Identification of conserved T cell epitopes and flanking amino acid mutants of endogenous retrovirus Gag antigen in nonobese diabetic mice.

The interactions between endogenous retroviruses (ERVs) and major histocompatibility complex molecules may significantly influence autoimmune diseases due to their common roles in the evolution and development of the adaptive immune system. Notably, regions within the Gag antigens of a specific group of ERVs, similar to murine leukemia retroviruses, exhibit patterns of sequence conservation, variation, and mutation. One highly conserved peptide of Gag, p5-13 (VTTPLSLTL), binds with high affinity to a nonclassic major histocompatibility complex molecule, Qa-1, and is preferentially recognized by T cells enriched in the pancreas of nonobese diabetic (NOD) mice, which spontaneously develop autoimmune type 1 diabetes.

A Targeted Deep Sequencing Method to Quantify Endogenous Retrovirus Gag Sequence Variants and Open Reading Frames Expressed in Nonobese Diabetic Mice.

Endogenous retroviruses (ERVs) are involved in autoimmune diseases such as type 1 diabetes (T1D). ERV gene products homologous to murine leukemia retroviruses are expressed in the pancreatic islets of NOD mice, a model of T1D. One ERV gene, Gag, with partial or complete open reading frames (ORFs), is detected in the islets, and it contains many sequence variants.

Endogenous retrovirus Gag antigen and its gene variants are unique autoantigens expressed in the pancreatic islets of non-obese diabetic mice.

Endogenous retrovirus (ERV) are remnants of ancient retroviruses that have been incorporated into the genome and evidence suggests that they may play a role in the etiology of T1D. We previously identified a murine leukemia retrovirus-like ERV whose Env and Gag antigens are involved in autoimmune responses in non-obese diabetic (NOD) mice. In this study, we show that the Gag antigen is present in the islet stromal cells.

Autoimmune Responses to Exosomes and Candidate Antigens Contribute to Type 1 Diabetes in Non-Obese Diabetic Mice.

Purpose Of Review: The initial autoimmune trigger of type 1 diabetes (T1D) remains unclear. In non-obese diabetic (NOD) mice, islet inflammation starts early in life, suggesting the presence of an endogenous trigger for the spontaneous autoimmune response in this T1D mouse model. In this review, we argue that abnormal release of exosomes might be the trigger of the early inflammatory and autoimmune responses in the islets.

Effects of partially dismantling the CD4 binding site glycan fence of HIV-1 Envelope glycoprotein trimers on neutralizing antibody induction.

Previously, VLPs bearing JR-FL strain HIV-1 Envelope trimers elicited potent neutralizing antibodies (nAbs) in 2/8 rabbits (PLoS Pathog 11(5): e1004932) by taking advantage of a naturally absent glycan at position 197 that borders the CD4 binding site (CD4bs). In new immunizations, we attempted to improve nAb responses by removing the N362 glycan that also lines the CD4bs. All 4 rabbits developed nAbs.

Type 1 diabetes pathogenesis is modulated by spontaneous autoimmune responses to endogenous retrovirus antigens in NOD mice.

Secreted microvesicles (MVs) are potent inflammatory triggers that stimulate autoreactive B and T cells, causing Type 1 Diabetes in non-obese diabetic (NOD) mice. Proteomic analysis of purified MVs released from islet cells detected the presence of endogenous retrovirus (ERV) antigens, including Env and Gag sequences similar to the well-characterized murine leukemia retroviruses. This raises the possibility that ERV antigens may be expressed in the pancreatic islets via MV secretion.

CRISPR-Cas9-Mediated Modification of the NOD Mouse Genome With Ptpn22R619W Mutation Increases Autoimmune Diabetes.

An allelic variant of protein tyrosine phosphatase nonreceptor type 22 (PTPN22), PTPN22(R620W), is strongly associated with type 1 diabetes (T1D) in humans and increases the risk of T1D by two- to fourfold. The NOD mouse is a spontaneous T1D model that shares with humans many genetic pathways contributing to T1D. We hypothesized that the introduction of the murine orthologous Ptpn22(R619W) mutation to the NOD genome would enhance the spontaneous development of T1D.

Exosomes released by islet-derived mesenchymal stem cells trigger autoimmune responses in NOD mice.

Exosomes (EXOs) are secreted, nano-sized membrane vesicles that contain potent immunostimulatory materials. We have recently demonstrated that insulinoma-released EXOs can stimulate the autoimmune responses in nonobese diabetic (NOD) mice, a spontaneous disease model for type 1 diabetes. To investigate whether primary islet cells can produce EXOs, we isolated cells from the islet of Langerhans of NOD mice and cultured them in vitro.

Insulinoma-released exosomes activate autoreactive marginal zone-like B cells that expand endogenously in prediabetic NOD mice.

Exosomes (EXOs) are nano-sized secreted microvesicles that can function as potent endogenous carriers of adjuvant and antigens. To examine a possible role in autoimmunity for EXOs, we studied EXO-induced immune responses in nonobese diabetic (NOD) mice, an autoimmune-prone strain with tissue-specific targeting at insulin-secreting beta cells. EXOs released by insulinoma cells can activate various antigen-presenting cells to secrete several proinflammatory cytokines and chemokines.

Genetic interactions among Idd3, Idd5.1, Idd5.2, and Idd5.3 protective loci in the nonobese diabetic mouse model of type 1 diabetes.

