Coxsackievirus infection as an environmental factor in the etiology of type 1 diabetes

T-Cell Receptor Sequences Identify Combined Coxsackievirus-Streptococci Infections as Triggers for Autoimmune Myocarditis and Coxsackievirus-Clostridia Infections for Type 1 Diabetes

Recent research suggests that T-cell receptor (TCR) sequences expanded during human immunodeficiency virus and SARS-CoV-2 infections unexpectedly mimic these viruses. The hypothesis tested here is that TCR sequences expanded in patients with type 1 diabetes mellitus (T1DM) and autoimmune myocarditis (AM) mimic the infectious triggers of these diseases. Indeed, TCR sequences mimicking coxsackieviruses, which are implicated as triggers of both diseases, are statistically significantly increased in both T1DM and AM patients. However, TCRs mimicking Clostridia antigens are significantly expanded in T1DM, whereas TCRs mimicking Streptococcal antigens are expanded in AM. Notably, Clostridia antigens mimic T1DM autoantigens, such as insulin and glutamic acid decarboxylase, whereas Streptococcal antigens mimic cardiac autoantigens, such as myosin and laminins. Thus, T1DM may be triggered by combined infections of coxsackieviruses with Clostridia bacteria, while AM may be triggered by coxsackieviruses with Streptococci. These TCR results are consistent with both epidemiological and clinical data and recent experimental studies of cross-reactivities of coxsackievirus, Clostridial, and Streptococcal antibodies with T1DM and AM antigens. These data provide the basis for developing novel animal models of AM and T1DM and may provide a generalizable method for revealing the etiologies of other autoimmune diseases. Theories to explain these results are explored.

Investigating the virulence of coxsackievirus B6 strains and antiviral treatments in a neonatal murine model

Coxsackievirus B6 (CVB6), a member of the human enterovirus family, is associated with severe diseases such as myocarditis in children. However, to date, only a limited number of CVB6 strains have been identified, and their characterization in animal models has been lacking. To address this gap, in this study, a neonatal murine model of CVB6 infection was established to compare the replication and virulence of three infectious-clone-derived CVB6 strains in vivo. The results showed that following challenge with a lethal dose of CVB6 strains, the neonatal mice rapidly exhibited a series of clinical signs, such as weight loss, limb paralysis, and death. For the two high-virulence CVB6 strains, histological examination revealed myocyte necrosis in skeletal and cardiac muscle, and immunohistochemistry confirmed the expression of CVB6 viral protein in these tissues. Real-time PCR assay also revealed higher viral loads in the skeletal and cardiac muscle than in other tissues at different time points post infection. Furthermore, the protective effect of passive immunization with antisera and a neutralizing monoclonal antibody against CVB6 infection was evaluated in the neonatal mouse model. This study should provide insights into the pathogenesis of CVB6 and facilitate further research in the development of vaccines and antivirals against CVBs.

Clostridia and Enteroviruses as Synergistic Triggers of Type 1 Diabetes Mellitus

What triggers type 1 diabetes mellitus (T1DM)? One common assumption is that triggers are individual microbes that mimic autoantibody targets such as insulin (INS). However, most microbes highly associated with T1DM pathogenesis, such as coxsackieviruses (COX), lack INS mimicry and have failed to induce T1DM in animal models. Using proteomic similarity search techniques, we found that COX actually mimicked the INS receptor (INSR). Clostridia were the best mimics of INS. Clostridia antibodies cross-reacted with INS in ELISA experiments, confirming mimicry. COX antibodies cross-reacted with INSR. Clostridia antibodies further bound to COX antibodies as idiotype-anti-idiotype pairs conserving INS-INSR complementarity. Ultraviolet spectrometry studies demonstrated that INS-like Clostridia peptides bound to INSR-like COX peptides. These complementary peptides were also recognized as antigens by T cell receptor sequences derived from T1DM patients. Finally, most sera from T1DM patients bound strongly to inactivated Clostridium sporogenes, while most sera from healthy individuals did not; T1DM sera also exhibited evidence of anti-idiotype antibodies against idiotypic INS, glutamic acid decarboxylase, and protein tyrosine phosphatase non-receptor (islet antigen-2) antibodies. These results suggest that T1DM is triggered by combined enterovirus-Clostridium (and possibly combined Epstein-Barr-virus-Streptococcal) infections, and the probable rate of such co-infections approximates the rate of new T1DM diagnoses.

Maternal provisions in type 1 diabetes: Evidence for both protective & pathogenic potential

Maternal influences on the immune health and development of an infant begin in utero and continue well into the postnatal period, shaping and educating the child's maturing immune system. Two maternal provisions include early microbial colonizers to initiate microbiota establishment and the transfer of antibodies from mother to baby. Maternal antibodies are a result of a lifetime of antigenic experience, reflecting the infection history, health and environmental exposure of the mother. These same factors are strong influencers of the microbiota, inexorably linking the two. Together, these provisions help to educate the developing neonatal immune system and shape lymphocyte repertoires, establishing a role for external environmental influences even before birth. In the context of autoimmunity, the transfer of maternal autoantibodies has the potential to be harmful for the child, sometimes targeting tissues and cells with devastating consequences. Curiously, this does not seem to apply to maternal autoantibody transfer in type 1 diabetes (T1D). Moreover, despite the rising prevalence of the disease, little research has been conducted on the effects of maternal dysbiosis or antibody transfer from an affected mother to her offspring and thus their relevance to disease development in the offspring remains unclear. This review seeks to provide a thorough evaluation of the role of maternal microorganisms and antibodies within the context of T1D, exploring both their pathogenic and protective potential. Although a definitive understanding of their significance in infant T1D development remains elusive at present, we endeavor to present what has been learned with the goal of spurring further interest in this important and intriguing question.

Environmental Determinants of Type 1 Diabetes: From Association to Proving Causality

The rising incidence of type 1 diabetes (T1D) cannot be ascribed to genetics alone, and causative environmental triggers and drivers must also be contributing. The prospective TEDDY study has provided the greatest contributions in modern time, by addressing misconceptions and refining the search strategy for the future. This review outlines the evidence to date to support the pathways from association to causality, across all stages of T1D (seroconversion to beta cell failure). We focus on infections and vaccinations; infant growth and childhood obesity; the gut microbiome and the lifestyle factors which cultivate it. Of these, the environmental determinants which have the most supporting evidence are enterovirus infection, rapid weight gain in early life, and the microbiome. We provide an infographic illustrating the key environmental determinants in T1D and their likelihood of effect. The next steps are to investigate these environmental triggers, ideally though gold-standard randomised controlled trials and further prospective studies, to help explore public health prevention strategies.

