Abstract
AimsRecent studies highlight the potentially important role of neoepitopes in breaking immune tolerance in type 1 diabetes. T cell reactivity to these neoepitopes has been reported, but how this response compares quantitatively and phenotypically with previous reports on native epitopes is not known. Thus, an understanding of the relationship between native and neoepitopes and their role as tolerance breakers or disease drivers in type 1 diabetes is required. We set out to compare T cell reactivity and phenotype against a panel of neo- and native islet autoantigenic epitopes to examine how this relates to stages of type 1 diabetes development.MethodsFifty-four subjects comprising patients with T1D, and autoantibody-positive unaffected family members were tested against a panel of neo- and native epitopes by ELISPOT (IFN-γ, IL-10, and IL-17). A further subset of two patients was analyzed by Single Cell Immune Profiling (RNAseq and TCR α/β) after stimulation with pools of native and neoepitope peptides.ResultsT cell responses to native and neoepitopes were present in patients with type 1 diabetes and at-risk subjects, and overall, there were no significant differences in the frequency, magnitude, or phenotype between the two sets of peptide stimuli. Single cell RNAseq on responder T cells revealed a similar profile in T1D patients stimulated with either neo- or native epitopes. A pro-inflammatory gene expression profile (TNF-α, IFN-γ) was dominant in both native and neoepitope stimulated T cells. TCRs with identical clonotypes were found in T cell responding to both native and neoepitopes.Conclusion/InterpretationThese data suggest that in peripheral blood, T cell responses to both native and neoepitopes are similar in terms of frequency and phenotype in patients with type 1 diabetes and high-risk unaffected family members. Furthermore, using a combination of transcriptomic and clonotypic analyses, albeit using a limited panel of peptides, we show that neoepitopes are comparable to native epitopes currently in use for immune-monitoring studies.
Highlights
Type 1 diabetes arises as a result of immune-mediated loss of b cell mass and function
We selected native peptides of proinsulin (PIPs), representing naturally processed and presented epitopes known to elicit CD4 responses in PBMC from individuals with type 1 diabetes [2,3,4] and hybrid insulin peptides (HIPs), known to activate CD4 T cells isolated from pancreatic islets from deceased organ donors with type 1 diabetes [8, 9]
In agreement with observations made by others we can detect T cell responsive to HIPs in PBMCs and that these cells respond with a range of cytokine production
Summary
Type 1 diabetes arises as a result of immune-mediated loss of b cell mass and function. A lack of self-tolerance against islet autoantigens facilitates this destruction; one of the hallmarks of type 1 diabetes pathogenesis is the autoantigen-specific clonal expansion of T cells [1]. Recent studies have highlighted the role of the b cell in orchestrating its own sustained attrition and demise by enabling a repertoire of non-germline encoded “neoepitopes” previously not encountered by the immune system [5]. Neoepitopes in T1D can be generated through several mechanisms including post-translational modification of peptides, for example via enzymatic deamidation or citrullination which can augment binding to HLA molecules and boost T cell responses [6]; alternative RNA-splicing results in proteins being encoded from an alternative open reading frame [7] and peptide fusion of islet-derived peptides [8]. Peptide fusion is a post-translational modification in which peptide fragments of proteins such as proinsulin are modified through fusion with peptides from other secretory granule proteins resulting in novel peptidic species termed hybrid insulin peptides (HIPs)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
