Characterisation of enterovirus RNA detected in the pancreas and other specimens of live patients with newly diagnosed type 1 diabetes in the DiViD study

AIMS/HYPOTHESIS

The Diabetes Virus Detection (DiViD) study is the first study to laparoscopically collect pancreatic tissue and purified pancreatic islets together with duodenal mucosa, serum, peripheral blood mononuclear cells (PBMCs) and stools from six live adult patients (age 24-35 years) with newly diagnosed type 1 diabetes. The presence of enterovirus (EV) in the pancreatic islets of these patients has previously been reported.

METHODS

In the present study we used reverse transcription quantitative real-time PCR (RT-qPCR) and sequencing to characterise EV genomes present in different tissues to understand the nature of infection in these individuals.

RESULTS

All six patients were found to be EV-positive by RT-qPCR in at least one of the tested sample types. Four patients were EV-positive in purified islet culture medium, three in PBMCs, one in duodenal biopsy and two in stool, while serum was EV-negative in all individuals. Sequencing the 5' untranslated region of these EVs suggested that all but one belonged to enterovirus B species. One patient was EV-positive in all these sample types except for serum. Sequence analysis revealed that the virus strain present in the isolated islets of this patient was different from the strain found in other sample types. None of the islet-resident viruses could be isolated using EV-permissive cell lines.

CONCLUSIONS/INTERPRETATION

EV RNA can be frequently detected in various tissues of patients with type 1 diabetes. At least in some patients, the EV strain in the pancreatic islets may represent a slowly replicating persisting virus.

Early Detection of Peripheral Blood Cell Signature in Children Developing β-Cell Autoimmunity at a Young Age

The appearance of type 1 diabetes (T1D)-associated autoantibodies is the first and only measurable parameter to predict progression toward T1D in genetically susceptible individuals. However, autoantibodies indicate an active autoimmune reaction, wherein the immune tolerance is already broken. Therefore, there is a clear and urgent need for new biomarkers that predict the onset of the autoimmune reaction preceding autoantibody positivity or reflect progressive β-cell destruction. Here we report the mRNA sequencing-based analysis of 306 samples including fractionated samples of CD4⁺ and CD8⁺ T cells as well as CD4^-CD8^- cell fractions and unfractionated peripheral blood mononuclear cell samples longitudinally collected from seven children who developed β-cell autoimmunity (case subjects) at a young age and matched control subjects. We identified transcripts, including interleukin 32 (IL32), that were upregulated before T1D-associated autoantibodies appeared. Single-cell RNA sequencing studies revealed that high IL32 in case samples was contributed mainly by activated T cells and NK cells. Further, we showed that IL32 expression can be induced by a virus and cytokines in pancreatic islets and β-cells, respectively. The results provide a basis for early detection of aberrations in the immune system function before T1D and suggest a potential role for IL32 in the pathogenesis of T1D.

Detection and localization of viral infection in the pancreas of patients with type 1 diabetes using short fluorescently-labelled oligonucleotide probes

Enteroviruses, specifically of the Coxsackie B virus family, have been implicated in triggering islet autoimmunity and type 1 diabetes, but their presence in pancreata of patients with diabetes has not been fully confirmed.

To detect the presence of very low copies of the virus genome in tissue samples from T1D patients, we designed a panel of fluorescently labeled oligonucleotide probes, each of 17-22 nucleotides in length with a unique sequence to specifically bind to the enteroviral genome of the picornaviridae family.

With these probes enteroviral RNA was detected with high sensitivity and specificity in infected cells and tissues, including in FFPE pancreas sections from patients with T1D. Detection was not impeded by variations in sample processing and storage thereby overcoming the potential limitations of fragmented RNA. Co-staining of small RNA probes in parallel with classical immunstaining enabled virus detection in a cell-specific manner and more sensitively than by viral protein.

Relative sensitivity of immunohistochemistry, multiple reaction monitoring mass spectrometry, in situ hybridization and PCR to detect Coxsackievirus B1 in A549 cells

BACKGROUND

Enteroviruses (EVs) have been linked to the pathogenesis of several diseases and there is a collective need to develop improved methods for the detection of these viruses in tissue samples.

OBJECTIVES

This study evaluates the relative sensitivity of immunohistochemistry (IHC), proteomics, in situ hybridization (ISH) and RT-PCR to detect one common EV, Coxsackievirus B1 (CVB1), in acutely infected human A549 cells in vitro.

STUDY DESIGN

A549 cells were infected with CVB1 and diluted with uninfected A549 cells to produce a limited dilution series in which the proportion of infected cells ranged from 10(-1) to 10(-8). Analyses were carried out by several laboratories using IHC with different anti-EV antibodies, ISH with both ViewRNA and RNAScope systems, liquid chromatography multiple reaction monitoring mass spectrometry (LC/MRM/MS/MS), and two modifications of RT-PCR.

RESULTS

RT-PCR was the most sensitive method for EV detection yielding positive signals in the most diluted sample (10(-8)). LC/MRM/MS/MS detected viral peptides at dilutions as high as 10(-7). The sensitivity of IHC depended on the antibody used, and the most sensitive antibody (Dako clone 5D8/1) detected virus proteins at a dilution of 10(-6), while ISH detected the virus at dilutions of 10(-4).

CONCLUSIONS

All methods were able to detect CVB1 in infected A549 cells. RT-PCR was most sensitive followed by LC/MRM/MS/MS and then IHC. The results from this in vitro survey suggest that all methods are suitable tools for EV detection but that their differential sensitivities need to be considered when interpreting the results from such studies.

Enterovirus infection of human islets of Langerhans affects β-cell function resulting in disintegrated islets, decreased glucose stimulated insulin secretion and loss of Golgi structure

AIMS/HYPOTHESIS

In type 1 diabetes (T1D), most insulin-producing β cells are destroyed, but the trigger is unknown. One of the possible triggers is a virus infection and the aim of this study was to test if enterovirus infection affects glucose stimulated insulin secretion and the effect of virus replication on cellular macromolecules and organelles involved in insulin secretion.

METHODS

Isolated human islets were infected with different strains of coxsackievirus B (CVB) virus and the glucose-stimulated insulin release (GSIS) was measured in a dynamic perifusion system. Classical morphological electron microscopy, large-scale electron microscopy, so-called nanotomy, and immunohistochemistry were used to study to what extent virus-infected β cells contained insulin, and real-time PCR was used to analyze virus induced changes of islet specific genes.

RESULTS

In islets infected with CVB, GSIS was reduced in correlation with the degree of virus-induced islet disintegration. The expression of the gene encoding insulin was decreased in infected islets, whereas the expression of glucagon was not affected. Also, in islets that were somewhat disintegrated, there were uninfected β cells. Ultrastructural analysis revealed that virus particles and virus replication complexes were only present in β cells. There was a significant number of insulin granules remaining in the virus-infected β cells, despite decreased expression of insulin mRNA. In addition, no typical Golgi apparatus was detected in these cells. Exposure of islets to synthetic dsRNA potentiated glucose-stimulated insulin secretion.

