Cellular immunity to a determinant common to glutamate decarboxylase and coxsackie virus in insulin-dependent diabetes

Molecular mimicry: its evolution from concept to mechanism as a cause of autoimmune diseases

On a clonal level, certain antibodies and T cells can interact with dissimilar antigens found in microbes and in host cells. More than 5% of over 800 monoclonal antibodies derived from multiple RNA and DNA viruses, as well as from a large number of T cell clones, engage in such interactions. Several of these cross-reactions, which we termed molecular mimicry, are against unique host proteins involved in autoimmune responses and diseases. Thus, molecular mimicry initiated as a host response to a virus or a microbial infection, but alternatively cross-reacting with an appropriate host-antigen, can be a mechanism for instigating an autoimmune disease. Molecular mimicry provides an explanation for the genetic observation that identical twins rarely manifest the same autoimmune disease and the documented epidemiologic evidence that microbial and/or viral infections often precede autoimmune disorders.

Role of viruses and other microbes in the pathogenesis of type 1 diabetes

Type 1 diabetes is caused by an immune-mediated destruction of insulin producing beta-cells in the pancreas. The risk of the disease is determined by interactions between more than 40 different susceptibility genes and yet unidentified environmental factors. The rapidly increasing incidence indicates that these environmental agents have a significant role in the pathogenesis. Microbes have associated with both increased and decreased risk reflecting their possible role as risk or protective factors. Two main hypotheses have been proposed to explain these effects: the hygiene hypothesis suggests that microbial exposures in early childhood stimulate immunoregulatory mechanisms which control autoimmune reactions (analogy with allergy), while the triggering hypothesis suggests that specific microbes damage insulin producing cells. Certain viruses, particularly enteroviruses, are currently the main candidates for such risk microbes. Enteroviruses cause diabetes in animals and have associated with increased risk of type 1 diabetes in epidemiological studies. They have also been detected in the pancreas of diabetic patients. Possible protective effect of microbes has been studied in animal models and in epidemiological studies, where certain enteral microbes (e.g. hepatitis A virus and Helicobacter pylori) and patterns of gut microbiome have associated with low risk of type 1 diabetes. In conclusion, these microbial effects offer attractive possibilities for the development of preventive interventions for type 1 diabetes based on the elimination of triggering agents (e.g. enterovirus vaccines) or use of protective microbes as probiotics.

Isolation and structural identification of glycopolymers of Bifidobacterium bifidum BIM B-733D as putative players in pathogenesis of autoimmune thyroid diseases

Bifidobacterium bifidum 791 (commercially available as B. bifidum BIM B-733D) cell-surface biopolymers (BPs) interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti TPO and anti Tg, respectively). BPanti-TPO and BPanti-Tg were isolated from the soluble fraction of B. bifidum BIM B-733D by affinity chromatography with anti-TPO or anti-Tg, respectively. Homogeneity of affinity eluates (AEanti-TPO and AEanti-Tg) was tested by size exclusion chromatography. For each AE, the elution profiles generated on the basis of absorbance at 280 nm do not conform to ELISA data for functional activity characteristic of BPs. Moreover, high functional activity was detected in chromatographic fractions that had significantly different molecular weights and no absorbance at 280 nm, which suggests a non-protein (carbohydrate) nature of BPanti-TPO and BPanti-Tg. The semi-preparative size exclusion chromatography of AEanti-TPO and AEanti-Tg with detection by refractometer gave 5,000-7,000 Da fractions containing substances that interact selectively with either anti TPO (BPanti-TPO) or anti-Tg (BPanti-Tg) according to ELISA data. Analysis by two-dimensional NMR spectroscopy including a 1H, 13C-heteronuclear single-quantum coherence experiment indicated that both substances are linear α-1,6-glucans. For the first time, an immunological similarity (molecular mimicry) of glycopolymers of B. bifidum BIM B-733D and human thyroid proteins, TPO and Tg, was shown. On the whole, our data point to a possible role of bifidobacteria in the pathogenesis of autoimmune thyroid diseases (ATD). The main requirements for triggering/acceleration or prevention/abrogation of ATD by bifidobacteria through molecular mimicry mechanism are hypothesised to be (1) genetic predisposition to ATD and (2) intestinal epithelium penetration by α-1,6-glucan.

Infectious triggers in type 1 diabetes: is there a case for epitope mimicry?

Environmental factors are the main contributors to type 1 diabetes (T1D) pathogenesis, yet they remain unidentified. Enteroviruses are proposed candidate triggers due to temporal correlations between infection and T1D autoimmunity and to detection of viral proteins in diseased islets. However, such correlations are not universal and may be relatively uncommon. Furthermore, evidence of a cause-effect relationship is lacking, as infection of non-obese diabetic mice with Coxsackie enteroviruses can either trigger or blunt disease. The proposed mechanisms are either non-antigen-specific (i.e. β-cell destruction and release of sequestered antigens, islet inflammation) or antigen-specific (i.e. epitope mimicry, by which immune responses to enteroviruses may be diverted against homologous β-cell antigens). The case for the latter mechanisms is even less stringent, as there is little evidence of promiscuous antigen recognition at the single T-cell level. Other infectious agents may thus be implicated. Demonstration of their role will require fulfilling the Koch's postulates, namely isolation of the agent preferentially in T1D patients, including before disease onset; and T1D induction when the agent is inoculated into mice. The same is needed for cross-reactive T cells to support epitope mimicry mechanisms. Generation of alternative (humanized) mouse models that could be challenged with candidate microbes is needed.

