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

LncRNA ARGI Contributes to Virus-Induced Pancreatic β Cell Inflammation Through Transcriptional Activation of IFN-Stimulated Genes

Type 1 diabetes (T1D) is a complex autoimmune disease that develops in genetically susceptible individuals. Most T1D-associated single nucleotide polymorphisms (SNPs) are located in non-coding regions of the human genome. Interestingly, SNPs in long non-coding RNAs (lncRNAs) may result in the disruption of their secondary structure, affecting their function, and in turn, the expression of potentially pathogenic pathways. In the present work, the function of a virus-induced T1D-associated lncRNA named ARGI (Antiviral Response Gene Inducer) is characterized. Upon a viral insult, ARGI is upregulated in the nuclei of pancreatic β cells and binds to CTCF to interact with the promoter and enhancer regions of IFNβ and interferon-stimulated genes, promoting their transcriptional activation in an allele-specific manner. The presence of the T1D risk allele in ARGI induces a change in its secondary structure. Interestingly, the T1D risk genotype induces hyperactivation of type I IFN response in pancreatic β cells, an expression signature that is present in the pancreas of T1D patients. These data shed light on the molecular mechanisms by which T1D-related SNPs in lncRNAs influence pathogenesis at the pancreatic β cell level and opens the door for the development of therapeutic strategies based on lncRNA modulation to delay or avoid pancreatic β cell inflammation in T1D.

Stress and Diabetes Mellitus: Pathogenetic Mechanisms and Clinical Outcome

Evidence suggests that psychological and physical stress are relevant triggering factors for the onset of type 1 diabetes (T1D) and type 2 diabetes (T2D). The underlying mechanisms involve a complex neuroendocrine structure, involving the central nervous system and the periphery. Psychological stress leads to an increase of serum glucocorticoid concentrations and catecholamines release increasing the insulin need and the insulin resistance. According to the β-cell stress hypothesis, also causes of increased insulin demand, such as rapid growth, overweight, puberty, low physical activity, trauma, infections, and glucose overload, are potentially relevant factors in development of T1D. It has also been demonstrated that chronic stress and obesity form a vicious circle which leads to a definitive metabolic failure, increasing the risk of developing T2D. In this review, we will provide the most recent data concerning the role of stress in the outcomes of T1D and T2D, with a focus on the role of physical and psychological stress on the onset of T1D.

Infections in the first year of life and development of beta cell autoimmunity and clinical type 1 diabetes in high-risk individuals: the TRIGR cohort

AIMS/HYPOTHESIS

Accumulated data suggest that infections in early life contribute to the development of type 1 diabetes. Using data from the Trial to Reduce IDDM in the Genetically at Risk (TRIGR), we set out to assess whether children who later developed diabetes-related autoantibodies and/or clinical type 1 diabetes had different exposure to infections early in life compared with those who did not.

METHODS

A cohort of 2159 children with an affected first-degree relative and HLA-conferred susceptibility to type 1 diabetes were recruited between 2002 and 2007 and followed until 2017. Infections were registered prospectively. The relationship between infections in the first year of life and the development of autoantibodies or clinical type 1 diabetes was analysed using univariable and multivariable Cox regression models. As this study was exploratory, no adjustment was made for multiple comparisons.

RESULTS

Adjusting for HLA, sex, breastfeeding duration and birth order, those who had seven or more infections during their first year of life were more likely to develop at least one positive type 1 diabetes-related autoantibody (p=0.028, HR 9.166 [95% CI 1.277, 65.81]) compared with those who had no infections. Those who had their first viral infection aged between 6 and 12 months were less likely to develop at least one positive type 1 diabetes-related antibody (p=0.043, HR 0.828 [95% CI 0.690, 0.994]) or multiple antibodies (p=0.0351, HR 0.664 [95% CI 0.453, 0.972]). Those who had ever had an unspecified bacterial infection were more likely to develop at least one positive type 1 diabetes-related autoantibody (p=0.013, HR 1.412 [95% CI 1.075, 1.854]), to develop multiple antibodies (p=0.037, HR 1.652 [95% CI 1.030, 2.649]) and to develop clinical type 1 diabetes (p=0.011, HR 2.066 [95% CI 1.182, 3.613]).

CONCLUSIONS/INTERPRETATION

We found weak support for the assumption that viral infections early in life may initiate the autoimmune process or later development of type 1 diabetes. In contrast, certain bacterial infections appeared to increase the risk of both multiple autoantibodies and clinical type 1 diabetes.

Urinary tract infection in patients with diabetes mellitus and the role of parental genetics in the emergence of the disease

This study aimed to assess the role of paternal genetics in the development of diabetic mellitus (DM) and determine the impact of DM on the urinary system by investigating the percentage of patients with urinary tract infection (UTI). The study included 100 people with DM; their ages ranged from 5 to 83 years. The DM and blood sugar levels were diagnosed clinically and at a laboratory in Al-Zahra Teaching Hospital and the outpatient clinics. The age, gender, and causes of DM and the family history of diabetes were reported. Isolation and identification of bacterial species were made depending on culture media and biochemical tests. The average age of patients was 47.7±5.5, and most of them were female (67%). The incidence of DM increased with age, and the main cause of DM was likely to be a genetic predisposition (family history), where 32% of patients appeared to have a positive family history and the presence of DM in both parents or only the mother had a significant role in increasing the genetic predisposition of developing DM. Among the non-genetic causes of DM, the most common was exposure to sudden psychological or nervous shock (41%). Obesity also had an important role in the development of diabetes, and also pregnancy and smoking. Moreover, 66% of patients with type 2 DM and all with type 1 DM suffered from UTIs. The main causative agents were E. coli (60%) and Proteus spp. (13%). The majority of patients suffering from UTIs (73%) were females. In conclusion, type 2 DM is the most common, especially in females, and increases with age. The main cause of DM was family genetic predisposition and sudden shocks. The current study also showed that most diabetic patients suffered from UTIs, especially females, and the main causes of UTI inflammation are E. coli isolates.

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

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

Increasing plasma glucose before the development of type 1 diabetes-the TRIGR study

OBJECTIVE

The β-cell stress hypothesis suggests that increased insulin demand contributes to the development of type 1 diabetes. In the TRIGR trial we set out to assess the profile of plasma glucose and HbA1c before the diagnosis of clinical diabetes compared to nondiabetic children.

