Daniel B. Rainbow

NOD.c3c4 congenic mice develop autoimmune biliary disease that serologically and pathogenetically models human primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease with a strong genetic component characterized by biliary ductular inflammation with eventual liver cirrhosis. The serologic hallmark of PBC is antimitochondrial antibodies that react with the pyruvate dehydrogenase complex, targeting the inner lipoyl domain of the E2 subunit (anti–PDC-E2). Herein we demonstrate that NOD.c3c4 mice congenically derived from the nonobese diabetic strain develop an autoimmune biliary disease (ABD) that models human PBC. NOD.c3c4 (at 9–10 wk, before significant biliary pathology) develop antibodies to PDC-E2 that are specific for the inner lipoyl domain. Affected areas of biliary epithelium are infiltrated with CD3+, CD4+, and CD8+ T cells, and treatment of NOD.c3c4 mice with monoclonal antibody to CD3 protects from ABD. Furthermore, NOD.c3c4-scid mice develop disease after adoptive transfer of splenocytes or CD4+ T cells, demonstrating a central role for T cells in pathogenesis. Histological analysis reveals destructive cholangitis, granuloma formation, and eosinophilic infiltration as seen in PBC, although, unlike PBC, the extrahepatic biliary ducts are also affected. Using a congenic mapping approach, we define the first ABD (Abd) locus, Abd1. These results identify the NOD.c3c4 mouse as the first spontaneous mouse model of PBC.

Functional IL6R 358Ala Allele Impairs Classical IL-6 Receptor Signaling and Influences Risk of Diverse Inflammatory Diseases

Inflammation, which is directly regulated by interleukin-6 (IL-6) signaling, is implicated in the etiology of several chronic diseases. Although a common, non-synonymous variant in the IL-6 receptor gene (IL6R Asp358Ala; rs2228145 A>C) is associated with the risk of several common diseases, with the 358Ala allele conferring protection from coronary heart disease (CHD), rheumatoid arthritis (RA), atrial fibrillation (AF), abdominal aortic aneurysm (AAA), and increased susceptibility to asthma, the variants effect on IL-6 signaling is not known. Here we provide evidence for the association of this non-synonymous variant with the risk of type 1 diabetes (T1D) in two independent populations and confirm that rs2228145 is the major determinant of the concentration of circulating soluble IL-6R (sIL-6R) levels (34.6% increase in sIL-6R per copy of the minor allele 358Ala; rs2228145 [C]). To further investigate the molecular mechanism of this variant, we analyzed expression of IL-6R in peripheral blood mononuclear cells (PBMCs) in 128 volunteers from the Cambridge BioResource. We demonstrate that, although 358Ala increases transcription of the soluble IL6R isoform (P = 8.3×10−22) and not the membrane-bound isoform, 358Ala reduces surface expression of IL-6R on CD4+ T cells and monocytes (up to 28% reduction per allele; P≤5.6×10−22). Importantly, reduced expression of membrane-bound IL-6R resulted in impaired IL-6 responsiveness, as measured by decreased phosphorylation of the transcription factors STAT3 and STAT1 following stimulation with IL-6 (P≤5.2×10−7). Our findings elucidate the regulation of IL-6 signaling by IL-6R, which is causally relevant to several complex diseases, identify mechanisms for new approaches to target the IL-6/IL-6R axis, and anticipate differences in treatment response to IL-6 therapies based on this common IL6R variant.

