Characterization of immune response to novel HLA-A2-restricted epitopes from zinc transporter 8 in type 1 diabetes

Two-pronged approach: Therapeutic effect of biological scaffold combined with immune intervention and β-cell replacement on type 1 diabetic mice

AIMS

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by β-cell damage and absolute insulin deficiency. We consider combining immune intervention and β-cell replacement by biological scaffold to treat T1DM. Zinc transporter 8 (ZnT8) is known to be a pancreatic islet-specific autoantigen. Studies have shown that ZnT8(107-115)/HLA-A2 dimers can be used as antigen-specific immunosuppressants for T1DM. Mesenchymal stem cells (MSCs) can be induced to differentiate into insulin-producing cells (IPCs) under certain conditions in vitro. In recent years, the development of biomaterials has provided a more suitable three-dimensional microenvironment for cell transplantation. Our research group previously prepared gelatin/polylactic acid (PLLA/G) nanofiber scaffold by electrospinning technology, fixed GLP-1 analogues on the scaffold by surface modification with polydopamine (pDA) and confirmed the scaffold can promote bone mesenchymal stem cells (BMSCs) proliferation and improve cell survival rate. In addition, the scaffold can promote the differentiation of BMSCs into IPCs. Subsequently, ZnT8(107-115)/HLA-A2 dimer was constructed and loaded on the scaffold and confirmed the scaffold loaded with immunosuppressants can inhibit the proliferation and cytotoxicity of specific CD8+ T cells in vitro. This study used the above scaffold to co-load ZnT8(107-115)/HLA-A2 dimer and IPCs and implanted the scaffold into T1DM mice to study the blood glucose control and immunomodulatory effects on T1DM.

MATERIALS AND METHODS

First, the PLLA/G scaffold was modified with pDA and fixed with Liraglutide (LIR) to obtain the PLLA/G-pDA-LIR scaffold. Rat BMSCs were loaded on the scaffold and the 'three-step induction method' was used to induce differentiation in vitro. The insulin expression of IPCs was detected by Dithizone (DTZ) staining, glucose stimulate insulin secretion (GSIS) in vitro and intraperitoneal glucose tolerance test (IPGTT) in vivo. Then, non obese diabetes mice were modelled with T1DM and randomly divided into 5 groups. Blank control group was not treated; negative control group underwent sham surgery; positive control group was injected with IPCs through tail vein; single load scaffold group was subcutaneously transplanted with PLLA/G-pDA-LIR scaffold loaded with IPCs; double load scaffold group was subcutaneously transplanted with PLLA/G-pDA-LIR scaffold loaded with IPCs and ZnT8(107-115)/HLA-A2 dimer. Blood glucose and body weight were measured weekly before and after transplantation. At 2, 4 and 6 W after transplantation, some mice were taken from each group to detect serum insulin and C-peptide, spleen lymphocyte subsets and Tregs and pancreatic Th1/Th2 cell inflammatory factors.

RESULTS

The results of insulin expression in induced differentiated IPCs show that cells with insulin expression can be obtained through the "three-step induction method", and transplanting IPCs can effectively reduce blood glucose and improve glucose tolerance. Compared with non-scaffold induced IPCs, fixing Liraglutide scaffolds can improve the insulin expression level of IPCs and promote the induction of differentiation. The results after scaffold transplantation showed that compared with the positive control group and the single load scaffold group, the blood glucose was significantly reduced, and the serum insulin and C-peptide were significantly increased and lasted longer. In addition, the pathogenic T cells and inflammatory factors in the double load scaffold group were significantly reduced, and Tregs and anti-inflammatory factors were significantly increased.

CONCLUSIONS

The results show that the biological scaffold with IPCs and ZnT8(107-115)/HLA-A2 dimers has the dual functions of controlling blood glucose and regulating immunity, and may effectively treat T1DM.

