A unique CD8(+) T lymphocyte signature in pediatric type 1 diabetes.

Human type 1 diabetes results from a destructive auto-reactive immune response in which CD8(+) T lymphocytes play a critical role. Given the intense ongoing efforts to develop immune intervention to prevent and/or cure the disease, biomarkers suitable for prediction of disease risk and progress, as well as for monitoring of immunotherapy are required. We undertook separate multi-parameter analyses of single naïve and activated/memory CD8(+) T lymphocytes from pediatric and adult patients, with the objective of identifying cellular profiles associated with onset of type 1 diabetes. We observe global perturbations in gene and protein expression and in the abundance of T cell populations characterizing pediatric but not adult patients, relative to age-matched healthy individuals. Pediatric diabetes is associated with a unique population of CD8(+) T lymphocytes co-expressing effector (perforin, granzyme B) and regulatory (transforming growth factor ß, interleukin-10 receptor) molecules. This population persists after metabolic normalization and is especially abundant in children with high titers of auto-antibodies to glutamic acid decarboxylase and with elevated HbA1c values. These findings highlight striking differences between pediatric and adult type 1 diabetes, indicate prolonged large-scale perturbations in the CD8(+) T cell compartment in the former, and suggest that CD8(+)CD45RA(-) T cells co-expressing effector and regulatory factors are of interest as biomarkers in pediatric type 1 diabetes.

ZnT8 is a major CD8+ T cell-recognized autoantigen in pediatric type 1 diabetes.

Type 1 diabetes results from the destruction of ß-cells by an autoimmune T-cell response assisted by antigen-presenting B cells producing autoantibodies. CD8(+) T-cell responses against islet cell antigens, thought to play a central role in diabetes pathogenesis, can be monitored using enzyme-linked immunosorbent spot (ELISpot) assays. However, such assays have been applied to monitoring of adult patients only, leaving aside the large and increasing pediatric patient population. The objective of this study was twofold: 1) to develop a CD8(+) T-cell interferon-γ ELISpot assay for pediatric patients and 2) to determine whether zinc transporter 8 (ZnT8), a recently described target of autoantibodies in a majority of patients, is also recognized by autoreactive CD8(+) T cells. Using DNA immunization of humanized mice, we identified nine HLA-A2-restricted ZnT8 epitopes. Among 36 HLA-A2(+) children with diabetes, 29 responded to ZnT8 epitopes, whereas only 3 of 16 HLA-A2(+) control patients and 0 of 17 HLA-A2(-) control patients responded. Some single ZnT8 epitopes performed as well as the group of epitopes in discriminating between patients and control individuals. Thus, ZnT8 is a major CD8(+) T-cell autoantigen, and ELISpot assays display similar performance in adult and pediatric type 1 diabetes.