Preproinsulin-specific CD8+ T cells secrete IFNgamma in human type 1 diabetes

Gene expression pattern in severely progressing covid-19 patients is related to diabetes mellitus type 1: A functional annotation analysis

Aims

The aim of this study was to extract the signaling mediators or biological pathways that link covid-19 to other diseases such as type 1 diabetes mellitus (T1DM).

Methods

Microarray data of covid-19 (GSE164805) was extracted from Gene Expression Omnibus (GEO) and analyses were performed by R package and GEO2R. Functional enrichment analysis was done to extract enriched molecular pathways (MP), biological process (BP) and molecular function (MF). Then commonly up- and down-regulated genes in covid-19 and T1DM were extracted by comparing deferentially expressed genes (DEGs) of GSE164805 and GSE9006.

Results

Down-regulated DEGs in the severely progressing covid-19 patients (SPCP) had a link to T1DM. Major histocompatibility system (MHC) class II, gamma interferon (IFNγ), and IL-1B were enriched in extracted pathway that leads to T1DM. In addition, comparing extracted DEGs from GSE164805 and GSE9006 indicated that MTUS1, EGR1 and EGR3 are the genes that are up-regulated in both SPCP and T1DM.

Conclusion

The findings of this study indicate that coincidence of SARS-COV-2 infection and T1DM may increase the severity of both diseases. Although covid-19 reduced the T cell mediated immune response, but increased mediators of T-cell signaling pathway such as IL-1 in both diseases. This could potentiate the inflammation response and worsens the severity of covid-19 cytokine storm or increase the resistance to insulin.

A Single L/D-Substitution at Q4 of the mInsA2-10 Epitope Prevents Type 1 Diabetes in Humanized NOD Mice

Autoreactive CD8⁺ T cells play an indispensable key role in the destruction of pancreatic islet β-cells and the initiation of type 1 diabetes (T1D). Insulin is an essential β-cell autoantigen in T1D. An HLA-A*0201-restricted epitope of insulin A chain (mInsA_2-10) is an immunodominant ligand for autoreactive CD8⁺ T cells in NOD.β2m^null .HHD mice. Altered peptide ligands (APLs) carrying amino acid substitutions at T cell receptor (TCR) contact positions within an epitope are potential to modulate autoimmune responses via triggering altered TCR signaling. Here, we used a molecular simulation strategy to guide the generation of APL candidates by substitution of L-amino acids with D-amino acids at potential TCR contact residues (positions 4 and 6) of mInsA_2-10, named mInsA_2-10DQ4 and mInsA_2-10DC6, respectively. We found that administration of mInsA_2-10DQ4, but not DC6, significantly suppressed the development of T1D in NOD.β2m^null .HHD mice. Mechanistically, treatment with mInsA_2-10DQ4 not only notably eliminated mInsA_2-10 autoreactive CD8⁺ T cell responses but also prevented the infiltration of CD4⁺ T and CD8⁺ T cells, as well as the inflammatory responses in the pancreas of NOD.β2m^null.HHD mice. This study provides a new strategy for the development of APL vaccines for T1D prevention.

Narrowing in on the anti-β cell-specific T cells: looking 'where the action is'

PURPOSE OF REVIEW

By necessity, the vast majority of information we have on autoreactive T cells in human type 1 diabetes (T1D) has come from the study of peripheral blood of donors with T1D. It is not clear how representative the peripheral autoreactive T-cell repertoire is of the autoreactive T cells infiltrating the islets in T1D. We will summarize and discuss what is known of the immunohistopathology of insulitis, the T-cell receptor repertoire expressed by islet-infiltrating T cells, and the autoreactivity and function of islet-infiltrating T cells in T1D.

RECENT FINDINGS

Recovery and analysis of live, islet-infiltrating T cells from the islets of cadaveric donors with T1D revealed a broad repertoire and proinflammatory phenotype of CD4 T-cell autoreactivity to peptide targets from islet proteins, including proinsulin, as well as CD4 T-cell reactivity to a number of post-translationally modified peptides, including peptides with citrullinations and hybrid insulin peptide fusions. Islet-infiltrating CD8 T cells were also derived and required further isolation and characterization.

SUMMARY

The recovery of live, islet-infiltrating T cells from donors with T1D, reactive with a broad range of known targets and post-translationally modified peptides, allows for the specific functional analysis of islet-infiltrating T cells for the development of antigen-specific immunotherapies.

