Metabolomics and Lipidomics Study of Mouse Models of Type 1 Diabetes Highlights Divergent Metabolism in Purine and Tryptophan Metabolism Prior to Disease Onset.

With the increase in incidence of type 1 diabetes (T1DM), there is an urgent need to understand the early molecular and metabolic alterations that accompany the autoimmune disease. This is not least because in murine models early intervention can prevent the development of disease. We have applied a liquid chromatography (LC-) and gas chromatography (GC-) mass spectrometry (MS) metabolomics and lipidomics analysis of blood plasma and pancreas tissue to follow the progression of disease in three models related to autoimmune diabetes: the nonobese diabetic (NOD) mouse, susceptible to the development of autoimmune diabetes, and the NOD-E (transgenic NOD mice that express the I-E heterodimer of the major histocompatibility complex II) and NOD-severe combined immunodeficiency (SCID) mouse strains, two models protected from the development of diabetes. All three analyses highlighted the metabolic differences between the NOD-SCID mouse and the other two strains, regardless of diabetic status indicating that NOD-SCID mice are poor controls for metabolic changes in NOD mice. By comparing NOD and NOD-E mice, we show the development of T1DM in NOD mice is associated with changes in lipid, purine, and tryptophan metabolism, including an increase in kynurenic acid and a decrease in lysophospholipids, metabolites previously associated with inflammation.

The Schistosoma mansoni T2 ribonuclease omega-1 modulates inflammasome-dependent IL-1ß secretion in macrophages.

The T2 ribonuclease omega-1 is a powerful Th2-inducing factor secreted by the eggs of the blood fluke Schistosoma mansoni. Omega-1 can modulate pattern recognition receptor-induced inflammatory signatures and alter antigen presentation by dendritic cells. Recent findings have suggested that component(s) contained in or secreted by S. mansoni eggs (soluble egg antigen) can also enhance IL-1ß secretion by dendritic cells stimulated with pattern recognition receptor ligands. Here we show that omega-1 enhances IL-1ß secretion in macrophages stimulated with Toll-like receptor 2 ligand, and propose omega-1 as the factor in soluble egg antigen capable of regulating inflammasome activity. This effect is dependent on the C-type lectin receptor Dectin-1, caspase-8 and the ASC inflammasome adaptor protein, highlighting the ability of omega-1 to regulate multiple pattern recognition receptor signalling pathways. These mechanistic insights into manipulation of host immunity by a parasite product have implications for the design of anti-inflammatory therapeutic drugs.

TARM1 Is a Novel Leukocyte Receptor Complex-Encoded ITAM Receptor That Costimulates Proinflammatory Cytokine Secretion by Macrophages and Neutrophils.

We identified a novel, evolutionarily conserved receptor encoded within the human leukocyte receptor complex and syntenic region of mouse chromosome 7, named T cell-interacting, activating receptor on myeloid cells-1 (TARM1). The transmembrane region of TARM1 contained a conserved arginine residue, consistent with association with a signaling adaptor. TARM1 associated with the ITAM adaptor FcRγ but not with DAP10 or DAP12. In healthy mice, TARM1 is constitutively expressed on the cell surface of mature and immature CD11b(+)Gr-1(+) neutrophils within the bone marrow. Following i.p. LPS treatment or systemic bacterial challenge, TARM1 expression was upregulated by neutrophils and inflammatory monocytes and TARM1(+) cells were rapidly recruited to sites of inflammation. TARM1 expression was also upregulated by bone marrow-derived macrophages and dendritic cells following stimulation with TLR agonists in vitro. Ligation of TARM1 receptor in the presence of TLR ligands, such as LPS, enhanced the secretion of proinflammatory cytokines by macrophages and primary mouse neutrophils, whereas TARM1 stimulation alone had no effect. Finally, an immobilized TARM1-Fc fusion protein suppressed CD4(+) T cell activation and proliferation in vitro. These results suggest that a putative T cell ligand can interact with TARM1 receptor, resulting in bidirectional signaling and raising the T cell activation threshold while costimulating the release of proinflammatory cytokines by macrophages and neutrophils.

Protection of islet grafts through transforming growth factor-ß-induced tolerogenic dendritic cells.