The targeting of β-cells by T lymphocytes in human type 1 diabetes: clinical perspectives

This review focuses on genes that control β-cell targeting in autoimmune, type 1-dependent, diabetes (T1D) and on insulin as the major autoantigen recognized by T lymphocytes throughout the disease process. T1D associates with multiple gene variants. Beyond genes that predispose to general failure of immune tolerance to self, loci identified by the analysis of crosses between non-obese diabetic (NOD) and conventional mouse strains harbour genes that control β-cell targeting or the deviation of autoimmunity towards other tissues. We report here the role of genes encoding co-activation molecules involved in the activation of T lymphocytes, ICOS and ICOS ligand (B7RP1). NOD mice which are deficient in either of these two molecules are protected from diabetes, but instead develop a neuromuscular autoimmune disease. We also report the characterization in humans of T lymphocytes that are specific for major β-cell autoantigens, especially insulin. This opens the way towards new bioassays in the diagnosis of autoimmunity and towards autoantigen-specific immunotherapy in T1D. In order to develop a new preclinical model of T1D that would allow testing insulin epitopes to induce immune tolerance in vivo, we developed a mouse that is deficient in endogenous major histocompatibility complex class I and class II genes and deficient for the two murine insulin genes and that express human class I, class II and insulin genes.

Type 1 diabetes: translating mechanistic observations into effective clinical outcomes

Type 1 diabetes (T1D) remains an important health problem, particularly in western countries, where the incidence has been increasing in younger children. In 1986, Eisenbarth described T1D as a chronic autoimmune disease. Work over the past three-and-a-half decades has identified many of the genetic, immunological and environmental factors that are involved in the disease and have led to hypotheses concerning its pathogenesis. Clinical trials have been conducted to test these hypotheses but have had mixed results. Here, we discuss the findings that have led to our current concepts of the disease mechanisms involved in T1D and the clinical studies promoted by these studies. The findings from preclinical and clinical studies support the original proposed model for how T1D develops but have also suggested that this disease is more complex than was originally thought and will require broader treatment approaches.

ZnT8-Specific CD4+ T cells display distinct cytokine expression profiles between type 1 diabetes patients and healthy adults

Determination of antigen-specific T cell repertoires in human blood has been a challenge. Here, we show a novel integrated approach that permits determination of multiple parameters of antigen-specific T cell repertoires. The approach consists of two assays: the Direct assay and the Cytokine-driven assay. Briefly, human PBMCs are first stimulated with overlapping peptides encoding a given antigen for 48 hours to measure cytokine secretion (Direct assay). Peptide-reactive T cells are further expanded by IL-2 for 5 days; and after overnight starvation, expanded cells are stimulated with the same peptides from the initial culture to analyze cytokine secretion (Cytokine-driven assay). We first applied this integrated approach to determine the type of islet-antigen-specific T cells in healthy adults. Out of ten donors, the Direct assay identified GAD65-specific CD4⁺ T cells in three adults and zinc transporter 8 (ZnT8)-specific CD4⁺ T cells in five adults. The intracytoplasmic cytokine staining assay showed that these islet-antigen-specific CD4⁺ T cells belonged to the CD45RO⁺ memory compartment. The Cytokine-driven assay further revealed that islet-antigen-specific CD4⁺ T cells in healthy adults were capable of secreting various types of cytokines including type 1 and type 2 cytokines as well as IL-10. We next applied our integrated assay to determine whether the type of ZnT8-specific CD4⁺ T cells is different between Type 1 diabetes patients and age/gender/HLA-matched healthy adults. We found that ZnT8-specific CD4⁺ T cells were skewed towards Th1 cells in T1D patients, while Th2 and IL-10-producing cells were prevalent in healthy adults. In conclusion, the Direct assay and the Cytokine-driven assay complement each other, and the combination of the two assays provides information of antigen-specific T cell repertoires on the breadth, type, and avidity. This strategy is applicable to determine the differences in the quality of antigen-specific T cells between health and disease.

Why is type 1 diabetes increasing?

A series of studies have reported a constant global rise in the incidence of type 1 diabetes. Epidemiological and immunological studies have demonstrated that environmental factors may influence the pathogenesis, leading to a cell-mediated pancreatic β-cell destruction associated with humoral immunity. The search for the triggering factor(s) has been going on for the past century, and yet they are still unknown. This review provides an overview of some of the most well-known theories found in the literature: hygiene, viral, vitamin D deficiency, breast milk and cow's milk hypotheses. Although the hygiene hypothesis appears to be the most promising, positive evidence from animal, human and epidemiological studies precludes us from completely discarding any of the other hypotheses. Moreover, due to contrasting evidence in the literature, a single factor is unlikely to cause an increase in the incidence of diabetes all over the world, which suggests that a multifactorial process might be involved. Although the immunological mechanisms are still unclear, there seems to be some overlap between the various hypotheses. It is thought that the emphasis should be shifted from a single to a multifactorial process and that perhaps the 'balance shift' model should be considered as a possible explanation for the rise in the incidence of type 1 diabetes.