RESEARCH DESIGN AND METHODS

A cohort of children (N = 2159) with an affected first-degree relative and increased HLA risk were recruited 2002-2007 and followed until 2017. To study the relationship between plasma glucose/HbA1c and the development of autoantibodies or clinical disease Kaplan-Meir curves were developed. Mixed models were constructed for plasma glucose and HbA1c separately.

RESULTS

A family history of type 2 diabetes was related to an increase in plasma glucose (p < 0.001). An increase in glucose from the previous sample predicted clinical diabetes (p < 0.001) but not autoantibodies. An increase of HbA1c of 20% or 30% from the previous sample predicted the development of any autoantibody (p < 0.003 resp <0.001) and the development of diabetes (p < 0.002 resp <0.001. Participants without autoantibodies had lower HbA1c (mean 5.18%, STD 0.24; mean 33.08 mmol/mol, STD 2.85) than those who progressed to clinical disease (5.31%, 0.42; 34.46 mmol/mol, 4.68; p < 0.001) but higher than those who developed any autoantibody (5.10%, 0.30; 32.21 mmol/mol, 3.49; p < 0.001), or multiple autoantibodies (5.11%, 0.35; 32.26 mmol/mol, 3.92; p < 0.003).

CONCLUSIONS

A pronounced increase in plasma glucose and HbA1c precedes development of clinical diabetes, while the association between plasma glucose or HbA1c and development of autoantibodies is complex. Increased insulin demand may contribute to development of type 1 diabetes.

Implication of epigenetic factors in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease that resulted from the severe destruction of the insulin-producing β cells in the pancreases of individuals with a genetic predisposition. Genome-wide studies have identified HLA and other risk genes associated with T1D susceptibility in humans. However, evidence obtained from the incomplete concordance of diabetes incidence among monozygotic twins suggests that environmental factors also play critical roles in T1D pathogenesis. Epigenetics is a rapidly growing field that serves as a bridge to link T1D risk genes and environmental exposures, thereby modulating the expression of critical genes relevant to T1D development beyond the changes of DNA sequences. Indeed, there is compelling evidence that epigenetic changes induced by environmental insults are implicated in T1D pathogenesis. Herein, we sought to summarize the recent progress in terms of epigenetic mechanisms in T1D initiation and progression, and discuss their potential as biomarkers and therapeutic targets in the T1D setting.

Integrative analyses of TEDDY Omics data reveal lipid metabolism abnormalities, increased intracellular ROS and heightened inflammation prior to autoimmunity for type 1 diabetes

BACKGROUND

The Environmental Determinants of Diabetes in the Young (TEDDY) is a prospective birth cohort designed to study type 1 diabetes (T1D) by following children with high genetic risk. An integrative multi-omics approach was used to evaluate islet autoimmunity etiology, identify disease biomarkers, and understand progression over time.

RESULTS

We identify a multi-omics signature that was predictive of islet autoimmunity (IA) as early as 1 year before seroconversion. At this time, abnormalities in lipid metabolism, decreased capacity for nutrient absorption, and intracellular ROS accumulation are detected in children progressing towards IA. Additionally, extracellular matrix remodeling, inflammation, cytotoxicity, angiogenesis, and increased activity of antigen-presenting cells are observed, which may contribute to beta cell destruction. Our results indicate that altered molecular homeostasis is present in IA-developing children months before the actual detection of islet autoantibodies, which opens an interesting window of opportunity for therapeutic intervention.

CONCLUSIONS

The approach employed herein for assessment of the TEDDY cohort showcases the utilization of multi-omics data for the modeling of complex, multifactorial diseases, like T1D.

Association of Maternal Dietary Components During Pregnancy and/or Lactation with Insulin-Dependent Diabetes Mellitus

CONTEXT

Considering the increasing trend in the incidence of type 1 diabetes mellitus (T1DM), the identification of its environmental determinants, especially those related to the prenatal and lactation period, might ultimately result in primary prevention of the disease. We aimed to review the evidence of the association between mothers' dietary components during pregnancy and/or lactation with T1DM.

EVIDENCE ACQUISITION

An electronic and comprehensive literature search was performed until August 2019 in the international databases, including Web of Science (ISI), PubMed, and Scopus, using the following keywords: type 1 diabetes mellitus, autoimmunity, mother, maternal, diet and lactation in different combinations. Papers related to the objectives of the study were selected.

RESULTS

Based on our review, the maternal consumption of meat, especially processed meat, was associated with increased risk of T1DM, whereas the maternal use of vegetables, potato, low-fat margarine, and berries showed protective effects against the development of T1DM in offspring. There was no significant association between the use of multivitamins and mineral supplements with T1DM, according to the available data. The results of the reviewed studies regarding the association between the maternal use of vitamin D, fatty acids, and coffee during pregnancy with T1DM were not consistent and conclusive.

CONCLUSIONS

Findings of this review indicate that the maternal consumption of some foods is associated with increased or decreased risk of T1DM. However, for some foods or dietary components, including coffee, vitamin D, and fatty acids, the results are not conclusive. We conclude that although maternal diet could influence the development of insulin autoantibodies (IA) and T1DM in offspring, there is no sufficient evidence for most nutrients, and available data are controversial, which should be dealt with in future cohort or interventional studies.

Enterovirus Neutralizing Antibodies, Monocyte Toll Like Receptors Expression and Interleukin Profiles Are Similar Between Non-affected and Affected Siblings From Long-Term Discordant Type 1 Diabetes Multiplex-Sib Families: The Importance of HLA Background

Enteroviruses are main candidates among environmental agents in the development of type 1 diabetes (T1D). However, the relationship between virus and the immune system response during T1D pathogenesis is heterogeneous. This is an interesting paradigm and the search for answers would help to highlight the role of viral infection in the etiology of T1D. The current data is a cross-sectional study of affected and non-affected siblings from T1D multiplex-sib families to analyze associations among T1D, genetic, islet autoantibodies and markers of innate immunity. We evaluated the prevalence of anti-virus antibodies (Coxsackie B and Echo) and its relationships with human leukocyte antigen (HLA) class II alleles, TLR expression (monocytes), serum cytokine profile and islet β cell autoantibodies in 51 individuals (40 T1D and 11 non-affected siblings) from 20 T1D multiplex-sib families and 54 healthy control subjects. The viral antibody profiles were similar among all groups, except for antibodies against CVB2, which were more prevalent in the non-affected siblings. TLR4 expression was higher in the T1D multiplex-sib family's members than in the control subjects. TLR4 expression showed a positive correlation with CBV2 antibody prevalence (rS: 0.45; P = 0.03), CXCL8 (rS: 0.65, P = 0.002) and TNF-α (rS: 0.5, P = 0.01) serum levels in both groups of T1D multiplex-sib family. Furthermore, within these families, there was a positive correlation between HLA class II alleles associated with high risk for T1D and insulinoma-associated protein 2 autoantibody (IA-2A) positivity (odds ratio: 38.8; P = 0.021). However, the HLA protective haplotypes against T1D prevalence was higher in the non-affected than the affected siblings. This study shows that although the prevalence of viral infection is similar among healthy individuals and members from the T1D multiplex-sib families, the innate immune response is higher in the affected and in the non-affected siblings from these families than in the healthy controls. However, autoimmunity against β-islet cells and an absence of protective HLA alleles were only observed in the T1D multiplex-sib members with clinical disease, supporting the importance of the genetic background in the development of T1D and heterogeneity of the interaction between environmental factors and disease pathogenesis despite the high genetic diversity of the Brazilian population.

