Mouse models for the study of autoimmune type 1 diabetes: a NOD to similarities and differences to human disease

Surge in regulatory T cells does not prevent onset of hyperglycemia in NOD mice: immune profiles do not correlate with disease severity

Immune profiling of non-obese diabetic (NOD) is a widely employed tool to assess the mechanisms of inflammatory insulitis. Our analysis of the female NOD colony revealed similar distribution of lymphoid lineages to wild type mice, and at various ages of prediabetic and diabetic mice. The profiles of mesenteric and pancreatic lymph nodes differ and often change reciprocally due to directed migration of T cells towards the site of inflammation. Significant events in our colony include early decline in CD4(+)CD25(+)CD62L(+) Treg, accompanied by gradual increase in CD4(+)CD25(+)FoxP3(+) Treg in peripheral lymphoid organs and pancreatic infiltrates. Impressively, aged euglycemic mice display significant transient rise in CD4(+)CD25(-)FoxP3(+) Treg in the thymus, pancreas and draining lymph nodes. A significant difference was superior viability of effector and suppressor cells from new onset diabetics in the presence of high interleukin-2 (IL-2) concentrations in vitro as compared to cells of prediabetic mice. Overall, we found no correlation between FoxP3(+) Treg in the pancreatic lymph nodes and the inflammatory scores of individual NOD mice. CD25(-)FoxP3(+) Treg are markedly increased in the pancreatic infiltrates in late stages of inflammation, possibly an effort to counteract destructive insulitis. Considering extensive evidence that Treg in aged NOD mice are functionally sufficient, quantitative profiling evolves as an unreliable tool to assess mechanism and causes of inflammation under baseline conditions. Immune profiles are modulated by thymic output, cell migration, shedding of markers, proliferation, survival and in-situ evolution of regulatory cells.

Long-term silencing of autoimmune diabetes and improved life expectancy by a soluble pHLA-DR4 chimera in a newly-humanized NOD/DR4/B7 mouse

Several human MHC class II (HLA) molecules are strongly associated with high incidence of autoimmune diseases including type 1 diabetes (T1D). The HLA-humanized mice may thus represent valuable tools to test HLA-based vaccines and therapeutics for human autoimmune diseases. Herein, we have tested the therapeutic potential of a soluble HLA-DR4-GAD65 271-280 (hu DEF-GAD65) chimera of human use in a newly-generated NOD/DR4/B7 double transgenic (dTg) mouse that develops spontaneously an accelerated T1D regardless the gender. The NOD/DR4/B7 dTg mice generated by a two-step crossing protocol express the HLA-DR*0401 molecules on 20% of antigen presenting cells, the human B7 molecules in pancreas, and HLA-DR4/GAD65-specific T-cells in the blood. Some 75% of pre-diabetic NOD/DR4/B7 dTg mice treated with hu DEF-GAD65 chimera remained euglycemic and showed a stabilized pancreatic insulitis 6 months after treatment. The 25% non responders developing hyperglycemia survived 3-4 months longer than their untreated littermates. T1D prevention by this reagent occurred by a Th2/TR-1 polarization in the pancreas. This study strongly suggests that the use of soluble pHLA reagents to suppress/stabilize the T1D progression and to extend the life expectancy in the absence of side effects is an efficient and safe therapeutic approach.

New opportunities: harnessing induced pluripotency for discovery in diabetes and metabolism

The landmark discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has transformed regenerative biology. Previously, insights into the pathogenesis of chronic human diseases have been hindered by the inaccessibility of patient samples. However, scientists are now able to convert patient fibroblasts into iPSCs and differentiate them into disease-relevant cell types. This ability opens new avenues for investigating disease pathogenesis and designing novel treatments. In this review, we highlight the uses of human iPSCs to uncover the underlying causes and pathological consequences of diabetes and metabolic syndromes, multifactorial diseases whose etiologies have been difficult to unravel using traditional methodologies.