Immunobiology of beta-cell destruction

Type 1 diabetes is a chronic disease characterized by severe insulin deficiency and hyperglycemia, due to autoimmune destruction of pancreatic islets of Langerhans. A susceptible genetic background is necessary, but not sufficient, for the development of the disease. Epidemiological and clinical observations underscore the importance of environmental factors as triggers of type 1 diabetes, currently under investigation. Islet-specific autoantibodies precede clinical onset by months to years and are established tools for risk prediction, yet minor players in the pathogenesis of the disease. Many efforts have been made to elucidate disease-relevant defects in the key immune effectors of islet destruction, from the early failure of specific tolerance to the vicious circle of destructive insulitis. However, the events triggering islet autoimmunity as well as the transition to overt diabetes are still largely unknown, making prevention and treatment strategies still a challenge.

Prevention or acceleration of type 1 diabetes by viruses

Type 1 diabetes is an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells. Even though extensive scientific research has yielded important insights into the immune mechanisms involved in pancreatic β-cell destruction, little is known about the events that trigger the autoimmune process. Recent epidemiological and experimental data suggest that environmental factors are involved in this process. In this review, we discuss the role of viruses as an environmental factor on the development of type 1 diabetes, and the immune mechanisms by which they can trigger or protect against this pathology.

Viral infections and diabetes

Type 1 diabetes mellitus (T1DM) is a multi-factorial autoimmune disease determined by the interaction of genetic, environmental and immunologic factors. One of the environmental risk factors identified by a series of independent studies is represented by viral infection, with strong evidence showing that viruses can indeed infect pancreatic beta cells with consequent effects ranging from functional damage to cell death. In this chapter we review the data obtained both in man and in experimental animal models in support of the potential participation of viral infections to Type 1 diabetes pathogenesis, with a particular emphasis on virus-triggered islet inflammation, beta-cell dysfunction and autoimmunity.

From markers to molecular mechanisms: type 1 diabetes in the post-GWAS era

By the year 2000, a draft of the human genome sequence was completed. Millions of single-nucleotide polymorphisms (SNPs) had been deposited into public databases, and high throughput technologies were under development for SNP genotyping. At that time, it was predicted that large case control association studies would provide far better resolution and power than genome-wide linkage studies. Type 1 diabetes was one of the first phenotypes to be examined by genome-wide association studies (GWAS), and to date over 50 genomic regions have been associated with the disease. In general, the great majority of these loci individually contribute a relatively small degree of risk, and most loci lie outside of coding sequences. The identification of molecular mechanisms from these genomic data therefore remains a significant challenge. Here, we summarize genetic candidate, linkage, and association studies of type 1 diabetes and discuss a potential strategy to identify mechanisms of disease from genomic data.

Role of immune system modulation in prevention of type 1 diabetes mellitus

An increased incidence of Type 1 diabetes mellitus (T1DM) is expected worldwide. Eventually, T1DM is fatal unless treated with insulin. The expansion of interventions to prevent diabetes and the use of alternative treatments to insulin is a dream to be fulfilled. The pathophysiology in T1DM is basically a destruction of beta cells in the pancreas, regardless of which risk factors or causative entities have been present. Individual risk factors can have separate patho-physiological processes to, in turn, cause this beta cell destruction. Currently, autoimmunity is considered the major factor in the pathophysiology of T1DM. In a genetically susceptible individual, viral infection may stimulate the production of antibodies against a viral protein that trigger an autoimmune response against antigenically similar beta cell molecules. Many components of the immune system have been implicated in autoimmunity leading to β-cell destruction, including cytotoxic and helper T-cells, B-cells, macrophages, and dendritic cells. The inflammatory process in early diabetes is thought to be initiated and propagated by the effect of Th1-secreted cytokines (e.g. g interferon) and suppressed by Th2-secreted antiinflammatory cytokines (interleukins). Structure and function of β-cell may be modulated by using Th1/Th2-secreted cytokines. Several experimental and clinical trials of applying GAD65, Hsp60, peptide-MHC, pepetide-277 immunization, anti-CD3 infusion, and interleukins to modulate immune response in T1DM were done. Applying such trials in patients with prediabetes, will most likely be the future key in preventing Type 1 autoimmune diabetes.

Viral infections and molecular mimicry in type 1 diabetes

Type 1 diabetes (T1D) is a disease characterized by inflammation of pancreatic islets associated with autoimmunity against insulin-producing beta cells, leading to their progressive destruction. The condition constitutes a significant and worldwide problem to human health, particularly because of its rapid, but thus far unexplained, increase in incidence. Environmental factors such as viral infections are thought to account for this trend. While there is no lack of reports associating viral infections toT1D, it has proven difficult to establish which immunological processes link viral infections to disease onset or progression. One of the commonly discussed pathways is molecular mimicry, a mechanism that encompasses cross-reactive immunity against epitopes shared between viruses and beta cells. In this review, we will take a closer look at mechanistic evidence for a potential role of viruses in T1D, with a special focus on molecular mimicry.

Infection as a cause of type 1 diabetes?

PURPOSE OF REVIEW

It is the current opinion that pathogens, such as viruses, are contributing to the development of type 1 diabetes (T1D) in susceptible individuals. This opinion is based on epidemiological associations, direct isolation of pathogens from the islets of Langerhans, as well as a large amount of data from various experimental animal models. Human enteroviruses have dominated the literature associated with the etiology of T1D. However, virus infections have also been reported to protect from autoimmune disorders.

