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Background and Aims: Hepatitis B virus (HBV)-associated liver cirrhosis (LC), a common condition with high incidence and mortality rates, is often associated with diabetes mellitus (DM). However, the molecular mechanisms underlying impaired glucose regulation during HBV-associated LC remain unclear., Methods: Data from 63 patients with LC and 62 patients with LC-associated DM were analysed. Co-culture of NK cells and islet β cell lines were used to study the glucose regulation mechanism. A mouse model of LC was used to verify the effect of S100A8/A9 on the glucose regulation., Results: Higher levels of interferon (IFN)-γ derived from natural killer (NK) cells and lower levels of insulin emerged in the peripheral blood of patients with both LC and DM compared with those from patients with LC only. IFN-γ derived from NK cells facilitated β cell necroptosis and impaired insulin production. Furthermore, S100A8/A9 elevation in patients with both LC and DM was found to upregulate IFN-γ production in NK cells. Consistently, in the mouse model for LC, mice treated with carbon tetrachloride (CCL 4 ) and S100A8/A9 exhibited increased blood glucose, impaired insulin production, increased IFN-γ, and increased β cells necroptosis compared with those treated with CCL 4 . Mechanistically, S100A8/A9 activated the p38 MAPK pathway to increase IFN-γ production in NK cells. These effects were diminished after blocking RAGE., Conclusion: Together, the data indicate that IFN-γ produced by NK cells induces β cell necroptosis via the S100A8/A9-RAGE-p38 MAPK axis in patients with LC and DM. Reduced levels of S100A8/A9, NK cells, and IFN-γ could be valuable for the treatment of LC with DM. Accumulation of S100A8/A9 in patients with LC may indicate the emergence of DM., (© 2024. The Author(s).)

The COVID-19 pandemic has revealed a bidirectional relationship between SARS-CoV-2 infection and diabetes mellitus. Existing evidence strongly suggests hyperglycemia as an independent risk factor for severe COVID-19, resulting in increased morbidity and mortality. Conversely, recent studies have reported new-onset diabetes following SARS-CoV-2 infection, hinting at a potential direct viral attack on pancreatic beta cells. In this review, we explore how hyperglycemia, a hallmark of diabetes, might influence SARS-CoV-2 entry and accessory proteins in pancreatic β-cells. We examine how the virus may enter and manipulate such cells, focusing on the role of the spike protein and its interaction with host receptors. Additionally, we analyze potential effects on endosomal processing and accessory proteins involved in viral infection. Our analysis suggests a complex interplay between hyperglycemia and SARS-CoV-2 in pancreatic β-cells. Understanding these mechanisms may help unlock urgent therapeutic strategies to mitigate the detrimental effects of COVID-19 in diabetic patients and unveil if the virus itself can trigger diabetes onset.

The association between chronic HCV infection and type 2 diabetes mellitus (T2DM) has been established; however, there is limited research on β-cell function particularly in the pre-diabetic population. Here, we evaluated indices of β-cell function and insulin sensitivity across the spectrum from normal glucose tolerance to T2DM in individuals with and without chronic hepatitis C (CHC), and the effects of antiviral treatments on these variables. A total of 153 non-cirrhotic, non-fibrotic CHC patients with a BMI <25 were enrolled in the study. Among them, 119 were successfully treated with either direct acting antiviral (DAA) drugs or pegylated interferon/ribavirin (IFN/RBV) anti-HCV therapy. Fasting state- and oral glucose tolerance test (OGTT)-derived indexes were used to evaluate β-cell function and insulin sensitivity. Among all subjects, 19 (13%) had T2DM and 21% exhibited pre-diabetes including 8% isolated impaired fasting glucose (IFG) and 13% combined IFG and impaired glucose tolerance (IGT). Early and total insulin secretion adjusted for the degree of insulin resistance were decreased in pre-diabetic CHC patients compared to HCV-uninfected individuals. Viral eradication through DAA or IFN/RBV therapy demonstrated positive impacts on insulin sensitivity and β-cell function in CHC patients who achieved sustained virologic response (SVR), regardless of fasting or OGTT state. These findings emphasize the role of HCV in the development of β-cell dysfunction, while also suggesting that viral eradication can improve insulin secretion, reverse insulin resistance, and ameliorate glycemic control. These results have important implications for managing pre-diabetic CHC patients and could prevent diabetes-related clinical manifestations and complications., Competing Interests: Conflict of interest Prof. Xinwen Chen is an editorial board member for Virologica Sinica and was not involved in the editorial review or the decision to publish this article. All authors declare that there are no competing interests., (Copyright © 2024 The Authors. Publishing services by Elsevier B.V. All rights reserved.)

Diabetes mellitus (DM) is comprised of two predominant subtypes: type 1 diabetes mellitus (T1DM), accounting for approximately 5 % of cases worldwide and resulting from autoimmune destruction of insulin-producing β-cells, and type 2 (T2DM), accounting for approximately 95 % of cases globally and characterized by the inability of pancreatic β-cells to meet the demand for insulin due to a relative β-cell deficit in the setting of peripheral insulin resistance. Both types of DM involve derangement of glucose metabolism and are metabolic diseases generally considered to be initiated by a combination of genetic and environmental factors. Viruses have been reported to play a role as infectious etiological factors in the initiation of both types of DM in predisposed individuals. Among the reported viral infections causing DM in humans, the most studied include coxsackie B virus, cytomegalovirus and hepatitis C virus. The recent COVID-19 pandemic has highlighted the diabetogenic potential of SARS-CoV-2, rekindling interest in the field of virus-induced diabetes (VID). This review discusses the reported mechanisms of viral-induced DM, addressing emerging concepts in VID, as well as highlighting areas where knowledge is lacking, and further investigation is warranted., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: To explore the mechanism of insulin secretion dysfunction in pancreatic beta cells induced by N-glycosylation mediated by an infection from the hepatitis C virus (HCV)., Methods: Min6 cell models infected with HCV and stimulated with glucose were constructed. Meanwhile, an HCV-infected animal model and a type 2 diabetes mellitus (T2DM) rat model were constructed. Glucose uptake in the Min6 cells was detected, and insulin secretion was detected by ELISA. Flow cytometry, immunofluorescence staining, Western blotting, RT-qPCR, and lectin blotting were used to detect the expression levels of related proteins and mRNA, as well as the level of N-glycosylation. HE staining was used to observe the pathological changes in the pancreatic tissue, and an oral glucose tolerance test (OGTT) was used to evaluate the glucose tolerance of the rats., Results: Compared with the NC group, the expression levels of GnT-IVa, GLUT2, galectin-9, and voltage-dependent calcium channel 1.2 (Cav1.2) were significantly downregulated in the HCV-infected group. The ATP-sensitive potassium channel (K ATP ) component proteins SUR1 and Kir6.2 were significantly upregulated, while intracellular glucose intake and insulin secretion decreased, N-glycosylation levels and ATP levels significantly decreased, and the overexpression of GnT-IVa reversed the effect of the HCV infection. However, treatment with the glycosylation inhibitor kifunensine (KIF) or the K ATP channel activator diazine (Dia) reversed the effects of the overexpression of GnT-IVa. In the animal experiments, HE staining revealed serious pathological injuries in the pancreatic tissue of the HCV-infected rats, with decreased glucose tolerance and glycosylation levels, decreased insulin secretion, downregulated expression of GnT-IVa, GLUT2, and Cav1.2, and upregulated expression of SUR1 and Kir6.2. The overexpression treatment of GnT-IVa or the K ATP channel antagonist miglinide reversed the effects of HCV., Conclusion: HCV infection inhibits GLUT2 N-glycosylation on the pancreatic β cell surface by downregulating the expression of GnT-IVa and then activates the K ATP pathway, which ultimately leads to disturbances in insulin secretion., (© 2023. The Author(s).)