Growth hormone prevents the development of autoimmune diabetes

Evidence supports a relationship between the neuroendocrine and the immune systems. Data from mice that overexpress or are deficient in growth hormone (GH) indicate that GH stimulates T and B-cell proliferation and Ig synthesis, and enhances maturation of myeloid progenitor cells. The effect of GH on autoimmune pathologies has nonetheless been little studied. Using a murine model of type 1 diabetes, a T-cell-mediated autoimmune disease characterized by immune cell infiltration of pancreatic islets and destruction of insulin-producing β-cells, we observed that sustained GH expression reduced prodromal disease symptoms and eliminated progression to overt diabetes. The effect involves several GH-mediated mechanisms; GH altered the cytokine environment, triggered anti-inflammatory macrophage (M2) polarization, maintained activity of the suppressor T-cell population, and limited Th17 cell plasticity. In addition, GH reduced apoptosis and/or increased the proliferative rate of β-cells. These results support a role for GH in immune response regulation and identify a unique target for therapeutic intervention in type 1 diabetes.

Advances in our understanding of the pathophysiology of Type 1 diabetes: lessons from the NOD mouse

T1D (Type 1 diabetes) is an autoimmune disease caused by the immune-mediated destruction of pancreatic β-cells. Studies in T1D patients have been limited by the availability of pancreatic samples, a protracted pre-diabetic phase and limitations in markers that reflect β-cell mass and function. The NOD (non-obese diabetic) mouse is currently the best available animal model of T1D, since it develops disease spontaneously and shares many genetic and immunopathogenic features with human T1D. Consequently, the NOD mouse has been extensively studied and has made a tremendous contribution to our understanding of human T1D. The present review summarizes the key lessons from NOD mouse studies concerning the genetic susceptibility, aetiology and immunopathogenic mechanisms that contribute to autoimmune destruction of β-cells. Finally, we summarize the potential and limitations of immunotherapeutic strategies, successful in NOD mice, now being trialled in T1D patients and individuals at risk of developing T1D.

Bacille Calmette-Guérin/DNAhsp65 prime-boost is protective against diabetes in non-obese diabetic mice but not in the streptozotocin model of type 1 diabetes

Type I diabetes is a disease caused by autoimmune destruction of the beta cells in the pancreas that leads to a deficiency in insulin production. The aim of this study was to evaluate the prophylactic potential of a prime-boost strategy involving bacille Calmette-Guérin (BCG) and the pVAXhsp65 vaccine (BCG/DNAhsp65) in diabetes induced by streptozotocin (STZ) in C57BL/6 mice and also in spontaneous type 1 diabetes in non-obese diabetic (NOD) mice. BCG/DNAhsp65 vaccination in NOD mice determined weight gain, protection against hyperglycaemia, decreased islet inflammation, higher levels of cytokine production by the spleen and a reduced number of regulatory T cells in the spleen compared with non-immunized NOD mice. In the STZ model, however, there was no significant difference in the clinical parameters. Although this vaccination strategy did not protect mice in the STZ model, it was very effective in NOD mice. This is the first report demonstrating that a prime-boost strategy could be explored as an immunomodulatory procedure in autoimmune diseases.

Distinct genetic control of autoimmune neuropathy and diabetes in the non-obese diabetic background

The non-obese diabetic (NOD) mouse is susceptible to the development of autoimmune diabetes but also multiple other autoimmune diseases. Over twenty susceptibility loci linked to diabetes have been identified in NOD mice and progress has been made in the definition of candidate genes at many of these loci (termed Idd for insulin-dependent diabetes). The susceptibility to multiple autoimmune diseases in the NOD background is a unique opportunity to examine susceptibility genes that confer a general propensity for autoimmunity versus susceptibility genes that control individual autoimmune diseases. We previously showed that NOD mice deficient for the costimulatory molecule B7-2 (NOD-B7-2KO mice) were protected from diabetes but spontaneously developed an autoimmune peripheral neuropathy. Here, we took advantage of multiple NOD mouse strains congenic for Idd loci to test the role of these Idd loci the development of neuropathy and determine if B6 alleles at Idd loci that are protective for diabetes will also be for neuropathy. Thus, we generated NOD-B7-2KO strains congenic at Idd loci and examined the development of neuritis and clinical neuropathy. We found that the NOD-H-2(g7) MHC region is necessary for development of neuropathy in NOD-B7-2KO mice. In contrast, other Idd loci that significantly protect from diabetes did not affect neuropathy when considered individually. However, we found potent genetic interactions of some Idd loci that provided almost complete protection from neuritis and clinical neuropathy. In addition, defective immunoregulation by Tregs could supersede protection by some, but not other, Idd loci in a tissue-specific manner in a model where neuropathy and diabetes occurred concomitantly. Thus, our study helps identify Idd loci that control tissue-specific disease or confer general susceptibility to autoimmunity, and brings insight to the Treg-dependence of autoimmune processes influenced by given Idd region in the NOD background.