RECENT FINDINGS

Here we review the evidence for virus infections to be involved in the pathogenesis of T1D and discuss potential mechanisms of how such infections could accelerate the destruction of insulin-producing β-cells. In addition, we will review evidence from epidemiologic and experimental animal studies showing that virus infections could also have protective properties.

SUMMARY

Virus infections play an important role in the pathogenesis of T1D by inducing or accelerating the autodestructive process, but also by protecting from autoimmunity. Thus, multiple sequential infections might shape the autoreactive immune repertoire and the pathogenesis of T1D in a complex fashion.

Molecular mimicry as a mechanism of autoimmune disease

A variety of mechanisms have been suggested as the means by which infections can initiate and/or exacerbate autoimmune diseases. One mechanism is molecular mimicry, where a foreign antigen shares sequence or structural similarities with self-antigens. Molecular mimicry has typically been characterized on an antibody or T cell level. However, structural relatedness between pathogen and self does not account for T cell activation in a number of autoimmune diseases. A proposed mechanism that could have been misinterpreted for molecular mimicry is the expression of dual T cell receptors (TCR) on a single T cell. These T cells have dual reactivity to both foreign and self-antigens leaving the host vulnerable to foreign insults capable of triggering an autoimmune response. In this review, we briefly discuss what is known about molecular mimicry followed by a discussion of the current understanding of dual TCRs. Finally, we discuss three mechanisms, including molecular mimicry, dual TCRs, and chimeric TCRs, by which dual reactivity of the T cell may play a role in autoimmune diseases.

Animal models used to examine the role of the environment in the development of autoimmune disease: findings from an NIEHS Expert Panel Workshop

Autoimmunity is thought to result from a combination of genetics, environmental triggers, and stochastic events. Environmental factors, such as chemicals, drugs or infectious agents, have been implicated in the expression of autoimmune disease, yet human studies are extremely limited in their ability to test isolated exposures to demonstrate causation or to assess pathogenic mechanisms. In this review we examine the research literature on the ability of chemical, physical and biological agents to induce and/or exacerbate autoimmunity in a variety of animal models. There is no single animal model capable of mimicking the features of human autoimmune disease, particularly as related to environmental exposures. An objective, therefore, was to assess the types of information that can be gleaned from the use of animal models, and how well that information can be used to translate back to human health. Our review notes the importance of genetic background to the types and severity of the autoimmune response following exposure to environmental factors, and emphasizes literature where animal model studies have led to increased confidence about environmental factors that affect expression of autoimmunity. A high level of confidence was reached if there were multiple studies from different laboratories confirming the same findings. Examples include mercury, pristane, and infection with Streptococcus or Coxsackie B virus. A second level of consensus identified those exposures likely to influence autoimmunity but requiring further confirmation. To fit into this category, there needed to be significant supporting data, perhaps by multiple studies from a single laboratory, or repetition of some but not all findings in multiple laboratories. Examples include silica, gold, TCE, TCDD, UV radiation, and Theiler's murine encephalomyelitis virus. With the caveat that researchers must keep in mind the limitations and appropriate applications of the various approaches, animal models are shown to be extremely valuable tools for studying the induction or exacerbation of autoimmunity by environmental conditions and exposures.

What is the key environmental trigger in type 1 diabetes--is it viruses, or wheat gluten, or both?

Prevention and treatment of type 1 diabetes is hampered by the fact that the key environmental trigger(s) of the disease is still unknown. Much of the data on this subject points to two possibilities, viruses and wheat gluten. Viruses appear to be involved as an etiological agent in some cases of type 1 diabetes, particularly in fulminant type 1 diabetes. Further analysis of the data suggests that viruses are not the sole trigger of type 1 diabetes in humans, and that wheat gluten may play a role in initiating the disease. Viruses may be the key environmental trigger in some cases of type 1 diabetes, and wheat gluten in others. Conceivably, some cases of type 1 diabetes might be caused by viruses and wheat gluten acting together as disease triggers.

Immunology in the clinic review series: focus on type 1 diabetes and viruses: the role of viruses in type 1 diabetes: a difficult dilemma

Convincing evidence now indicates that viruses are associated with type 1 diabetes (T1D) development and progression. Human enteroviruses (HEV) have emerged as prime suspects, based on detection frequencies around clinical onset in patients and their ability to rapidly hyperglycaemia trigger in the non-obese diabetic (NOD) mouse. Whether or not HEV can truly cause islet autoimmunity or, rather, act by accelerating ongoing insulitis remains a matter of debate. In view of the disease's globally rising incidence it is hypothesized that improved hygiene standards may reduce the immune system's ability to appropriately respond to viral infections. Arguments in favour of and against viral infections as major aetiological factors in T1D will be discussed in conjunction with potential pathological scenarios. More profound insights into the intricate relationship between viruses and their autoimmunity-prone host may lead ultimately to opportunities for early intervention through immune modulation or vaccination.