In type 1 diabetes, the insulin-producing ß-cells are destroyed by the immune system. One way of restoring glucose control is to transplant ß-cells from a donor. Although this procedure may restore endogenous insulin production, immunosuppressive treatment is needed to prevent the recipient from rejecting the donor-derived islets. We investigated the possibilities of transient expression of the immunosuppressive cytokine transforming growth factor (TGF)-ß within islets to achieve long-term graft tolerance. We found that brief expression of TGF-ß prevented rejection of syngeneic islets, that there was reduction of dendritic cell (DC) activation in the graft, and that there was reduced reactivation of T cells in the graft-draining lymph nodes. In vitro exposure of bone marrow-derived DCs to TGF-ß reduced expression of costimulatory molecules CD80 and CD86, as well as production of proinflammatory cytokines such as interleukin-12 p70 in DCs, but did not alter levels of major histocompatibility complex classes I and II. Furthermore, the capacity of TGF-ß-treated bone marrow-derived DCs to activate both CD4(+) and CD8(+) T cells was reduced. Adding TGF-ß-conditioned tolerogenic DCs to the grafted islets led to long-term survival of the graft, demonstrating that TGF-ß-induced tolerogenic DCs can provide an effective means to restore immune tolerance in an already established autoimmune disease.

Vaccine against autoimmune disease: can helminths or their products provide a therapy?

There is an increasing interest in exploiting the immunomodulatory effects of helminths and their products in treatment of diseases such as allergy, autoimmunity and inflammatory bowel disease. Detailed examination of the ways in which helminth derived products interact with the host immune system and with host physiology has revealed that these may be multifaceted and have almost certainly arisen following co-evolution of helminths and their hosts. Clinical trials have been initiated with encouraging results in the treatment of inflammatory bowel disease and also Multiple Sclerosis. Identification of key pathways that are manipulated by helminths to ameliorate ongoing inflammatory conditions increases the prospect of developing novel therapies for the treatment and possible prevention of a range of debilitating and life threatening conditions.

Helminth mediated modulation of Type 1 diabetes (T1D).

Type 1 diabetes is increasing dramatically in incidence in the developed world. While there may be several reasons for this, improved sanitation and public health measures have altered our interactions with certain infectious agents such as helminths. There is increasing interest in the use of helminths or their products to alleviate inflammatory or allergic conditions. Using rodent models of diabetes, it has been possible to explore the therapeutic potential of both live infections as well as helminth-derived products on the development of autoimmunity. This review provides an overview of the findings from animal models and additionally explores the potential for translation to the clinic.

Inflammation and type one diabetes.

Type one diabetes (T1D) is a complex T cell-mediated autoimmune disease, the defining feature of which is the destruction of the insulin-secreting beta- (ß)- cell. Both genetic and environmental factors combine to precipitate disease, and the outcome of the pathological process is dependent on multiple inter-related factors. In this review, the mechanisms behind the initiation and propagation of the autoimmune response are analysed, and the contribution of differing T-helper (T(h)) subsets--in particular T(h)1- and T(h)17-related cytokines--to the disease process are discussed. An argument is then synthesized that proposes that the ß-cell's response to stress and inflammation is the critical determinant in predicting disease outcome and that, immunologically, a delicate balance exists between regulation and inflammation at the site of islet infiltration. Strategies for disease intervention, therefore, will not only require the induction of T-cell tolerance by tipping the balance towards regulation but will also need to contain approaches that result in the scavenging of inflammatory mediators, in order to facilitate repair. Ultimately, given that clinical diabetes presents late in the autoimmune process, strategies for ß-cell regeneration must now be addressed. There is thus a requirement for an increased, collaborative effort between stem cell biologists and immunologists in order to tailor an optimal therapeutic strategy for the treatment of this debilitating disease.

Helminth infection and type 1 diabetes.

The increasing incidence of type 1 diabetes (T1D) and autoimmune diseases in industrialized countries cannot be exclusively explained by genetic factors. Human epidemiological studies and animal experimental data provide accumulating evidence for the role of environmental factors, such as infections, in the regulation of allergy and autoimmune diseases. The hygiene hypothesis has formally provided a rationale for these observations, suggesting that our co-evolution with pathogens has contributed to the shaping of the present-day human immune system. Therefore, improved sanitation, together with infection control, has removed immunoregulatory mechanisms on which our immune system may depend. Helminths are multicellular organisms that have developed a wide range of strategies to manipulate the host immune system to survive and complete their reproductive cycles successfully. Immunity to helminths involves profound changes in both the innate and adaptive immune compartments, which can have a protective effect in inflammation and autoimmunity. Recently, helminth-derived antigens and molecules have been tested in vitro and in vivo to explore possible applications in the treatment of inflammatory and autoimmune diseases, including T1D. This exciting approach presents numerous challenges that will need to be addressed before it can reach safe clinical application. This review outlines basic insight into the ability of helminths to modulate the onset and progression of T1D, and frames some of the challenges that helminth-derived therapies may face in the context of clinical translation.

PD-L1 blockade overrides Salmonella typhimurium-mediated diabetes prevention in NOD mice: no role for Tregs.

