B-cells expressing NgR1 and NgR3 are localized to EAE-induced inflammatory infiltrates and are stimulated by BAFF

We have previously reported evidence that Nogo-A activation of Nogo-receptor 1 (NgR1) can drive axonal dystrophy during the neurological progression of experimental autoimmune encephalomyelitis (EAE). However, the B-cell activating factor (BAFF/BlyS) may also be an important ligand of NgR during neuroinflammation. In the current study we define that NgR1 and its homologs may contribute to immune cell signaling during EAE. Meningeal B-cells expressing NgR1 and NgR3 were identified within the lumbosacral spinal cords of ngr1^+/+ EAE-induced mice at clinical score 1. Furthermore, increased secretion of immunoglobulins that bound to central nervous system myelin were shown to be generated from isolated NgR1- and NgR3-expressing B-cells of ngr1^+/+ EAE-induced mice. In vitro BAFF stimulation of NgR1- and NgR3-expressing B cells, directed them into the cell cycle DNA synthesis phase. However, when we antagonized BAFF signaling by co-incubation with recombinant BAFF-R, NgR1-Fc, or NgR3 peptides, the B cells remained in the G0/G1 phase. The data suggest that B cells express NgR1 and NgR3 during EAE, being localized to infiltrates of the meninges and that their regulation is governed by BAFF signaling.

Tetraspanin CD53 Promotes Lymphocyte Recirculation by Stabilizing L-Selectin Surface Expression

Tetraspanins regulate key processes in immune cells; however, the function of the leukocyte-restricted tetraspanin CD53 is unknown. Here we show that CD53 is essential for lymphocyte recirculation. Lymph nodes of Cd53-/- mice were smaller than those of wild-type mice due to a marked reduction in B cells and a 50% decrease in T cells. This reduced cellularity reflected an inability of Cd53-/- B and T cells to efficiently home to lymph nodes, due to the near absence of L-selectin from Cd53-/- B cells and reduced stability of L-selectin on Cd53-/- T cells. Further analyses, including on human lymphocytes, showed that CD53 stabilizes L-selectin surface expression and may restrain L-selectin shedding via both ADAM17-dependent and ADAM17-independent mechanisms. The disruption in lymphocyte recirculation in Cd53-/- mice led to impaired immune responses dependent on antigen delivery to lymph nodes. Together these findings demonstrate an essential role for CD53 in lymphocyte trafficking and immunity.

The Influence of Differentially Expressed Tissue-Type Plasminogen Activator in Experimental Autoimmune Encephalomyelitis: Implications for Multiple Sclerosis

Tissue type plasminogen activator (t-PA) has been implicated in the development of multiple sclerosis (MS) and in rodent models of experimental autoimmune encephalomyelitis (EAE). We show that levels of t-PA mRNA and activity are increased ~4 fold in the spinal cords of wild-type mice that are mice subjected to EAE. This was also accompanied with a significant increase in the levels of pro-matrix metalloproteinase 9 (pro-MMP-9) and an influx of fibrinogen. We next compared EAE severity in wild-type mice, t-PA^-/- mice and T4+ transgenic mice that selectively over-express (~14-fold) mouse t-PA in neurons of the central nervous system. Our results confirm that t-PA deficient mice have an earlier onset and more severe form of EAE. T4+ mice, despite expressing higher levels of endogenous t-PA, manifested a similar rate of onset and neurological severity of EAE. Levels of proMMP-9, and extravasated fibrinogen in spinal cord extracts were increased in mice following EAE onset regardless of the absence or over-expression of t-PA wild-type. Interestingly, MMP-2 levels also increased in spinal cord extracts of T4+ mice following EAE, but not in the other genotypes. Hence, while the absence of t-PA confers a more deleterious form of EAE, neuronal over-expression of t-PA does not overtly protect against this condition with regards to symptom onset or severity of EAE.

Gene therapy delivery of myelin oligodendrocyte glycoprotein (MOG) via hematopoietic stem cell transfer induces MOG-specific B cell deletion

The various mechanisms that have been described for immune tolerance govern our ability to control self-reactivity and minimize autoimmunity. However, the capacity to genetically manipulate the immune system provides a powerful avenue to supplement this natural tolerance in an Ag-specific manner. We have previously shown in the mouse model of experimental autoimmune encephalomyelitis that transfer of bone marrow (BM) transduced with retrovirus encoding myelin oligodendrocyte glycoprotein (MOG) promotes disease resistance and CD4(+) T cell deletion within the thymus. However, the consequence of this strategy on B cell tolerance is not known. Using BM from IgH(MOG) mice that develop MOG-specific B cell receptors, we generated mixed chimeras together with BM-encoding MOG. In these animals, the development of MOG-specific B cells was abrogated, resulting in a lack of MOG-specific B cells in all B cell compartments examined. This finding adds a further dimension to our understanding of the mechanisms of tolerance that are associated with this gene therapy approach to treating autoimmunity and may have important implications for Ab-mediated autoimmune disorders.

Cutting edge issues in autoimmune gastritis

Autoimmune gastritis is the outcome of a pathological CD4 T cell-mediated autoimmune response directed against the gastric H/K-ATPase. Silent initially, the gastric lesion becomes manifest in humans by the development of megaloblastic pernicious anemia arising from vitamin B12 deficiency. Cutting edge issues in this disease relate to its epidemiology, immunogenetics, a role for Helicobacter pylori as an infective trigger through molecular mimicry, its immunopathogenesis, associated organ-specific autoimmune diseases, laboratory diagnosis, and approaches to curative 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.