CONCLUSIONS/INTERPRETATION

Glucose-stimulated insulin secretion; organelles involved in insulin secretion and gene expression were all affected by CVB replication in β cells.

Coxsackie-adenovirus receptor expression is enhanced in pancreas from patients with type 1 diabetes

OBJECTIVES

One of the theories connecting enterovirus (EV) infection of human islets with type 1 diabetes (T1D) is the development of a fertile field in the islets. This implies induction of appropriate proteins for the viral replication such as the coxsackie-adenovirus receptor (CAR). The aim of this study was to investigate to what extent CAR is expressed in human islets of Langerhans, and what conditions that would change the expression.

DESIGN

Immunohistochemistry for CAR was performed on paraffin-embedded pancreatic tissue from patients with T1D (n=9 recent onset T1D, n=4 long-standing T1D), islet autoantibody-positive individuals (n=14) and non-diabetic controls (n=24) individuals. The expression of CAR was also examined by reverse transcription PCR on microdissected islets (n=5), exocrine tissue (n=5) and on explanted islets infected with EV or exposed to chemokines produced by EV-infected islet cells.

RESULTS

An increased frequency of patients with T1D and autoantibody-positive individuals expressed CAR in the pancreas (p<0.039). CAR staining was detected more frequently in pancreatic islets from patients with T1D and autoantibody-positive subjects (15/27) compared with (6/24) non-diabetic controls (p<0.033). Also in explanted islets cultured in UV-treated culture medium from coxsackievirus B (CBV)-1-infected islets, the expression of the CAR gene was increased compared with controls. Laser microdissection of pancreatic tissue revealed that CAR expression was 10-fold higher in endocrine compared with exocrine cells of the pancreas. CAR was also expressed in explanted islets and the expression level decreased with time in culture. CBV-1 infection of explanted islets clearly decreased the expression of CAR (p<0.05). In contrast, infection with echovirus 6 did not affect the expression of CAR.

CONCLUSIONS

CAR is expressed in pancreatic islets of patients with T1D and the expression level of CAR is increased in explanted islets exposed to proinflammatory cytokines/chemokines produced by infected islets. T1D is associated with increased levels of certain chemokines/cytokines in the islets and this might be the mechanism behind the increased expression of CAR in TID islets.

Differential effects of three echovirus strains on cell lysis and insulin secretion in beta cell derived lines

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.

Detection of a low-grade enteroviral infection in the islets of langerhans of living patients newly diagnosed with type 1 diabetes

The Diabetes Virus Detection study (DiViD) is the first to examine fresh pancreatic tissue at the diagnosis of type 1 diabetes for the presence of viruses. Minimal pancreatic tail resection was performed 3-9 weeks after onset of type 1 diabetes in six adult patients (age 24-35 years). The presence of enteroviral capsid protein 1 (VP1) and the expression of class I HLA were investigated by immunohistochemistry. Enterovirus RNA was analyzed from isolated pancreatic islets and from fresh-frozen whole pancreatic tissue using PCR and sequencing. Nondiabetic organ donors served as controls. VP1 was detected in the islets of all type 1 diabetic patients (two of nine controls). Hyperexpression of class I HLA molecules was found in the islets of all patients (one of nine controls). Enterovirus-specific RNA sequences were detected in four of six patients (zero of six controls). The results were confirmed in various laboratories. Only 1.7% of the islets contained VP1(+) cells, and the amount of enterovirus RNA was low. The results provide evidence for the presence of enterovirus in pancreatic islets of type 1 diabetic patients, which is consistent with the possibility that a low-grade enteroviral infection in the pancreatic islets contributes to disease progression in humans.

Silent coeliac disease is over-represented in children with type 1 diabetes and their siblings

AIM

This study measured autoantibodies against tissue transglutaminase (anti-tTG) to detect untreated coeliac disease in children with type 1 diabetes and their siblings.

METHODS

Anti-tTG was measured in prospectively collected sera from 169 children at the onset of diabetes, 88 of their siblings and 96 matched control children. Coeliac disease was confirmed with a small intestinal biopsy.

RESULTS

Coeliac disease was diagnosed in five children before diabetes onset. A further 12 children were diagnosed after diabetes onset, without any gastrointestinal symptoms, and 11 of these had anti-tTG at the onset of diabetes, with the remaining child showing seroconversion within 6 months. Hence, all the children with both diseases had anti-tTG at or before diabetes diagnosis, and the prevalence of coeliac disease was 10.1%. Moreover, 6.8% of the siblings and 3.1% of the control children had elevated levels of anti-tTG. None of the siblings reported any coeliac-related symptoms, despite being positive for anti-tTG, and coeliac disease has so far been biopsy confirmed in 4.5%.

CONCLUSION

Silent coeliac disease is over-represented in children with type 1 diabetes and their siblings. All diabetes children and their siblings should be tested and followed for the presence of anti-tTG and coeliac disease.

Coxsackievirus B1 reveals strain specific differences in plasmacytoid dendritic cell mediated immunogenicity

Enterovirus infections are usually mild but can also cause severe illnesses and play a role in chronic diseases, such as cardiomyopathies and type 1 diabetes. Host response to the invading virus can markedly modulate the course of the infection, and this response varies between individuals due to the polymorphism of immune response genes. However, it is currently not known if virus strains also differ in their ability to stimulate the host immune system. Coxsackievirus B1 (CBV1) causes severe epidemics in young infants and it has recently been connected with type 1 diabetes in seroepidemiological studies. This study evaluated the ability of different field isolates of CBV1 to induce innate immune responses in PBMCs. CBV1 strains differed markedly in their capacity to induce innate immune responses. Out of the 18 tested CBV1 strains two induced exceptionally strong alpha interferon (IFN-α) response in PBMC cultures. The responding cell type was found to be the plasmacytoid dendritic cell. Such a strong innate immune response was accompanied by an up-regulation of several other immune response genes and secretion of cytokines, which modulate inflammation, and adaptive immune responses. These results suggest that enterovirus-induced immune activation depends on the virus strain. It is possible that the immunotype of the virus modulates the course of the infection and plays a role in the pathogenesis of chronic immune-mediated enterovirus diseases.

Evaluation of the fidelity of immunolabelling obtained with clone 5D8/1, a monoclonal antibody directed against the enteroviral capsid protein, VP1, in human pancreas

AIMS/HYPOTHESIS

Enteroviral infection has been implicated in the development of islet autoimmunity in type 1 diabetes and enteroviral antigen expression has been detected by immunohistochemistry in the pancreatic beta cells of patients with recent-onset type 1 diabetes. However, the immunohistochemical evidence relies heavily on the use of a monoclonal antibody, clone 5D8/1, raised against an enteroviral capsid protein, VP1. Recent data suggest that the clone 5D8/1 may also recognise non-viral antigens; in particular, a component of the mitochondrial ATP synthase (ATP5B) and an isoform of creatine kinase (CKB). Therefore, we evaluated the fidelity of immunolabelling by clone 5D8/1 in the islets of patients with type 1 diabetes.