Viruses and cytotoxic T lymphocytes in type 1 diabetes

Histopathological studies on pancreas tissues from individuals with recent-onset type 1 diabetes (T1D) consistently find that CD8 T cells substantially contribute to the formation of islet lesions. CD8 T cells reactive against islet-associated antigens can also be found in blood samples from T1D patients. Mechanistic studies on the pathogenic role of this T cell subset have mostly focused on two animal models, i.e., the non-obese diabetic mouse and the virally induced rat insulin promoter-lymphocytic choriomeningitis virus model. Data were obtained in support of a role for viral infection in expanding a population of diabetogenic cytotoxic T lymphocytes. In view of the theorized association of viral infection with initiation of islet autoimmunity and progression to clinically overt disease, CD8 T cells thus represent an attractive target for immunotherapy. We will review here arguments in favor of a pivotal role for CD8 T cells in driving T1D development and speculate on etiologic agents that may provoke their aberrant activation.

Prediction of HLA class I-restricted T-cell epitopes of islet autoantigen combined with binding and dissociation assays

Identification of cognate peptides recognized by human leucocyte antigen (HLA)/T cell receptor (TCR) complex provides insight into the pathogenic process of type 1 diabetes (T1D). We hypothesize that HLA-binding assays alone are inadequate metrics for the affinity of peptides. Zinc transporter-8 (ZnT8) has emerged in recent years as a novel, major, human autoantigen. Therefore, we aim to identify the HLA-A2-restricted ZnT8 epitopes using both binding and dissociation assays. HLA class I peptide affinity algorithms were used to predict candidate ZnT8 peptides that bind to HLA-A2. We analyzed 15 reported epitopes of seven β-cell candidate autoantigens and eight predicted candidate ZnT8 peptides using binding and dissociation assays. Using IFN-γ ELISpot assay, we tested peripheral blood mononuclear cells (PBMCs) from recent-onset T1D patients and healthy controls for reactivity to seven reported epitopes and eight candidate ZnT8 peptides directly ex vivo. We found five of seven recently reported epitopes in Chinese T1D patients. Of the eight predicted ZnT8 peptides, ZnT8(153-161) had a strong binding affinity and the lowest dissociation rate to HLA-A*0201. We identified it as a novel HLA-A*0201-restricted T-cell epitope in three of eight T1D patients. We conclude that ZnT8(153-161) is a novel HLA-A*0201-restricted T-cell epitope. We did not observe a significant correlation (P = 0.3, R = - 0.5) between cytotoxic T cell (CTL) response and peptide/HLA*0201 complex stability. However, selection of peptides based on affinity and their dissociation rate may be helpful for the identification of candidate CTL epitopes. Thus, we can minimize the number of experiments for the identification of T-cell epitopes from interesting antigens.

High affinity binding of hydrophobic and autoantigenic regions of proinsulin to the 70 kDa chaperone DnaK

BACKGROUND

Chaperones facilitate proper folding of peptides and bind to misfolded proteins as occurring during periods of cell stress. Complexes of peptides with chaperones induce peptide-directed immunity. Here we analyzed the interaction of (pre)proinsulin with the best characterized chaperone of the hsp70 family, bacterial DnaK.

RESULTS

Of a set of overlapping 13-mer peptides of human preproinsulin high affinity binding to DnaK was found for the signal peptide and one further region in each proinsulin domain (A- and B-chain, C-peptide). Among the latter, peptides covering most of the B-chain region B11-23 exhibited strongest binding, which was in the range of known high-affinity DnaK ligands, dissociation equilibrium constant (K'd) of 2.2 ± 0.4 μM. The B-chain region B11-23 is located at the interface between two insulin molecules and not accessible in insulin oligomers. Indeed, native insulin oligomers showed very low DnaK affinity (K'd 67.8 ± 20.8 μM) whereas a proinsulin molecule modified to prevent oligomerization showed good binding affinity (K'd 11.3 ± 7.8 μM).

CONCLUSIONS

Intact insulin only weakly interacts with the hsp70 chaperone DnaK whereas monomeric proinsulin and peptides from 3 distinct proinsulin regions show substantial chaperone binding. Strongest binding was seen for the B-chain peptide B 11-23. Interestingly, peptide B11-23 represents a dominant autoantigen in type 1 diabetes.