Type 1 diabetes: primary antigen/peptide/register/trimolecular complex

Type 1A diabetes (autoimmune) is now immunologically predictable in man, but preventable only in animal models. What triggers the development of autoimmunity in genetically susceptible individuals remains unknown. Studies of non-obese diabetic (NOD) mice reveal that interactions between T-cell receptors of diabetogenic T cell and an MHC class II loaded with an autoantigen are key determinates of the disease. With insulin as the primary target in the NOD mouse, likely man, and possibly the RT1-U rat models, therapeutic targeting of the components of these anti-insulin trimolecular complexes we believe provide a fulcrum for development of preventive therapy. In particular for the NOD mouse model, there is extensive evidence that the dominant insulin peptide driving disease initiation is insulin B chain amino acids 9-23 (SHLVEALYLVCGERG) recognized predominantly by germ-line sequences of a specific T-cell receptor Valpha (TRAV5D-4), and small molecules or monoclonal antibodies directed at this recognition complex can prevent diabetes.

Genetic control of murine invariant natural killer T cells maps to multiple type 1 diabetes regions

Reduced frequency of invariant natural killer T (iNKT)-cells has been indicated as a contributing factor to type 1 diabetes (T1D) development in NOD mice. To further understand the genetic basis of the defect, we generated (NOD X ICR)F2 mice to map genes that control iNKT-cell development. We determined frequencies of thymic and splenic iNKT-cells as well as the ratio of CD4-positive and -negative subsets in the spleens of 209 F2 males. Quantitative trait loci (QTL) analysis revealed 5 loci that exceed the significant threshold for the frequency of thymic and/or splenic iNKT-cells on Chromosomes (Chr) 1, 5, 6, 12, and 17. Three significant loci on Chr 1, 4, and 5 were found for the ratio of CD4-positive and -negative splenic iNKT-cells. Comparisons to previously known mouse T1D susceptibility (Idd) loci revealed two significant QTL peak locations respectively mapped to Idd regions on Chr 4 and 6. The peak marker location of the significant Chr 12 iNKT QTL maps to within 0.5Mb of a syntenic human T1D locus. Collectively, our results reveal several novel loci controlling iNKT-cell development and provide additional information for future T1D genetic studies.

Several classical mouse inbred strains, including DBA/2, NOD/Lt, FVB/N, and SJL/J, carry a putative loss-of-function allele of Gpr84

G protein-coupled receptor 84 (GPR84) is a 7-transmembrane protein expressed on myeloid cells that can bind to medium-chain free fatty acids in vitro. Here, we report the discovery of a 2-bp frameshift deletion in the second exon of the Gpr84 gene in several classical mouse inbred strains. This deletion generates a premature stop codon predicted to result in a truncated protein lacking the transmembrane domains 4-7. We sequenced Gpr84 exon 2 from 58 strains representing different groups in the mouse family tree and found that 14 strains are homozygous for the deletion. Some of these strains are DBA/1J, DBA/2J, FVB/NJ, LG/J, MRL/MpJ, NOD/LtJ, and SJL/J. However, the deletion was not found in any of the wild-derived inbred strains analyzed. Haplotype analysis suggested that the deletion originates from a unique mutation event that occurred more than 100 years ago, preceding the development of the first inbred strain (DBA), from a Mus musculus domesticus source. As GPR84 ostensibly plays a role in the biology of myeloid cells, it could be relevant 1) to consider the existence of this Gpr84 nonsense mutation in several mouse strains when choosing a mouse model to study immune processes and 2) to consider reevaluating data obtained using such strains.

Genetic and Pharmacologic Models for Type 1 Diabetes

Type 1 diabetes (T1D) is characterized by a partial or total insufficiency of insulin. The premiere animal model of autoimmune T cell-mediated T1D is the NOD mouse. A dominant negative mutation in the mouse insulin 2 gene (Ins2Akita ) produces a severe insulin deficiency syndrome without autoimmune involvement, as do a variety of transgenes overexpressed in beta cells. Pharmacologically-induced T1D (without autoimmunity) elicted by alloxan or streptozotocin at high doses can generate hyperglycemia in almost any strain of mouse by direct toxicity. Multiple low doses of streptozotocin combine direct beta cell toxicity with local inflammation to elicit T1D in a male sex-specific fashion. A summary of protocols relevant to the management of these different mouse models will be covered in this overview.