Immunology in the clinic review series: focus on type 1 diabetes and viruses: the role of viruses in type 1 diabetes: a difficult dilemma

Convincing evidence now indicates that viruses are associated with type 1 diabetes (T1D) development and progression. Human enteroviruses (HEV) have emerged as prime suspects, based on detection frequencies around clinical onset in patients and their ability to rapidly hyperglycaemia trigger in the non-obese diabetic (NOD) mouse. Whether or not HEV can truly cause islet autoimmunity or, rather, act by accelerating ongoing insulitis remains a matter of debate. In view of the disease's globally rising incidence it is hypothesized that improved hygiene standards may reduce the immune system's ability to appropriately respond to viral infections. Arguments in favour of and against viral infections as major aetiological factors in T1D will be discussed in conjunction with potential pathological scenarios. More profound insights into the intricate relationship between viruses and their autoimmunity-prone host may lead ultimately to opportunities for early intervention through immune modulation or vaccination.

Beyond the hormone: insulin as an autoimmune target in type 1 diabetes

Insulin is not only the hormone produced by pancreatic β-cells but also a key target antigen of the autoimmune islet destruction leading to type 1 diabetes. Despite cultural biases between the fields of endocrinology and immunology, these two facets should not be regarded separately, but rather harmonized in a unifying picture of diabetes pathogenesis. There is increasing evidence suggesting that metabolic factors (β-cell dysfunction, insulin resistance) and immunological components (inflammation and β-cell-directed adaptive immune responses) may synergize toward islet destruction, with insulin standing at the crossroad of these pathways. This concept further calls for a revision of the classical dichotomy between type 1 and type 2 diabetes because metabolic and immune mechanisms may both contribute to different extents to the development of different forms of diabetes. After providing a background on the mechanisms of β-cell autoimmunity, we will explain the role of insulin and its precursors as target antigens expressed not only by β-cells but also in the thymus. Available knowledge on the autoimmune antibody and T-cell responses against insulin will be summarized. A unifying scheme will be proposed to show how different aspects of insulin biology may lead to β-cell destruction and may be therapeutically exploited. We will argue about possible reasons why insulin remains the mainstay of metabolic control in type 1 diabetes but has so far failed to prevent or halt β-cell autoimmunity as an immune modulatory reagent.

T cell recognition of autoantigens in human type 1 diabetes: clinical perspectives

Type 1 diabetes (T1D) is an autoimmune disease driven by the activation of lymphocytes against pancreatic β-cells. Among β-cell autoantigens, preproinsulin has been ascribed a key role in the T1D process. The successive steps that control the activation of autoreactive lymphocytes have been extensively studied in animal models of T1D, but remains ill defined in man. In man, T lymphocytes, especially CD8⁺ T cells, are predominant within insulitis. Developing T-cell assays in diabetes autoimmunity is, thus, a major challenge. It is expected to help defining autoantigens and epitopes that drive the disease process, to pinpoint key functional features of epitope-specific T lymphocytes along the natural history of diabetes and to pave the way towards therapeutic strategies to induce immune tolerance to β-cells. New T-cell technologies will allow defining autoreactive T-cell differentiation programs and characterizing autoimmune responses in comparison with physiologically appropriate immune responses. This may prove instrumental in the discovery of immune correlates of efficacy in clinical trials.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence-Based Laboratory Medicine Committee of the American Association for Clinical Chemistry jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (HbA(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of HbA(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence Based Laboratory Medicine Committee of the AACC jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (Hb A(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of Hb A(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Protection against or triggering of Type 1 diabetes? Different roles for viral infections

The emergence of autoreactivity that ultimately destroys insulin-producing β-cells and causes Type 1 diabetes (T1D) is a result of genetic susceptibility and environmental factors, such as viral infections. The ability to induce strong cellular immune responses and to cause inflammation in the target organ makes viral infections prime candidates for the initiation of islet autoreactivity. Indeed, certain viruses have been linked to the occurrence of T1D based on epidemiological, serological and histological findings; and several rodent studies clearly demonstrate that viral infections can trigger autoimmunity. However, viruses have also been shown to efficiently prevent autoimmunity, which underlines the beneficial aspects of exposure to microbial agents as suggested by the hygiene hypothesis. Here, we will try to untangle some aspects of the complex interplay between viruses and the immune system and we will recapitulate by what rationale certain viruses have been associated with T1D.

Regulatory T-cell adoptive immunotherapy: potential for treatment of autoimmunity

Tregs have shown considerable potential in treating preclinical models of autoimmunity. These studies have highlighted the importance of Treg antigen (Ag) specificity. Translation of these promising results to the clinic will require a robust method of generating large pure populations of Ag-specific Tregs. These include the recently described T-cell receptor gene transfer approach, which has proven to be a rapid and reliable method to generate large populations of Ag-specific Tregs. In this article, we will examine these various approaches and discuss their relative merits. Furthermore, we will discuss the obstacles that need to be surmounted to allow adoptive Treg therapy to progress to the clinic for the benefit of autoimmune patients.

