Follicular helper T cell profiles predict response to costimulation blockade in type 1 diabetes.

Follicular helper T (TFH) cells are implicated in type 1 diabetes (T1D), and their development has been linked to CD28 costimulation. We tested whether TFH cells were decreased by costimulation blockade using the CTLA-4-immunoglobulin (Ig) fusion protein (abatacept) in a mouse model of diabetes and in individuals with new-onset T1D. Unbiased bioinformatics analysis identified that inducible costimulatory molecule (ICOS)+ TFH cells and other ICOS+ populations, including peripheral helper T cells, were highly sensitive to costimulation blockade. We used pretreatment TFH profiles to derive a model that could predict clinical response to abatacept in individuals with T1D. Using two independent approaches, we demonstrated that higher frequencies of ICOS+ TFH cells at baseline were associated with a poor clinical response following abatacept administration. Therefore, TFH analysis may represent a new stratification tool, permitting the identification of individuals most likely to benefit from costimulation blockade.

Costimulation Blockade Disrupts CD4+ T Cell Memory Pathways and Uncouples Their Link to Decline in ß-Cell Function in Type 1 Diabetes.

We previously reported that costimulation blockade by abatacept limits the decline of ß-cell function and the frequency of circulating CD4+ central memory T cells (TCM) (CD45RO+CD62L+) in new-onset type 1 diabetes. In human subjects receiving placebo, we found a significant association between an increase in CD4+ TCM cells and the decline of ß-cell function. To extend and refine these findings, we examined changes in human CD4+ and CD8+ naive and memory T cell subsets at greater resolution using polychromatic flow and mass cytometry. In the placebo group, we successfully reproduced the original finding of a significant association between TCM and ß-cell function and extended this to other T cell subsets. Furthermore, we show that abatacept treatment significantly alters the frequencies of a majority of CD4+ conventional and regulatory T cell subsets; in general, Ag-naive subsets increase and Ag-experienced subsets decrease, whereas CD8+ T cell subsets are relatively resistant to drug effects, indicating a lesser reliance on CD28-mediated costimulation. Importantly, abatacept uncouples the relationship between changes in T cell subsets and ß-cell function that is a component of the natural history of the disease. Although these data suggest immunological markers for predicting change in ß-cell function in type 1 diabetes, the finding that abatacept blunts this relationship renders the biomarkers nonpredictive for this type of therapy. In sum, our findings point to a novel mechanism of action for this successful immunotherapy that may guide other disease-modifying approaches for type 1 diabetes.

T cell receptor ß-chains display abnormal shortening and repertoire sharing in type 1 diabetes.

Defects in T cell receptor (TCR) repertoire are proposed to predispose to autoimmunity. Here we show, by analyzing >2 × 108 TCRB sequences of circulating naive, central memory, regulatory and stem cell-like memory CD4+ T cell subsets from patients with type 1 diabetes and healthy donors, that patients have shorter TCRB complementarity-determining region 3s (CDR3), in all cell subsets, introduced by increased deletions/reduced insertions during VDJ rearrangement. High frequency of short CDR3s is also observed in unproductive TCRB sequences, which are not subjected to thymic culling, suggesting that the shorter CDR3s arise independently of positive/negative selection. Moreover, TCRB CDR3 clonotypes expressed by autoantigen-specific CD4+ T cells are shorter compared with anti-viral T cells, and with those from healthy donors. Thus, early events in thymic T cell development and repertoire generation are abnormal in type 1 diabetes, which suggest that short CDR3s increase the potential for self-recognition, conferring heightened risk of autoimmune disease.

Metabolic and immune effects of immunotherapy with proinsulin peptide in human new-onset type 1 diabetes.

Immunotherapy using short immunogenic peptides of disease-related autoantigens restores immune tolerance in preclinical disease models. We studied safety and mechanistic effects of injecting human leukocyte antigen-DR4(DRB1*0401)-restricted immunodominant proinsulin peptide intradermally every 2 or 4 weeks for 6 months in newly diagnosed type 1 diabetes patients. Treatment was well tolerated with no systemic or local hypersensitivity. Placebo subjects showed a significant decline in stimulated C-peptide (measuring insulin reserve) at 3, 6, 9, and 12 months versus baseline, whereas no significant change was seen in the 4-weekly peptide group at these time points or the 2-weekly group at 3, 6, and 9 months. The placebo group's daily insulin use increased by 50% over 12 months but remained unchanged in the intervention groups. C-peptide retention in treated subjects was associated with proinsulin-stimulated interleukin-10 production, increased FoxP3 expression by regulatory T cells, low baseline levels of activated ß cell-specific CD8 T cells, and favorable ß cell stress markers (proinsulin/C-peptide ratio). Thus, proinsulin peptide immunotherapy is safe, does not accelerate decline in ß cell function, and is associated with antigen-specific and nonspecific immune modulation.