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.

Variations in rodent models of type 1 diabetes: islet morphology

Type 1 diabetes (T1D) is characterized by hyperglycemia due to lost or damaged islet insulin-producing β -cells. Rodent models of T1D result in hyperglycemia, but with different forms of islet deterioration. This study focused on 1 toxin-induced and 2 autoimmune rodent models of T1D: BioBreeding Diabetes Resistant rats, nonobese diabetic mice, and Dark Agouti rats treated with streptozotocin. Immunochemistry was used to evaluate the insulin levels in the β -cells, cell composition, and insulitis. T1D caused complete or significant loss of β -cells in all animal models, while increasing numbers of α -cells. Lymphocytic infiltration was noted in and around islets early in the progression of autoimmune diabetes. The loss of lymphocytic infiltration coincided with the absence of β -cells. In all models, the remaining α - and δ -cells regrouped by relocating to the islet center. The resulting islets were smaller in size and irregularly shaped. Insulin injections subsequent to induction of toxin-induced diabetes significantly preserved β -cells and islet morphology. Diabetes in animal models is anatomically heterogeneous and involves important changes in numbers and location of the remaining α - and δ -cells. Comparisons with human pancreatic sections from healthy and diabetic donors showed similar morphological changes to the diabetic BBDR rat model.

Advances in murine models of diabetic nephropathy

Diabetic nephropathy (DN) is one of the microvascular complications of both type 1 and type 2 diabetes, which is also associated with a poor life expectancy of diabetic patients. However, the pathogenesis of DN is still unclear. Thus, it is of great use to establish appropriate animal models of DN for doing research on pathogenesis and developing novel therapeutic strategies. Although a large number of murine models of DN including artificially induced, spontaneous, and genetically engineered (knockout and transgenic) animal models have been developed, none of them develops renal changes sufficiently reflecting those seen in humans. Here we review the identified murine models of DN from the aspects of genetic background, type of diabetes, method of induction, gene deficiency, animal age and gender, kidney histopathology, and phenotypic alterations in the hope of enhancing our comprehension of genetic susceptibility and molecular mechanisms responsible for this disease and providing new clues as to how to choose appropriate animal models of DN.

Comparative genetics: synergizing human and NOD mouse studies for identifying genetic causation of type 1 diabetes

Although once widely anticipated to unlock how human type 1 diabetes (T1D) develops, extensive study of the nonobese diabetic (NOD) mouse has failed to yield effective treatments for patients with the disease. This has led many to question the usefulness of this animal model. While criticism about the differences between NOD and human T1D is legitimate, in many cases disease in both species results from perturbations modulated by the same genes or different genes that function within the same biological pathways. Like in humans, unusual polymorphisms within an MHC class II molecule contributes the most T1D risk in NOD mice. This insight supports the validity of this model and suggests the NOD has been improperly utilized to study how to cure or prevent disease in patients. Indeed, clinical trials are far from administering T1D therapeutics to humans at the same concentration ranges and pathological states that inhibit disease in NOD mice. Until these obstacles are overcome it is premature to label the NOD mouse a poor surrogate to test agents that cure or prevent T1D. An additional criticism of the NOD mouse is the past difficulty in identifying genes underlying T1D using conventional mapping studies. However, most of the few diabetogenic alleles identified to date appear relevant to the human disorder. This suggests that rather than abandoning genetic studies in NOD mice, future efforts should focus on improving the efficiency with which diabetes susceptibility genes are detected. The current review highlights why the NOD mouse remains a relevant and valuable tool to understand the genes and their interactions that promote autoimmune diabetes and therapeutics that inhibit this disease. It also describes a new range of technologies that will likely transform how the NOD mouse is used to uncover the genetic causes of T1D for years to come.

