Aims/hypothesis: The Diabetes Virus Detection (DiViD) study has suggested the
presence of low-grade enteroviral infection in pancreatic tissue collected from six of six
live adult patients newly diagnosed with type 1 diabetes. The present study aimed to
compare the gene and protein expression of selected virally induced pathogen ...
Aims/hypothesis: The Diabetes Virus Detection (DiViD) study has suggested the
presence of low-grade enteroviral infection in pancreatic tissue collected from six of six
live adult patients newly diagnosed with type 1 diabetes. The present study aimed to
compare the gene and protein expression of selected virally induced pathogen recognition
receptors and interferon stimulated genes in islets from these newly diagnosed type 1
diabetes (DiViD) subjects vs age-matched non-diabetic (ND) controls.
Methods: RNA was extracted from laser-captured islets and Affymetrix Human Gene 2.0
ST arrays used to obtain gene expression profiles. Lists of differentially expressed genes
were subjected to a data-mining pipeline searching for enrichment of canonical pathways,
KEGG pathways, Gene Ontologies, transcription factor binding sites and other upstream
regulators. In addition, the presence and localisation of specific viral response proteins
(PKR, MxA and MDA5) were examined by combined immunofluorescent labelling in
sections of pancreatic tissue.
Results: The data analysis and data mining process revealed a significant enrichment of
gene ontologies covering viral reproduction and infectious cycles; peptide translation,
elongation and initiation, as well as oxidoreductase activity. Enrichment was identified in
the KEGG pathways for oxidative phosphorylation; ribosomal and metabolic activity;
antigen processing and presentation and in canonical pathways for mitochondrial
dysfunction, oxidative phosphorylation and EIF2 signaling. Protein Kinase R (PKR)
expression did not differ between newly diagnosed type 1 diabetes and ND islets at the
level of total RNA, but a small subset of b-cells displayed markedly increased PKR protein
levels. These PKR+ b-cells correspond to those previously shown to contain the viral
protein, VP1. RNA encoding MDA5 was increased significantly in newly diagnosed type 1
diabetes islets, and immunostaining of MDA5 protein was seen in a- and certain b-cells in both newly diagnosed type 1 diabetes and ND islets, but the expression was increased in
b-cells in type 1 diabetes. In addition, an uncharacterised subset of synaptophysin
positive, but islet hormone negative, cells expressed intense MDA5 staining and these
were more prevalent in DiViD cases. MxA RNA was upregulated in newly diagnosed type 1
diabetes vs ND islets and MxA protein was detected exclusively in newly diagnosed type 1
diabetes b-cells.
Conclusion/interpretation: The gene expression signatures reveal that pathways
associated with cellular stress and increased immunological activity are enhanced in
islets from newly diagnosed type 1 diabetes patients compared to controls. The increases
in viral response proteins seen in b-cells in newly diagnosed type 1 diabetes provide clear
evidence for the activation of IFN signalling pathways. As such, these data strengthen the
hypothesis that an enteroviral infection of islet b-cells contributes to the pathogenesis of
type 1 diabetes.
