Insulin-like Growth Factor-1 Synergizes with IL-2 to Induce Homeostatic Proliferation of Regulatory T Cells.

IL-2 has been proposed to restore tolerance via regulatory T cell (Treg) expansion in autoimmunity, yet off-target effects necessitate identification of a combinatorial approach allowing for lower IL-2 dosing. We recently reported reduced levels of immunoregulatory insulin-like growth factor-1 (IGF1) during type 1 diabetes progression. Thus, we hypothesized that IGF1 would synergize with IL-2 to expand Tregs. We observed IGF1 receptor was elevated on murine memory and human naive Treg subsets. IL-2 and IGF1 promoted PI3K/Akt signaling in Tregs, inducing thymically-derived Treg expansion beyond either agent alone in NOD mice. Increased populations of murine Tregs of naive or memory, as well as CD5lo polyclonal or CD5hi likely self-reactive, status were also observed. Expansion was attributed to increased IL-2Rγ subunit expression on murine Tregs exposed to IL-2 and IGF1 as compared with IL-2 or IGF1 alone. Assessing translational capacity, incubation of naive human CD4+ T cells with IL-2 and IGF1 enhanced thymically-derived Treg proliferation in vitro, without the need for TCR ligation. We then demonstrated that IGF1 and IL-2 or IL-7, which is also IL-2Rγ-chain dependent, can be used to induce proliferation of genetically engineered naive human Tregs or T conventional cells, respectively. These data support the potential use of IGF1 in combination with common γ-chain cytokines to drive homeostatic T cell expansion, both in vitro and in vivo, for cellular therapeutics and ex vivo gene editing.

Guidelines for standardizing T-cell cytometry assays to link biomarkers, mechanisms, and disease outcomes in type 1 diabetes.

Cytometric immunophenotyping is a powerful tool to discover and implement T-cell biomarkers of type 1 diabetes (T1D) progression and response to clinical therapy. Although many discovery-based T-cell biomarkers have been described, to date, no such markers have been widely adopted in standard practice. The heterogeneous nature of T1D and lack of standardized assays and experimental design across studies is a major barrier to the broader adoption of T-cell immunophenotyping assays. There is an unmet need to harmonize the design of immunophenotyping assays, including those that measure antigen-agnostic cell populations, such that data collected from different clinical trial sites and T1D cohorts are comparable, yet account for cohort-specific features and different drug mechanisms of action. In these Guidelines, we aim to provide expert advice on how to unify aspects of study design and practice. We provide recommendations for defining cohorts, method implementation, as well as tools for data analysis and reporting by highlighting and building on selected successes. Harmonization of cytometry-based T-cell assays will allow researchers to better integrate findings across trials, ultimately enabling the identification and validation of biomarkers of disease progression and treatment response in T1D.

Altered cellular localisation and expression, together with unconventional protein trafficking, of prion protein, PrPC, in type 1 diabetes.

AIMS/HYPOTHESIS: Normal cellular prion protein (PrPC) is a conserved mammalian glycoprotein found on the outer plasma membrane leaflet through a glycophosphatidylinositol anchor. Although PrPC is expressed by a wide range of tissues throughout the body, the complete repertoire of its functions has not been fully determined. The misfolded pathogenic isoform PrPSc (the scrapie form of PrP) is a causative agent of neurodegenerative prion diseases. The aim of this study is to evaluate PrPC localisation, expression and trafficking in pancreases from organ donors with and without type 1 diabetes and to infer PrPC function through studies on interacting protein partners. METHODS: In order to evaluate localisation and trafficking of PrPC in the human pancreas, 12 non-diabetic, 12 type 1 diabetic and 12 autoantibody-positive organ donor tissue samples were analysed using immunofluorescence analysis. Furthermore, total RNA was isolated from 29 non-diabetic, 29 type 1 diabetic and 24 autoantibody-positive donors to estimate PrPC expression in the human pancreas. Additionally, we performed PrPC-specific immunoblot analysis on total pancreatic protein from non-diabetic and type 1 diabetic organ donors to test whether changes in PrPC mRNA levels leads to a concomitant increase in PrPC protein levels in human pancreases. RESULTS: In non-diabetic and type 1 diabetic pancreases (the latter displaying both insulin-positive [INS(+)] and -negative [INS(-)] islets), we found PrPC in islets co-registering with beta cells in all INS(+) islets and, strikingly, unexpected activation of PrPC in alpha cells within diabetic INS(-) islets. We found PrPC localised to the plasma membrane and endoplasmic reticulum (ER) but not the Golgi, defining two cellular pools and an unconventional protein trafficking mechanism bypassing the Golgi. We demonstrate PrPC co-registration with established protein partners, neural cell adhesion molecule 1 (NCAM1) and stress-inducible phosphoprotein 1 (STI1; encoded by STIP1) on the plasma membrane and ER, respectively, linking PrPC function with cyto-protection, signalling, differentiation and morphogenesis. We demonstrate that both PRNP (encoding PrPC) and STIP1 gene expression are dramatically altered in type 1 diabetic and autoantibody-positive pancreases. CONCLUSIONS/INTERPRETATION: As the first study to address PrPC expression in non-diabetic and type 1 diabetic human pancreas, we provide new insights for PrPC in the pathogenesis of type 1 diabetes. We evaluated the cell-type specific expression of PrPC in the human pancreas and discovered possible connections with potential interacting proteins that we speculate might address mechanisms relevant to the role of PrPC in the human pancreas.

