Dendritic cell-directed CTLA-4 engagement during pancreatic beta cell antigen presentation delays type 1 diabetes

Immunomodulation by subcutaneously injected methacrylic acid-based hydrogels and tolerogenic dendritic cells in a mouse model of autoimmune diabetes

Type 1 diabetes is an autoimmune disease associated with the destruction of insulin-producing β cells. Immunotherapies are being developed to mitigate autoimmune diabetes. One promising option is the delivery of tolerogenic dendritic cells (DCs) primed with specific β-cell-associated autoantigens. These DCs can combat autoreactive cells and promote expansion of β-cell-specific regulatory immune cells, including Tregs. Tolerogenic DCs are typically injected systemically (or near target lymph nodes) in suspension, precluding control over the microenvironment surrounding tolerogenic DC interactions with the host. In this study we show that degradable, synthetic methacrylic acid (MAA)-based hydrogels are an inherently immunomodulating delivery vehicle that enhances tolerogenic DC therapy in the context of autoimmune diabetes. MAA hydrogels were found to affect the local recruitment and activation state of macrophages, DCs, T cells and other cells. Delivering tolerogenic DCs in the MAA hydrogel improved the local host response (e.g., fewer cytotoxic T cells) and enhanced peripheral Treg expansion. Non obese diabetic (NOD) mice treated with tolerogenic DCs subcutaneously injected in MAA hydrogels showed a delay in onset of autoimmune diabetes compared to control vehicles. Our findings further demonstrate the usefulness of MAA-based hydrogels as platforms for regenerative medicine in the context of type 1 diabetes.

Activation of T cell checkpoint pathways during β-cell antigen presentation by engineered dendritic cells promotes protection from type 1 diabetes

Defective immune regulation has been recognized in type 1 diabetes (T1D). Immune regulatory T cell check-point receptors, which are generally upregulated on activated T cells, have been the molecules of attention as therapeutic targets for enhancing immune response in tumor therapy. Here, we show that pancreatic β-cell antigen (BcAg) presentation by engineered tolerogenic dendritic cells (tDCs) that express CTLA4 selective ligand (B7.1wa) or a combination of CTLA4, PD1 and BTLA selective ligands (B7.1wa, PD-L1, and HVEM-CRD1 respectively; multiligand-DCs) causes an increase in regulatory cytokine and T cell (Treg) responses and suppression of the effector T cell function as compared to engineered control-DCs. Non-obese diabetic (NOD) mice treated with BcAg-pulsed CTLA4-ligand-DCs and multiligand-DCs at pre-diabetic and early-hyperglycemic stages showed significantly lower degree of insulitis, higher frequencies of insulin-positive islets, profound delay in, and reversal of, hyperglycemia for a significant duration. Immune cells from the tDC treated mice not only produced lower amounts of IFNγ and higher amounts of IL10 and TGFβ1 upon BcAg challenge, but also failed to induce hyperglycemia upon adoptive transfer. While both CTLA4-ligand-DCs and multiligand-DCs were effective in inducing tolerance, multiligand-DC treatment produced an overall higher suppressive effect on effector T cell function and disease outcome. These studies show that enhanced engagement of T cell checkpoint receptors during BcAg presentation can modulate T cell function and suppress autoimmunity and progression of the disease in T1D.

Gastrin producing syngeneic mesenchymal stem cells protect non-obese diabetic mice from type 1 diabetes

Progressive destruction of pancreatic islet β-cells by immune cells is a primary feature of type 1 diabetes (T1D) and therapies that can restore the functional β-cell mass are needed to alleviate disease progression. Here, we report the use of mesenchymal stromal/stem cells (MSCs) for the production and delivery of Gastrin, a peptide hormone that is produced by intestinal cells and foetal islets and can increase β-Cell mass, to promote protection from T1D. A single injection of syngeneic MSCs that were engineered to express Gastrin (Gastrin-MSCs) caused a significant delay in hyperglycaemia in non-obese diabetic (NOD) mice compared to engineered control-MSCs. Similar treatment of early-hyperglycaemic mice caused the restoration of euglycemia for a considerable duration, and these therapeutic effects were associated with the protection of, and/or higher frequencies of, insulin-producing islets and less severe insulitis. While the overall immune cell phenotype was not affected profoundly upon treatment using Gastrin-MSCs or upon in vitro culture, pancreatic lymph node cells from Gastrin-MSC treated mice, upon ex vivo challenge with self-antigen, showed a Th2 and Th17 bias, and diminished the diabetogenic property in NOD-Rag1 deficient mice suggesting a disease protective immune modulation under Gastrin-MSC treatment associated protection from hyperglycaemia. Overall, this study shows the potential of production and delivery of Gastrin in vivo, by MSCs, in protecting insulin-producing β-cells and ameliorating the disease progression in T1D.