The Prevalence of Celiac Disease-Specific Auto-Antibodies in Type 1 Diabetes in a Moroccan Population

OBJECTIVE

We aimed to determine the prevalence of specific auto-antibodies to celiac disease (CD) in Moroccan type 1 diabetic (T1D) patients and compare the clinical and biological characteristics of seropositive and seronegative cases.

PATIENTS AND METHODS

A cross-sectional study was carried out on 276 T1D patients including 109 adults and 167 pediatric cases. The screening for CD was performed by an Elisa IgA anti-tissue transglutaminase antibody (tTGA) testing, combined with IgA quantification by nephelometry. Positive-IgA-tTGA cases were secondly tested for anti-endomysial antibodies (EMA) using an immunofluorescence technique, and the IgA deficiency cases were screened for IgG-tTGA. Patients with low positive tTGA titers underwent HLA-DQ2/DQ8 typing. Sociodemographic and clinical data of the patients were collected using a hetero-administered questionnaire. The comparison of clinical and biological data between seropositive and seronegative diabetics was done using independent T, Mann-Whitney U, chi-squared, and Fisher tests, which were considered significant if p value <0.05.

RESULTS

The prevalence of CD-specific auto-antibodies was estimated to be 9.1% (IC = 95%), with 25 positive cases in tTGA and EMA testing. Eight cases displayed low titers of IgA-tTGA, among which 4 were positive for HLA-DQ2, 1 for HLA-DQ8, and 1 for both DQ2 and DQ8. The other 2 cases had a biopsy-proven CD. Compared to seronegative patients, seropositive cases had a higher percentage of associated autoimmune disorders (16% vs. 2.4%, p=0.008), with a significant lower height Z-scores (median: -0.90 (-3.93 to 0.95) vs. -0.51 (-4.54 to 2.18), p=0.029) and a higher HbA1c level (median: 11.30% (7.31 to 16.00) vs. 9.30% (4.40 to17.31), p=0.022).

CONCLUSION

The current study gave evidence of a high prevalence of CD specific auto-antibodies in T1D population. The co-existence of these two conditions was associated with a poor glycemic control, a lower height, and other autoimmune diseases. These findings may suggest the necessity of a systematic screening of CD in T1D patients.

Immunomodulatory Effect of Vitamin D and Its Potential Role in the Prevention and Treatment of Type 1 Diabetes Mellitus-A Narrative Review

Type 1 diabetes mellitus is a chronic autoimmune disease associated with degeneration of pancreatic β-cells that results in an inability to produce insulin and the need for exogenous insulin administration. It is a significant global health problem as the incidence of this disorder is increasing worldwide. The causes are still poorly understood, although it certainly has genetic and environmental origins. Vitamin D formed profusely in the skin upon exposure to sunlight, as well as from dietary sources, exhibits an immunomodulatory effect based on gene transcription control. Indeed, vitamin D can downregulate mechanisms connected with adaptive immunity, induce immunological tolerance and decrease auto-aggression-related inflammation. These properties provide the basis for a preventive and therapeutic role of vitamin D. As many studies have demonstrated, appropriate supplementation with vitamin D reduces the risk of autoimmune diseases, including type 1 diabetes mellitus, and alleviates disease symptoms in patients. The aim of this narrative review is to present the molecular mechanisms for the vitamin D immunomodulatory effect as well as review human clinical studies on the use of vitamin D as adjuvant therapy in type 1 diabetes mellitus.

Fifty years of pancreatic islet pathology in human type 1 diabetes: insights gained and progress made

Type 1 diabetes is increasing in incidence in many parts of the world and it might be imagined that the pathological processes that underlie disease progression are firmly understood. However, this is not the case; rather, our collective understanding is still surprisingly rudimentary. There are various reasons for this but one of the most important is that the target organ (the pancreas) has been examined at, or soon after, diagnosis in only a small number of cases worldwide over the past half a century. This review provides a summary of some of the insights gained from these studies and highlights areas of ongoing uncertainty. In particular, it considers the process of insulitis (a form of islet inflammation that occurs characteristically in type 1 diabetes) and discusses the factors that may influence the access of immune cells to the beta cells. Attention is also drawn to recent evidence implying that two distinct profiles of insulitis exist, which occur differentially in people who develop type 1 diabetes at increasing ages. Emphasis is also placed on the emerging (and somewhat surprising) consensus that the extent of beta cell loss is variable among people with type 1 diabetes and that many (especially those who are older at onset) retain significant numbers of insulin-producing cells long after diagnosis. We conclude by emphasising the importance of renewed efforts to study the human pancreas at disease onset and consider how the current insights may inform the design of future strategies to slow or halt the rate of beta cell loss.

The Role of Epigenetics in Type 1 Diabetes

PURPOSE OF REVIEW

Epigenetics is defined as mitotically heritable changes in gene expression that do not directly alter the DNA sequence. By implication, such epigenetic changes are non-genetically determined, although they can be affected by inherited genetic variation. Extensive evidence indicates that autoimmune diseases including type 1 diabetes are determined by the interaction of genetic and non-genetic factors. Much is known of the genetic causes of these diseases, but the non-genetic effects are less clear-cut. Further, it remains unclear how they interact to cause the destructive autoimmune process. This review identifies the key issues in the genetic/non-genetic interaction, examining the most recent evidence of the role of non-genetic effects in the disease process, including the impact of epigenetic effects on key pathways.