Two recent reports denoted the potential of SARS-CoV-2 to directly infect β-cells and the possible fate of β-cells under COVID-19. The fight against SARS-CoV-2 will continue to develop more effective therapeutic strategies for diabetes., (© 2021 The Authors. Journal of Diabetes Investigation published by Asian Association for the Study of Diabetes (AASD) and John Wiley & Sons Australia, Ltd.)

Although spermatogenic dysfunction is widely found in patients with human immunodeficiency virus (HIV), the underlying reasons remain unclear. Thus far, potential hypotheses involving viral reservoirs, testicular inflammation, hormone imbalance, and cachexia show inconsistent correlation with spermatogenic dysfunction. Here, northern pig-tailed macaques (NPMs) exhibited marked spermatogenic dysfunction after long-term infection with simian immunodeficiency virus (SIVmac239), with significant decreases in Johnsen scores, differentiated spermatogonial stem cells, and testicular proliferating cells. The above hypotheses were also evaluated. Results showed no differences between SIV- and SIV+ NPMs, except for an increase in follicle stimulating hormone (FSH) during SIV infection, which had no direct effect on the testes. However, long-term SIVmac239 infection undermined pancreatic islet β cell function, partly represented by significant reductions in cellular counts and autophagy levels. Pancreatic islet β cell dysfunction led to glucose metabolism disorder at the whole-body level, which inhibited lactate production by Sertoli cells in testicular tissue. As lactate is the main energy substrate for developing germ cells, its decrease was strongly correlated with spermatogenic dysfunction. Therefore, glucose metabolism disorder appears to be a primary cause of spermatogenic dysfunction in NPMs with long-term SIVmac239 infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Song, Zhang, Zhang, Wang, Pang, Tian and Zheng.)

Emerging evidence points toward an intricate relationship between the pandemic of coronavirus disease 2019 (COVID-19) and diabetes. While preexisting diabetes is associated with severe COVID-19, it is unclear whether COVID-19 severity is a cause or consequence of diabetes. To mechanistically link COVID-19 to diabetes, we tested whether insulin-producing pancreatic β cells can be infected by SARS-CoV-2 and cause β cell depletion. We found that the SARS-CoV-2 receptor, ACE2, and related entry factors (TMPRSS2, NRP1, and TRFC) are expressed in β cells, with selectively high expression of NRP1. We discovered that SARS-CoV-2 infects human pancreatic β cells in patients who succumbed to COVID-19 and selectively infects human islet β cells in vitro. We demonstrated that SARS-CoV-2 infection attenuates pancreatic insulin levels and secretion and induces β cell apoptosis, each rescued by NRP1 inhibition. Phosphoproteomic pathway analysis of infected islets indicates apoptotic β cell signaling, similar to that observed in type 1 diabetes (T1D). In summary, our study shows SARS-CoV-2 can directly induce β cell killing., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Recent clinical data have suggested a correlation between coronavirus disease 2019 (COVID-19) and diabetes. Here, we describe the detection of SARS-CoV-2 viral antigen in pancreatic beta cells in autopsy samples from individuals with COVID-19. Single-cell RNA sequencing and immunostaining from ex vivo infections confirmed that multiple types of pancreatic islet cells were susceptible to SARS-CoV-2, eliciting a cellular stress response and the induction of chemokines. Upon SARS-CoV-2 infection, beta cells showed a lower expression of insulin and a higher expression of alpha and acinar cell markers, including glucagon and trypsin1, respectively, suggesting cellular transdifferentiation. Trajectory analysis indicated that SARS-CoV-2 induced eIF2-pathway-mediated beta cell transdifferentiation, a phenotype that could be reversed with trans-integrated stress response inhibitor (trans-ISRIB). Altogether, this study demonstrates an example of SARS-CoV-2 infection causing cell fate change, which provides further insight into the pathomechanisms of COVID-19., Competing Interests: Declaration of interests R.E.S. is on the scientific advisory board of Miromatrix Inc. and is a paid consultant and speaker for Alnylam Inc. The other authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The generation of a human pancreatic beta cell line which reproduces the responses seen in primary beta cells, but is amenable to propagation in culture, has long been an important goal in diabetes research. This is particularly true for studies focussing on the role of enteroviral infection as a potential cause of beta-cell autoimmunity in type 1 diabetes. In the present work we made use of a clonal beta cell line (1.1B4) available from the European Collection of Authenticated Cell Cultures, which had been generated by the fusion of primary human beta-cells with a pancreatic ductal carcinoma cell, PANC-1. Our goal was to study the factors allowing the development and persistence of a chronic enteroviral infection in human beta-cells. Since PANC-1 cells have been reported to support persistent enteroviral infection, the hybrid 1.1B4 cells appeared to offer an ideal vehicle for our studies. In support of this, infection of the cells with a Coxsackie virus isolated originally from the pancreas of a child with type 1 diabetes, CVB4.E2, at a low multiplicity of infection, resulted in the development of a state of persistent infection. Investigation of the molecular mechanisms suggested that this response was facilitated by a number of unexpected outcomes including an apparent failure of the cells to up-regulate certain anti-viral response gene products in response to interferons. However, more detailed exploration revealed that this lack of response was restricted to molecular targets that were either activated by, or detected with, human-selective reagents. By contrast, and to our surprise, the cells were much more responsive to rodent-selective reagents. Using multiple approaches, we then established that populations of 1.1B4 cells are not homogeneous but that they contain a mixture of rodent and human cells. This was true both of our own cell stocks and those held by the European Collection of Authenticated Cell Cultures. In view of this unexpected finding, we developed a strategy to harvest, isolate and expand single cell clones from the heterogeneous population, which allowed us to establish colonies of 1.1B4 cells that were uniquely human (h1.1.B4). However, extensive analysis of the gene expression profiles, immunoreactive insulin content, regulated secretory pathways and the electrophysiological properties of these cells demonstrated that they did not retain the principal characteristics expected of human beta cells. Our data suggest that stocks of 1.1B4 cells should be evaluated carefully prior to their use as a model human beta-cell since they may not retain the phenotype expected of human beta-cells., (© 2021. The Author(s).)

The link between COVID-19 infection and diabetes has been explored in several studies since the start of the pandemic, with associations between comorbid diabetes and poorer prognosis in patients infected with the virus and reports of diabetic ketoacidosis occurring with COVID-19 infection. As such, significant interest has been generated surrounding mechanisms by which the virus may exert effects on the pancreatic β cells. In this review, we consider possible routes by which SARS-CoV-2 may impact β cells. Specifically, we outline data that either support or argue against the idea of direct infection and injury of β cells by SARS-CoV-2. We also discuss β cell damage due to a "bystander" effect in which infection with the virus leads to damage to surrounding tissues that are essential for β cell survival and function, such as the pancreatic microvasculature and exocrine tissue. Studies elucidating the provocation of a cytokine storm following COVID-19 infection and potential impacts of systemic inflammation and increases in insulin resistance on β cells are also reviewed. Finally, we summarize the existing clinical data surrounding diabetes incidence since the start of the COVID-19 pandemic.

