Zinc transporter (ZnT)8186–194 is an immunodominant CD8+ T cell epitope in HLA-A2+ type 1 diabetic patients

Abstract

Aims/hypothesis Anti-zinc transporter (ZnT)8 autoantibodies are commonly detected in type 1 diabetic patients. We hypothesized that ZnT8 is also recognized by CD8+ T cells and aimed at identifying HLA-A2 (A*02:01)-restricted epitope targets. Methods Candidate epitopes were selected by ZnT8 plasmid DNA immunization of HLA-A2/DQ8-transgenic mice and tested for T-cell recognition in peripheral blood mononuclear cells of type 1 diabetic, type 2 diabetic and healthy subjects by IFN-γ enzyme-linked immunospot. Results Caucasian HLA-A2+ type 1 diabetic patients, both adults (83%) and children (60%),displayed ZnT8-reactive CD8+ T cells which recognized a single ZnT8186–194 (VAANIVLTV) epitope. This ZnT8186–194-reactive fraction accounted for 50–53% of total ZnT8-specific CD8+ T cells. Another ZnT8153–161 (VVTGVLVYL) sequence was recognized in 20–25% of type 1 diabetic adults and children, respectively. Both epitopes were type 1 diabetes-specific, being marginally recognized by type 2 diabetic and healthy subjects (7–12% for ZnT8186–194 and 0% for ZnT8153–161). Conclusions/interpretation ZnT8-reactive CD8+ T cells are predominantly directed against the ZnT8186–194 epitope and are detected in a majority of type 1 diabetic patients. The exceptional immunodominance of ZnT8186–194 may point to common environmental triggers precipitating beta-cell autoimmunity.

Islet-reactive CD8 + T cell frequencies in the pancreas, but not in blood, distinguish type 1 diabetic patients from healthy donors

“…Parallel ELISpot assays confirmed that ZnT8 186–194 -reactive IFN-γ responses were more frequent in T1D vs. healthy donors (Fig. S8) (7). In contrast, similar frequencies of ZnT8 186–194 and MelanA 26–35 MMr + CD8 + T cells were detected in age-stratified T1D and healthy donors (Fig.…”

“…Given that ZnT8 186–194 -reactive IFN-γ responses are highly prevalent in T1D patients (7), we started by generating ZnT8 186–194 -reactive CD8 + T-cell clones from a new-onset T1D patient (D222D) (7). Following in-vitro expansion with the ZnT8 186–194 peptide (8), HLA-A2 MMr + cells were labeled with two different fluorochromes (9) and sorted (Fig.…”

Autoreactive T cells in type 1 diabetes

“…Low levels of insulin secretion are detected in many patients even decades after diagnosis: some β cell regeneration occurs after diagnosis, and it has been hypothesized that regeneration may occur during the preclinical stage. efflux transporter ZNT8 (7,(81)(82)(83)(84)(85), chromogranin (86,87), islet-amyloid polypeptide (IAPP) (8), and more. Many are present in secretory granules, and some are unique to β cells (insulin, IGRP, ZNT8), while some are expressed in other cells and tissues, including neuroendocrine cells (GAD65, IA-2) (88,89).…”

β-Cell–Specific CD8 T Cell Phenotype in Type 1 Diabetes Reflects Chronic Autoantigen Exposure

“…Several lines of evidence implicate the CD8 T cell lineage in this process: 1) CD8 T cells predominate in islet-centered leukocytic infiltrates close to diagnosis (3,4); 2) autoreactive CD8 T cells with b-cell epitope specificities have been detected in such early infiltrates (3); 3) CD8 T cell clones specific for preproinsulin-derived peptides can kill b-cells in vitro (5,6); and 4) large genetic association studies link disease susceptibility to the inheritance of specific human leukocyte antigen class I (HLAI) alleles (7). This mounting functional and epidemiological evidence, combined with the expanding array of reported HLAI-restricted b-cell epitopes (8,9), provides a strong rationale for detailed studies of autoreactive CD8 T cells in type 1 diabetes.…”