The immunobiology of apotransferrin in type 1 diabetes

The transferrin (Tf) family of iron binding proteins includes important endogenous modulators of the immune function that may modulate autoimmune diseases. To define more clearly the role of apotransferrin (apoTf) in type 1 diabetes we determined the impact of this protein on type 1 diabetes as investigated in islet cells, animal models and patient sera. First, we demonstrated that recombinant apoTf counteracts the cytokine-induced death of murine pancreatic islet cells. Secondly, human apoTf administration favourably influences the course of type 1 diabetes in animal models, resulting in protection against disease development that was associated with reduction of insulitis and reduced levels of proinflammatory cytokines. Finally, we confirmed that patients with newly diagnosed type 1 diabetes manifest significantly lower apoTf serum levels compared to healthy controls and patients with long-lasting disease. In conclusion, our data suggest the apoTf pivotal role in the perpetuation of type 1 diabetes pathology.

The use of animal models in diabetes research

Diabetes is a disease characterized by a relative or absolute lack of insulin, leading to hyperglycaemia. There are two main types of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes is due to an autoimmune destruction of the insulin-producing pancreatic beta cells, and type 2 diabetes is caused by insulin resistance coupled by a failure of the beta cell to compensate. Animal models for type 1 diabetes range from animals with spontaneously developing autoimmune diabetes to chemical ablation of the pancreatic beta cells. Type 2 diabetes is modelled in both obese and non-obese animal models with varying degrees of insulin resistance and beta cell failure. This review outlines some of the models currently used in diabetes research. In addition, the use of transgenic and knock-out mouse models is discussed. Ideally, more than one animal model should be used to represent the diversity seen in human diabetic patients.

Granzyme B is dispensable in the development of diabetes in non-obese diabetic mice

Pancreatic beta cell destruction in type 1 diabetes is mediated by cytotoxic CD8(+) T lymphoctyes (CTL). Granzyme B is an effector molecule used by CTL to kill target cells. We previously showed that granzyme B-deficient allogeneic CTL inefficiently killed pancreatic islets in vitro. We generated granzyme B-deficient non-obese diabetic (NOD) mice to test whether granzyme B is an important effector molecule in spontaneous type 1 diabetes. Granzyme B-deficient islet antigen-specific CD8(+) T cells had impaired homing into islets of young mice. Insulitis was reduced in granzyme B-deficient mice at 70 days of age (insulitis score 0.043±0.019 in granzyme B-deficient versus 0.139±0.034 in wild-type NOD mice p<0.05), but was similar to wild-type at 100 and 150 days of age. We observed a reduced frequency of CD3(+)CD8(+) T cells in the islets and peripheral lymphoid tissues of granzyme B-deficient mice (p<0.005 and p<0.0001 respectively), but there was no difference in cell proportions in the thymus. Antigen-specific CTL developed normally in granzyme B-deficient mice, and were able to kill NOD islet target cells as efficiently as wild-type CTL in vitro. The incidence of spontaneous diabetes in granzyme B-deficient mice was the same as wild-type NOD mice. We observed a delayed onset of diabetes in granzyme B-deficient CD8-dependent NOD8.3 mice (median onset 102.5 days in granzyme B-deficient versus 57.50 days in wild-type NOD8.3 mice), which may be due to the delayed onset of insulitis or inefficient priming at an earlier age in this accelerated model of diabetes. Our data indicate that granzyme B is dispensable for beta cell destruction in type 1 diabetes, but is required for efficient early activation of CTL.

Subcongenic analyses reveal complex interactions between distal chromosome 4 genes controlling diabetogenic B cells and CD4 T cells in nonobese diabetic mice

Autoimmune type 1 diabetes (T1D) in humans and NOD mice results from interactions between multiple susceptibility genes (termed Idd) located within and outside the MHC. Despite sharing ∼88% of their genome with NOD mice, including the H2(g7) MHC haplotype and other important Idd genes, the closely related nonobese resistant (NOR) strain fails to develop T1D because of resistance alleles in residual genomic regions derived from C57BLKS mice mapping to chromosomes (Chr.) 1, 2, and 4. We previously produced a NOD background strain with a greatly decreased incidence of T1D as the result of a NOR-derived 44.31-Mb congenic region on distal Chr. 4 containing disease-resistance alleles that decrease the pathogenic activity of autoreactive B and CD4 T cells. In this study, a series of subcongenic strains for the NOR-derived Chr. 4 region was used to significantly refine genetic loci regulating diabetogenic B and CD4 T cell activity. Analyses of these subcongenic strains revealed the presence of at least two NOR-origin T1D resistance genes within this region. A 6.22-Mb region between rs13477999 and D4Mit32, not previously known to contain a locus affecting T1D susceptibility and now designated Idd25, was found to contain the main NOR gene(s) dampening diabetogenic B cell activity, with Ephb2 and/or Padi2 being strong candidates as the causal variants. Penetrance of this Idd25 effect was influenced by genes in surrounding regions controlling B cell responsiveness and anergy induction. Conversely, the gene(s) controlling pathogenic CD4 T cell activity was mapped to a more proximal 24.26-Mb region between the rs3674285 and D4Mit203 markers.

