Diabetes induced by Coxsackie virus: initiation by bystander damage and not molecular mimicry

Antibodies against H1N1 influenza virus hemagglutinin cross-react with prohibitin

Influenza virus infection is associated with type 1 diabetes (T1DM), but its pathogenesis remains unclear. Here, our study found that one of the monoclonal antibodies against H1N1 influenza virus hemagglutinin(HA) cross-reacted with human pancreatic tissue and further demonstrated that it binded to rat islet β-cells. We immunoprecipitated islet protein with this cross-reactive antibody and identified the bound antigen as prohibitin by mass spectrometry. We then expressed the prohibitin protein in bacteria and confirmed the antibody binding to prohibitin by Western blot. We also verified the cross-reactivity of the antibody by prohibitin-siRNA transfection in islet beta cells. We conclude that prohibitin is an autoantigen that cross-reacts with influenza virus HA. The correlation between the autoantigen prohibitin and type 1 diabetes remains to be investigated.

Infections: a double-edge sword in autoimmunity

PURPOSE OF REVIEW

Infections play a role in the pathogenesis of autoimmune diseases (AID). Several bacterial and viral pathogens play a double role, as both inducers and inhibitors of AID. In this review, we will present current evidence and discuss different aspects of this notion.

RECENT FINDINGS

Infectors that both inhibit and induce AID include Helicobacter pylori, Klebsiella pneumoniae, hepatitis B virus, group B Coxsackieviruses, Epstein-Barr virus and Lymphocytic choriomeningitis virus. Numerous AID are affected by infections, including polyarteritis nodosa, inflammatory bowel disease, and type 1 diabetes. Some pathogens, such as group B Coxsackieviruses, may induce and inhibit the development of the same AID. This reveals a complex role of infections in autoimmunity pathogenesis.

SUMMARY

Elucidating the exact role of each pathogen on each specific AID is important, as this will enable evaluating the manipulation of these infections in the treatment of AID.

β Cell Hypoxia-Inducible Factor-1α Is Required for the Prevention of Type 1 Diabetes

The development of autoimmune disease type 1 diabetes (T1D) is determined by both genetic background and environmental factors. Environmental triggers include RNA viruses, particularly coxsackievirus (CV), but how they induce T1D is not understood. Here, we demonstrate that deletion of the transcription factor hypoxia-inducible factor-1α (HIF-1α) from β cells increases the susceptibility of non-obese diabetic (NOD) mice to environmentally triggered T1D from coxsackieviruses and the β cell toxin streptozotocin. Similarly, knockdown of HIF-1α in human islets leads to a poorer response to coxsackievirus infection. Studies in coxsackievirus-infected islets demonstrate that lack of HIF-1α leads to impaired viral clearance, increased viral load, inflammation, pancreatitis, and loss of β cell mass. These findings show an important role for β cells and, specifically, lack of β cell HIF-1α in the development of T1D. These data suggest new strategies for the prevention of T1D.

Rationale for enteroviral vaccination and antiviral therapies in human type 1 diabetes

In type 1 diabetes, pancreatic beta cells are destroyed by chronic autoimmune responses. The disease develops in genetically susceptible individuals, but a role for environmental factors has been postulated. Viral infections have long been considered as candidates for environmental triggers but, given the lack of evidence for an acute, widespread, cytopathic effect in the pancreas in type 1 diabetes or for a closely related temporal association of diabetes onset with such infections, a role for viruses in type 1 diabetes remains unproven. Moreover, viruses have rarely been isolated from the pancreas of individuals with type 1 diabetes, mainly (but not solely) due to the inaccessibility of the organ. Here, we review past and recent literature to evaluate the proposals that chronic, recurrent and, possibly, persistent enteroviral infections occur in pancreatic beta cells in type 1 diabetes. We also explore whether these infections may be sustained by different virus strains over time and whether multiple viral hits can occur during the natural history of type 1 diabetes. We emphasise that only a minority of beta cells appear to be infected at any given time and that enteroviruses may become replication defective, which could explain why they have been isolated from the pancreas only rarely. We argue that enteroviral infection of beta cells largely depends on the host innate and adaptive immune responses, including innate responses mounted by beta cells. Thus, we propose that viruses could play a role in type 1 diabetes on multiple levels, including in the triggering and chronic stimulation of autoimmunity and in the generation of inflammation and the promotion of beta cell dysfunction and stress, each of which might then contribute to autoimmunity, as part of a vicious circle. We conclude that studies into the effects of vaccinations and/or antiviral drugs (some of which are currently on-going) is the only means by which the role of viruses in type 1 diabetes can be finally proven or disproven.

Suppression of diabetes by accumulation of non-islet-specific CD8+ effector T cells in pancreatic islets

The inflammatory lesion at the pancreatic islet in type 1 diabetes (T1D) contains a heterogeneous infiltrate of T cells. In human and mouse studies, a large majority (98 to 99%) of the cytotoxic CD8⁺ T cells (CTLs) within islets are not specific to any islet antigen and are thought to passively add to tissue damage. We show by intravital confocal microscopy the opposite, immune-regulatory function of this cohort of CTLs. Diabetes did not develop in mice with islets showing high levels of infiltration of non-islet-specific CTLs not recognizing local antigens. Accumulation of such CTLs resulted in lower activation and proliferation of islet-specific CTLs, leading them to enter a state of unresponsiveness due to limited access to antigens at the inflammatory lesion. This nonspecific suppression by nonautoreactive CTLs was recapitulated in a model of viral meningitis, may explain viral interference in autoimmunity, and provides insight into the regulation of organ-specific autoimmune responses.

Developing a vaccine for type 1 diabetes by targeting coxsackievirus B

INTRODUCTION

Virus infections have long been considered as a possible cause of type 1 diabetes (T1D). One virus group, enteroviruses (EVs), has been studied extensively, and clinical development of a vaccine against T1D-associated EV types has started.

AREAS COVERED

Epidemiological studies have indicated an association between EVs and T1D. These viruses have a strong tropism for insulin-producing β-cells; the destruction of these cells leads to T1D. The exact mechanisms by which EVs could cause T1D are not known, but direct infection of β-cells and virus-induced inflammation may play a role. Recent studies have narrowed down the epidemiological association to a subset of EVs: group B coxsackieviruses (CVBs). These findings have prompted efforts to develop vaccines against CVBs. Prototype CVB vaccines have prevented both infection and CVB-induced diabetes in mice. This review summarizes recent progress in the field and the specifics of what could constitute the first human vaccine developed for a chronic autoimmune disease.

EXPERT COMMENTARY

Manufacturing of a clinical CVB vaccine as well as preclinical studies are currently in progress in order to enable clinical testing of the first CVB vaccine. Ongoing scientific research projects can significantly facilitate this effort by providing insights into the mechanisms of the CVB-T1D association.

