptions of ASIT performed by the ancient king Mithridates (132-63 B.C.) and Jenner's development of a cowpox vaccine. Following Noon's and Freeman's first controlled human trials, ASIT was performed by a large number of modalities and with a myriad of pharmacologic preparations. These developments range from early aqueous pollen extracts and whole bee extracts to chemically modified allergens (allergoids) and various recombinant allergens. In addition to allergen-specific immunotherapy, non-specific immune response modifiers have been used in the past or are in the developmental stage. Also, currently many innovative experimental approaches of ASIT are studied in animal models and human in vitro systems and will hopefully further broaden the range of allergies that can be treated by ASIT, with enhanced efficacy and further reduced side-effects.

Breaking T cell tolerance to beta cell antigens by merocytic dendritic cells

In type 1 diabetes (T1D), a break in central and peripheral tolerance results in antigen-specific T cells destroying insulin-producing, pancreatic beta cells. Herein, we discuss the critical sub-population of dendritic cells responsible for mediating both the cross-presentation of islet antigen to CD8(+) T cells and the direct presentation of beta cell antigen to CD4(+) T cells. These cells, termed merocytic dendritic cells (mcDC), are more numerous in non-obese diabetic (NOD), and antigen-loaded mcDC rescue CD8(+) T cells from peripheral anergy and deletion, and stimulate islet-reactive CD4(+) T cells. When purified from the pancreatic lymph nodes of overtly diabetic NOD mice, mcDC can break peripheral T cell tolerance to beta cell antigens in vivo and induce rapid onset T cell-mediated T1D in young NOD mouse. Thus, the mcDC subset appears to represent the long-sought critical antigen-presenting cell responsible for breaking peripheral tolerance to beta cell antigen in vivo.

Targeting the CXCR4-CXCL12 axis mobilizes autologous hematopoietic stem cells and prolongs islet allograft survival via programmed death ligand 1

Antagonism of CXCR4 disrupts the interaction between the CXCR4 receptor on hematopoietic stem cells (HSCs) and the CXCL12 expressed by stromal cells in the bone marrow, which subsequently results in the shedding of HSCs to the periphery. Because of their profound immunomodulatory effects, HSCs have emerged as a promising therapeutic strategy for autoimmune disorders. We sought to investigate the immunomodulatory role of mobilized autologous HSCs, via target of the CXCR4-CXL12 axis, to promote engraftment of islet cell transplantation. Islets from BALB/c mice were transplanted beneath the kidney capsule of hyperglycemic C57BL/6 mice, and treatment of recipients with CXCR4 antagonist resulted in mobilization of HSCs and in prolongation of islet graft survival. Addition of rapamycin to anti-CXCR4 therapy further promoted HSC mobilization and islet allograft survival, inducing a robust and transferable host hyporesponsiveness, while administration of an ACK2 (anti-CD117) mAb halted CXCR4 antagonist-mediated HSC release and restored allograft rejection. Mobilized HSCs were shown to express high levels of the negative costimulatory molecule programmed death ligand 1 (PD-L1), and HSCs extracted from wild-type mice, but not from PD-L1 knockout mice, suppressed the in vitro alloimmune response. Moreover, HSC mobilization in PD-L1 knockout mice failed to prolong islet allograft survival. Targeting the CXCR4-CXCL12 axis thus mobilizes autologous HSCs and promotes long-term survival of islet allografts via a PD-L1-mediated mechanism.

[Antitumor effects of raddeanin A on S180, H22 and U14 cell xenografts in mice]

BACKGROUND & OBJECTIVE

Raddeanin A, a triterpenoid saponin from Anemone raddeana Regel, has good antitumor activity in vitro. This study was to investigate its antitumor effects on tumor cell xenografts in mice.

METHODS

The inhibitory effects of raddeanin A on the proliferation of human nasopharyngeal carcinoma KB cells and ovarian cancer SKOV3 cells were measured by MTT assay. The inhibitory effects of raddeanin A injection on the growth of sarcoma S180, liver cancer H22 and cervical carcinoma U14 cell xenografts in mice and the effect of raddeanin A lavage on the growth of S180 cell xenografts were measured. The acute toxicity of raddeanin A was also measured.