Life in the fast lane: mammalian disease models in the genomics era

Analyses of the human genome have proven extremely successful in identifying changes that contribute to human disease. Genetically engineered mice provide a powerful tool to analyze these changes, although they are slow and costly and do not always recapitulate human biology. Recent advances in genomic technologies, rodent-modeling approaches, and the production of patient-derived reprogrammed cell lines now provide a plethora of complementary systems to study disease states and test new therapies. Continued evolution and integration of these model systems will be the key to realizing the benefits of the genomic revolution and refining our understanding and treatment of human diseases.

Altered metabolic signature in pre-diabetic NOD mice

Altered metabolism proceeding seroconversion in children progressing to Type 1 diabetes has previously been demonstrated. We tested the hypothesis that non-obese diabetic (NOD) mice show a similarly altered metabolic profile compared to C57BL/6 mice. Blood samples from NOD and C57BL/6 female mice was collected at 0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 13 and 15 weeks and the metabolite content was analyzed using GC-MS. Based on the data of 89 identified metabolites OPLS-DA analysis was employed to determine the most discriminative metabolites. In silico analysis of potential involved metabolic enzymes was performed using the dbSNP data base. Already at 0 weeks NOD mice displayed a unique metabolic signature compared to C57BL/6. A shift in the metabolism was observed for both strains the first weeks of life, a pattern that stabilized after 5 weeks of age. Multivariate analysis revealed the most discriminative metabolites, which included inosine and glutamic acid. In silico analysis of the genes in the involved metabolic pathways revealed several SNPs in either regulatory or coding regions, some in previously defined insulin dependent diabetes (Idd) regions. Our result shows that NOD mice display an altered metabolic profile that is partly resembling the previously observation made in children progressing to Type 1 diabetes. The level of glutamic acid was one of the most discriminative metabolites in addition to several metabolites in the TCA cycle and nucleic acid components. The in silico analysis indicated that the genes responsible for this reside within previously defined Idd regions.

The non-obese diabetic (NOD) mouse as a model of human type 1 diabetes

The non-obese diabetic (NOD) mouse spontaneously develops type 1 diabetes (T1D) and has thus served as a model for understanding the genetic and immunological basis, and treatment, of T1D. Since its initial description in 1980, however, the field has matured and recognized that prevention of diabetes in NOD mice (i.e., preventing the disease from occurring by an intervention prior to frank diabetes) is relatively easy to achieve and does not correlate well with curing the disease (after the onset of frank hyperglycemia). Hundreds of papers have described the prevention of diabetes in NOD mice but only a handful have described its actual reversal. The paradoxical conclusion is that preventing the disease in NOD mice does not necessarily tell us what caused the disease nor how to reverse it. The NOD mouse model is therefore best used now, with respect to human disease, as a way to understand the genetic and immunologic causes of and as a model for trying to reverse disease once hyperglycemia occurs. We describe how genetic approaches to identifying causative gene variants can be adapted to identify novel therapeutic agents for reversing new-onset T1D.

Calcium insufficiency accelerates type 1 diabetes in vitamin D receptor-deficient nonobese diabetic (NOD) mice

Vitamin D exerts important regulatory effects on the endocrine and immune systems. Autoimmune type 1 diabetes (T1D) development in the inbred NOD mouse strain can be accelerated by vitamin D insufficiency or suppressed by chronic treatment with high levels of 1α,25-dihydroxyvitamin D(3). Consequently, a report that T1D development was unaffected in NOD mice genetically lacking the vitamin D receptor (VDR) was unexpected. To further assess this result, the mutant stock was imported to The Jackson Laboratory, backcrossed once to NOD/ShiLtJ, and progeny rederived through embryo transfer. VDR-deficient NOD mice of both sexes showed significant acceleration of T1D. This acceleration was not associated with alterations in immune cells targeting pancreatic β-cells. Rather, the capacity of β-cells to produce and/or secrete insulin was severely impaired by the hypocalcaemia developing in VDR-deficient NOD mice fed a standard rodent chow diet. Feeding a high-lactose calcium rescue diet that circumvents a VDR requirement for calcium absorption from the intestine normalized serum calcium levels, restored β-cell insulin secretion, corrected glucose intolerance, and eliminated accelerated T1D in VDR-deficient NOD mice. These findings suggest that calcium and/or vitamin D supplementation may improve disease outcomes in some T1D-prone individuals that are calcium deficient.