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.

Thymic gene transfer of myelin oligodendrocyte glycoprotein ameliorates the onset but not the progression of autoimmune demyelination

Tolerance induction, and thus prevention of autoimmunity, is linked with the amount of self-antigen presented on thymic stroma. We describe that intrathymic (i.t.) delivery of the autoantigen, myelin oligodendrocyte glycoprotein (MOG), via a lentiviral vector (LV), led to tolerance induction and prevented mice from developing fulminant experimental autoimmune encephalomyelitis (EAE). This protective effect was associated with the long-term expression of antigen in transduced stromal cells, which resulted in the negative selection of MOG-specific T cells and the generation of regulatory T cells (Tregs). These selection events were effective at decreasing T-cell proliferative responses and reduced Th1 and Th17 cytokines. In vivo, this translated to a reduction in inflammation and demyelination with minimal, or no axonal loss in the spinal cords of treated animals. Significantly intrathymic delivery of MOG to mice during the priming phase of the disease failed to suppress clinical symptoms despite mice being previously treated with a clearing anti-CD4 antibody. These results indicate that targeting autoantigens to the thymic stroma might offer an alternative means to induce the de novo production of tolerant, antigen-specific T cells; however, methods that control the number and or the activation of residual autoreactive cells in the periphery are required to successfully treat autoimmune neuroinflammation.

Transplantation of autoimmune regulator-encoding bone marrow cells delays the onset of experimental autoimmune encephalomyelitis

The autoimmune regulator (AIRE) promotes "promiscuous" expression of tissue-restricted antigens (TRA) in thymic medullary epithelial cells to facilitate thymic deletion of autoreactive T-cells. Here, we show that AIRE-deficient mice showed an earlier development of myelin oligonucleotide glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). To determine the outcome of ectopic Aire expression, we used a retroviral transduction system to over-express Aire in vitro, in cell lines and in bone marrow (BM). In the cell lines that included those of thymic medullary and dendritic cell origin, ectopically expressed Aire variably promoted expression of TRA including Mog and Ins2 (proII) autoantigens associated, respectively, with the autoimmune diseases multiple sclerosis and type 1 diabetes. BM chimeras generated from BM transduced with a retrovirus encoding Aire displayed elevated levels of Mog and Ins2 expression in thymus and spleen. Following induction of EAE with MOG(35-55), transplanted mice displayed significant delay in the onset of EAE compared with control mice. To our knowledge, this is the first example showing that in vivo ectopic expression of AIRE can modulate TRA expression and alter autoimmune disease development.

Targeting MOG expression to dendritic cells delays onset of experimental autoimmune disease

Haematopoietic stem cell (HSC) transfer coupled with gene therapy is a powerful approach to treating fatal diseases such as X-linked severe combined immunodeficiency. This ability to isolate and genetically manipulate HSCs also offers a strategy for inducing immune tolerance through ectopic expression of autoantigens. We have previously shown that retroviral transduction of bone marrow (BM) with vectors encoding the autoantigen, myelin oligodendrocyte glycoprotein (MOG), can prevent the induction of experimental autoimmune encephalomyelitis (EAE). However, ubiquitous cellular expression of autoantigen driven by retroviral promoters may not be the best approach for clinical translation and a targeted expression approach may be more acceptable. As BM-derived dendritic cells (DCs) play a major role in tolerance induction, we asked whether targeted expression of MOG, a target autoantigen in EAE, to DCs can promote tolerance induction and influence the development of EAE. Self-inactivating retroviral vectors incorporating the mouse CD11c promoter were generated and used to transduce mouse BM cells. Transplantation of gene-modified cells into irradiated recipients resulted in the generation of chimeric mice with transgene expression limited to DCs. Notably, chimeric mice transplanted with MOG-expressing BM cells manifest a significant delay in the development of EAE suggesting that targeted antigen expression to tolerogenic cell types may be a feasible approach to inducing antigen-specific tolerance.

A molecular Trojan horse: hijacking the bone marrow to treat autoimmune diseases

Autoimmune diseases such as multiple sclerosis, type 1 diabetes, systemic sclerosis, and rheumatoid arthritis affect approximately 5% of the population and are characterized by a destructive immune response directed to self-tissues. Treatments are often designed to dampen the immune system and are therefore associated with unwanted side effects. A major challenge is to find a cure that does not compromise normal immune function. From our understanding of how the immune system develops, it is clear that mechanisms designed to eliminate or maintain control over self-reactive clones are critical for normal health. These key concepts form the crux of many experimental strategies currently aimed at abrogating the autoimmune response. In this review, we focus on the strategy of harnessing the bone marrow compartment through genetic manipulation directed at promoting ectopic autoantigen expression. Our experience with this strategy is presented in the context of reports in the literature and we argue for the potential benefit of translating this approach to the treatment of human autoimmune disease.

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.