RESULTS

The 50% inhibition concentration (IC(50)) of raddeanin A was 4.64 microg/mL for KB cells and 1.40 microg/mL for SKOV3 cells. When injected with raddeanin A at a dose of 4.5 mg/kg, the growth inhibition rates of S180, H22 and U14 cell xenografts were 60.5%, 36.2% and 61.8%, respectively. When lavaged with raddeanin A at a dose of 200 mg/kg, the growth inhibition rate of S180 cell xenografts was 64.7%. The median lethal dose (LD50) of raddeanin A lavage was 1.1 g/kg and that of raddeanin A injection was 16.1 mg/kg.

CONCLUSION

Raddeanin A has good antitumor activity both in vitro and in vivo, and would be a potential antitumor medicine.

Recent insights into CD4+ T-cell specificity and function in type 1 diabetes

Type 1 diabetes (T1D) is caused by T-cell-mediated destruction of the insulin-producing beta-cells in the pancreas. Genetic and immunological evidence from humans and mouse models indicates that CD4(+) T cells play a crucial role in the development and prevention of T1D. The dichotomy between CD4(+) T regulatory and effector T cells has encouraged research into the role of these cell subsets in T1D. New antigens and epitopes recognized by CD4(+) T cells in affected individuals have been identified. Growing knowledge of T-cell specificity and function is helping to develop new assays for analyzing islet antigen-specific CD4(+) T cells from human blood. Here we discuss, with particular reference to human studies, advances in our understanding of CD4(+) T-cell responses in T1D.

The immunotherapeutic potential of dendritic cells in type 1 diabetes

Type 1 diabetes is an autoimmune disease characterized by destruction of the pancreatic islet beta cells that is mediated primarily by T cells specific for beta cell antigens. Insulin administration prolongs the life of affected individuals, but often fails to prevent the serious complications that decrease quality of life and result in significant morbidity and mortality. Thus, new strategies for the prevention and treatment of this disease are warranted. Given the important role of dendritic cells (DCs) in the establishment of peripheral T cell tolerance, DC-based strategies are a rational and exciting avenue of exploration. DCs employ a diverse arsenal to maintain tolerance, including the induction of T cell deletion or anergy and the generation and expansion of regulatory T cell populations. Here we review DC-based immunotherapeutic approaches to type 1 diabetes, most of which have been employed in non-obese diabetic (NOD) mice or other murine models of the disease. These strategies include administration of in vitro-generated DCs, deliberate exposure of DCs to antigens before transfer and the targeting of antigens to DCs in vivo. Although remarkable results have often been obtained in these model systems, the challenge now is to translate DC-based immunotherapeutic strategies to humans, while at the same time minimizing the potential for global immunosuppression or exacerbation of autoimmune responses. In this review, we have devoted considerable attention to antigen-specific DC-based approaches, as results from murine models suggest that they have the potential to result in regulatory T cell populations capable of both preventing and reversing type 1 diabetes.

From allergen genes to allergy vaccines

IgE-mediated allergy is a hypersensitivity disease affecting more than 25% of the population. The structures of the most common allergens have been revealed through molecular cloning technology in the past two decades. On the basis of this knowledge of the sequences and three-dimensional structures of culprit allergens, investigators can now analyze the immune recognition of allergens and the mechanisms of allergic inflammation in allergic patients. Allergy vaccines have been constructed that are able to selectively target the aberrant immune responses in allergic patients via different pathways of the immune system. Here we review various types of allergy vaccines that have been developed based on allergen structures, results from their clinical application in allergic patients, and future strategies for allergen-specific immunotherapy and allergy prophylaxis.