Engineered Dendritic Cell-Directed Concurrent Activation of Multiple T cell Inhibitory Pathways Induces Robust Immune Tolerance

Inhibitory/repressor-receptors are upregulated significantly on activated T cells, and have been the molecules of attention as targets for inducing immune tolerance. Induction of effective antigen specific tolerance depends on concurrent engagement of the TCR and one or more of these inhibitory receptors. Here, we show, for the first time that dendritic cells (DCs) can be efficiently engineered to express multiple T cell inhibitory ligands, and enhanced engagement of T cell inhibitory receptors, upon antigen presentation, by these DCs can induce effective CD4+ T cell tolerance and suppress autoimmunity. Compared to control DCs, antigen presentation by DCs that ectopically express CTLA4, PD1 and BTLA selective ligands (B7.1wa, PD-L1, and HVEM-CRD1 respectively) individually (mono-ligand DCs) or in combination (multi-ligand DCs) causes an inhibition of CD4+ T cell proliferation and pro-inflammatory cytokine response, as well as increase in Foxp3+ Treg frequency and immune regulatory cytokine production. Administration of self-antigen (mouse thyroglobulin; mTg) loaded multi-ligand DCs caused hyporesponsiveness to mTg challenge, suppression of autoantibody production, and amelioration of experimental autoimmune thyroiditis. Overall, this study shows that engineered DC-directed enhanced concurrent activation of multiple T cell coinhibitory pathways is an effective way to induce self-antigen specific T cell tolerance to suppress ongoing autoimmunity.

Optimal Tolerogenic Dendritic Cells in Type 1 Diabetes (T1D) Therapy: What Can We Learn From Non-obese Diabetic (NOD) Mouse Models?

Tolerogenic dendritic cells (tolDCs) are explored as a promising standalone or combination therapy in type 1 diabetes (T1D). The therapeutic application of tolDCs, including in human trials, has been tested also in other autoimmune diseases, however, T1D displays some unique features. In addition, unlike in several disease-induced animal models of autoimmune diseases, the prevalent animal model for T1D, the NOD mouse, develops diabetes spontaneously. This review compares evidence of various tolDCs approaches obtained from animal (mainly NOD) models of T1D with a focus on parameters of this cell-based therapy such as protocols of tolDC preparation, antigen-specific vs. unspecific approaches, doses of tolDCs and/or autoantigens, application schemes, application routes, the migration of tolDCs as well as their preventive, early pre-onset intervention or curative effects. This review also discusses perspectives of tolDC therapy and areas of preclinical research that are in need of better clarification in animal models in a quest for effective and optimal tolDC therapies of T1D in humans.

Complex dietary polysaccharide modulates gut immune function and microbiota, and promotes protection from autoimmune diabetes

The dietary supplement and prebiotic values of β-glucan-rich products have been widely recognized and dietary approaches for modulating autoimmunity have been increasingly explored, we assess the impact of oral administration of high-purity yeast β-glucan (YBG) on gut immune function, microbiota and type 1 diabetes (T1D) using mouse models. Oral administration of this non-digestible complex polysaccharide caused a dectin-1-dependent immune response involving increased expression of interleukin-10 (IL-10), retinaldehyde dehydrogenase (Raldh) and pro-inflammatory cytokines in the gut mucosa. YBG-exposed intestinal dendritic cells induced/expanded primarily Foxp3⁺ , IL-10⁺ and IL-17⁺ T cells, ex vivo. Importantly, prolonged oral administration of low-dose YBG at pre-diabetic stage suppressed insulitis and significantly delayed the appearance of T1D in non-obese diabetic (NOD) mice. Further, prolonged treatment with YBG showed increased Foxp3⁺ T-cell frequencies, and a significant change in the gut microbiota, particularly an increase in the abundance of Bacteroidetes and a decrease in the Firmicute members. Oral administration of YBG, together with Raldh-substrate and β-cell antigen, resulted in better protection of NOD mice from T1D. These observations suggest that YBG not only has a prebiotic property, but also an oral tolerogenic-adjuvant-like effect, and these features could be exploited for modulating autoimmunity in T1D.

