Several different enterovirus serotypes can be associated with prediabetic autoimmune episodes and onset of overt IDDM. Childhood Diabetes in Finland (DiMe) Study Group

Clostridia and Enteroviruses as Synergistic Triggers of Type 1 Diabetes Mellitus

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

Coxsackievirus B Vaccines Prevent Infection-Accelerated Diabetes in NOD Mice and Have No Disease-Inducing Effect

Enteroviruses, including the Coxsackievirus Bs (CVB), have been implicated as causal agents in human type 1 diabetes. Immunization of at-risk individuals with a CVB vaccine provides an attractive strategy for elucidating the role of CVBs in the disease etiology. Previously, we have shown that an inactivated whole-virus vaccine covering all CVB serotypes (CVB1-6) is safe to administer and highly immunogenic in preclinical models, including nonhuman primates. Before initiating clinical trials with this type of vaccine, it was also important to address 1) whether the vaccine itself induces adverse immune reactions, including accelerating diabetes onset in a diabetes-prone host, and 2) whether the vaccine can prevent CVB-induced diabetes in a well-established disease model. Here, we present results from studies in which female NOD mice were left untreated, mock-vaccinated, or vaccinated with CVB1-6 vaccine and monitored for insulitis occurrence or diabetes development. We demonstrate that vaccination induces virus-neutralizing antibodies without altering insulitis scores or the onset of diabetes. We also show that NOD mice vaccinated with a CVB1 vaccine are protected from CVB-induced accelerated disease onset. Taken together, these studies show that CVB vaccines do not alter islet inflammation or accelerate disease progression in an animal model that spontaneously develops autoimmune type 1 diabetes. However, they can prevent CVB-mediated disease progression in the same model.

Association of different enteroviruses with atopy and allergic diseases in early childhood

BACKGROUND

Enterovirus (EV) infections, being among the most prevalent viruses worldwide, have been associated with reduced risk of allergic diseases. We sought to determine the association between EVs and allergic sensitization and disease in early childhood.

METHODS

The study was carried out in a nested case-control setting within a prospective birth cohort in Finland. We included 138 case children who had specific IgE (s-IgE) sensitization at the age of 5 years and 138 control children without s-IgE sensitization. Allergic disease was recorded at study visits and identified with the ISAAC questionnaire. We screened for the presence of serotype-specific antibodies against 41 EVs at 1-5 years of age and assessed their association with allergic sensitization and disease.

RESULTS

The overall number of EV infections did not differ between s-IgE-sensitized children and non-sensitized control children. However, there was a tendency of case children with an allergic disease having less EV infections than their controls. This observation was statistically significant for species A EVs in case children with atopic dermatitis vs. control children: OR 0.6 (95% CI 0.36-0.99), p = .048.

CONCLUSION

This study supports the evidence that EV exposure and development of allergic disease are inversely associated. Interestingly, the inverse association was not observed for bare atopic IgE sensitization, but for IgE sensitization coupled with clinical atopic disease. This suggests that environmental factors influencing IgE sensitization may differ from those influencing progression to clinical allergic disease.

Increased Incidence of Pediatric Type 1 Diabetes With Novel Association With Coxsackievirus A Species in Young Children but Declined Incidence in Adolescents in Taiwan

OBJECTIVE

Type 1 diabetes (T1D) has been linked to enterovirus infection in small population-based epidemiological studies. We investigated the secular relationship of T1D incidence with enterovirus infection and enterovirus species using nationwide population-based analysis.

RESEARCH DESIGN AND METHODS

We accessed the National Health Insurance Research Database of Taiwan to identify T1D and enterovirus infection cases from 2001 to 2015. Enterovirus serotype isolation rates were obtained from the nationwide laboratory surveillance systems. Negative binomial regression models assessed the incidence trend, and extended Cox proportional hazards models analyzed the association of enterovirus infection with T1D incidence. Spearman correlation coefficients evaluated the correlation between T1D incidence and circulating enterovirus species.

RESULTS

T1D incidence rates in youth younger than 20 years were 6.30 and 5.02 per 100,000 person-years in 2001 and 2015 (P = 0.287), respectively. T1D incidence increased significantly in children aged 0-6 years (P < 0.001) but decreased in adolescents aged 13-19 years (P = 0.011). The T1D risk in children aged 0-6 years with enterovirus infection was significantly higher than that in noninfected subjects (hazard ratio 1.46; 95% CI 1.35-1.58; P < 0.001). Additionally, TID incidence in children aged 0-6 years was significantly correlated with the isolation rates of coxsackievirus A species (r = 0.60; P = 0.017), but no association was found beyond the age of 7.

CONCLUSIONS

We demonstrated that T1D incidence increased in children aged 0-6 years but decreased in adolescents aged 13-19 years in Taiwan. Enterovirus-infected subjects younger than 7 years had a higher risk of T1D than noninfected subjects.

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

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

GRP78: A cell's response to stress

Background

Glucose-Regulated Protein 78 (GRP78) is a chaperone heat shock protein that has been intensely studied in the last two decades. GRP78 is the master of the unfolded protein response (UBR) in the Endoplasmic Reticulum (ER) in normal cells. GRP78 force the unfolded proteins to refold or degrade using cellular degradation mechanisms.

Scope

Under stress, the overexpression of GRP78 on the cell membrane mediates the vast amount of disordered proteins. Unfortunately, this makes it a tool for pathogens (bacterial, fungal and viral) to enter the cell and to start different pathways leading to pathogenesis. Additionally, GRP78 is overexpressed on the membranes of various cancer cells and increase the aggressiveness of the disease.

Major conclusions

The current review summarizes structure, function, and different mechanisms GRP78 mediate in response to normal or stress conditions.

General significance

GRP78 targeting and possible inhibition mechanisms are also covered in the present review aiming to prevent the virulence of pathogens and cancer.

Human enteroviruses associated with and without diarrhea in Thailand between 2010 and 2016

Non-bacterial acute gastroenteritis (AGE) associated with virus infection affects individuals living in developing countries, especially children. To investigate whether shedding of certain human enterovirus (EV) is more frequently detected in the stool of individuals with AGE of unknown etiology than individuals without AGE symptoms, we tested fecal samples collected from 2,692 individuals with diarrhea between January 2010 and December 2016. Samples were tested for rotavirus, norovirus, and EV by reverse-transcription polymerase chain reaction (RT-PCR) and adenovirus by PCR. EV-positive samples were subjected to sequencing and phylogenetic analysis to identify EV species and types. Findings were compared to EV found in 1,310 fecal samples from individuals without AGE who were diagnosed with hand, foot, and mouth disease (HFMD). While the majority of viruses identified in AGE consisted of human rotavirus (22.7%), norovirus (11.4%) and adenovirus (9.3%), we identified EV (6.2%) belonging mainly to species B, C, and rhinovirus. In contrast, >92% of EV found without AGE symptoms belonged to species A. Although AGE symptoms are not often attributed to EV infection, EV was associated with diarrhea of unknown etiology at least in 3.4% of AGE cases. While CV-A6 was most likely to be found in stools of HFMD patients, rhinovirus A and C were the two most common EV species associated with AGE. Elucidating group-specific EV infection in diseases with and without AGE will be useful in assisting identification, clinical management, and the surveillance of EV infection in the community.