RECENT FINDINGS

Recent research indicates that these pathways likely involve immune effector cells both of the innate and adaptive immune response. Specifically, there is evidence of cell type-specific enrichment in altered DNA methylation, changes which were temporally stable and enriched at gene regulatory elements. Epigenomics remains in its infancy, and we anticipate further studies will define how the interaction of genetic and non-genetic effects induces tissue-specific destruction and enhances our ability to predict, and possibly even modify that process.

Immune interventions to preserve β cell function in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to destruction of pancreatic β cells, lifelong dependence on insulin, and increased morbidity and mortality from diabetes-related complications. Preservation of residual β cells at diagnosis is a major goal because higher levels of endogenous insulin secretion are associated with better short- and long-term outcomes. For the past 3 decades, a variety of immune interventions have been evaluated in the setting of new-onset T1D, including nonspecific immunosuppression, pathway-specific immune modulation, antigen-specific therapies, and cellular therapies. To date, no single intervention has produced durable remission off therapy in most treated patients, but the field has gained valuable insights into disease mechanisms and potential immunologic correlates of success. In particular, T-cell–directed therapies, including therapies that lead to partial depletion or modulation of effector T cells and preservation or augmentation of regulatory T cells, have shown the most success and will likely form the backbone of future approaches. The next phase will see evaluation of rational combinations, comprising one or more of the following: an effector T-depleting or -modulating drug, a cytokine-based tolerogenic (regulatory T-cells–promoting) agent, and an antigen-specific component. The long term goal is to reestablish immunologic tolerance to β cells, thereby preserving residual β cells early after diagnosis or enabling restoration of β-cell mass from autologous stem cells or induced neogenesis in patients with established T1D.

The viral paradigm in type 1 diabetes: Who are the main suspects?

Type 1 diabetes (T1D) is an autoimmune disease characterized by the loss of pancreatic beta cells in the islets of Langerhans. Although genetic predisposition plays an important role in T1D development, studies of identical twins suggest that environmental factors such as viruses and other pathogens may be critical triggers either through direct cytolytic effect and gradual beta cell destruction, or by bystander activation of the immune system. In addition, viruses may circumvent the host immune response and have the capacity to establish chronic lifelong infections. The association of various viral infections with the induction of T1D has been extensively studied at the serological and epidemiological level. However, there is still little evidence from studies of human pancreas to confirm their presence or a causal role in disease pathogenesis. In this review, we identify possible suspects for viral triggers of disease and explain their potential roles in the "viral paradigm" of T1D.

Environmental risk factors for type 1 diabetes

The incidence of type 1 diabetes has risen considerably in the past 30 years due to changes in the environment that have been only partially identified. In this Series paper, we critically discuss candidate triggers of islet autoimmunity and factors thought to promote progression from autoimmunity to overt type 1 diabetes. We revisit previously proposed hypotheses to explain the growth in the incidence of type 1 diabetes in light of current data. Finally, we suggest a unified model in which immune tolerance to β cells can be broken by several environmental exposures that induce generation of hybrid peptides acting as neoautoantigens.

Co-infection with Helicobacter pylori and Epstein-Barr virus in benign upper digestive diseases: An endoscopic and serologic pilot study

BACKGROUND

Some gastric cancers are Epstein-Barr virus associated.

AIM

To assess the prevalence of Helicobacter pylori and viral co-infection in benign upper digestive diseases.

METHODS

One hundred and four outpatients were included in a prospective endoscopic-serologic study. Epstein-Barr virus immunoglobulin G (IgG), immunoglobulin M and viral capsid antigen titres were assayed with an ELISA test. Helicobacter pylori was determined by the modified Giemsa stain and by IgG-chemiluminescence.

RESULTS

The overall prevalence of Helicobacter pylori was 56.7%. Duodenal ulcer patients were infected in 72.5 % of the cases, with the prevalence being 33.3% in functional dyspepsia (p = 0.0008) and 25.8% in reflux patients (p = 0.0001). Epstein-Barr virus IgG was detected in 70.1% of the whole group, 75% of duodenal ulcer patients, 51.2% of functional dyspepsia patients (p = 0.04) and 51.6% of the reflux disease cases (p = 0.04). Co-infection with both agents was detected in 60% of duodenal ulcer patients, 18.1% of functional dyspepsia (p = 0.00014) and 12.9% of reflux disease patients (p = 0.00012). Anti-viral IgG titre displayed a 31.7 ± 3.0 cut-off index in duodenal ulcer, 20.5 ± 3.5 in functional dyspepsia (p = 0.01) and 21.4 ± 3.6 in reflux cases (p = 0.03).

CONCLUSIONS

Both Helicobacter pylori and Epstein-Barr virus, and co-infection with these agents, were significantly more prevalent in duodenal ulcer patients than in dyspeptic/reflux patients.

Insulin resistance in type 1 diabetes mellitus

For long the presence of insulin resistance in type 1 diabetes has been questioned. Detailed metabolic analyses revealed 12%-61% and up to 20% lower whole-body (skeletal muscle) and hepatic insulin sensitivity in type 1 diabetes, depending on the population studied. Type 1 diabetes patients feature impaired muscle adenosine triphosphate (ATP) synthesis and enhanced oxidative stress, predominantly relating to hyperglycemia. They may also exhibit abnormal fasting and postprandial glycogen metabolism in liver, while the role of hepatic energy metabolism for insulin resistance remains uncertain. Recent rodent studies point to tissue-specific differences in the mechanisms underlying insulin resistance. In non-obese diabetic mice, increased lipid availability contributes to muscle insulin resistance via diacylglycerol/protein kinase C isoforms. Furthermore, humans with type 1 diabetes respond to lifestyle modifications or metformin by 20%-60% increased whole-body insulin sensitivity, likely through improvement in both glycemic control and oxidative phosphorylation. Intensive insulin treatment and islet transplantation also increase but fail to completely restore whole-body and hepatic insulin sensitivity. In conclusion, insulin resistance is a feature of type 1 diabetes, but more controlled trials are needed to address its contribution to disease progression, which might help to optimize treatment and reduce comorbidities.

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.

Targeting memory T cells in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to progressive destruction of pancreatic beta cells. Compared to healthy controls, a characteristic feature of patients with T1D is the presence of self-reactive T cells with a memory phenotype. These autoreactive memory T cells in both the CD4(+) and CD8(+) compartments are likely to be long-lived, strongly responsive to antigenic stimulation with less dependence on costimulation for activation and clonal expansion, and comparatively resistant to suppression by regulatory T cells (Tregs) or downregulation by immune-modulating agents. Persistence of autoreactive memory T cells likely contributes to the difficulty in preventing disease progression in new-onset T1D and maintaining allogeneic islet transplants by regular immunosuppressive regimens. The majority of immune interventions that have demonstrated some success in preserving beta cell function in the new-onset period have been shown to deplete or modulate memory T cells. Based on these and other considerations, preservation of residual beta cells early after diagnosis or restoration of beta cell mass by use of stem cell or transplantation technology will require a successful strategy to control the autoreactive memory T cell compartment, which could include depletion, inhibition of homeostatic cytokines, induction of hyporesponsiveness, or a combination of these approaches.