In the NOD mouse model of type 1 diabetes, insulin-dependent diabetes (Idd) loci control the development of insulitis and diabetes. Independently, protective alleles of Idd3/Il2 or Idd5 are able to partially protect congenic NOD mice from insulitis and diabetes, and to partially tolerize islet-specific CD8(+) T cells. However, when the two regions are combined, mice are almost completely protected, strongly suggesting the existence of genetic interactions between the two loci.

Insulinoma-released exosomes or microparticles are immunostimulatory and can activate autoreactive T cells spontaneously developed in nonobese diabetic mice.

Exosomes (EXO) are secreted intracellular microparticles that can trigger inflammation and induce Ag-specific immune responses. To test possible roles of EXO in autoimmunity, we isolated small microparticles, mainly EXO, from mouse insulinoma and examined their activities to stimulate the autoimmune responses in NOD mice, a model for human type 1 diabetes. We demonstrate that the EXO contains strong innate stimuli and expresses candidate diabetes autoantigens.

Antigen processing patterns determine GAD65-specific regulation vs. pathogenesis.

Alterations in presenting self determinants to T cells may depend upon the availability of sites on the molecule adjacent to known determinants to different processing enzymes, or, at the level of amino acid sequence or conformation of a single determinant. We have studied three possible ways that could modulate the processing and presentation of T cell determinants of a diabetes autoantigen, glutamic acid decarboxylase (GAD) 65, which could contribute to induction of GAD65-specific regulatory versus pathogenic T cells in type 1 diabetes (T1D): 1) enhanced presentation of subdominant/cryptic determinants to T cells that have not been well-tolerized, which may activate T cells of high affinity and high aggressiveness; 2) trimming or truncating flanking residues which may otherwise provide needed binding energy to determinants that activate regulatory cells, thus releasing autoaggressive T cells from suppression; 3) biochemical or chemical modifications of self antigens in an inflammatory environment or within activated antigen presenting cells (APC) which may convert a previously regulatory antigen or determinant into a disease-causing one that activates autoreactive T cells at a higher affinity.

Slc11a1 enhances the autoimmune diabetogenic T-cell response by altering processing and presentation of pancreatic islet antigens.

Objective: Efforts to map non-major histocompatibility complex (MHC) genes causing type 1 diabetes in NOD mice identified Slc11a1, formerly Nramp1, as the leading candidate gene in the Idd5.2 region. Slc11a1 is a membrane transporter of bivalent cations that is expressed in late endosomes and lysosomes of macrophages and dendritic cells (DCs).

N-terminal flanking residues of a diabetes-associated GAD65 determinant are necessary for activation of antigen-specific T cells in diabetes-resistant mice.

A diabetes-associated peptide in the glutamic acid decarboxylase 65 (GAD65) molecule, p524-543, activates two distinct populations of T cells, which apparently play opposite roles in the development of diabetes in NOD mice. By comparing the fine specificity of these two T cell repertoires using a nested set of truncated peptides that cover the p524-543 region, we found, surprisingly, that all clones recognized the same core within this peptide, p530-539. The core itself was non-immunogenic, but the residues flanking this shared sequence played the crucial role in selecting T cells to activate.

Antigen processing by autoreactive B cells promotes determinant spreading.

Acute primary immune responses tend to focus on few immunodominant determinants using a very limited number of T cell clones for expansion, whereas chronic inflammatory responses generally recruit a large number of different T cell clones to attack a broader range of determinants of the invading pathogens or the inflamed tissues. In T cell-mediated organ-specific autoimmune disease, a transition from the acute to the chronic phase contributes to pathogenesis, and the broadening process is called determinant spreading. The cellular components catalyzing the spreading reaction are not identified.

A peptide of glutamic acid decarboxylase 65 can recruit and expand a diabetogenic T cell clone, BDC2.5, in the pancreas.

Self peptide-MHC ligands create and maintain the mature T cell repertoire by positive selection in the thymus and by homeostatic proliferation in the periphery. A low affinity/avidity interaction among T cells, self peptides, and MHC molecules has been suggested for these events, but it remains unknown whether or how this self-interaction is involved in tolerance and/or autoimmunity. Several lines of evidence implicate the glutamic acid decarboxylase 65 (GAD-65) peptide, p524-543, as a specific, possibly low affinity, stimulus for the spontaneously arising, diabetogenic T cell clone BDC2.

Thyroxine-binding antibodies inhibit T cell recognition of a pathogenic thyroglobulin epitope.

Thyroid hormone-binding (THB) Abs are frequently detected in autoimmune thyroid disorders but it is unknown whether they can exert immunoregulatory effects. We report that a THB mAb recognizing the 5' iodine atom of the outer phenolic ring of thyroxine (T4) can block T cell recognition of the pathogenic thyroglobulin (Tg) peptide (2549-2560) that contains T4 at aa position 2553 (T4(2553)). Following peptide binding to the MHC groove, the THB mAb inhibited activation of the A(k)-restricted, T4(2553)-specific, mouse T cell hybridoma clone 3.

Enhanced iodination of thyroglobulin facilitates processing and presentation of a cryptic pathogenic peptide.

Increased iodine intake has been associated with the development of experimental autoimmune thyroiditis (EAT), but the biological basis for this association remains poorly understood. One hypothesis has been that enhanced incorporation of iodine in thyroglobulin (Tg) promotes the generation of pathogenic T cell determinants. In this study we sought to test this by using the pathogenic nondominant A(s)-binding Tg peptides p2495 and p2694 as model Ags.