Mechanisms of Gastric Mucosal Cell Loss In Autoimmune Gastritis

The causes of target cell death in organ-specific autoimmune diseases are not precisely known. In the case of EAG, parietal cell death depends on Th1 CD4 T cells and Fas/Fas-ligand, either through interaction between infiltrating CD4 T cells with gastric parietal cells that have upregulated Fas expression or through homotypic interactions between the parietal cells. TNF-alpha does not appear to have a role in this process. The accompanying loss of zymogenic cells is likely a consequence of the interruption of the normal developmental pathway in the gastric mucosa that follows the destruction of parietal cells in the gastric mucosa.

Experimental Autoimmune Gastritis: Mouse Models Of Human Organ-specific Autoimmune Disease

Experimental autoimmune gastritis (EAG) is an excellent model of human autoimmune gastritis, the underlying cause of pernicious anaemia. Murine autoimmune gastritis replicates human gastritis in being characterized by a chronic inflammatory mononuclear cell infiltrate in the gastric mucosa, destruction of parietal and zymogenic cells, and autoantibodies to the alpha-and beta-subunits of the gastric H+/K+ ATPase. Disease is induced strain specifically in gastritis-susceptible BALB/c mice by methods with a greater variety than those for most other experimental autoimmune diseases. The disease is induced in the regional gastric lymph node in which pathogenic CD4+ T cells are recruited. The model provides an excellent illustration of regulation by CD4+CD25+T cells, and, indeed, the removal of such regulatory cells, e.g., by neonatal thymectomy, is thought to be a major mechanism by which disease can develop. The culprit T helper type 1 (Th1) CD4+ T cells recognize either the alpha- or beta-subunits of the gastric H+/K+ ATPase, but the beta-subunit appears to be the initiating autoantigen, while the alpha-subunit may have a role in perpetuating disease. Since no specific environmental modifiers are identifiable, the origins of the disease are intrinsic; this is illustrated by the capacity of a cytokine (GM-CSF)-dependent inflammatory stimulus in the stomach to initiate EAG, according to a transgenic model in which thymectomy is dispensible. Thus, EAG is an exquisite model for a reductionist analysis of the multiple elements that in combination induce autoimmunity in humans.

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.

Transplantation of bone marrow transduced to express self-antigen establishes deletional tolerance and permanently remits autoimmune disease

Autoimmune diseases are incurable. We have hypothesized that these diseases can be cured by the transplantation of bone marrow (BM) stem cells that have been genetically engineered to express self-Ag. Here we have tested this hypothesis in experimental autoimmune encephalomyelitis (EAE) induced by the self-Ag myelin oligodendrocyte glycoprotein (MOG). We show that, in mice, transplantation of BM genetically modified to express MOG prevented the induction and progression of EAE, and combined with antecedent corticosteroid treatment, induced long-term remission of established disease. Mice remained resistant to EAE development upon subsequent rechallenge with MOG. Transfer of BM from these mice rendered recipients resistant to EAE. Splenocytes from these mice failed to proliferate or produce IL-17, IFN-gamma, and GM-CSF in response to MOG(35-55) peptide stimulation and they failed to produce MOG autoantibody. Mechanistically, we demonstrated in vivo reduction in development of CD4(+) MOG(35-55)-specific thymocytes, indicative of clonal deletion with no evidence for selection of Ag-specific regulatory T cells. These findings validate our hypothesis that transplantation of genetically modified BM expressing disease-causative self-Ag provides a curative approach by clonal deletion of disease-causative self-reactive T cells.

Methylprednisolone induces reversible clinical and pathological remission and loss of lymphocyte reactivity to myelin oligodendrocyte glycoprotein in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of human multiple sclerosis (MS). EAE, induced by immunisation with myelin-associated autoantigens, is characterised by an inflammatory infiltrate in the central nervous system (CNS) associated with axonal degeneration, demyelination and damage. We have recently shown in an experimental mouse model of autoimmune gastritis that methylprednisolone treatment induces a reversible remission of gastritis with regeneration of the gastric mucosa. Here, we examined the effect of oral methylprednisolone on the mouse EAE model of human MS induced by immunisation with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)). We examined the clinical scores, CNS pathology and lymphocyte reactivity to MOG(35-55) following treatment and withdrawal of the steroid. Methylprednisolone remitted the clinical signs of EAE and the inflammatory infiltrate in the CNS, accompanied by loss of lymphocyte reactivity to MOG(35-55) peptide. Methylprednisolone withdrawal initiated relapse of the clinical features, a return of the CNS inflammatory infiltrate and lymphocyte reactivity to MOG(35-55) peptide. This is the first study to show that methylprednisolone induced a reversible remission in the clinical and pathological features of EAE in mice accompanied by loss of lymphocyte reactivity to the encephalitogen. This model will be useful for studies directed at a better understanding of mechanisms associated with steroid-induced disease remission, relapse and remyelination and also as an essential adjunct to an overall curative strategy.

GM-CSF-induced autoimmune gastritis in interferon alpha receptor deficient mice

Experimental autoimmune gastritis (EAG), a mouse model of human autoimmune gastritis, is characterised by gastric mononuclear cell infiltrates and parietal and zymogenic cell destruction. The gastritis is accompanied by circulating auto-antibodies to parietal cell-associated gastric H(+)/K(+) ATPase. As interferon alpha has been implicated in the regulation of immune responses, we asked whether EAG induced by the local transgenic expression of granulocyte-macrophage colony stimulating factor (GM-CSF) in the stomach (PC-GMCSF transgenic mice) would be affected by deficiency of its binding receptor. To address this, we crossed PC-GMCSF transgenic mice with mice deficient in interferon alpha (IFNalpha) receptor2 (IFNAR2). We found that EAG development in the PC-GMCSF transgenic mice was not affected by IFNAR2 deficiency. There was no difference in severity of gastric pathology, nor in autoantibody levels in the IFNAR2 deficient mice compared to wild-type, and heterozygous littermates. We conclude that the local transgenic expression of GM-CSF in the stomach overrides any possible modulatory effects of IFNAR2 on EAG development.