De-coding genetic risk variants in type 1 diabetes.

The conceptual basis for a genetic predisposition underlying the risk for developing type 1 diabetes (T1D) predates modern human molecular genetics. Over half of the genetic risk has been attributed to the human leukocyte antigen (HLA) class II gene region and to the insulin (INS) gene locus - both thought to confer direction of autoreactivity and tissue specificity. Notwithstanding, questions still remain regarding the functional contributions of a vast array of minor polygenic risk variants scattered throughout the genome that likely influence disease heterogeneity and clinical outcomes. Herein, we summarize the available literature related to the T1D-associated coding variants defined at the time of this review, for the genes PTPN22, IFIH1, SH2B3, CD226, TYK2, FUT2, SIRPG, CTLA4, CTSH and UBASH3A. Data from genotype-selected human cohorts are summarized, and studies from the non-obese diabetic (NOD) mouse are presented to describe the functional impact of these variants in relation to innate and adaptive immunity as well as to ß-cell fragility, with expression profiles in tissues and peripheral blood highlighted. The contribution of each variant to progression through T1D staging, including environmental interactions, are discussed with consideration of how their respective protein products may serve as attractive targets for precision medicine-based therapeutics to prevent or suspend the development of T1D.

Innate inflammation drives NK cell activation to impair Treg activity.

IL-12 and IL-18 synergize to promote TH1 responses and have been implicated as accelerators of autoimmune pathogenesis in type 1 diabetes (T1D). We investigated the influence of these cytokines on immune cells involved in human T1D progression: natural killer (NK) cells, regulatory T cells (Tregs), and cytotoxic T lymphocytes (CTL). NK cells from T1D patients exhibited higher surface CD226 versus controls and lower CD25 compared to first-degree relatives and controls. Changes in NK cell phenotype towards terminal differentiation were associated with cytomegalovirus (CMV) seropositivity, while possession of IL18RAP, IFIH1, and IL2RA T1D-risk variants impacted NK cell activation as evaluated by immuno-expression quantitative trait loci (eQTL) analyses. IL-12 and IL-18 stimulated NK cells from healthy donors exhibited enhanced specific killing of myelogenous K562 target cells. Moreover, activated NK cells increased expression of NKG2A, NKG2D, CD226, TIGIT and CD25, which enabled competition for IL-2 upon co-culture with Tregs, resulting in Treg downregulation of FOXP3, production of IFNγ, and loss of suppressive function. We generated islet-autoreactive CTL "avatars", which upon exposure to IL-12 and IL-18, upregulated IFNγ and Granzyme-B leading to increased lymphocytotoxicity of a human ß-cell line in vitro. These results support a model for T1D pathogenesis wherein IL-12 and IL-18 synergistically enhance CTL and NK cell cytotoxic activity and disrupt immunoregulation by Tregs.

Immune Mechanisms and Pathways Targeted in Type 1 Diabetes.