Redox-Sensitive Innate Immune Pathways During Macrophage Activation in Type 1 Diabetes

SIGNIFICANCE

Type 1 diabetes (T1D) is an autoimmune disease resulting in β-cell destruction mediated by islet-infiltrating leukocytes. The role of oxidative stress in human and murine models of T1D is highly significant as these noxious molecules contribute to diabetic complications and β-cell lysis, but their direct impact on dysregulated autoimmune responses is highly understudied. Pro-inflammatory macrophages play a vital role in the initiation and effector phases of T1D by producing free radicals and pro-inflammatory cytokines to facilitate β-cell destruction and to present antigen to autoreactive T cells. Recent Advances: Redox modulation of macrophage functions may play critical roles in autoimmunity. These include enhancing pro-inflammatory innate immune signaling pathways in response to environmental triggers, enforcing an M1 macrophage differentiation program, controlling antigen processing, and altering peptide recognition by oxidative post-translational modification. Therefore, an oxidative environment may act on multiple macrophage functions to orchestrate T1D pathogenesis.

CRITICAL ISSUES

Mechanisms involved in the initiation of T1D remain unclear, making preventive and early therapeutics difficult to develop. Although many of these advances in the redox regulation of macrophages are in their infancy, they provide insight into how oxidative stress aids in the precipitating event of autoimmune activation.

FUTURE DIRECTIONS

Future studies should be aimed at mechanistically determining which redox-regulated macrophage functions are pertinent in T1D pathogenesis, as well as at investigating potential targetable therapeutics to halt and/or dampen innate immune activation in T1D.

The proinflammatory effects of macrophage-derived NADPH oxidase function in autoimmune diabetes

Type 1 diabetes (T1D) is an autoimmune disease culminating in the destruction of insulin-producing pancreatic β-cells. While ultimately a T cell-mediated disease, macrophages play an indispensable role in disease initiation and progression. Infiltrating macrophages generate an inflammatory environment by releasing NADPH oxidase-derived superoxide and proinflammatory cytokines. The synthesis of reactive oxygen species (ROS) is acknowledged as putative factors contributing to autoimmunity and β-cell damage in T1D. In addition to direct lysis, free radicals collectively participate in β-cell destruction by providing a redox-dependent third signal necessary for islet-reactive CD4 and CD8 T cell maturation and by inducing oxidative post-translational modifications of β-cell epitopes to further exacerbate autoimmune responses. This review will provide an overview of macrophage function and a synergistic cross-talk with redox biology that contributes to autoimmune dysregulation in T1D.

The pertussis hypothesis: Bordetella pertussis colonization in the etiology of asthma and diseases of allergic sensitization

Decades of peer reviewed evidence demonstrate that: 1)Bordetellapertussisand pertussis toxin are potent adjuvants, inducing asthma and allergic sensitization in animal models of human disease, 2)Bordetella pertussisoften colonizes the human nasopharynx, and is well documented in highly pertussis-vaccinated populations and 3) in children, a history of whooping cough increases the risk of asthma and allergic sensitization disease. We build on these observations with six case studies and offer a pertussis-based explanation for the rapid rise in allergic disease in former East Germany following the fall of the Berlin Wall; the current asthma, peanut allergy, and anaphylaxis epidemics in the United States; the correlation between the risk of asthma and gross national income per capita by country; the lower risk of asthma and allergy in children raised on farms; and the reduced risk of atopy with increased family size and later sibling birth order. To organize the evidence for the pertussis hypothesis, we apply the Bradford Hill criteria to the association between Bordetella pertussisand asthma and allergicsensitization disease. We propose that, contrary to conventional wisdom that nasopharyngealBordetella pertussiscolonizing infections are harmless, subclinicalBordetella pertussiscolonization is an important cause of asthma and diseases of allergic sensitization.

Vaccine-associated inflammatory diseases of the central nervous system: from signals to causation

PURPOSE OF REVIEW

As the most cost-effective intervention in preventive medicine and as a crucial element of any public health program, vaccination is used extensively with over 90% coverage in many countries. As approximately 5-8% of the population in developed countries suffer from an autoimmune disorder, people with an autoimmune disease are most likely to be exposed to some vaccines before or after the disease onset. In fact, a number of inflammatory disorders of the central nervous system have been associated with the administration of various vaccines. These adverse events, be they spurious associations or genuine reactions to the vaccine, may lead to difficulties in obtaining public trust in mass vaccination programs. There is, thus, an urgent need to understand whether vaccination triggers or enhances autoimmune responses.

RECENT FINDINGS

By reviewing vaccine-associated inflammatory diseases of the central nervous system, this study describes the current knowledge on whether the safety signal was coincidental, as in the case of multiple sclerosis with several vaccines, or truly reflected a causal link, as in narcolepsy with cataplexy following pandemic H1N1 influenza virus vaccination.

SUMMARY

The lessons learnt emphasize a central role of thorough, ideally prospective, epidemiological studies followed, if the signal is deemed plausible or real, by immunological investigations.

Interactions Between the Neuroendocrine System and T Lymphocytes in Diabetes

It is well established that there is a fine-tuned bidirectional communication between the immune and neuroendocrine tissues in maintaining homeostasis. Several types of immune cells, hormones, and neurotransmitters of different chemical nature are involved as communicators between organs. Apart of being key players of the adaptive arm of the immune system, it has been recently described that T lymphocytes are involved in the modulation of metabolism of several tissues in health and disease. Diabetes may result mainly from lack of insulin production (type 1 diabetes) or insufficient insulin and insulin resistance (type 2 diabetes), both influenced by genetic and environmental components. Herein, we discuss accumulating data regarding the role of the adaptive arm of the immune system in the pathogenesis of diabetes; including the action of several hormones and neurotransmitters influencing on central and peripheral T lymphocytes development and maturation, particularly under the metabolic burden triggered by diabetes. In addition, we comment on the role of T-effector lymphocytes in adipose and liver tissues during diabetes, which together enhances pancreatic β-cell stress aggravating the disease.

Superoxide Production by NADPH Oxidase Intensifies Macrophage Antiviral Responses during Diabetogenic Coxsackievirus Infection

Coxsackievirus B infections are suspected environmental triggers of type 1 diabetes (T1D) and macrophage antiviral responses may provide a link to virus-induced T1D. We previously demonstrated an important role for NADPH oxidase (NOX)-derived superoxide production during T1D pathogenesis, as NOX-deficient NOD mice (NOD.Ncf1m1J ) were protected against T1D due, in part, to impaired proinflammatory TLR signaling in NOD.Ncf1m1J macrophages. Therefore, we hypothesized that loss of NOX-derived superoxide would dampen diabetogenic antiviral macrophage responses and protect from virus-induced diabetes. Upon infection with a suspected diabetogenic virus, Coxsackievirus B3 (CB3), NOD.Ncf1m1J mice remained resistant to virus-induced autoimmune diabetes. A concomitant decrease in circulating inflammatory chemokines, blunted antiviral gene signature within the pancreas, and reduced proinflammatory M1 macrophage responses were observed. Importantly, exogenous superoxide addition to CB3-infected NOD.Ncf1m1J bone marrow-derived macrophages rescued the inflammatory antiviral M1 macrophage response, revealing reduction-oxidation-dependent mechanisms of signal transducer and activator of transcription 1 signaling and dsRNA viral sensors in macrophages. We report that superoxide production following CB3 infection may exacerbate pancreatic β cell destruction in T1D by influencing proinflammatory M1 macrophage responses, and mechanistically linking oxidative stress, inflammation, and diabetogenic virus infections.