METHODS

Enteroviral VP1, CKB and ATP5B expression were analysed by western blotting, RT-PCR and immunocytochemistry in a range of cultured cell lines, isolated human islets and human tissue.

RESULTS

Clone 5D8/1 labelled CKB, but not ATP5B, on western blots performed under denaturing conditions. In cultured human cell lines, isolated human islets and pancreas sections from patients with type 1 diabetes, the immunolabelling of ATP5B, CKB and VP1 by 5D8/1 was readily distinguishable. Moreover, in a human tissue microarray displaying more than 80 different cells and tissues, only two (stomach and colon; both of which are potential sites of enterovirus infection) were immunopositive when stained with clone 5D8/1.

CONCLUSIONS/INTERPRETATION

When used under carefully optimised conditions, the immunolabelling pattern detected in sections of human pancreas with clone 5D8/1 did not reflect cross-reactivity with either ATP5B or CKB. Rather, 5D8/1 is likely to be representative of enteroviral antigen expression.

Infection of human islets of Langerhans with two strains of Coxsackie B virus serotype 1: assessment of virus replication, degree of cell death and induction of genes involved in the innate immunity pathway

Type 1 diabetes mellitus is believed to be triggered, in part, by one or more environmental factors and human enteroviruses (HEVs) are among the candidates. Therefore, this study has examined whether two strains of HEV may differentially affect the induction of genes involved in pathways leading to the synthesis of islet hormones, chemokines and cytokines in isolated, highly purified, human islets. Isolated, purified human pancreatic islets were infected with strains of Coxsackievirus B1.Viral replication and the degree of CPE/islet dissociation were monitored. The expression of insulin, glucagon, CXCL10, TLR3, IF1H1, CCL5, OAS-1, IFNβ, and DDX58 was analyzed. Both strains replicated in islets but only one of strain caused rapid islet dissociation/CPE. Expression of the insulin gene was reduced during infection of islets with either viral strain but the gene encoding glucagon was unaffected. All genes analyzed which are involved in viral sensing and the development of innate immunity were induced by Coxsackie B viruses, with the notable exception of TLR3. There was no qualitative difference in the expression pattern between each strain but the magnitude of the response varied between donors. The lack of virus induced expression of TLR3, together with the differential regulation of IF1H1, OAS1 and IFNβ, (each of which has polymorphic variants influence the predisposition to type 1 diabetes), that might result in defective clearance of virus from islet cells. The reduced expression of the insulin gene and the unaffected expression of the gene encoding glucagon by Coxsackie B1 infection is consistent with the preferential β-cell tropism of the virus.

Human enterovirus species B in ileocecal Crohn's disease

OBJECTIVES

Advanced ileocecal Crohn's disease (ICD) is characterized by strictures, inflammation in the enteric nervous system (myenteric plexitis), and a high frequency of NOD2 mutations. Recent findings implicate a role of NOD2 and another CD susceptibility gene, ATG16L1, in the host response against single-stranded RNA (ssRNA) viruses. However, the role of viruses in CD is unknown. We hypothesized that human enterovirus species B (HEV-B), which are ssRNA viruses with dual tropism both for the intestinal epithelium and the nervous system, could play a role in ICD.

METHODS

We used immunohistochemistry and in situ hybridization to study the general presence of HEV-B and the presence of the two HEV-B subspecies, Coxsackie B virus (CBV) and Echovirus, in ileocecal resections from 9 children with advanced, stricturing ICD and 6 patients with volvulus, and in intestinal biopsies from 15 CD patients at the time of diagnosis.

RESULTS

All patients with ICD had disease-associated polymorphisms in NOD2 or ATG16L1. Positive staining for HEV-B was detected both in the mucosa and in myenteric nerve ganglia in all ICD patients, but in none of the volvulus patients. Expression of the cellular receptor for CBV, CAR, was detected in nerve cell ganglia.

CONCLUSIONS

The common presence of HEV-B in the mucosa and enteric nervous system of ICD patients in this small cohort is a novel finding that warrants further investigation to analyze whether HEV-B has a role in disease onset or progress. The presence of CAR in myenteric nerve cell ganglia provides a possible route of entry for CBV into the enteric nervous system.

Tropism Analysis of Two Coxsackie B5 Strains Reveals Virus Growth in Human Primary Pancreatic Islets but not in Exocrine Cell Clusters In Vitro

Human Enteroviruses (HEVs) have been implicated in human pancreatic diseases such as pancreatitis and type 1 diabetes (T1D). Human studies are sparse or inconclusive and our aim was to investigate the tropism of two strains of Coxsackie B virus 5 (CBV-5) in vitro to primary human pancreatic cells. Virus replication was measured with TCID50 titrations of aliquots of the culture medium at different time points post inoculation. The presence of virus particles or virus proteins within the pancreatic cells was studied with immunohistochemistry (IHC) and electron microscopy (EM). None of the strains replicated in the human exocrine cell clusters, in contrast, both strains replicated in the endocrine islets of Langerhans. Virus particles were found exclusively in the endocrine cells, often in close association with insulin granules. In conclusion, CBV-5 can replicate in human endocrine cells but not in human exocrine cells, thus they might not be the cause of pancreatitis in humans. The association of virus with insulin granules might reflect the use of these as replication scaffolds.

Modulation of innate immunity in human pancreatic islets infected with enterovirus in vitro

Present knowledge of innate immunity in infected cells relies on studies of cell lines and animal models. In this study, primary human pancreatic islets of Langerhans were used to study virus-host interactions in a model of the possible induction of type 1 diabetes by enterovirus (EV). Human islets were infected with a strain of EV isolated at onset of type 1 diabetes, or exposed to synthetic dsRNA (poly(I:C)), used commonly to mimic viral infection. Induction of innate immunity and the effect of the female sex hormone 17β-estradiol, known to have cell-protective effects, on islet chemokine secretion were investigated. 17β-Estradiol reduced EV-but not poly(I:C)-induced IP-10/CXCL10 secretion from human islets, suggesting that separate signaling pathways of the innate immune response are triggered by EV and poly(I:C), respectively. Infection with EV increased the gene-expression of toll-like receptor 3, interferon-β, and the intracellular helicase MDA5, involved in antiviral innate immunity, multi-fold over time, whereas poly(I:C) increased the expression of these genes transiently. The induced expression pattern was similar in all donors, but the expression levels varied greatly. Pre-exposure to poly(I:C) blocked viral replication in islets from 56% of the donors. These data provide insight on the innate immune responses induced by EV in human islets, and show that this can be modulated by 17β-estradiol, and suggest an important difference between virus- and poly(I:C)-induced signaling.