PURPOSE OF REVIEW: The immunosuppressive agent cyclosporine was first reported to lower daily insulin dose and improve glycemic control in patients with new-onset type 1 diabetes (T1D) in 1984. While renal toxicity limited cyclosporine's extended use, this observation ignited collaborative efforts to identify immunotherapeutic agents capable of safely preserving ß cells in patients with or at risk for T1D. RECENT FINDINGS: Advances in T1D prediction and early diagnosis, together with expanded knowledge of the disease mechanisms, have facilitated trials targeting specific immune cell subsets, autoantigens, and pathways. In addition, clinical responder and non-responder subsets have been defined through the use of metabolic and immunological readouts. Herein, we review emerging T1D biomarkers within the context of recent and ongoing T1D immunotherapy trials. We also discuss responder/non-responder analyses in an effort to identify therapeutic mechanisms, define actionable pathways, and guide subject selection, drug dosing, and tailored combination drug therapy for future T1D trials.

Impaired islet function and normal exocrine enzyme secretion occur with low inter-regional variation in type 1 diabetes.

Histopathological heterogeneity in the human pancreas is well documented; however, functional evidence at the tissue level is scarce. Herein, we investigate in situ glucose-stimulated islet and carbachol-stimulated acinar cell secretion across the pancreas head (PH), body (PB), and tail (PT) regions in donors without diabetes (ND; n = 15), positive for one islet autoantibody (1AAb+; n = 7), and with type 1 diabetes (T1D; <14 months duration, n = 5). Insulin, glucagon, pancreatic amylase, lipase, and trypsinogen secretion along with 3D tissue morphometrical features are comparable across regions in ND. In T1D, insulin secretion and beta-cell volume are significantly reduced within all regions, while glucagon and enzymes are unaltered. Beta-cell volume is lower despite normal insulin secretion in 1AAb+, resulting in increased volume-adjusted insulin secretion versus ND. Islet and acinar cell secretion in 1AAb+ are consistent across the PH, PB, and PT. This study supports low inter-regional variation in pancreas slice function and, potentially, increased metabolic demand in 1AAb+.

Impaired islet function with normal exocrine enzyme secretion is consistent across the head, body, and tail pancreas regions in type 1 diabetes.

Histopathological heterogeneity in human pancreas has been well documented; however, functional evidence at the tissue level is scarce. Herein we investigated in situ glucose-stimulated islet and carbachol-stimulated acinar cell secretion across the pancreas head (PH), body (PB), and tail (PT) regions in no diabetes (ND, n=15), single islet autoantibody-positive (1AAb+, n=7), and type 1 diabetes donors (T1D, <14 months duration, n=5). Insulin, glucagon, pancreatic amylase, lipase, and trypsinogen secretion along with 3D tissue morphometrical features were comparable across the regions in ND. In T1D, insulin secretion and beta-cell volume were significantly reduced within all regions, while glucagon and enzymes were unaltered. Beta-cell volume was lower despite normal insulin secretion in 1AAb+, resulting in increased volume-adjusted insulin secretion versus ND. Islet and acinar cell secretion in 1AAb+ were consistent across PH, PB and PT. This study supports low inter-regional variation in pancreas slice function and potentially, increased metabolic demand in 1AAb+.

Inhibition of CD226 Co-Stimulation Suppresses Diabetes Development in the NOD Mouse by Augmenting Tregs and Diminishing Effector T Cell Function.

Aims/hypothesis: Immunotherapeutics targeting T cells are crucial for inhibiting autoimmune disease progression proximal to disease onset in type 1 diabetes. A growing number of T cell-directed therapeutics have demonstrated partial therapeutic efficacy, with anti-CD3 (α-CD3) representing the only regulatory agency-approved drug capable of slowing disease progression through a mechanism involving the induction of partial T cell exhaustion. There is an outstanding need to augment the durability and effectiveness of T cell targeting by directly restraining proinflammatory T helper type 1 (Th1) and type 1 cytotoxic CD8+ T cell (Tc1) subsets, while simultaneously augmenting regulatory T cell (Treg) activity. Here, we present a novel strategy for reducing diabetes incidence in the NOD mouse model using a blocking monoclonal antibody targeting the type 1 diabetes-risk associated T cell co-stimulatory receptor, CD226. Methods: Female NOD mice were treated with anti-CD226 between 7-8 weeks of age and then monitored for diabetes incidence and therapeutic mechanism of action. Results: Compared to isotype-treated controls, anti-CD226 treated NOD mice showed reduced insulitis severity at 12 weeks and decreased disease incidence at 30 weeks. Flow cytometric analysis performed five weeks post-treatment demonstrated reduced proliferation of CD4+ and CD8+ effector memory T cells in spleens of anti-CD226 treated mice. Phenotyping of pancreatic Tregs revealed increased CD25 expression and STAT5 phosphorylation following anti-CD226, with splenic Tregs displaying augmented suppression of CD4+ T cell responders in vitro. Anti-CD226 treated mice exhibited reduced frequencies of islet-specific glucose-6-phosphatase catalytic subunit related protein (IGRP)-reactive CD8+ T cells in the pancreas, using both ex vivo tetramer staining and single-cell T cell receptor sequencing (scTCR-seq) approaches. 51Cr-release assays demonstrated reduced cell-mediated lysis of beta-cells by anti-CD226-treated autoreactive cytotoxic T lymphocytes. Conclusions/interpretation: CD226 blockade reduces T cell cytotoxicity and improves Treg function, representing a targeted and rational approach for restoring immune regulation in type 1 diabetes.