Genetic Control of Autoimmunity: Protection from Diabetes, but Spontaneous Autoimmune Biliary Disease in a Nonobese Diabetic Congenic Strain

At least 20 insulin-dependent diabetes (Idd) loci modify the progression of autoimmune diabetes in the NOD mouse, an animal model of human type 1 diabetes. The NOD.c3c4 congenic mouse, which has multiple B6- and B10-derived Idd-resistant alleles on chromosomes 3 and 4, respectively, is completely protected from autoimmune diabetes. We demonstrate in this study, however, that NOD.c3c4 mice develop a novel spontaneous and fatal autoimmune polycystic biliary tract disease, with lymphocytic peribiliary infiltrates and autoantibodies. Strains having a subset of the Idd-resistant alleles present in the NOD.c3c4 strain show component phenotypes of the liver disease: NOD mice with B6 resistance alleles only on chromosome 3 have lymphocytic liver infiltration without autoantibody formation, while NOD mice with B10 resistance alleles only on chromosome 4 show autoantibody formation without liver infiltration. The liver disease is transferable to naive NOD.c3c4 recipients using splenocytes from affected NOD.c3c4 mice, demonstrating an autoimmune etiology. Thus, substitution of non-NOD genetic intervals into the NOD strain can prevent diabetes, but in turn cause an entirely different autoimmune syndrome, a finding consistent with a generalized failure of self-tolerance in the NOD genetic background. The complex clinical phenotypes in human autoimmune conditions may be similarly resolved into largely overlapping biochemical pathways that are then modified, potentially by alleles at a few key chromosomal regions, to produce specific autoimmune syndromes.

Genetic Evidence That the Differential Expression of the Ligand-Independent Isoform of CTLA-4 Is the Molecular Basis of the Idd5.1 Type 1 Diabetes Region in Nonobese Diabetic Mice

Idd5.1 regulates T1D susceptibility in nonobese diabetic (NOD) mice and has two notable candidate genes, Ctla4 and Icos. Reduced expression of one of the four CTLA-4 isoforms, ligand-independent CTLA-4 (liCTLA-4), which inhibits in vitro T cell activation and cytokine production similarly to full-length CTLA-4 (flCTLA-4), has been hypothesized to increase type 1 diabetes (T1D) susceptibility. However, further support of this hypothesis is required since the Idd5.1 haplotypes of the diabetes-susceptible NOD and the resistant B10 strains differ throughout Ctla4 and Icos. Using haplotype analysis and the generation of novel Idd5.1-congenic strains that differ at the disease-associated Ctla4 exon 2 single-nucleotide polymorphism, we demonstrate that increased expression of liCTLA-4 correlates with reduced T1D susceptibility. To directly assess the ability of liCTLA-4 to modulate T1D, we generated liCTLA-4-transgenic NOD mice and compared their diabetes susceptibility to nontransgenic littermates. NOD liCTLA-4-transgenic mice were protected from T1D to the same extent as NOD.B10 Idd5.1-congenic mice, demonstrating that increased liCTLA-4 expression alone can account for disease protection. To further investigate the in vivo function of liCTLA-4, specifically whether liCTLA-4 can functionally replace flCTLA-4 in vivo, we expressed the liCTLA-4 transgene in CTLA-4−/− B6 mice. CTLA-4−/− mice expressing liCTLA-4 accumulated fewer activated effector/memory CD4+ T cells than CTLA-4−/− mice and the transgenic mice were partially rescued from the multiorgan inflammation and early lethality caused by the disruption of Ctla4. These results suggest that liCTLA-4 can partially replace some functions of flCTLA-4 in vivo and that this isoform evolved to reinforce the function of flCTLA-4.

The Soluble CTLA-4 Splice Variant Protects From Type 1 Diabetes and Potentiates Regulatory T-Cell Function