The potential of multimer technologies in type 1 diabetes prediction strategies

Type 1 diabetes is an autoimmune disease which occurs in (human leukocyte antigen) genetically predisposed individuals as a consequence of the organ-specific immune destruction of the insulin-producing β cells in the islets of Langherans within the pancreas. Type 1 diabetes is the result of a breakdown in immune regulation that leads to expansion of autoreactive CD4+ and CD8+ T cells, autoantibody-producing B lymphocytes and activation of the innate immune system. Islet-related autoantibodies revealed themselves to be good predictors of future onset of the disease, although they are not directly pathogenetic; T cells instead play a dominant role in disease initiation and progression. In this review, we first discuss the approaches that several laboratories attempted to measure human islet autoantigen-specific T-cell function in type 1 diabetes. T-cell assays could be used in combination with standardized autoantibody screenings to improve predictive strategies. They could also help to monitor in long-term follow-up the efficacy of tolerogenic immunotherapeutic strategies when established at the onset of the disease, and help to predict the recurrence of disease. Although some recent developments based on enzyme-linked immunosorbent spot and immunoblotting techniques have been able to distinguish with good sensitivity and specificity patients from controls, T-cell results, as revealed by international workshops, were indeed largely inconclusive. Nowadays, novel technologies have been exploited that could contribute to answering the tantalizing question of identifying autoreactive T cells. We particularly focus on and discuss MHC multimer tools and emphasize the advantages they can offer but also their weaknesses when used in combination with other T-cell assays. Copyright © 2011 John Wiley & Sons, Ltd.

Cellular tropism of human enterovirus D species serotypes EV-94, EV-70, and EV-68 in vitro: implications for pathogenesis

Enterovirus 94 (EV-94) is an enterovirus serotype described recently which, together with EV-68 and EV-70, forms human enterovirus D species. This study investigates the seroprevalences of these three serotypes and their abilities to infect, replicate, and damage cell types considered to be essential for enterovirus-induced diseases. The cell types studied included human leukocyte cell lines, primary endothelial cells, and pancreatic islets. High prevalence of neutralizing antibodies against EV-68 and EV-94 was found in the Finnish population. The virus strains studied had wide leukocyte tropism. EV-94 and EV-68 were able to produce infectious progeny in leukocyte cell lines with monocytic, granulocytic, T-cell, or B-cell characteristics. EV-94 and EV-70 were capable of infecting primary human umbilical vein endothelial cells, whereas EV-68 had only marginal progeny production and did not induce cytopathic effects in these cells. Intriguingly, EV-94 was able to damage pancreatic islet β-cells, to infect, replicate, and cause necrosis in human pancreatic islets, and to induce proinflammatory and chemoattractive cytokine expression in endothelial cells. These results suggest that HEV-D viruses may be more prevalent than has been thought previously, and they provide in vitro evidence that EV-94 may be a potent pathogen and should be considered a potentially diabetogenic enterovirus type.

Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies

Type 1 diabetes (T1D) is a chronic autoimmune disease in which destruction or damaging of the beta-cells in the islets of Langerhans results in insulin deficiency and hyperglycemia. We only know for sure that autoimmunity is the predominant effector mechanism of T1D, but may not be its primary cause. T1D precipitates in genetically susceptible individuals, very likely as a result of an environmental trigger. Current genetic data point towards the following genes as susceptibility genes: HLA, insulin, PTPN22, IL2Ra, and CTLA4. Epidemiological and other studies suggest a triggering role for enteroviruses, while other microorganisms might provide protection. Efficacious prevention of T1D will require detection of the earliest events in the process. So far, autoantibodies are most widely used as serum biomarker, but T-cell readouts and metabolome studies might strengthen and bring forward diagnosis. Current preventive clinical trials mostly focus on environmental triggers. Therapeutic trials test the efficacy of antigen-specific and antigen-nonspecific immune interventions, but also include restoration of the affected beta-cell mass by islet transplantation, neogenesis and regeneration, and combinations thereof. In this comprehensive review, we explain the genetic, environmental, and immunological data underlying the prevention and intervention strategies to constrain T1D.

Combined peptides of human enterovirus 71 protect against virus infection in mice

Human enterovirus 71 (EV71) is a cause of hand, foot and mouth disease (HMFD) in children under 6 years old, and could cause serious neurological complications in some patients. Numerous large outbreaks of EV71 caused HMFD have occurred recently in Asia, especially in China. The cross-reactivity of EV71 with human brain tissue was observed and the cross-reactivity inducing regions were identified in previously study, which suggested that there were two regions in structural proteins of virus should be avoided in the vaccine. Six peptides without cross-reactivity were selected and combined into three vaccine candidates and applied in further evaluation in neonatal mice. The Vac6 comprising the peptides of P(70-159), P(140-249), P(324-443) and P(746-876) of the structural proteins could provide effective protection on pups against virus infection, as shown in viral copies detection and histopathology examination. Immunohistochemical staining results indicated that Vac6 had no cross-reactivity with human brain tissues. Our results suggested that Vac6 could have potential clinical value against EV71 epidemics caused mainly by C4 strains in the mainland of China.

Immune cell crosstalk in type 1 diabetes

The development of type 1 diabetes involves a complex interaction between pancreatic beta-cells and cells of both the innate and adaptive immune systems. Analyses of the interactions between natural killer (NK) cells, NKT cells, different dendritic cell populations and T cells have highlighted how these different cell populations can influence the onset of autoimmunity. There is evidence that infection can have either a potentiating or inhibitory role in the development of type 1 diabetes. Interactions between pathogens and cells of the innate immune system, and how this can influence whether T cell activation or tolerance occurs, have been under close scrutiny in recent years. This Review focuses on the nature of this crosstalk between the innate and the adaptive immune responses and how pathogens influence the process.