Detection of enteroviruses in stools precedes islet autoimmunity by several months: possible evidence for slowly operating mechanisms in virus-induced autoimmunity

AIMS/HYPOTHESIS

This case-control study was nested in a prospective birth cohort to evaluate whether the presence of enteroviruses in stools was associated with the appearance of islet autoimmunity in the Type 1 Diabetes Prediction and Prevention study in Finland.

METHODS

Altogether, 1673 longitudinal stool samples from 129 case children who turned positive for multiple islet autoantibodies and 3108 stool samples from 282 matched control children were screened for the presence of enterovirus RNA using RT-PCR. Viral genotype was detected by sequencing.

RESULTS

Case children had more enterovirus infections than control children (0.8 vs 0.6 infections per child). Time-dependent analysis indicated that this excess of infections occurred more than 1 year before the first detection of islet autoantibodies (6.3 vs 2.1 infections per 10 follow-up years). No such difference was seen in infections occurring less than 1 year before islet autoantibody seroconversion or after seroconversion. The most frequent enterovirus types included coxsackievirus A4 (28% of genotyped viruses), coxsackievirus A2 (14%) and coxsackievirus A16 (11%).

CONCLUSIONS/INTERPRETATION

The results suggest that enterovirus infections diagnosed by detecting viral RNA in stools are associated with the development of islet autoimmunity with a time lag of several months.

Incomplete immune response to coxsackie B viruses associates with early autoimmunity against insulin

Viral infections are associated with autoimmunity in type 1 diabetes. Here, we asked whether this association could be explained by variations in host immune response to a putative type 1 etiological factor, namely coxsackie B viruses (CVB). Heterogeneous antibody responses were observed against CVB capsid proteins. Heterogeneity was largely defined by different binding to VP1 or VP2. Antibody responses that were anti-VP2 competent but anti-VP1 deficient were unable to neutralize CVB, and were characteristic of children who developed early insulin-targeting autoimmunity, suggesting an impaired ability to clear CVB in early childhood. In contrast, children who developed a GAD-targeting autoimmunity had robust VP1 and VP2 antibody responses to CVB. We further found that 20% of memory CD4⁺ T cells responding to the GAD65_247-266 peptide share identical T cell receptors to T cells responding to the CVB4 p2C_30-51 peptide, thereby providing direct evidence for the potential of molecular mimicry as a mechanism for GAD autoimmunity. Here, we highlight functional immune response differences between children who develop insulin-targeting and GAD-targeting autoimmunity, and suggest that children who lose B cell tolerance to insulin within the first years of life have a paradoxical impaired ability to mount humoral immune responses to coxsackie viruses.

Enterovirus infection is associated with an increased risk of childhood type 1 diabetes in Taiwan: a nationwide population-based cohort study

AIMS/HYPOTHESIS

This study compared the incidence rate of type 1 diabetes in children diagnosed with enterovirus (EV) infections with that in age- and sex-matched children without EV infection in a population-based cohort. In addition, we examined whether the direction or magnitude of the association between EV infection and type 1 diabetes differs according to atopic disease status in children.

METHODS

We used insurance claims data from Taiwan's National Health Insurance Research Database to derive type 1 diabetes incidence in children aged up to 18 years with or without a diagnosis of EV infection during 2000-2008. Incidence rate ratios and HRs of type 1 diabetes for EV infection were estimated by Poisson regression and Cox's proportional hazard regression model.

RESULTS

Overall incidence of type 1 diabetes was higher in the EV than in the non-EV infection cohort (5.73 vs 3.89 per 100,000 person-years; incidence rate ratio 1.48 [95% CI 1.19, 1.83]), with an adjusted HR of 1.48 (95% CI 1.19, 1.83). Among children without EV, incidence increased with age at diagnosis of EV infection, except in those aged 5-10 years. The HRs of type 1 diabetes in children with allergic rhinitis, bronchial asthma or either one of these atopic diseases showed more variation than in those children without these diseases.

CONCLUSIONS/INTERPRETATION

This nationwide retrospective cohort study found a positive correlation between type 1 diabetes and EV infection. The results suggest that a preventive strategy, such as an effective vaccine against EV infection, may lessen the incidence of type 1 diabetes in Taiwan.

Enteroviruses, hygiene and type 1 diabetes: toward a preventive vaccine

Enteroviruses and humans have long co-existed. Although recognized in ancient times, poliomyelitis and type 1 diabetes (T1D) were exceptionally rare and not epidemic, due in large part to poor sanitation and personal hygiene which resulted in repeated exposure to fecal-oral transmitted viruses and other infectious agents and viruses and the generation of a broad protective immunity. As a function of a growing acceptance of the benefits of hygienic practices and microbiologically clean(er) water supplies, the likelihood of exposure to diverse infectious agents and viruses declined. The effort to vaccinate against poliomyelitis demonstrated that enteroviral diseases are preventable by vaccination and led to understanding how to successfully attenuate enteroviruses. Type 1 diabetes onset has been convincingly linked to infection by numerous enteroviruses including the group B coxsackieviruses (CVB), while studies of CVB infections in NOD mice have demonstrated not only a clear link between disease onset but an ability to reduce the incidence of T1D as well: CVB infections can suppress naturally occurring autoimmune T1D. We propose here that if we can harness and develop the capacity to use attenuated enteroviral strains to induce regulatory T cell populations in the host through vaccination, then a vaccine could be considered that should function to protect against both autoimmune as well as virus-triggered T1D. Such a vaccine would not only specifically protect from certain enterovirus types but more importantly, also reset the organism's regulatory rheostat making the further development of pathogenic autoimmunity less likely.

Coxsackievirus B1 is associated with induction of β-cell autoimmunity that portends type 1 diabetes

The rapidly increasing incidence of type 1 diabetes implies that environmental factors are involved in the pathogenesis. Enteroviruses are among the suspected environmental triggers of the disease, and the interest in exploring the possibilities to develop vaccines against these viruses has increased. Our objective was to identify enterovirus serotypes that could be involved in the initiation of the disease process by screening neutralizing antibodies against 41 different enterovirus types in a unique longitudinal sample series from a large prospective birth-cohort study. The study participants comprised 183 case children testing persistently positive for at least two diabetes-predictive autoantibodies and 366 autoantibody-negative matched control children. Coxsackievirus B1 was associated with an increased risk of β-cell autoimmunity. This risk was strongest when infection occurred a few months before autoantibodies appeared and was attenuated by the presence of maternal antibodies against the virus. Two other coxsackieviruses, B3 and B6, were associated with a reduced risk, with an interaction pattern, suggesting immunological cross-protection against coxsackievirus B1. These results support previous observations suggesting that the group B coxsackieviruses are associated with the risk of type 1 diabetes. The clustering of the risk and protective viruses to this narrow phylogenetic lineage supports the biological plausibility of this phenomenon.

