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

Viruses and cytotoxic T lymphocytes in type 1 diabetes

Histopathological studies on pancreas tissues from individuals with recent-onset type 1 diabetes (T1D) consistently find that CD8 T cells substantially contribute to the formation of islet lesions. CD8 T cells reactive against islet-associated antigens can also be found in blood samples from T1D patients. Mechanistic studies on the pathogenic role of this T cell subset have mostly focused on two animal models, i.e., the non-obese diabetic mouse and the virally induced rat insulin promoter-lymphocytic choriomeningitis virus model. Data were obtained in support of a role for viral infection in expanding a population of diabetogenic cytotoxic T lymphocytes. In view of the theorized association of viral infection with initiation of islet autoimmunity and progression to clinically overt disease, CD8 T cells thus represent an attractive target for immunotherapy. We will review here arguments in favor of a pivotal role for CD8 T cells in driving T1D development and speculate on etiologic agents that may provoke their aberrant activation.

Epitope spreading is rarely found in pemphigus vulgaris by large-scale longitudinal study using desmoglein 2-based swapped molecules

Epitope spreading is involved in inducing and maintaining self-reactivity. Epitope spreading in pemphigus vulgaris (PV), caused by IgG autoantibodies to desmoglein 3 (Dsg3) and Dsg1, was previously analyzed using Dsg3/Dsg1 extracellular domain-swapped molecules. However, precise identification of the responsible epitopes in each molecule by using only this method was problematic. In this study, we studied epitope spreading in PV by a novel immunoprecipitation-immunoblot method using Dsg3 (or Dsg1)/Dsg2 domain-swapped molecules, which overcomes the problems associated with the previous approaches. We analyzed the antigenic epitopes recognized by 212 sera collected from 53 PV patients at multiple disease stages. The major epitopes were present at the N-terminal region of Dsgs and were unchanged over the course of the disease in both anti-Dsg3 mucosal dominant-type PV and anti-Dsg3/Dsg1 mucocutaneous-type PV. These N-terminal epitopes were calcium dependent. Circulating antibodies in paraneoplastic pemphigus and pemphigus herpetiformis had unique epitope distributions, although the Dsg N-termini still contained the major epitopes. These results suggest that, after onset, intramolecular and intermolecular epitope spreading among extracellular domains on Dsg3 and Dsg1 is rare in PV and has no correlation with disease course.

Oral ingestion of Capsaicin, the pungent component of chili pepper, enhances a discreet population of macrophages and confers protection from autoimmune diabetes

Vanilloid receptor 1 (VR1) is expressed on immune cells as well as on sensory neurons. Here we report that VR1 can regulate immunological events in the gut in response to its ligand Capsaicin (CP), a nutritional factor, the pungent component of chili peppers. Oral administration of CP attenuates the proliferation and activation of autoreactive T cells in pancreatic lymph nodes (PLNs) but not other lymph nodes, and protects mice from development of type 1 diabetes (T1D). This is a general phenomenon and not restricted to one particular strain of mice. Engagement of VR1 enhances a discreet population of CD11b(+)/F4/80(+) macrophages in PLN, which express anti-inflammatory factors interleukin (IL)-10 and PD-L1. This population is essential for CP-mediated attenuation of T-cell proliferation in an IL-10-dependent manner. Lack of VR1 expression fails to inhibit proliferation of autoreactive T cells, which is partially reversed in (VR1(+/+) → VR1(-/-)) bone marrow chimeric mice, implying the role of VR1 in crosstalk between neuronal and immunological responses in vivo. These findings imply that endogenous ligands of VR1 can have profound effect on gut-mediated immune tolerance and autoimmunity by influencing the nutrient-immune interactions.

High intrafamilial variability in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy: a case study

INTRODUCTION

Autoimmune polyendocrinopathy- candidiasis-ectodermal-dystrophy syndrome (APECED) is a monogenic disease whose phenotype may reveal wide heterogeneity. The reasons of this variability still remain obscure.

PATIENTS AND METHODS

Two APECED siblings with identical genotype and extremely different phenotype were compared with regard to exposure to infectious triggers, autoantibodies' profile, mechanisms of peripheral tolerance, and human leukocyte antigen (HLA) haplotype. The following infectious markers were evaluated: rubella, Epstein Barr virus, cytomegalovirus, toxoplasma, varicella zoster virus, parvovirus B19, herpes simplex virus, and parainfluenza virus. APECED-related autoantibodies were detected by indirect immunofluorescence or complement fixation or enzyme- linked immunosorbent assay or radioimmunoassay. Resistance to Fas-induced apoptosis was evaluated on peripheral blood mononuclear cells (PBMC) activated with phytohemoagglutinin, the number of TCD4+CD25+ regulatory cells (Treg) was evaluated through flow-cytometry and natural killer (NK) activity through Wallac method. Perforin (PRF1) was amplified by PCR and sequenced.