OBJECTIVE CTLA4 gene variation associates with multiple autoimmune disorders, including type 1 diabetes. The CTLA4 susceptibility allele was found to generate decreased levels of mRNA encoding soluble CTLA-4 (sCTLA-4) relative to the full-length isoform, the functional consequence of which is as yet unknown. In this study, we investigated the contribution of sCTLA-4 to immune regulation with the aim to elucidate the functional basis of the disease association of CTLA4. RESEARCH DESIGN AND METHODS To model the disease-associated splicing variation of CTLA4, we generated NOD mice in which sCTLA-4 mRNA is silenced by RNA interference. RESULTS We found that loss of sCTLA-4 impairs the function of regulatory T (Treg) cells. This functional defect could be attributed, at least in part, to the failure of sCTLA-4 knockdown (KD) Treg cells to downregulate dendritic cell costimulation. sCTLA-4 KD Treg cells, in contrast with wild-type Treg cells, failed to inhibit colitis induced by transfer of CD4+CD45RBhi cells into NOD.SCID animals. Furthermore, diminished sCTLA-4 expression accelerated the onset of autoimmune diabetes in transgenic mice. CONCLUSIONS Our results demonstrate that sCTLA-4 participates in immune regulation by potentiating the function of Treg cells. The functional outcome of silencing this splice variant in the NOD model provides an explanation for the association of CTLA4 variation with autoimmunity. Lower sCTLA-4 expression from the susceptibility allele may directly affect the suppressive capacity of Treg cells and thereby modulate disease risk. Our unprecedented approach establishes the feasibility of modeling splicing variations relevant to autoimmunity.

Expression of Diabetes-Associated Genes by Dendritic Cells and CD4 T Cells Drives the Loss of Tolerance in Nonobese Diabetic Mice

In humans and NOD mice, defects in immune tolerance result in the spontaneous development of type-1-diabetes. Recent studies have ascribed a breakdown in tolerance to dysfunction in regulatory T cells that is secondary to reduced IL-2 production by T cells having the NOD diabetes susceptibility region insulin-dependent diabetes 3 (Idd3). In this study, we demonstrate a peripheral tolerance defect in the dendritic cells of NOD mice that is independent of regulatory T cells. NOD CD8 T cells specific for islet Ags fail to undergo deletion in the pancreatic lymph nodes. Deletion was promoted by expression of the protective alleles of both Idd3 (Il2) and Idd5 in dendritic cells. We further identify a second tolerance defect that involves endogenous CD4 T cell expression of the disease-promoting NOD alleles of these genetic regions. Pervasive insulitis can be reduced by expression of the Idd3 and Idd5 protective alleles by either the Ag-presenting cell or lymphocytes.

Nonobese Diabetic Congenic Strain Analysis of Autoimmune Diabetes Reveals Genetic Complexity of the Idd18 Locus and Identifies Vav3 as a Candidate Gene

We have used the public sequencing and annotation of the mouse genome to delimit the previously resolved type 1 diabetes (T1D) insulin-dependent diabetes (Idd)18 interval to a region on chromosome 3 that includes the immunologically relevant candidate gene, Vav3. To test the candidacy of Vav3, we developed a novel congenic strain that enabled the resolution of Idd18 to a 604-kb interval, designated Idd18.1, which contains only two annotated genes: the complete sequence of Vav3 and the last exon of the gene encoding NETRIN G1, Ntng1. Targeted sequencing of Idd18.1 in the NOD mouse strain revealed that allelic variation between NOD and C57BL/6J (B6) occurs in noncoding regions with 138 single nucleotide polymorphisms concentrated in the introns between exons 20 and 27 and immediately after the 3′ untranslated region. We observed differential expression of VAV3 RNA transcripts in thymocytes when comparing congenic mouse strains with B6 or NOD alleles at Idd18.1. The T1D protection associated with B6 alleles of Idd18.1/Vav3 requires the presence of B6 protective alleles at Idd3, which are correlated with increased IL-2 production and regulatory T cell function. In the absence of B6 protective alleles at Idd3, we detected a second T1D protective B6 locus, Idd18.3, which is closely linked to, but distinct from, Idd18.1. Therefore, genetic mapping, sequencing, and gene expression evidence indicate that alteration of VAV3 expression is an etiological factor in the development of autoimmune β-cell destruction in NOD mice. This study also demonstrates that a congenic strain mapping approach can isolate closely linked susceptibility genes.