Inhibition of oxidative metabolism by nitric oxide restricts EMCV replication selectively in pancreatic beta-cells

Environmental factors, such as viral infection, are proposed to play a role in the initiation of autoimmune diabetes. In response to encephalomyocarditis virus (EMCV) infection, resident islet macrophages release the pro-inflammatory cytokine IL-1β, to levels that are sufficient to stimulate inducible nitric oxide synthase (iNOS) expression and production of micromolar levels of the free radical nitric oxide in neighboring β-cells. We have recently shown that nitric oxide inhibits EMCV replication and EMCV-mediated β-cell lysis and that this protection is associated with an inhibition of mitochondrial oxidative metabolism. Here we show that the protective actions of nitric oxide against EMCV infection are selective for β-cells and associated with the metabolic coupling of glycolysis and mitochondrial oxidation that is necessary for insulin secretion. Inhibitors of mitochondrial respiration attenuate EMCV replication in β-cells, and this inhibition is associated with a decrease in ATP levels. In mouse embryonic fibroblasts (MEFs), inhibition of mitochondrial metabolism does not modify EMCV replication or decrease ATP levels. Like most cell types, MEFs have the capacity to uncouple the glycolytic utilization of glucose from mitochondrial respiration, allowing for the maintenance of ATP levels under conditions of impaired mitochondrial respiration. It is only when MEFs are forced to use mitochondrial oxidative metabolism for ATP generation that mitochondrial inhibitors attenuate viral replication. In a β-cell selective manner, these findings indicate that nitric oxide targets the same metabolic pathways necessary for glucose stimulated insulin secretion for protection from viral lysis.

Prediction of new potential associations between LncRNAs and environmental factors based on KATZ measure

The associations between genetic and environmental factors (EFs) are significant to understand the development and progression of many complex human diseases. There have been many research studies concerning genetic factors (protein-coding genes, microRNAs) and EFs but limited research addressing the associations between long noncoding RNAs (lncRNAs) and EFs. LncRNAs of more than 200 nucleotides are an important class of non-coding transcripts and are effective in the organization of gene expressions and, therefore, on the formation of diseases. Environmental factors can alter the expression patterns of some lncRNAs, so a thorough understanding of the associations between lncRNAs and environmental factors will contribute to the understanding of the mechanisms of many complex diseases at the molecular level. In this study, we have developed a model based on the KATZ measure to find potential new associations between lncRNAs and EFs by using the DLREFD database, which contains proven associations between lncRNAs and EFs. The KATZ measure and Gaussian interaction profile kernel similarity were used to predict new potential associations between lncRNAs and EFs. The AUC results obtained by global leave-one-out cross-validation and 2-fold and 5-fold cross-validations were 0.855, 0.827, 0.838, respectively. These results show that our model can predict new potential associations between lncRNAs and EFs with high reliability. Also, the results obtained in case studies demonstrate the effectiveness of our model.

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

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

Sex differences underlying pancreatic islet biology and its dysfunction

Background

The sex of an individual affects glucose homeostasis and the pathophysiology, incidence, and prevalence of diabetes as well as the response to therapy.

Scope of the review

This review focuses on clinical and experimental sex differences in islet cell biology and dysfunction during development and in adulthood in human and animal models. We discuss sex differences in β-cell and α-cell function, heterogeneity, and dysfunction. We cover sex differences in communication between gonads and islets and islet-cell immune interactions. Finally, we discuss sex differences in β-cell programming by nutrition and other environmental factors during pregnancy.

Major conclusions

Important sex differences exist in islet cell function and susceptibility to failure. These differences represent sex-related biological factors that can be harnessed for gender-based prevention of and therapy for diabetes.

A Bipartite Network and Resource Transfer-Based Approach to Infer lncRNA-Environmental Factor Associations

Phenotypes and diseases are often determined by the complex interactions between genetic factors and environmental factors (EFs). However, compared with protein-coding genes and microRNAs, there is a paucity of computational methods for understanding the associations between long non-coding RNAs (lncRNAs) and EFs. In this study, we focused on the associations between lncRNA and EFs. By using the common miRNA partners of any pair of lncRNA and EF, based on the competing endogenous RNA (ceRNA) hypothesis and the technique of resources transfer within the experimentally-supported lncRNA-miRNA and miRNA-EF association bipartite networks, we propose an algorithm for predicting new lncRNA-EF associations. Results show that, compared with another recently-proposed method, our approach is capable of predicting more credible lncRNA-EF associations. These results support the validity of our approach to predict biologically significant associations, which could lead to a better understanding of the molecular processes.

On the pathogenesis of insulin-dependent diabetes mellitus: the role of microbiota

Type 1 diabetes (T1D) is an autoimmune disorder characterized by the selective destruction of insulin-producing β cells as result of a complex interplay between genetic, stochastic and environmental factors in genetically susceptible individuals. An increasing amount of experimental data from animal models and humans has supported the role played by imbalanced gut microbiome in T1D pathogenesis. The commensal intestinal microbiota is fundamental for several physiologic mechanisms, including the establishment of immune homeostasis. Alterations in its composition have been correlated to changes in the gut immune system, including defective tolerance to food antigens, intestinal inflammation and enhanced gut permeability. Early findings reported differences in the intestinal microbiome of subjects affected by prediabetes or overt disease compared to healthy individuals. The present review focuses on microbiota-host homeostasis, its alterations, factors that influence microbiome composition and discusses their putative correlation with T1D development. Further studies are necessary to clarify the role played by microbiota modifications in the processes that cause enhanced permeability and the autoimmune mechanisms responsible for T1D onset.