RESULTS

No difference was observed between the siblings in common infectious triggers, extent of Fas-induced apoptosis, NK-cell activity and PRF1 sequence, the number of Tregs and HLA haplotypes.

CONCLUSION

Although APECED is a monogenic disease, its expressivity may be extremely different even in the same family. This variability cannot be explained by common triggering infectious agents or functional alterations of mechanisms governing peripheral tolerance.

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.

Harnessing memory adaptive regulatory T cells to control autoimmunity in type 1 diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing β-cells in the pancreatic islets. There is an immediate need to restore both β-cell function and immune tolerance to control disease progression and ultimately cure T1D. Currently, there is no effective treatment strategy to restore glucose regulation in patients with T1D. FoxP3-expressing CD4(+) regulatory T cells (Tregs) are potential candidates to control autoimmunity because they play a central role in maintaining self-tolerance. However, deficiencies in either naturally occurring Tregs (nTregs) themselves and/or their ability to control pathogenic effector T cells have been associated with T1D. Here, we hypothesize that nTregs can be replaced by FoxP3(+) adaptive Tregs (aTregs), which are uniquely equipped to combat autoreactivity in T1D. Unlike nTregs, aTregs are stable and provide long-lived protection. In this review, we summarize the current understanding of aTregs and their potential for use as an immunological intervention to treat T1D.

Characterization of infections of human leukocytes by non-polio enteroviruses

To elucidate the detailed susceptibilities of leukocytes to clinically important non-polio enteroviruses (EVs), primary monocytes and various human leukocyte cell lines were infected with coxsackievirus A24 (CVA24), coxsackievirus B3 (CVB3), and enterovirus 70 (EV70). The permissiveness was then assessed by determining virus replication and resultant cytopathic effects. Different EVs varied markedly in their ability to infect leukocyte cell lines. CVB3 replicated effectively in leukocytes of B-cell, T-cell, and monocyte origin, CVA24 in leukocytes of B-cell and monocyte origin, and EV70 in leukocytes of monocyte origin. Primary monocytes, as well as monocyte-derived U-937 cells, were permissive to all three EVs. We observed a positive correlation between cytotoxicity and active virus replication, except in CVB3-infected monocytes. U-937 cells efficiently generated CVB3 progeny virus without severe cellular damage, including cell death. Moreover, infectivity on leukocytes was not absolutely associated with the availability of viral receptors. These findings suggest that the susceptibility of human leukocytes to non-polio EVs may be responsible for virus transport during the viremic phase, particularly to secondary target organs, and that active replication of CVB3 in all human leukocyte lineages leads to greater dissemination, in agreement with the ability of CVB to cause systemic diseases.

Exposure to the viral by-product dsRNA or Coxsackievirus B5 triggers pancreatic beta cell apoptosis via a Bim / Mcl-1 imbalance

The rise in type 1 diabetes (T1D) incidence in recent decades is probably related to modifications in environmental factors. Viruses are among the putative environmental triggers of T1D. The mechanisms regulating beta cell responses to viruses, however, remain to be defined. We have presently clarified the signaling pathways leading to beta cell apoptosis following exposure to the viral mimetic double-stranded RNA (dsRNA) and a diabetogenic enterovirus (Coxsackievirus B5). Internal dsRNA induces cell death via the intrinsic mitochondrial pathway. In this process, activation of the dsRNA-dependent protein kinase (PKR) promotes eIF2α phosphorylation and protein synthesis inhibition, leading to downregulation of the antiapoptotic Bcl-2 protein myeloid cell leukemia sequence 1 (Mcl-1). Mcl-1 decrease results in the release of the BH3-only protein Bim, which activates the mitochondrial pathway of apoptosis. Indeed, Bim knockdown prevented both dsRNA- and Coxsackievirus B5-induced beta cell death, and counteracted the proapoptotic effects of Mcl-1 silencing. These observations indicate that the balance between Mcl-1 and Bim is a key factor regulating beta cell survival during diabetogenic viral infections.