Type 1 diabetes genetic susceptibility and dendritic cell function: potential targets for treatment

Type 1 diabetes is an autoimmune disease that results from the defective induction or maintenance of T cell tolerance against islet β cell self-antigens. Under steady-state conditions, dendritic cells with tolerogenic properties are critical for peripheral immune tolerance. Tolerogenic dendritic cells can induce T cell anergy and deletion and, in some contexts, induce or expand regulatory T cells. Dendritic cells contribute to both immunomodulatory effects and triggering of pathogenesis in type 1 diabetes. This immune equilibrium is affected by both genetic and environmental factors that contribute to the development of type 1 diabetes. Genome-wide association studies and disease association studies have identified >50 polymorphic loci that lend susceptibility or resistance to insulin-dependent diabetes mellitus. In parallel, diabetes susceptibility regions known as insulin-dependent diabetes loci have been identified in the nonobese diabetic mouse, a model for human type 1 diabetes, providing a better understanding of potential immunomodulatory factors in type 1 diabetes risk. Most genetic candidates have annotated immune cell functions, but the focus has been on changes to T and B cells. However, it is likely that some of the genomic susceptibility in type 1 diabetes directly interrupts the tolerogenic potential of dendritic cells in the pathogenic context of ongoing autoimmunity. Here, we will review how gene polymorphisms associated with autoimmune diabetes may influence dendritic cell development and maturation processes that could lead to alterations in the tolerogenic function of dendritic cells. These insights into potential tolerogenic and pathogenic roles for dendritic cells have practical implications for the clinical manipulation of dendritic cells toward tolerance to prevent and treat type 1 diabetes.

Association analysis of PTPN22, CTLA4 and IFIH1 genes with type 1 diabetes in Colombian families

BACKGROUND

Protein tyrosine phosphatase, non-receptor type 22 (lymphoid) (PTPN22), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and interferon induced with helicase C domain 1 (IFIH1) are among the confirmed type 1 diabetes (T1D) susceptibility genes in several populations. The aim of this study was to evaluate the role of PTPN22, CTLA4, and IFIH1 gene variants in the development of T1D in a Colombian population.

METHODS

Associations of PTPN22, CTLA4, and IFIH1 variants with T1D were investigated in a sample of 197 nuclear families, including 205 affected children, in the Colombian population. Three to four single nucleotide polymorphisms (SNPs) were analyzed per gene: rs2476600, rs2476601, rs1217418, and rs2488457 for PTPN22; rs1990760, rs3747517, and rs10930046 for IFIH1; and rs231775, rs3087243, and rs231779 for CTLA4. A transmission disequilibrium test was performed for the global sample, in addition to stratified analysis considering autoimmunity, age at onset, and parent of origin. Haplotypes per gene were also analyzed.

RESULTS

There was no significant transmission distortion for CTLA4. Conversely, SNPs rs10930046 (IFIH1) and rs2476601 (PTPN222) exhibited significant transmission distortion of the C and T alleles, respectively, from parents to affected children (odds ratio [OR] 0.57 and 1.83, respectively). In addition, decreased transmission of the C allele for rs10930046 occurred preferentially from mothers. Stratification analysis revealed that this association was maintained in individuals who were positive for autoantibodies and in those with an age of diagnosis <5 years.

CONCLUSION

The results show that IFIH1 and PTPN22 are associated with T1D in Colombian families.

CTLA-4⁺ Regulatory T Cells Increased in Cetuximab-Treated Head and Neck Cancer Patients Suppress NK Cell Cytotoxicity and Correlate with Poor Prognosis

The EGFR-targeted antibody cetuximab is effective against head and neck cancer (HNSCC), but in only 15% to 20% of patients, and the variability and extent of cetuximab-mediated cellular immunity is not fully understood. We hypothesized that regulatory T cells (Treg) may exert a functional and clinical impact on antitumor immunity in cetuximab-treated individuals. The frequency, immunosuppressive phenotype, and activation status of Treg and natural killer (NK) cells were analyzed in the circulation and tumor microenvironment of cetuximab-treated patients with HNSCC enrolled in a novel neoadjuvant, single-agent cetuximab clinical trial. Notably, cetuximab treatment increased the frequency of CD4(+)FOXP3(+) intratumoral Treg expressing CTLA-4, CD39, and TGFβ. These Treg suppressed cetuximab-mediated antibody-dependent cellular cytotoxicity (ADCC) and their presence correlated with poor clinical outcome in two prospective clinical trial cohorts. Cetuximab expanded CTLA-4(+)FOXP3(+) Treg in vitro, in part, by inducing dendritic cell maturation, in combination with TGFβ and T-cell receptor triggering. Importantly, cetuximab-activated NK cells selectively eliminated intratumoral Treg but preserved effector T cells. In ex vivo assays, ipilimumab targeted CTLA-4(+) Treg and restored cytolytic functions of NK cells mediating ADCC. Taken together, our results argue that differences in Treg-mediated suppression contribute to the clinical response to cetuximab treatment, suggesting its improvement by adding ipilimumab or other strategies of Treg ablation to promote antitumor immunity.