Enterovirus markers and serum CXCL10 in children with type 1 diabetes

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

Antiviral effect of nicotinamide on enterovirus-infected human islets in vitro: effect on virus replication and chemokine secretion

Type 1 diabetes is a chronic disease characterized by the selective destruction of insulin-producing cells in the pancreas. Enterovirus (EV) is the prime candidate to initiate this destruction and several inflammatory chemokines are induced by EV infection. Nicotinamide has been shown to protect isolated human islets, and to modulate chemokine expression. The aim of this study was to evaluate the effect of nicotinamide on EV replication and EV-induced chemokine secretion and cytolysis of human islets. Two EV strains were used to infect human islets in vitro, one lytic (Adrian) isolated from a child at onset of type 1 diabetes, and one non-lytic (VD2921). Secretion of the chemokines IP-10 and MCP-1, viral replication, and virus-induced cytopathic effect (CPE), were measured at different time points post-infection. Addition of nicotinamide to the culture medium reduced viral replication and virus-induced islet destruction/CPE, significantly. Both EV strains increased secretion of IP-10 and MCP-1, when measured days 2-3, and days 5-7 post infection, compared to mock-infected control islets. IP-10 was not produced by uninfected isolated islets, whereas a basal secretion of MCP-1 was detected. Interestingly, addition of nicotinamide blocked completely (Adrian), or reduced significantly (VD2921), the virus-induced secretion of IP-10. Secretion of MCP-1 was also reduced in the presence of nicotinamide, from infected and uninfected islets. The reported antiviral effects of nicotinamide could have implications for the treatment/prevention of virus- and immune-mediated disease. Also, this study highlights a possible mechanism of virus-induced type 1 diabetes through the induction of MCP-1 and IP-10 in pancreatic islets.

A unifying hypothesis on the development of type 1 diabetes and celiac disease: gluten consumption may be a shared causative factor

This paper presents a hypothesis of the aetiology of the increasing incidence of type 1 diabetes (T1D). This together with the global increased incidence of celiac disease (CD) and that these increases cannot be explained by genetic factors suggest a common environmental factor for these two diseases. Even though enterovirus (EV) infections are believed to trigger T1D and gluten is the trigger of CD, the increasing intake of gluten containing products all over the world could be the trigger for both diseases directly and indirectly. It has been shown that the duration of exposure to gluten is related to the prevalence of T1D. It has also been shown that T1D patients at onset have an inflammatory reaction in the gut. Hence, early diagnose of CD followed by elimination of dietary gluten will lead to a decreased incidence of T1D.

Recent enterovirus infection in type 1 diabetes: evidence with a novel IgM method

Enterovirus (EV) infection has been associated with Type 1 (T1D) diabetes and on a few occasions virus could be isolated at onset of the disease. Using two such isolates as antigens in a quantitative PCR enhanced immunoassay (T1D-EV-QPIA) we have measured IgM antibodies against such potentially diabetogenic viruses in serum from 33 newly diagnosed T1D children, 24 siblings, and 27 healthy children. Sera were also analysed with regard to autoantibodies against GAD65, the cytokine TNF-alpha and the chemokine IP-10. EV-RNA detection was performed on peripheral blood mononuclear cells (PBMC). IgM antibodies against this "new" EV antigen were more frequent in serum from T1D children than in serum from siblings and/or controls (P < 0.001). EV-RNA was detected more frequently in PBMC from T1D children than in healthy control children (P < 0.001) and also compared to the siblings (P < 0.003). The cytokine TNF-alpha was less frequently detected in serum from the T1D children compared with serum from siblings and/controls (P < 0.001). A positive correlation was found between the results obtained with the T1D-EV-QPIA and the EV-PCR (P < 0.001). These findings are in line with earlier findings of an increased frequency of enteroviral infections in newly diagnosed T1D patients. In addition, we found that T1D children at onset of the disease had lower frequencies of the chemokine TNF-alpha in their serum than age- and sex-matched controls had, suggesting an impaired immune response.

Antiviral treatment of Coxsackie B virus infection in human pancreatic islets

Enterovirus infections of the pancreatic islets are believed to trigger or precipitate the near total destruction of beta-cells that constitutes type 1 diabetes (T1D). This study investigated the ability of an anti-picornaviral compound, pleconaril, to block the replication of two beta-cell tropic Coxsackie B4 virus (CBV-4) strains in isolated human islets. The two strains, VD2921 and V89 4557, with demonstrated abilities to cause non-lytic persistence or lytic infection, respectively, in islets, represented two different potential mechanisms behind virus-induced T1D. The virus replication in the islets was studied with and without addition of pleconaril. In addition, islet morphology was studied every day. To test the effects of pleconaril and/or DMSO on the beta-cells' insulin secretion, glucose perifusions were performed on treated and untreated islets. Virus titrations showed a clear reduction of the replication of both strains after pleconaril treatment. The VD2921 strain was inhibited to undetectable levels. The V89 4557 strain, however, showed an initial reduction of titers but virus titers then increased despite the addition of a second dose of pleconaril. This incomplete inhibition of viral replication suggested the existence of a resistant subtype within this strain. Pleconaril treatment reduced the beta-cells' insulin secretion in response to glucose stimulation in some experiments and induced slight morphological changes to the islets compared to untreated controls. In summary, pleconaril reduced the replication of the two beta-cell tropic CBV-4 strains in human islets. However, genetic differences between these strains influenced the effectiveness of pleconaril treatment. This stresses the importance of using multiple viral strains in antiviral tests.

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.

Induction of the chemokine interferon-gamma-inducible protein-10 in human pancreatic islets during enterovirus infection

AIMS/HYPOTHESIS

Enterovirus infections have long been suspected to be environmental factors that may cause type 1 diabetes, but the pathways leading from infection to beta cell destruction are still unknown. We therefore examined whether enterovirus infection of human islets leads to upregulation of interferon-gamma-inducible protein (IP-10, now known as chemokine [C-X-C motif] ligand 10 [CXCL10]), a chemokine important for the induction of insulitis.

METHODS

Isolated human islets were infected with three different strains of Coxsackie B4 virus. IP-10 expression and secretion from the infected human islets were then measured using RT-PCR and ELISA at several time points.

RESULTS

IP-10 was clearly upregulated in and secreted from human islets during enterovirus infection. This was demonstrated with three different strains of Coxsackie B4 virus, two of which are lytic to islets and one which is non-lytic and can establish a persistent infection in human islets.

CONCLUSIONS/INTERPRETATION

We propose that enterovirus-induced upregulation of IP-10 during infection of the islets in vivo is the first step towards destructive insulitis. Our findings support the idea that enterovirus infection triggers immune-mediated beta cell destruction, and for the first time suggest a possible mechanism behind enterovirus-induced diabetes.