Interferon and interferon-inducible gene activation in patients with type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is thought to be triggered by environmental factors in genetically susceptible individuals. Enteroviruses have been mentioned as the most probable induction component of the disease. Nevertheless, the literature is controversial regarding the association of T1D with viral infection and first-line antiviral defence components, for example type I interferons (IFNs). Our aim was to test the hypothesis that an abnormality in IFN-stimulated gene patterns may cause a failure in immunological tolerance and, thereby, initiate T1D as an autoimmune disorder. We studied material from 64 T1D and 36 control subjects, divided into two age groups: <10 years and ≥10 years old. Using a relative gene expression method, we observed a lower expression of interferon-induced helicase 1 (IFIH1) and other type I IFN-induced genes in the blood cells of T1D subjects, especially subjects under 10 years old, in spite of their higher IFN levels as measured by the pSTAT1-inducing capacity of their sera. Likewise, freshly purified CpG-stimulated cells from T1D patients showed significantly lower upregulation of IFN-induced genes, that is IFIH1 and CXCL10, compared to cells from the control group. The identified dysregulation in the IFN-α-induced antiviral response in T1D patients, especially in early childhood, could be one of the factors affecting T1D development.

p204-Mediated innate antiviral responses in mouse adipose cells and their effects on cell functions

Viruses can infect adipose tissues. However, innate antiviral responses in adipose cells and their effects on adipocyte function have not yet been intensively investigated. In this study, p204-initiated innate antiviral responses in mouse adipose cells were examined. Cytosolic DNA sensor p204 and its signaling adaptor stimulator of interferon (IFN) genes (STING) were constitutively expressed in primary preadipocytes. Synthetic herpes simplex viral DNA (HSV60), a p204 ligand, induced type I IFN expression by activating IFN regulatory factor 3. Major antiviral proteins, including IFN-stimulating gene 15, 2',5'-oligoadenylate synthetase and Mx GTPase 1, in preadipocytes were upregulated by HSV60. HSV60-triggered innate antiviral responses were significantly reduced by inhibition of p204 signaling with specific small interfering RNA targeting p204 or STING. HSV60 inhibited the differentiation of preadipocytes to mature adipocytes and enhanced the proliferation of adipose cells. Moreover, HSV60 induced innate antiviral responses in mature adipocytes and inhibited expressions of several adipokines, including leptin, adiponectin and resistin. These results indicated that p204 initiated innate antiviral responses in adipose cells, thereby modulating adipocyte function.

Influence of host immunoregulatory genes, ER stress and gut microbiota on the shared pathogenesis of inflammatory bowel disease and Type 1 diabetes

Inflammatory bowel disease (IBD) with its two distinct entities, Crohn's disease and ulcerative colitis, and Type 1 diabetes mellitus (T1D) are autoimmune diseases. The prevalence of these diseases continues to rapidly rise in the industrialized world. Despite the identification of several genetic loci that are associated with both IBD and T1D, thus far, there is a paucity of epidemiological data to support a clinical overlap. In an effort to better understand the underlying pathogenic mechanisms of both IBD and T1D, this review summarizes the literature about these related autoimmune diseases, describes the most recent advances in their etiopathogenesis and emphasizes the genetic and nongenetic factors that exercise a differential influence. Genome-wide association studies have identified genetic loci with a role in immune response regulation that are linked to both IBD (particularly Crohn's disease) and T1D. Some of these genetic loci (e.g., IL-18RAP) have a divergent role, conferring risk for one disease and protection for the other. Recent evidence highlights an important role of gut microbiota and cellular responses (e.g., endoplasmic reticulum stress) in the pathogenesis of both IBD and T1D.

Interferon stimulated gene 15 has an anti-apoptotic effect on MIN6 cells

Type 1 diabetes, one of two major forms of diabetes, results from the complete destruction of pancreatic beta cells. Viral infection has been suggested to be a trigger of beta cell destruction, the pathogenesis of type 1 diabetes. The aim of this study was to clarify the role of the protein encoded by intherferon stimulated gene (ISG) 15, an antiviral effector, in the development of this clinical entity. We used the mouse beta cell line MIN6 to investigate the role of ISG15 and paid special attention to apoptosis. Although not detected in native MIN6 cells, free ISG15 and ISG15 conjugated proteins were both present in dose-dependently increased amounts following stimulation with interferon alpha. As assessed both by caspase 3/7 activity and an annexin V assay, the percentage of apoptotic MIN6 cells (after exposure to the inflammatory cytokines of interleukin-1beta plus interferon gamma or tumor necrosis factor alpha) was decreased by pretreatment with adenovirus-expressing ISG15 and increased by expressing a short hairpin RNA directed against ISG15. In conclusion, ISG15 has an anti-apoptotic effect on MIN6 cells. Thus, promoting ISG15 expression in the pancreatic beta cells could be a potential therapeutic approach for patients with type 1 diabetes.

New opportunities: harnessing induced pluripotency for discovery in diabetes and metabolism

The landmark discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has transformed regenerative biology. Previously, insights into the pathogenesis of chronic human diseases have been hindered by the inaccessibility of patient samples. However, scientists are now able to convert patient fibroblasts into iPSCs and differentiate them into disease-relevant cell types. This ability opens new avenues for investigating disease pathogenesis and designing novel treatments. In this review, we highlight the uses of human iPSCs to uncover the underlying causes and pathological consequences of diabetes and metabolic syndromes, multifactorial diseases whose etiologies have been difficult to unravel using traditional methodologies.