Group B coxsackieviruses and autoimmunity: focus on Type 1 diabetes

Group B coxsackieviruses (CVB) and/or their components have been found in the blood and pancreas of patients with Type 1 diabetes (T1D). CVB infections lead to the activation of the innate and adaptive immune systems, which can result in the induction or aggravation of autoimmune processes. Persistent and/or repeated infections of pancreas islet β cells with CVB and the resulting production of IFN-α and inflammatory mediators, combined with a predisposed genetic background, may induce bystander activation of autoimmune effector T cells and an autoreactive response to islet self-antigens through molecular mimicry. Moreover, the antibody-dependent enhancement of CVB infection of monocytes, as well as infection of the thymus can intervene in the pathogenesis of T1D. In contrast with the deleterious effect of CVB, it has been shown that these viruses can protect against the development of T1D under certain experimental conditions. The role of CVB in autoimmunity is complex, and therefore a better understanding of the inducer versus protective effects of these viruses in T1D will help to design new strategies to treat and prevent the disease.

Chlamydia pneumoniae heat shock protein 60 is associated with apoptotic signaling pathway in human atheromatous plaques of coronary artery disease patients

BACKGROUND

Chlamydia pneumoniae heat shock protein (HSP) 60 is known to contribute to the activation of inflammation. In addition, there are contradictory reports on C. pneumoniae and their role in activation of pathways (apoptotic/antiapoptotic/necrosis) in coronary artery disease (CAD). Hence, more studies are required to know the actual role of C. pneumoniae in activation of apoptotic/antiapoptotic/necrosis pathways.

METHODS AND RESULTS

In this study, two sets of patient groups (cHSP60 positive and cHSP60 negative) were included and gene expression was studied by cDNA micro array and real time polymerase chain reaction arrays. Expression of Caspase-3, 8, 9, c-FLIP, PPAR-γ, PGC-1α, and Gsk-3b were also evaluated at protein level by immunoblotting. In cHSP60 positive CAD patients significantly higher (p<0.001) mRNA expression was found for CCL4, CXCL4, CXCL9, IL-8, CD40LG, CD8, TGFβ1, TGFβ2, APOE, EGR1, CTGF, APOB, LDLR, LPA, and LPL, whereas significantly lower (p<0.001) mRNA expression was detected for CD4, IL1F10, IFNA2, and IL-10 as compared to cHSP60 negative CAD patients. Additionally, at protein level expression of Caspase-3 (p=0.027), 8 (p=0.028), and 9 (p=0.037) were higher and c-FLIP (p=0.028) and PPAR-γ (p=0.95) expression were comparable in cHSP60 positive CAD patients compared to cHSP60 negative CAD patients.

CONCLUSION

Genes/proteins of pre-apoptotic caspase dependent/independent pathways, chemokines, and inflammatory cytokines receptors were significantly up-regulated in human atheromatous plaques of cHSP60 positive CAD patients suggesting an association of cHSP60 with CAD.

Recognition and killing of human and murine pancreatic beta cells by the NK receptor NKp46

Type 1 diabetes is an incurable disease that is currently treated by insulin injections or in rare cases by islet transplantation. We have recently shown that NKp46, a major killer receptor expressed by NK cells, recognizes an unknown ligand expressed by β cells and that in the absence of NKp46, or when its activity is blocked, diabetes development is inhibited. In this study, we investigate whether NKp46 is involved in the killing of human β cells that are intended to be used for transplantation, and we also thoroughly characterize the interaction between NKp46 and its human and mouse β cell ligands. We show that human β cells express an unknown ligand for NKp46 and are killed in an NKp46-dependent manner. We further demonstrate that the expression of the NKp46 ligand is detected on human β cells already at the embryonic stage and that it appears on murine β cells only following birth. Because the NKp46 ligand is detected on healthy β cells, we wondered why type 1 diabetes does not develop in all individuals and show that NK cells are absent from the vicinity of islets of healthy mice and are detected in situ in proximity with β cells in NOD mice. We also investigate the molecular mechanisms controlling NKp46 interactions with its β cell ligand and demonstrate that the recognition is confined to the membrane proximal domain and stalk region of NKp46 and that two glycosylated residues of NKp46, Thr(125) and Asn(216), are critical for this recognition.

TLR7/9 versus TLR3/MDA5 signaling during virus infections and diabetes

IFN-I are pleiotropic cytokines that impact innate and adaptive immune responses. In this article, we discuss TLR7/9 versus TLR3/MDA5 signaling in antiviral responses and diabetes. pDCs are thought to have a critical role in antiviral defense because of their ability to rapidly secrete large amounts of IFN-I through TLR7/9 signaling. A recent study demonstrates that although pDCs are a source of IFN-I in vivo, their overall contribution to viral containment is limited and time-dependent, such that additional cellular sources of IFN-I are required to fully control viral infections. dsRNA sensors, such as TLR3 and MDA5, provide another important trigger for antiviral IFN-I responses, which can be exploited to enhance immune responses to vaccines. In the absence of infection, IFN-I production by pDCs or from signaling through dsRNA sensors has been implicated in the pathogenesis of autoimmune diseases such as diabetes. However, recent data demonstrate that IFN-I production via TLR3 and MDA5 is critical to counter diabetes caused by a virus with preferential tropism for pancreatic β-cells. This highlights the complexity of the host antiviral response and how multiple cellular and molecular components balance protective versus pathological responses.