Insulin2 gene (Ins2) transcription by NOD bone marrow-derived cells does not influence autoimmune diabetes development in NOD-Ins2 knockout mice

Insulin is a critical autoantigen for the development of autoimmune diabetes in non-obese diabetic (NOD) mice. About 80% of NOD females and 30-40% of NOD males develop diabetes. However, Insulin2 (Ins2) knockout NOD mice develop autoimmune diabetes with complete penetrance in both sexes, at an earlier age, and have stronger autoimmune responses to insulin. The severe diabetes phenotype observed in NOD-Ins2-/- mice suggests that lack of Ins2 expression in the thymus may compromise immunological tolerance to insulin. Insulin is a prototypical tissue specific antigen (TSA) for which tolerance is dependent on expression in thymus and peripheral lymphoid tissues. TSA are naturally expressed by medullary thymic epithelial cells (mTEC), stromal cells in peripheral lymphoid tissues and bone marrow (BM)-derived cells, mainly CD11c(+) dendritic cells. The natural expression of TSA by mTEC and stromal cells has been shown to contribute to self-tolerance. However, it is unclear whether this also applies to BM-derived cells naturally expressing TSA. To address this question, we created BM chimeras and investigated whether reintroducing Ins2 expression solely by NOD BM-derived cells delays diabetes development in NOD-Ins2-/- mice. On follow-up, NOD-Ins2-/- mice receiving Ins2-expressing NOD BM cells developed diabetes at similar rates of those receiving NOD-Ins2-/- BM cells. Diabetes developed in 64% of NOD recipients transplanted with NOD BM and in 47% of NOD mice transplanted with NOD-Ins2-/- BM (P = ns). Thus, NOD-Ins2-/- BM did not worsen diabetes in NOD recipients and Ins2 expression by NOD BM-derived cells did not delay diabetes development in NOD-Ins2-/- mice.

Gene therapy and bone marrow stem-cell transfer to treat autoimmune disease

Current treatment of human autoimmune disease by autologous bone marrow stem-cell transfer is hampered by frequent disease relapses. This is most probably owing to re-emergent self-reactive lymphocytes. Gene therapy combined with bone marrow stem cells has successfully introduced genes lacking in immunodeficiences. Because the bone marrow compartment has a key role in establishing immune tolerance, this combination strategy should offer a rational approach to prevent re-emergent self-reactive lymphocytes by establishing solid, life-long immune tolerance to causative self-antigen. Indeed, we have recently demonstrated the success of this combination approach to prevent and cure an experimental autoimmune disease. We suggest that this combination strategy has the potential for translation to treat human autoimmune diseases in which causative self-antigens are known.

Reversing the Autoimmune Condition: Experience with Experimental Autoimmune Gastritis

Autoimmune diseases remain a significant health problem in our society, despite the best efforts to understand and treat these conditions. Current clinical treatments are aimed at alleviating the consequences of these diseases, with limited prospects for cure. Our studies with the experimental model of autoimmune gastritis have led us to explore potential curative strategies that can reverse the autoimmune condition. Using mouse models, we have shown that expression of the known gastric autoantigen in the thymus results in immunological tolerance and resistance to the induction of autoimmune gastritis. Also, induced tolerance in donor mice can be transferred to syngeneic recipient mice by bone marrow cells. Strategies based on these observations could lead to reversal of established disease. Transfer of ensuing knowledge to the cure of serious human autoimmune diseases is our ultimate goal.

Tolerance induction in experimental autoimmune encephalomyelitis using non-myeloablative hematopoietic gene therapy with autoantigen

Experimental autoimmune encephalomyelitis (EAE) constitutes a paradigm of antigen (Ag)-specific T cell driven autoimmune diseases. In this study, we transferred bone marrow cells (BMCs) expressing an autoantigen (autoAg), the peptide 40-55 of the myelin oligodendrocytic glycoprotein (MOG(40-55)), to induce preventive and therapeutic immune tolerance in a murine EAE model. Transfer of BMC expressing MOG(40-55) (IiMOG-BMC) into partially myeloablated mice resulted in molecular chimerism and in robust protection from the experimental disease. In addition, in mice with established EAE, transfer of transduced BMC with or without partial myeloablation reduced the clinical and histopathological severity of the disease. In these experiments, improvement was observed even in the absence of engraftment of the transduced hematopoietic cells, probably rejected due to the previous immunization with the autoAg. Splenocytes from mice transplanted with IiMOG-BMC produced significantly higher amounts of interleukin (IL)-5 and IL-10 upon autoAg challenge than those of control animals, suggesting the participation of regulatory cells. Altogether, these results suggest that different tolerogenic mechanisms may be mediating the preventive and the therapeutic effects. In conclusion, this study demonstrates that a cell therapy using BMC expressing an autoAg can induce Ag-specific tolerance and ameliorate established EAE even in a nonmyeloablative setting.