TLR2- and Dectin 1-associated innate immune response modulates T-cell response to pancreatic β-cell antigen and prevents type 1 diabetes

The progression of autoimmune diseases is dictated by deviations in the fine balance between proinflammatory versus regulatory responses, and pathogen recognition receptors (PRRs) play a key role in maintaining this balance. Previously, we have reported that ligation of Toll-like receptor 2 (TLR2) and Dectin 1 on antigen-presenting cells by zymosan results in a regulatory immune response that prevents type 1 diabetes (T1D). Here, we show that TLR2 and Dectin 1 engagement by zymosan promotes regulatory T-cell (Treg) responses against the pancreatic β-cell-specific antigen (Ag). Unlike the TLR4 ligand, bacterial lipopolysaccharide, which induced proinflammatory cytokines and pathogenic T cells, zymosan induced a mixture of pro- and anti-inflammatory factors and Tregs, both in vitro and in vivo. Ag-specific T cells that are activated using zymosan-exposed dendritic cells (DCs) expressed Foxp3 and produced large amounts of IL-10, TGF-β1, and IL-17. NOD mice that received β-cell-Ag-loaded, zymosan-exposed DCs showed delayed hyperglycemia. Injection of NOD mice at the prediabetic age and early hyperglycemic stage with β-cell-Ag, along with zymosan, results in a superior protection of the NOD mice from diabetes as compared with mice that received zymosan alone. This therapeutic effect was associated with increased frequencies of IL-10-, IL-17-, IL-4-, and Foxp3-positive T cells, especially in the pancreatic lymph nodes. These results show that zymosan can be used as an immune regulatory adjuvant for modulating the T-cell response to pancreatic β-cell-Ag and reversing early-stage hyperglycemia in T1D.

Fungal β-glucan, a Dectin-1 ligand, promotes protection from type 1 diabetes by inducing regulatory innate immune response

β-Glucans are naturally occurring polysaccharides in cereal grains, mushrooms, algae, or microbes, including bacteria, fungi, and yeast. Immune cells recognize these β-glucans through a cell surface pathogen recognition receptor called Dectin-1. Studies using β-glucans and other Dectin-1 binding components have demonstrated the potential of these agents in activating the immune cells for cancer treatment and controlling infections. In this study, we show that the β-glucan from Saccharomyces cerevisiae induces the expression of immune regulatory cytokines (IL-10, TGF-β1, and IL-2) and a tolerogenic enzyme (IDO) in bone marrow-derived dendritic cells as well as spleen cells. These properties can be exploited to modulate autoimmunity in the NOD mouse model of type 1 diabetes (T1D). Treatment of prediabetic NOD mice with low-dose β-glucan resulted in a profound delay in hyperglycemia, and this protection was associated with increase in the frequencies of Foxp3(+), LAP(+), and GARP(+) T cells. Upon Ag presentation, β-glucan-exposed dendritic cells induced a significant increase in Foxp3(+) and LAP(+) T cells in in vitro cultures. Furthermore, systemic coadministration of β-glucan plus pancreatic β cell Ag resulted in an enhanced protection of NOD mice from T1D as compared with treatment with β-glucan alone. These observations demonstrate that the innate immune response induced by low-dose β-glucan is regulatory in nature and can be exploited to modulate T cell response to β cell Ag for inducing an effective protection from T1D.

A novel pancreatic β-cell targeting bispecific-antibody (BsAb) can prevent the development of type 1 diabetes in NOD mice

To prepare a novel Bispecific Antibody (BsAb) as a potential targeted therapy for T1D, we produced a "functionally inert" monoclonal antibody (mAb) against Glucose transporter-2 (GLUT-2) expressed on β-cells to serve as an anchoring antibody. The therapeutic arm is an agonistic mAb against Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4), a negative regulator of T-cell activation expressed on activated CD4+ T-cells. A BsAb was prepared by chemically coupling an anti-GLUT2 mAb to an agonistic anti-CTLA-4 mAb. This BsAb was able to bind to GLUT2 and CTLA-4 in vitro, and to pancreatic islets, both in vitro and in vivo. We tested the safety and efficacy of this BsAb by treating Non-Obese Diabetes (NOD) mice and found that it could delay the onset of diabetes with no apparent undesirable side effects. Thus, engagement of CTLA-4 on activated T cells from target tissue can be an effective way to treat type-1 diabetes.