Haematopoietic stem cell gene therapy to treat autoimmune disease

Autoimmune diseases affect approximately 6% of the population and are characterised by a pathogenic immune response that targets self-antigens. Well known diseases of this nature include type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis. Treatment is often restricted to replacement therapy or immunosuppressive regimes and to date there are no cures. The strategy of utilising autologous or allogeneic haematopoietic stem cell transplantation to treat autoimmunity and induce immunological tolerance has been trailed with various levels of success. A major issue is disease relapse as the autoimmune response is reinitiated. Cells of the immune system originate from bone marrow and have a central role in the induction of immunological tolerance. The ability to isolate and genetically manipulate bone marrow haematopoietic stem cells therefore makes these cells a suitable vehicle for driving ectopic expression of defined autoantigens and induction of immunological tolerance.

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.

Gene Therapy Strategies Towards Immune Tolerance to Treat the Autoimmune Diseases

Autoimmune diseases such as type 1 diabetes and multiple sclerosis pose a significant health burden on our society. As a whole, autoimmune diseases affect approximately 6% of the population and are the third largest disease burden after heart disease and cancer. Such pathologic manifestations arise by way of damaging reactions of B-cell derived antibodies and/or T-cells to self-antigens and are triggered by genetic and environmental factors. Currently there is no known cure, with treatment restricted to toxic, long-term immunosuppressive regimes, replacement therapy and in intractable cases, transplantation of autologous or allogeneic haematopoietic stem cells. In experimental models of autoimmunity, gene therapeutic approaches have demonstrated promise in treating the autoimmune diseases. These include delivery of anti-inflammatory cytokines and exploitation of regulatory T cells. However, none of these approaches provide lasting, long-term benefit. We hypothesise that therapeutically transduced haematopoietic stem cells followed by transplantation is an alternative strategy to establish permanent immune tolerance that can not only prevent autoimmunity but also cure these diseases. Our approach is focused on directing autoimmune disease-specific autoantigen expression in the thymus by genetic manipulation of haematopoietic stem cells to establish molecular chimeras. Our hypothesis originates from experimental studies with a mouse model of experimental autoimmune gastritis (EAG) and more recently with the non-obese diabetic (NOD) mouse model for type 1 diabetes (T1D).

Prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis

A cardinal feature of organ-specific autoimmunity is destructive pathology in the target organ. In human and experimental models of autoimmune gastritis, mononuclear cell infiltration and cellular destruction in the gastric mucosa are disease hallmarks. Strategies to cure autoimmune disease must not only establish immunological tolerance to autoantigen, but also rid the organ of pathogenic autoreactive cells. The present study has assessed the effect of prednisolone treatment in clearing the inflammatory infiltrate in experimental autoimmune gastritis and in preventing disease relapse in athymic compared with euthymic mice. Experimental autoimmune gastritis was induced by neonatal thymectomy or by transgenic expression of GM-CSF (PC-GMCSF mice). Groups of mice were treated with prednisolone (10 mg/kg per day) for 10 weeks or with prednisolone for 10 weeks followed by 10 weeks without prednisolone. Stomachs were examined for gross morphological changes, and by histology and immunohistochemistry for composition of inflammatory infiltrate and gastric mucosal integrity. Autoantibody to gastric H+/K+ ATPase was determined by ELISA. Prednisolone promoted remission of gastritis in both mouse models of experimental autoimmune gastritis, evident by reduction in stomach size, clearing of gastric inflammatory infiltrate, and regeneration of the gastric mucosa. Prednisolone withdrawal resulted in disease relapse in all PC-GMCSF mice, whereas approximately 40% of neonatal thymectomy mice retained normal stomach morphology and remained free of gastric pathology. It is concluded that prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis. Prolonged remission of autoimmune gastritis in some athymic mice suggests a role for the thymus in disease relapse.

Induction of tolerance to self-antigens using genetically modified bone marrow cells

The challenge of finding a lasting cure for autoimmune disease(s) has not been met. Although the use of systemic anti-inflammatory agents still dominates the treatment of these diseases, there is a push towards developing novel and more specific strategies. In addressing autoimmunity, there is the intrinsic need to understand the mechanisms that lead to the development and maintenance of immunological tolerance to self-antigens. Experimental evidence has shown that directed antigen expression in the thymus can induce immunological tolerance to that antigen. This forms the cornerstone of one strategy directed towards the cure of autoimmunity. In this strategy, individuals with autoimmune disease are transplanted with bone marrow stem cells that have been genetically modified and in this way allow expression of the self-antigen in the thymus.