Pivotal epitopes for islet antigen-specific CD8+ T cell detection improve classification of suspected type 1 diabetes with the HLA-A*0201 allele

A proportion of patients with new-onset diabetes share similar symptoms with type 1 diabetes (T1D) patients but they are negative for islet antigen-specific autoantibodies. This study was to develop an islet antigen-specific CD8+ T-cell assay to provide autoimmune evidence regarding these "suspected" T1D patients. HLA-A*0201 individuals with autoAbs+ T1D, autoAbs- suspected T1D, and type 2 diabetes, along with HLA-A*0201 healthy controls were recruited. Using interferon-γ enzyme-linked immunospot assays, the percentages of participants in each group with various islet antigen-specific CD8+ T cells were determined. Sixteen out of the 28 islet antigen-specific epitopes tested were T1D specific, meaning that there was a significantly (P < 0.05) greater epitope positivity rate in the autoAbs+ T1D cohort than in the healthy controls. Using a cutoff value of two positive epitopes, the 16-epitope panel led to a sensitivity of 75.0% and a specificity of 94.4% regarding the autoAbs+ T1D patients. Even when using an optimized five-epitope panel, the results were highly accurate. Notably, in the application phase of the study, 77.8% of a new cohort of autoAbs- suspected T1D patients exhibited positivity when using the five-epitope optimized panel. This highly accurate method, especially for pediatric patients, will improve clinical diagnosis and etiological classification of autoimmune T1D.

Update on the ZNT8 epitope and its role in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is an organ-specific chronic autoimmune disease mediated by autoreactive T cells. ZnT8 is a pancreatic islet-specific zinc transporter that is mainly located in β cells. It not only participates in the synthesis, storage and secretion of insulin but also maintains the structural integrity of insulin. ZnT8 is the main autoantigen recognized by autoreactive CD8+ T cells in children and adults with T1D. This article summarizes the latest research results on the T lymphocyte epitope and B lymphocyte epitope of ZnT8 in the current literature. The structure and expression of ZnT8, the role of ZnT8 in insulin synthesis and its role in autoimmunity are reviewed. ZnT8 is the primary autoantigen of T1D and is specifically expressed in pancreatic islets. Thus, it is one of biomarkers for the diagnosis of T1D. It has broad prospects for further research on immunomodulators for the treatment of T1D.

Vaccine for Diabetes-Where Do We Stand?

Diabetes is an endocrinological disorder with a rapidly increasing number of patients globally. Over the last few years, the alarming status of diabetes has become a pivotal factor pertaining to morbidity and mortality among the youth as well as middle-aged people. Current developments in our understanding related to autoimmune responses leading to diabetes have developed a cause for concern in the prospective usage of immunomodulatory agents to prevent diabetes. The mechanism of action of vaccines varies greatly, such as removing autoreactive T cells and inhibiting the interactions between immune cells. Currently, most developed diabetes vaccines have been tested in animal models, while only a few human trials have been completed with positive outcomes. In this review, we investigate the undergoing clinical trial studies for the development of a prototype diabetes vaccine.

Fulminant type 1 diabetes patients display high frequencies of IGRP-specific type 1 CD8+ T cells

The role of cellular autoimmunity in the pathogenesis of fulminant type 1 diabetes (FT1D) remains largely unknown. In this study, we performed an integrated assay using peripheral blood mononuclear cells to determine the islet antigen-specific CD8+ T cell responses in FT1D and compare the responses among acute-onset T1D (AT1D) and slowly progressive T1D (SP1D). IGRP- and ZnT8-specific IL-6, G-CSF, and TNF-α responses were significantly upregulated in patients with FT1D, while IGRP- and ZnT8-specific IP-10 responses were significantly upregulated in patients with AT1D than in non-diabetics (ND). Furthermore, the frequencies of IGRP-specific type 1 CD8+ cytotoxic T (Tc1) cells were significantly higher in the FT1D group than in the ND, SP1D, and AT1D groups. Additionally, IGRP-specific Tc1 cells were more abundant in the FT1D with HLA-A2 group than in the FT1D without A2 group. In conclusion, our study suggests that IGRP-specific CD8+ T cells significantly contribute to the pathogenesis of FT1D.

Identification of novel hepatitis B virus therapeutic vaccine candidates derived from polymerase protein

Hepatitis B virus (HBV) infection is a worldwide health problem with high morbidity and mortality rates. The therapeutic vaccine is a promising method of treatment, and HBV polymerase plays a vital role in viral replication. Therefore, a therapeutic vaccine that binds to HBV DNA polymerase may control HBV infection. We predicted and selected epitopes of polymerase using online databases and analysis software. We then performed molecular docking and peptide binding assays to evaluate the binding energies and affinities between polymerase epitopes and the HLA-A0201 molecule. Finally, we induced T cells from the peripheral blood mononuclear cells (PBMCs) of healthy donors using each epitope and quantified the functions of epitope-specific T cells by IFN-γELISPOT assay, T2 cell cytotoxicity assay, HepG2.2.15 cell cytotoxicity assay and HBV gene expression assays. Four epitopes (RVTGGVFLV, GLLGFAAPF, LLDDEAGPL and YMDDVVLGA) had low binding energy and two epitopes (RVTGGVFLV and GLLGFAAPF) had a high binding affinity. The T cells stimulated by two epitopes (GLLGFAAPF and HLYSHPIIL) had a greater ability to induce immune response and suppress HBV. The HBV DNA polymerase epitopes identified in this study are promising targets for designing an epitope-based therapeutic vaccine against HBV.