Metabolic diseases are associated with an increased risk of severe COVID-19 and conversely, new-onset hyperglycemia and complications of preexisting diabetes have been observed in COVID-19 patients. Here, we performed a comprehensive analysis of pancreatic autopsy tissue from COVID-19 patients using immunofluorescence, immunohistochemistry, RNA scope and electron microscopy and detected SARS-CoV-2 viral infiltration of beta-cells in all patients. Using SARS-CoV-2 pseudoviruses, we confirmed that isolated human islet cells are permissive to infection. In eleven COVID-19 patients, we examined the expression of ACE2, TMPRSS and other receptors and factors, such as DPP4, HMBG1 and NRP1, that might facilitate virus entry. Whereas 70% of the COVID-19 patients expressed ACE2 in the vasculature, only 30% displayed ACE2-expression in beta-cells. Even in the absence of manifest new-onset diabetes, necroptotic cell death, immune cell infiltration and SARS-CoV-2 viral infection of pancreatic beta-cells may contribute to varying degrees of metabolic dysregulation in patients with COVID-19.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by pancreatic islet inflammation (insulitis) and specific pancreatic β-cell destruction by an immune attack. Although the precise underlying mechanisms leading to the autoimmune assault remain poorly understood, it is well accepted that insulitis takes place in the context of a conflicting dialogue between pancreatic β-cells and the immune cells. Moreover, both host genetic background (i.e., candidate genes) and environmental factors (e.g., viral infections) contribute to this inadequate dialogue. Accumulating evidence indicates that type I interferons (IFNs), cytokines that are crucial for both innate and adaptive immune responses, act as key links between environmental and genetic risk factors in the development of T1D. This chapter summarizes some relevant pathways involved in β-cell dysfunction and death, and briefly reviews how enteroviral infections and genetic susceptibility can impact insulitis. Moreover, we present the current evidence showing that, in β-cells, type I IFN signaling pathway activation leads to several outcomes, such as long-lasting major histocompatibility complex (MHC) class I hyperexpression, endoplasmic reticulum (ER) stress, epigenetic changes, and induction of posttranscriptional as well as posttranslational modifications. MHC class I overexpression, when combined with ER stress and posttranscriptional/posttranslational modifications, might lead to sustained neoantigen presentation to immune system and β-cell apoptosis. This knowledge supports the concept that type I IFNs are implicated in the early stages of T1D pathogenesis. Finally, we highlight the promising therapeutic avenues for T1D treatment directed at type I IFN signaling pathway., Competing Interests: Disclosure statement The authors have nothing to disclose., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Viral infection is one environmental factor that may contribute to the initiation of pancreatic β-cell destruction during the development of autoimmune diabetes. Picornaviruses, such as encephalomyocarditis virus (EMCV), induce a pro-inflammatory response in islets leading to local production of cytokines, such as IL-1, by resident islet leukocytes. Furthermore, IL-1 is known to stimulate β-cell expression of iNOS and production of the free radical nitric oxide. The purpose of this study was to determine whether nitric oxide contributes to the β-cell response to viral infection. We show that nitric oxide protects β-cells against virally mediated lysis by limiting EMCV replication. This protection requires low micromolar, or iNOS-derived, levels of nitric oxide. At these concentrations nitric oxide inhibits the Krebs enzyme aconitase and complex IV of the electron transport chain. Like nitric oxide, pharmacological inhibition of mitochondrial oxidative metabolism attenuates EMCV-mediated β-cell lysis by inhibiting viral replication. These findings provide novel evidence that cytokine signaling in β-cells functions to limit viral replication and subsequent β-cell lysis by attenuating mitochondrial oxidative metabolism in a nitric oxide-dependent manner., Competing Interests: Conflict of interest—The authors declare that they have no conflicts of interest with the contents of this article., (© 2020 Stafford et al.)

Increasing evidence demonstrated that the expression of Angiotensin I-Converting Enzyme type 2 (ACE2) is a necessary step for SARS-CoV-2 infection permissiveness. In light of the recent data highlighting an association between COVID-19 and diabetes, a detailed analysis aimed at evaluating ACE2 expression pattern distribution in human pancreas is still lacking. Here, we took advantage of INNODIA network EUnPOD biobank collection to thoroughly analyze ACE2, both at mRNA and protein level, in multiple human pancreatic tissues and using several methodologies. Using multiple reagents and antibodies, we showed that ACE2 is expressed in human pancreatic islets, where it is preferentially expressed in subsets of insulin producing β -cells. ACE2 is also highly expressed in pancreas microvasculature pericytes and moderately expressed in rare scattered ductal cells. By using different ACE2 antibodies we showed that a recently described short-ACE2 isoform is also prevalently expressed in human β -cells. Finally, using RT-qPCR, RNA-seq and High-Content imaging screening analysis, we demonstrated that pro-inflammatory cytokines, but not palmitate, increase ACE2 expression in the β -cell line EndoC- β H1 and in primary human pancreatic islets. Taken together, our data indicate a potential link between SARS-CoV-2 and diabetes through putative infection of pancreatic microvasculature and/or ductal cells and/or through direct β -cell virus tropism., (Copyright © 2020 Fignani, Licata, Brusco, Nigi, Grieco, Marselli, Overbergh, Gysemans, Colli, Marchetti, Mathieu, Eizirik, Sebastiani and Dotta.)

Using immunohistochemistry, enterovirus capsid proteins were demonstrated in pancreatic islets of patients with type 1 diabetes. Virus proteins are mainly located in beta cells, supporting the hypothesis that enterovirus infections may contribute to the pathogenesis of type 1 diabetes. In samples of pancreatic tissue, enterovirus RNA was also detected, but in extremely small quantities and in a smaller proportion of cases compared to the enteroviral protein. Difficulties in detecting viral RNA could be due to the very small number of infected cells, the possible activity of PCR inhibitors, and the presence-during persistent infection-of the viral genome in unencapsidated forms. The aim of this study was twofold: (a) to examine if enzymes or other compounds in pancreatic tissue could affect the molecular detection of encapsidated vs. unencapsidated enterovirus forms, and (b) to compare the sensitivity of RT-PCR methods used in different laboratories. Dilutions of encapsidated and unencapsidated virus were spiked into human pancreas homogenate and analyzed by RT-PCR. Incubation of pancreatic homogenate on wet ice for 20 h did not influence the detection of encapsidated virus. In contrast, a 15-min incubation on wet ice dramatically reduced detection of unencapsidated forms of virus. PCR inhibitors could not be found in pancreatic extract. The results show that components in the pancreas homogenate may selectively affect the detection of unencapsidated forms of enterovirus. This may lead to difficulties in diagnosing persisting enterovirus infection in the pancreas of patients with type 1 diabetes.