Tumor necrosis factor alpha is not implicated in the genesis of experimental autoimmune gastritis

Experimental autoimmune gastritis (EAG) characterised by mononuclear cell infiltrate, parietal and zymogenic cell destruction and circulating autoantibodies to gastric H(+)/K(+)ATPase is an animal model for human autoimmune gastritis, that leads to pernicious anaemia. We have previously shown that Fas has a role in initiating damage to target cells in EAG. Here we used three strategies to examine the role of TNFalpha in this disease. We administered neutralising anti-TNFalpha antibody either as a single injection or as twice weekly injections for 8 weeks to mice subjected to neonatal thymectomy-induced EAG. To address the role of apoptotic signals through TNFR1, TNFR1 deficient mice were either neonatally thymectomised or crossed to PC-GMCSF transgenic mice that spontaneously develop EAG. Neonatally thymectomised mice treated with anti-TNFalpha antibody developed destructive gastritis and autoantibodies to gastric H(+)/K(+)ATPase similar to control mice. Following either neonatal thymectomy or crossing to PC-GMCSF transgenic mice, TNFR1 deficient mice developed autoantibody-positive destructive gastritis at similar frequency compared with wild type and heterozygous littermates. Our observations that neutralisation of TNFalpha and absence of TNFR1 has no discernible effect on development of EAG suggest that TNFalpha is not required for mucosal cell damage or development of autoimmune gastritis. While blocking TNFalpha activity has therapeutic benefit in certain autoimmune diseases, this is not the case for EAG.

Chemokine receptor CCR5 is not required for development of experimental autoimmune gastritis

Experimental autoimmune gastritis (EAG) is a model of human autoimmune gastritis, the underlying cause of pernicious anaemia. It is characterised by gastric mononuclear cell infiltrates, destruction of parietal and zymogenic cells, and autoantibodies to parietal cell-associated H(+)/K(+) ATPase. Here, we have investigated the role of CCR5 in the development of EAG. We found that the development of EAG was not prevented in CCR5-deficient mice. Using reverse-transcriptase analysis of stomachs from normal and gastritic mice we found no difference in expression of CCR5 and its chemokine ligands MIP-1alpha, MIP-1beta, and RANTES. We also found that the CCR5 antagonist met-RANTES failed to prevent the development of EAG induced by neonatal thymectomy. These observations suggest that the CC chemokine receptor CCR5 is not essential for development of EAG.

Stem cells engineered to express self-antigen to treat autoimmunity

Autoimmune diseases are incurable. We propose a combination curative strategy using haematopoietic stem cells and gene therapy. The strategy should establish molecular chimerism with culprit antigen expressed by donor antigen-presenting cells in the thymus, resulting in immunological tolerance. Our strategy is based on the intrathymic tolerance and disease resistance established by transgenic expression of antigen in the thymus under control of an MHC class II promoter. We propose that transplantation with genetically engineered stem cells provides an advance over current autologous bone marrow transplantation, in that it should remove the significant risk of disease relapse.

Tolerance established in autoimmune disease by mating or bone marrow transplantation that target autoantigen to thymus

Autoimmune diseases are a significant cause of death and morbidity, affecting up to 5% of the population. At present, there is no cure. Autologous bone marrow transplantation has been promoted as a treatment for achieving disease reversal and long-term remission. However, clinical trials in progress in Europe and North America report a significant risk of relapse. Here, we have addressed whether we can establish tolerance in an active autoimmune disease model by thymic expression of autoantigen. We show that tolerance and disease resistance can indeed be established in transgenic mice that spontaneously develop granulocyte macrophage colony stimulating factor-induced autoimmune gastritis, by mating them with disease-resistant transgenic mice that target autoantigen to the thymus. T cells from these double-transgenic mice are non-responsive to gastric antigen in vitro and fail to initiate disease following transfer to naive recipients. Further, we show that transplantation with bone marrow from disease-resistant transgenic mice renders recipient mice with gastritis tolerant to autoantigen as shown by a dramatic fall in autoantibody levels and T cell non-responsiveness to antigen in vitro. We suggest that genetically modified bone marrow targeting autoantigen to the thymus may be used to establish tolerance and prevent relapse of autoimmune disease following autologous bone marrow transplantation.

Fas/CD95 is required for gastric mucosal damage in autoimmune gastritis

BACKGROUND & AIMS

Experimental autoimmune gastritis (EAG), characterized by a gastric mononuclear cell infiltrate, mucosal cell damage, and autoantibodies to parietal cell-associated H(+)/K(+) adenosine triphosphatase, is a model for human autoimmune gastritis that leads to pernicious anemia. Previous in vitro studies have implicated Fas/CD95 in initiating damage to gastric mucosal cells in humans and an animal model of autoimmune gastritis. Here we used 2 in vivo animal models to examine the role of Fas in the development of mucosal cell damage in autoimmune gastritis.

METHODS

We initiated EAG in BALB/cCrSlc mice by neonatal thymectomy and examined for Fas expression in the gastric mucosa by immunohistochemistry. To address the in vivo relevance of Fas in mucosal injury, we examined the stomachs and sera of BALB/cCrSlc lpr/lpr mice subjected to neonatal thymectomy and BALB/cCrSlc nu/nu lpr/lpr mice transferred with lymphocytes from gastritic BALB/cCrSlc mice.

RESULTS

Fas expression was up-reguiated in parietal cells of mice with EAG. Neonatally thymectomized lpr/lpr mice were resistant to developing destructive gastritis compared with heterozygous and wild-type littermates. Nu/nu Fas-sufficient mice transferred with lymphocytes from thymectomized lpr/lpr mice developed destructive gastritis. Nu/nu lpr/lpr mice transferred with lymphocytes from gastritic mice developed a nondestructive gastritis.

