Evidence for molecular mimicry between human T cell epitopes in rotavirus and pancreatic islet autoantigens.

In type 1 diabetes, insulin-producing beta cells in the islets of the pancreas are destroyed by autoreactive T cells. Rotavirus (RV) has been implicated in the pathogenesis of type 1 diabetes. Peptides in VP7, a major immunogenic protein of RV, have high sequence similarity to T cell epitope peptides in the islet autoantigens tyrosine phosphatase-like insulinoma Ag 2 (IA2) and glutamic acid decarboxylase 65 (GAD65). We aimed to educe evidence for the hypothesis that molecular mimicry with RV promotes autoimmunity to islet autoantigens. Peptides in RV and their sequence-similar counterparts in IA2 and GAD65 were assayed for binding to HLA molecules associated with type 1 diabetes and for the ability to elicit T cell proliferative responses in HLA-typed individuals. T cells expanded or cloned to epitopes in IA2 or RV were then tested for cross-reactivity with these epitopes. Peptides in RV-VP7, similar to T cell epitopes in IA2 and GAD65, bound strongly to HLA-DRB1*04 molecules that confer susceptibility to type 1 diabetes and were also T cell epitopes in humans at risk for type 1 diabetes. The proliferative responses of T cells to the similar peptides in RV and islet autoantigens were significantly correlated. T cells expanded to the IA2 epitope could be restimulated to express IFN-gamma by the similar peptide in RV-VP7, and T cell clones generated to this RV-VP7 peptide cross-reacted with the IA2 epitope. Our findings are consistent with the hypothesis that molecular mimicry with RV could promote autoimmunity to islet Ags.

Predictive power of screening for antibodies against insulinoma-associated protein 2 beta (IA-2beta) and zinc transporter-8 to select first-degree relatives of type 1 diabetic patients with risk of rapid progression to clinical onset of the disease: implications for prevention trials.

AIMS/HYPOTHESIS: We investigated whether screening for insulinoma-associated protein (IA-2) beta (IA-2beta) autoantibodies (IA-2betaA) and zinc transporter-8 (ZnT8) autoantibodies (ZnT8A) improves identification of first-degree relatives of type 1 diabetic patients with a high 5-year disease risk, which to date has been based on assays for insulin autoantibodies (IAA), GAD autoantibodies (GADA) and IA-2 autoantibodies (IA-2A). METHODS: IA-2betaA and ZnT8A (using a ZnT8 carboxy-terminal hybrid construct, CW-CR, carrying 325Arg and 325Trp) were determined by radiobinding assay in 409 IAA(+), GADA(+) and/or IA-2A(+) siblings or offspring (<40 years) of type 1 diabetic patients consecutively recruited by the Belgian Diabetes Registry. The median (interquartile range) age of the first-degree relatives was 12 (6-19) years. RESULTS: Of the first-degree relatives, 24% were IA-2A(+) (n = 97), 14% (n = 59) IA-2betaA(+) and 20% (n = 80) ZnT8A(+). IA-2betaA and ZnT8A were significantly (p < 0.001) associated with IA-2A and prediabetes (n = 86); in IA-2A(-) first-degree relatives (n = 312) the presence of IA-2betaA and ZnT8A was associated with an increased progression rate to diabetes (p < 0.001). Positivity for IA-2A and/or ZnT8A emerged as the most sensitive combination of two markers to identify first-degree relatives with a 5-year progression rate to diabetes of 45% (survival analysis) and as strongest predictor of diabetes (Cox regression analysis). Omission of first-degree relatives protected by HLA-DQ genotypes or maternal diabetes reduced the group to be followed from n = 409 to n = 246 (40%) with minor loss in the number of prediabetic IA-2A(+) or ZnT8A(+) first-degree relatives identified (n = 3). CONCLUSIONS/INTERPRETATION: IA-2A(+) and/or ZnT8A(+) first-degree relatives may be the participants of choice in future secondary prevention trials with immunointervention in relatives of type 1 diabetic patients.

Regulatory T cells prevent transfer of type 1 diabetes in NOD mice only when their antigen is present in vivo.

Regulatory T cells (Tregs) can potentially be used as tools to suppress pathogenic T cells in autoimmune diseases such as type 1 diabetes. For use in therapy it is critically important to determine whether suppression by Tregs requires a population specific for the target of autoimmunity, such as pancreatic beta cells in type 1 diabetes. Current reports in the NOD mouse model of type 1 diabetes are in conflict as to whether suppression of disease by Tregs is Ag-dependent. We have addressed this question by evaluating the effects of islet-specific TGF-beta-induced Tregs in recipient mice in which the Treg Ag is either present or absent. Our data show that Treg numbers in pancreas are reduced in the absence of Ag and that there are Ag-dependent differences in the effects of Tregs on pathogenic T cells in the pancreas. By examining protection from diabetes induced by T cell transfer, we have clearly demonstrated that Tregs suppress only in the presence of their Ag and not in mice in which the islets lack the Treg Ag. Our results also suggest that in sufficiently large populations of polyclonal Tregs, there will be adequate numbers of islet-specific Tregs to suppress diabetes.

Genome-Wide Mapping of 5mC and 5hmC Identified Differentially Modified Genomic Regions in Late-Onset Severe Preeclampsia: A Pilot Study.

Preeclampsia (PE) is a leading cause of perinatal morbidity and mortality. However, as a common form of PE, the etiology of late-onset PE is elusive. We analyzed 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) levels in the placentas of late-onset severe PE patients (n = 4) and normal controls (n = 4) using a (hydroxy)methylated DNA immunoprecipitation approach combined with deep sequencing ([h]MeDIP-seq), and the results were verified by (h)MeDIP-qPCR. The most significant differentially methylated regions (DMRs) were verified by MassARRAY EppiTYPER in an enlarged sample size (n = 20). Bioinformatics analysis identified 714 peaks of 5mC that were associated with 403 genes and 119 peaks of 5hmC that were associated with 61 genes, thus showing significant differences between the PE patients and the controls (>2-fold, p<0.05). Further, only one gene, PTPRN2, had both 5mC and 5hmC changes in patients. The ErbB signaling pathway was enriched in those 403 genes that had significantly different 5mC level between the groups. This genome-wide mapping of 5mC and 5hmC in late-onset severe PE and normal controls demonstrates that both 5mC and 5hmC play epigenetic roles in the regulation of the disease, but work independently. We reveal the genome-wide mapping of DNA methylation and DNA hydroxymethylation in late-onset PE placentas for the first time, and the identified ErbB signaling pathway and the gene PTPRN2 may be relevant to the epigenetic pathogenesis of late-onset PE.

Aberrant Expression of proPTPRN2 in Cancer Cells Confers Resistance to Apoptosis.

The protein tyrosine phosphatase receptor PTPRN2 is expressed predominantly in endocrine and neuronal cells, where it functions in exocytosis. We found that its immature isoform proPTPRN2 is overexpressed in various cancers, including breast cancer. High proPTPRN2 expression was associated strongly with lymph node-positive breast cancer and poor clinical outcome. Loss of proPTPRN2 in breast cancer cells promoted apoptosis and blocked tumor formation in mice, whereas enforced expression of proPTPRN2 in nontransformed human mammary epithelial cells exerted a converse effect. Mechanistic investigations suggested that ProPTPRN2 elicited these effects through direct interaction with TRAF2, a hub scaffold protein for multiple kinase cascades, including ones that activate NF-κB. Overall, our results suggest PTPRN2 as a novel candidate biomarker and therapeutic target in breast cancer.