The vast majority of type 1 diabetes (T1D) genetic association signals lie in noncoding regions of the human genome. Many have been predicted to affect the expression and secondary structure of long noncoding RNAs (lncRNAs), but the contribution of these lncRNAs to the pathogenesis of T1D remains to be clarified. Here, we performed a complete functional characterization of a lncRNA that harbors a single nucleotide polymorphism (SNP) associated with T1D, namely, Lnc13 Human pancreatic islets harboring the T1D-associated SNP risk genotype in Lnc13 (rs917997*CC) showed higher STAT1 expression than islets harboring the heterozygous genotype (rs917997*CT). Up-regulation of Lnc13 in pancreatic β-cells increased activation of the proinflammatory STAT1 pathway, which correlated with increased production of chemokines in an allele-specific manner. In a mirror image, Lnc13 gene disruption in β-cells partially counteracts polyinosinic-polycytidylic acid (PIC)-induced STAT1 and proinflammatory chemokine expression. Furthermore, we observed that PIC, a viral mimetic, induces Lnc13 translocation from the nucleus to the cytoplasm promoting the interaction of STAT1 mRNA with (poly[rC] binding protein 2) (PCBP2). Interestingly, Lnc13 -PCBP2 interaction regulates the stability of the STAT1 mRNA, sustaining inflammation in β-cells in an allele-specific manner. Our results show that the T1D-associated Lnc13 may contribute to the pathogenesis of T1D by increasing pancreatic β-cell inflammation. These findings provide information on the molecular mechanisms by which disease-associated SNPs in lncRNAs influence disease pathogenesis and open the door to the development of diagnostic and therapeutic approaches based on lncRNA targeting., Competing Interests: The authors declare no competing interest.

Chronic hepatitis C virus (HCV) infection has a close association with type 2 diabetes mellitus. Although the mechanisms of insulin resistance in chronic hepatitis C (CHC) patients have been extensively studied, little attention has been given to the role of β-cell function in HCV-associated diabetes. Here, we analysed β-cell function in CHC patients and HCV-infected mouse model and found in addition to insulin resistance, impaired pancreatic β-cell function occurred in CHC patients and HCV-infected C/OTg mice, not only in diabetic individuals but also in individuals with impaired fasting glucose levels. Both first-phase and second-phase insulin secretion were impaired, at least partially due to the reduction of exocytosis of secretory insulin-containing granules following HCV infection. Up-regulated p38δ in HCV-infected β-cells resulted in inactivation of protein kinase D (PKD), which was responsible for impaired insulin secretory capacity of β-cells. Thus, impaired insulin secretion due to HCV infection in β-cells contributes to HCV-associated type 2 diabetes. These findings provided a new inspiration for the important prognostic and therapeutic implications in the management of CHC patients with impaired fasting glucose., (© 2020 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

Viral infection is an environmental trigger that has been suggested to initiate pancreatic β-cell damage, leading to the development of autoimmune diabetes. Viruses potently activate the immune system and can damage β cells by either directly infecting them or stimulating the production of secondary effector molecules (such as proinflammatory cytokines) during bystander activation. However, how and where β cells recognize viruses is unclear, and the antiviral responses that are initiated following virus recognition are incompletely understood. In this study, we show that the β-cell response to dsRNA, a viral replication intermediate known to activate antiviral responses, is determined by the cellular location of sensing (intracellular versus extracellular) and differs from the cellular response to cytokine treatment. Using biochemical and immunological methods, we show that β cells selectively respond to intracellular dsRNA by expressing type I interferons (IFNs) and inducing apoptosis, but that they do not respond to extracellular dsRNA. These responses differ from the activities of cytokines on β cells, which are mediated by inducible nitric oxide synthase expression and β-cell production of nitric oxide. These findings provide evidence that the antiviral activities of type I IFN production and apoptosis are elicited in β cells via the recognition of intracellular viral replication intermediates and that β cells lack the capacity to respond to extracellular viral intermediates known to activate innate immune responses., (© 2020 Shaheen et al.)

Viral infection is a putative causal factor for the development of type 1 diabetes, but the exact pathogenic mechanism of virus-induced diabetes (VID) remains unclear. Here, to identify the critical factors that regulate VID, we analyzed encephalomyocarditis D (EMC-D) VID-sensitive DBA/2 mice in comparison with resistant B6 mice. EMC-D virus-induced cell death occurred more frequently in DBA/2 β-cells than in B6 β-cells with 100U/ml IFN-β priming in vitro. We therefore purified β-cells using flow cytometry from mice two days after EMC-D virus infection and subjected them to microarray analysis. As a results, innate immune response pathway was found to be enriched in B6 β-cells. The signal transducer and activator of transcription 2 (Stat2) gene interacted with genes in the pathway. Stat2 gene expression levels were lower in DBA/2 mice than in B6 mice, restrictive to β-cells. Moreover, administration of IFN-β failed to upregulate Stat2 gene in DBA/2 β-cells than in those of B6 in vivo. The viral titer significantly increased only in the DBA/2 pancreas. Thus, these provided data suggest that impaired upregulation of Stat2 gene restrictive to β-cells at the early stage of infection is responsible for VID development in DBA/2 mice., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Studies performed in humans and animal models have implicated the environment in the etiology of type 1 diabetes (T1D), but the nature and timing of the interactions triggering β cell autoimmunity are poorly understood. Virus infections have been postulated to be involved in disease mechanisms, but the underlying mechanisms are not known. It is exceedingly difficult to establish a cause-and-effect relationship between viral infection and diabetes in humans. Thus, we have used the BioBreeding Diabetes-Resistant (BBDR) and the LEW1.WR1 rat models of virus-induced disease to elucidate how virus infection leads to T1D. The immunophenotype of these strains is normal, and spontaneous diabetes does not occur in a specific pathogen-free environment. However, β cell inflammation and diabetes with many similarities to the human disease are induced by infection with the parvovirus Kilham rat virus (KRV). KRV-induced diabetes in the BBDR and LEW1.WR1 rat models is limited to young animals and can be induced in both male and female rats. Thus, these animals provide a powerful experimental tool to identify mechanisms underlying virus-induced T1D development.

It has been suggested that the persistence of coxsackieviruses-B (CV-B) in pancreatic beta cells plays a role in the pathogenesis of type 1 diabetes (T1D). Yet, immunological effectors, especially natural killer (NK) cells, are supposed to clear virus-infected cells. Therefore, an evaluation of the response of NK cells to pancreatic beta cells persistently infected with CV-B4 was conducted. A persistent CV-B4 infection was established in 1.1B4 pancreatic beta cells. Infectious particles were found in supernatants throughout the culture period. The proportion of cells containing viral protein VP1 was low (< 5%), although a large proportion of cells harbored viral RNA (around 50%), whilst cell viability was preserved. HLA class I cell surface expression was downregulated in persistently infected cultures, but HLA class I mRNA levels were unchanged in comparison with mock-infected cells. The cytolytic activities of IL-2-activated non-adherent peripheral blood mononuclear cells (PBMCs) and of NK cells were higher towards persistently infected cells than towards mock-infected cells, as assessed by an LDH release assay. Impaired cytolytic activity of IL-2-activated non-adherent PBMCs from patients with T1D towards infected beta cells was observed. In conclusion, pancreatic beta cells persistently infected with CV-B4 can be lysed by NK cells, implying that impaired cytolytic activity of these effector cells may play a role in the persistence of CV-B in the host and thus in the viral pathogenesis of T1D.