Quantitative PCR-enhanced immunoassay for measurement of enteroviral immunoglobulin M antibody and diagnosis of aseptic meningitis

A PCR-enhanced immunoassay (PIA) to detect enterovirus (EV) immunoglobulin M (IgM) for diagnosis of recent EV infection was recently developed. This test was compared with another EV IgM capture technique, the solid-phase reverse immunosorbent test (SPRIST). Fourteen of 43 serum samples from aseptic meningitis patients were positive by PIA, whereas 10 were positive by SPRIST. One of 39 control serum samples was weakly positive by PIA. A single-serum-dilution real-time PCR-based PIA for EV IgM (quantitative PIA [QPIA]) was also developed and evaluated against PIA, SPRIST, an EV IgM radioimmunoassay (RIA), and clinical data. A mixture of 12 EVs was used as the antigen. Results from investigating four groups of serum samples were as follows. (i) The nine PIA-positive serum samples in group 1 were all positive by QPIA. (ii) Group 2 consisted of 59 serum samples from aseptic meningitis patients. Nineteen of 30 serum samples (63%) taken at hospital admission were positive by QPIA. Of these, 17 were positive in EV PCR. (iii) None of the 30 control serum samples in group 3 were positive by QPIA. (iv) For the 24 serum samples in group 4, of which 11 were positive and 13 were negative by RIA, the QPIA results were completely concordant. The sensitivity and specificity of QPIA for diagnosis of EV infection were 70 and 80%, respectively. QPIA provides a rational strategy for the detection of EV IgM, allows the use of viral antigens with minimal purification, and needs no virus-specific reagents apart from those in the PCR. QPIA is a generally applicable method for the detection of viral IgM in IgM capture assays.

Simultaneous type 1 diabetes onset in mother and son coincident with an enteroviral infection

Enterovirus (EV) infections have been implicated in the development 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. Virus was isolated from a woman at diagnosis of T1D (Tuvemo 1) and in addition, virus was isolated from her son at diagnosis of T1D at the same day (Tuvemo 2). None of the isolates could initially be serotyped by conventional methods. The Tuvemo 1 virus was genotyped and after sub-cultivation it was also serotyped as Coxsackievirus B5. The mother revealed antibodies against GAD65. The boy and the father both revealed a significant increase in neutralization antibody titre against two strains of CBV-4, clearly indicating a recent or ongoing EV infection. In addition, the brother showed such a titre rise against another CBV-4 strain (E2) and against a CBV-5 strain (4429). These results show that the whole family had a proven EV infection at the time of T1D diagnosis of the mother and the 10-years-old boy, indicating that the infection might cause or accelerate the T1D.

Inflammatory gene expression in Coxsackievirus B-4-infected human islets of Langerhans

The event that triggers the autoimmune destruction of insulin-producing beta-cells in type 1 diabetes mellitus (T1DM) is still unknown. Enterovirus, especially Coxsackievirus, infections have long been associated with this disease. Cytokines and chemokines induced by an enterovirus infection may act to trigger the autoimmune reactions that produce T1DM. Gene expression was examined in isolated human islets infected with a Coxsackievirus-B4 (CBV-4) strain causing lytic infection (V89-4557) and in islets infected with a CBV-4 strain establishing persistent infection (VD2921). Microarray analysis indicated that infection with the CBV-4 strains resulted in specific induction of a number of inflammatory genes, including IL-1beta, IL-6, IL-8, MCP-1, and RANTES. Importantly, the inflammatory genes induced by the CBV-4 infections differed in the two strains, with more cytokines being induced by the non-lytic CBV-4 strain than by the lytic strain. These cytokines and chemokines have the potential to rapidly induce inflammatory reactions when expressed in vivo and could contribute to the autoimmune reactions associated with the development of T1DM.

Strains of coxsackie virus B4 differed in their ability to induce acute pancreatitis and the responses were negatively correlated to glucose tolerance

The outcome of infections with three CVB4 strains known to replicate in human pancreatic islet cells (E2, V89 4557 and VD2921) and one CVB3 strain (Nancy) in CBA/J mice with regard to viral replication, inflammation and glucose tolerance was studied. Isolation of virus from hearts, livers and pancreata was performed 7, 14 and 21 days post infection (pi). All strains could be equally well isolated from the pancreata and all but one strain, V89 4557, could be isolated from the hearts. The titers of neutralizing antibodies in the mice infected with the CVB4 strain V89 4557 were significantly lower than in mice infected with the other strains (p < 0.01). Even though virus was isolated from both heart and pancreata, immunohistochemical staining only revealed inflammatory cells in the latter. Seven days pi there was a significant difference between the strains in this respect i.e. mice infected with CVB3 and the E2 strain revealed more CD4+ lymphocytes, macrophages and granulocytes compared to mice infected with the other CBV strains (p < 0.05). Glucose tolerance tests performed at day 14 and at day 115 pi revealed normal kinetics of glucose absorption from the blood in the control mice and in mice infected with the strains that induced severe inflammation of the pancreas (E2 and CVB3). In contrast, the glucose clearance in mice infected with the CVB4 strains V89 4557 and VD2921 were significantly impaired compared to uninfected controls and compared to mice infected with the other CVB strains (p < 0.01). Mice infected with CVB4 strains V89 4557 also had a significantly impaired clearance of glucose 120 min after injection (p < 0.05) even though no virus could be isolated and no inflammation was detected in the pancreata at that time point. These results show that there is a clear strain difference with regard to the ability to affect clearance of glucose from the blood as late as 115 days pi as well as the degree of inflammation in the pancreas. This indicates that the in vitro diabetogenic strains (VD2921 and V89 4557) also in vivo can induce a pre-diabetic state in CBA/J mice.

dsRNA formed as an intermediate during Coxsackievirus infection does not induce NO production in a β-cell line with or without addition of IFN-γ

Virus infection is one environmental factor that has been implicated as a precipitating event initiating beta-cell damage during the development of type 1 diabetes. One aim of this study was to investigate how permissive an insulin-producing beta-cell line, RINm5F, is to enterovirus (EV) infections. A second aim was to study if the viral replicative intermediate, double-stranded RNA (dsRNA), together with IFN-gamma results in nitric oxide (NO) production. Monolayer cultures of RINm5F cells were not permissive to infection with seven different strains of EV. However, when the growth pattern of the beta-cell line changed and the cells started to grow as free-floating RIN cell clusters (RCC), all EV strains replicated. Immunostaining for the Coxsackie-adenovirus-receptor (CAR) detected the protein on the free-floating RIN cell clusters, but not on the RINm5F cells cultured as a monolayer of beta-cells. This shows that the CAR expression can change and/or the CAR protein can be redistributed on the cell surface as a consequence of altered growth pattern thus allowing viral replication in a previously non-permissive beta-cell line. As expected, NO production was significantly increased (p<0.05) by addition of synthetic dsRNA and IFN-gamma to the RCC. In contrast, the dsRNA formed during virus infection with a Coxsackievirus B4 strain (E2) with or without addition of IFN-gamma did not induce NO production in these cells. This indicates that synthetic dsRNA does not mimic a real viral infection in that respect, and suggests an NO-independent mechanism for virus-induced beta-cell damage.