Identification of novel HLA-A0201-restricted T-cell epitopes against thyroid antigens in autoimmune thyroid diseases

PURPOSE

The different mechanisms that trigger the autoimmune attack to the thyroid between Hashimoto's thyroiditis (HT) and Graves' disease (GD) are still unclear. The aim of this study was to recognize thyroid antigens specific CD8+ T-cell epitopes and explore the relationship between these epitopes and thyroid autoantibodies, duration and classification in these two diseases.

METHODS

Free thiiodothyronine, free tetraiodothyronine, thyroid-stimulating hormone, TgAb, and TPOAb were all measured by immunochemiluminometric assays, while TRAb was tested by radioimmunoassay. HLA class I peptide affinity algorithms were applied to predict candidate thyroid autoantigen peptides that blind to HLA-A*0201. The ELISpot assay was used to detect Tg-, TPO-, and TSHR-specific CD8+ T cells.

RESULTS

We demonstrated that TG-6 was a novel HLA-A*0201-restricted CTL epitope in GD. TG-6, TG-7, TG-10, TG-11, and TPO-6 were immunodominant in GD patients compared with HT patients (TG-6: 38.5 vs. 8%, P = 0.034; TG-7, TG-10, TG-11, and TPO-6: 23.1 vs. 0%, P = 0.034). The immunodominance of TG-6 in GD patients was more evident than healthy controls (HC) (TG-6: 35.8 vs. 0%, P = 0.011), but there was no statistically significant difference between HT patients and HC. Subgroup analyses revealed the T-cell responsiveness to TG-6 was stronger in TgAb-negative HT patients (0 vs. 40%, P = 0.033). However, there was no correlation showed for TPOAb, TRAb, medication and duration in both HT and GD patients.

CONCLUSIONS

We report for the first time that both diseases, HT and GD, recognize different antigen-specific CD8-positive T cells. Tg maybe the dominant thyroid autoantigen contributing to breaking tolerance in GD. It could improve our knowledge of autoimmune thyroid diseases pathogenesis as well as offer new therapeutical tools in terms of peptide vaccine therapy.

Novel HLA-A2 restricted antigenic peptide derivatives with high affinity for the treatment of breast cancer expressing NY-ESO-1

Tumor immunotherapy based on specific tumor antigen has become the focus for breast cancer, and research into cancer/testes antigens (CTA) is progressing. As an important member in the CTA, NY-ESO-1 plays a crucial role in the treatment and prognosis of breast cancer. In this study, we aimed to improve the binding ability to MHC by designing and synthesizing stable NY-ESO-1-derived peptides, based on NetMHC 4.0 webserver (http://www.cbs.dtu.dk/services/NetMHC/) and HLP webserver (http://crdd.osdd.net/raghava/hlp/pep_both.htm). Moreover, after modification of the lead compound, affinity of the peptides to human leukocyte antigen-A2 (HLA-A2) was determined by a flow cytometry and an inverted fluorescence microscope in T2 cells that show high expression of HLA-A2. The results demonstrated that the affinity of peptides II-4 and II-10 to HLA-A2 was significantly better when compared to others (II-Lead, II-1 ~ II-3, II-5 ~ II-9, II-11 ~ II-15). Further studies indicated that II-4 and II-10, especially II-4, significantly promoted the maturation of HLA-A2-positive human peripheral blood-derived dendritic cells (DCs) from morphology and surface markers, the activation of CD8 + T lymphocytes, and the type-specific killing effect on HLA-A2⁺/NY-ESO-1⁺ MDA-MB-231 cells. Molecular docking studies suggested a strong interaction between peptide II-4 and HLA-A2, thereby indicating that the II-4 is a promising candidate with antigenic potential in the field of immunotherapy that needs more studies.

