Bridge between type 1 diabetes in mouse and man

Chimeric Antigen Receptor (CAR)-Based Cell Therapy for Type 1 Diabetes Mellitus (T1DM); Current Progress and Future Approaches

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that destroys insulin-producing pancreatic β-cells. Insulin replacement therapy is currently the mainstay of treatment for T1DM; however, treatment with insulin does not ameliorate disease progression, as dysregulated immune response and inflammation continue to cause further pancreatic β-cell degradation. Therefore, shifting therapeutic strategies toward immunomodulating approaches could be effective to prevent and reverse disease progression. Different immune-modulatory therapies could be used, e.g., monoclonal-based immunotherapy, mesenchymal stem cell, and immune cell therapy. Since immune-modulatory approaches could have a systemic effect on the immune system and cause toxicity, more specific treatment options should target the immune response against pancreatic β-cells. In this regard, chimeric antigen receptor (CAR)-based immunotherapy could be a promising candidate for modulation of dysregulated immune function in T1DM. CAR-based therapy has previously been approved for a number of hematologic malignancies. Nevertheless, there is renewed interest in CAR T cells' " off-the-shelf " treatment for T1DM. Several pre-clinical studies demonstrated that redirecting antigen-specific CAR T cells, especially regulatory CAR T cells (CAR Tregs), toward the pancreatic β-cells, could prevent diabetes onset and progression in diabetic mice models. Here, we aim to review the current progress of CAR-based immune-cell therapy for T1DM and the corresponding challenges, with a special focus on designing CAR-based immunomodulatory strategies to improve its efficacy in the treatment of T1DM.

Rational Engineering of Islet Tolerance via Biomaterial-Mediated Immune Modulation

Type 1 diabetes (T1D) onset is characterized by an autoimmune attack on β islet cells within the pancreas, preventing the insulin secretion required to maintain glucose homeostasis. Targeted modulation of key immunoregulatory cell populations is a promising strategy to restore tolerance to β cells. This strategy can be used to prevent T1D onset or reverse T1D with transplanted islets. To this end, drug delivery systems can be employed to transport immunomodulatory cargo to specific cell populations that inhibit autoreactive T cell-mediated destruction of the β cell mass. The rational engineering of biomaterials into nanoscale and microscale drug carriers can facilitate targeted interactions with immune cells. The physicochemical properties of the biomaterial, the delivered immunomodulatory agent, and the target cell populations are critical variables in the design of these delivery systems. In this review, we discuss recent biomaterials-based drug delivery approaches to induce islet tolerance and the need to consider both immune and metabolic markers of disease progression.

T1D patient-derived hematopoietic stem cells are programmed to generate Tph, Tfh, and autoimmunity-associated B cell subsets in human immune system mice

Interactions between B cells and CD4⁺ T cells play a central role in the development of Type 1 Diabetes (T1D). Two helper cell subsets, follicular (Tfh) and peripheral (Tph) helper T cells, are increased in patients with T1D but their role in driving B cell autoimmunity is undefined. We used a personalized immune (PI) mouse model to generate human immune systems de novo from hematopoietic stem cells (HSCs) of patients with T1D or from healthy controls (HCs). Both groups developed Tfh and Tph-like cells, and those with T1D-derived immune systems demonstrated increased numbers of Tph-like and Tfh cells compared to HC-derived PI mice. T1D-derived immune systems included increased proportions of unconventional memory CD27^-IgD^- B cells and reduced proportions of naïve B cells compared to HC PI mice, resembling changes reported for patients with systemic lupus erythematosus. Our findings suggest that T1D HSCs are genetically programmed to produce increased proportions of T cells that promote the development of unconventional, possibly autoreactive memory B cells. PI mice provide an avenue for further understanding of the immune abnormalities that drive autoantibody pathogenesis and T1D.

Harnessing CD8+ T-cell exhaustion to treat type 1 diabetes

Although immune interventions have shown great promise in type 1 diabetes mellitus (T1D) clinical trials, none are yet in routine clinical use or able to achieve insulin independence in patients. In addition to this, the principles of T1D treatment remain essentially unchanged since the isolation of insulin, almost a century ago. T1D is characterized by insulin deficiency as a result of destruction of insulin-producing beta cells mediated by autoreactive T cells. Therapies that target beta-cell antigen-specific T cells are needed to prevent T1D. CD8⁺ T-cell exhaustion is an emerging area of research in chronic infection, cancer immunotherapy, and more recently, autoimmunity. Recent data suggest that exhausted T-cell populations are associated with improved markers of T1D. T-cell exhaustion is both characterized and mediated by inhibitory receptors. This review aims to identify which inhibitory receptors may prove useful to induce T-cell exhaustion to treat T1D and identify limitations and gaps in the current literature.