Viruses are implicated in autoimmune destruction of pancreatic islet β cells, which results in insulin deficiency and type 1 diabetes (T1D) 1-4 . Certain enteroviruses can infect β cells in vitro 5 , have been detected in the pancreatic islets of patients with T1D 6 and have shown an association with T1D in meta-analyses 4 . However, establishing consistency in findings across studies has proven difficult. Obstacles to convincingly linking RNA viruses to islet autoimmunity may be attributed to rapid viral mutation rates, the cyclical periodicity of viruses 7 and the selection of variants with altered pathogenicity and ability to spread in populations. β cells strongly express cell-surface coxsackie and adenovirus receptor (CXADR) genes, which can facilitate enterovirus infection 8 . Studies of human pancreata and cultured islets have shown significant variation in enteroviral virulence to β cells between serotypes and within the same serotype 9,10 . In this large-scale study of known eukaryotic DNA and RNA viruses in stools from children, we evaluated fecally shed viruses in relation to islet autoimmunity and T1D. This study showed that prolonged enterovirus B rather than independent, short-duration enterovirus B infections may be involved in the development of islet autoimmunity, but not T1D, in some young children. Furthermore, we found that fewer early-life human mastadenovirus C infections, as well as CXADR rs6517774, independently correlated with islet autoimmunity.

Purpose of the Review: The aim of this review is to discuss recent data pointing at an involvement of human endogenous retroviruses (HERVs) in type 1 diabetes (T1D) onset and progression., Recent Findings: The envelope protein of HERV-W family, named HERV-W-Env, was detected in pancreata from T1D patients and was shown to display pro-inflammatory properties and direct toxicity toward pancreatic beta cells. The etiopathogenesis of T1D remains elusive, even if conventional environmental viral infections have been recurrently involved. Nonetheless, a new category of pathogens may provide the missing link between genetic susceptibility and environmental factors long thought to contribute to T1D onset. A number of studies have now shown that HERV sequences, which are normally inactivated or repressed in the human genome, could be activated by environmental viruses. Thus, if similarly activated by viruses associated with T1D, disregarded HERV genes may underlie T1D genetic susceptibility. Moreover, once expressed, HERV elements may display broad pathogenic properties, which identify them as potential new therapeutic targets.

Influenza virus infection is associated with type 1 diabetes (T1DM), but its pathogenesis remains unclear. Here, our study found that one of the monoclonal antibodies against H1N1 influenza virus hemagglutinin(HA) cross-reacted with human pancreatic tissue and further demonstrated that it binded to rat islet β-cells. We immunoprecipitated islet protein with this cross-reactive antibody and identified the bound antigen as prohibitin by mass spectrometry. We then expressed the prohibitin protein in bacteria and confirmed the antibody binding to prohibitin by Western blot. We also verified the cross-reactivity of the antibody by prohibitin-siRNA transfection in islet beta cells. We conclude that prohibitin is an autoantigen that cross-reacts with influenza virus HA. The correlation between the autoantigen prohibitin and type 1 diabetes remains to be investigated., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Ljungan virus (LV) has not confirmed to associate with any human disease, but a possible connection with type 1 diabetes has been suggested. LV is a rodent-borne picornavirus that induces a diabetes-like condition in rodents. Approximately 30% of adults and 60% of children are seropositive in Finland. The Finnish Type 1 Diabetes Prediction and Prevention study enabled the use of very well characterized sample panels from children seroconverted to positivity for multiple islet autoantibodies during their prospective observation from birth; in addition, samples from age, sex, human leukocyte antigen (HLA), and residence area matched control children., Methods: We analyzed LV IgG seroprevalence in 102 case children (65 had also developed type 1 diabetes), in addition to nondiabetic control children. LV and human parechovirus (HPeV) immunofluorescence assays were used to analyze LV and HPeV-specific IgG from 102 plasma samples taken at the time of islet autoantibody appearance and from 204 samples from the matched control children., Results: Altogether 46.1% of the case and 50.7% of the control children were positive for LV IgG (odds ratio 0.8; 95% confidence interval, 0.47-1.36; P = 0.416) and 67.6% versus 79.8% were positive for HPeV IgG, respectively (odds ratio 0.49, 0.27-0.9, P = 0.023)., Conclusions: Thus, no risk associations between LV or HPeV-specific IgG and islet autoimmunity were observed. However, a trend for significantly higher prevalence of HPeV antibodies in control children (P = 0.023) suggests a possible protective association of this virus with islet autoimmunity.

Type 1 diabetes (T1D) is an autoimmune disease characterized by islet inflammation and progressive pancreatic β cell destruction. The disease is triggered by a combination of genetic and environmental factors, but the mechanisms leading to the triggering of early innate and late adaptive immunity and consequent progressive pancreatic β cell death remain unclear. The insulin-producing β cells are active secretory cells and are thus particularly sensitive to endoplasmic reticulum (ER) stress. ER stress plays an important role in the pathologic pathway leading to autoimmunity, islet inflammation, and β cell death. We show here that group B coxsackievirus (CVB) infection, a putative causative factor for T1D, induces a partial ER stress in rat and human β cells. The activation of the PERK/ATF4/CHOP branch is blunted while the IRE1α branch leads to increased spliced XBP1 expression and c-Jun N-terminal kinase (JNK) activation. Interestingly, JNK1 activation is essential for CVB amplification in both human and rat β cells. Furthermore, a chemically induced ER stress preceding viral infection increases viral replication, in a process dependent on IRE1α activation. Our findings show that CVB tailors the unfolded protein response in β cells to support their replication, preferentially triggering the pro-viral IRE1α/XBP1s/JNK1 pathway while blocking the pro-apoptotic PERK/ATF4/CHOP pathway., (© 2019 The Author(s) Published by S. Karger AG, Basel.)

Context: Recent studies have suggested that influenza A virus (IAV) might be involved in the etiology of diabetes., Objective and Methods: To address this question, we tested the ability of H1N1 pandemic IAV to infect, replicate, and damage human β cells/pancreatic islets in vitro and induce pancreatic damage and/or glucose metabolism alterations in chemical and autoimmune models of β cell damage in vivo. Moreover, we looked for direct and/or indirect evidence of correlation between IAV infection and autoimmunity/diabetes in humans., Results: Human H1N1 A/California/2009-derived viruses infected human pancreatic islets in vitro, inducing a proinflammatory response associated with substantial increases of CXCL9 and CXCL10 release. In vivo, infected mice showed a clear susceptibility to the virus, with its localization also found in extrapulmonary organs, including the pancreas. Infection was able to induce mild modifications of glycemia in C57B6 mice after chemical damage of islets but did not modulate the autoimmune damage of islets in NOD mice. One of 69 nasopharyngeal swabs collected from patients at the onset of type 1 diabetes yielded positive results for IAV. Pancreas sections from 17 organ donors available from the Network for Pancreatic Organ Donors With Diabetes showed the persistence of CXCL10-positive cells in islet autoimmunity-positive subjects; however, extremely rare cells stained for viral RNA and not preferentially in autoimmune subjects., Conclusion: Influenza H1N1 pdm strains are able to infect and replicate in mammalian pancreatic cells both in vitro and in vivo but did not cause any functional impairment consistent with diabetes.