Viruses and type 1 diabetes: a new look at an old story

Epidemiological data suggesting an infectious origin of diabetes pre-date the discovery of insulin; indeed it was the variation in mortality rates from diabetes that led Gunderson to hypothesise that a virus with 'selective affinity for the pancreas' may cause 'acute diabetes' in youth (1). He noted an increase in deaths from diabetes in young people aged 10-20 yr in Norway from 1900 to 1921 following epidemics of parotitis, with a lag time of 3-4 yr between infection and death. In Norway, Denmark,France, and America, the increase in deaths from diabetes exceeded the expected number based on population growth; lending further weight to the proposal that diabetes was caused by infection. Since that time,a large body of epidemiological, clinical and experimental research, in humans, cellular and animal models, has provided further insights into the contribution of infections in the development of type 1 diabetes.Epidemiological evidence for a viral aetiology of diabetes A substantial body of epidemiological data point to a significant contribution of the environment in the development of type 1 diabetes,although much of the evidence is not specific to viruses per se. These data include rising rates of type 1 diabetes in both developed and developing countries in recent decades (2, 3) and a reduced contribution of high risk human leucocyte antigen (HLA) genotypes (4, 5), indicating that non-genetic factors are important. Similarly, the pairwise concordance between monozygotic twins for type 1 diabetes of less than 40%, and the observation that the incidence of diabetes in migrant children reflects that of their adopted country (6, 7), provide circumstantial evidence that environmental agents contribute to the disease. Space-time clustering in the presentation of type 1 diabetes (8-10) and clustering of births in children who subsequently develop diabetes (11) support a direct role for infections in the initiation and acceleration of the disease process.

Structural and functional analysis of coxsackievirus A9 integrin αvβ6 binding and uncoating

Coxsackievirus A9 (CVA9) is an important pathogen of the Picornaviridae family. It utilizes cellular receptors from the integrin αv family for binding to its host cells prior to entry and genome release. Among the integrins tested, it has the highest affinity for αvβ6, which recognizes the arginine-glycine-aspartic acid (RGD) loop present on the C terminus of viral capsid protein, VP1. As the atomic model of CVA9 lacks the RGD loop, we used surface plasmon resonance, electron cryo-microscopy, and image reconstruction to characterize the capsid-integrin interactions and the conformational changes on genome release. We show that the integrin binds to the capsid with nanomolar affinity and that the binding of integrin to the virion does not induce uncoating, thereby implying that further steps are required for release of the genome. Electron cryo-tomography and single-particle image reconstruction revealed variation in the number and conformation of the integrins bound to the capsid, with the integrin footprint mapping close to the predicted site for the exposed RGD loop on VP1. Comparison of empty and RNA-filled capsid reconstructions showed that the capsid undergoes conformational changes when the genome is released, so that the RNA-capsid interactions in the N termini of VP1 and VP4 are lost, VP4 is removed, and the capsid becomes more porous, as has been reported for poliovirus 1, human rhinovirus 2, enterovirus 71, and coxsackievirus A7. These results are important for understanding the structural basis of integrin binding to CVA9 and the molecular events leading to CVA9 cell entry and uncoating.

Early human enterovirus infections in healthy Swedish children participating in the PRODIA pilot study

Human enteroviruses (HEV) are common, especially in childhood and during the enterovirus season, causing mainly asymptomatic infections but also mild and severe illnesses. Numerous studies have shown the association between HEV infections and type 1 diabetes. Here, the prevalence of HEV infections was studied in healthy Swedish children with increased HLA-associated risk for type 1 diabetes participating in the PRODIA pilot study in which children were randomized to receive probiotics or placebo during the first 6 months of life. Stool specimens collected from 197 children in every 3 months from the age of 3 to 24 months were screened for HEV using traditional viral culturing method and identified with reverse transcriptase polymerase chain reaction (RT-PCR) and sequencing of the partial VP1 coding part of the viral genome. Altogether 4.8% (52/1,094) of the specimens were HEV-positive and 22.3% (44/197) of the children excreted HEV during the follow-up. HEV-A and HEV-B were present in 2.1 and 2.7% of the specimens, respectively. HEV-C and HEV-D viruses were not detected. In total, 17 different HEV serotypes were detected and the most common findings were CV-A9 (13.5%), CV-A16 (11.5%), and CV-A2 (9.6%). The majority of the infections (92.3%) were during the enterovirus season extending from July to December. Probiotic treatment did not affect significantly the risk of HEV infections during the 2-year follow-up although a trend for transient decrease for HEV positivity (HEV-A and/or HEV-B) by the age of 12 months was observed in children who received probiotics [OR 0.40; 95% confidence interval 0.15 to 1.08; P-value 0.071, generalized estimating (GEE) analysis]. According to the results, HEV-A findings were nearly as common as HEV-B findings among the healthy children participating in this study. Also it was shown that serotypes belonging to HEV-A species can be detected by means of viral culturing.

Role of enterovirus infections in IgE sensitization

Among other infectious agents, enteroviruses have been associated with protection against allergic diseases. The aim of the present study was to confirm these findings using a highly sensitive and specific neutralization antibody assay and to investigate whether the protective effect is related to certain enterovirus serotypes. Antibodies against 12 enterovirus serotypes were measured in 60 children who were positive for allergen-specific IgE and in 190 control children. Echoviruses seemed to be more protective than coxsackie-B-viruses and echovirus 11 had the strongest independent protective effect (P = 0.001; OR = 0.35, 95% CI: 0.18-0.67). The results support previous observations suggesting that infections by certain enterovirus types are associated with protection against IgE sensitization.

Interaction of enterovirus infection and cow's milk-based formula nutrition in type 1 diabetes-associated autoimmunity

BACKGROUND

Enteral virus infections and early introduction of cow's milk (CM)-based formula are among the suggested triggers of type 1 diabetes (T1D)-associated autoimmunity, although studies on their role have remained contradictory. Here, we aimed to analyse whether interactions between these factors might clarify the controversies.

MATERIALS

The study population comprised 107 subjects developing positivity for at least two T1D-associated autoantibodies and 446 control subjects from the Finnish diabetes prediction and prevention cohort. Enterovirus, rotavirus, adenovirus, respiratory syncytial virus and bovine insulin-binding antibodies were analysed from prospective serum samples at 3-24 months of age. Data on infant cow's milk exposure were available for 472 subjects: 251 subjects were exposed to cow's milk before 3 months of age and 221 subjects later in infancy.

RESULTS

Signs of an enterovirus infection by 12 months of age were associated with the appearance of autoimmunity among children who were exposed to cow's milk before 3 months of age. Cox regression analysis revealed a combined effect of enterovirus infection and early cow's milk exposure for the development of ICA and any of the biochemically defined autoantibodies (p = 0.001), of IAA (p = 0.002), GADA (p = 0.001) and IA-2A (p = 0.013).

CONCLUSIONS

The effect of enterovirus infection on the appearance of T1D-associated autoimmunity seems to be modified by exposure to cow's milk in early infancy suggesting an interaction between these factors. Moreover, these results provide an explanation for the controversial findings obtained when analysing the effect of any single one of these factors on the appearance of T1D-associated autoimmunity.

Human enterovirus infections in children at increased risk for type 1 diabetes: the Babydiet study

AIMS/HYPOTHESIS

The aim of this study was to examine human enteroviruses (HEVs) and other intestinal viruses derived from children who participated in the Babydiet intervention study and to analyse the findings according to the appearance of islet autoantibodies, dietary intervention, maternal type 1 diabetes and clinical symptoms.

METHODS

In the Babydiet study the influence of first gluten exposure (6 or 12 months) on the development of islet autoimmunity was investigated in 150 children with increased genetic and familial risk for type 1 diabetes. Blood and stool samples were collected at 3 monthly intervals until the age of 3 years and yearly thereafter. Infections and clinical symptoms were recorded daily for the first year. In the present study, 339 stool samples collected from 104 children during the first year of life were analysed for HEVs and a certain proportion of the samples were analysed for other intestinal viruses.