On type 1 diabetes mellitus pathogenesis

Type 1 diabetes mellitus (T1DM) results from the autoimmune destruction of β cells of the endocrine pancreas. Pathogenesis of T1DM is different from that of type 2 diabetes mellitus, where both insulin resistance and reduced secretion of insulin by the β cells play a synergistic role. We will present genetic, environmental and immunologic factors that destroy β cells of the endocrine pancreas and lead to insulin deficiency. The process of autoimmune destruction takes place in genetically susceptible individuals under the triggering effect of one or more environmental factors and usually progresses over a period of many months to years, during which period patients are asymptomatic and euglycemic, but positive for relevant autoantibodies. Symptomatic hyperglycemia and frank diabetes occur after a long latency period, which reflects the large percentage of β cells that need to be destroyed before overt diabetes become evident.

Distinct fecal and oral microbiota composition in human type 1 diabetes, an observational study

OBJECTIVE

Environmental factors driving the development of type 1 diabetes (T1D) are still largely unknown. Both animal and human studies have shown an association between altered fecal microbiota composition, impaired production of short-chain fatty acids (SCFA) and T1D onset. However, observational evidence on SCFA and fecal and oral microbiota in adults with longstanding T1D vs healthy controls (HC) is lacking.

RESEARCH DESIGN AND METHODS

We included 53 T1D patients without complications or medication and 50 HC matched for age, sex and BMI. Oral and fecal microbiota, fecal and plasma SCFA levels, markers of intestinal inflammation (fecal IgA and calprotectin) and markers of low-grade systemic inflammation were measured.

RESULTS

Oral microbiota were markedly different in T1D (eg abundance of Streptococci) compared to HC. Fecal analysis showed decreased butyrate producing species in T1D and less butyryl-CoA transferase genes. Also, plasma levels of acetate and propionate were lower in T1D, with similar fecal SCFA. Finally, fecal strains Christensenella and Subdoligranulum correlated with glycemic control, inflammatory parameters and SCFA.

CONCLUSIONS

We conclude that T1D patients harbor a different amount of intestinal SCFA (butyrate) producers and different plasma acetate and propionate levels. Future research should disentangle cause and effect and whether supplementation of SCFA-producing bacteria or SCFA alone can have disease-modifying effects in T1D.

Optimizing Multiplexed Detections of Diabetes Antibodies via Quantitative Microfluidic Droplet Array

Sensitive, single volume detections of multiple diabetes antibodies can provide immunoprofiling and early screening of at-risk patients. To advance the state-of-the-art suspension assays for diabetes antibodies, porous hydrogel droplets are leveraged in microfluidic serpentine arrays to enhance reagent transport. This spatially multiplexed assay is applied to the detection of antibodies against insulin, glutamic acid decarboxylase, and insulinoma-associated protein 2. Optimization of assay protocol results in a shortened assay time of 2 h, with better than 20 pg mL Supporting Information detection limits across all three antibodies. Specificity and cross-reactivity tests show negligible background, nonspecific antibody-antigen, and nonspecific antibody-antibody bindings. Multiplexed detections are able to measure within 15% of target concentrations from low to high ranges. The technique enables quantifications of as little as 8000 molecules in each 500 µm droplet in a single volume, multiplexed assay format, a breakthrough necessary for the adoption of diabetes panels for clinical screening and monitoring in the future.

The Four-Way Stop Sign: Viruses, 12-Lipoxygenase, Islets, and Natural Killer Cells in Type 1 Diabetes Progression

Natural killer (NK) cells represent an important effector arm against viral infection, and mounting evidence suggests that viral infection plays a role in the development of type 1 diabetes (T1D) in at least a portion of patients. NK cells recognize their target cells through a delicate balance of inhibitory and stimulatory receptors on their surface. If unbalanced, NK cells have great potential to wreak havoc in the pancreas due to the beta cell expression of the as-yet-defined NKp46 ligand through interactions with the activating NKp46 receptor found on the surface of most NK cells. Blocking interactions between NKp46 and its ligand protects mice from STZ-induced diabetes, but differential expression non-diabetic and diabetic donor samples have not been tested. Additional studies have shown that peripheral blood NK cells from human T1D patients have altered phenotypes that reduce the lytic and functional ability of the NK cells. Investigations of humanT1D pancreas tissues have indicated that the presence of NK cells may be beneficial despite their infrequent detection. In non-obese diabetic (NOD) mice, we have noted that NK cells express high levels of the proinflammatory mediator 12/15-lipoxygenase (12/15-LO), and decreased levels of stimulatory receptors. Conversely, NK cells of 12/15-LO deficient NOD mice, which are protected from diabetes development, express significantly higher levels of stimulatory receptors. Furthermore, the human NK92 cell line expresses the ALOX12 protein [human 12-lipoxygenase (12-LO), related to mouse 12/15-LO] via Western blotting. Human 12-LO is upregulated in the pancreas of both T1D and T2D human donors with insulin-containing islets, showing a link between 12-LO expression and diabetes progression. Therefore, our hypothesis is that NK cells in those susceptible to developing T1D are unable to function properly during viral infections of pancreatic beta cells due to increased 12-LO expression and activation, which contributes to increased interferon-gamma production and an imbalance in activating and inhibitory NK cell receptors, and may contribute to downstream autoimmune T cell responses. The work presented here outlines evidence from our lab, as well as published literature, supporting our hypothesis, including novel data.

Type 1 diabetes and viral infections: What is the relationship?

Type 1 diabetes (T1D) is the most common chronic metabolic disorder in children. Epigenetic and environmental factors capable of altering the penetrance of major susceptibility genes or capable of increasing the penetrance of low-risk genes are currently thought to play a role in triggering autoimmunity and T1D development. This paper discusses the current knowledge of the role of viruses in T1D. Most studies that have evaluated the potential association between viral infections and T1D have indicated that it is highly likely that some of these infectious agents play a role in T1D development. However, most T1D cases are immune-mediated, and it is supposed that the initial viral infection is capable of creating, in genetically predisposed subjects, a particular condition in which chronic local inflammation occurs through the persistence of the infecting virus in pancreatic tissue and the activation of autoimmunity by means of molecular mimicry, bystander activation, or both. Theoretically, this knowledge could lead to possible prophylaxis and therapy for T1D. Further studies devoted to evaluating which infectious agents are linked to T1D and which immune mechanisms induce or protect against the disease are needed before adequate prophylactic and therapeutic measures can be developed.