CONCLUSIONS

The observations that Fas is up-regulated in gastric parietal cells of mice with EAG and that Fas-deficient mice are resistant to development of destructive gastritis provide compelling evidence that Fas is required in vivo for development of gastric mucosal cell damage in autoimmune gastritis.

Autoantibodies in neuropsychiatric lupus

The American College of Rheumatology presented a consensus document in 1999 proposing the classification of 19 different syndromes defined by neurological and psychiatric manifestations of systemic lupus erythematosus (SLE). The detection of autoantibodies in patient's serum or cerebrospinal fluid has not been used as diagnostic markers for the proposed neuropsychiatric lupus classifications as their disease associations remain highly contentious. Autoantibodies detected in the serum and/or cerebrospinal fluid, that have been reported to segregate with patients presenting with neuropsychiatric lupus include: (1) anti-neuronal antibodies, (2) brain-lymphocyte cross-reactive antibodies, (3) anti-ribosomal P antibodies, (4) anti-phospholipid antibodies and (5) anti-ganglioside antibodies. Tests for anti-neuronal, anti-brain-lymphocyte cross-reactive and anti-ganglioside antibodies remain highly specialized whereas tests for ribosomal P antibodies and for antiphospholipid antibodies are currently routinely available in most diagnostic laboratories. Anti-ribosomal antibodies segregate with SLE. Antiphospholipid P antibodies are markers for the antiphospholipid syndrome. This syndrome may be associated with another disease, commonly SLE. In this setting, neuropsychiatric manifestations in SLE may arise as a consequence of thrombotic episodes involving the cerebral vasculature. There is a pressing need for antibodies to ribosomal P and to phospholipids to be standardized for routine diagnostic application. We conclude that the search for specific antibody marker(s) that can be applied for the routine laboratory diagnosis for neuropsychiatric lupus remains elusive.

Organ-specific autoimmunity in granulocyte macrophage-colony stimulating factor (GM-CSF) deficient mice

Granulocyte macrophage-colony stimulating factor (GM-CSF) is a pleiotrophic proinflammatory cytokine that augments adaptive immunity by linking it to innate immunity. Experimental autoimmune gastritis is an animal model of human autoimmune gastritis and pernicious anaemia. We have previously shown that GM-CSF is expressed in the gastric mucosa of mice with gastritis initiated by neonatal thymectomy (Gastroenterology 110 (1996) 1791) and that transgenic expression of GM-CSF in the stomach induces autoimmune gastritis in mice (J. Immunol. 166 (2001) 2090). Here we have examined the development of autoimmune gastritis initiated by immunisation or by neonatal thymectomy in GM-CSF deficient mice. We found that gastritis develops in GM-CSF deficient mice initiated by neonatal thymectomy but not by immunisation with gastric antigen. These observations suggest that GM-CSF is not absolutely required for the initiation of autoimmunity and highlights the different conclusions that can be drawn using different disease models.

Animal models of human disease: experimental autoimmune gastritis--a model for autoimmune gastritis and pernicious anemia

Human autoimmune gastritis is an organ-specific autoimmune disease of the stomach. It is characterized by the development of disease-specific autoantibodies and a pathology that specifically targets specialized cells within the gastric environment. The autoantigens associated with this disease have been defined as the gastric H+/K+ ATPase and intrinsic factor. The development of experimental disease models has been pivotal in our contemporary understanding of autoimmunity. Here we review mouse models of autoimmune gastritis and their relevance to human autoimmune gastritis associated with pernicious anemia. We appraise some historical as well as recent studies of experimental autoimmune gastritis (EAG), highlighting key findings that have formed the basis of our current understanding of the etiology and mechanism(s) associated with autoimmune gastritis. A precise understanding of the pathogenesis of autoimmune gastritis will permit the design of innovative and rational therapeutic strategies to prevent, arrest, ameliorate or reverse the disease.

Defining T cell receptors which recognise the immunodominant epitope of the gastric autoantigen, the H/K ATPase beta-subunit

We have previously shown that autoimmune gastritis can be elicited in mice by immunisation with the gastric parietal cell H/K ATPase alphabeta heterodimer, and, furthermore, have identified the H/K ATPase beta-subunit epitope, H/Kbeta253-277 as the dominant epitope of the gastric H/K ATPase. Using gastric H/K ATPase-immunised mice, here we have generated two T cell hybridomas specific for the H/Kbeta253-277 peptide, namely 4B11.F4.5 and 1E4.C1. Hybridoma 4B11.F4.5 uses Valpha8 and Vbeta8.2 TCR chains and 1E4.C1 uses Valpha9 and V1beta8.3 chains. Although both hybridomas are specific for H/Kbeta253-277, T cell assays using overlapping 14-mers of the 25-mer epitope showed that the two autoreactive TCRs recognise different regions of the 25-mer. The TCR from 1E4.C1 has been used to generate a TCR beta-chain transgenic mouse. >80% of peripheral CD4+ T cells utilise the Vbeta8.3 transgene. As expected, 1E4-TCR beta-chain transgenic mice are susceptible to neonatal thymectomy induced autoimmune gastritis. While none of the 1E4-TCR beta chain transgenic mice spontaneously developed a destructive gastritis, a minority (20%) of the transgenic mice developed a non-invasive and non-destructive gastritis. This suggests that the pathogenic T cells are maintained in a tolerant state in the periphery of the transgenic mice.