RESULTS

HEV was detected in 32 (9.4%) samples from 24 (23.1%) children. Altogether 13 serotypes were identified, with HEV-A species being the most common. Children with gastrointestinal symptoms had norovirus (3/11) and sapovirus (1/11) infections in addition to HEV (1/11). Of the 104 children, 22 developed islet autoantibodies. HEV infections were detected in 18% (4/22) and 24% (20/82) of islet-autoantibody-positive and -negative children, respectively (p = 0.5). The prevalence of HEV was similar in the gluten-exposed groups and in children from mothers with type 1 diabetes or from affected fathers and/or siblings (p = 1.0 and 0.6, respectively).

CONCLUSIONS/INTERPRETATION

No correlation was found between the presence of HEV in the first year of life and the development of islet autoantibodies. There was no association between HEV infections and dietary intervention, maternal diabetes or clinical symptoms.

Coxsackievirus B3-induced cellular protrusions: structural characteristics and functional competence

Virus-induced alterations in cell morphology play important roles in the viral life cycle. To examine the intracellular events of coxsackievirus B3 (CVB3) infection, green monkey kidney (GMK) cells were either inoculated with the virus or transfected with the viral RNA. Various microscopic and flow cytometric approaches demonstrated the emergence of CVB3 capsid proteins at 8 h posttransfection, followed by morphological transformation of the cells. The morphological changes included formation of membranous protrusions containing viral capsids, together with microtubules and actin. Translocation of viral capsids into these protrusions was sensitive to cytochalasin D, suggesting the importance of actin in the process. Three-dimensional (3D) live-cell imaging demonstrated frequent contacts between cellular protrusions and adjacent cells. Markedly, in spite of an increase in the cellular viral protein content starting 8 h postinfection, no significant decrease in cell viability or increase in the amount of early apoptotic markers was observed by flow cytometry by 28 h postinfection. Comicroinjection of viral RNA and fluorescent dextran in the presence of neutralizing virus antibody suggested that these protrusions mediated the spread of infection from one cell to another prior to virus-induced cell lysis. Altogether, the CVB3-induced cellular protrusions could function as a hitherto-unknown nonlytic mechanism of cell-to-cell transmission exploited by enteroviruses.

Enterovirus infection induces cytokine and chemokine expression in insulin-producing cells

Despite evidence supporting an association between enterovirus (EV) infection and type 1 diabetes, the etiological mechanism(s) for EV-induced beta cell destruction is(are) not well understood. In this study, the effects of Coxsackievirus B (CVB) 1-6 on cell lysis and cytokine/chemokine expression in the insulinoma-1 (INS-1) beta cell line were investigated. Cytolysis was assessed using tissue culture infectious dose 50 (TCID(50)). Quantitative RT-PCR was used to measure viral RNA and mRNA of cytokines interferon (IFN)-α, IFN-β, IFN-γ, tumor necrosis factor (TNF)-α, and chemokine (C-X-C motif) ligand 10 (CXCL10), chemokine (C-C motif) ligand 2 (CCL2), and chemokine (C-C motif) ligand 5 (CCL5) in infected INS-1 cells. CVB2, 4, 5, and 6 lysed and replicated in INS-1 cells; TCID(50) was lowest for CVB5 and highest for CVB6. IFN-γ, CXCL10, and CCL5 mRNA levels all increased significantly following infection with CVB2, 4, 5, and 6 (P<0.05). CCL2 mRNA increased with CVB2, 5, and 6 (P<0.05), IFN-α mRNA increased with CVB5 infection (P<0.05), while TNF-α mRNA and IFN-β mRNA (P<0.001) increased with CVB2 infection. Dose-dependent effects of infection on cytokine mRNA levels were observed for all (P<0.01) except IFN-γ. Following inoculation of INS-1 cells with CVB1 and 3, viral RNA was not detected and cytokine/chemokine mRNA levels were unchanged. In conclusion, CVB2, 4, 5, and 6 induce dose-dependent cytokine and chemokine mRNA production from INS-1 cells suggesting that pro-inflammatory cytokine and chemokine secretion by beta cells is a potential mechanism for EV-induced beta cell damage in type 1 diabetes.

Murine pancreatic beta TC3 cells show greater 2', 5'-oligoadenylate synthetase (2'5'AS) antiviral enzyme activity and apoptosis following IFN-alpha or poly(I:C) treatment than pancreatic alpha TC3 cells

Type 1 diabetes is caused by autoimmune destruction of pancreatic beta cells, possibly virus initiated. Virus infection induces alpha-interferon (IFN-α), leading to upregulation of genes encoding double-stranded (ds) RNA-dependent antiviral enzymes 2′, 5′-oligoadenylate synthetase (2′5′AS) and PKR (p68). To investigate whether beta cell specificity could be due to antiviral differences between beta and alpha cells, we treated beta and alpha TC3 cell lines with IFN-α and/or poly(I:C) (a synthetic dsRNA). Results showed that, following IFN-α stimulation, increases in 2′5′AS levels and activities were significantly higher in beta than alpha cells (P < .001), whereas increases in PKR level and activity were comparable in the two cell types. Poly(I:C) stimulated 2′5′AS activity in beta but not alpha cells, and co-transfection IFN-α plus poly(I:C) induced apoptosis in beta but not alpha cells. These findings suggest that the elevated 2′5′AS response of pancreatic beta cells could render them particularly vulnerable to damage and/or apoptosis during virus infection.

Anti-infectious antibodies and autoimmune-associated autoantibodies in patients with type I diabetes mellitus and their close family members

Type 1 diabetes mellitus (T1DM) is an autoimmune disease with complex interactions between genetic and environmental factors. We compared antibody levels to various infectious agents and of autoimmune-associated autoantibodies between Colombian T1DM patients, their close family members and healthy controls. Significantly lower levels of antibodies against several infectious agents were detected in the T1DM patients. These included Helicobacter pylori (P = 0.01), cytomegalovirus (P = 0.001), Epstein-Barr virus (P = 0.02) and Toxoplasma (P = 0.001). T1DM patients had significantly higher levels of IgG-anti-gliadin antibodies (P = 0.001) and IgG-antitissue transglutaminase antibodies (P = 0.03), and a borderline association with anticentromere antibodies (P = 0.06). The lower level of antibodies against infectious agents in T1DM patients may be related to their younger ages, but may also point to a protective role of those infections in T1DM development in susceptible individuals. Our results confirm the association between T1DM and celiac disease. A possible association with anticentromere antibody needs further studies.

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.

The prevalence of enteroviral capsid protein vp1 immunostaining in pancreatic islets in human type 1 diabetes

AIMS/HYPOTHESIS

Evidence that the beta cells of human patients with type 1 diabetes can be infected with enterovirus is accumulating, but it remains unclear whether such infections occur at high frequency and are important in the disease process. We have now assessed the prevalence of enteroviral capsid protein vp1 (vp1) staining in a large cohort of autopsy pancreases of recent-onset type 1 diabetic patients and a range of controls.

METHODS

Serial sections of paraffin-embedded pancreatic autopsy samples from 72 recent-onset type 1 diabetes patients and up to 161 controls were immunostained for insulin, glucagon, vp1, double-stranded RNA activated protein kinase R (PKR) and MHC class I.