The development of islet autoimmunity and type 1 diabetes has long been linked with enteroviral infection but a causal relationship has proven hard to establish. This is partly because much of the epidemiological evidence derives from studies of neutralising antibody generation in blood samples while less attention has been paid to the pancreatic beta cell as a site of infection. Nevertheless, recent studies have revealed that beta cells express specific enteroviral receptors and that they can sustain a productive enteroviral infection. Importantly, they can also mount antiviral responses which attenuate viral replication and may favour the establishment of a persistent enteroviral infection. Together, these responses combine to create the Trojan horse by which enteroviruses might precipitate islet autoimmunity., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Introduction: Virus infections have long been considered as a possible cause of type 1 diabetes (T1D). One virus group, enteroviruses (EVs), has been studied extensively, and clinical development of a vaccine against T1D-associated EV types has started., Areas Covered: Epidemiological studies have indicated an association between EVs and T1D. These viruses have a strong tropism for insulin-producing β-cells; the destruction of these cells leads to T1D. The exact mechanisms by which EVs could cause T1D are not known, but direct infection of β-cells and virus-induced inflammation may play a role. Recent studies have narrowed down the epidemiological association to a subset of EVs: group B coxsackieviruses (CVBs). These findings have prompted efforts to develop vaccines against CVBs. Prototype CVB vaccines have prevented both infection and CVB-induced diabetes in mice. This review summarizes recent progress in the field and the specifics of what could constitute the first human vaccine developed for a chronic autoimmune disease., Expert Commentary: Manufacturing of a clinical CVB vaccine as well as preclinical studies are currently in progress in order to enable clinical testing of the first CVB vaccine. Ongoing scientific research projects can significantly facilitate this effort by providing insights into the mechanisms of the CVB-T1D association.

Pancreatic islet transplantation is a promising treatment for type 1 diabetes mellitus offering improved glycaemic control by restoring insulin production. Improved human pancreatic islet isolation has led to higher islet transplantation success. However, as many as 50% of islets are lost after transplantation due to immune responses and cellular injury, gene therapy presents a novel strategy to protect pancreatic islets for improved survival post-transplantation. To date, most of the vectors used in clinical trials and gene therapy studies have been derived from mammalian viruses such as adeno-associated or retrovirus. However, baculovirus BacMam vectors provide an attractive and safe alternative. Here, a novel BacMam was constructed containing a frameshift mutation within fp25 , which results in virus stocks with higher infectious titres. This improved in vitro transduction when compared to control BacMams. Additionally, incorporating a truncated vesicular stomatitis virus G protein increased transduction efficacy and production of EGFP and BCL2 in human kidney (HK-2) and pancreatic islet β cells (EndoC βH3). Lastly, we have shown that our optimized BacMam vector can deliver and express egfp in intact pancreatic islet cells from human cadaveric donors. These results confirm that BacMam vectors are a viable choice for providing delivery of transgenes to pancreatic islet cells.

Recently, we reported the presence of distinct cell clusters named acinar-like cell clusters touching Langerhans islets with thin interstitial surrounding (ATLANTIS) in human pancreas. A morphological study in humans demonstrated that ATLANTIS and islet cell clusters are found together in the microenvironment enclosed by a common basement membrane, and ATLANTIS releases vesicles containing Regenerating gene protein (REG Iα) to islet cell clusters. We examined 1) the presence or absence of ATLANTIS in homozygous Reg I (mouse homologue of human REG Iα) deficient (Reg I -/- ) and wild-type mice, and 2) the possible role of ATLANTIS in the regeneration of beta cell clusters after encephalomyocarditis (EMC) virus (D-variant) infection in Reg I -/- and wild-type mice. ATLANTIS was found in both wild-type and Reg I -/- mice. In both groups, mean blood glucose increased transiently to greater than 14.0 mmol/L at 5 days after EMC virus infection and recovered to baseline at 12 days. At 12 days after EMC virus infection, lower BrdU labeling indices were observed in islet beta cells of Reg I -/- mice compared to wild-type mice. Beta cell volume 12 days after EMC virus infection in Reg I -/- mice did not differ from that of wild-type mice. These results suggest that Reg I, which is released from ATLANTIS to islet beta cell clusters, has a crucial role in beta cell regeneration in EMC virus-induced diabetes. The presence of mechanism(s) other than that mediated by Reg I in beta cell restoration after destruction by EMC virus was also suggested., (Copyright © 2018. Published by Elsevier Inc.)

Direct-acting antiviral agents (DAAs) have been widely used for chronic hepatitis C (CHC) treatment recently. The characteristics of glucose abnormalities after DAAs therapy however, remain elusive. We aimed to elucidate the mutual impact between treatment response and parameters of glucose abnormalities after DAAs therapy in CHC patients. CHC patients who received DAAs therapy were recruited. The primary outcome measurements were their insulin resistance (IR) and beta-cell function assessed by the homeostasis model assessment (HOMA) method before treatment and at end-of-follow-up (EOF). Sixty-five CHC patients (19 males, mean age = 59.8 ± 10.3 years) were consecutively enrolled. They included 47 (72.3%) patients of genotype-1 infection. The treatment regimens among patients were sofosbuvir in 30 patients, paritaprevir-ritonavir/ombitasvir/dasabuvir in 23 patients, and asunaprevir/daclatasvir in 12 patients respectively. The overall sustained virological response rate was 98.5%. The mean IR at EOF was 2.6 ± 1.8, which was not significantly different from baseline level (2.7 ± 2.9, P = 0.75). There was a significant improvement of beta-cell function at EOF compared to baseline (107.7 ± 86.8 to 86.7 ± 44.5, P = 0.05). The amelioration of beta-cell function at EOF was significantly observed among 23 patients of high baseline IR (166.7 ± 111.3 of baseline vs 105.7 ± 48.2 of EOF, P = 0.04). Six (60%) of the 10 pre-diabetic patients at baseline achieved a normoglycemic state at EOF. Successful eradication of HCV by DAAs might improve glucose abnormalities in CHC patients, particularly among those who had high IR., (Copyright © 2017. Published by Elsevier Taiwan.)

Metastatic cancer accounts for 90% of deaths in patients with solid tumors. There is an urgent need to better understand the drivers of cancer metastasis and to identify novel therapeutic targets. To investigate molecular events that drive the progression from primary cancer to metastasis, we have developed a bitransgenic mouse model, RIP-Tag; RIP-tva. In this mouse model, the rat insulin promoter (RIP) drives the expression of the SV40 T antigen (Tag) and the receptor for subgroup A avian leukosis virus (tva) in pancreatic β cells. The mice develop pancreatic neuroendocrine tumors with 100% penetrance through well-defined stages that are similar to human tumorigenesis, with stages including hyperplasia, angiogenesis, adenoma, and invasive carcinoma. Because RIP-Tag; RIP-tva mice do not develop metastatic disease, genetic alterations that promote metastasis can be identified easily. Somatic gene transfer into tva-expressing, proliferating pancreatic β premalignant lesions is achieved through intracardiac injection of avian retroviruses harboring the desired genetic alteration. A titer of >1 x 10 8 infectious units per ml is considered appropriate for in vivo infection. In addition, avian retroviruses can infect cell lines derived from tumors in RIP-Tag; RIP-tva mice with high efficiency. The cell lines can also be used to characterize the metastatic factors. Here we demonstrate how to utilize this mouse model and cell lines to assess the functions of candidate genes in tumor metastasis.