Phenylthiomethyl Ketone-Based Fragments Show Selective and Irreversible Inhibition of Enteroviral 3C Proteases

Lead structure discovery mainly focuses on the identification of noncovalently binding ligands. Covalent linkage, however, is an essential binding mechanism for a multitude of successfully marketed drugs, although discovered by serendipity in most cases. We present a concept for the design of fragments covalently binding to proteases. Covalent linkage enables fragment binding unrelated to affinity to shallow protein binding sites and at the same time allows differentiated targeted hit verification and binding location verification through mass spectrometry. We describe a systematic and rational computational approach for the identification of covalently binding fragments from compound collections inhibiting enteroviral 3C protease, a target with high therapeutic potential. By implementing reactive groups potentially forming covalent bonds as a chemical feature in our 3D pharmacophore methodology, covalent binders were discovered by high-throughput virtual screening. We present careful experimental validation of the virtual hits using enzymatic assays and mass spectrometry unraveling a novel, previously unknown irreversible inhibition of the 3C protease by phenylthiomethyl ketone-based fragments. Subsequent synthetic optimization through fragment growing and reactivity analysis against catalytic and noncatalytic cysteines revealed specific irreversible 3C protease inhibition.

The role of enterovirus infections in type 1 diabetes in Tunisia

BACKGROUND

Enteroviral infections have long been suspected in having a role in β cell destruction and therefore leading to the onset of clinical type 1 diabetes (T1D). The frequency of enterovirus (EV)-related T1D in North Africa is still unknown. The aim of the present study was to investigate the relationship between infection with EV and T1D in Tunisia.

METHODS

A total of 95 T1D patients (41 children and 54 adults) and 141 healthy control subjects (57 children and 84 adults) were tested for the presence of EV-RNA by a highly sensitive nested reverse transcription-polymerase chain reaction (RT-PCR) method.

RESULTS

EV-RNA was detected more frequently in plasma from diabetic patients than in plasma of controls (31.6% vs. 7.8%, p<0.0001; OR=5.45; 95% CI 2.44-12.43). RT-PCR revealed positive in 53.7% of T1D children and 14.8% of T1D adults. There was a statistically significant difference between children and adults with T1D (p<0.0001). Positivity of EV-RNA according to the time after the occurrence of the disease did not show any significant difference (p=0.34). Anti-glutamic acid decarboxylase (GAD) antibodies were not associated with EV-RNA (p=0.65).

CONCLUSIONS

EV-RNA is associated with T1D mellitus in the Tunisian population especially in children. These results support the hypothesis that EV act as environmental risk factors for T1D.

Fresh Ideas, Foundational Experiments (FIFE): Immunology and Diabetes 2016 FIFE Symposium

The first Fresh Ideas, Foundational Experiments (FIFE): Immunology and Diabetes symposia workshop took place in 2016 and exemplified the active interest of a number of several investigators interested the global rise in the incidence of type 1 diabetes (T1D). This increase does not correlate with genetic drift and indicates that environmental exposures are playing an increasingly significant role. Despite major biomedical and technological advances in diagnosis and treatment, treatments are frequently insufficient as they do not inhibit the progression of the underlying autoimmune response and often fail to prevent life-threatening complications. T1D is the result of autoimmune destruction of the insulin-producing beta cells of the pancreas, and the precise, mechanistic contribution of the immune system to disease pathogenesis and progression remains to be fully characterized. Ultimately, the combinatorial effect of concurrent factors, including beta cell fragility, exogenous stressors, and genetic priming of the innate and adaptive immune system, work together to induce T1D autoimmunity. Thus, T1D is the result of immunological defects and environmental pathogens, requiring the sustained attention of collaborative research teams such as FIFE: I & D with varied perspectives, unified by the universally held goal of finding a sustainable, life-long cure. Herein, the authors provide perspective on various fields in T1D research highlighted by speakers participating in the inaugural FIFE symposium.

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

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

Autoimmunity and the microbiome: T-cell receptor mimicry of "self" and microbial antigens mediates self tolerance in holobionts: The concepts of "holoimmunity" (TcR-mediated tolerance for the holobiont) and "holoautoimmunity" (loss of tolerance for the holobiont) are introduced

I propose a T-cell receptor (TcR)-based mechanism by which immunity mediates both "genetic self" and "microbial self" thereby, connecting microbiome disease with autoimmunity. The hypothesis is based on simple principles. First, TcR are selected to avoid strong cross-reactivity with "self," resulting in selection for a TcR repertoire mimicking "genetic self." Second, evolution has selected for a "microbial self" that mimics "genetic self" so as to share tolerance. In consequence, our TcR repertoire also mimics microbiome antigenicity, providing a novel mechanism for modulating tolerance to it. Also, the microbiome mimics the TcR repertoire, acting as a secondary immune system. I call this TcR-microbiome mimicry "holoimmunity" to denote immune tolerance to the "holobiont self." Logically, microbiome-host mimicry means that autoimmunity directed at host antigens will also attack components of the microbiome, and conversely, an immunological attack on the microbiome may cross-react with host antigens producing "holoautoimmunity."

Regulation of effector and memory CD8(+) T cell function by inflammatory cytokines

Cells communicate with each other through the production and secretion of cytokines, which are integral to the host response to infection. Once recognized by specific cytokine receptors expressed on the cell surface, these exogenous signals direct the biological function of a cell in order to adapt to their microenvironment. CD8(+) T cells are critical immune cells that play an important role in the control and elimination of intracellular pathogens. Current findings have demonstrated that cytokines influence all aspects of the CD8(+) T cell response to infection or immunization. The cytokine milieu induced at the time of activation impacts the overall magnitude and function of the effector CD8(+) T cell response and the generation of functional memory CD8(+) T cells. This review will focus on the impact of inflammatory cytokines on different aspects of CD8(+) T cell biology.

The virus-induced HSPs regulate the apoptosis of operatus APCs that result in autoimmunity, not in homeostasis

The viruses stand salient as environmental factors that trigger autoimmunity. The virus realizes its effects through induction of heat-shock proteins (HSPs) as well as by the viral IE-axis-mediated conversion of organ epithelial cells into virgin de novo professional antigen-presenting cells (APCs). The HSP is the accomplished operator in homeostasis by the logic of it being the regulator of apoptosis. By virtue of its regulation of apoptosis, the HSP is also involved in autoimmunity: (1) adornment of viral IE-axis-generated virgin de novo professional APCs with HSP-induced co-stimulatory molecules which transform these otherwise epithelial cells to competent antigen presenters, the operatus APCs, liable to apoptosis that becomes the initiator of organ damages; (2) molecular mimicry mechanism: epitopes on the HSP may be mistaken for viral peptides and be presented by operatus APCs to autoreactive TCRs resulting in the apoptosis of the operatus APCs; (3) regulation of MHC class II DR-mediated apoptosis of operatus APCS which can result in organ-specific autoimmune syndromes. We should remember, however, that Nature's intended purpose for apoptosis of the professional APCs is benevolence: as a principal regulator of immune homeostasis. But the apoptosis of our postulated operatus APCs can result in autoimmunity. The transformation of virgin de novo professional APCs to operatus APCs mirrors the maturation of DCs through their acquisition of HSP-induced costimulatory molecules. What happens to mature DCs as antigen presenters that end in homeostasis is replicated by what happens to operatus APCs that ends instead in autoimmunity.