A Histological Study of Fulminant Type 1 Diabetes Mellitus Related to Human Cytomegalovirus Reactivation

CONTEXT

Fulminant type 1 diabetes mellitus (T1DM) is thought to be partly caused by virus infection.

OBJECTIVE

This study investigated the mechanism of β cell destruction in fulminant T1DM after drug-induced hypersensitivity syndrome (DIHS).

METHODS

We determined the localization of human cytomegalovirus (HCMV), human herpesvirus 6 (HHV-6), and Epstein-Barr virus (EBV) and the expression of interferon regulatory factor 3 (IRF3) and viral receptors of Z-DNA binding protein 1 (ZBP1) and retinoic acid-inducible gene I (RIG-I), together with inflammatory cells, by immunohistochemistry of the autopsy pancreas of a patient with fulminant T1DM with DIHS and in seven subjects with normal glucose tolerance who underwent pancreatectomy.

RESULTS

HCMV-positive cells were detected in islets and exocrine areas in the patient with fulminant T1DM. Greater numbers of macrophages and CD4+ and CD8+ T lymphocytes had infiltrated into HCMV-positive islets than into HCMV-negative islets, and 52.6% of HCMV-positive cells were also positive for IRF3. α Cells expressed IRF3, ZBP1, or RIG-I. No HCMV-positive cells were detected in the control subjects. HHV-6-positive, but not EBV-positive, cells were present in the patient and the control subjects.

CONCLUSIONS

These findings indicate that the immunoresponse caused by HCMV infection was associated with β cell injury.

Two rheumatoid arthritis-specific autoantigens correlate microbial immunity with autoimmune responses in joints

In rheumatoid arthritis (RA), immunological triggers at mucosal sites, such as the gut microbiota, may promote autoimmunity that affects joints. Here, we used discovery-based proteomics to detect HLA-DR-presented peptides in synovia or peripheral blood mononuclear cells and identified 2 autoantigens, N-acetylglucosamine-6-sulfatase (GNS) and filamin A (FLNA), as targets of T and B cell responses in 52% and 56% of RA patients, respectively. Both GNS and FLNA were highly expressed in synovia. GNS appeared to be citrullinated, and GNS antibody values correlated with anti-citrullinated protein antibody (ACPA) levels. FLNA did not show the same results. The HLA-DR-presented GNS peptide has marked sequence homology with epitopes from sulfatase proteins of the Prevotella sp. and Parabacteroides sp., whereas the HLA-DR-presented FLNA peptide has homology with epitopes from proteins of the Prevotella sp. and Butyricimonas sp., another gut commensal. Patients with T cell reactivity with each self-peptide also had responses to the corresponding microbial peptides, and the levels were directly correlated. Furthermore, HLA-DR molecules encoded by shared-epitope (SE) alleles were predicted to bind these self- and microbial peptides strongly, and these responses were more common in RA patients with SE alleles. Thus, sequence homology between T cell epitopes of 2 self-proteins and a related order of gut microbes may provide a link between mucosal and joint immunity in patients with RA.

Is Tolerance Broken in Autoimmunity?

Autoimmune diseases are classified into about 80 different types based on their specificity related to system, organ and/or tissue. About 5% of the western population is affected by this anomaly, but its worldwide incidence is unknown. Autoimmune diseases are heterogeneous in nature and clinical manifestations range from benign disorders to life-threatening conditions. Autoimmunity strikes at any stage of life, but age and/or gender also play role in onset of some of these anomalies. The autoimmune pathogenesis is initiated by the origination of autoantigens, which leads to the development of autoantibodies followed by auto-immunogenicity and the ultimate onset of autoimmunity. There is a lack of suitable therapies to treat autoimmune diseases, because mechanisms involved in the onset of these anomalies were poorly understood. Present therapies are limited to symptomatic treatment and come with severe side effects. Here, I described the molecular mechanisms and cellular events involved in the initiation of autoimmunity and proposed better strategies to modulate such molecular and cellular anomalies, which will help in preventing and/or controlling autoimmune pathogenesis and ultimately aid in enhancing the quality of life.

Environmental Factors Contribute to β Cell Endoplasmic Reticulum Stress and Neo-Antigen Formation in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease in which immune-mediated targeting and destruction of insulin-producing pancreatic islet β cells leads to chronic hyperglycemia. There are many β cell proteins that are targeted by autoreactive T cells in their native state. However, recent studies have demonstrated that many β cell proteins are recognized as neo-antigens following posttranslational modification (PTM). Although modified neo-antigens are well-established targets of pathology in other autoimmune diseases, the effects of neo-antigens in T1D progression and the mechanisms by which they are generated are not well understood. We have demonstrated that PTM occurs during endoplasmic reticulum (ER) stress, a process to which β cells are uniquely susceptible due to the high rate of insulin production in response to dynamic glucose sensing. In the context of genetic susceptibility to autoimmunity, presentation of these modified neo-antigens may activate autoreactive T cells and cause pathology. However, inherent β cell ER stress and protein PTM do not cause T1D in every genetically susceptible individual, suggesting the contribution of additional factors. Indeed, many environmental factors, such as viral infection, chemicals, or inflammatory cytokines, are associated with T1D onset, but the mechanisms by which these factors lead to disease onset remain unknown. Since these environmental factors also cause ER stress, exposure to these factors may enhance production of neo-antigens, therefore boosting β cell recognition by autoreactive T cells and exacerbating T1D pathogenesis. Therefore, the combined effects of physiological ER stress and the stress that is induced by environmental factors may lead to breaks in peripheral tolerance, contribute to antigen spread, and hasten disease onset. This Hypothesis and Theory article summarizes what is currently known about ER stress and protein PTM in autoimmune diseases including T1D and proposes a role for environmental factors in breaking immune tolerance to β cell antigens through neo-antigen formation.

The Folate Cycle As a Cause of Natural Killer Cell Dysfunction and Viral Etiology in Type 1 Diabetes

The folate pathway is critical to proper cellular function and metabolism. It is responsible for multiple functions, including energy (ATP) production, methylation reactions for DNA and protein synthesis and the production of immunomodulatory molecules, inosine and adenosine. These play an important role in immune signaling and cytotoxicity. Herein, we hypothesize that defects in the folate pathway in genetically susceptible individuals could lead to immune dysfunction, permissive environments for chronic cyclical latent/lytic viral infection, and, ultimately, the development of unchecked autoimmune responses to infected tissue, in this case islet beta cells. In the context of type 1 diabetes (T1D), there has been a recent increase in newly diagnosed cases of T1D in the past 20 years that has exceeded previous epidemiological predictions with yet unidentified factor(s). This speaks to a potential environmental trigger that adversely affects immune responses. Most research into the immune dysfunction of T1D has focused on downstream adaptive responses of T and B cells neglecting the role of the upstream innate players such as natural killer (NK) cells. Constantly, surveilling the blood and tissues for pathogens, NK cells remove threats through direct cytotoxic responses and recruitment of adaptive responses using cytokines, such as IL-1β and IFN-γ. One long-standing hypothesis suggests viral infection as a potential trigger for the autoimmune response in T1D. Recent data suggest multiple viruses as potential causal agents. Intertwined with this is an observed reduced NK cell enumeration, cytotoxicity, and cytokine signaling in T1D patients. Many of the viruses implicated in T1D are chronic latent/lysogenic infections with demonstrated capacity to reduce NK cell response and number through mechanisms that resemble those of pregnancy tolerance. Defects in the folate pathway in T1D patients could result in decreased immune response to viral infection or viral reactivation. Dampened NK responses to infections result in improper signaling, improper antigen presentation, and amplified CD8⁺ lymphocyte proliferation and cytotoxicity, a hallmark of beta cell infiltrates in patients with T1D onset. This would suggest a critical role for NK cells in T1D development linked to viral infection and the importance of the folate pathway in maintaining proper NK response.