Metabolic disorders are common in patients with chronic hepatitis C virus (HCV) infection. Epidemiologic and clinical data indicate an overprevalence of lipids abnormalite, steatosis, insuline resistance (IR) and diabetes mellitus in HCV patients, suggesting that HCV itself may interact with glucido-lipidic metabolism. HCV interacts with the host lipid metabolism by several mechanisms leading to hepatic steatosis and hypolipidemia which are reversible after viral eradication. Liver and peripheral IR are HCV genotype/viral load dependent and improved after viral eradication. This article examines examine the relationship between HCV, lipid abnormalities, steatosis, IR, and diabetes and the pathogenic mechanisms accounting for these events in HCV-infected patients., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Context: Fulminant type 1 diabetes mellitus (T1DM) is thought to be partly caused by virus infection., Objective: This study investigated the mechanism of β cell destruction in fulminant T1DM after drug-induced hypersensitivity syndrome (DIHS)., Methods: We determined the localization of human cytomegalovirus (HCMV), human herpesvirus 6 (HHV-6), and Epstein-Barr virus (EBV) and the expression of interferon regulatory factor 3 (IRF3) and viral receptors of Z-DNA binding protein 1 (ZBP1) and retinoic acid-inducible gene I (RIG-I), together with inflammatory cells, by immunohistochemistry of the autopsy pancreas of a patient with fulminant T1DM with DIHS and in seven subjects with normal glucose tolerance who underwent pancreatectomy., Results: HCMV-positive cells were detected in islets and exocrine areas in the patient with fulminant T1DM. Greater numbers of macrophages and CD4+ and CD8+ T lymphocytes had infiltrated into HCMV-positive islets than into HCMV-negative islets, and 52.6% of HCMV-positive cells were also positive for IRF3. α Cells expressed IRF3, ZBP1, or RIG-I. No HCMV-positive cells were detected in the control subjects. HHV-6-positive, but not EBV-positive, cells were present in the patient and the control subjects., Conclusions: These findings indicate that the immunoresponse caused by HCMV infection was associated with β cell injury., (Copyright © 2017 Endocrine Society)

In an earlier study, infection of human pancreatic islets with epidemic strains of echovirus (E4, E16, E30), with proven but differently ability to induce islet autoimmunity, resulted either in a severe damage (i.e., E16 and E30) or proceeded without visible changes in infected islets (i.e., E4). In this study, the ability of these strains to replicate in beta cells and the consequence of such an infection for beta cell lysis and beta cell function was studied in the pancreatic beta cell lines INS-1, MIN6, and NIT-1. The strains of E16 and E30 did replicate in INS1, MIN6, and NIT1 cells and resulted in a pronounced cytopathic effect within 3 days following infection. By contrast, E4 replicated in all examined insulinoma cells with no apparent cell destruction. The insulin release in response to high glucose stimulation was hampered in all infected cells (P < 0.05) when no evidence of cytolysis was present; however, the adverse effect of E16 and E30 on insulin secretion appeared to be higher than that of the E4 strain. The differential effects of echovirus infection on cell lysis, and beta cell function in the rodent insulinoma INS1, MIN6, and NIT 1 cells reflect those previously obtained in primary human islets and support the notion that the insulin-producing beta cells can harbor a non-cytopathic viral infection., (© 2015 Wiley Periodicals, Inc.)

Derailment of immune responses can lead to autoimmune type 1 diabetes, and this can be accelerated or even induced by local stress caused by inflammation or infection. Dendritic cells (DCs) shape both innate and adaptive immune responses. Here, we report on the responses of naturally occurring human myeloid BDCA1(+) DCs towards differentially stressed pancreatic β cells. Our data show that BDCA1(+) DCs in human pancreas-draining lymph node (pdLN) suspensions and blood-derived BDCA1(+) DCs both effectively engulf β cells, thus mimicking physiological conditions. Upon uptake of enterovirus-infected, but not mock-infected cells, BDCA1(+) DCs induced interferon (IFN)-α/β responses, co-stimulatory molecules and proinflammatory cytokines and chemokines. Notably, induction of stress in β cells by ultraviolet irradiation, culture in serum-free medium or cytokine-induced stress did not provoke strong DC activation, despite efficient phagocytosis. DC activation correlated with the amount of virus used to infect β cells and required RNA within virally infected cells. DCs encountering enterovirus-infected β cells, but not those incubated with mock-infected or stressed β cells, suppressed T helper type 2 (Th2) cytokines and variably induced IFN-γ in allogeneic mixed lymphocyte reaction (MLR). Thus, stressed β cells have little effect on human BDCA1(+) DC activation and function, while enterovirus-infected β cells impact these cells significantly, which could help to explain their role in development of autoimmune diabetes in individuals at risk., (© 2016 British Society for Immunology.)

Extensive research has identified enterovirus (EV) infections as key environmental triggers of type 1 diabetes. However, the underlying molecular mechanisms via which EVs contribute to the pathogenesis of type 1 diabetes remain unclear. Given that EVs dysregulate host microRNAs (miRNAs), which function as key regulators of β-cell biology, we investigated the impact of coxsackievirus B5 (CVB5) infection on the cellular expression of miRNAs within human islets. Using high-throughput quantitative PCR nanofluidics arrays, the expression of 754 miRNAs was examined in CVB5-infected human pancreatic islets. In total, 33 miRNAs were significantly dysregulated (≥ threefold difference) in the infected compared with control islets (P < 0.05). Subsequently, these differentially expressed miRNAs were predicted to target mRNAs of 57 known type 1 diabetes risk genes that collectively mediate various biological processes, including the regulation of cell proliferation, cytokine production, the innate immune response, and apoptosis. In conclusion, we report the first global miRNA expression profiling of CVB5-infected human pancreatic islets. We propose that EVs disrupt the miRNA-directed suppression of proinflammatory factors within β-cells, thereby resulting in an exacerbated antiviral immune response that promotes β-cell destruction and eventual type 1 diabetes., (© 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

It has been reported that endogenous retroviruses can contaminate human cell lines that have been passaged as xenotransplants in immunocompromised mice. We previously developed and described 2 human pancreatic β cell lines (EndoC-βH1 and EndoC-βH2) that were generated in this way. Here, we have shown that B10 xenotropic virus 1 (Bxv1), a xenotropic endogenous murine leukemia virus (MuLV), is present in these 2 recently described cell lines. We determined that Bxv1 was also present in SCID mice that were used for in vivo propagation of EndoC-βH1/2 cells, suggesting that contamination occurred during xenotransplantation. EndoC-βH1/2 cells released Bxv1 particles that propagated to human 293T and Mus dunni cells. Mobilization assays demonstrated that Bxv1 transcomplements defective MuLV-based retrovectors. In contrast, common rodent β cell lines, rat INS-1E and RIN-5F cells and mouse MIN6 and βTC3 cells, displayed either no or extremely weak xenotropic helper activity toward MuLV-based retrovectors, although xenotropic retrovirus sequences and transcripts were detected in both mouse cell lines. Bxv1 propagation from EndoC-βH1/2 to 293T cells occurred only under optimized conditions and was overall poorly efficient. Thus, although our data imply that MuLV-based retrovectors should be cautiously used in EndoC-βH1/2 cells, our results indicate that an involuntary propagation of Bxv1 from these cells can be easily avoided with good laboratory practices.