RNA sensor-induced type I IFN prevents diabetes caused by a β cell-tropic virus in mice

Viral infections have been linked to the onset of type I diabetes (T1D), with viruses postulated to induce disease directly by causing β cell injury and subsequent release of autoantigens and indirectly via the host type I interferon (IFN-I) response triggered by the virus. Consistent with this, resistance to T1D is associated with polymorphisms that impair the function of melanoma differentiation associated gene-5 (MDA5), a sensor of viral RNA that elicits IFN-I responses. In animal models, triggering of another viral sensor, TLR3, has been implicated in diabetes. Here, we found that MDA5 and TLR3 are both required to prevent diabetes in mice infected with encephalomyocarditis virus strain D (EMCV-D), which has tropism for the insulin-producing β cells of the pancreas. Infection of Tlr3-/- mice caused diabetes due to impaired IFN-I responses and virus-induced β cell damage rather than T cell-mediated autoimmunity. Mice lacking just 1 copy of Mda5 developed transient hyperglycemia when infected with EMCV-D, whereas homozygous Mda5-/- mice developed severe cardiac pathology. TLR3 and MDA5 controlled EMCV-D infection and diabetes by acting in hematopoietic and stromal cells, respectively, inducing IFN-I responses at kinetically distinct time points. We therefore conclude that optimal functioning of viral sensors and prompt IFN-I responses are required to prevent diabetes when caused by a virus that infects and damages the β cells of the pancreas.

Fragments of genomic DNA released by injured cells activate innate immunity and suppress endocrine function in the thyroid

Activation of innate and acquired immune responses, which can be induced by infection, inflammation, or tissue injury, may impact the development of autoimmunity. Although stimulation of cells by double-stranded DNA (dsDNA) has been shown to activate immune responses, the role of self-genomic DNA fragments released in the context of sterile cellular injury is not well understood. Using cultured thyroid cells, we show that cell injury prompts the release of genomic DNA into the cytosol, which is associated with the production of type I interferons, inflammatory cytokines, and chemokines. Molecules necessary for antigen processing and presentation to lymphocytes are also induced in thyroid cells by injury. dsDNA strongly suppressed the expression of sodium/iodide symporter and radioiodine uptake. To identify molecules responsible for sensing cytosolic dsDNA, we directly identified the cellular proteins that bound a dsDNA Sepharose column by mass spectrometry. Our analysis identified histone H2B, which was previously demonstrated to be an essential factor that mediates the activation of innate immunity induced by dsDNA. Knockdown of histone H2B using specific small interfering RNA abolished cell injury-induced innate immune activation and increased sodium/iodide symporter expression. These results indicate that genomic DNA fragments released by cell injury are recognized by extrachromosomal histone H2B, which results in the activation of genes involved in both innate and acquired immune responses in thyroid cells and suppression of thyroid function. These results suggest that sterile thyroid injury, in the absence of infection, may be sufficient to trigger autoimmune reaction and to induce thyroid dysfunction.

Viral infection prevents diabetes by inducing regulatory T cells through NKT cell-plasmacytoid dendritic cell interplay

Type 1 diabetes (T1D) is an autoimmune disease resulting from T cell-mediated destruction of insulin-producing β cells, and viral infections can prevent the onset of disease. Invariant natural killer T cells (iNKT cells) exert a regulatory role in T1D by inhibiting autoimmune T cell responses. As iNKT cell-plasmacytoid dendritic cell (pDC) cooperation controls viral replication in the pancreatic islets, we investigated whether this cellular cross talk could interfere with T1D development during viral infection. Using both virus-induced and spontaneous mouse models of T1D, we show that upon viral infection, iNKT cells induce TGF-β-producing pDCs in the pancreatic lymph nodes (LNs). These tolerogenic pDCs convert naive anti-islet T cells into Foxp3(+) CD4(+) regulatory T cells (T reg cells) in pancreatic LNs. T reg cells are then recruited into the pancreatic islets where they produce TGF-β, which dampens the activity of viral- and islet-specific CD8(+) T cells, thereby preventing T1D development in both T1D models. These findings reveal a crucial cooperation between iNKT cells, pDCs, and T reg cells for prevention of T1D by viral infection.