Tolerization of a type I allergic immune response through transplantation of genetically modified hematopoietic stem cells

Allergy represents a hypersensitivity disease that affects >25% of the population in industrialized countries. The underlying type I allergic immune reaction occurs in predisposed atopic individuals in response to otherwise harmless Ags (i.e., allergens) and is characterized by the production of allergen-specific IgE, an allergen-specific T cell response, and the release of biologically active mediators such as histamine from mast cells and basophils. Regimens permanently tolerizing an allergic immune response still need to be developed. We therefore retrovirally transduced murine hematopoietic stem cells to express the major grass pollen allergen Phl p 5 on their cell membrane. Transplantation of these genetically modified hematopoietic stem cells led to durable multilineage molecular chimerism and permanent immunological tolerance toward the introduced allergen at the B cell, T cell, and effector cell levels. Notably, Phl p 5-specific serum IgE and IgG remained undetectable, and T cell nonresponsiveness persisted throughout follow-up (40 wk). Besides, mediator release was specifically absent in in vitro and in vivo assays. B cell, T cell, and effector cell responses to an unrelated control allergen (Bet v 1) were unperturbed, demonstrating specificity of this tolerance protocol. We thus describe a novel cell-based strategy for the prevention of allergy.

Cellular therapies for type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a disease that results from the selective autoimmune destruction of insulin-producing beta-cells. This disease process lends itself to cellular therapy because of the single cell nature of insulin production. Murine models have provided opportunities for the study of cellular therapies for the treatment of diabetes, including the investigation of islet transplantation, and also the possibility of stem cell therapies and islet regeneration. Studies in islet transplantation have included both allo- and xeno-transplantation and have allowed for the study of new approaches for the reversal of autoimmunity and achieving immune tolerance. Stem cells from hematopoietic sources such as bone marrow and fetal cord blood, as well as from the pancreas, intestine, liver, and spleen promise either new sources of islets or may function as stimulators of islet regeneration. This review will summarize the various cellular interventions investigated as potential treatments of T1DM.

Vaccination against self to prevent autoimmune disease: the type 1 diabetes model

Immune tolerance to self-antigens is physiological. Given a repertoire of self-reactive, potentially pathogenic lymphocytes, therapeutic options to diminish autoimmune disease risk include deletion, reduced activation or increased regulation of self-reactive lymphocytes by means that mimic or promote physiological mechanisms of immunity. Vaccination with self-antigen to promote self-antigen-specific tolerance, 'negative vaccination', may represent the most specific and potentially safest means of averting autoimmune disease. This strategy is therapeutically effective in inbred rodent models but its translation in humans has failed to meet expectations. This failure can be attributed to the use of suboptimal dosage regimens in end-stage disease, as well as other factors. This review focuses on vaccination against self-antigen in type 1 diabetes, an autoimmune disease unique in that individuals at risk can be identified years before clinical presentation. Moreover, the spontaneously diabetic non-obese diabetic mouse, which mimics human type 1 diabetes in many ways, has provided 'proof-of-concept' for negative vaccination. Recent trials of a nasal insulin vaccine in humans at risk of type 1 diabetes provide evidence of tolerance induction as a basis for clinical efficacy.

Steady-state dendritic cells expressing cognate antigen terminate memory CD8+ T-cell responses

Antigen stimulation of naive T cells in conjunction with strong costimulatory signals elicits the generation of effector and memory populations. Such terminal differentiation transforms naive T cells capable of differentiating along several terminal pathways in response to pertinent environmental cues into cells that have lost developmental plasticity and exhibit heightened responsiveness. Because these cells exhibit little or no need for the strong costimulatory signals required for full activation of naive T cells, it is generally considered memory and effector T cells are released from the capacity to be inactivated. Here, we show that steady-state dendritic cells constitutively presenting an endogenously expressed antigen inactivate fully differentiated memory and effector CD8(+) T cells in vivo through deletion and inactivation. These findings indicate that fully differentiated effector and memory T cells exhibit a previously unappreciated level of plasticity and provide insight into how memory and effector T-cell populations may be regulated.