Understanding type 1 diabetes through genetics: advances and prospects

Starting with early crucial discoveries of the role of the major histocompatibility complex, genetic studies have long had a role in understanding the biology of type 1 diabetes (T1D), which is one of the most heritable common diseases. Recent genome-wide association studies (GWASs) have given us a clearer picture of the allelic architecture of genetic susceptibility to T1D. Fine mapping and functional studies are gradually revealing the complex mechanisms whereby immune self-tolerance is lost, involving multiple aspects of adaptive immunity. The triggering of these events by dysregulation of the innate immune system has also been implicated by genetic evidence. Finally, genetic prediction of T1D risk is showing promise of use for preventive strategies.

Development of type 1 diabetes mellitus in nonobese diabetic mice follows changes in thymocyte and peripheral T lymphocyte transcriptional activity

As early as one month of age, nonobese diabetic (NOD) mice feature pancreatic infiltration of autoreactive T lymphocytes, which destruct insulin-producing beta cells, producing autoimmune diabetes mellitus (T1D) within eight months. Thus, we hypothesized that during the development of T1D, the transcriptional modulation of immune reactivity genes may occur as thymocytes mature into peripheral T lymphocytes. The transcriptome of thymocytes and peripheral CD3⁺ T lymphocytes from prediabetic or diabetic mice analyzed through microarray hybridizations identified 2,771 differentially expressed genes. Hierarchical clustering grouped mice according to age/T1D onset and genes according to their transcription profiling. The transcriptional activity of thymocytes developing into peripheral T lymphocytes revealed sequential participation of genes involved with CD4⁺/CD8⁺ T-cell differentiation (Themis), tolerance induction by Tregs (Foxp3), and apoptosis (Fasl) soon after T-cell activation (IL4), while the emergence of T1D coincided with the expression of cytotoxicity (Crtam) and inflammatory response genes (Tlr) by peripheral T lymphocytes.

An update on the use of NOD mice to study autoimmune (Type 1) diabetes

The widely used nonobese diabetic (NOD) mouse model of autoimmune (Type 1) diabetes mellitus shares multiple characteristics with the human disease, and studies employing this model continue to yield clinically relevant and important information. Here, we review some of the recent key findings obtained from NOD mouse investigations that have both advanced our understanding of disease pathogenesis and suggested new therapeutic targets and approaches. Areas discussed include antigen discovery, identification of genes and pathways contributing to disease susceptibility, development of strategies to image islet inflammation and the testing of therapeutics. We also review recent technical advances that, combined with an improved understanding of the NOD mouse model's limitations, should work to ensure its popularity, utility and relevance in the years ahead.

B cell-directed therapies in type 1 diabetes

B cells play a pathogenic role as antigen-presenting cells and autoantibody secretors in the lead up to T cell-mediated autoimmune destruction of insulin-producing β cells in type 1 diabetes (T1D). This has led to significant interest in the use of B cell depletion therapies as a treatment for T1D. In this review, we compare results from five recent studies that used distinct B cell-depleting agents and protocols to successfully prevent and even reverse T1D in the non-obese diabetic (NOD) mouse model. We discuss how information gained from animal studies could be used to improve on the positive outcomes of a completed phase II clinical trial of the B cell-depleting drug rituximab in humans with recent-onset T1D.

Prevention of "Humanized" diabetogenic CD8 T-cell responses in HLA-transgenic NOD mice by a multipeptide coupled-cell approach

OBJECTIVE

Type 1 diabetes can be inhibited in standard NOD mice by autoantigen-specific immunotherapy targeting pathogenic CD8+ T-cells. NOD.β2m(null).HHD mice expressing human HLA-A2.1 but lacking murine major histocompatibility complex class I molecules develop diabetes characterized by CD8 T-cells recognizing certain autoantigenic peptides also targeted in human patients. These include peptides derived from the pancreatic β-cell proteins insulin (INS1/2 A(2-10) and INS1 B(5-14)) and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP(265-273) and IGRP(228-236)). Hence, NOD.β2m(null).HHD mice represent a model system for developing potentially clinically translatable interventions for suppressing diabetogenic HLA-A2.1-restricted T-cell responses.