Biomaterials-based nanoparticles conjugated to regulatory T cells provide a modular system for localized delivery of pharmacotherapeutic agents.

Type 1 diabetes (T1D) presents with two therapeutic challenges: the need to correct underlying autoimmunity and restore ß-cell mass. We harnessed the unique capacity of regulatory T cells (Tregs) and the T cell receptor (TCR) to direct tolerance induction along with tissue-localized delivery of therapeutic agents to restore endogenous ß-cell function. Specifically, we designed a combinatorial therapy involving biomaterials-based poly(lactic-co-glycolic acid) nanoparticles co-loaded with the Treg growth factor, IL-2, and the ß-cell regenerative agent, harmine (a tyrosine-regulated kinase 1A [DYRK1A] inhibitor), conjugated to the surface of Tregs. We observed continuous elution of IL-2 and harmine from nanoparticles for at least 7 days in vitro. When conjugated to primary human Tregs, IL-2 nanoparticles provided sufficient IL-2 receptor signaling to support STAT5 phosphorylation for sustained phenotypic stability and viability in culture. Inclusion of poly-L-lysine (PLL) during nanoparticle-cell coupling dramatically increased conjugation efficiency, providing sufficient IL-2 to support in vitro proliferation of IL-2-dependent CTLL-2 cells and primary murine Tregs. In 12-week-old female non-obese diabetic mice, adoptive transfer of IL-2/harmine nanoparticle-conjugated NOD.BDC2.5 Tregs, which express an islet antigen-specific TCR, significantly prevented diabetes demonstrating preserved in vivo viability. These data provide the preclinical basis to develop a biomaterials-optimized cellular therapy to restore immune tolerance and promote ß-cell proliferation in T1D through receptor-targeted drug delivery within pancreatic islets.

Modeling cell-mediated immunity in human type 1 diabetes by engineering autoreactive CD8+ T cells.

The autoimmune pathogenesis of type 1 diabetes (T1D) involves cellular infiltration from innate and adaptive immune subsets into the islets of Langerhans within the pancreas; however, the direct cytotoxic killing of insulin-producing ß-cells is thought to be mediated primarily by antigen-specific CD8+ T cells. Despite this direct pathogenic role, key aspects of their receptor specificity and function remain uncharacterized, in part, due to their low precursor frequency in peripheral blood. The concept of engineering human T cell specificity, using T cell receptor (TCR) and chimeric antigen receptor (CAR)-based approaches, has been demonstrated to improve adoptive cell therapies for cancer, but has yet to be extensively employed for modeling and treating autoimmunity. To address this limitation, we sought to combine targeted genome editing of the endogenous TCRα chain gene (TRAC) via CRISPR/Cas9 in combination with lentiviral vector (LV)-mediated TCR gene transfer into primary human CD8+ T cells. We observed that knockout (KO) of endogenous TRAC enhanced de novo TCR pairing, which permitted increased peptide:MHC-dextramer staining. Moreover, TRAC KO and TCR gene transfer increased markers of activation and effector function following activation, including granzyme B and interferon-γ production. Importantly, we observed increased cytotoxicity toward an HLA-A*0201+ human ß-cell line by HLA-A*02:01 restricted CD8+ T cells engineered to recognize islet-specific glucose-6-phosphatase catalytic subunit (IGRP). These data support the notion of altering the specificity of primary human T cells for mechanistic analyses of autoreactive antigen-specific CD8+ T cells and are expected to facilitate downstream cellular therapeutics to achieve tolerance induction through the generation of antigen-specific regulatory T cells.