Anti-CD20 therapy depletes activated myelin-specific CD8+ T cells in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. CD8⁺ T cells have been strongly implicated in MS pathogenesis, but it is unclear whether myelin is a CD8⁺ T cell autoantigenic target in MS. This study demonstrated that while myelin-specific CD8⁺ T cells are present at similar frequencies in untreated MS patients and healthy subjects, the proportion of memory and CD20-expressing myelin-specific CD8⁺ T cells was increased in MS patients, suggesting prior antigen encounter. This activated phenotype was reversible as the memory and CD20-expressing populations of certain myelin-specific CD8⁺ T cells were reduced following anti-CD20 treatment.

CD8⁺ T cells are believed to play an important role in multiple sclerosis (MS), yet their role in MS pathogenesis remains poorly defined. Although myelin proteins are considered potential autoantigenic targets, prior studies of myelin-reactive CD8⁺ T cells in MS have relied on in vitro stimulation, thereby limiting accurate measurement of their ex vivo precursor frequencies and phenotypes. Peptide:MHC I tetramers were used to identify and validate 5 myelin CD8⁺ T cell epitopes, including 2 newly described determinants in humans. The validated tetramers were used to measure the ex vivo precursor frequencies and phenotypes of myelin-specific CD8⁺ T cells in the peripheral blood of untreated MS patients and HLA allele-matched healthy controls. In parallel, CD8⁺ T cell responses against immunodominant influenza epitopes were also measured. There were no differences in ex vivo frequencies of tetramer-positive myelin-specific CD8⁺ T cells between MS patients and control subjects. An increased proportion of myelin-specific CD8⁺ T cells in MS patients exhibited a memory phenotype and expressed CD20 compared to control subjects, while there were no phenotypic differences observed among influenza-specific CD8⁺ T cells. Longitudinal assessments were also measured in a subset of MS patients subsequently treated with anti-CD20 monoclonal antibody therapy. The proportion of memory and CD20⁺ CD8⁺ T cells specific for certain myelin but not influenza epitopes was significantly reduced following anti-CD20 treatment. This study, representing a characterization of unmanipulated myelin-reactive CD8⁺ T cells in MS, indicates these cells may be attractive targets in MS therapy.

What has zinc transporter 8 autoimmunity taught us about type 1 diabetes?

Zinc transporter 8 (ZnT8), a protein highly specific to pancreatic insulin-producing beta cells, is vital for the biosynthesis and secretion of insulin. ZnT8 autoantibodies (ZnT8A) are among the most recently discovered and least-characterised islet autoantibodies. In combination with autoantibodies to several other islet antigens, including insulin, ZnT8A help predict risk of future type 1 diabetes. Often, ZnT8A appear later in the pathogenic process leading to type 1 diabetes, suggesting that the antigen is recognised as part of the spreading, rather than the initial, autoimmune response. The development of autoantibodies to different forms of ZnT8 depends on the genotype of an individual for a polymorphic ZnT8 residue. This genetic variant is associated with susceptibility to type 2 but not type 1 diabetes. Levels of ZnT8A often fall rapidly after diagnosis while other islet autoantibodies can persist for many years. In this review, we consider the contribution made by ZnT8 to our understanding of type 1 diabetes over the past decade and what remains to be investigated in future research.

Standardizing T-Cell Biomarkers in Type 1 Diabetes: Challenges and Recent Advances

Type 1 diabetes (T1D) results from the progressive destruction of pancreatic β-cells in a process mediated primarily by T lymphocytes. The T1D research community has made dramatic progress in understanding the genetic basis of the disease as well as in the development of standardized autoantibody assays that inform both disease risk and progression. Despite these advances, there remains a paucity of robust and accepted biomarkers that can effectively inform on the activity of T cells during the natural history of the disease or in response to treatment. In this article, we discuss biomarker development and validation efforts for evaluation of T-cell responses in patients with and at risk for T1D as well as emerging technologies. It is expected that with systematic planning and execution of a well-conceived biomarker development pipeline, T-cell-related biomarkers would rapidly accelerate disease progression monitoring efforts and the evaluation of intervention therapies in T1D.

The Role of Zinc and Zinc Homeostasis in Macrophage Function

Zinc has long been recognized as an essential trace element, playing roles in the growth and development of all living organisms. In recent decades, zinc homeostasis was also found to be important for the innate immune system, especially for maintaining the function of macrophages. It is now generally accepted that dysregulated zinc homeostasis in macrophages causes impaired phagocytosis and an abnormal inflammatory response. However, many questions remain with respect to the mechanisms that underlie these processes, particularly at the cellular and molecular levels. Here, we review our current understanding of the roles that zinc and zinc transporters play in regulating macrophage function.