The genetics of innate immunity sensors and human disease

Since their discovery, innate immunity microbial sensors have been increasingly studied and shown to play a critical role in innate responses to microbes in several experimental in vitro, ex vivo, and animal models. However, their role in the human response to infection in natural conditions has just started to be deciphered, by means of clinical studies of primary immunodeficiencies and epidemiological genetic studies. Here, we summarize the major findings concerning the genetic diversity of the various families of microbial sensors in humans, and of other molecules involved in the signaling pathways they trigger. Specifically, we review the genetic associations, revealed by both clinical and epidemiological genetics studies, of microbial sensors from five different families: Toll-like receptors, C-type lectin receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. In particular, we consider the relationships between variation at the genes encoding these molecules and susceptibility to and the severity of infectious diseases and other clinical conditions associated with immune dysfunction, including autoimmunity, inflammation, allergy, and cancer. Despite the fact that the genetic links between innate immunity sensors and human disorders remain still limited, human genetics studies are increasingly improving our understanding of the genuine functions of microbial sensors and downstream signaling molecules in the natural setting.

Enteroviral pathogenesis of type 1 diabetes: queries and answers

PURPOSE OF REVIEW

Type 1 diabetes (T1D) results from interplay between genetic predisposition, immune system, and environmental factors. Epidemiological and experimental data strongly suggest a role for enteroviruses in the development of T1D, but a lot of controversies and unanswered questions remained. This review focuses on issues that are fueling debate.

RECENT FINDINGS

Beyond HLA genes, which provide genetic susceptibility for T1D, other loci have been identified to be associated with the disease. There is a link between T1D and single-nucleotide polymorphisms (SNPs) in the interferon-induced helicase 1 (IFIH1) gene that encodes melanoma differentiation-associated protein 5 (MDA5). This protein is a cytoplasmic sensor for viruses especially coxsackieviruses B, the most incriminated enteroviruses in T1D pathogenesis. Upon viral infection, MDA5 stimulates the production of mediators of the innate antiviral immune response, which is believed to play a role in a 'bystander activation' scenario. Rare variants of IFIH1 through a lost or reduced expression of the protein are protective against T1D, whereas common IFIH1 SNPs are associated with the disease. However, a clear association has not been yet established between T1D-associated IFIH1 polymorphisms and enterovirus detection.

SUMMARY

Literature have accumulated a lot of evidence supporting that enteroviruses can contribute, at least in some patients, to the pathogenesis of T1D through various mechanisms. But it is still a challenge to date to prove a causal relationship between enteroviruses and T1D. Future studies may lead to a better understanding of this relationship and ultimately can help toward disease prevention.

The case for virus-induced type 1 diabetes

PURPOSE OF REVIEW

Type 1 diabetes (T1D) results from the immune-mediated destruction of pancreatic insulin-producing cells because of the interaction among genetic susceptibility, the immune system and environmental factor(s). A possible role of viral infections in T1D pathogenesis has been hypothesized for some time; however, only in the most recent years, studies performed at the molecular and cellular level are starting to shed light on this issue.

RECENT FINDINGS

Studies in animal models and in man have shown that viruses can indeed infect pancreatic beta-cells, inducing islet inflammation and functional damage. In addition, recent in-situ investigations performed on pancreatic tissue samples have provided evidence that in addition to adaptive immune response, innate immunity is involved in T1D pathogenesis and the whole pancreas (not only its endocrine portion) is infiltrated by immune-mediated phenomena.

SUMMARY

The established role of inflammation in the insulitic process and the increasing evidence in support of the contribution of viral infections to a proinflammatory islet scenario are strongly suggestive that viruses may indeed contribute to beta-cell damage and dysfunction, thus setting the stage for the design of antiviral strategies (e.g. vaccines and antiviral drugs) aimed at protecting the beta-cells.

The pancreatic β cell and type 1 diabetes: innocent bystander or active participant?

Type 1 diabetes mellitus (T1DM) is a chronic disease resulting from destruction of insulin-producing pancreatic β cells. Genetic and environmental factors contribute to T1DM onset. Use of high-throughput DNA sequencing has allowed geneticists to perform genome-wide association studies (GWAS) to identify novel gene loci associated with T1DM. Interestingly, >50% of these genes encode products that are expressed in β cells. These studies, coupled with emerging molecular evidence that β cells are impaired by gain-of-function or loss-of-function of these loci, suggest an active role for the β cell in eliciting its own demise. Although immune dysregulation plays a vital role in T1DM pathogenesis, understanding the mechanisms contributing to β cell failure may lead to new strategies to preserve or improve β cell function in patients with T1DM.

Progress in immune-based therapies for type 1 diabetes

Immune-based therapies that prevent type 1 diabetes or preserve metabolic function remaining at diagnosis have become a major objective for funding agencies and international trial consortia, and receive backing from notable patient advocate groups. The development of immune-based therapeutic strategies in this arena requires a careful balancing of the risks of the therapy against the potential benefits, because many individuals are diagnosed or identified as being at increased risk of disease in early childhood, a period when manipulation of the developing immune system should be undertaken with caution. In addition, a therapy exists (daily insulin injection) that is life-saving in the acute stages of disease and can be used effectively over a lifetime as maintenance. Conversely, the disease is increasing in incidence; is peaking in ever-younger age groups; carries significant risk of increased morbidity and early mortality; and remains difficult to manage effectively in many settings. With these issues in mind, in this article we review progress towards immune-based strategies for this chronic autoimmune disease.

Immunological biomarkers: catalysts for translational advances in autoimmune diabetes

In a recent workshop organized by the JDRF focused on the 'Identification and Utilization of Robust Biomarkers in Type1 Diabetes', leaders in the field of type 1 diabetes (T1D)/autoimmunity and assay technology came together from academia, government and industry to assess the current state of the field, evaluate available resources/technologies and identify gaps that need to be filled for moving the field of T1D research forward. The highlights of this workshop are discussed in this paper, as well as the proposal for a larger, planned consortium effort, incorporating a JDRF Biomarker Core, to foster collaboration and accelerate progress in this critically needed area of T1D research.

Genetic risk factors for pancreatic disorders

A combination of genetic, environmental, and metabolic factors contribute to the development and recurrence of acute and chronic pancreatitis; information on all of these is required to manage patients effectively. For example, variants that affect regulation of the protease, serine (PRSS)1-PRSS2, and claudin (CLDN)2 loci, rather than their coding sequences, interact with other genetic and environmental factors to affect disease development. New strategies are needed to use these data and determine their contribution to pathogenesis, because these variants differ from previously studied, rare variants in exons (coding regions) of genes such as PRSS1, SPINK1, cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin (CTR)C, and calcium-sensing receptor (CASR). Learning how various genetic factors affect pancreatic cells and systems could lead to etiology-based therapies rather than treatment of symptoms.

Early life socioeconomic indicators and risk of type 1 diabetes in children and young adults

OBJECTIVE

To examine the potential role of 2 early-life socioeconomic indicators, parental education, and crowding index, on risk of type 1 diabetes (T1DM) in patients up to age 29 years to test heterogeneity by age at onset according to the hygiene hypothesis.