Enterovirus infections with beta-cell tropic strains are frequent in siblings of children diagnosed with type 1 diabetes children and in association with elevated levels of GAD65 antibodies

Enterovirus infections have been associated with type 1 diabetes in a number of reports. Recent prospective studies have suggested that enterovirus infections initiate the autoimmune process. Variation in virulence and replication pattern between strains of a serotype has also been shown. The aim was to study if there were specific Coxsackievirus strains that were associated more often with the type 1 diabetes children than with controls and/or siblings and to analyse if there was any time-relationship between such infections and the appearance of antibodies against glutamic acid decarboxylase 65 (GAD65). In the present study, serum was tested from newly diagnosed type 1 diabetes children, their siblings and matched controls for neutralising antibodies against different strains of Coxsackievirus B (CBV). Tests for the presence of antibodies against GAD65 in the same groups were also carried out. Newly diagnosed type 1 diabetes children revealed higher titres of neutralising antibodies against a strain of Coxsackievirus B4 (CBV-4, VD2921) that has been shown to cause persistent infection in human pancreatic islet cells. The type 1 diabetes child and its sibling often encountered the same infection. Among the former, 16 of 27 (59%) had a significant rise in neutralising antibodies. Eight of the type 1 diabetes children had such a rise against a recombinant strain, V89 4557. Among the siblings 10 of 13 (77%) had significant titre increases. Among the type 1 diabetes children, increasing neutralising titres was associated positively with increasing antibody levels against GAD65. All siblings with antibodies against GAD 65 had significant titre increase against any of the CBV strains.

Cell culture propagation and biochemical analysis of the Ljungan virus prototype strain

Ljungan virus (LV) is proposed as a potentially important rodent harbored viral human pathogen. Little is known about the biophysical nature of the virus and despite being molecularly characterized, progress in epidemiological and basic biological studies of LV has been hampered by the lack of a robust and reliable cell culture propagation system. Here we report the first description of an efficient lytic multi-cycle cell culture propagation of the LV prototype strain (87-012). Biophysical analysis of gradient purified LV virions generated by this system identified mature infectious virions to possess a sedimentation coefficient of 160S and in agreement with previous molecular prediction, polyprotein analysis suggests that the native virion is composed of only three major structural proteins. The nucleotide composition of the complete genome of the LV cell culture adapted virus was determined and compared to that of the parental prototype LV. Numerous mutations were observed scattered throughout the viral genome and particularly in VP1. The development of this cell culture system for LV should open new avenues in the study of LV biology, structure, pathogenesis, and prevalence of natural infection in the wider community.

Complete nucleotide sequence of a Coxsackievirus B-4 strain capable of establishing persistent infection in human pancreatic islet cells: effects on insulin release, proinsulin synthesis, and cell morphology

The aim of the present investigation was to study the effect of infection of human pancreatic islet cells with a strain (VD2921) of Coxsackie B virus serotype 4 capable of establishing persistent infection in these cells, as well as to sequence the strain, to study the determinants of virulence and persistence. Groups of islets were infected and assessments of proinsulin, insulin content, and virus replication were made. Insulin release in response to high glucose was measured. Infected and control islets displayed a strong insulin response to high glucose 3-4 days as well as 7-8 days post-infection (dpi). At 11-17 dpi, the infected islets did not respond at all to high glucose, and the response of the control islets was at this late time point somewhat reduced. The insulin and proinsulin content of the infected islets did not differ significantly from that of the control islets. TCID(50) titrations showed that the VD2921 strain replicated in the islet cells during the whole study. Electron microscopic examination of infected islets did not reveal any virus-induced changes of cell morphology compared with the controls, although higher magnifications of the infected beta-cells showed virus-like particles in the cytoplasm. These results show that certain strains of Coxsackievirus B-4 in vitro can establish a persistent infection that might mimic, the more gradual loss of beta-cell function seen during the clinical course of autoimmune diabetes. The ability of this Coxsackievirus B-4 strain to establish a persistent infection might be due to substitution of 11 amino acids located at the surface of the structural protein VP1, adjacent to the predicted receptor binding canyon of the virus.

Enterovirus RNA is found in peripheral blood mononuclear cells in a majority of type 1 diabetic children at onset

We have studied the occurrence of enterovirus (EV)-RNA at the onset of childhood type 1 diabetes in all 24 new cases of childhood type 1 diabetes during 1 year in Uppsala county, Sweden. We also studied 24 matched control subjects and 20 siblings of the patients. RNA was isolated from peripheral blood mononuclear cells and EV-RNA detected by RT-PCR. Primers (groups A and B) corresponding to conserved regions in the 5' noncoding region (NCR) of EV were used in the PCRs, and the amplicons were sequenced. By the use of group A primers, EV-RNA was found in 12 (50%) of the 24 type 1 diabetic children, 5 (26%) of 19 siblings, and none of the control subjects. Both patients and siblings showed a higher frequency of EV-RNA compared with the control subjects. The group B primers detected EV-RNA in all three groups but did not show statistically significant differences between the groups. The EV-RNA positivity with the group B primers was 11 (46%) of 24 in the type 1 diabetic children, 11 (58%) of 19 in the siblings, and 7 (29%) of 24 in the control subjects. The significant difference between groups seen with the group A primers but not with the group B primers might indicate the existence of diabetogenic EV strains. The phylogenetic analysis of the PCR products revealed clustering of the sequences from patients and siblings into five major branches when the group A PCR primers were used. With the group B primers, the sequences from patients, siblings, and control subjects formed three major branches in the phylogenetic tree, where 6 of the 7 control subjects clustered together in a sub-branch of CBV-4/VD2921. Seven of the type 1 diabetic children clustered together in another sub-branch of CBV-4/VD2921. Five of the type 1 diabetic children formed a branch together with the CBV-4/E2 strain, four clustered together with CBV-5, and one formed a branch with echovirus serotype. The presence of EV-RNA in the blood cells of most newly diagnosed type 1 diabetic children supports the hypothesis that a viral infection acts as an exogenous factor. In addition, sequencing of the PCR amplicons from the type 1 diabetic children, their siblings, and matched control subjects might reveal differences related to diabetogenic properties of such a virus.

The replication of certain Coxsackie B virus strains in CHO cells

Cell surface molecules that can act as viral receptors may exert an important selective pressure on RNA viral quasi-species. Coxsackie-Adenovirus Receptor and Decay Accelerating Factor (DAF, CD55) have been identified as receptors for Coxsackie B virus. In studies of viral replication using different strains of Coxsackievirus serotype 4 (CBV-4), it was found that despite lack of expression of these cell surface molecules on Chinese Hamster Ovary (CHO) cells and despite their common use as negative controls in Coxsackie B virus receptor assays, two strains were able to replicate, one (V89-4557) without cytopathic effect (CPE), and the other (T318) with strong CPE. A weak signal was obtained using antibodies against enterovirus, visualized with FITC-conjugated antibodies, when the Coxsackievirus B4 strain V89-4557 was inoculated on CHO cells compared to no signal with the non-replicating Coxsackievirus B4 strain VD2921, indicating some degree of binding of the former to the cells.

Mechanisms of chronic enteroviral persistence in tissue

Although the association remains controversial, enteroviruses have been implicated in the aetiology of several chronic diseases in humans. Investigations in vitro lead to better understanding of virus-cell interactions, and improve our knowledge of the molecular factors that are involved in the establishment and maintenance of these infections. Recent findings suggest that the most important factor in the establishment of a persistent infection is receptor usage. Studies of the mechanisms that are at work in these in-vitro models of viral infection have shown that there is frequently a co-evolution of mutant cells with higher resistance to viral infection and of virus variants with increased virulence (i.e. variants with the ability to utilize other cell-surface molecules as receptors).