CD8αα+MHC Class II+ Cell with the Capacity To Terminate Autoimmune Inflammation Is a Novel Antigen-Presenting NK-like Cell in Rats

Discovery of immune tolerance mechanisms, which inhibit pre-existing autoimmune inflammation, may provide us with new strategies for treating autoimmune diseases. We have identified a CD8αα⁺MHC class II⁺ cell with professional APC capacity during our investigation on spontaneous recovery from autoimmune glomerulonephritis in a rat model. This cell actively invades inflamed target tissue and further terminates an ongoing autoimmune inflammation by selective killing of effector autoreactive T cells. In this study, we show that this cell used a cytotoxic machinery of Ly49s⁺ NK cells in killing of target T cells. Thus, this CD8αα⁺MHC class II⁺ cell was a dually functional Ag-presenting NK-like (AP-NK) cell. Following its coupling with target T cells through Ag presentation, killing stimulatory receptor Ly49s6 and coreceptor CD8αα on this cell used rat nonclassic MHC class I C/E16 on the target T cells as a ligand to initiate killing. Thus, activated effector T cells with elevated expression of rat nonclassic MHC class I C/E16 were highly susceptible to the killing by the CD8αα⁺ AP-NK cell. Granule cytolytic perforin/granzyme C from this cell subsequently mediated cytotoxicity. Thus, inhibition of granzyme C effectively attenuated the killing. As it can recognize and eliminate effector autoreactive T cells in the inflamed target tissue, the CD8αα⁺ AP-NK cell not only represents a new type of immune cell involved in immune tolerance, but it also is a potential candidate for developing a cell-based therapy for pre-existing autoimmune diseases.

Receptor for Advanced Glycation End Products (RAGE) in Type 1 Diabetes Pathogenesis

The receptor for advanced glycation end products (RAGE) is a novel protein increasingly studied in the pathogenesis of type 1 diabetes (T1D). RAGE is expressed by several immune cell types, including T cells, antigen-presenting cells, endothelial cells, and the endocrine cells of the pancreatic islets. RAGE binds various ligands including advanced glycation end products (AGEs), high-mobility group box protein 1 (HMGB1), S100 proteins, β-amyloid, β-sheet fibrils, and lipopolysaccharide. AGEs are a particularly interesting ligand because their exogenous introduction into the body can be accelerated by the consumption of AGE-rich processed foods. This review will detail RAGE isoforms and its ligands and discuss how RAGE binding on the aforementioned cells could be linked to T1D pathogenesis.

Cytokine and chemokine profiles of aqueous humor and serum in horses with uveitis measured using multiplex bead immunoassay analysis

OBJECTIVE

To determine whether horses with clinically diagnosed Equine Recurrent Uveitis (ERU) and those with Leptospirosis infection have a specific cytokine profile in their aqueous humor (AH) and serum that differs from horses with uveitis secondary to other ocular inflammatory processes and from horses with normal eyes.

ANIMALS STUDIED

Twenty-five client-owned horses with uveitis that were presented to the North Carolina State University Ophthalmology Service, and four University-owned horses without history or clinical signs of ocular disease.

PROCEDURE

Samples of AH and serum were obtained from horses with ERU (n=13), acute or non-recurrent uveitis (UV; n=7), uveitis secondary to infectious keratitis (IK; n=5), and normal eyes (N; n=4). Cytokine levels in AH and serum were quantified using a multiplex bead immunoassay. Leptospiral antibody titers in serum and AH and PCR for Leptospiral DNA in AH were performed.

RESULTS

In the AH of horses with ERU, increased levels of IL-1a, IL-4, IL-6, IL-8, IL-12p70, FGF-2, G-CSF, and RANTES were measured compared to UV, IK and N eyes, but the differences were not significant. However, IL-10 was significantly higher in ERU eyes compared to IK and N (P=0.029; 0.013), and IP-10 in ERU eyes was significantly higher than in UV and N (P=0.004). Furthermore, MCP-1 was significantly higher in ERU than N (P=0.04). In the serum, increased levels of IL-1a, IL-4, IL-6, IL-8, IL-12p70, fractalkine, and G-CSF were measured in horses with ERU, but the levels were not significantly higher than those observed in UV, IK, or N horses. However, serum IP-10 levels in horses with ERU were significantly higher than in UV and N horses (P=0.005) and MCP-1 levels were significantly higher in ERU than N (P=0.03). Horses with marked ocular inflammation had significantly higher serum levels of G-CSF, IL-1a, fractalkine, IL-13, IL-4, IL-17a, IL-12p70, IFN-γ, and MCP-1. Elevated IL-10 in AH was significantly associated with disease chronicity, both overall and in ERU eyes (P=0.049), and in horses with positive ocular leptospiral titers or leptospiral PCR, significant elevations of IL-10 (P=0.0018; 0.0032) and IP-10 (P=0.0342; 0.043) were detected in the AH compared to leptospiral negative eyes.

CONCLUSIONS

The anti-inflammatory cytokine IL-10 and the pro-inflammatory cytokine IP-10 appear to play an important role in ERU. Further studies are needed to further clarify and characterize cytokine profiles of specific ocular inflammatory diseases, but multiplex bead immunoassay technology shows promise as a diagnostically valuable tool.

The human microbiome and juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in childhood. The pathogenesis of JIA is thought to be the result of a combination of host genetic and environmental triggers. However, the precise factors that determine one's susceptibility to JIA remain to be unravelled. The microbiome has received increasing attention as a potential contributing factor to the development of a wide array of immune-mediated diseases, including inflammatory bowel disease, type 1 diabetes and rheumatoid arthritis. Also in JIA, there is accumulating evidence that the composition of the microbiome is different from healthy individuals. A growing body of evidence indeed suggests that, among others, the microbiome may influence the development of the immune system, the integrity of the intestinal mucosal barrier, and the differentiation of T cell subsets. In turn, this might lead to dysregulation of the immune system, thereby possibly playing a role in the development of JIA. The potential to manipulate the microbiome, for example by faecal microbial transplantation, might then offer perspectives for future therapeutic interventions. Before we can think of such interventions, we need to first obtain a deeper understanding of the cause and effect relationship between JIA and the microbiome. In this review, we discuss the existing evidence for the involvement of the microbiome in JIA pathogenesis and explore the potential mechanisms through which the microbiome may influence the development of autoimmunity in general and JIA specifically.