Type 1 diabetes (T1D) is an autoimmune disease caused by loss of pancreatic β cells via apoptosis while neighboring α cells are preserved. Viral infections by coxsackieviruses (CVB) may contribute to trigger autoimmunity in T1D. Cellular permissiveness to viral infection is modulated by innate antiviral responses, which vary among different cell types. We presently describe that global gene expression is similar in cytokine-treated and virus-infected human islet cells, with up-regulation of gene networks involved in cell autonomous immune responses. Comparison between the responses of rat pancreatic α and β cells to infection by CVB5 and 4 indicate that α cells trigger a more efficient antiviral response than β cells, including higher basal and induced expression of STAT1-regulated genes, and are thus better able to clear viral infections than β cells. These differences may explain why pancreatic β cells, but not α cells, are targeted by an autoimmune response during T1D.

Considerable evidence implies that an enteroviral infection may accelerate or precipitate type 1 diabetes (T1D) in some individuals. However, causality is not proven. We present and critically assess evidence suggesting that islet β cells can become infected with enterovirus, and argue that this may result in one of several consequences. Occasionally, a fully lytic infection may arise and this culminates in fulminant diabetes. Alternatively, an atypical persistent infection develops which can be either benign or promote islet autoimmunity. We propose a model in which the 'strength' of the β cell response to the establishment of a persistent enteroviral infection determines the final disease outcome., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Beyond acute clinical conditions, the role of enteroviruses (EVs) in chronic human diseases has been described. Although they are considered as highly cytolytic viruses, EVs can persist in various tissues. The persistence is believed to play a major role in the pathogenesis of EV related chronic diseases such as type 1 diabetes (T1D). T1D is characterized by an autoimmune destruction of pancreatic beta cells, and results from interplay between a genetic predisposition, the immune system, and environmental factors. EVs and especially group B coxsackieviruses (CVB) have been the most incriminated as exogenous agents involved in the development of T1D. Enteroviral persistence is the result of a virus-host coevolution combining a cell resistance to lysis through mutations or down-regulation of viral receptor, and a decrease of the viral replication by genomic modifications or the production of a stable double-stranded RNA form. CVB can persist in pancreatic cells and therefore could trigger, in genetically predisposed individuals, the autoimmune destruction of beta cells mainly through an activation of inflammation. The persistence of the virus in other tissues such as intestine, blood cells, and thymus has been described, and could also contribute to some extent to the enteroviral pathogenesis of T1D. The molecular and cellular mechanisms of CVB persistence and the link with the development of T1D should be investigated further.

Purpose of Review: Type 1 diabetes (T1D) results from the immune-mediated destruction of pancreatic insulin-producing cells because of the interaction among genetic susceptibility, the immune system and environmental factor(s). A possible role of viral infections in T1D pathogenesis has been hypothesized for some time; however, only in the most recent years, studies performed at the molecular and cellular level are starting to shed light on this issue., Recent Findings: Studies in animal models and in man have shown that viruses can indeed infect pancreatic beta-cells, inducing islet inflammation and functional damage. In addition, recent in-situ investigations performed on pancreatic tissue samples have provided evidence that in addition to adaptive immune response, innate immunity is involved in T1D pathogenesis and the whole pancreas (not only its endocrine portion) is infiltrated by immune-mediated phenomena., Summary: The established role of inflammation in the insulitic process and the increasing evidence in support of the contribution of viral infections to a proinflammatory islet scenario are strongly suggestive that viruses may indeed contribute to beta-cell damage and dysfunction, thus setting the stage for the design of antiviral strategies (e.g. vaccines and antiviral drugs) aimed at protecting the beta-cells.

In vitro studies with primary human pancreatic islets suggest that several enterovirus serotypes are able to infect and replicate in beta cells. Some enterovirus strains are highly cytolytic in vitro whereas others show virus replication with no apparent islet destruction. The capability to induce islet destruction is determined only partially by the virus serotype, since strain specific differences have been detected within some serotypes including echovirus 9 (E-9). In this study, the viral genetic factors determining the outcome of islet infection (i.e., destructive vs. benign) were investigated by constructing parallel infectious clones of lytic E-9-DM strain that was isolated from a small child at the clinical onset of type 1 diabetes. The capabilities of these clone-derived viruses to induce islet destruction were monitored and the lytic potential of clones was modified by site-directed mutagenesis. The lytic capabilities of these clone-derived viruses in human pancreatic islets were modified by a single amino acid substitution (T81A) in the capsid protein VP1. The data presented outline the importance of amino acid point mutations in the pathogenetic process leading to islet necrosis. However, although the amino acid substitution (T81A) modifies the lytic capabilities of E-9-DM strain-derived microvariant strains, it is likely that additional viral genetic determinants of pancreatic islet pathogenicity exist in other E-9 strains., (Copyright © 2013 Wiley Periodicals, Inc.)

Autoimmune destruction of insulin producing pancreatic β-cells is the hallmark of type I diabetes. One of the key molecules implicated in the disease onset is the immunoproteasome, a protease with multiple proteolytic sites that collaborates with the constitutive 19S and the inducible 11S (PA28) activators to produce immunogenic peptides for presentation by MHC class I molecules. Despite its importance, little is known about the function and regulation of the immunoproteasome in pancreatic β-cells. Of special interest to immunoproteasome activation in β-cells are the effects of IFNβ, a type I IFN secreted by virus-infected cells and implicated in type I diabetes onset, compared to IFNγ, the classic immunoproteasome inducer secreted by cells of the immune system. By qPCR analysis, we show that mouse insulinoma MIN6 cells and mouse islets accumulate the immune proteolytic β1(i), β2(i) and β5(i), and 11S mRNAs upon exposure to IFNβ or IFNγ. Higher concentrations of IFNβ than IFNγ are needed for similar expression, but in each case the expression is transient, with maximal mRNA accumulation in 12 hours, and depends primarily on Interferon Regulatory Factor 1. IFNs do not alter expression of regular proteasome genes, and in the time frame of IFNβ-mediated response, the immune and regular proteolytic subunits co-exist in the 20S particles. In cell extracts with ATP, these particles have normal peptidase activities and degrade polyubiquitinated proteins with rates typical of the regular proteasome, implicating normal regulation by the 19S activator. However, ATP depletion rapidly stimulates the catalytic rates in a manner consistent with levels of the 11S activator. These findings suggest that stochastic combination of regular and immune proteolytic subunits may increase the probability with which unique immunogenic peptides are produced in pancreatic β-cells exposed to IFNβ, but primarily in cells with reduced ATP levels that stimulate the 11S participation in immunoproteasome function.

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.

A possible etiologic role of enteroviruses for type 1 diabetes has been researched for 40 years, but evidence to date is inconclusive. This article summarizes new evidence from Cuban research supporting a role for enteroviruses, both in preclinical stages of autoimmune reactions against pancreatic β cells and at clinical onset, in a population with low type 1 diabetes incidence. Possible pathogenetic mechanisms are also discussed, such as acute cytolytic damage and molecular mimicry. Although direct causal effects of enteroviruses in type 1 diabetes are difficult to demonstrate, arguments supporting their role in type 1 diabetes pathogenesis should not be ignored; and confirmation could contribute to development of more effective preventive strategies.

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