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

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

The virus-induced HSPs regulate the apoptosis of operatus APCs that results in autoimmunity, not in homeostasis

The viruses are salient in the roles of environmental factors that trigger autoimmunity. The virus realizes its effects by the power of its induction of heat shock proteins (HSPs) as well as by the viral IE-axis-mediated conversion of organ epithelial cells into virgin de novo professional antigen-presenting cells (APCs). The HSP is the accomplished operator in homeostasis by the logic of it being the regulator of apoptosis. That HSP which regulates and controls different points in the pathways of apoptosis is rationally propitious as both HSP and apoptosis are highly conserved in multicellular organisms. By virtue of its regulation of apoptosis, the HSP is also involved in human autoimmunity and this involvement is tripartite: (i) adornment of viral IE-axis-generated virgin de novo professional APCs with HSP-induced co-stimulatory molecules which transform these otherwise epithelial cells to achieve the status of fledged competent antigen-presenters, the operatus APCs, which are liable to apoptosis that becomes the initiator of organ damages that can culminate in the autoimmune syndrome(s); apoptosis is a routine fate that befalls all APCs following their antigen presentation; (ii) molecular mimicry mechanism: epitopes on the HSP may be mistaken for viral peptides and be presented by operatus APCs to autoreactive TCRs resulting in the apoptosis of the operatus APCs; and (iii) regulation of MHC class II-DR-mediated apoptosis of operatus APCs which can ultimately consequent in organ-specific autoimmune syndromes. We should remember, however, that Nature's intended purpose for the apoptosis of the professional APCs is benevolence: as a principal regulator of homeostasis. It is only from the apoptosis of our postulated operatus APCs that the apoptotic consequence can be deleterious, an autoimmune syndrome(s). The transformation of virgin de novo professional APCs to operatus APCs mirrors the maturation of DCs, through their acquisition of HSP-induced co-stimulatory molecules; and what happens to mature DCs as antigen-presenters that ends in homeostasis is replicated by what happens to operatus APCs that ends instead in autoimmune syndromes (Fig. 1).

The mosaic of environment involvement in autoimmunity: the abrogation of viral latency by stress, a non-infectious environmental agent, is an intrinsic prerequisite prelude before viruses can rank as infectious environmental agents that trigger autoimmune diseases

An autoimmune disease (AD), organ-specific or systemic, results from an aberrant response in which the protective immune system normally schooled to recognize and destroy invading infectious agents (viruses, etc.) instead fails to distinguish self-antigens and proceeds to attack and destroy the host's organs. There can be familial aggregation in which a single AD may occur in members of a family, or a single family may be afflicted with multiple ADs. Finally, sometimes multiple ADs co-occur in a single individual: the kaleidoscope of autoimmunity. Autoimmunity is a multifactorial process in which genetic, hormonal, immunological and environmental factors act in concert to materialize the mosaic of autoimmunity phenomenon. A genetically primed individual may yet not develop an AD: the contribution by an environmental factor (non-infectious or infectious) is essential for completion of the act. Of the non-infectious factors, stress plays a determinative step in autoimmunity in that it abrogates viral latency and thereby ordains the viruses to qualify as infectious environmental factors that trigger ADs. This is note-worthy as viruses rank first as the most important environmental triggers of ADs. Furthermore, all these viruses experience going through latency. Hence the hypothesis: "The abrogation of viral latency by stress, a non-infectious environmental agent, is an intrinsic prerequisite prelude before viruses can rank as infectious environmental agents that trigger autoimmune diseases". There is collaboration here between non-infectious- and infectious-agent to achieve the cause of autoimmunity. We say viral latency and stress have a covenant: continued perpetration of autoimmunity is dependent on the intervention by stress to reactivate latent infections.

Expression of innate immunity genes and damage of primary human pancreatic islets by epidemic strains of Echovirus: implication for post-virus islet autoimmunity

Three large-scale Echovirus (E) epidemics (E4,E16,E30), each differently associated to the acute development of diabetes related autoantibodies, have been documented in Cuba. The prevalence of islet cell autoantibodies was moderate during the E4 epidemic but high in the E16 and E30 epidemic. The aim of this study was to evaluate the effect of epidemic strains of echovirus on beta-cell lysis, beta-cell function and innate immunity gene expression in primary human pancreatic islets. Human islets from non-diabetic donors (n = 7) were infected with the virus strains E4, E16 and E30, all isolated from patients with aseptic meningitis who seroconverted to islet cell antibody positivity. Viral replication, degree of cytolysis, insulin release in response to high glucose as well as mRNA expression of innate immunity genes (IFN-b, RANTES, RIG-I, MDA5, TLR3 and OAS) were measured. The strains of E16 and E30 did replicate well in all islets examined, resulting in marked cytotoxic effects. E4 did not cause any effects on cell lysis, however it was able to replicate in 2 out of 7 islet donors. Beta-cell function was hampered in all infected islets (P<0.05); however the effect of E16 and E30 on insulin secretion appeared to be higher than the strain of E4. TLR3 and IFN-beta mRNA expression increased significantly following infection with E16 and E30 (P<0.033 and P<0.039 respectively). In contrast, the expression of none of the innate immunity genes studied was altered in E4-infected islets. These findings suggest that the extent of the epidemic-associated islet autoimmunity may depend on the ability of the viral strains to damage islet cells and induce pro-inflammatory innate immune responses within the infected islets.

Previous maternal infection protects offspring from enterovirus infection and prevents experimental diabetes development in mice

AIMS/HYPOTHESIS

Enterovirus (e.g. Coxsackie B virus serotypes [CVBs]) infections may be associated with development of type 1 diabetes. Studies conducted in several European countries have, however, shown an inverse correlation between the incidence of type 1 diabetes and the prevalence of enterovirus infections. These findings could in part be explained by an extension of the poliovirus hypothesis, suggesting that the absence of maternally transferred antibodies protecting offspring from early infection increases the risk for diabetes development. Experimental evidence supporting this hypothesis in type 1 diabetes is, however, lacking. As maternally transferred protection from infection is a crucial component of the extended poliovirus hypothesis, we here tested the hypothesis that previously infected females transfer protection against infection and diabetes to offspring.