STUDY DESIGN

The study base was 330 950 individuals born from 1967 to 2006 who resided in the city of Turin at any time between 1984 and 2007. Data on their early life socioeconomic position were derived from the Turin Longitudinal Study; 414 incident cases of T1DM up to age 29 years were derived from the Turin T1DM registry.

RESULTS

Socioeconomic indicators had opposing effects on risk of T1DM in different age at onset subgroups. In a Poisson regression model that included both socioeconomic indicators, there was a 3-fold greater risk of T1DM (relative risk 2.91, 95% CI 0.99-8.56) in children age 0-3 years at diagnosis living in crowded houses. In the 4- to 14-year subgroup, a low parental educational level had a protective effect (relative risk 0.50, 95% CI 0.29-0.84), and the effect of crowding nearly disappeared. In the 15- to 29-year subgroup, neither crowding nor parental educational level was clearly associated with the incidence of T1DM.

CONCLUSIONS

We provide evidence of heterogeneity by age at onset of the association between early-life socioeconomic indicators and the risk of T1DM. This finding is consistent with the hypothesis that infectious agents in the perinatal period may increase the risk, whereas in the following years they may become protective factors (hygiene hypothesis).

Immunological pathways to β-cell damage in Type 1 diabetes

Following almost 30 years of intensive research, initiated by the observation that Type 1 diabetes development is associated with a characteristic pancreatic immune cell infiltrate, a picture is emerging of which of the diverse effector arms of the immune system are involved in β-cell destruction. Like any chronic pathology, there is considerable complexity, and our ability to model the disease is hampered by a lack of ready access to the target organ and limited longitudinal analyses. However, it seems that putative pathways can start to be ruled in and out, in part as a result of focused mechanistic studies that make use of new technologies, and in part through analysis of the outcomes of clinical trials of new agents aimed at halting the disease process. The picture that emerges suggests a pathway to prevention that may require combinations of therapeutic agents that target different aspects of the immune system and will need to be used with due attention to their risk-benefit profiles.

Pancreatic islet autoimmunity

Type 1 diabetes (T1D) represents 10 to 15% of all forms of diabetes. Its incidence shows a consistent rise in all countries under survey. Evidence for autoimmunity in human T1D relies on the detection of insulitis, of islet cell antibodies, of activated β-cell-specific T lymphocytes and on the association of T1D with a restricted set of class II major histocompatibility complex (MHC) alleles. However, mechanisms that initiate the failure of immune tolerance to β-cell autoantigens remain elusive in common forms of T1D. T1D commonly develop as a multifactorial disease in which environmental factors concur with a highly multigenic background. The disease is driven by the activation of T-lymphocytes against pancreatic β-cells. Several years elapse between initial triggering of the autoimmune response to β cells, as evidenced by the appearance or islet cell autoantibodies, and the onset of clinical diabetes, defining a prediabetes stage. Active mechanisms hold back autoreactive effector T-cells in prediabetes, in particular a subset of CD4+ T-cells (T(reg)) and other regulatory T-cells, such as invariant NKT cells. There is evidence in experimental models that systemic or local infections can trigger autoimmune reactions to β-cells. However, epidemiological observations that have accumulated over years have failed to identify undisputable environmental factors that trigger T1D. Moreover, multiple environmental factors may intervene in the disease evolution and protective as weel as triggering environmental factors may be involved. Available models also indicate that local signals within the islets are required for full-blown diabetes to develop. Many autoantigens that are expressed by β-cells but also by the other endocrine islet cells and by neurons are recognized by lymphocytes along the development of T1D. The immune image of β-cells is that of native components of the β-cell membrane, as seen by B-lymphocytes, and of fragments of intracellular β-cell proteins in the form of peptides loaded onto class I MHC molecules on the β-cell surface and class I and class II molecules onto professional antigen presenting cells. Given the key role of T lymphocytes in T1D, the cartography of autoantigen-derived peptides that are presented to class I-restricted CD8(+) T-cells and class II-restricted CD4(+) T-cells is of outmost importance and is a necessary step in the development of diagnostic T-cell assays and of immunotherapy of T1D.

Broadening the translational immunology landscape

It is just over 5 years sinceClinical and Experimental Immunology came under the direction of a new team of Editors and made a concerted effort to refresh its approach to promoting clinical and applied immunology through its pages. There were two major objectives: to foster papers in a field which, at the time, we loosely termed ‘translational immunology’; and to create a forum for the presentation and discussion of immunology that is relevant to clinicians operating in this space. So, how are we doing with these endeavours? This brief paper aims to summarize some of the key learning points and successes and highlight areas in which translational gaps remain.

The status of serum γ-interferonand antiviral antibodies in patients with type I and type 2 diabetes: A comparative study

OBJECTIVES

There is an association between viral infection and development of diabetes mellitus. This study aimed to investigate the role of rubella virus, cytomegalovirus and coxsackievirus in patients with type 1 (T1D) and type 2 (T2D) diabetes mellitus in respect to the glycemic control and immune response presented by serum γ-interferon leveland antiviral antibodies.

MATERIALS AND METHODS

A total number of 160 (70 male and 90 female) T1D and 75 T2D (25 male and 50 female) patients allocated randomly from Martyr Layla Qasm center for diabetes mellitus in Erbil, Iraq, were enrolled in the study. Serum IgG antibody (I.U./mL) against rubella virus, cytomegalovirus coxsackievirus as well as serum interferon-g were determined.

RESULTS

Type-1 diabetic patients with positive anti-coxsakievirus antibody presented with significantly shorter duration of illness (4.822 ± 2.442 year) and poorer glycemic control (HbA1c %: 9.895 ± 1.272) This observation was not noticed with other viral infection as well as in T2D. Significant alterations in serum interferon-g (8.051 ± 13.371 pg/ml) were observed in T1D and related to coxasackievirus infection (13 patients had a level higher than 10.975 pg/ml; the upper limit of 95% C.I of control, and 34 had a level less than 4.457 pg/ml; the lower limit of 95% C.I of control).

CONCLUSIONS

Subjects with type 1 diabetes and Coxsackie infections seem to have a different immunological and clinical profile. This needs further study.