Microbiome and Anticancer Immunosurveillance

Anticancer immune responses can be considered a desirable form of autoimmunity that may be profoundly shaped by the microbiome. Here, we discuss evidence for the microbiome's influence on anti-tumor immunosurveillance, including those that are indirect and can act at a distance, and we put forward hypotheses regarding mechanisms of how these effects are implemented. These may involve cross-reactivity between microbial and tumor antigens shaping T cell repertoires and/or microbial products stimulating pattern recognition receptors that influence the type and intensity of immune responses. Understanding how the microbiome impacts natural cancer immunosurveillance as well as treatment-induced immune responses will pave the way for more effective therapies and prophylactics.

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

The association between thyroid volume, L-thyroxine therapy and hepatocyte growth factor levels among patients with euthyroid and hypothyroid goitrous and non-goitrous Hashimoto's thyroiditis versus healthy subjects

OBJECTIVE

Hashimoto's thyroiditis (HT) is the most common etiology of hypothyroidism in regions where iodine deficiency is not a concern. To date, many clinical investigations have been conducted to elucidate its pathogenesis. Several growth factors have been shown to have a role in its development. Hepatocyte growth factor (HGF) is one of the aforementioned molecules. We aimed to demonstrate whether HGF is responsible for HT and goiter development. Also, we aimed to test the hypothesis that levo-thyroxine sodium therapy will suppress HGF levels.

MATERIALS AND METHODS

Sixty-one premenopausal women who were admitted to our outpatient clinic between November 2010 and September 2011 were enrolled. Three groups were determined according to their thyroid function tests (TFTs) as euthyroid Hashimoto's, control and subclinical hypothyroid Hashimoto's groups. Basal TFTs, anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-tg), thyroid ultrasonography (USG) and HGF were studied and recorded. Subclinical hypothyroid HT patients received levo-thyroxine sodium replacement therapy, and were re-assessed for the same laboratory and radiologic features after a median 3.5 month follow-up.

RESULTS

Basal HGF levels were not different between groups. In the subclinical hypothyroidism group, HGF levels (752.75 ± 144.91 pg/ml vs. 719.37 ± 128.05 pg/ml; p = 0.496) and thyroid volumes (12.51 ± 3.67 cc vs. 12.18 ± 4.26 cc; p = 0.7) before and after treatment did not change significantly. No correlations were found between HGF and other parameters. HGF levels were similar between subjects with nodular goiter and normal thyroid structure.

CONCLUSIONS

HGF was not shown to be associated with HT and goiter development. In addition, levo-thyroxine sodium replacement therapy did not alter serum HGF levels significantly.

Viral infections in type 1 diabetes mellitus--why the β cells?

Type 1 diabetes mellitus (T1DM) is caused by progressive autoimmune-mediated loss of pancreatic β-cell mass via apoptosis. The onset of T1DM depends on environmental factors that interact with predisposing genes to induce an autoimmune assault against β cells. Epidemiological, clinical and pathology studies in humans support viral infection--particularly by enteroviruses (for example, coxsackievirus)--as an environmental trigger for the development of T1DM. Many candidate genes for T1DM, such as MDA5, PTPN2 and TYK2, regulate antiviral responses in both β cells and the immune system. Cellular permissiveness to viral infection is modulated by innate antiviral responses that vary among different tissues or cell types. Some data indicate that pancreatic islet α cells trigger a more efficient antiviral response to infection with diabetogenic viruses than do β cells, and so are able to eradicate viral infections without undergoing apoptosis. This difference could account for the varying ability of islet-cell subtypes to clear viral infections and explain why chronically infected pancreatic β cells, but not α cells, are targeted by an autoimmune response and killed during the development of T1DM. These issues and attempts to target viral infection as a preventive therapy for T1DM are discussed in the present Review.

Autoimmunity in picornavirus infections

Enteroviruses are small, non-enveloped, positive-sense single-strand RNA viruses, and are ubiquitously found throughout the world. These viruses usually cause asymptomatic or mild febrile illnesses, but have a propensity to induce severe diseases including type 1 diabetes and pancreatitis, paralysis and neuroinflammatory disease, myocarditis, or hepatitis. This pathogenicity may result from induction of autoimmunity to organ-specific antigens. While enterovirus-triggered autoimmunity can arise from multiple mechanisms including antigenic mimicry and release of sequestered antigens, the recent demonstration of T cells expressing dual T cell receptors arising as a natural consequence of Theiler's virus infection is the first demonstration of this autoimmune mechanism.

β cell ER stress and the implications for immunogenicity in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by hyperglycemia due to progressive immune-mediated destruction of insulin-producing pancreatic islet β cells. Although many elegant studies have identified β cell autoantigens that are targeted by the autoimmune response, the mechanisms by which these autoantigens are generated remain poorly understood. Normal β cell physiology includes a high demand for insulin production and secretion in response to dynamic glucose sensing. This secretory function predisposes β cells to significantly higher levels of endoplasmic reticulum (ER) stress compared to nonsecretory cells. In addition, many environmental triggers associated with T1D onset further augment this inherent ER stress in β cells. ER stress may increase abnormal post-translational modification (PTM) of endogenous β cell proteins. Indeed, in other autoimmune disorders such as celiac disease, systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis, abnormally modified neo-antigens are presented by antigen presenting cells (APCs) in draining lymph nodes. In the context of genetic susceptibility to autoimmunity, presentation of neo-antigens activates auto-reactive T cells and pathology ensues. Therefore, the ER stress induced by normal β cell secretory physiology and environmental triggers may be sufficient to generate neo-antigens for the autoimmune response in T1D. This review summarizes what is currently known about ER stress and protein PTM in target organs of other autoimmune disease models, as well as the data supporting a role for ER stress-induced neo-antigen formation in β cells in T1D.

Mechanisms of Beta Cell Dysfunction Associated With Viral Infection

Type 1 diabetes (T1D) results from genetic predisposition and environmental factors leading to the autoimmune destruction of pancreatic beta cells. Recently, a rapid increase in the incidence of childhood T1D has been observed worldwide; this is too fast to be explained by genetic factors alone, pointing to the spreading of environmental factors linked to the disease. Enteroviruses (EVs) are perhaps the most investigated environmental agents in relationship to the pathogenesis of T1D. While several studies point to the likelihood of such correlation, epidemiological evidence in its support is inconclusive or in some instances even against it. Hence, it is still unknown if and how EVs are involved in the development of T1D. Here we review recent findings concerning the biology of EV in beta cells and the potential implications of this knowledge for the understanding of beta cell dysfunction and autoimmune destruction in T1D.