Local transgenic expression of granulocyte macrophage-colony stimulating factor initiates autoimmunity

Mechanisms leading to breakdown of immunological tolerance and initiation of autoimmunity are poorly understood. Experimental autoimmune gastritis is a paradigm of organ-specific autoimmunity arising from a pathogenic autoimmune response to gastric H/K ATPase. The gastritis is accompanied by autoantibodies to the gastric H/K ATPase. The best characterized model of experimental autoimmune gastritis requires neonatal thymectomy. This procedure disrupts the immune repertoire, limiting its usefulness in understanding how autoimmunity arises in animals with intact immune systems. Here we tested whether local production of GM-CSF, a pro-inflammatory cytokine, is sufficient to break tolerance and initiate autoimmunity. We generated transgenic mice expressing GM-CSF in the stomach. These transgenic mice spontaneously developed gastritis with an incidence of about 80% after six backcrosses to gastritis-susceptible BALBc/CrSlc mice. The gastritis is accompanied by mucosal hypertrophy, enlargement of draining lymph nodes and autoantibodies to gastric H/K ATPase. An infiltrate of dendritic cells and macrophages preceded CD4 T cells into the gastric mucosa. T cells from draining lymph nodes specifically proliferated to the gastric H/K ATPase. CD4 but not CD8 T cells transferred gastritis to nude mouse recipients. CD4(+) CD25(+) T cells from the spleen retained anergic suppressive properties that were reversed by IL-2. We conclude that local expression of GM-CSF is sufficient to break tolerance and initiate autoimmunity mediated by CD4 T cells. This new mouse model should be useful for studies of organ-specific autoimmunity.

Immunopathology of autoimmune gastritis: lessons from mouse models

Autoimmune gastritis in humans is a chronic inflammatory disease of the stomach accompanied by specific destruction of gastric parietal and zymogenic cells resulting in pernicious anemia. Human gastritis can be accurately reproduced in mice and is characterised by autoantibodies to the alpha- and beta-subunits of the gastric H/K ATPase (the enzyme responsible for gastric acid secretion) and cellular destruction of parietal and zymogenic cells within the gastric gland. Studies with these mouse models have given us our current concepts of the immunopathogenesis of the gastritis. Mouse models have shown that a T cell response is generated to the alpha- and beta-subunits of the H/K ATPase and that an immune response to the beta-subunit seems to be required for disease initiation. Using these models, we have defined key events associated with a damaging autoimmune response to the gastric H/K ATPase. The mechanisms associated with the cellular destruction associated with autoimmune gastritis are not know, but may involve signaling through death inducing pathways such as the Fas/FasL and TNF/TNFR pathways. This knowledge should permit us to develop strategies to prevent and treat the gastritis.

The causative H+/K+ ATPase antigen in the pathogenesis of autoimmune gastritis

The gastric H+/K+ ATPase is the causative autoantigen recognized by CD4+ T cells that mediate autoimmune gastritis. Pathogenic CD4+ T cells are regulated by CD25+CD4+ T cells. Here, it is proposed that waves of activation and migration of antigen presenting cells and CD4+ T cells to and from the target organ and draining lymph node result in tissue damage.

Tolerance and autoimmunity to a gastritogenic peptide in TCR transgenic mice

The catalytic alpha and glycoprotein beta subunits of the gastric H/K ATPase are major molecular targets in human and mouse autoimmune gastritis. We have previously shown that the H/K ATPase beta subunit is required for the initiation of mouse gastritis and identified a gastritogenic H/K ATPase beta subunit peptide (H/Kbeta253-277). Here we report the generation of MHC class II-restricted TCR transgenic mice using V(alpha)9 and V(beta)8.3 TCR chains with specificity for the gastritogenic H/Kbeta253-277 peptide. We found an 8-fold reduction in CD4(+) T cells in the thymus of the transgenic mice. Despite the reduction in intrathymic CD4(+) T cells, V(beta)8. 3-expressing T cells comprised the majority (>90%) of peripheral spleen and lymph node T cells. These peripheral T cells retained their capacity to proliferate in vitro to the H/Kbeta253-277 peptide. Using the responsive T cells, we have restricted the gastritogenic T cell epitope to H/Kbeta261-274. Despite the capacity of the peripheral T cells to proliferate in vitro to the peptide, the majority ( approximately 80%, 13 of 16) of transgenic mice remained free of gastritis while a minority (20%, three of 16) spontaneously developed an invasive and destructive gastritis. Our results confirm that H/Kbeta261-274 is a gastritogenic peptide. The data also suggest that CD4 T cell tolerance to the gastritogenic peptide in the transgenic mice is maintained by a combination of intrathymic and peripheral tolerance mechanisms.