Differences in inhibition of replication between Coxsackie B4 virus strains in various cell lines by antibodies to some cell surface proteins

Monoclonal antibodies that interact with the decay accelerating factor (DAF, CD55), the lymphocyte homing receptor (CD44) or the intercellular adhesion molecule I (ICAM- 1) were found to inhibit the replication of different strains of Coxsackievirus serotype B4 (CBV-4) to various extent. By adding antibodies to CD55 the replication of two (V345 and VD2921) of seven strains in HeLa cells, three (V89-4557, VD2921 and T318) of seven in A549-10C cells and one (VD2921) of five strains in RD cells was blocked totally. Consequently, the replication of one strain (VD2921) was blocked in all cells indicating that this strain uses CD55 as a receptor or as a co-receptor on all cell lines and is unable to use another cell surface protein. The binding of this strain to the cell surface was inhibited by the antibodies to CD55. None of the CBV-4 strains was blocked totally by adding antibodies to CD44 to HeLa and A549-10C cells, whereas in RD cells the replication of one (T318) of the CBV-4 strains was blocked totally. The antibodies to ICAM-1 did not inhibit totally the replication of any strain in HeLa and RD cells, but it blocked totally the replication of one strain (CBV-4-E) in A549-10C cells. In HeLa and A549-10C cells the degree of replication correlated highly with the degree of cytopathic effect (CPE). In RD cells, four of the strains replicated without CPE. The adding of antibodies to the integrin alpha(v)beta(3) led to slightly enhanced replication of three of the CBV-4 strains in all cell lines. It is concluded that the receptor usage by different strains of CBV-4 varies not only within the same cells but also between different cell lines.

Persistence of coxsackievirus B4 infection in rhabdomyosarcoma cells for 30 months. Brief report

A persistent infection of rhabdomyosarcoma (RD) cells by Coxsackie B4 virus (CBV-4) was established. The persistently infected RD (piRD) cells have been maintained for over 130 passages (30 months) and have released virus continuously without cellular destruction. The production of infectious virus declined three times during the study. After the first decline (third week post infection) a viral variant with a littered cytopathic effect (CPE) and a marked delayed replication cycle on Green Monkey Kidney (GMK) cells, replaced the original viral population. 100-fold diluted cell cultures were recovered from the piRD cells at the 48(th) and 104(th) passage. All 96 cultures from the former whereas 72% from the second dilution showed virus production when tested on GMK cells. Using a streptavidin/biotin immune-staining assay all piRD cells were positively stained. Test for ts mutants showed that the persistence of the CBV-4 strain was not dependent upon incubation temperature and addition of the antiviral compound disoxaril did not cure the piRD cells.

Tissue culture of isolated human pancreatic islets infected with different strains of coxsackievirus B4: assessment of virus replication and effects on islet morphology and insulin release

The aim was to study whether different strains of Coxsackievirus B4 (CBV-4) are able to infect human pancreatic islet cells in vitro and cause morphological and functional damages. Isolated islets maintained in tissue culture were infected with five well- characterised strains of CBV-4. Aliquots of the culture medium were analysed with regard to virus replication and insulin content. Infected and uninfected islets were examined by light microscopy to determine the degree of virus-induced cytopathic effect (CPE). The results showed that the islet cells were susceptible to infection by all the strains of CBV-4 although the outcome of the infection differed. The virus titres obtained at 48 and 72 hours post infection differed significantly between all the CBV-4 strains (p<0.001), indicating different ability to replicate in islet cells. Pronounced to weak CPE, which was partly due to the origin (donor) of the islets, was induced by four of the five CBV-4 strains. One strain (VD2921) replicated without causing CPE despite high virus titres. One (V89-4557) of the CBV-4 strains always revealed pronounced CPE. Infection by this strain also caused functional impairment that significantly affected insulin response to high glucose at 48 hours post infection (p<0.001). Replication of another CBV-4 strain (JVB) in the islet cells significantly increased the release of insulin compared to non-infected control cells (p<0.001) indicating damage of the beta-cells leading to leakage of insulin.

A novel serological technique: polymerase chain reaction enhanced immunoassay. Application to enterovirus IgM diagnosis

The polymerase chain reaction (PCR) method is a sensitive, specific and rapid technique for virus detection. The principles of a PCR enhanced immunoassay (PIA) are described. The method combines solid phase serological techniques with the PCR, providing a versatile and sensitive method for antibody detection. By linking the antigenicity of virus particles with their content of nucleic acid, the method provides new possibilities for virus serology: for example, antibody specificity can be coupled to viral sequence in patients with chronic infections caused by highly variable viruses such as HIV and HCV. An application of the PIA technique is described for the detection of anti-enterovirus IgM. IgM is captured to anti-human IgM-coated microwell plates. The anti-enterovirus IgM is allowed to bind crude enterovirus antigen. Bound virus is heat denatured and the released RNA is used as a template for reverse transcription PCR (RT-PCR) amplification. Amplicons are detected by hybridisation to an affinity labelled probe in a microwell colorimetric assay. In a pilot study, 18 serum specimens from patients with enterovirus infections were examined. Using a mixture of ten crude enterovirus antigens, the frequency of IgM positivity was 6/18 (33%). Titres between 1/500 and 1/100,000 were recorded. Predominantly type-specific antibodies were detected. The results were compared with a procapsid enterovirus radioimmunoassay (RIA). After further optimisation, the PIA has the potential to be a clinically useful assay for the detection of antiviral antibodies.

Antibody responses to different strains of coxsackie B4 virus in patients with newly diagnosed type I diabetes mellitus or aseptic meningitis

Considerable differences in antibody responses measured by capture-IgM RIA and neutralization tests (NT) were seen in children with newly diagnosed type I (insulin-dependent) diabetes mellitus (IDDM) when five different strains of Coxsackie B4 virus (CBV-4) were used. The IgM positivity of the 160 patients varied between 3.7 and 10.0% (P < 0.05) and with the use of all strains, IgM was found in 13.2%. Matched controls showed a significantly lower frequency (P < 0.05), but there were no apparent differences between the strains, although no IgM was found against two strains. In the NT different results were also obtained in the IDDM children with use of the five strains. However, these results differed considerably from those of the RIA, indicating that different epitopes on the virus were involved. Serum specimens from 75 patients with aseptic meningitis from whom enteroviruses had been isolated, also showed varying IgM frequencies, ranging from 13.3 to 18.7%, but the differences between the strains were different to those found in the IDDM patients. We speculate that only certain strains of a serotype of CBV may be used to distinguish IDDM pathogenesis from that of other diseases.