Functional relevance for type 1 diabetes mellitus-associated genetic variants by using integrative analyses

AIM

Type 1 diabetes mellitus (type 1 DM) is an autoimmune disease. Although genome-wide association studies (GWAS) and meta-analyses have successfully identified numerous type 1 DM-associated susceptibility loci, the underlying mechanisms for these susceptibility loci are currently largely unclear.

METHODS

Based on publicly available datasets, we performed integrative analyses (i.e., integrated gene relationships among implicated loci, differential gene expression analysis, functional prediction and functional annotation clustering analysis) and combined with expression quantitative trait loci (eQTL) results to further explore function mechanisms underlying the associations between genetic variants and type 1 DM.

RESULTS

Among a total of 183 type 1 DM-associated SNPs, eQTL analysis showed that 17 SNPs with cis-regulated eQTL effects on 9 genes. All the 9 eQTL genes enrich in immune-related pathways or Gene Ontology (GO) terms. Functional prediction analysis identified 5 SNPs located in transcription factor (TF) binding sites. Of the 9 eQTL genes, 6 (TAP2, HLA-DOB, HLA-DQB1, HLA-DQA1, HLA-DRB5 and CTSH) were differentially expressed in type 1 DM-associated related cells. Especially, rs3825932 in CTSH has integrative functional evidence supporting the association with type 1 DM.

CONCLUSIONS

These findings indicated that integrative analyses can yield important functional information to link genetic variants and type 1 DM.

Recent progress in understanding coxsackievirus replication, dissemination, and pathogenesis

Coxsackieviruses (CVs) are relatively common viruses associated with a number of serious human diseases, including myocarditis and meningo-encephalitis. These viruses are considered cytolytic yet can persist for extended periods of time within certain host tissues requiring evasion from the host immune response and a greatly reduced rate of replication. A member of Picornaviridae family, CVs have been historically considered non-enveloped viruses - although recent evidence suggest that CV and other picornaviruses hijack host membranes and acquire an envelope. Acquisition of an envelope might provide distinct benefits to CV virions, such as resistance to neutralizing antibodies and efficient nonlytic viral spread. CV exhibits a unique tropism for progenitor cells in the host which may help to explain the susceptibility of the young host to infection and the establishment of chronic disease in adults. CVs have also been shown to exploit autophagy to maximize viral replication and assist in unconventional release from target cells. In this article, we review recent progress in clarifying virus replication and dissemination within the host cell, identifying determinants of tropism, and defining strategies utilized by the virus to evade the host immune response. Also, we will highlight unanswered questions and provide future perspectives regarding the potential mechanisms of CV pathogenesis.

Enterovirus and type 1 diabetes: What is the matter?

A complex interaction of genetic and environmental factors can trigger the immune-mediated mechanism responsible for type 1 diabetes mellitus (T1DM) establishment. Environmental factors may initiate and possibly sustain, accelerate, or retard damage to β-cells. The role of environmental factors in this process has been exhaustive studied and viruses are among the most probable ones, especially enteroviruses. Improvements in enterovirus detection methods and randomized studies with patient follow-up have confirmed the importance of human enterovirus in the pathogenesis of T1DM. The genetic risk of T1DM and particular innate and acquired immune responses to enterovirus infection contribute to a tolerance to T1DM-related autoantigens. However, the frequency, mechanisms, and pathways of virally induced autoimmunity and β-cell destruction in T1DM remain to be determined. It is difficult to investigate the role of enterovirus infection in T1DM because of several concomitant mechanisms by which the virus damages pancreatic β-cells, which, consequently, may lead to T1DM establishment. Advances in molecular and genomic studies may facilitate the identification of pathways at earlier stages of autoimmunity when preventive and therapeutic approaches may be more effective.

Lessons from the mouse: potential contribution of bystander lymphocyte activation by viruses to human type 1 diabetes

Viruses are considered to be potential key modulators of type 1 diabetes mellitus, with several possible mechanisms proposed for their modes of action. Here we discuss the evidence for virus involvement, including pancreatic infection and the induction of T cell-mediated molecular mimicry. A particular focus of this review is the further possibility that virus infection triggers bystander activation of pre-existing autoreactive lymphocytes. In this scenario, the virus triggers dendritic cell maturation and proinflammatory cytokine secretion by engaging pattern recognition receptors. These proinflammatory cytokines provoke bystander autoreactive lymphocyte activation in the presence of cognate autoantigen, which leads to enhanced beta cell destruction. Importantly, this mechanism does not necessarily involve pancreatic virus infection, and its virally non-specific nature suggests that it might represent a means commonly employed by multiple viruses. The ability of viruses specifically associated with type 1 diabetes, including group B coxsackievirus, rotavirus and influenza A virus, to induce these responses is also examined. The elucidation of a mechanism shared amongst several viruses for accelerating progression to type 1 diabetes would facilitate the identification of important targets for disease intervention.

Reduced expression of the MDA5 Gene IFIH1 prevents autoimmune diabetes

Although it is widely accepted that type 1 diabetes (T1D) is the result of the autoimmune destruction of insulin-producing β-cells in the pancreas, little is known about the events leading to islet autoimmunity. Epidemiological and genetic data have associated virus infections and antiviral type I interferon (IFN-I) response genes with T1D. Genetic variants in the T1D risk locus interferon induced with helicase C domain 1 (IFIH1) have been identified by genome-wide association studies to confer resistance to T1D and result in the reduction in expression of the intracellular RNA virus sensor known as melanoma differentiation-associated protein 5 (MDA5). Here, we translate the reduction in IFIH1 gene expression that results in protection from T1D. Our functional studies demonstrate that mice heterozygous at the Ifih1 gene express less than half the level of MDA5 protein, which leads to a unique antiviral IFN-I signature and adaptive response after virus infection that protects from T1D. IFIH1 heterozygous mice have a regulatory rather than effector T-cell response at the site of autoimmunity, supporting IFIH1 expression as an essential regulator of the diabetogenic T-cell response and providing a potential mechanism for patients carrying IFIH1 protective polymorphisms.

Environmental trigger(s) of type 1 diabetes: why so difficult to identify?

Type 1 diabetes (T1D) is one of the most common chronic diseases with childhood onset, and the disease has increased two- to fivefold over the past half century by as yet unknown means. T1D occurs when the body's immune system turns against itself so that, in a very specific and targeted way, it destroys the pancreatic β-cells. T1D results from poorly defined interactions between susceptibility genes and environmental determinants. In contrast to the rapid progress in finding T1D genes, identification and confirmation of environmental determinants remain a formidable challenge. This review article will focus on factors which have to be evaluated and decision to take before starting a new prospective cohort study. Considering all the large ongoing prospective studies, new and more conclusive data than that obtained so far should instead come from international collaboration on the ongoing cohort studies.