Blockade of the Programmed Death-1 (PD1) Pathway Undermines Potent Genetic Protection from Type 1 Diabetes

Aims/Hypothesis Inhibition of PD1-PDL1 signaling in NOD mice accelerates onset of type 1 diabetes implicating this pathway in suppressing the emergence of pancreatic beta cell reactive T-cells. However, the molecular mechanism by which PD1 signaling protects from type 1 diabetes is not clear. We hypothesized that differential susceptibility of Idd mouse strains to type 1 diabetes when challenged with anti PDL1 will identify genomic loci that collaborate with PD1 signaling in suppressing type 1 diabetes. Methods Anti PDL1 was administered to NOD and various Idd mouse strains at 10 weeks of age and onset of disease was monitored by measuring blood glucose levels. Additionally, histological evaluation of the pancreas was performed to determine degree of insulitis. Statistical analysis of the data was performed using Log-Rank and Students t-test. Results Blockade of PDL1 rapidly precipitated type 1 diabetes in nearly all NOD Idd congenic strains tested, despite the fact that all are moderately (Idd5, Idd3 and Idd10/18) or highly (Idd3/10/18 and Idd9) protected from spontaneous type 1 diabetes by virtue of their protective Idd genes. Only the Idd3/5 strain, which is nearly 100% protected from spontaneous disease, remained normoglycemic following PDL1 blockade. Conclusions These results indicate that multiple Idd loci collaborate with PD1 signaling. Anti PDL1 treatment undermines a large portion of the genetic protection mediated by Idd genes in the NOD model of type 1 diabetes. Basal insulitis correlated with higher susceptibility to type 1 diabetes. These findings have important implications since the PD1 pathway is a target for immunotherapy.

Regulatory T Cell Responses in Participants with Type 1 Diabetes after a Single Dose of Interleukin-2: A Non-Randomised, Open Label, Adaptive Dose-Finding Trial

Background Interleukin-2 (IL-2) has an essential role in the expansion and function of CD4+ regulatory T cells (Tregs). Tregs reduce tissue damage by limiting the immune response following infection and regulate autoreactive CD4+ effector T cells (Teffs) to prevent autoimmune diseases, such as type 1 diabetes (T1D). Genetic susceptibility to T1D causes alterations in the IL-2 pathway, a finding that supports Tregs as a cellular therapeutic target. Aldesleukin (Proleukin; recombinant human IL-2), which is administered at high doses to activate the immune system in cancer immunotherapy, is now being repositioned to treat inflammatory and autoimmune disorders at lower doses by targeting Tregs. Methods and Findings To define the aldesleukin dose response for Tregs and to find doses that increase Tregs physiologically for treatment of T1D, a statistical and systematic approach was taken by analysing the pharmacokinetics and pharmacodynamics of single doses of subcutaneous aldesleukin in the Adaptive Study of IL-2 Dose on Regulatory T Cells in Type 1 Diabetes (DILT1D), a single centre, non-randomised, open label, adaptive dose-finding trial with 40 adult participants with recently diagnosed T1D. The primary endpoint was the maximum percentage increase in Tregs (defined as CD3+CD4+CD25highCD127low) from the baseline frequency in each participant measured over the 7 d following treatment. There was an initial learning phase with five pairs of participants, each pair receiving one of five pre-assigned single doses from 0.04 × 106 to 1.5 × 106 IU/m2, in order to model the dose-response curve. Results from each participant were then incorporated into interim statistical modelling to target the two doses most likely to induce 10% and 20% increases in Treg frequencies. Primary analysis of the evaluable population (n = 39) found that the optimal doses of aldesleukin to induce 10% and 20% increases in Tregs were 0.101 × 106 IU/m2 (standard error [SE] = 0.078, 95% CI = −0.052, 0.254) and 0.497 × 106 IU/m2 (SE = 0.092, 95% CI = 0.316, 0.678), respectively. On analysis of secondary outcomes, using a highly sensitive IL-2 assay, the observed plasma concentrations of the drug at 90 min exceeded the hypothetical Treg-specific therapeutic window determined in vitro (0.015–0.24 IU/ml), even at the lowest doses (0.040 × 106 and 0.045 × 106 IU/m2) administered. A rapid decrease in Treg frequency in the circulation was observed at 90 min and at day 1, which was dose dependent (mean decrease 11.6%, SE = 2.3%, range 10.0%–48.2%, n = 37), rebounding at day 2 and increasing to frequencies above baseline over 7 d. Teffs, natural killer cells, and eosinophils also responded, with their frequencies rapidly and dose-dependently decreased in the blood, then returning to, or exceeding, pretreatment levels. Furthermore, there was a dose-dependent down modulation of one of the two signalling subunits of the IL-2 receptor, the β chain (CD122) (mean decrease = 58.0%, SE = 2.8%, range 9.8%–85.5%, n = 33), on Tregs and a reduction in their sensitivity to aldesleukin at 90 min and day 1 and 2 post-treatment. Due to blood volume requirements as well as ethical and practical considerations, the study was limited to adults and to analysis of peripheral blood only. Conclusions The DILT1D trial results, most notably the early altered trafficking and desensitisation of Tregs induced by a single ultra-low dose of aldesleukin that resolves within 2–3 d, inform the design of the next trial to determine a repeat dosing regimen aimed at establishing a steady-state Treg frequency increase of 20%–50%, with the eventual goal of preventing T1D. Trial Registration ISRCTN Registry ISRCTN27852285; ClinicalTrials.gov NCT01827735