RESEARCH DESIGN AND METHODS

Starting at 4-6 weeks of age, NOD.β2m(null).HHD female mice were injected intravenously with syngeneic splenocytes to which various admixtures of the four above-mentioned peptides were bound by the cross-linking agent ethylene carbodiimide (ECDI).

RESULTS

Treatment with such cells bearing the complete cocktail of INS and IGRP epitopes (designated INS/IGRP-SPs) significantly inhibited diabetes development in NOD.β2m(null).HHD recipients compared with controls receiving splenocytes coupled with an irrelevant HLA-A2.1-restricted Flu16 peptide. Subsequent analyses found syngeneic splenocytes bearing the combination of the two ECDI-coupled IGRPs but not INS peptides (IGRP-SPs or INS-SPs) effectively inhibited diabetes development in NOD.β2m(null).HHD mice. This result was supported by enzyme-linked immunospot (ELISPOT) analyses indicating combined INS/IGRP-SPs diminished HLA-A2.1-restricted IGRP but not INS autoreactive CD8+ T-cell responses in NOD.β2m(null).HHD mice.

CONCLUSIONS

These data support the potential of a cell therapy approach targeting HLA-A2.1-restricted IGRP autoreactive CD8 T-cells as a diabetes intervention approach in appropriate human patients.

Unmasking genes in a type 1 diabetes-resistant mouse strain that enhances pathogenic CD8 T-cell responses

OBJECTIVE

Nominally resistant mouse strains such as C57BL/6 (B6) harbor latent type 1 diabetes susceptibility genes uncovered in outcross to disease-susceptible NOD mice. However, identification of possible recessively acting B6-derived susceptibility genes is limited because very few F2 progeny derived from outcrossing this strain with NOD develop spontaneous autoimmune diabetes. Thus, we assessed whether a transgenic T-cell receptor (TCR) disease transfer model allowed the mapping of recessively acting B6 genetic loci that in the proper context contribute to diabetes.

RESEARCH DESIGN AND METHODS

CD8 T-cells transgenically expressing the diabetogenic AI4 TCR were transferred into 91 (NODxB6.H2(g7))F1xB6.H2(g7) first-backcross (BC1) females. A genome-wide scan was performed for loci affecting clinical diabetes and insulitis severity.

RESULTS

A major locus on chromosome 11 in tight linkage with the marker D11Mit48 (logarithm of odds score = 13.2) strongly determined whether BC1 progeny were susceptible to AI4 T-cell-mediated diabetes. Mice homozygous versus heterozygous for B6 markers of this chromosome 11 genetic locus were, respectively, highly susceptible or resistant to AI4-induced insulitis and diabetes. The genetic effect is manifest by host CD4 T-cells. Microarray analyses of mRNA transcript expression identified a limited number of candidate genes.

CONCLUSIONS

The distal region of chromosome 11 in B6 mice harbors a previously unrecognized recessively acting gene(s) that can promote autoreactive diabetogenic CD8 T-cell responses. Future identification of this gene(s) may further aid the screening of heterogeneous humans at future risk for diabetes, and might also provide a target for possible disease interventions.

T-cell autoantigens in the non-obese diabetic mouse model of autoimmune diabetes

The non-obese diabetic (NOD) mouse model of autoimmune (type 1) diabetes has contributed greatly to our understanding of disease pathogenesis and has facilitated the development and testing of therapeutic strategies to combat the disease. Although the model is a valuable immunological tool in its own right, it reaches its fullest potential in areas where its findings translate to the human disease. Perhaps the foremost example of this is the field of T-cell antigen discovery, from which diverse benefits can be derived, including the development of antigen-specific disease interventions. The majority of NOD T-cell antigens are also targets of T-cell autoimmunity in patients with type 1 diabetes, and several of these are currently being evaluated in clinical trials. Here we review the journeys of these antigens from bench to bedside. We also discuss several recently identified NOD T-cell autoantigens whose translational potential warrants further investigation.