The sentinel role of CD8 T cells in regulating CD4 T cell responses to proinsulin in beta-islet cell autoimmunity

Circulating CD4 T cells specific for peptide epitopes of proinsulin and other autoantigens are markers of autoimmune beta cell destruction in type 1 diabetes, while the role of CD8 T cells is still largely unknown. Here we show that CD8 T cells of a diabetic patient--after rechallange with proinsulin peptides--secrete IFNgamma and granzyme B, markers of their effector capacity. On the other hand, CD8 T cells of the same patient in a "cross-talk" with proinsulin-specific CD4 T cells suppress their proliferation. If confirmed in larger numbers of subjects with beta-islet cell autoimmunity, these results may help us to understand the role of CD8 cells in disease progression and extend our knowledge of disease pathogenesis.

Type 1 diabetes mellitus in a child with phenobarbital hypersensitivity syndrome

OBJECTIVE

To report a case of type 1 diabetes mellitus (T1DM) in a child with phenobarbital hypersensitivity syndrome with an emphasis on the clinical presentation, diagnostic modalities and treatment options.

CASE SUMMARY

A 5-yr-old girl developed fever, rash and hepatic inflammation after receiving phenobarbital. Infection and connective tissue diseases were excluded and an adverse event following phenobarbital administration [anticonvulsant hypersensitivity syndrome (AHS)] was considered. Clinical manifestation was somewhat improved after systemic hydrocortisone and other antiallergic drugs were administrated. However, polyuria, polydipsia, dehydration, severe metabolic acidosis with increased anion gap and hyperglucosemia were found about 4 weeks after stopping phenobarbital. Increased blood ketone and glycosylated hemoglobin (HbA1c), and decreased blood insulin and C-peptide confirmed the diagnosis of T1DM. Insulin was used and gamma-immunoglobulin was administered on the 25th day after admission. Since then, clinical symptoms and signs improved significantly and the patient was discharged on the 45th day after admission. Postdischarge course was uneventful and the patient is well with sequential HbA1c of 7.3% 1 month after discharge.

CONCLUSIONS

AHS should be suspected in patients who develop unexplained systemic manifestations following exposure to aromatic antiepileptics, including phenobarbital. The timely recognition and treatment with corticosteroids and immunoglobulin is required and useful. The potential damage of beta-cells should be considered in patients with AHS.

Human CD8 responses to a complete epitope set from preproinsulin: implications for approaches to epitope discovery

PURPOSE

In this study, we explored the breadth of CD8 T cell reactivity to preproinsulin (PPI) in type 1 diabetes.

MATERIALS AND METHODS

We tested a complete peptide set in pools covering all 406 potential 8-11mer epitopes of PPI and 61 algorithm-predicted human leukocyte antigen (HLA)-A2-specific epitopes (15 pools) from islet-specific glucose-6-phophatase catalytic subunit-related protein (IGRP), using a CD8-specific granzyme B enzyme-linked immunosorbent spot assay.

RESULTS

Responses were seen to 64 of the 102 PPI pools in two or more newly diagnosed patients (63%) compared to 11 pools in the control subjects (11%, p < 0.0001, Fisher's exact test). We identified five pools containing 20 peptides, which distinguished patients from control subjects, most of which had predicted low-affinity binding to HLA class I molecules. In contrast, fewer (5 of 15 = 33%) IGRP peptide pools, selected by higher binding affinity for HLA-A2 (present in seven of eight patients and five of seven control subjects), stimulated responses in two or more patients, and none stimulated responses in more than two control subjects (p = 0.042, Fisher's exact test).

CONCLUSION

Thus, we conclude that CD8 T cell reactivity to PPI in patients with type 1 diabetes can be much broader than shown previously and more diverse than seen in control subjects. Furthermore, responses were often stimulated by peptides with low predicted HLA-binding affinities.

The Development and Application of HLA Tetramers in the Detection, Characterization and Therapy of Type 1 Diabetes Mellitus