Responses against islet antigens in NOD mice are prevented by tolerance to proinsulin but not IGRP

Type 1 diabetes (T1D) is characterized by immune responses against several autoantigens expressed in pancreatic beta cells. T cells specific for proinsulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) can induce T1D in NOD mice. However, whether immune responses to multiple autoantigens are caused by spreading from one to another or whether they develop independently of each other is unknown. As cytotoxic T cells specific for IGRP were not detected in transgenic NOD mice tolerant to proinsulin, we determined that immune responses against proinsulin are necessary for IGRP-specific T cells to develop. On the other hand, transgenic overexpression of IGRP resulted in loss of intra-islet IGRP-specific T cells but did not protect NOD mice from insulitis or T1D, providing direct evidence that the response against IGRP is downstream of the response to proinsulin. Our results suggest that pathogenic proinsulin-specific immunity in NOD mice subsequently spreads to other antigens such as IGRP.

Transplantation of bone marrow genetically engineered to express proinsulin II protects against autoimmune insulitis in NOD mice

BACKGROUND

Type 1 diabetes (T1D) is a T-cell-dependent autoimmune disease resulting from destructive inflammation (insulitis) of the insulin-producing pancreatic beta-cells. Transgenic expression of proinsulin II by a MHC class II promoter or transfer of bone marrow from these transgenic mice protects NOD mice from insulitis and diabetes. We assessed the feasibility of gene therapy in the NOD mouse as an approach to treat T1D by ex vivo genetic manipulation of normal hematopoietic stem cells (HSCs) with proinsulin II followed by transfer to recipient mice.

METHODS

HSCs were isolated from 6-8-week-old NOD female mice and transduced in vitro with retrovirus encoding enhanced green fluorescent protein (EGFP) and either proinsulin II or control autoantigen. Additional control groups included mice transferred with non-manipulated bone marrow and mice which did not receive bone marrow transfer. EGFP-sorted or non-sorted HSCs were transferred into pre-conditioned 3-4-week-old female NOD mice and insulitis was assessed 8 weeks post-transfer.

RESULTS

Chimerism was established in all major lymphoid tissues, ranging from 5-15% in non-sorted bone marrow transplants to 20-45% in EGFP-sorted bone marrow transplants. The incidence and degree of insulitis was significantly reduced in mice receiving proinsulin II bone marrow compared to controls. However, the incidence of sialitis in mice receiving proinsulin II bone marrow and control mice was not altered, indicating protection from insulitis was antigen specific.

CONCLUSIONS

We show for the first time that ex vivo genetic manipulation of HSCs to express proinsulin II followed by transplantation to NOD mice can establish molecular chimerism and protect from destructive insulitis in an antigen-specific manner.

Jagged2-expressing hematopoietic progenitors promote regulatory T cell expansion in the periphery through notch signaling

Cellular interactions promoting the in vivo expansion of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells for maintenance of immune tolerance remain poorly defined. Here we report that mobilized Lin(-)Sca-1(+)c-kit(+) (LSK) hematopoietic progenitor cells (HPCs), unlike medullary hematopoietic stem cells (HSCs), selectively drove the direct, immediate expansion of functional host-derived Treg cells, thereby preventing the progression to overt spontaneous autoimmune diabetes in nonobese diabetic mice. Treg cell expansion required cell-to-cell contact and Notch3 signaling, which was mediated selectively through the Notch ligand Jagged2 expressed by the multipotent HPC subset, as assessed by small interfering RNA (siRNA) silencing. Conversely, notwithstanding their similar multilineage microchimerism, neither sorted Jagged2(-) HPCs nor Jagged2(lo) medullary HSCs were able to expand Treg cells. These data provide evidence for a productive Notch-mediated interaction between a unique subset of mobilized hematopoietic progenitors and Treg cells. They open therapeutic perspectives for autologous transplantation of Jagged2(+) LSK progenitors to promote Treg cell expansion in T cell-mediated diseases.