Idd9.1 Locus Controls the Suppressive Activity of FoxP3+CD4+CD25+ Regulatory T-Cells

OBJECTIVE The ∼45-cM insulin-dependent diabetes 9 (Idd9) region on mouse chromosome 4 harbors several different type 1 diabetes–associated loci. Nonobese diabetic (NOD) mice congenic for the Idd9 region of C57BL/10 (B10) mice, carrying antidiabetogenic alleles in three different Idd9 subregions (Idd9.1, Idd9.2, and Idd9.3), are strongly resistant to type 1 diabetes. However, the mechanisms remain unclear. This study aimed to define mechanisms underlying the type 1 diabetes resistance afforded by B10 Idd9.1, Idd9.2, and/or Idd9.3. RESEARCH DESIGN AND METHODS We used a reductionist approach that involves comparing the fate of a type 1 diabetes–relevant autoreactive CD8+ T-cell population, specific for residues 206–214 of islet-specific glucose 6 phosphatase catalytic subunit–related protein (IGRP206–214), in noncongenic versus B10 Idd9–congenic (Idd9.1 + Idd9.2 + Idd9.3, Idd9.2 + Idd9.3, Idd9.1, Idd9.2, and Idd9.3) T-cell receptor (TCR)–transgenic (8.3) NOD mice. RESULTS Most of the protective effect of Idd9 against 8.3-CD8+ T-cell–enhanced type 1 diabetes was mediated by Idd9.1. Although Idd9.2 and Idd9.3 afforded some protection, the effects were small and did not enhance the greater protective effect of Idd9.1. B10 Idd9.1 afforded type 1 diabetes resistance without impairing the developmental biology or intrinsic diabetogenic potential of autoreactive CD8+ T-cells. Studies in T- and B-cell–deficient 8.3-NOD.B10 Idd9.1 mice revealed that this antidiabetogenic effect was mediated by endogenous, nontransgenic T-cells in a B-cell–independent manner. Consistent with this, B10 Idd9.1 increased the suppressive function and antidiabetogenic activity of the FoxP3+CD4+CD25+ T-cell subset in both TCR-transgenic and nontransgenic mice. CONCLUSIONS A gene(s) within Idd9.1 regulates the development and function of FoxP3+CD4+CD25+ regulatory T-cells and, in turn, the activation of CD8+ effector T-cells in the pancreatic draining lymph nodes, without affecting their development or intrinsic diabetogenic potential.