METHODS

The induction of CVB-specific maternal antibodies and transfer of protection from virus infection, replication and development of virus-induced diabetes to offspring was assessed using NOD and Socs1-transgenic NOD mice.

RESULTS

Infected mice produced neutralising antibodies to CVB. Offspring from infected females were positive for neutralising antibodies and were strongly protected from both infection and experimental diabetes.

CONCLUSIONS/INTERPRETATION

Our study shows that maternally transferred antibodies protect offspring from enterovirus infection and virus-induced diabetes. This suggests that the absence of maternally provided protection increases the risk for severe outcomes after an enterovirus infection in offspring. Moreover, our findings may have implications for the design of prospective studies aimed at investigating the possible role of enterovirus infections in the aetiology of human type 1 diabetes.

In type 1 diabetes a subset of anti-coxsackievirus B4 antibodies recognize autoantigens and induce apoptosis of pancreatic beta cells

Type 1 diabetes is characterized by autoimmune destruction of pancreatic beta cells. The role played by autoantibodies directed against beta cells antigens in the pathogenesis of the disease is still unclear. Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet. To clarify these issues, we screened a random peptide library with sera obtained from 58 patients with recent onset type 1 diabetes, before insulin therapy. We identified an immunodominant peptide recognized by the majority of individual patients’sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis. Antibodies against the peptide affinity-purified from patients’ sera, recognized the viral protein and autoantigens; moreover, such antibodies induced apoptosis of the beta cells upon binding the L-type calcium channels expressed on the beta cell surface, suggesting a calcium dependent mechanism. Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.

Coxsackievirus B transmission and possible new roles for extracellular vesicles

Coxsackievirus B1, a member of the Picornaviridae family is a non-enveloped single-stranded RNA virus associated with human diseases including myocarditis and pancreatitis. Infection of the intestinal mucosa, lined by polarized epithelial cells, requires interaction of coxsackievirus with apically located DAF (decay-accelerating factor) before transport to the basolaterally located CAR (coxsackie and adenovirus receptor), where entry is mediated by endocytosis. As with many other non-enveloped viruses, coxsackievirus has to induce lysis of host cells in order to perpetuate infection. However, recent evidence indicates that virus spread to secondary sites is not only achieved by a lytic mechanism and a non-lytic cell–cell strategy has been suggested for coxsackievirus B3. A physical interaction between infected and non-infected cells has been shown to be an efficient mechanism for retroviral transmission and one type of extracellular vesicle, the exosome, has been implicated in HIV-1 transmission. HIV-1 also takes advantage of depolymerization of actin for spread between T-cells. Calpain-mediated depolymerization of the actin cytoskeleton, as a result of increases in intracellular calcium concentration during coxsackievirus infection, would result in a release of host cell-derived microvesicles. If so, we speculate that maybe such microvesicles, increasingly recognized as major vehicles mediating intercellular communication, could play a role in the intercellular transmission of non-enveloped viruses.

Alterations in glucose homeostasis in a murine model of Chagas disease

Chagas disease, caused by Trypanosoma cruzi, is an important cause of morbidity and mortality primarily resulting from cardiac dysfunction, although T. cruzi infection results in inflammation and cell destruction in many organs. We found that T. cruzi (Brazil strain) infection of mice results in pancreatic inflammation and parasitism within pancreatic β-cells with apparent sparing of α cells and leads to the disruption of pancreatic islet architecture, β-cell dysfunction, and surprisingly, hypoglycemia. Blood glucose and insulin levels were reduced in infected mice during acute infection and insulin levels remained low into the chronic phase. In response to the hypoglycemia, glucagon levels 30 days postinfection were elevated, indicating normal α-cell function. Administration of L-arginine and a β-adrenergic receptor agonist (CL316, 243, respectively) resulted in a diminished insulin response during the acute and chronic phases. Insulin granules were docked, but the lack of insulin secretion suggested an inability of granules to fuse at the plasma membrane of pancreatic β-cells. In the liver, there was a concomitant reduced expression of glucose-6-phosphatase mRNA and glucose production from pyruvate (pyruvate tolerance test), demonstrating defective hepatic gluconeogenesis as a cause for the T. cruzi-induced hypoglycemia, despite reduced insulin, but elevated glucagon levels. The data establishes a complex, multi-tissue relationship between T. cruzi infection, Chagas disease, and host glucose homeostasis.

Alternatively activated macrophages in types 1 and 2 diabetes

Macrophages are innate immune cells derived from monocytes, which, in turn, arise from myeloid precursor cells in the bone marrow. Macrophages have many important roles in the innate and adaptive immune response, as well as in tissue homeostasis. Two major populations have been defined: The classically activated macrophages that respond to intracellular pathogens by secreting proinflammatory cytokines and reactive oxygen species and alternatively activated macrophages which are induced during Th2 responses displaying anti-inflammatory activities. Both macrophage populations are central players in diabetes, the first one triggering inflammatory responses which initiates insulitis and pancreatic β cell death during type 1 diabetes, whereas the second population decreases hyperglycemia, insulitis, and inflammation in the pancreas, thereby negatively regulate type 1 diabetes. Obesity is an important factor in the development of type 2 diabetes; classically activated macrophages are a dominant cell population involved in the establishment of the inflammatory profile, insulin resistance, and activation of inflammatory signals during the development and progression of this disease. In contrast, alternatively activated macrophages regulate the release of proinflammatory cytokines, attenuating adipose tissue inflammation. Here, we review the advantages and disadvantages of these two macrophage populations with regard to their roles in types 1 and 2 diabetes.