Autoimmune host-microbiota interactions at barrier sites and beyond

The microbiota is considered to be an important factor influencing the pathogenesis of autoimmunity at both barrier sites and internal organs. Impinging on innate and adaptive immunity, commensals exert protective or detrimental effects on various autoimmune animal models. Human microbiome studies of autoimmunity remain largely descriptive, but suggest a role for dysbiosis in autoimmune disease. Humanized gnotobiotic approaches have advanced our understanding of immune-commensal interactions, but little is known about the mechanisms in autoimmunity. We propose that, similarly to infectious agents, the microbiota mediates autoimmunity via bystander activation, epitope spread, and, particularly under homeostatic conditions, via crossreactivity. This review presents an overview of the current literature concluding with outstanding questions in this field.

Cumulative effect of IFIH1 variants and increased gene expression associated with type 1 diabetes

AIMS

IFIH1 (Interferon Induced with Helicase C domain 1) gene encodes a sensor of double-stranded RNA, which initiates antiviral activity. Recent studies have indicated the association of rare and common IFIH1 variants with type 1 diabetes mellitus (T1D). The aim of this study was to investigate whether polymorphisms in the IFIH1 locus are a risk factor for T1D in Caucasian patients from Poland.

METHODS

We genotyped 514 T1D patients and 713 healthy control individuals for rs3747517, rs1990760, rs2111485 and rs13422767 variants. Cumulative genetic risk score (CGRS) was calculated using unweighted and weighted approaches. We also examined the expression of IFIH1 gene in a cohort of 90 T1D patients.

RESULTS

All studied polymorphisms showed significant association with type 1 diabetes. The risk alleles G of rs3747517, rs2111485, rs13422767 and A of rs1990760 were observed more frequently in T1D group with P values and allelic odds ratio OR (95%CI) < 0.0001, 1.742 (1.428-2.126); 0.001, 1.336 (1.125-1.588); < 0.0001, 1.799 (1.416-2.285); 0.0005, 1.359 (1.144-1.616), respectively. The risk for type 1 diabetes increased with the growing number of the risk alleles. OR (95%CI) for carriers of ≥ 6 risk alleles reached 2.387 (1.552-3.670) for unweighted CGRS and 3.132 (1.928-5.089) for weighted CGRS. Furthermore, IFIH1 gene expression levels in unstimulated peripheral blood mononuclear cells of T1D patients were significantly higher compared to healthy individuals (mean ± SEM mRNA copy number 163.8 ± 15.7 vs. 117.8 ± 7.2; P = 0.046).

CONCLUSIONS

This study confirms the association of the IFIH1 locus with susceptibility to T1D in the Polish population. The cumulative effect of rs3747517, rs1990760, rs2111485 and rs13422767 variants on type 1 diabetes risk was observed.

Toll-like receptor 3 is critical for coxsackievirus B4-induced type 1 diabetes in female NOD mice

Group B coxsackieviruses (CVBs) are involved in triggering some cases of type 1 diabetes mellitus (T1DM). However, the molecular mechanism(s) responsible for this remain elusive. Toll-like receptor 3 (TLR3), a receptor that recognizes viral double-stranded RNA, is hypothesized to play a role in virus-induced T1DM, although this hypothesis is yet to be substantiated. The objective of this study was to directly investigate the role of TLR3 in CVB-triggered T1DM in nonobese diabetic (NOD) mice, a mouse model of human T1DM that is widely used to study both spontaneous autoimmune and viral-induced T1DM. As such, we infected female wild-type (TLR3(+/+)) and TLR3 knockout (TLR3(-/-)) NOD mice with CVB4 and compared the incidence of diabetes in CVB4-infected mice with that of uninfected counterparts. We also evaluated the islets of uninfected and CVB4-infected wild-type and TLR3 knockout NOD mice by immunohistochemistry and insulitis scoring. TLR3 knockout mice were markedly protected from CVB4-induced diabetes compared with CVB4-infected wild-type mice. CVB4-induced T-lymphocyte-mediated insulitis was also significantly less severe in TLR3 knockout mice compared with wild-type mice. No differences in insulitis were observed between uninfected animals, either wild-type or TLR3 knockout mice. These data demonstrate for the first time that TLR3 is 1) critical for CVB4-induced T1DM, and 2) modulates CVB4-induced insulitis in genetically prone NOD mice.

A preclinical study on the efficacy and safety of a new vaccine against Coxsackievirus B1 reveals no risk for accelerated diabetes development in mouse models

AIMS/HYPOTHESIS

Enterovirus infections have been implicated in the aetiology of autoimmune type 1 diabetes. A vaccine could be used to test the causal relationship between enterovirus infections and diabetes development. However, the development of a vaccine against a virus suspected to induce an autoimmune disease is challenging, since the vaccine itself might trigger autoimmunity. Another challenge is to select the enterovirus serotypes to target with a vaccine. Here we aimed to evaluate the function and autoimmune safety of a novel non-adjuvanted prototype vaccine to Coxsackievirus serotype B1 (CVB1), a member of the enterovirus genus.

METHODS

A formalin-inactivated CVB1 vaccine was developed and tested for its immunogenicity and safety in BALB/c and NOD mice. Prediabetic NOD mice were vaccinated, infected with CVB1 or mock-treated to compare the effect on diabetes development.

RESULTS

Vaccinated mice produced high titres of CVB1-neutralising antibodies without signs of vaccine-related side effects. Vaccinated mice challenged with CVB1 had significantly reduced levels of replicating virus in their blood and the pancreas. Prediabetic NOD mice demonstrated an accelerated onset of diabetes upon CVB1 infection whereas no accelerated disease manifestation or increased production of insulin autoantibodies was observed in vaccinated mice.

CONCLUSIONS/INTERPRETATION

We conclude that the prototype vaccine is safe and confers protection from infection without accelerating diabetes development in mice. These results encourage the development of a multivalent enterovirus vaccine for human use, which could be used to determine whether enterovirus infections trigger beta cell autoimmunity and type 1 diabetes in humans.

Type I diabetes mellitus: genetic factors and presumptive enteroviral etiology or protection

We review type 1 diabetes and host genetic components, as well as epigenetics and viruses associated with type 1 diabetes, with added emphasis on the enteroviruses, which are often associated with triggering the disease. Genus Enterovirus is classified into twelve species of which seven (Enterovirus A, Enterovirus B, Enterovirus C, and Enterovirus D and Rhinovirus A, Rhinovirus B, and Rhinovirus C) are human pathogens. These viruses are transmitted mainly by the fecal-oral route; they may also spread via the nasopharyngeal route. Enterovirus infections are highly prevalent, but these infections are usually subclinical or cause a mild flu-like illness. However, infections caused by enteroviruses can sometimes be serious, with manifestations of meningoencephalitis, paralysis, myocarditis, and in neonates a fulminant sepsis-like syndrome. These viruses are often implicated in chronic (inflammatory) diseases as chronic myocarditis, chronic pancreatitis, and type 1 diabetes. In this review we discuss the currently suggested mechanisms involved in the viral induction of type 1 diabetes. We recapitulate current basic knowledge and definitions.