Immunology of beta-cell destruction

The pancreatic islet beta-cells are the target for an autoimmune process that eventually results in an inability to control blood glucose due to the lack of insulin. The different steps that eventually lead to the complete loss of the beta-cells are reviewed to include the very first step of a triggering event that initiates the development of beta-cell autoimmunity to the last step of appearance of islet-cell autoantibodies, which may mark that insulitis is about to form. The observations that the initial beta-cell destruction by virus or other environmental factors triggers islet autoimmunity not in the islets but in the draining pancreatic lymph nodes are reviewed along with possible basic mechanisms of loss of tolerance to islet autoantigens. Once islet autoimmunity is established the question is how beta-cells are progressively killed by autoreactive lymphocytes which eventually results in chronic insulitis. Many of these series of events have been dissected in spontaneously diabetic mice or rats, but controlled clinical trials have shown that rodent observations are not always translated into mechanisms in humans. Attempts are therefore needed to clarify the step 1 triggering mechanisms and the step to chronic autoimmune insulitis to develop evidence-based treatment approaches to prevent type 1 diabetes.

Transgenically induced GAD tolerance curtails the development of early beta-cell autoreactivities but causes the subsequent development of supernormal autoreactivities to other beta-cell antigens

OBJECTIVE

To study how tolerance to GAD65 affects the development of autoimmunity to other beta-cell autoantigens (beta-CAAs) in GAD65-transgenic (GAD-tg) NOD mice.

RESEARCH DESIGN AND METHODS

We used ELISPOT to characterize the frequency and functional phenotype of T-cell responses to GAD65 and other beta-CAAs at different ages in GAD-tg mice and their NOD mouse littermates.

RESULTS

In young GAD-tg mice, Th1 responses to GAD65's dominant determinants were 13-18% of those in young NOD mice. This coincided with a great reduction in Th1 responses to other beta-CAAs. Evidently, GAD65-reactive T-cells are important for activating and/or expanding early autoreactivities in NOD mice. As GAD-tg mice aged, their T-cell responses to GAD65 remained low, but they developed supernormal splenic and pancreatic lymph node T-cell autoimmunity to other beta-CAAs. Apparently, the elimination/impairment of many GAD65-reactive T-cells allowed other beta-CAA-reactive T-cells to eventually expand to a greater extent, perhaps by reducing competition for antigen-presenting cells, or homeostatic proliferation in the target tissue, which may explain the GAD-tg mouse's usual disease incidence.

CONCLUSIONS

Transgenically induced reduction of GAD65 autoreactivity curtailed the development of early T-cell responses to other beta-CAAs. However, later in life, beta-CAA-reactive T-cells expanded to supernormal levels. These data suggest that early beta-cell autoreactivities are mutually dependent for support to activate and expand, while later in the disease process, autoantigen-specific T-cell pools can expand autonomously. These findings have implications for understanding type 1 diabetes immunopathogenesis and for designing antigen-based immunotherapeutics.

Viruses and autoimmunity

Viruses have been suspected as causes and contributors of human autoimmune diseases (AID), although direct evidence for the association is lacking. However, several animal models provide strong evidence that viruses can induce AIDs as well as act to accelerate and exacerbate lesions in situations where self-tolerance is broken. Many models support the hypothesis by acting as molecular mimics that stimulate self-reactive lymphocytes. Mimicry alone is usually inadequate and with human AID, no compelling evidence supports a role for viruses that are acting as molecular mimics. Alternative mechanisms by which viruses participate in autoimmunity are non-specific, involving a mechanistically poorly understood process termed bystander activation or perhaps viral interference with regulatory cell control systems. This review briefly discusses examples where viruses are involved, taking the viewpoint that molecular mimicry is over emphasized as a critical mechanism during AID pathogenesis.

Autoimmune disease triggered by infection with alphaproteobacteria

Despite having long been postulated, compelling evidence for the theory that microbial triggers drive autoimmunity has only recently been reported. A specific association between Novosphingobium aromaticivorans, an ubiquitous alphaproteobacterium, and primary biliary cirrhosis (PBC) has been uncovered in patients with PBC. Notably, the association between Novosphingobium infection and PBC has been confirmed in a mouse model in which infection leads to the development of liver lesions resembling PBC concomitant with the production of anti-PDC-E2 antibodies that cross-react with conserved PDC-E2 epitopes shared by Novosphingobium. The discovery of infectious triggers of autoimmunity is likely to change our current concepts about the etiology of various autoimmune syndromes and may suggest new and simpler ways to diagnose and treat these debilitating diseases.

Selective autoantibody production against CCL3 is associated with human type 1 diabetes mellitus and serves as a novel biomarker for its diagnosis

We have recently demonstrated that patients suffering from chronic autoimmune diseases develop an autoantibody response against key mediators that participate in the initiation and progression of these diseases. In this paper, we show that patients with type 1 diabetes mellitus (T1DM), but not those suffering from several other inflammatory autoimmune diseases, display a selective autoantibody titer to a single CC chemokine named CCL3. From the diagnostic point we show that this response could be used as a biomarker for diagnosis of T1DM, a disease that is currently diagnosed by autoantibodies to competitive anti-insulin Abs, islet cell Abs, and glutamic acid decarboxylase Abs. We show that our currently suggested biomarker is more reliable than each of the above alone, including diagnosis of T1DM at its preclinical stage, and could therefore be used as a novel way for diagnosis of T1DM. These Abs were found to be neutralizing Abs. It is possible, though hard to prove, that these Abs participate in the natural regulation of the human disease. Hence, it has previously been shown by others that selective neutralization of CCL3 suppresses T1DM in NOD mice. Theses results together with ours suggest CCL3 as a preferential target for therapy of T1DM.