Divergent metabolic phenotypes in two genetic syndromes of low insulin secretion.

AIMS: We examined the effect of growth hormone (GH) counter-regulation on carbohydrate metabolism in individuals with life-long diminished insulin secretion (DIS). METHODS: Adults homozygous for the E180 splice site mutation of GHR [Laron syndrome (LS)], adults with a gain-of-function mutation in CDKN1c [Guevara-Rosenbloom syndrome (GRS)], and controls were evaluated for body composition, leptin, total and high molecular weight (HMW) adiponectin, insulin-like growth factor (IGF) axis molecules, and a 5-hour oral glucose tolerance test (OGTT), with measurements of glucose, insulin, glucagon, ghrelin, pancreatic polypeptide, gastric inhibitory peptide, glucagon-like peptide-1, peptide YY, and islet amyloid polypeptide (IAPP). RESULTS: Both syndromic cohorts displayed DIS during OGTT. LS subjects had higher serum concentrations of total and HMW adiponectin, and lower levels of IGF-I, IGF-II, and IGF-Binding Protein-3 than individuals in other study groups. Furthermore, they displayed normal glycemic responses during OGTT with the lowest IAPP secretion. In contrast, individuals with GRS had higher levels of protein glycation, deficient glucose control during OGTT, and increased secretion of IAPP. CONCLUSIONS: A distinct metabolic phenotype depending on GH counter-regulatory status, associates with diabetes development and excess glucose-induced IAPP secretion.

Treg-Specific CD226 Deletion Reduces Diabetes Incidence in NOD Mice by Improving Regulatory T-Cell Stability.

Costimulation serves as a critical checkpoint for T-cell activation, and several genetic variants affecting costimulatory pathways confer risk for autoimmune diseases. A single nucleotide polymorphism (rs763361) in the CD226 gene encoding a costimulatory receptor increases susceptibility to multiple autoimmune diseases, including type 1 diabetes. We previously found that Cd226 knockout protected NOD mice from disease, but the impact of CD226 on individual immune subsets remained unclear. Our prior reports implicate regulatory T cells (Tregs), as human CD226+ Tregs exhibit reduced suppressive function. Hence, we hypothesized that genomic Cd226 gene deletion would increase Treg stability and that Treg-specific Cd226 deletion would inhibit diabetes in NOD mice. Indeed, crossing NOD.Cd226-/- and a NOD Treg-lineage tracing strain resulted in decreased pancreatic Foxp3-deficient "ex-Tregs." We generated a novel Treg-conditional knockout (TregΔCd226) strain that displayed decreased insulitis and diabetes incidence. CD226-deficient pancreatic Tregs had increased expression of the coinhibitory counter-receptor T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT). Moreover, NOD splenocytes treated with TIGIT-Fc fusion protein exhibited reduced T-cell proliferation and interferon-γ production following anti-CD3/CD28 stimulation. This study demonstrates that a CD226/TIGIT imbalance contributes to Treg instability in NOD mice and highlights the potential for therapeutic targeting this costimulatory pathway to halt autoimmunity.

Human immune phenotyping reveals accelerated aging in type 1 diabetes.

The proportions and phenotypes of immune cell subsets in peripheral blood undergo continual and dramatic remodeling throughout the human life span, which complicates efforts to identify disease-associated immune signatures in type 1 diabetes (T1D). We conducted cross-sectional flow cytometric immune profiling on peripheral blood from 826 individuals (stage 3 T1D, their first-degree relatives, those with ≥2 islet autoantibodies, and autoantibody-negative unaffected controls). We constructed an immune age predictive model in unaffected participants and observed accelerated immune aging in T1D. We used generalized additive models for location, shape, and scale to obtain age-corrected data for flow cytometry and complete blood count readouts, which can be visualized in our interactive portal (ImmScape); 46 parameters were significantly associated with age only, 25 with T1D only, and 23 with both age and T1D. Phenotypes associated with accelerated immunological aging in T1D included increased CXCR3+ and programmed cell death 1-positive (PD-1+) frequencies in naive and memory T cell subsets, despite reduced PD-1 expression levels on memory T cells. Phenotypes associated with T1D after age correction were predictive of T1D status. Our findings demonstrate advanced immune aging in T1D and highlight disease-associated phenotypes for biomarker monitoring and therapeutic interventions.