RESULTS

vp1-immunopositive cells were detected in multiple islets of 44 out of 72 young recent-onset type 1 diabetic patients, compared with a total of only three islets in three out of 50 neonatal and paediatric normal controls. vp1 staining was restricted to insulin-containing beta cells. Among the control pancreases, vp1 immunopositivity was also observed in some islets from ten out of 25 type 2 diabetic patients. A strong correlation was established between islet cell vp1 positivity and PKR production in insulin-containing islets of both type 1 and type 2 diabetic patients, consistent with a persistent viral infection of the islets.

CONCLUSIONS/INTERPRETATION

Immunoreactive vp1 is commonly found in the islets of recent-onset type 1 diabetes patients, but only rarely in normal paediatric controls. vp1 immunostaining was also observed in some islets of type 2 diabetes patients, suggesting that the phenomenon is not restricted to type 1 diabetes patients.

Maternal enterovirus infection during pregnancy as a risk factor in offspring diagnosed with type 1 diabetes between 15 and 30 years of age

Maternal enterovirus infections during pregnancy may increase the risk of offspring developing type 1 diabetes during childhood. The aim of this study was to investigate whether gestational enterovirus infections increase the offspring's risk of type 1 diabetes later in life. Serum samples from 30 mothers without diabetes whose offspring developed type 1 diabetes between 15 and 25 years of age were analyzed for enterovirus-specific immunoglobulin M (IgM) antibodies and enterovirus genome (RNA), and compared to a control group. Among the index mothers, 9/30 (30%) were enterovirus IgM-positive, and none was positive for enterovirus RNA. In the control group, 14/90 (16%) were enterovirus IgM-positive, and 4/90 (4%) were positive for enterovirus RNA (n.s.). Boys of enterovirus IgM-positive mothers had approximately 5 times greater risk of developing diabetes (OR 4.63; 95% CI 1.22–17.6), as compared to boys of IgM-negative mothers (P < .025). These results suggest that gestational enterovirus infections may be related to the risk of offspring developing type 1 diabetes in adolescence and young adulthood.

Role of coxsackievirus B4 in the pathogenesis of type 1 diabetes

Environmental factors, especially viruses, are thought to play an important role in the initiation or acceleration of the pathogenesis of type 1 diabetes (T1D). Data from retrospective and prospective epidemiological studies strongly suggest that enteroviruses, such as coxsackievirus B4 (CV-B4), may be associated with the development of T1D. It has also been shown that enterovirus infections are significantly more prevalent in at-risk individuals such as the siblings of diabetic patients, when they develop 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 supports the hypothesis of a relationship between the virus and the disease. Furthermore, studies performed in vitro and in vivo in animal models have increased our knowledge of the role of CV-B4 in T1D by helping to clarify the pathogenic mechanisms of the infection that can lead to beta-cell destruction, including direct virus-induced beta-cell lysis, molecular mimicry, 'bystander activation' and viral persistence. The role of enteroviruses as the sole agents in T1D, and a causal link between these agents and T1D, have not yet been established, although arguments that support such a role for these viruses in the pathogenesis of the disease cannot be ignored.

An enterovirus strain isolated from diabetic child belongs to a genetic subcluster of echovirus 11, but is also neutralised with monotypic antisera to coxsackievirus A9

An enterovirus strain (designated D207) isolated from a Slovakian diabetic child and originally serotyped as coxsackievirus A9 (CAV-9) was found to cause rapid cytolysis coinciding with severe functional damage of the surviving cells in primary cultures of human pancreatic islets. This finding prompted us to clone the isolate for full-length genome sequencing and molecular characterization as the prototype strain of CAV-9 is known to cause only minimal damage to insulin-producing β-cells. Based on capsid-coding sequence comparisons, the isolate turned out to be echovirus 11 (E-11). Phylogenetic analyses demonstrated that E-11/D207 was closely related to a specific subgroup B of E-11 strains known to cause uveitis. To study further antigenic properties of isolate E-11/D207 and uveitis-causing E-11 strains, neutralization experiments were carried out with CAV-9- and E-11-specific antisera. Unlike the prototype strains, the isolate E-11/D207 and uveitis-causing E-11 strains were well neutralized with both CAV-9- and E-11-specific antisera. Attempts to identify recombination of the capsid coding sequences as a reason for double-reactivity using the Simplot analysis failed to reveal major transferred motifs. However, peptide scanning technique was able to identify antigenic regions of capsid proteins of E-11/D207 as well as regions cross-reacting with an antiserum raised to CAV-9. Thus, double specificity of E-11/D207 seems to be a real characteristic shared by the phylogenetically closely related virus strains in the genetic subgroup B of E-11.

Genetic and phenotypic diversity of echovirus 30 strains and pathogenesis of type 1 diabetes

Several enterovirus serotypes should be considered as potentially diabetogenic. The capacity of an enterovirus to kill or impair the functions of human beta-cells can vary among the strains within a given serotype as shown previously for echovirus 9 and 30 (E-30). The evolution of E-30 has also shown patterns correlating with the global increase of type 1 diabetes incidence. In the present study, antigenic properties of a set of E-30 isolates were investigated and the results correlated with the previously documented beta-cell destructive phenotype of the strains, or to genetic clustering of the strains. No simple correlation between the three properties was observed. A full-length infectious clone was constructed and sequenced from one of the isolates found to be most destructive to beta-cells (E-30/14916net87). Phylogenetic analyses demonstrated that this strain was closely related to the E-30 prototype strain at the capsid coding region while outside the capsid region prototype strains of several other human enterovirus B serotypes clustered more closely. This suggests that the relatively greater pathogenicity of the strain might be based on properties of the genome outside of the structural protein coding region. Neutralizing antibody assays on sera from 100 type 1 diabetic patients and 100 controls using three different E-30 strains did not reveal differences between the groups. This finding does not support a previous proposition of aberrant antibody responses to E-30 in diabetic patients. It is concluded that identification of the genetic counterparts of pathogenicity of E-30 strains requires further studies.

Study design of the Trial to Reduce IDDM in the Genetically at Risk (TRIGR)

The hypothesis for this study is that weaning to an extensively hydrolyzed infant formula will decrease the incidence of type 1 diabetes (T1D), as it does in all relevant animal models for the disease. This will be tested in children who carry risk-associated human leukocyte antigen genotypes and have a first-degree relative with T1D. The trial will use a double-blind, prospective, placebo-controlled intervention protocol, comparing casein hydrolysate with a conventional cow's milk (CM)-based formula. A secondary aim is to determine relationships between CM antibodies, a measure of CM exposure, and diabetes-associated autoantibodies. To achieve an 80% power for the detection of a 40% intervention-induced difference in the development of autoantibodies and subsequent diabetes, the study requires 2032 subjects. A multicenter, international, collaborative effort is necessary to achieve recruitment targets. A collaborative international study group of 78 clinical centers in 15 countries has therefore been assembled for this purpose.