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

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

Immunological, paracrine and endocrine aspects of testicular immune privilege

Protection of the spermatogenic cells from the host immune response is fundamental to male fertility. Significantly, this protection extends to the tolerance of foreign tissue grafts placed within the testicular environment, a phenomenon that is called 'immune privilege'. This privilege of the testis appears to involve several levels of immune control, encompassing the normal mechanisms of immune tolerance, antigen sequestration behind the blood-testis barrier, reduced immune activation, localised immunosuppression and antigen-specific immunoregulation. Central to these regulatory processes are the somatic cells of the testis, particularly the Sertoli cells, and testicular secretions, including androgens, cytokines, peptides and bioactive lipids. Failure of these protective mechanisms, which may be precipitated by trauma, inflammation or infection, or as the consequence of genetic factors, can lead to androgen deficiency, infertility and autoimmunity.

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

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

Do viral infections protect from or enhance type 1 diabetes and how can we tell the difference?

Virus infections have been implicated in both initiation of and protection from autoimmune diseases, such as type 1 diabetes (T1D). In this review we intend to reflect on recent evidence how viruses might on the one hand be involved in the pathogenesis of T1D and on the other hand induce a state of protection from autoimmune-mediated damage. It is important to acknowledge that human individuals encounter more than just one virus infection in their lifetime. Therefore, it is important to integrate more than just one possible environmental triggering factor for autoimmune diseases to occur.

Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies

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

Enteroviruses and type 1 diabetes: towards a better understanding of the relationship

Environmental factors, especially viruses, are involved in the initiation or the acceleration of type 1 diabetes (T1D) pathogenesis. Epidemiological data strongly suggest that enteroviruses, such as coxsackievirus B4 (CV-B4), can be associated with T1D. It has been demonstrated that enterovirus infections were significantly more prevalent in at risk individuals, such as siblings of diabetic patients, when they developed anti-beta-cell autoantibodies or T1D, and in recently diagnosed diabetic patients, compared with control subjects. The isolation of CV-B4 from the pancreas of diabetic patients strengthened the hypothesis of a relationship between the virus and the disease. Studies performed in vitro and in vivo in animal models helped to discover mechanisms of the infection of pancreas and other tissues, potentially able to play a role in the pathogenesis of T1D. Interestingly, it cannot be excluded that enteroviruses behave as half-devil half-angel since experimental studies suggest that, in certain conditions, these agents would be able to protect individuals against the disease. All of the plausible mechanisms by which enterovirus may be related to T1D will be reviewed here.

Pathogenic T cells have a paradoxical protective effect in murine autoimmune diabetes by boosting Tregs

CD4+CD25+Foxp3+ Tregs play a major role in prevention of autoimmune diseases. The suppressive effect of Tregs on effector T cells (Teffs), the cells that can mediate autoimmunity, has been extensively studied. However, the in vivo impact of Teff activation on Tregs during autoimmunity has not been explored. In this study, we have shown that CD4+ Teff activation strongly boosts the expansion and suppressive activity of Tregs. This helper function of CD4+ T cells, which we believe to be novel, was observed in the pancreas and draining lymph nodes in mouse recipients of islet-specific Teffs and Tregs. Its physiological impact was assessed in autoimmune diabetes. When islet-specific Teffs were transferred alone, they induced diabetes. Paradoxically, when the same Teffs were cotransferred with islet-specific Tregs, they induced disease protection by boosting Treg expansion and suppressive function. RNA microarray analyses suggested that TNF family members were involved in the Teff-mediated Treg boost. In vivo experiments showed that this Treg boost was partially dependent on TNF but not on IL-2. This feedback regulatory loop between Teffs and Tregs may be critical to preventing or limiting the development of autoimmune diseases.