Indications that maternal coxsackie B virus infection during pregnancy is a risk factor for childhood-onset IDDM

In a population-based setting, we traced serum samples collected at time of birth from 55 mothers whose children later developed insulin-dependent diabetes (IDDM) and matched them pairwise to control subjects who gave birth at the same hospital during the same month. The sera were analysed for IgM antibodies to coxsackie B virus serotypes 2, 3 and 4 (CBV-2, 3 and 4) using a type-specific mu-antibody-capture radioimmunoassay. Despite a decreased power due to the close matching by time of birth we found a significantly higher frequency of CBV-3 IgM at delivery in mothers whose children later became diabetic compared to their matched control subjects. When using the presence of CBV-3 IgM as a risk factor the Mantel-Haenszel odds ratio estimate (95% confidence limits) was 2.57 (1.02; 7.31), p = 0.043. For CBV-2 and CBV-4, respectively no significant difference was found between mothers of patients and control subjects. According to the odds ratio estimate for CBV-3 and the proportion of exposed mothers among patients estimated in this study the aetiological fraction for this risk determinant would be 27%. In conclusion, this study indicates that children of mothers who expressed CBV IgM at delivery are at increased risk for developing childhood onset IDDM. A fetal infection with CBV similar to rubella virus may initiate autoimmunity or cause persistent infection that may lead to progressive beta-cell destruction.

Impaired Ca2+ response to glucose in mouse beta-cells infected with coxsackie B or Echo virus

Five strains of Coxsackie B4 virus and one of Echo 11 virus were tested with regard to their ability to replicate in pancreatic mouse beta-cells and interfere with the alterations of the cytoplasmic Ca2+ concentration ([Ca2+]i) induced by glucose. All strains except one both multiplied and caused cytopathic effect. In a control group 68% of the beta-cells responded to 11 mM glucose with large amplitude oscillations of [Ca2+]i. After inoculation with the infectious strains these oscillations appeared in only 5% of the beta-cells, whereas the non-infectious strain did not modify the glucose effect on [Ca2+]i. Despite the virus interference with the glucose response, [Ca2+]i was increased after depolarization with excessive extracellular K+ and the oscillations were induced in most beta-cells when glucose was combined with the insulin-releasing sulfonylurea tolbutamide.

Stabilization of the antigenicity of coxsackie B procapsids by disoxaril

Disoxaril added to cell cultures infected with coxsackie B virus serotypes 3 or 4 increased the yield and stabilized the antigenicity of the procapsids. In the absence of disoxaril, the procapsids lost their broad antigenicity after a short period of time. Prevention of this loss by disoxaril was observed in radioimmunoassays of IgM in sera from patients infected with various enteroviruses. The procapsids are useful in serological diagnosis of enterovirus infections, and the addition of disoxaril facilitates this technique.

Coxsackie B virus infections in women with miscarriage

To study the possible role of Coxsackie B virus serotypes 1-5 (CBV 1-5) as an etiological factor in miscarriage, 97 women with miscarriage were tested for the presence of CBV-IgM by radioimmunoassays (RIAs) and compared with 113 control women undergoing voluntary interruption of pregnancy in the same gestational week. Of the 80 women with miscarriage before the 13th week of gestation, 34 (42%) had CBV-IgM, whereas 18 of 100 (18%) corresponding control women had these antibodies, a statistically significant difference (P < 0.001). There was no significant difference in CBV-IgM frequency between the women with miscarriage from the 13th through the 27th week and their controls. IgM against CBV 2 predominated, followed by IgM against CBV 5, CBV 4, CBV 3, and CBV 1. Two strains of CBV 5 were used in the RIAs, one (M147) isolated from a woman with miscarriage included in the study and one (V136) isolated in 1971 from a patient with meningitis. When the former strain was used, 13 women with miscarriage and seven control women had IgM, but with use of V136 only two women in each group were IgM positive. CBV 5 was isolated from the placental tissue from more women with miscarriage (6 of 28; 21%), than control women (2 of 21; 10%), but the difference was not statistically significant. No other viruses, except cytomegalovirus from a woman with miscarriage, were isolated.

Increased frequency of coxsackie B virus IgM in women with spontaneous abortion

IgM antibodies to Coxsackie B virus serotypes 1-5 (CBV 1-5) were studied by radioimmunoassay (RIA) of blood samples from women who had undergone a spontaneous abortion or given birth to a stillborn child. Results were compared with those of controls comprising healthy pregnant women who had not suffered such experiences. Among 48 women with abortions, 16 (33%) had CBV-IgM, while among the controls only three of 37 (8%) had these antibodies, a statistically significant difference (P less than 0.025). Among 21 women with a stillborn child, 11 (52%) were CBV-IgM positive, while the corresponding proportion in their controls was four of 18 (22%), a difference which is not statistically significant. It is concluded that CBV may be an important causative agent in spontaneous abortions and possibly also in stillbirths.

High frequency of IgM antibodies to coxsackie B virus in sarcoidosis patients and patients with asbestos-related lesions

By using radioimmunoassay (RIA) for detection of IgM antibodies to Coxsackie B viruses (CBV), the occurrence of these antibodies was investigated in patients with sarcoidosis and asbestos-related lesions. Sixty-one per cent of the patients with sarcoidosis, all patients with benign asbestos pleural effusion, and 67% of those with diffuse asbestos-related pleural thickening showed CBV-IgM. Patients with healed sarcoidosis or pleural plaques were all negative, and among the "healthy" controls seven per cent had CBV-IgM. Thus, there was a high frequency of CBV-IgM in patients with sarcoidosis and in those with asbestos-related diseases. Since the titres could be the effect of an unspecific polyclonal stimulation of the B cells, sera were tested for antibodies to rubella and cytomegalovirus, but without any remarkable results.

Coxsackie B virus IgM in children at onset of type 1 (insulin-dependent) diabetes mellitus: evidence for IgM induction by a recent or current infection

Thirty-five children with newly-diagnosed Type 1 (insulin-dependent) diabetes mellitus and their 47 siblings were investigated for the presence of IgM antibodies to Coxsackie B virus serotypes 1-5 (CBV 1-5) with the aid of mu-antibody-capture radioimmunoassays. When a high cut-off value was used, 16 (46%) diabetic children and 16 (34%) siblings showed CBV-IgM. Of the siblings of diabetic patients positive for CBV-IgM, 11 (44%) were CBV-IgM-positive; the corresponding figure for the siblings of negative patients was five (26%). With a lower cut-off value, leading to a "borderline titre", the frequency of IgM positivity increased in both the patients and siblings. When the borderline titres were included, the number of IgM-positive patients was 19 (54%) and the corresponding number of siblings was 29 (62%). Of the siblings of positive patients, 27 (93%) showed CBV-IgM, and of the siblings of the negative patients, two (11%) were CBV-IgM-positive. Sixteen (89%) siblings of IgM-negative patients remained negative. Regarding the serotypes of CBV to which IgM was directed, CBV 4 was most frequent, followed by serotypes CBV 3, CBV 2, CBV 5 and CBV 1. There was a striking similarity between the individual diabetic child and his or her sibling(s) concerning this specificity of IgM. It is concluded that within most families with a newly-diagnosed diabetic child positive for CBV-IgM the same serotype(s) of the virus circulates and that the intrafamilial spread of virus is considerable. The results strongly indicate that the IgM detected was CBV-specific and caused by a recent or current CBV infection.(ABSTRACT TRUNCATED AT 250 WORDS)