Improved crystallization of the coxsackievirus B3 RNA-dependent RNA polymerase

The Picornaviridae virus family contains a large number of human pathogens such as poliovirus, hepatitis A virus and rhinoviruses. Amongst the viruses belonging to the genus Enterovirus, several serotypes of coxsackievirus coexist for which neither vaccine nor therapy is available. Coxsackievirus B3 is involved in the development of acute myocarditis and dilated cardiomyopathy and is thought to be an important cause of sudden death in young adults. Here, the first crystal of a coxsackievirus RNA-dependent RNA polymerase is reported. Standard crystallization methods yielded crystals that were poorly suited to X-ray diffraction studies, with one axis being completely disordered. Crystallization was improved by testing crystallization solutions from commercial screens as additives. This approach yielded crystals that diffracted to 2.1 A resolution and that were suitable for structure determination.

Serologic prevalence of coxsackievirus group B in Greece

Coxsackieviruses are human enteroviruses, which have been associated with myocarditis/pericarditis and sudden death. In one investigation (Spanakis N, Manolis EN, Tsakris A, Tsiodras S, Panagiotopoulos T, Saroglou G, and Legakis NJ: J Clin Pathol 2005;58:357-360), a cluster of cases of fatal myocarditis in Greece was linked to coxsackievirus B3. The information from this investigation prompted us to study serologically the prevalence of coxsackieviruses B throughout Greece. Sera were obtained from 506 healthy blood donors from various transfusion centers, covering the entire country. All sera were tested for the presence of IgG and IgM antibodies, using ELISAs with various antigenic specificities: (1) heat-denatured coxsackievirus type B1 and B5 virions, (2) a synthetic peptide from the N terminus of the VP1 protein of coxsackievirus B3, and (3) a synthetic peptide from the N terminus of the VP1 protein of coxsackievirus B4. Sera positive for IgG antibodies against coxsackieviruses B1/B5, B3, and B4 were detected in 6.7 to 21.6% of the individuals tested in the various regions of Greece. Statistical analysis revealed that the highest prevalence of IgG antibodies against coxsackieviruses B1/B5 was found in blood donors from Crete (p = 0.025), whereas the highest prevalence against coxsackievirus B4 was detected in blood donors from Athens (p = 0.01). IgM antibodies against coxsackievirus B were detected at low percentage, less than 5%, with no significant viral preference for particular geographic regions. The preference of anti-coxsackievirus IgG antibodies for particular geographic regions could be potentially related to the previously reported clustering of cases of insulin-dependent diabetes mellitus and myocarditis in Athens and Crete, respectively.

Effects on isolated human pancreatic islet cells after infection with strains of enterovirus isolated at clinical presentation of type 1 diabetes

Enterovirus (EV) infections have been associated with the pathogenesis of type 1 diabetes (T1D). They may cause beta-cell destruction either by cytolytic infection of the cells or indirectly by triggering the autoimmune response. Evidence for EV involvement have been presented in several studies, EV-IgM antibodies have been reported in T1D patients, EV-RNA has been found in the blood from T1D patients at onset, and EV have been isolated from newly diagnosed T1D. Our aim was to study infections with EV isolates from newly diagnosed T1D patients in human pancreatic islets in vitro. Two of them (T1 and T2) originated from a mother and her son diagnosed with T1D on the same day, the other two (A and E) were isolated from a pair of twins at the time of diagnosis of T1D in one of them. Isolated human pancreatic islets were infected and viral replication, viability and degree of cytolysis as well as insulin release in response to high glucose were measured. All four EV isolates replicated in the islet cells and virus particles and virus-induced vesicles were seen in the cytoplasm of the beta-cells. The isolates varied in their ability to induce cytolysis and to cause destruction of the islets and infection with two of the isolates (T1 and A) caused more pronounced destruction of the islets. Infection with the isolate from the healthy twin boy (E) was the least cytolytic. The ability to secrete insulin in response to high glucose was reduced in all infected islets as early as 3 days post infection, before any difference in viability was observed. To conclude, strains of EV isolated from T1D patients at clinical presentation of T1D revealed beta-cell tropism, and clearly affected the function of the beta-cell. In addition, the infection caused a clear increase in the number of dead cells.

Molecular analysis of an echovirus 3 strain isolated from an individual concurrently with appearance of islet cell and IA-2 autoantibodies

Growing evidence has implicated members of the genus Enterovirus of the family Picornaviridae in the etiology of some cases of type 1 diabetes (T1D). To contribute to an understanding of the molecular determinants underlying this association, we determined the complete nucleotide sequence of a strain of echovirus 3 (E3), Human enterovirus B (HEV-B) species, isolated from an individual who soon after virus isolation developed autoantibodies characteristic of T1D. The individual has remained positive for over 6 years for tyrosine phosphatase-related IA-2 protein autoantibodies and islet cell autoantibodies, indicating an ongoing autoimmune process, although he has not yet developed clinical T1D. The sequence obtained adds weight to the observation that recent enterovirus isolates differ significantly from prototype strains and provides further evidence of a role for recombination in enterovirus evolution. In common with most HEV-B species members, the isolate exhibits 2C and VP1 sequences suggested as triggers of autoimmunity through molecular mimicry. However, comparisons with the E3 prototype strain and previously reported diabetogenic and nondiabetogenic HEV-B strains do not reveal clear candidates for sequence features of PicoBank/DM1/E3 that could be associated with autoantibody appearance. This is the first time a virus strain isolated at the time of commencement of beta-cell damage has been analyzed and is an invaluable addition to enterovirus strains isolated previously at the onset of T1D in the search for specific molecular features which could be associated with diabetes induction.

Enteroviruses: new findings on the role of enteroviruses in type 1 diabetes

Common enterovirus infections appear to initiate or facilitate the pathogenetic processes leading to type 1 diabetes, and sometimes also precipitate the clinical disease. It is not known in detail how enterovirus infections bring about the loss of insulin-producing beta-cells, a phenomenon characteristic of the disease. Recent results from studies on pancreases from human autopsies and cultured human islets support the idea that during systemic enterovirus infections, the virus may reach pancreatic islets and cause direct beta-cell damage. Although individual enteroviruses (EV) exhibited differences in their beta-cell tropism in the cultured human islets, all serotypes studied contained highly destructive strains. The final confirmation on the role of enteroviruses in type 1 diabetes can only be obtained from intervention studies. If the association holds true then it would be possible to reduce the risk of developing type 1 diabetes by preventing enterovirus infections with a multivalent enterovirus vaccine that could be given to children soon after birth.

Enterovirus RNA sequences in sera of schoolchildren in the general population and their association with type 1-diabetes-associated autoantibodies

Type 1 diabetes (T1D) is an autoimmune disease linked with genetic factors as well as with environmental triggers, such as virus infections, but the aetiology is still unclear. The authors analysed serum from autoantibody-positive (n=50) and autoantibody-negative (n=50) schoolchildren as well as children newly diagnosed with T1D (n=47; time from diagnosis, median 5 days, interquartile range 1-12 days) for the presence and frequency of enterovirus (EV) and adenovirus sequences. The autoantibody-positive and -negative groups were part of the Karlsburg Type 1 Diabetes Risk Study of a Normal Schoolchild Population, which represents a general population without T1D first-degree relatives. There was no significant seasonality of sampling in any of the three groups investigated. EV RNA sequences were detected in 10 of 50 (20%) autoantibody-positive children and in 17 of 47 (36%) children newly diagnosed with T1D, but only in two of 50 (4%) of the age- and sex-matched controls (P<0.05, P<0.001). Characterization of the EV amplicons by direct sequencing revealed high homology with coxsackievirus B group. For adenovirus we found no data to support an association with T1D. The data support the hypothesis that different enteroviruses may be aetiologically important as a trigger and/or accelerating factor in the process of T1D development.