Enterovirus markers and serum CXCL10 in children with type 1 diabetes

Most patients with type 1 diabetes are considered to have a T-cell mediated autoimmune disease. The chemokine CXCL10 promotes the migration of activated T-cells. Virus infections might contribute to the pathogenesis of type 1 diabetes and enterovirus protein and/or genome have been detected in beta-cells from a majority of tested newly diagnosed children with type 1 diabetes. The chemokine CXCL10 is induced in human islet cells by enterovirus infections in vivo and in vitro, but is not expressed in islets from normal organ donors. Since CXCL10 is a chemokine known to be induced by virus infections and/or cellular damage, our aim was to study if levels of CXCL10 are elevated in serum from children with type 1 diabetes and whether it correlates to the presence of enterovirus markers. CXCL10, neutralizing antibody titer rises against certain enterovirus, and antibodies against GAD65 were measured in serum, and enterovirus PCR was performed on whole blood from 83 type 1 diabetes patients at onset, 48 siblings and 69 controls. CXCL10 was also measured in serum from 46 patients with proven enterovirus infection and in serum from 46 patients with other proven virus infections. The CXCL10 serum levels were not elevated in children at onset of type 1 diabetes and there was a considerable overlap between the groups with 99 (8-498) pg/ml in serum from children with type 1 diabetes, 120 (17-538) pg/ml in serum from controls, and 117 (7-448) pg/ml in siblings of the children with type 1 diabetes. The CXCL10 serum levels in patients with proven enterovirus infection were slightly increased compared to the levels in the other groups, 172 (0-585) pg/ml but there was no statistically significant difference. In contrast, CXCL10 serum levels in patients with other proven virus infections were clearly elevated 418 (34-611) pg/ml. Despite that elevated CXCL10 levels have been demonstrated in some groups of patients with type 1 diabetes, in this study the mean CXCL10 serum levels were not elevated in patients with type 1 diabetes neither in patients with proven enterovirus infection. In contrast, in patients with other virus infections the CXCL10 levels were elevated, presumably reflecting the severity or the site of infection. This suggests that local production of CXCL10 in the affected organ cannot be measured reproducible in serum and that its potential use in clinical practice is limited.

Virus infections: lessons from pancreas histology

Type 1 diabetes mellitus is a chronic autoimmune disease resulting from the progressive immune-mediated destruction of pancreatic beta cells in genetically susceptible individuals, with the likely contribution of environmental factors, among which viruses have been extensively studied. The pathologic hallmark of the disease is insulitis-a process characterized by islet infiltration of immunocompetent cells that has been well characterized in animal models of islet autoimmunity, and to a lesser extent, in humans. Insulitis characterization has provided valuable information to gain insights into the disease pathogenesis. We review the recent literature on the viral contribution to beta-cell destruction and dysfunction in type 1 diabetes, with particular reference to the pathology of the pancreatic islet in humans and in animal models of the disease.

Immune cell crosstalk in type 1 diabetes

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

Enteroviruses, type 1 diabetes and hygiene: a complex relationship

Type 1 diabetes (T1D) is an autoimmune disease in which the immune system mounts an attack on the host's insulin‐producing β cells. Because most cases of T1D cannot be attributed only to individual genetics, it is strongly inferred that there is a significant environmental contribution, such as infection, impacting disease development. The human enteroviruses (HEV) are common picornaviruses often implicated as triggers of human T1D, although precisely which of the numerous HEV may be involved in human T1D development is unknown. Experiments using non‐obese diabetic (NOD) mice, commonly used to model T1D, show that induction of T1D by HEV infection in NOD mice is a multifactorial process involving both the virus and the host. Interestingly, results demonstrate that HEV infection of NOD mice can also induce long‐term protection from T1D under certain conditions, suggesting that a similar mechanism may occur in humans. Based upon both experimental animal and observational human studies, we postulate that HEV have a dual role in T1D development and can either cause or prevent autoimmune disease. Whichever outcome occurs depends upon multiple variables in the host‐virus equation, many of which can be deduced from results obtained from NOD mouse studies. We propose that the background to the sharply rising T1D incidences observed in the 20th century correlates with increased levels of hygiene in human societies. Viewing T1D in this perspective suggests that potential preventative options could be developed. Copyright © 2009 John Wiley & Sons, Ltd.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: viruses, autoimmunity and immunoregulation

Based on studies in animal models, viral infections, in particular by enteroviruses, can accelerate or halt type 1 diabetes (T1D) development. Among factors that determine the outcome are the degree of viral replication in the target organ (viral titres), the tropism of the virus for beta cells, and the precise time-point of infection in relation to the diabetogenic process. Mechanisms underlying these phenomena have been assessed in mouse studies and should now be verified for human T1D. For enhancement of diabetes development, up-regulation of interferon pathways, expression of class-I major histocompatibility complexes and Toll-like receptor-dependent immunity appear important. In contrast, prevention of T1D involves pathways that the immune system usually invokes to shut down anti-viral responses to limit immunopathology, and which can 'clean out' autoreactive memory effector T cells as a bystander phenomenon: up-regulation of inhibitory molecules and invigoration of regulatory T cell (T(reg)) function. Importantly, these immunoregulatory processes also appear to foster and sustain persistent viral infections. Induction of immunoregulatory mechanisms, and in particular the phenotype and function of T(regs), is of interest therapeutically and will be discussed.