A genomic data archive from the Network for Pancreatic Organ donors with Diabetes.

The Network for Pancreatic Organ donors with Diabetes (nPOD) is the largest biorepository of human pancreata and associated immune organs from donors with type 1 diabetes (T1D), maturity-onset diabetes of the young (MODY), cystic fibrosis-related diabetes (CFRD), type 2 diabetes (T2D), gestational diabetes, islet autoantibody positivity (AAb+), and without diabetes. nPOD recovers, processes, analyzes, and distributes high-quality biospecimens, collected using optimized standard operating procedures, and associated de-identified data/metadata to researchers around the world. Herein describes the release of high-parameter genotyping data from this collection. 372 donors were genotyped using a custom precision medicine single nucleotide polymorphism (SNP) microarray. Data were technically validated using published algorithms to evaluate donor relatedness, ancestry, imputed HLA, and T1D genetic risk score. Additionally, 207 donors were assessed for rare known and novel coding region variants via whole exome sequencing (WES). These data are publicly-available to enable genotype-specific sample requests and the study of novel genotype:phenotype associations, aiding in the mission of nPOD to enhance understanding of diabetes pathogenesis to promote the development of novel therapies.

Exocrine and Endocrine Inflammation Increases Cellular Replication in the Pancreatic Duct Compartment in Type 1 Diabetes.

Context: We recently demonstrated increased cellular proliferation in the pancreatic ductal gland (PDG) compartment of organ donors with type 1 diabetes, suggesting that PDGs may harbor progenitor cells capable of pancreatic regeneration. Objective: We evaluated the impact of diabetes and pancreatic inflammation on PDG and interlobular duct (ILD) cellular proliferation and profiles. Methods: Endocrine hormone expression (insulin, glucagon, somatostatin, pancreatic polypeptide) and proliferating Ki67+ cells were localized within the PDG and ILD compartments by multicolor immunohistochemistry in cross-sections from the head, body, and tail regions of pancreata from those with (n = 31) or without type 1 diabetes (n = 43). Whole-slide scanned images were analyzed using digital pathology. Results: Type 1 diabetes donors with insulitis or histologically identified pancreatitis had increased cellular replication in the ILD and PDG compartments. Interestingly, while cellular proliferation within the pancreatic ductal tree was significantly increased in type 1 diabetes (PDG mean = 3.36%, SEM = 1.06; ILD mean = 2.78%, SEM = 0.97) vs nondiabetes(ND) subjects without pancreatic inflammation (PDG mean = 1.18%, SEM = 0.42; ILD mean = 0.74%, SEM = 0.15, P < 0.05), robust replication was also observed in ND donors with pancreatitis (PDG mean = 3.52%, SEM = 1.33; ILD mean = 2.18%, SEM = 0.54, P < 0.05). Few polyhormonal cells were present in the ILD (type 1 diabetes = 0.04 ± 0.02%; ND = 0.08 ± 0.03%, P = 0.40) or PDG compartment (type 1 diabetes = 0.02 ± 0.01%; ND = 0.08 ± 0.13%, P = 0.63). Conclusion: These data suggest that increased pancreatic ductal cell replication is associated with sustained pancreatic inflammation; however, as replicating cells were hormone-negative, PDGs do not appear to represent a compelling endogenous source of hormone-positive endocrine cells.

Incidence Trends of New-Onset Diabetes in Children and Adolescents Before and During the COVID-19 Pandemic: Findings From Florida.

This study examined the incidence trends of new-onset type 1 and type 2 diabetes in children and adolescents in Florida before and during the coronavirus disease 2019 (COVID-19) pandemic. In this observational descriptive cohort study, we used a validated computable phenotype to identify incident diabetes cases among individuals <18 years of age in the OneFlorida+ network of the national Patient-Centered Clinical Research Network between January 2017 and June 2021. We conducted an interrupted time series analysis based on the autoregressive integrated moving average model to compare changes in age-adjusted incidence rates of type 1 and type 2 diabetes before and after March 2020, when COVID-19 was declared a national health emergency in the U.S. The age-adjusted incidence rates of both type 1 and type 2 diabetes increased post-COVID-19 for children and adolescents. These results highlight the need for longitudinal cohort studies to examine how the pandemic might influence subsequent diabetes onset in young individuals.