Global profiling of coxsackievirus- and cytokine-induced gene expression in human pancreatic islets

AIMS/HYPOTHESIS

It is thought that enterovirus infections initiate or facilitate the pathogenetic processes leading to type 1 diabetes. Exposure of cultured human islets to cytolytic enterovirus strains kills beta cells after a protracted period, suggesting a role for secondary virus-induced factors such as cytokines.

METHODS

To clarify the molecular mechanisms involved in virus-induced beta cell destruction, we analysed the global pattern of gene expression in human islets. After 48 h, RNA was extracted from three independent human islet preparations infected with coxsackievirus B5 or exposed to interleukin 1beta (50 U/ml) plus interferon gamma (1,000 U/ml), and gene expression profiles were analysed using Affymetrix HG-U133A gene chips, which enable simultaneous analysis of 22,000 probe sets.

RESULTS

As many as 13,077 genes were detected in control human islets, and 945 and 1293 single genes were found to be modified by exposure to viral infection and the indicated cytokines, respectively. Four hundred and eighty-four genes were similarly modified by the cytokines and viral infection.

CONCLUSIONS/INTERPRETATION

The large number of modified genes observed emphasises the complex responses of human islet cells to agents potentially involved in insulitis. Notably, both cytokines and viral infection significantly (p<0.02) increased the expression of several chemokines, the cytokine IL-15 and the intercellular adhesion molecule ICAM-1, which might contribute to the homing and activation of mononuclear cells in the islets during infection and/or an early autoimmune response. The present results provide novel insights into the molecular mechanisms involved in viral- and cytokine-induced human beta cell dysfunction and death.

Relationship between the incidence of type 1 diabetes and maternal enterovirus antibodies: time trends and geographical variation

AIMS/HYPOTHESIS

We have previously observed an inverse correlation between the incidence of type 1 diabetes and enterovirus infections in the background population. The aim of this study was to analyse whether maternal enterovirus antibody status, which reflects both the frequency of enterovirus infections and the protection conferred by the mother on the offspring, also correlates with the incidence of type 1 diabetes.

METHODS

Maternal enterovirus antibodies were analysed from serum samples taken from pregnant women between 1983 and 2001 in Finland and Sweden using enzyme immunoassay and neutralisation assays. Comparable samples were also taken between 1999 and 2001 in countries with a lower incidence of diabetes (Estonia, Germany, Hungary, Israel, Lithuania, Russia).

RESULTS

A clear decrease was observed in maternal enterovirus antibody levels over the past 20 years (p<0.0001). The frequency of enterovirus antibodies was higher in countries with a low or intermediate incidence of type 1 diabetes compared with high-incidence countries (p<0.0001).

CONCLUSIONS/INTERPRETATION

These findings are in line with our previous observations supporting the hypothesis that a low frequency of enterovirus infection in the background population increases the susceptibility of young children to the diabetogenic effect of enteroviruses.

Phenotypic and genetic changes in coxsackievirus B5 following repeated passage in mouse pancreas in vivo

Common enterovirus infections appear to initiate or facilitate the pathogenetic processes leading to type 1 diabetes, and also sometimes precipitate the clinical disease. In experimental infection of mice, coxsackieviruses have shown to have a strong affinity for the exocrine tissue, while even in lethal cases, the islets remain unaffected. The virus strain most intensively studied in this respect is the diabetogenic variant E2 of coxsackievirus B4. In addition, it is known that all six serotypes of coxsackie B viruses can be made diabetogenic by repeated passages in either mouse pancreas in vivo or in cultured mouse beta-cells in vitro. However, the genetic determinants of the phenomenon have not been determined. In the present study, a laboratory strain of coxsackievirus B5 was passaged repeatedly in mouse pancreas in vivo. After 15 passages, the virus phenotype was clearly changed and infection of the variant resulted in a diabetes-like syndrome in mice characterized by chronic pancreatic inflammation together with dysregulation in glucose metabolism, loss of pancreatic acinar tissue, and mild insulitis. In order to characterize the genetic determinants involved in mouse pancreas adaptation, the passaged virus variant together with the parental virus strain was cloned for molecular characterization. The whole genome sequencing of both virus strains revealed only limited differences. Altogether, eight nucleotides were changed resulting in five amino acid substitutions, of which three were located in the capsid proteins.

OAS1 splice site polymorphism controlling antiviral enzyme activity influences susceptibility to type 1 diabetes

Both genetic and nongenetic factors contribute to the development of type 1 diabetes. Many investigations, including prospective studies of high-risk children, have implicated virus infections as predisposing environmental agents. We previously reported that basal activity of the key antiviral enzyme 2'5'-oligoadenylate synthetase (2'5'AS) was significantly elevated in type 1 diabetic patients compared with healthy control subjects. Recently, we showed that an A/G splice site single nucleotide polymorphism (SNP) in the OAS1 gene encoding 2'5'AS is strongly associated with basal 2'5'AS activity. Basal enzyme activity was highest in individuals with GG genotype and lowest in those with AA genotype. In the present study, we genotyped 835 type 1 diabetic and 401 healthy siblings at the OAS1 splice site polymorphism and (for comparison) at an A/C SNP of the insulin (IDDM2) locus. Results showed that OAS1 GG and GA were significantly increased in diabetic compared with healthy siblings (P = 0.0023). The strength of association was similar to that at IDDM2, where, as expected, the C/C (variable number tandem repeat class I homozygote) genotype was increased in affected compared with healthy siblings (P = 0.0025). The results suggest that host genetic response to virus infection could influence susceptibility to type 1 diabetes.

Variation in antiviral 2',5'-oligoadenylate synthetase (2'5'AS) enzyme activity is controlled by a single-nucleotide polymorphism at a splice-acceptor site in the OAS1 gene

It is likely that human genetic differences mediate susceptibility to viral infection and virus-triggered disorders. OAS genes encoding the antiviral enzyme 2',5'-oligoadenylate synthetase (2'5'AS) are critical components of the innate immune response to viruses. This enzyme uses adenosine triphosphate in 2'-specific nucleotidyl transfer reactions to synthesize 2',5'-oligoadenylates, which activate latent ribonuclease, resulting in degradation of viral RNA and inhibition of virus replication. We showed elsewhere that constitutive (basal) activity of 2'5'AS is correlated with virus-stimulated activity. In the present study, we asked whether constitutive activity is genetically determined and, if so, by which variants. Analysis of 83 families containing two parents and two children demonstrated significant correlations between basal activity in parent-child pairs (P<.0001) and sibling pairs (P=.0044), but not spousal pairs, suggesting strong genetic control of basal activity. We next analyzed association between basal activity and 15 markers across the OAS gene cluster. Significant association was detected at multiple markers, the strongest being at an A/G single-nucleotide polymorphism at the exon 7 splice-acceptor site (AG or AA) of the OAS1 gene. At this unusual polymorphism, allele G had a higher gene frequency in persons with high enzyme activity than in those with low enzyme activity (0.44 vs. 0.20; P=3 x 10(-11)). Enzyme activity varied in a dose-dependent manner across the GG, GA, and AA genotypes (tested by analysis of variance; P=1 x 10(-14)). Allele G generates the previously described p46 enzyme isoform, whereas allele A ablates the splice site and generates a dual-function antiviral/proapoptotic p48 isoform and a novel p52 isoform. This genetic polymorphism makes OAS1 an excellent candidate for a human gene that influences host susceptibility to viral infection.