Analysis of epitope-based vaccine candidates against the E antigen of the hepatitis B virus based on the B genotype sequence: An in silico and in vitro approach

Chronic hepatitis B virus infection is a worldwide health problem with no current effective strategy to achieve a cure. The Hepatitis B virus (HBV) E antigen (HBeAg) has a negative effect on the immune system and a therapeutic vaccine is a promising strategy in order to treat chronic virus infection. In this study, we analyzed and identified the MHC-I, MHC-II and B cell epitopes of the HBeAg based on a B genotype sequence of HBV using a bioinformatic approach and in vitro experiments. The computational approach provided us with four epitopes (LLWFHISCL, YLVSFGVWI, MQLFHLCLI, TVLEYLVSF) of the specific MHC-I allele HLA-A0201 that conformed to all criteria. Molecular docking and a peptide binding assay showed that epitope TVLEYLVSF had the lowest binding energy and epitope LLWFHISCL had the highest binding affinity to the HLA-A0201 molecule. An interferonγenzyme-linked immunospot assay and cytotoxicity assay revealed that epitope LLWFHISCL had the highest ability to induce and stimulate T cells. Furthermore, we determined four core peptides of MHC-II epitopes and a region of the B cell epitope. The epitopes and region identified in this research may be helpful in designing epitope-based vaccines and boosting the mechanism research of HBeAg and its effect on the immune system.

Multipeptide-coupled nanoparticles induce tolerance in 'humanised' HLA-transgenic mice and inhibit diabetogenic CD8+ T cell responses in type 1 diabetes

AIMS/HYPOTHESIS

Induction of antigen-specific immunological tolerance may provide an attractive immunotherapy in the NOD mouse model but the conditions that lead to the successful translation to human type 1 diabetes are limited. In this study, we covalently linked 500 nm carboxylated polystyrene beads (PSB) with a mixture of immunodominant HLA-A*02:01-restricted epitopes (peptides-PSB) that may have high clinical relevance in humans as they promote immune tolerance; we then investigated the effect of the nanoparticle-peptide complexes on T cell tolerance.

METHODS

PSB-coupled mixtures of HLA-A*02:01-restricted epitopes were administered to HHD II mice via intravenous injection. The effects on delaying the course of the disease were verified in NOD.β2m ^null HHD mice. The diabetogenic HLA-A*02:01-restricted cytotoxic lymphocyte (CTL) responses to treatment with peptides-PSB were validated in individuals with type 1 diabetes.

RESULTS

We showed that peptides-PSB could induce antigen-specific tolerance in HHD II mice. The protective immunological mechanisms were mediated through the function of CD4⁺CD25⁺ regulatory T cells, suppressive T cell activation and T cell anergy. Furthermore, the peptides-PSB induced an activation and accumulation of regulatory T cells and CD11c⁺ dendritic cells through a rapid production of CD169⁺ macrophage-derived C-C motif chemokine 22 (CCL22). Peptides-PSB also prevented diabetes in 'humanised' NOD.β2m ^null HHD mice and suppressed pathogenic CTL responses in people with type 1 diabetes.

CONCLUSIONS/INTERPRETATION

Our findings demonstrate for the first time the potential for using multipeptide-PSB complexes to induce T cell tolerance and halt the autoimmune process. These findings represent a promising platform for an antigen-specific tolerance strategy in type 1 diabetes and highlight a mechanism through which metallophilic macrophages mediate the early cell-cell interactions required for peptides-PSB-induced immune tolerance.

In Silico Analysis of Epitope-Based Vaccine Candidates against Hepatitis B Virus Polymerase Protein

Hepatitis B virus (HBV) infection has persisted as a major public health problem due to the lack of an effective treatment for those chronically infected. Therapeutic vaccination holds promise, and targeting HBV polymerase is pivotal for viral eradication. In this research, a computational approach was employed to predict suitable HBV polymerase targeting multi-peptides for vaccine candidate selection. We then performed in-depth computational analysis to evaluate the predicted epitopes’ immunogenicity, conservation, population coverage, and toxicity. Lastly, molecular docking and MHC-peptide complex stabilization assay were utilized to determine the binding energy and affinity of epitopes to the HLA-A0201 molecule. Criteria-based analysis provided four predicted epitopes, RVTGGVFLV, VSIPWTHKV, YMDDVVLGA and HLYSHPIIL. Assay results indicated the lowest binding energy and high affinity to the HLA-A0201 molecule for epitopes VSIPWTHKV and YMDDVVLGA and epitopes RVTGGVFLV and VSIPWTHKV, respectively. Regions 307 to 320 and 377 to 387 were considered to have the highest probability to be involved in B cell epitopes. The T cell and B cell epitopes identified in this study are promising targets for an epitope-focused, peptide-based HBV vaccine, and provide insight into HBV-induced immune response.