Influenza A viruses grow in human pancreatic cells and cause pancreatitis and diabetes in an animal model

Influenza A viruses commonly cause pancreatitis in naturally and experimentally infected animals. In this study, we report the results of in vivo investigations carried out to establish whether influenza virus infection could cause metabolic disorders linked to pancreatic infection. In addition, in vitro tests in human pancreatic islets and in human pancreatic cell lines were performed to evaluate viral growth and cell damage. Infection of an avian model with two low-pathogenicity avian influenza isolates caused pancreatic damage resulting in hyperlipasemia in over 50% of subjects, which evolved into hyperglycemia and subsequently diabetes. Histopathology of the pancreas showed signs of an acute infection resulting in severe fibrosis and disruption of the structure of the organ. Influenza virus nucleoprotein was detected by immunohistochemistry (IHC) in the acinar tissue. Human seasonal H1N1 and H3N2 viruses and avian H7N1 and H7N3 influenza virus isolates were able to infect a selection of human pancreatic cell lines. Human viruses were also shown to be able to infect human pancreatic islets. In situ hybridization assays indicated that viral nucleoprotein could be detected in beta cells. The cytokine activation profile indicated a significant increase of MIG/CXCL9, IP-10/CXCL10, RANTES/CCL5, MIP1b/CCL4, Groa/CXCL1, interleukin 8 (IL-8)/CXCL8, tumor necrosis factor alpha (TNF-α), and IL-6. Our findings indicate that influenza virus infection may play a role as a causative agent of pancreatitis and diabetes in humans and other mammals.

The viral enterprises in autoimmunity: conversion of target cells into de novo APCs is the presage to autoimmunity

An autoimmune disease (AD) occurs in a situation where an individual's protective immune system attacks and destroys the individual's own tissues and organ(s), causing a recognizable syndrome(s). The viruses feature in the triggering of autoimmune diseases in genetically primed individuals through generating a viral group of regulatory immediate early proteins (IE). The IE indulges in promiscuous regulations of the viral replications as well as of host intracellular proteins. But there are consequences in the IE controlling host cell protein regulations, which we suggest as: the IE titration of the transactivator protein, autoimmune regulator (AIRE), which causes abolition of central tolerance; and the IE titration of the repressor protein, FOXP3, which results in the breach of peripheral tolerance. Titrations of AIRE and FOXP3 allow the escape of autoreactive T cells into the (peripheral) circulation where they can reach and zero in on self-tissues. The AD-predisposing MHC-II-DR-DQ haplotypes probably play a crucial role in the shaping of the T cell repertoire intrathymically for the survival of budding autoreactive T cell receptors (TCRs). Finally, we suggest there is IE titration of the repressors, the histone deacetylases (HDACs), in target organ cells which then consequentially express de novo MHC-II molecules and become de novo non-professional antigen-presenting cells (APCs), able to present viral peptides to cognate TCRs, thereby enrolling themselves for apoptotic death: a destiny of all APCs in immune responses, in general. Extensive apoptotic destruction of organ cells leads to an autoimmune syndrome(s).

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.

Effects of the microbial secondary metabolites pyrrolnitrin, phenazine and patulin on INS-1 rat pancreatic β-cells

The effects on pancreatic β-cell viability and function of three microbial secondary metabolites pyrrolnitrin, phenazine and patulin were investigated, using the rat clonal pancreatic β-cell line, INS-1. Cells were exposed to 10-fold serial dilutions (range 0-10 μg mL(-1)) of the purified compounds for 2, 24 and 72 h. After 2 h exposure, only patulin (10 μg mL(-1)) was cytotoxic. All compounds showed significant cytotoxicity after 24 h. None of the compounds altered insulin secretion with 2 and 20 mM glucose after 2 h. However, after 24 h treatment, phenazine and pyrrolnitrin (10 and 100 ng mL(-1)) potentiated insulin production and glucose-stimulated insulin secretion, whereas patulin had no effect. Exposure (24 h) to either phenazine (100 ng mL(-1)) or pyrrolnitrin (10 ng mL(-1)) caused similar increases in the Ca(2+) content of INS-1 cells. The outward membrane current was inhibited after 24 h exposure to either phenazine (100 ng mL(-1)) or pyrrolnitrin (10 or 100 ng mL(-1)). This study presents novel data suggesting that high concentrations of pyrrolnitrin and phenazine are cytotoxic to pancreatic β-cells and thus possibly diabetogenic, whereas at lower concentrations these agents are nontoxic and may be insulinotropic. The possible role of such agents in the development of cystic fibrosis-related diabetes is discussed.

dsRNA sensors and plasmacytoid dendritic cells in host defense and autoimmunity

The innate immune system detects viruses through molecular sensors that trigger the production of type I interferons (IFN-I) and inflammatory cytokines. As viruses vary tremendously in size, structure, genomic composition, and tissue tropism, multiple sensors are required to detect their presence in various cell types and tissues. In this review, we summarize current knowledge of the diversity, specificity, and signaling pathways downstream of viral sensors and ask whether two distinct sensors that recognize the same viral component are complementary, compensatory, or simply redundant. We also discuss why viral sensors are differentially distributed in distinct cell types and whether a particular cell type dominates the IFN-I response during viral infection. Finally, we review evidence suggesting that inappropriate signaling through viral sensors may induce autoimmunity. The picture emerging from these studies is that disparate viral sensors in different cell types form a dynamic and integrated molecular network that can be exploited for improving vaccination and therapeutic strategies for infectious and autoimmune diseases.

Identification and typing of human enterovirus: a genomic barcode approach

Identification and typing of human enterovirus (HEVs) are important to pathogen detection and therapy. Previous phylogeny-based typing methods are mainly based on multiple sequence alignments of specific genes in the HEVs, but the results are not stable with respect to different choices of genes. Here we report a novel method for identification and typing of HEVs based on information derived from their whole genomes. Specifically, we calculate the k-mer based barcode image for each genome, HEV or other human viruses, for a fixed k, 1<k<7, where a genome barcode is defined in terms of the k-mer frequency distribution across the whole genome for all combinations of k-mers. A phylogenetic tree is constructed using a barcode-based distance and a neighbor-joining method among a set of 443 representative non-HEV human viruses and 395 HEV sequences. The tree shows a clear separation of the HEV viruses from all the non-HEV viruses with 100% accuracy and a separation of the HEVs into four distinct clads with 93.4% consistency with a multiple sequence alignment-based phylogeny. Our detailed analyses of the HEVs having different typing results by the two methods indicate that our results are in better agreement with known information about the HEVs.

Differentiation of autoimmune pancreatitis from pancreas cancer: utility of anti-amylase and anti-carbonic anhydrase II autoantibodies

Purpose

To investigate the utility of different combinations of serum anti-carbonic anhydrase II antibodies (CA II Abs), anti-α amylase antibodies (AMY-α Abs) and IgG4 levels for the diagnosis of autoimmune pancreatitis (AIP).

Methods

We recruited 93 patients with clinical suspicion for AIP and 94 patients as control groups between June 2003 and October 2009. Serum antibodies were measured using homemade enzyme linked immunosorbent assay and IgG4 levels were determined by nephelometry.