Overexpression of HLA class I molecules on T cells among type 1 diabetes Brazilian patients

To evaluate the membrane expression of histocompatibility (HLA) class I (A-C) molecules on lymphomononuclear cells involved in the pathogenesis of type 1 diabetes, we studied 20 newly diagnosed Brazilian patients and 20 matched controls. The coexpression of HLA and cluster of differentiation (CD) molecules was evaluated by flow cytometry. Compared to controls, patients presented increased fluorescence intensity of HLA class I molecules on CD3+, CD4+ and CD8+ cells. Patients exhibiting the HLA-DQB1*0201 and/or DQB1*0302 alleles presented increased expression of class I molecules in relation to HLA-matched healthy controls. The increased HLA class I expression in subsets of T cells may be due to the proinflammatory profile of the disease as well as to the presence of diabetes susceptibility alleles.

Detection of enteroviruses in treated drinking water

This study deals with the routine monitoring of drinking water for the presence of enteroviruses, over a period of 1 year. A rapid and simple method was employed for the simultaneous detection and typing of enteroviruses in large-volume water samples. This included an integrated cell culture/nested PCR approach, followed by restriction enzyme analysis. The two drinking water supplies studied were derived from acceptable quality surface water sources using treatment processes, which conform to international specifications for the production of safe drinking water. Enteroviruses (predominantly coxsackie B viruses) were detected in 11% and 16% of the drinking water samples from two treatment plants, respectively. This study confirms that acceptable water quality indicators do not necessarily reflect the virus content of drinking water.

Mechanisms of beta cell death during restricted and unrestricted enterovirus infection

Coxsackie B virus (CVB-5) infections potentially trigger and accelerate pancreatic beta cell damage leading to type 1 diabetes. In vivo, all viruses face natural resistance mediated by various host factors which restrict the progression of infection. Thus, the aims of this study were to generate a tissue culture model of restricted coxsackie B virus infection in primary islet cells by preventing the production of viral progeny with a selective inhibitor of viral RNA replication and to investigate the mechanisms of virus-induced islet cell death during productive and restricted infective conditions. Cultured foetal porcine islet cells were infected effectively with the prototype strain of coxsackievirus B5 (CVB-5). Nuclear viability stainings and electron microscopy showed productive infection to result in dominantly necrotic cell death with additional slight induction of apoptosis during the 7 days of follow-up. The restricted conditions were created by addition of guanidine-hydrochloride (G-HCl) into culture medium. At 1 mM concentration, it significantly protected the infected cells from necrosis and thus maintained high viability. This was associated with increased significantly apoptosis. In perifusion analysis, the cellular ability to release insulin was reduced, although the metabolic integrity was preserved as shown by MTT-analysis and cellular ATP levels. These data show that restriction of CVB-5 replication with G-HCl protects islet cells against virus-induced necrosis. However, restriction of viral replication shifts the mechanism of cell death from necrosis toward apoptosis. A slowly progressing subclinical infection of islets could thus lead to increased beta-cell apoptosis.

Enterovirus infection in human pancreatic islet cells, islet tropism in vivo and receptor involvement in cultured islet beta cells

AIMS/HYPOTHESIS

It is thought that enterovirus infections cause beta-cell damage and contribute to the development of Type 1 diabetes by replicating in the pancreatic islets. We sought evidence for this through autopsy studies and by investigating known enterovirus receptors in cultured human islets.

METHODS

Autopsy pancreases from 12 newborn infants who died of fulminant coxsackievirus infections and from 65 Type 1 diabetic patients were studied for presence of enteroviral ribonucleic acid by in situ hybridisation. Forty non-diabetic control pancreases were included in the study. The expression and role of receptor candidates in cultured human islets were investigated with receptor-specific antibodies using immunocytochemistry and functional assays.

RESULTS

Enterovirus-positive islet cells were found in some of both autopsy specimen collections, but not in control pancreases. No infected cells were seen in exocrine tissue. The cell surface molecules, poliovirus receptor and integrin alphavbeta3, which act as enterovirus receptors in established cell lines, were expressed in beta cells. Antibodies to poliovirus receptor, human coxsackievirus and adenovirus receptor and integrin alphavbeta3 protected islets and beta cells from adverse effects of poliovirus, coxsackie B viruses, and several of the arginine-glycine-aspartic acid motifs containing enteroviruses and human parechovirus 1 respectively. No evidence was found for expression of the decay-accelerating factor which acts as a receptor for several islet-cell-replicating echoviruses in established cell lines.

CONCLUSIONS/INTERPRETATION

The results show a definite islet-cell tropism of enteroviruses in the human pancreas. Some enteroviruses seem to use previously identified cell surface molecules as receptors in beta cells, whereas the identity of receptors used by other enteroviruses remains unknown.

Can enteroviruses cause type 1 diabetes?

Enterovirus infections have long been considered as one possible environmental trigger of type 1 diabetes. These viruses have been detected from diabetic patients more often than from control subjects and they can infect beta cells in cell culture and induce diabetes in animal models. Furthermore, a same kind of seasonality has been observed in both the onset of clinical diabetes and subclinical beta cell autoimmunity (appearance of autoantibodies) as in enterovirus infections. Recently, considerable new evidence has cumulated from prospective studies indicating the risk effect of enterovirus infections long before clinical diabetes was diagnosed. In addition, several studies have reported enterovirus genome sequences in diabetic patients more often than in control subjects. Currently, the evidence for the role of enteroviruses is stronger than for most other environmental agents, but still the final proof is lacking. The ongoing studies aim to prove the risk effect in different populations and to identify the underlying mechanisms. This research field is becoming more and more important because it could open up possibilities to prevent type 1 diabetes by an enterovirus vaccine.

Lack of islet neogenesis plays a key role in beta-cell depletion in mice infected with a diabetogenic variant of coxsackievirus B4

Group B coxsackieviruses (CVBs) have a well-established association with type 1 diabetes but the mechanism of depletion of beta-cell mass following infection has not yet been defined. In this report we show that the major difference in pathogenesis between the E2 diabetogenic strain of CVB4 and the prototypic JVB strain in SJL mice is not in tropism for islet cells but in the degree of damage inflicted on the exocrine pancreas and the resulting capacity for regeneration of both acinar and islet tissue by the host. Both strains replicated to a high titre in acinar tissue up to day 3 post-infection (p.i.), while the islets of Langerhans were largely spared. However, the pancreas in the JVB-infected animals then regenerated and many small islets were seen throughout the tissue by day 10 p.i. In contrast, the acinar tissue in E2-infected mice became increasingly necrotic until all that remained by day 21 p.i. were large islets containing varying numbers of dead cells, caught up in strands of connective tissue. Surviving beta cells were found to synthesize little insulin, although islet amyloid polypeptide was detected and glucagon synthesis in alpha cells appeared normal or enhanced. Our results suggest that the key to CVB-E2-induced damage lies in the exocrine tissue and prevention of islet neogenesis rather than from direct effects on existing islets.