Haploidentical mixed chimerism cures autoimmunity in established type 1 diabetic mice

Clinical trials are currently testing whether induction of haploidentical mixed chimerism (Haplo-MC) induces organ transplantation tolerance. Whether Haplo-MC can be used to treat established autoimmune diseases remains unknown. Here, we show that established autoimmunity in euthymic and adult-thymectomized NOD (H-2g7) mice was cured by induction of Haplo-MC under a non-myeloablative anti-thymocyte globulin-based conditioning regimen and infusion of CD4+ T cell-depleted hematopoietic graft from H-2b/g7 F1 donors that expressed autoimmune-resistant H-2b or from H-2s/g7 F1 donors that expressed autoimmune-susceptible H-2s. The cure was associated with enhanced thymic negative selection, increased thymic Treg (tTreg) production, and anergy or exhaustion of residual host-type autoreactive T cells in the periphery. The peripheral tolerance was accompanied by expansion of donor- and host-type CD62L-Helios+ tTregs as well as host-type Helios-Nrp1+ peripheral Tregs (pTregs) and PD-L1hi plasmacytoid DCs (pDCs). Depletion of donor- or host-type Tregs led to reduction of host-type PD-L1hi pDCs and recurrence of autoimmunity, whereas PD-L1 deficiency in host-type DCs led to reduction of host-type pDCs and Helios-Nrp1+ pTregs. Thus, induction of Haplo-MC reestablished both central and peripheral tolerance through mechanisms that depend on allo-MHC+ donor-type DCs, PD-L1hi host-type DCs, and the generation and persistence of donor- and host-type tTregs and pTregs.

MHC-mismatched mixed chimerism restores peripheral tolerance of noncross-reactive autoreactive T cells in NOD mice

Mixed chimerism has shown good potential to cure some autoimmune diseases and prevent tissue rejection. It is known that MHC-mismatched but not -matched mixed chimerism effectively tolerizes autoreactive T cells, even those noncross-reactive T cells that do not directly recognize donor-type antigen presenting cells [i.e., dendritic cells (DCs)]. How this is accomplished remains unknown. These studies have shown that tolerizing peripheral residual host-type noncross-reactive autoreactive T cells requires engraftment of donor-type DCs and involves a host-type DC-mediated increase in donor-type Treg cells, which associates with restoration of tolerogenic features of host-type plasmacytoid DCs and expansion of host-type Treg cells. This study suggests a previously unrecognized tolerance network among donor- and host-type DCs and Treg cells in MHC-mismatched mixed chimeras.

Autoimmune type 1 diabetes (T1D) and other autoimmune diseases are associated with particular MHC haplotypes and expansion of autoreactive T cells. Induction of MHC-mismatched but not -matched mixed chimerism by hematopoietic cell transplantation effectively reverses autoimmunity in diabetic nonobese diabetic (NOD) mice, even those with established diabetes. As expected, MHC-mismatched mixed chimerism mediates deletion in the thymus of host-type autoreactive T cells that have T-cell receptor (TCR) recognizing (cross-reacting with) donor-type antigen presenting cells (APCs), which have come to reside in the thymus. However, how MHC-mismatched mixed chimerism tolerizes host autoreactive T cells that recognize only self-MHC–peptide complexes remains unknown. Here, using NOD.Rag1^−/−.BDC2.5 or NOD.Rag1^−/−.BDC12-4.1 mice that have only noncross-reactive transgenic autoreactive T cells, we show that induction of MHC-mismatched but not -matched mixed chimerism restores immune tolerance of peripheral noncross-reactive autoreactive T cells. MHC-mismatched mixed chimerism results in increased percentages of both donor- and host-type Foxp3⁺ Treg cells and up-regulated expression of programmed death-ligand 1 (PD-L1) by host-type plasmacytoid dendritic cells (pDCs). Furthermore, adoptive transfer experiments showed that engraftment of donor-type dendritic cells (DCs) and expansion of donor-type Treg cells are required for tolerizing the noncross-reactive autoreactive T cells in the periphery, which are in association with up-regulation of host-type DC expression of PD-L1 and increased percentage of host-type Treg cells. Thus, induction of MHC-mismatched mixed chimerism may establish a peripheral tolerogenic DC and Treg network that actively tolerizes autoreactive T cells, even those with no TCR recognition of the donor APCs.