Proinsulin is encoded by an RNA splice variant in human blood myeloid cells

Genes for peripheral tissue-restricted self-antigens are expressed in thymic and hematopoietic cells. In thymic medullary epithelial cells, self-antigen expression imposes selection on developing autoreactive T cells and regulates susceptibility to autoimmune disease in mouse models. Less is known about the role of self-antigen expression by hematopoietic cells. Here we demonstrate that one of the endocrine self-antigens expressed by human blood myeloid cells, proinsulin, is encoded by an RNA splice variant. The surface expression of immunoreactive proinsulin was significantly decreased after transfection of monocytes with small interfering RNA to proinsulin. Furthermore, analogous to proinsulin transcripts in the thymus, the abundance of the proinsulin RNA splice variant in blood cells corresponded with the length of the variable number of tandem repeats 5' of the proinsulin gene, known to be associated with type 1 diabetes susceptibility. Self-antigen expression by peripheral myeloid cells extends the umbrella of "immunological self" and, by analogy with the thymus, may be implicated in peripheral immune tolerance.

Rapid immune reconstitution and dendritic cell engraftment post–bone marrow transplantation with heterogeneous progenitors and GM-CSF treatment

OBJECTIVE

Bone marrow/hematopoietic stem cell transplantation (BMT) has been the treatment of choice for severe hematological diseases and cancers. Rapid host immune recovery following BMT is critical for reducing complications and improving therapeutic outcome. Here we report manipulations that facilitate rapid immune and dendritic cell (DC) reconstitution post-BMT for improvement in therapeutic outcome of BMT-based disease treatment.

METHODS

Using lentiviral vector-modified or unmodified murine hematopoietic stem cells, we examined the engraftment efficiency and kinetics in immune reconstitution of unfractionated bone marrow cells (BM), lineage marker-negative (Lin-) hematopoietic progenitor cells (HPC), or purified Lin-Sca-1+ hematopoietic stem cells (HSC) at an equal hematopoietic progenitor number.

RESULTS

Our study revealed that BM reconstituted host primary and secondary lymphoid tissues more efficiently and rapidly. Moreover, in a competitive BMT setting using lentiviral vector-engineered BM and HSC expressing GFP or DsRed respectively, we showed that GM-CSF treatment further enhanced DC reconstitution to therapeutic relevant level as early as 2 weeks post-BMT. On the other hand, Flt3 ligand was less effective in enhancing DC reconstitution till 3 weeks post-BMT. This accelerated DC engraftment by GM-CSF treatment correlated well with improved overall immune reconstitution and enhanced activation of antigen-specific T cells post-BMT.

CONCLUSION

This study suggests that use of heterogeneous BM for transplantation facilitates more rapid immune reconstitution, especially in the presence of DC-stimulating cytokines. This improved immune reconstitution would provide additional therapeutic benefits for BMT-based immunotherapy and gene therapy of genetic disorders and cancers.

Transgenic insulin (B:9-23) T-cell receptor mice develop autoimmune diabetes dependent upon RAG genotype, H-2g7 homozygosity, and insulin 2 gene knockout

A series of recent studies in humans and the NOD mouse model have highlighted the central role that autoimmunity directed against insulin, in particular the insulin B chain 9-23 peptide, may play in the pathogenesis of type 1 diabetes. Both pathogenic and protective T-cell clones recognizing the B:9-23 peptide have been produced. This report describes the successful creation of BDC12-4.1 T-cell receptor (TCR) transgenic mice with spontaneous insulitis in F1 mice (FVB x NOD) and spontaneous diabetes in NOD.RAG(-/-) (backcross 1 generation). Disease progression is heterogeneous and is modified by a series of genetic factors including heterozygosity (H-2(g7)/H-2(q)) versus homozygosity for H-2(g7), the presence of additional T-/B-cell receptor-rearranged genes (RAG(+) versus RAG(-/-)), and the insulin 2 gene knockout (the insulin gene expressed in the NOD thymus). Despite lymphopenia, 40% of H-2(g7/g7) BDC12-4.1 TCR(+) RAG(-/-) Ins2(-/-) mice are diabetic by 10 weeks of age. As few as 13,500 transgenic T-cells from a diabetic TCR(+) RAG(-/-) mouse can transfer diabetes to an NOD.scid mouse. The current study demonstrates that the BDC12-4.1 TCR is sufficient to cause diabetes at NOD backcross 1, bypassing polygenic inhibition of insulitis and diabetogenesis.