Results

Both CA-II Abs and AMY-α Abs had the highest sensitivity (83%) although AMY-α Abs (89%) were more specific than CA-II Abs (75%). The presence of increased IgG4 levels was the most specific serological marker (94%), but it had the lowest sensitivity (58%). The combination of the three serological markers altogether had the highest specificity (99%) and positive predictive value (PPV) (86%), but they had a rather low sensitivity (50%). When we combined CA-II Abs and AMY-α Abs without IgG4 levels, we got the highest sensitivity (75%) and negative predictive value (98%) but the specificity and the PPV decreased to 93 and 50%, respectively. Importantly, AMY-α Abs were not detected in pancreas cancer.

Conclusions

The presence of serum CA-II and AMY-α Abs with increased IgG4 is useful in the differential diagnosis of AIP from pancreatic cancer.

High prevalence of vitamin D deficiency in school-age children in Tehran, 2008: a red alert

OBJECTIVE

To assess the vitamin D status of 9-12-year-old primary-school children in Tehran during autumn and winter 2007-2008.

DESIGN

A descriptive cross-sectional study.

SETTING

Primary schools of Tehran city, Iran.

SUBJECTS

A total of 1111 children aged 9-12 years (573 boys and 538 girls) from sixty primary schools were enrolled in the study. Weight, height, BMI and serum levels of Ca, P, Mg, 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone (iPTH), osteocalcin and bone-specific alkaline phosphatase of all the participants were assessed. Dietary Ca intake was also evaluated using a quantitative FFQ for a subsample of the study population (n 503). Vitamin D sufficiency was defined on the basis of serum levels of 25(OH)D as either ≥37 nmol/l (criterion 1) or ≥50 nmol/l (criterion 2).

RESULTS

Daily intake of Ca did not differ significantly between boys and girls (929·6 (sd 436·7) mg and 909·5 (sd 465·5) mg, respectively). However, on the basis of the first criterion, approximately 86 % of the children had vitamin D deficiency, with 38·3 % being severely deficient (25(OH)D < 12·5 nmol/l). According to the second criterion, prevalence of vitamin D deficiency rose to 91·7 %. Prevalence of vitamin D deficiency was higher in girls than in boys by either criterion. Serum levels of 25(OH)D inversely correlated with iPTH (r = -0·154, P < 0·001) and BMI (r = -0·092, P = 0·002) but directly correlated with duration of sun exposure (r = 0·115, P < 0·001).

CONCLUSIONS

The high prevalence of vitamin D deficiency among schoolchildren (especially among girls) warrants immediate interventions for proper nutritional support.

Enterovirus infection and progression from islet autoimmunity to type 1 diabetes: the Diabetes and Autoimmunity Study in the Young (DAISY)

OBJECTIVE

To investigate whether enterovirus infections predict progression to type 1 diabetes in genetically predisposed children repeatedly positive for islet autoantibodies.

RESEARCH DESIGN AND METHODS

Since 1993, the Diabetes and Autoimmunity Study in the Young (DAISY) has followed 2,365 genetically predisposed children for islet autoimmunity and type 1 diabetes. Venous blood and rectal swabs were collected every 3-6 months after seroconversion for islet autoantibodies (against GAD, insulin, or insulinoma-associated antigen-2 [IA-2]) until diagnosis of diabetes. Enteroviral RNA in serum or rectal swabs was detected using reverse transcriptase PCR with primers specific for the conserved 5' noncoding region, detecting essentially all enterovirus serotypes.

RESULTS

Of 140 children who seroconverted to repeated positivity for islet autoantibodies at a median age of 4.0 years, 50 progressed to type 1 diabetes during a median follow-up of 4.2 years. The risk of progression to clinical type 1 diabetes in the sample interval following detection of enteroviral RNA in serum (three diabetes cases diagnosed among 17 intervals) was significantly increased compared with that in intervals following a negative serum enteroviral RNA test (33 cases diagnosed among 1,064 intervals; hazard ratio 7.02 [95% CI 1.95-25.3] after adjusting for number of autoantibodies). Results remained significant after adjustment for ZnT8-autoantibodies and after restriction to various subgroups. Enteroviral RNA in rectal swabs was not predictive of progression to type 1 diabetes. No evidence for viral persistence was found.

CONCLUSIONS

This novel observation suggests that progression from islet autoimmunity to type 1 diabetes may increase after an enterovirus infection characterized by the presence of viral RNA in blood.

Virus infections and type 1 diabetes risk

Common intestinal infections caused by human enteroviruses (HEVs) are considered major environmental factors predisposing to type 1 diabetes (T1D). In spite of the active research of the field, the HEV-induced pathogenetic processes are poorly understood. Recently, after the first documented report on HEV infections in the pancreatic islets of deceased T1D patients, several groups became interested in the issue and studied valuable human material, the autopsy pancreases of diabetic and/or autoantibody-positive patients for HEV infections. In this review, the data on HEV infections in human pancreatic islets are discussed with special reference to the methods used. Likewise, mechanisms that could increase viral access to the pancreas are reviewed and discussed.

Loss-of-function mutations E6 27X and I923V of IFIH1 are associated with lower poly(I:C)-induced interferon-β production in peripheral blood mononuclear cells of type 1 diabetes patients

Melanoma differentiation-associated 5 (MDA5), a product of the IFIH1 gene, is responsible for sensing double-stranded viral double-stranded RNA (RNA). In this study, we showed a significant association of two rare IFIH1 variants, rs35744605 (E627X) and rs35667974 (I923V), with decreased risk of type 1 diabetes (T1D) in a Russian population (for the allele X627, odds ratio [OR] = 0.39, 95% confidence interval [95% CI] = 0.22-0.69, p = 0.0015; for the allele V923, OR = 0.45, 95% CI, 0.30-0.66, p = 5.4 × 10(-5)). We detected a 3.5-fold greater frequency of enteroviral RNA in T1D subjects compared with controls (p <1.0 × 10(-8)), and 2.1-fold more frequent presence of viral RNA in T1D patients with a recent-onset diabetes (duration ≤1 year) compared with those with a longer disease (p <1.0 × 10(-8)). The carriage of the predisposing IFIH1 EI/EI haplogenotype was significantly associated with a 1.5- to 1.7-fold increase in the poly(I:C)-stimulated secretion of IFN-β in PMBCs compared with the other IFIH1 variants. The upregulated MDA5-dependent production of inflammatory cytokines could enhance the autoimmune destruction of β-cells mediated by self-reactive T-cells.