Spontaneous autoimmune gastritis in C3H/He mice: a new mouse model for gastric autoimmunity

Autoimmune gastritis is the underlying pathological lesion of pernicious anemia in humans. The lesion is characterized by a chronic inflammatory infiltrate in the gastric mucosa with loss of parietal and zymogenic cells. It is associated with circulating autoantibodies to the gastric H/K-ATPase, the enzyme responsible for acidification of gastric juice. Experimental models of autoimmune gastritis have previously been produced in mice after a variety of manipulations, including thymectomy. Here we report for the first time a spontaneous mouse model of autoimmune gastritis in C3H/He mice. The spontaneous gastritis is also accompanied by circulating autoantibodies to the gastric H/K-ATPase. The spontaneous mouse model should be useful for studies directed toward the immunopathogenesis and treatment of autoimmune gastritis.

Expression of the gastric H/K-ATPase alpha-subunit in the thymus may explain the dominant role of the beta-subunit in the pathogenesis of autoimmune gastritis

The two subunits of the gastric H/K ATPase, namely the catalytic alpha-subunit and the glycoprotein beta-subunit, are the major targets of parietal cell autoantibodies associated with human and murine autoimmune gastritis. The murine disease induced by neonatal thymectomy is T cell-mediated. We have previously shown that transgenic expression of the H/K ATPase beta-subunit gene in the thymus prevented the development of autoimmune gastritis induced by thymectomy. However, little is known of the contribution of the H/K ATPase alpha-subunit in disease development. Here, we show that (1) in contrast to the gastric H/K ATPase beta-subunit, the alpha-subunit gene is expressed in normal BALB/c thymus. (2) transgenic expression of the gastric H/K ATPase alpha-subunit gene in the thymus failed to prevent the development of autoimmune gastritis and (3) normal BALB/c and transgenic mice expressing the alpha-subunit in the thymus develop autoimmune gastritis following immunisation with purified murine gastric H/K ATPase, whereas transgenic mice expressing the beta-subunit in the thymus do not. We propose that the expression of the H/K ATPase alpha-subunit in the normal thymus may account for the predominant role of the beta-subunit in the development of autoimmune gastritis induced either by thymectomy or by immunisation with the ATPase.

Atrophic gastric changes in both Helicobacter felis and Helicobacter pylori infected mice are host dependent and separate from antral gastritis

BACKGROUND/AIMS

The role of host factors has been neglected in studies of the pathogenesis of Helicobacter associated disease. The aim of this study was to assess the response of different mouse strains to infection with a single strain of Helicobacter felis.

METHOD

Six strains of inbred mice were infected with the identical H felis culture and were killed at one month, two months, and six months after infection to assess histopathological changes. In addition, two strains of mice were infected with a mouse adapted strain of H pylori and examined at six months after infection.

RESULTS

In SJL, C3H/He, DBA/2, and C57BL/6 infected mice, severe to moderate chronic active gastritis was observed only in the body of the stomach, which increased in severity over time with specialised cells in the body glands being replaced. As the severity of this damage in the body increased and atrophic changes were seen, the level of bacterial colonisation of the antrum decreased. In contrast, in BALB/c and CBA mice, there was only mild gastritis in the antrum, no remarkable changes were detected in their body mucosa, and no atrophy was seen over time. In both these strains of mice, heavy bacterial colonisation was seen, which tended to increase over the period of the experiment. Of particular importance in this experiment was that bacterial colonisation was mainly restricted to the antrum yet the atrophy, when present, was only observed in the body of the stomach. H pylori infected C3H/He mice showed moderate colonisation of the antrum, which persisted up to six months with little development of atrophy. In contrast, H pylori in C57BL/6 mice showed excellent colonisation of the antrum at two months but six months after infection there was moderate to severe body atrophy, which was associated with a loss of bacteria from the antrum.

CONCLUSIONS

These findings challenge current concepts of the development of Helicobacter induced atrophy in that active chronic gastritis of antrum or the body mucosa, or both, is not a prerequisite. They also suggest an autoimmune basis for the pathology although no autoantibody or antibody to the H+/K+ ATPase was detected. Loss of infecting helicobacters from the stomach together with development of an atrophic gastritis in the body of the stomach is similar to the pattern found in certain H pylori infected human subjects.

Analysis of mononuclear cell infiltrate and cytokine production in murine autoimmune gastritis

BACKGROUND & AIMS

Murine autoimmune gastritis, induced by day-3 thymectomy, is characterized by cellular infiltrates and circulating autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. The aim of this study was to analyze the cellular infiltrates and cytokines in autoimmune gastritis.

METHODS

Stomachs and blood samples from day-3 thymectomized BALB/c mice were obtained from 2 to 12 weeks after thymectomy for analysis.

RESULTS

At 4 weeks, the gastritic infiltrates were composed of macrophages and CD4+ T cells, accompanied by major histocompatibility complex class II expression on gastric epithelial cells. Mucosal B cells, scant at 4 weeks, were abundant at 8 weeks, coincident with the peaking of autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. CD8+ T cells increased marginally during the 12 weeks. Mononuclear cells from diseased stomachs transferred gastritis to nu/nu recipients. At 4 weeks, interleukins 2, 3, 5, 6, and 10; interferon gamma; tumor necrosis factor alpha; and granulocyte-macrophage colony-stimulating factor were detected in gastritic mucosa, but interleukin 4 was not.

CONCLUSIONS

The early lesion of autoimmune gastritis is composed of macrophages and CD4+ T cells with major histocompatibility complex class II expression in gastric epithelial cells. Autoantibody production is a late event. Our results are consistent with a lesion mediated by CD4+ T cells producing a mix of Th1- and Th2-type cytokines.