Increasingly, evidence suggests that there is a strong environmental component to the development of the autoimmune disease type 1 diabetes. Our previous data showed that NOD mice are protected from developing diabetes after infection with Salmonella typhimurium and there is some evidence that changes within the DC compartment play a crucial role in this protective effect. This paper further characterises this Salmonella-modulated protective phenotype. We find that, contrary to other infection-mediated models of type 1 diabetes protection, there was no expansion of Foxp3(+) Tregs. Furthermore, transcriptome analysis of DCs identified a distinct Salmonella-induced signature in which the inhibitory receptor PD-L1 was up-regulated. This was confirmed by flow cytometry. In vivo blockade of the PD1/PD-L1 interaction was found to ablate the protective function of Salmonella infection. These data provide evidence for a novel regulatory DC phenotype proficient at controlling autoreactive T cells for an extended duration in the NOD mouse model of diabetes.

The S. mansoni glycoprotein ω-1 induces Foxp3 expression in NOD mouse CD4⁺ T cells.

Immunization with Schistosoma mansoni soluble antigen preparations protects non-obese diabetic (NOD) mice against the development of type 1 diabetes. These preparations have long been known to induce Th2 responses in vitro and in vivo. Recently, two separate groups have reported that ω-1, a well-characterized glycoprotein in S. mansoni soluble egg antigens (SEA), which with IL-4 inducing principle of S. mansoni eggs (IPSE/α-1) is one of the two major glycoproteins secreted by live eggs, is a major SEA component responsible for this effect. We found that ω-1 induces Foxp3 as well as IL-4 expression when injected in vivo. We confirmed that ω-1 conditions DCs to drive Th2 responses and further demonstrated that ω-1 induces Foxp3(+) T cells from NOD mouse naïve T cells. In contrast, IPSE/α-1 did not drive Foxp3 responses. The in vitro development of Foxp3-expressing T cells by ω-1 was TGF-ß- and retinoic acid-dependent. Our work, therefore, identifies ω-1 as an important factor for the induction of Foxp3(+) T cells by SEA in NOD mice.

Infectious triggers protect from autoimmunity.

While some infectious agents have been linked to onset of autoimmune disease there is also other evidence suggesting that certain infectious agents might inhibit autoimmune pathology. This review focuses on the ways in which infectious agents or their products might intervene in an autoimmune response.

Roles for TGF-beta and programmed cell death 1 ligand 1 in regulatory T cell expansion and diabetes suppression by zymosan in nonobese diabetic mice.

Zymosan is a complex fungal component shown to be capable of both promoting and suppressing the development of autoimmune disorders in mice. In this study, we show that a single injection of zymosan just prior to diabetes onset can significantly delay the progression of disease in NOD mice. Zymosan treatment of NOD mice induced the production of biologically active TGF-beta from cells infiltrating the pancreas and was associated with expansion of programmed cell death 1 ligand 1(+)TGF-beta(+) macrophages and Foxp3(+) regulatory T cells in vivo. Neutralization of either TGF-beta or programmed cell death 1 ligand 1 abrogated the protective effects of zymosan. Zymosan acted through TLR2 as well as ERK and p38 MAPK to induce macrophage secretion of TGF-beta and promotion of Foxp3(+) regulatory T cells in vitro and in vivo.

Immune cell crosstalk in type 1 diabetes.

The development of type 1 diabetes involves a complex interaction between pancreatic beta-cells and cells of both the innate and adaptive immune systems. Analyses of the interactions between natural killer (NK) cells, NKT cells, different dendritic cell populations and T cells have highlighted how these different cell populations can influence the onset of autoimmunity. There is evidence that infection can have either a potentiating or inhibitory role in the development of type 1 diabetes. Interactions between pathogens and cells of the innate immune system, and how this can influence whether T cell activation or tolerance occurs, have been under close scrutiny in recent years. This Review focuses on the nature of this crosstalk between the innate and the adaptive immune responses and how pathogens influence the process.

Importance of TLR2 in the direct response of T lymphocytes to Schistosoma mansoni antigens.

The immunomodulatory effect of Schistosoma mansoni antigens has often been attributed to interaction with PRR expressed on APC. Our previous work has shown that S. mansoni-soluble egg antigen (SEA) can induce, together with a Th2 response, TGF-ß-dependent Foxp3 expression in naïve CD4(+) T cells from NOD mice. We found that SEA can directly upregulate the expression of surface-bound TGF-ß in purified CD4(+) T cells in the absence of accessory cell interactions. In this study, we show that the C-type lectin receptors DEC-205 and galectin-3 were involved in the direct interaction between S. mansoni antigens and CD4(+) T cells. SEA was able to enhance CD4(+) T-cell secretion of bioactive TGF-ß in response to TLR2 ligand stimulation, in the absence of APC. We also show that TLR2 expressed on CD4(+) T cells was important for the Foxp3 expression induced by SEA.

Harnessing CD8(+) regulatory T cells: therapy for type 1 diabetes?