pH of drinking water influences the composition of gut microbiome and type 1 diabetes incidence

Nonobese diabetic (NOD) mice spontaneously develop type 1 diabetes (T1D), progression of which is similar to that in humans, and therefore are widely used as a model for understanding the immunological basis of this disease. The incidence of T1D in NOD mice is influenced by the degree of cleanliness of the mouse colony and the gut microflora. In this report, we show that the T1D incidence and rate of disease progression are profoundly influenced by the pH of drinking water, which also affects the composition and diversity of commensal bacteria in the gut. Female NOD mice that were maintained on acidic pH water (AW) developed insulitis and hyperglycemia rapidly compared with those on neutral pH water (NW). Interestingly, forced dysbiosis by segmented filamentous bacteria (SFB)-positive fecal transfer significantly suppressed the insulitis and T1D incidence in mice that were on AW but not in those on NW. The 16S rDNA-targeted pyrosequencing revealed a significant change in the composition and diversity of gut flora when the pH of drinking water was altered. Importantly, autoantigen-specific T-cell frequencies in the periphery and proinflammatory cytokine response in the intestinal mucosa are significantly higher in AW-recipient mice compared with their NW counterparts. These observations suggest that pH of drinking water affects the composition of gut microflora, leading to an altered autoimmune response and T1D incidence in NOD mice.

Dendritic cell subsets in type 1 diabetes: friend or foe?

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease characterized by immune mediated destruction of the insulin-producing β cells in the islets of Langerhans. Dendritic cells (DC) have been implicated in the pathogenesis of T1D and are also used as immunotherapeutic agents. Plasmacytoid (p)DC have been shown to have both protective and pathogenic effects and a newly described merocytic DC population has been shown to break tolerance in the mouse model of T1D, the non-obese diabetic (NOD) mouse. We have used DC populations to prevent the onset of T1D in NOD mice and clinical trials of DC therapy in T1D diabetes have been initiated. In this review we will critically examine the recent published literature on the role of DC subsets in the induction and regulation of the autoimmune response in T1D.

Induction of CD152 (CTLA-4) and LAP (TGF-β1) in human Foxp3- CD4+ CD25- T cells modulates TLR-4 induced TNF-α production

CD152 (CTLA-4) is a co-stimulatory molecule that is expressed by T cells and negatively regulates immune responses. Here, we report the identification of a novel ligand, GPC(81-95), with the ability to induce both CD152 and LAP (TGF-β1) on human Foxp3(-) CD25(-) CD4(+) T cells. The results demonstrate that GPC(81-95) peptide-induced cell surface CD152 is endocytosed back into the cell during stimulation. The protein export and exocytosis of CD152 is also induced by this ligand. The inhibitory effects of GPC(81-95) on LPS-induced TNF-α production was shown to be closely associated with its ability to induce both LAP (TGF-β1) and CD152. Taken together, we have shown that a novel peptide ligand stimulates LAP (TGF-β1) and CD152 expression on resting CD4 T cells and have demonstrated that GPC(81-95) is a useful tool to study the functional properties of LAP (TGF-β1)(+) CD152(+) CD4(+) T cells.

Functional specialization of islet dendritic cell subsets

Dendritic cells (DC) play important roles in both tolerance and immunity to β cells in type 1 diabetes. How and why DC can have diverse and opposing functions in islets remains elusive. To answer these questions, islet DC subsets and their specialized functions were characterized. Under both homeostatic and inflammatory conditions, there were two main tissue-resident DC subsets in islets, defined as CD11b(lo/-)CD103(+)CX3CR1(-) (CD103(+) DC), the majority of which were derived from fms-like tyrosine kinase 3-dependent pre-DC, and CD11b(+)CD103(-)CX3CR1(+) (CD11b(+) DC), the majority of which were derived from monocytes. CD103(+) DC were the major migratory DC and cross-presented islet-derived Ag in the pancreatic draining lymph node, although this DC subset displayed limited phagocytic activity. CD11b(+) DC were numerically the predominant subset (60-80%) but poorly migrated to the draining lymph node. Although CD11b(+) DC had greater phagocytic activity, they poorly presented Ag to T cells. CD11b(+) DC increased in numbers and percentage during T cell-mediated insulitis, suggesting that this subset might be involved in the pathogenesis of diabetes. These data elucidate the phenotype and function of homeostatic and inflammatory islet DC, suggesting differential roles in islet immunity.