Islet antigens are presented by human leukocyte antigen (HLA) class I and II molecules and are recognized by CD8(+) and CD4(+) autoreactive T cells in type 1 diabetic individuals. Early identification of individuals at risk for the disease by detection of these antigens and the autoreactive cells themselves is essential for understanding pathogenesis and for intervention at an early stage to prevent ongoing beta-cell destruction. However, the methods of identifying autoimmune development at an early stage have appeared to be limited because of the heterogeneity of the disease. The appearance of autoantibodies in preclinical type 1 diabetes mellitus (T1DM) does not follow specific patterns and depends on patient characteristics such as age. Also, results obtained with cytokine assays revealed that the number of islet antigen-responsive T cells present in the pool of peripheral blood mononuclear cells (PBMC) of non-diabetic individuals is highly variable and can be similar to that assayed in diabetics. Therefore, new identification and detection methods are needed. In this context, the use of HLA epitopes to generate stable HLA epitope tetramers has recently proved to be a promising approach to the detection of autoreactive T cells in antigen-stimulated PBMC cultures from diabetic and pre-diabetic subjects. HLA class II tetramers have been found to be capable not only of detecting TCRalphabeta of different avidities for a common ligand, e.g. GAD65(555-567(mimitope)), but also of inducing apoptosis in lymphocytes with high TCRalphabeta avidity for this ligand. This observation even opens up a potential application of HLA class II tetramers as therapeutic agents for immune intervention in T1DM.

Suberosin inhibits proliferation of human peripheral blood mononuclear cells through the modulation of the transcription factors NF-AT and NF-kappaB

BACKGROUND AND PURPOSE

Extracts of Plumbago zeylanica containing suberosin exhibit anti-inflammatory activity. We purified suberosin from such extracts and studied its effects on a set of key regulatory events in the proliferation of human peripheral blood mononuclear cells (PBMC) stimulated by phytohemagglutinin (PHA).

EXPERIMENTAL APPROACH

Proliferation of PBMC in culture was measured by uptake of 3H-thymidine; production of cytokines and cyclins by Western blotting and RT-PCR. Transcription factors NF-AT and NF-kappaB were assayed by immunocytochemistry and EMSA.

KEY RESULTS

Suberosin suppressed PHA-induced PBMC proliferation and arrested cell cycle progression from the G1 transition to the S phase. Suberosin suppressed, in activated PBMC, transcripts of interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and cyclins D3, E, A, and B. DNA binding activity and nuclear translocation of NF-AT and NF-kappaB induced by PHA were blocked by suberosin. Suberosin decreased the rise in intracellular Ca2+ concentration ([Ca2+]i) in PBMC stimulated with PHA. Suberosin did not affect phosphorylation of p38 and JNK but did reduce activation of ERK in PHA-treated PBMC. Pharmacological inhibitors of NF-kappaB, NF-AT, and ERK decreased expression of mRNA for the cyclins, IL-2, and IFN-gamma and cell proliferation in PBMC activated by PHA.

CONCLUSIONS AND IMPLICATIONS

The inhibitory effects of suberosin on PHA-induced PBMC proliferation, were mediated, at least in part, through reduction of [Ca2+]i, ERK, NF-AT, and NF-kappaB activation, and early gene expression in PBMC including cyclins and cytokines, and arrest of cell cycle progression in the cells. Our observations provide an explanation for the anti-inflammatory activity of P. zeylanica.

T cell epitope mapping study with insulin overlapping peptides using ELISPOT assay in Japanese children and adolescents with type 1 diabetes

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease. Insulin seems to be a critical antigen recognized by autoreactive T cells. In this study, we performed T cell epitope mapping of insulin using serial overlapping peptides in Japanese patients with T1D. Serial overlapping insulin peptides comprising 23 peptides, which were each 15-amino acid long, were prepared based on insulin sequence. Cytokine secretion from peripheral T cells against these peptides was studied by enzyme-linked immunospot (ELISPOT) assay in 18 patients with recent-onset T1D and 12 patients with established T1D, and compared with 17 healthy control subjects. In ELISPOT assay, IFN-gamma-secreting T cells, but not IL-4, against several insulin peptides were observed in 77.8% of patients with recent-onset T1D, 50.0% of patients with established T1D, and 0% of healthy control subjects. All epitopes recognized by T cells were identified in the B-chain of insulin. The most frequent epitope existed at the B10-24 region (9/18), followed by B1-15 and B11-25 regions (6/18, each), with B4-18, B9-23, and B12-26 identified in some patients. These data did not correlate with insulin autoantibodies or HLA-DRB1 of the patients. This is the first report of T cell epitope mapping using one amino acid serial overlapping peptides of insulin in T1D. ELISPOT assay revealed the frequent existence of insulin peptide-specific T cells in patients with recent-onset and established T1D. The T cell epitopes of insulin were similar but not identical in our cohort, which probably explains the difficulty encountered in prevention of human T1D by using insulin.