In this issue of Immunity, Tsai et al. (2010) demonstrate that low-avidity autoantigen-specific regulatory CD8(+) T cells can reverse ongoing autoimmune disease and provide insight into the mechanism by which this is achieved.

Immune modulation by Schistosoma mansoni antigens in NOD mice: effects on both innate and adaptive immune systems.

We have shown that Schistosoma mansoni egg soluble antigen (SEA) prevents diabetes in the nonobese diabetic (NOD) mouse inducing functional changes in antigen presenting cells (APCs) and expanding T helper (Th) 2 and regulatory T cell (Treg) responses. A Th2 response to S. mansoni infection or its antigens is key to both the establishment of tolerance and successfully reproduction in the host. More recently we demonstrated that SEA treatment upregulates bioactive TGFbeta on T cells with consequent expansion of Foxp3+ Tregs, and these cells might be important in SEA-mediated diabetes prevention together with Th2 cells. In this study we profile further the phenotypic changes that SEA induces on APCs, with particular attention to cytokine expression and markers of macrophage alternative activation. Our studies suggest that TGFbeta from T cells is important not just for Treg expansion but also for the successful Th2 response to SEA, and therefore, for diabetes prevention in the NOD mouse.

Schistosoma mansoni egg antigens induce Treg that participate in diabetes prevention in NOD mice.

Schistosoma mansoni soluble egg antigens (SEA) profoundly regulate the infected host's immune system. We previously showed that SEA prevents type 1 diabetes in NOD mice and that splenocytes from SEA-treated mice have reduced ability to transfer diabetes to NOD.scid recipients. To further characterize the mechanism of diabetes prevention we examined the cell types involved and showed that CD25(+) T-cell depletion of splenocytes from SEA-treated donors restored their ability to transfer diabetes. Furthermore, SEA treatment increased the number and proportional representation of Foxp3(+) T cells in the pancreas of NOD mice. We have used in vitro systems to analyze the effect of SEA on the development of NOD Foxp3(+) T cells. We find that SEA can induce Foxp3 expression in naïve T cells in a TGF-beta-dependent manner. Foxp3 induction requires the presence of DC, which we also show are modified by SEA to upregulate C-type lectins, IL-10 and IL-2. Our studies show that SEA can have a direct effect on CD4(+) T cells increasing expression of TGF-beta, integrin beta8 and galectins. These effects of SEA on DC and T cells may act in synergy to induce Foxp3(+) Treg in the NOD mouse.

Interplay of parasite-driven immune responses and autoimmunity.

As more facts emerge regarding the ways in which parasite-derived molecules modulate the host immune response, it is possible to envisage how a lack of infection by agents that once infected humans commonly might contribute to the rise in autoimmune disease. Through effects on cells of both the innate and adaptive arms of the immune response, parasites can orchestrate a range of outcomes that are beneficial not only to parasites, in terms of facilitating their life cycles, but also to their host, in limiting pathology.

The potential role of chitin in allergic reactions.

Allergy, a potentially life-threatening condition, has at its heart an overly zealous T-helper type 2 response to environmental antigens. We are constantly flooded by potential allergens, both airborne and ingested. Although innocuous to some, common antigens can cause serious allergic reactions in susceptible individuals. Chitin, a polymerized sugar and fundamental component of arthropods and fungi, is not commonly deemed a potential allergen but can cause sensitization through frequent exposure. A recent intriguing study has highlighted the role of chitin in allergic reactions.

Cyclophosphamide-induced type-1 diabetes in the NOD mouse is associated with a reduction of CD4+CD25+Foxp3+ regulatory T cells.

Regulatory T cells (Tregs) have been implicated as key players in immune tolerance as well as suppression of antitumor responses. The chemotherapeutic alkylating agent cyclophosphamide (CY) is widely used in the treatment of tumors and some autoimmune conditions. Although previous data has demonstrated that Tregs may be preferentially affected by CY, its relevance in promoting autoimmune conditions has not been addressed. The nonobese diabetic mouse spontaneously develops type-1 diabetes (T1D). We demonstrate in this study that CY targets CD4+CD25+Foxp3+ Tregs in vivo. CD4+CD25+ T cells isolated from CY-treated mice display reduced suppressive activity in vitro and increased expression of apoptotic markers. Although Treg numbers rapidly recovered to pretreatment levels in the peripheral lymphoid tissues, Tregs failed to recover proportionally within pancreatic infiltrates. T1D progression was effectively prevented by adoptive transfer of a small number of islet Ag-specific CD4+CD25+ Tregs to CY-treated recipients. Prevention of T1D was associated with reduced T cell activation and higher Treg proportions in the pancreas. We conclude that acceleration of T1D by CY is associated with a reduction in CD4+CD25+Foxp3+ Tregs and can be prevented by transfer of CD4+CD25+ Tregs.