Cross-priming in health and disease

Cross-priming is an important mechanism to activate cytotoxic T lymphocytes (CTLs) for immune defence against viruses and tumours. Although it was discovered more than 25 years ago, we have only recently gained insight into the underlying cellular and molecular mechanisms, and we are just beginning to understand its physiological importance in health and disease. Here we summarize current concepts on the cross-talk between the immune cells involved in CTL cross-priming and on its role in antimicrobial and antitumour defence, as well as in immune-mediated diseases.

Pathogenesis of type 1 diabetes mellitus: interplay between enterovirus and host

Enteroviruses are believed to contribute to the pathogenesis of type 1 diabetes mellitus (T1DM). In this Review, the interplay between infection with enteroviruses, the immune system and host genes is discussed. Data from retrospective and prospective epidemiological studies strongly suggest the involvement of enteroviruses, such as coxsackievirus B, in the development of T1DM. Enteroviral RNA and/or proteins can be detected in tissues of patients with T1DM. Isolation of coxsackievirus B4 from the pancreas of patients with T1DM or the presence of enteroviral components in their islets strengthens the hypothesis of a relationship between the virus and the disease. Enteroviruses can play a part in the early phase of T1DM through the infection of beta cells and the activation of innate immunity and inflammation. In contrast with its antiviral role, virus-induced interferon alpha can be deleterious, acting as an initiator of the autoimmunity directed against beta cells. Enteroviruses, through persistent and/or successive infections, can interact with the adaptive immune system. Host genes, such as IFIH1, that influence susceptibility to T1DM are associated with antiviral activities. An increased activity of the IFIH1 protein may promote the development of T1DM. An improved knowledge of the pathogenic mechanisms of enterovirus infections should help to uncover preventive strategies for T1DM.

Enteroviruses in the pathogenesis of type 1 diabetes

The question if enteroviruses could cause beta-cell damage and type 1 diabetes has become more and more relevant when recent studies have provided new evidence supporting this scenario. One important observation is the recent discovery of IFIH1 as a risk gene for type 1 diabetes. This gene is an innate immune system receptor for enteroviruses offering one possible mechanism for the diabetogenic effect of enteroviruses. This is further emphasized by the observations suggesting that the innate immune system is activated in the pancreatic islets of type 1 diabetic patients and that the innate immune system is important for the defense against the virus and for the regulation of adaptive immune system. Important progress has also been gained in studies analyzing pancreas tissue for possible presence of enteroviruses. Several studies have found enteroviruses in the pancreatic islets of type 1 diabetic patients using various methods. The virus seems to be located in the islets while exocrine pancreas is mostly uninfected. One recent study found the virus in the intestinal mucosa in the majority of diabetic patients. Enteroviruses can also infect cultured human pancreatic islets causing either rapid cell destruction or a persistent-like noncytolytic infection. Combined with all previous, epidemiological findings indicating the risk effect of enteroviruses in cross-sectional and prospective studies, these observations fit to a scenario where certain diabetogenic enterovirus variants establish persistent infection in gut mucosa and in the pancreatic islets. This in turn could lead to a local inflammation and the breakdown of tolerance in genetically susceptible individuals. This is also supported by mouse experiments showing that enteroviruses can establish prolonged infection in the pancreas and intestine, and some virus strains cause beta-cell damage and diabetes. In conclusion, recent studies have strengthened the hypothesis that enteroviruses play a role in the pathogenesis of type 1 diabetes. These findings open also new opportunities to explore the underlying mechanism and get closer to causal relationship.

Gut barrier disruption by an enteric bacterial pathogen accelerates insulitis in NOD mice

AIMS/HYPOTHESIS

Increased exposure to enteric microbes as a result of intestinal barrier disruption is thought to contribute to the development of several intestinal inflammatory diseases; however, it less clear whether such exposure modulates the development of extra-intestinal inflammatory and autoimmune diseases. The goal of this study was to examine the potential role of pathogenic enteric microbes and intestinal barrier dysfunction in the pathogenesis of type 1 diabetes.

METHODS

Using NOD mice, we assessed: (1) intrinsic barrier function in mice at different ages by measuring serum levels of FITC-labelled dextran; and (2) the impact on insulitis development of infection by strains of an enteric bacterial pathogen (Citrobacter rodentium) either capable (wild-type) or incapable (lacking Escherichia coli secreted protein F virulence factor owing to deletion of the gene [DeltaespF]) of causing intestinal epithelial barrier disruption.

RESULTS

Here we demonstrate that prediabetic (12-week-old) NOD mice display increased intestinal permeability compared with non-obese diabetes-resistant and C57BL/6 mice. We also found that young (4-week-old) NOD mice infected with wild-type C. rodentium exhibited accelerated development of insulitis in concert with infection-induced barrier disruption. In contrast, insulitis development was not altered in NOD mice infected with the non-barrier-disrupting DeltaespF strain. Moreover, C. rodentium-infected NOD mice demonstrated increased activation and proliferation of pancreatic-draining lymph node T cells, including diabetogenic CD8(+) T cells, compared with uninfected NOD mice.

CONCLUSIONS/INTERPRETATION

This is the first demonstration that a loss of intestinal barrier integrity caused by an enteric bacterial pathogen results in the activation of diabetogenic CD8(+) T cells and modulates insulitis.

Melanoma differentiation-associated protein-5 (MDA-5) limits early viral replication but is not essential for the induction of type 1 interferons after Coxsackievirus infection

Coxsackievirus infections are associated with severe diseases such as myocarditis, meningitis and pancreatitis. To study the contribution of the intracellular viral sensor melanoma differentiation-associated protein-5 (MDA-5) in the host immune response to Coxsackievirus B3 (CVB3) we infected C57BL/6 and 129/SvJ mice lacking mda-5. Mice deficient in MDA-5 showed a dramatically increased susceptibility to CVB3 infection. The loss of MDA-5 allowed the virus to replicate faster, resulting in increased liver and pancreas damage and heightened mortality. MDA-5 was not absolutely required for the induction of type 1 interferons (IFNs), but essential for the production of maximal levels of systemic IFN-alpha early after infection. Taken together, our findings indicate that MDA-5 plays an important role in the host immune response to CVB3 by preventing early virus replication and limiting tissue pathology.