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Enterovirus-induced changes in explanted human islet of Langerhans resemble findings in islets of fulminant and conventional type 1 diabetes
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Clinical Immunology.
University of Tampere, School of Medicine, Tampere, Finland ,Fimlab Ltd, Pirkanmaa Hospital District, Finland.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Clinical Immunology.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Hypothesis: Fulminant Type 1 diabetes is a unique subtype of T1D, mostly reported in the Japanese population, which is characterized by extensive beta cell death already at onset, often without any insulitis. Enterovirus (EV) infections are associated with the etiology of both fulminant and conventional T1D. However the causative mechanism is not known for any of these diseases. EVs capability to cause lytic vs non-lytic infection in explanted human islets may have implications on the pathogenesis of these two types of T1D.

Aim: To study the effect of infection of explanted human pancreatic islets with lytic (CBV-1) and non-lytic (CBV-4) Coxsackie B virus strains on cytopathic effect/islet disintegration and to what extent genes involved in viral sensing, antiviral defense and encoding of islet auto-antigens are affected by the viral replication. Also, to compare these findings with the findings reported in fulminant and conventional T1D.

Methods: Degree of cytopathic effect/islet disintegration was studied and viral replication was measured. Genes involved in viral sensing (NOD2, TLR7 and TLR4), antiviral pathways (OAS2, MX1, PKR, and IRF7), genes coding for known islet auto antigens (GAD65, ZNT8) and the islet hormones, insulin and glucagon, were studied. Mock-infected explanted islet served as controls.

Results: All CBV strains replicated in the explanted islets but only the CBV-1 strains caused cytopathic effect/islet cell disintegration. Infection with all CBV strains resulted in the induction of genes encoding OAS2 and MX1. In contrast, mRNA expression levels of the gene encoding insulin was reduced. The gene encoding PKR was induced by one of the lytic strains (CBV-1-11) and also by the non-lytic CBV4 strain, while the mRNA expression levels of genes encoding glucagon, NOD2, TLR7, TLR4, MCL1, GAD65 and ZNT8 were not significantly affected.

National Category
Endocrinology and Diabetes Microbiology
URN: urn:nbn:se:uu:diva-283281OAI: oai:DiVA.org:uu-283281DiVA: diva2:918882
Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2016-06-01
In thesis
1. Studies of Enterovirus Infection and Induction of Innate Immunity in Human Pancreatic Cells
Open this publication in new window or tab >>Studies of Enterovirus Infection and Induction of Innate Immunity in Human Pancreatic Cells
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Several epidemiological and clinical studies have indicated a possible role of Enterovirus (EV) infection in type 1 diabetes (T1D) development. However, the exact casual mechanism of these viruses in T1D development is not known. The aim of this thesis is to study various EVs that have been shown to differ in their immune phenotype, lytic ability, association with induction of islet autoantibodies, ability to replicate, cause islet disintegration and induce innate antiviral pathways in infected pancreatic cells in vitro. Furthermore, EV presence and pathogenic process in pancreatic tissue and isolated islets of T1D patients was also studied.

Studies in this thesis for first time show the detection of EV RNA and protein in recent onset live T1D patients supporting the EV hypothesis in T1D development. Further all EV serotypes studied were able to replicate in islets, causing variable amount of islet disintegration ranging from extensive islet disintegration to not affecting islet morphology at all. However, one of the EV serotype replicated in only two out of seven donors infected, highlighting the importance of individual variation between donors. Further, this serotype impaired the insulin response to glucose stimulation without causing any visible islet disintegration, suggesting that this serotype might impaired the insulin response by inducing a functional block. Infection of human islets with the EV serotypes that are differentially associated with the development of islet autoantibodies showed the islet cell disintegration that is comparable with their degree of islet autoantibody seroconversion. Suggesting that the extent of the epidemic-associated islet autoantibody induction may depend on the ability of the viral serotypes to damage islet cells. Furthermore, one of the EV strains showed unique ability to infect and replicate both in endo and exocrine cells of the pancreas. EV replication in both endo and exocrine cells affected the genes involved in innate and antiviral pathways and induction of certain genes with important antiviral activity significantly varied between different donors. Suggesting that the same EV infection could result in different outcome in different individuals. Finally, we compared the results obtained by lytic and non lytic EV strains in vitro with the findings reported in fulminant and slowly progressing autoimmune T1D and found some similarities. In conclusion the results presented in this thesis further support the role of EV in T1D development and provide more insights regarding viral and host variation.  This will improve our understanding of the possible causative mechanism by EV in T1D development.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 63 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1223
Type 1 Diabetes, Enterovirus, Innate Immunity, Pancreas
National Category
Microbiology in the medical area
urn:nbn:se:uu:diva-284370 (URN)978-91-554-9572-5 (ISBN)
Public defence
2016-06-07, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, 752 37 Uppsala, Uppsala, 09:00 (English)
Available from: 2016-05-13 Created: 2016-04-18 Last updated: 2016-06-01

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