Genetic determinants of Type 1 diabetes: immune response genes

Type 1 diabetes (T1D) is a polygenic autoimmune disease. Susceptibility to T1D is strongly linked to a major genetic locus that is the MHC, and several other minor loci including insulin, cytotoxic T-lymphocyte-associated antigen-4, PTPN22 and others that contribute to diabetes risk in an epistatic way. We have observed that there are three sets of DR3-positive autoimmunity-favoring haplotypes in the north-Indian population, including B50-DR3, B58-DR3 and B8-DR3. The classical Caucasian autoimmunity favoring AH8.1 (HLA-A1-B8-DR3) is rare in the Indian population, and has been replaced by a variant AH8.1v, which differs from the Caucasian AH8.1 at several gene loci. Similarly, there are additional HLA-DR3 haplotypes, A26-B8-DR3 (AH8.2), A24-B8-DR3 (AH8.3), A3-B8-DR3 (AH8.4) and A31-B8-DR3 (AH8.5), of which AH8.2 is the most common. The fact that disease-associated DR3-positive haplotypes show heterogeneity in different populations suggests that these might possess certain shared components that are involved in the development of autoimmunity.

Immunology and genetics of type 1 diabetes

Type 1 diabetes is one of the most well-characterized autoimmune diseases. Type 1 diabetes compromises an individual's insulin production through the autoimmune destruction of pancreatic beta-cells. Although much is understood about the mechanisms of this disease, multiple potential contributing factors are thought to play distinct parts in triggering type 1 diabetes. The immunological diagnosis of type 1 diabetes relies primarily on the detection of autoantibodies against islet antigens in the serum of type 1 diabetes mellitus patients. Genetic analyses of type 1 diabetes have linked human leukocyte antigen, specifically class II alleles, to susceptibility to disease onset. Environmental catalysts include various possible factors, such as viral infections, although the evidence linking infections with type 1 diabetes remains inconclusive. Imbalances within the immune system's system of checks and balances may promote immune activation, while undermining immune regulation. A lack of proper regulation and overactive pathogenic responses provide a framework for the development of autoimmune abnormalities. Type 1 diabetes is a predictable and potentially treatable disease that still requires much research to fully understand and pinpoint the exact triggering events leading to autoimmune activation. In silico research can aid the comprehension of the etiology of complex disease pathways, including Type I diabetes, in order to and help predict the outcome of therapeutic strategies aimed at preserving beta-cell function.

Immunogenicity in peptide-immunotherapy: from self/nonself to similar/dissimilar sequences

The nature of the relationship between an antigenic amino acid sequence and its capability to evoke an immune response is still an unsolved problem. Although experiments indicate that specific (dis)continuous amino acid sequences may determine specific immune responses, how immunogenic properties and recognition informations are mapped onto a non-linear sequence is not understood. Immunology has invoked the concept of self/nonself discrimination in order to explain the capability of the organism to selectively immunoreact. However, no clear, logical and rational pathway has emerged to relate a structure and its immuno-nonreactivity. It cannot yet be dismissed what Koshland wrote in 1990: "Of all the mysteries of modern science, the mechanism of self versus nonself recognition in the immune system ranks at or near the top". This chapter reviews the concept of self/nonself discrimination in the immune system starting from the historical perspective and the conceptual framework that underlie immune reaction pattern. It also introduces future research directions based on a proteomic dissection of the immune unit, qualitatively defined as a low-similarity sequence and quantitatively delimitated by the minimum amino acid requisite able to evoke an immune response, independently ofany, microbial or viral, "foreignness".

TEDDY Study Group. The Environmental Determinants of Diabetes in the Young (TEDDY) Study

The etiology of type 1 diabetes (T1D) remains unknown, but a growing body of evidence points to infectious agents and/or components of early childhood diet. The National Institutes of Health has established the TEDDY Study consortium of six clinical centers in the United States and Europe and a data coordinating center to identify environmental factors predisposing to, or protective against, islet autoimmunity and T1D. From 2004-2009, TEDDY will screen more than 360,000 newborns from both the general population and families already affected by T1D to identify an estimated 17,804 children with high-risk HLA-DR,DQ genotypes. Of those, 7,801 (788 first-degree relatives and 7,013 newborns with no family history of T1D) will be enrolled in prospective follow-up beginning before the age of 4.5 months. As of May 2008, TEDDY has screened more than 250,000 newborns and enrolled nearly 5,000 infants--approximately 70% of the final cohort. Participants are seen every 3 months up to 4 years of age, with subsequent visits every 6 months until the subject is 15 years of age. Blood samples are collected at each visit for detection of candidate infectious agents and nutritional biomarkers; monthly stool samples are collected for infectious agents. These samples are saved in a central repository. Primary endpoints include (1) appearance of one or more islet autoantibodies (to insulin, GAD65 or IA-2) confirmed at two consecutive visits; (2) development of T1D. By age 15, an estimated 800 children will develop islet autoimmunity and 400 will progress to T1D; 67 and 27 children have already reached these endpoints.