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.

Effect of Curcuma longa freeze dried rhizome powder with milk in STZ induced diabetic rats

This study deals with the effects of freeze dried rhizome powder of Curcuma longa (C. longa) dissolved in milk on normal as well as diabetic models. Diabetes of type II and type I was within 3 days of a single administration of doses of 45 and 65 mg kg(-1) of streptozotocin respectively. Various parameters such as blood glucose levels, triglycerides, total cholesterol, high density lipoprotein, very low density lipoprotein, low density lipoprotein, serum glutamic oxaloacetic transaminase, serum glutamic pyruvate transaminase, alkaline phosphatase, creatinine, hemoglobin, urine protein and urine sugar in addition to body weight were taken in to consideration and were analyzed after administration of variable doses of rhizome powder. The dose of 200 mg kg(-1) was identified as the most effective dose as it increased HDL, Hb and bw (P<0.05) with significant decrease in the levels of blood glucose, lipid profile and hepatoprotective enzymes (P<0.001).

Development of potential antiviral strategy against coxsackievirus B4

Coxsackievirus B4 (CVB4) can cause a broad range of diseases such as aseptic meningitis, meningoencephalitis, myocarditis, hepatitis, pancreatitis, gastroenteritis, necrotizing enterocolitis, pneumonia and sudden death in the neonates. CVB4 has also been implicated as a possible etiological agent for type 1 insulin dependent diabetes mellitus (IDDM). In this study, the possibility of RNA interference (RNAi) as a potential therapeutic approach to treat CVB4 infection was explored. The results showed that the Rhabdomyosarcoma (RD) cells treated with 19-mer siRNAs displayed high specificity against CVB4 replication without displaying any sign of target effects. The siRNA targeting the 3C(pro) region of CVB4 genome was also established to be the most effective in inhibition of CVB4 replication in RD cell line in a dosage dependent manner, indicating its potential to be developed as an antiviral strategy against CVB4.

Immunology of beta-cell destruction

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

Autoimmune disease in Lyn-deficient mice is dependent on an inflammatory environment established by IL-6

Lyn-deficient mice develop Ab-mediated autoimmune disease resembling systemic lupus erythematosus where hyperactive B cells are major contributors to pathology. In this study, we show that an inflammatory environment is established in Lyn(-/-) mice that perturbs several immune cell compartments and drives autoimmune disease. Lyn(-/-) leukocytes, notably B cells, are able to produce IL-6, which facilitates hyperactivation of B and T cells, enhanced myelopoiesis, splenomegaly, and, ultimately, generation of pathogenic autoreactive Abs. Lyn(-/-) dendritic cells show increased maturation, but this phenotype is independent of autoimmunity as it is reiterated in B cell-deficient Lyn(-/-) mice. Genetic deletion of IL-6 on a Lyn-deficient background does not alter B cell development, plasma cell accumulation, or dendritic cell hypermaturation, suggesting that these characteristics are intrinsic to the loss of Lyn. However, hyperactivation of B and T cell compartments, extramedullary hematopoiesis, expansion of the myeloid lineage and autoimmune disease are all ameliorated in Lyn(-/-)IL-6(-/-) mice. Importantly, our studies show that although Lyn(-/-) B cells may be autoreactive, it is the IL-6-dependent inflammatory environment they engender that dictates their disease-causing potential. These findings improve our understanding of the mode of action of anti-IL-6 and B cell-directed therapies in autoimmune and inflammatory disease treatment.

The activating receptor NKp46 is essential for the development of type 1 diabetes

The mechanism of action of natural killer (NK) cells in type 1 diabetes is still unknown. Here we show that the activating receptor NKp46 recognizes mouse and human ligands on pancreatic beta cells. NK cells appeared in the pancreas when insulitis progressed to type 1 diabetes, and NKp46 engagement by beta cells led to degranulation of NK cells. NKp46-deficient mice had less development of type 1 diabetes induced by injection of a low dose of streptozotocin. Injection of soluble NKp46 proteins into nonobese diabetic mice during the early phase of insulitis and the prediabetic stage prevented the development of type 1 diabetes. Our findings demonstrate that NKp46 is essential for the development of type 1 diabetes and highlight potential new therapeutic modalities for this disease.