NKG2D blockade facilitates diabetes prevention by antigen-specific Tregs in a virus-induced model of diabetes

It is thought that viral infections might jeopardize regulatory T cell therapy in type 1 diabetes. Viral infections can lead to surface expression of ligands for the activating NKG2D receptor, such as retinoic acid early transcript 1 (Rae-1), whose expression on beta-cells recruits NKG2D(+) autoreactive CD8(+) T cells. Both in men and mice, autoreactive cytotoxic T cells express NKG2D. We showed that NKG2D expression increased on CD4(+) and CD8(+) T cells during virus-induced diabetes development in the rat insulin promotor (RIP) Lymphocytic Choriomeningitis Virus (LCMV) model. Combination treatment with anti-NKG2D and antigen-specific regulatory T cells (Treg), at doses inefficacious in mono-treatment, synergized to prevent diabetes in 75% of the virus-infected RIP-LCMV mice. Nevertheless, NKG2D blockade alone failed to reverse recent-onset diabetes in non-obese diabetic (NOD) mice, despite downregulation of NKG2D on NK cells in the blood and CD8(+) T cells in the spleen and pancreatic lymph nodes. Our data suggest that blocking the interaction of NKG2D with it ligands is insufficient to protect against diabetes when a strong inflammatory process actively drives NKG2D upregulation, but should be considered to help maintaining Treg functionality during ongoing pancreatic inflammation.

Immunology in the clinic review series; focus on type 1 diabetes and viruses: the enterovirus link to type 1 diabetes: critical review of human studies

The hypothesis that under some circumstances enteroviral infections can lead to type 1 diabetes (T1D) was proposed several decades ago, based initially on evidence from animal studies and sero-epidemiology. Subsequently, enterovirus RNA has been detected more frequently in serum of patients than in control subjects, but such studies are susceptible to selection bias and reverse causality. Here, we review critically recent evidence from human studies, focusing on longitudinal studies with potential to demonstrate temporal association. Among seven longitudinal birth cohort studies, the evidence that enterovirus infections predict islet autoimmunity is quite inconsistent in our interpretation, due partially, perhaps, to heterogeneity in study design and a limited number of subjects studied. An association between enterovirus and rapid progression from autoimmunity to T1D was reported by one longitudinal study, but although consistent with evidence from animal models, this novel observation awaits replication. It is possible that a potential association with initiation and/or progression of islet autoimmunity can be ascribed to a subgroup of the many enterovirus serotypes, but this has still not been investigated properly. There is a need for larger studies with frequent sample intervals and collection of specimens of sufficient quality and quantity for detailed characterization of enterovirus. More research into the molecular epidemiology of enteroviruses and enterovirus immunity in human populations is also warranted. Ultimately, this knowledge may be used to devise strategies to reduce the risk of T1D in humans.

Viruses and type 1 diabetes: ignorance acquires a better vocabulary

The hypothesis that a virus might in some way be involved in the causation of type 1 diabetes has a long history, but decades of research have failed to resolve the issue beyond reasonable doubt. Viruses could potentially play a primary role in the pathogenesis of type 1 diabetes by initiating autoimmunity, a secondary role by promoting established immune responses, or a tertiary role by precipitating the onset of hyperglycaemia. There is currently little evidence to suggest that viruses play a primary role in the causation of type 1 diabetes, let alone a necessary or sufficient role. Secondary or tertiary roles remain possible, but have yet to be confirmed in prospective studies.

Immunology in the clinic review series; focus on type 1 diabetes and viruses: the innate immune response to enteroviruses and its possible role in regulating type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease arising as a consequence of a misdirected T cell response to the pancreatic beta cell. In recent years, there has been a growing interest in the innate immune system as a regulator of disease development. Genome-wide association studies have identified diabetes-associated polymorphisms in genes encoding proteins with functions related to the innate immune response. Moreover, enteroviruses, known to activate a strong innate immune response, have been implicated in the disease pathogenesis. In this review, we discuss the innate immune response elicited by enteroviruses and how this response may regulate T1D development.

Immunology in the clinic review series; focus on type 1 diabetes and viruses: role of antibodies enhancing the infection with Coxsackievirus-B in the pathogenesis of type 1 diabetes

Type 1 diabetes results from an interaction between genetic and environmental factors. Coxsackieviruses B (CV-B) are major environmental candidates, as suggested by epidemiological and experimental studies. The mechanisms leading to the disease involve interactions between the virus, host target tissue (pancreas) and the immune system. The infection of target cells with viruses can be prevented by antibodies. Conversely, the infection can be enhanced by antibodies. The antibody-dependent enhancement (ADE) of infection has been described with various viruses, especially Picornaviruses. In mice infected with CV-B3 this phenomenon resulted in an extended inflammatory reaction and myocarditis. In the human system non-neutralizing antibodies can increase the infection of monocytes with CV-B4 and stimulate the production of interferon (IFN)-α by these cells in vitro. CV-B4/immunoglobulin (Ig)G immune complexes interacted with a specific viral receptor [Coxsackievirus and adenovirus receptor (CAR)] and with IgG Fc fraction receptors (FcγRII and FcγRIII) at the surface of monocytes. The virus-antibody complexes are internalized (CAR) and receptors for the Fc of IgG (FcγRII and FcγRIII). Such antibodies have been detected in patients with type 1 diabetes and they could be responsible for the presence of enteroviral RNA and IFN-α in peripheral blood mononuclear cells (PBMC) of these individuals. The target of enhancing antibodies has been identified as the VP4 protein, which allowed the detection of these antibodies by enzyme-linked immunosorbent assay (ELISA). It cannot be excluded that antibodies enhancing the infection with CV-B may play a role in the pathogenesis of type 1 diabetes, induced or aggravated by these viruses. They can cause a viral escape from the immune response and may participate in the spreading of viruses to β cells. Whether enhancing antibodies raised against VP4 can play a role in iterative homologous and/or heterologous CV-B infections and in the persistence of viruses within the host deserves further study.

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: how viral infections modulate beta cell function

Type 1 diabetes mellitus (T1DM) is a multi-factorial immune-mediated disease characterized by the autoimmune destruction of insulin-producing pancreatic islet beta cells in genetically susceptible individuals. Epidemiological evidence has also documented the constant rise in the incidence of T1DM worldwide, with viral infections representing one of the candidate environmental risk factors identified by several independent studies. In fact, epidemiological data showed that T1DM incidence increases after epidemics due to enteroviruses and that enteroviral RNA can be detected in the blood of >50% of T1DM patients at the time of disease onset. Furthermore, both in-vitro and ex-vivo studies have shown that viruses can infect pancreatic beta cells with consequent effects ranging from functional damage to cell death.