Anti-Zinc Transporter Protein 8 Antibody Testing Is Not Informative in Routine Prediabetes Screening in Young Patients with Autoimmune Thyroiditis and Celiac Disease

BACKGROUND/AIMS

Patients with type 1 diabetes mellitus (T1DM), autoimmune thyroiditis (ATD), and celiac disease (CD) are at increased risk for developing other autoimmune diseases. We evaluated zinc transporter 8 (ZnT8) prevalence in patients with ATD and/or CD in order to define the usefulness of ZnT8 autoantibodies for prediabetes screening.

METHODS

Eighty-one young patients with ATD and/or CD were included in the study; 32 subjects with clinical onset of T1DM were enrolled as a control group. GAD65, IA-2, and ZnT8 antibodies were measured. An intravenous glucose tolerance test, C-peptide, glycosylated hemoglobin levels, and genomic analysis of HLA-DQA1* and -DQB1* were also considered in patients positive for autoantibodies.

RESULTS

The ZnT8 prevalence was higher in T1DM patients than in patients with other autoimmune diseases (p < 0.001); positive ZnT8 detection was found in 2 ATD (p = 0.004) and 3 ATD + CD (p = 0.04) patients. Positive ZnT8 was associated with GAD65 (p = 0.01) but not with IA-2 positivity. No correlation between ZnT8 detection and the number of T1DM-susceptible HLA-DQ heterodimers was found. Pathological C-peptide levels and insulin response were found in subjects with islet autoimmunity and genetic susceptibility.

CONCLUSION

ZnT8 autoantibodies detection in ATD and/or CD patients is low, and routine ZnT8 screening is not justified. ZnT8 evaluation may be recommended in subjects with autoimmune diseases as a marker for predicting compromised insulin secretion.

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.

T Cell-Mediated Beta Cell Destruction: Autoimmunity and Alloimmunity in the Context of Type 1 Diabetes

Type 1 diabetes (T1D) results from destruction of pancreatic beta cells by T cells of the immune system. Despite improvements in insulin analogs and continuous blood glucose level monitoring, there is no cure for T1D, and some individuals develop life-threatening complications. Pancreas and islet transplantation have been attractive therapeutic approaches; however, transplants containing insulin-producing cells are vulnerable to both recurrent autoimmunity and conventional allograft rejection. Current immune suppression treatments subdue the immune system, but not without complications. Ideally a successful approach would target only the destructive immune cells and leave the remaining immune system intact to fight foreign pathogens. This review discusses the autoimmune diabetes disease process, diabetic complications that warrant a transplant, and alloimmunity. First, we describe the current understanding of autoimmune destruction of beta cells including the roles of CD4 and CD8 T cells and several possibilities for antigen-specific tolerance induction. Second, we outline diabetic complications necessitating beta cell replacement. Third, we discuss transplant recognition, potential sources for beta cell replacement, and tolerance-promoting therapies under development. We hypothesize that a better understanding of autoreactive T cell targets during disease pathogenesis and alloimmunity following transplant destruction could enhance attempts to re-establish tolerance to beta cells.

Screening and identification of human ZnT8-specific single-chain variable fragment (scFv) from type 1 diabetes phage display library

Zinc transporter 8 (ZnT8) is a major autoantigen and a predictive marker in type 1 diabetes (T1D). To investigate ZnT8-specific antibodies, a phage display library from T1D was constructed and single-chain antibodies against ZnT8 were screened and identified. Human T1D single-chain variable fragment (scFv) phage display library consists of approximately 1×10(8) clones. After four rounds of bio-panning, seven unique clones were positive by phage ELISA. Among them, C27 and C22, which demonstrated the highest affinity to ZnT8, were expressed in Escherichia coli Top10F' and then purified by affinity chromatography. C27 and C22 specifically bound ZnT8 N/C fusion protein and ZnT8 C terminal dimer with one Arg325Trp mutation. The specificity to human islet cells of these scFvs were further confirmed by immunohistochemistry. In conclusion, we have successfully constructed a T1D phage display antibody library and identified two ZnT8-specific scFv clones, C27 and C22. These ZnT8-specific scFvs are potential agents in immunodiagnostic and immunotherapy of T1D.