Human CD4+CD25+CD226- Tregs Demonstrate Increased Purity, Lineage Stability, and Suppressive Capacity Versus CD4+CD25+CD127lo/- Tregs for Adoptive Cell Therapy.

Regulatory T cell (Treg) adoptive cell therapy (ACT) represents an emerging strategy for restoring immune tolerance in autoimmune diseases. Tregs are commonly purified using a CD4+CD25+CD127lo/- gating strategy, which yields a mixed population: 1) cells expressing the transcription factors, FOXP3 and Helios, that canonically define lineage stable thymic Tregs and 2) unstable FOXP3+Helios- Tregs. Our prior work identified the autoimmune disease risk-associated locus and costimulatory molecule, CD226, as being highly expressed not only on effector T cells but also, interferon-γ (IFN-γ) producing peripheral Tregs (pTreg). Thus, we sought to determine whether isolating Tregs with a CD4+CD25+CD226- strategy yields a population with increased purity and suppressive capacity relative to CD4+CD25+CD127lo/- cells. After 14d of culture, expanded CD4+CD25+CD226- cells displayed a decreased proportion of pTregs relative to CD4+CD25+CD127lo/- cells, as measured by FOXP3+Helios- expression and the epigenetic signature at the FOXP3 Treg-specific demethylated region (TSDR). Furthermore, CD226- Tregs exhibited decreased production of the effector cytokines, IFN-γ, TNF, and IL-17A, along with increased expression of the immunoregulatory cytokine, TGF-ß1. Lastly, CD226- Tregs demonstrated increased in vitro suppressive capacity as compared to their CD127lo/- counterparts. These data suggest that the exclusion of CD226-expressing cells during Treg sorting yields a population with increased purity, lineage stability, and suppressive capabilities, which may benefit Treg ACT for the treatment of autoimmune diseases.

Limited extent and consequences of pancreatic SARS-CoV-2 infection.

Concerns that infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19), may cause new-onset diabetes persist in an evolving research landscape, and precise risk assessment is hampered by, at times, conflicting evidence. Here, leveraging comprehensive single-cell analyses of in vitro SARS-CoV-2-infected human pancreatic islets, we demonstrate that productive infection is strictly dependent on the SARS-CoV-2 entry receptor ACE2 and targets practically all pancreatic cell types. Importantly, the infection remains highly circumscribed and largely non-cytopathic and, despite a high viral burden in infected subsets, promotes only modest cellular perturbations and inflammatory responses. Similar experimental outcomes are also observed after islet infection with endemic coronaviruses. Thus, the limits of pancreatic SARS-CoV-2 infection, even under in vitro conditions of enhanced virus exposure, challenge the proposition that in vivo targeting of ß cells by SARS-CoV-2 precipitates new-onset diabetes. Whether restricted pancreatic damage and immunological alterations accrued by COVID-19 increase cumulative diabetes risk, however, remains to be evaluated.

The Immunoregulatory Role of the Signal Regulatory Protein Family and CD47 Signaling Pathway in Type 1 Diabetes.

Background: The pathogenesis of type 1 diabetes (T1D) involves complex genetic susceptibility that impacts pathways regulating host immunity and the target of autoimmune attack, insulin-producing pancreatic ß-cells. Interactions between risk variants and environmental factors result in significant heterogeneity in clinical presentation among those who develop T1D. Although genetic risk is dominated by the human leukocyte antigen (HLA) class II and insulin (INS) gene loci, nearly 150 additional risk variants are significantly associated with the disease, including polymorphisms in immune checkpoint molecules, such as SIRPG. Scope of Review: In this review, we summarize the literature related to the T1D-associated risk variants in SIRPG, which include a protein-coding variant (rs6043409, G>A; A263V) and an intronic polymorphism (rs2281808, C>T), and their potential impacts on the immunoregulatory signal regulatory protein (SIRP) family:CD47 signaling axis. We discuss how dysregulated expression or function of SIRPs and CD47 in antigen-presenting cells (APCs), T cells, natural killer (NK) cells, and pancreatic ß-cells could potentially promote T1D development. Major Conclusions: We propose a hypothesis, supported by emerging genetic and functional immune studies, which states a loss of proper SIRP:CD47 signaling may result in increased lymphocyte activation and cytotoxicity and enhanced ß-cell destruction. Thus, we present several novel therapeutic strategies for modulation of SIRPs and CD47 to intervene in T1D.