Influence of microbial environment on autoimmunity

During protective immune responses, the adaptive arm of the immune system requires activation by signals provided by innate immunity and driven by microbial stimuli. Whether the same rules apply to autoimmune diseases involving clonal self-reactive T and B lymphocytes--a process referred to here as 'adaptive autoimmunity'--is not quite clear. Nevertheless, in these diseases, the innate-adaptive connection is likely to be influenced by the microbial environment. This review integrates the results of experiments analyzing autoimmunity in sterile versus nonsterile conditions and experiments testing the role of innate immune receptor signaling in autoimmunity. It proposes that autoimmune diseases can be divided into two groups, the pathogenesis of which either follows the rules of innate-adaptive connection or does not.

Regulatory T-cell counter-regulation by innate immunity is a barrier to transplantation tolerance

Innate immune signals foster adaptive immunity through activation of antigen-presenting cells. Recent in vitro evidence suggests that innate signaling may also contribute to immunity by countering the effects of regulatory T cells (T-regs), counter-regulation. We present in vivo evidence using a transgenic skin allograft model that the function of T-regs is lost in the setting of acute skin transplantation but remains intact when grafts were transplanted 1 month prior to allow surgery-induced inflammation to abate. Our findings identify T-reg counter-regulation as a naturally occurring process that accompanies transplantation and an important barrier to T-reg-mediated tolerance. Our finding further highlights the central role of regulatory cell deactivation in the initiation of the immune response.

The role of infections in the immunopathogensis of systemic sclerosis--evidence from serological studies

Infections are believed to often play a role in the immunopathogenesis of autoimmune disorders; such is the case in systemic sclerosis (SSc). In order to evaluate the potential role infections may have on the pathogenesis of SSc, we assessed serological reactivity against various infectious agents in patients with SSc and compared them with healthy controls. Serological samples obtained from 80 patients with SSc were compared with 296 compatible healthy controls. Both groups were of European origin. All samples were tested for the presence of antibodies directed against hepatitis B virus, hepatitis C virus, toxoplasmosis, rubella, CMV, EBV, and Treponema pallidum. We applied Bio-Rad commercial and experimental kits to assess most antigens and ELISA assays to complete the panel. Patients with SSc had elevated IgM and IgG against Toxoplasma gondii and against CMV. Higher titers were also detected against the hepatitis B virus core protein (recombinant HBc antigen) using MONOLISA anti-HBc Plus commercial kit (Bio-Rad). A significantly higher rate of IgM antibodies against the capsid antigen of the EBV was detected in SSc patients compared with healthy controls, as well. These data demonstrate that antibodies against CMV, HBV, and toxoplasmosis were detected more often in patients with SSc. This association implies that infectious agents may have a role in disease pathogenesis and expression.

Coxsackievirus B4 and type 1 diabetes pathogenesis: contribution of animal models

The role of enteroviruses, in particular type B coxsackieviruses (CV-B), in type 1 diabetes (T1D) pathogenesis is supported by epidemiological, clinical and experimental observations.The investigation of T1D pathogenesis benefits from the contribution of animal models called spontaneously diabetic. Among these animals the non-obese diabetic (NOD) mouse and the bio-breeding diabetes-prone (BBDP) rat present a genetic susceptibility manifested by the expression of an autoimmune diabetes similar to the pathology observed in human beings. Other models whose genetic predisposition is less known are of considerable contribution as well. Numerous major observations relative to several aspects of T1D pathogenesis in the context of CV-B infections, such as susceptibility, diabetogenicity, pancreatotropism, mechanisms of beta cells destruction and others, have been deduced thanks to investigations with animal models. Despite their limits, these models are necessary in improving our knowledge of the role of enteroviruses, like CV-B4, in the pathogenesis of T1D, and the recent advances ensuing from their contribution may have important therapeutic and preventive spin-offs.

Tissue-specific deletion of the coxsackievirus and adenovirus receptor protects mice from virus-induced pancreatitis and myocarditis

In cultured cells, infection by group B coxsackievirus (CVB) is mediated by the coxsackievirus and adenovirus receptor (CAR), but the importance of this molecule in CVB-induced disease has not been determined. We generated mice with tissue-specific ablation of CAR within each of two major CVB target organs, the pancreas and heart. In the pancreas, deletion of CAR resulted in a significant reduction in both virus titers and virus-induced tissue damage. Similarly, cardiomyocyte-specific CAR deletion resulted in a marked reduction in virus titer, infection-associated cytokine production, and histopathology within the heart. Consistent with the in vivo phenotype, CAR-deficient cardiomyocytes resisted infection in vitro. These results demonstrate a critical function for CAR in the pathogenesis of CVB infection in vivo and in virus tropism for the heart and pancreas.

Viruses and autoimmunity

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