T cell receptor recognition of hybrid insulin peptides bound to HLA-DQ8

Mai T Tran,Yi Tian Ting,Nicole L La Gruta,Jamie Rossjohn,Fergus J Cameron,Anthony W Purcell,Pushpak Bhattacharjee,Eleonora Tresoldi,Claerwen M Jones,Hugh H Reid,Goodluck Onwukwe,Stuart I Mannering,Jia Jia Lim,Pouya Faridi

doi:10.1038/s41467-021-25404-x

Abstract

HLA-DQ8, a genetic risk factor in type I diabetes (T1D), presents hybrid insulin peptides (HIPs) to autoreactive CD4+ T cells. The abundance of spliced peptides binding to HLA-DQ8 and how they are subsequently recognised by the autoreactive T cell repertoire is unknown. Here we report, the HIP (GQVELGGGNAVEVLK), derived from splicing of insulin and islet amyloid polypeptides, generates a preferred peptide-binding motif for HLA-DQ8. HLA-DQ8-HIP tetramer+ T cells from the peripheral blood of a T1D patient are characterised by repeated TRBV5 usage, which matches the TCR bias of CD4+ T cells reactive to the HIP peptide isolated from the pancreatic islets of a patient with T1D. The crystal structure of three TRBV5+ TCR-HLA-DQ8-HIP complexes shows that the TRBV5-encoded TCR β-chain forms a common landing pad on the HLA-DQ8 molecule. The N- and C-termini of the HIP is recognised predominantly by the TCR α-chain and TCR β-chain, respectively, in all three TCR ternary complexes. Accordingly, TRBV5 + TCR recognition of HIP peptides might occur via a ‘polarised’ mechanism, whereby each chain within the αβTCR heterodimer recognises distinct origins of the spliced peptide presented by HLA-DQ8.

Highlights

HLA-DQ8, a genetic risk factor in type I diabetes (T1D), presents hybrid insulin peptides (HIPs) to autoreactive CD4+ T cells
While some of the pancreatic islet-infiltrating CD4+ T cells responded to the proinsulin C-peptide, the C-peptide-IAPP2 HIP presented by HLA-DQ8 (GQVELGGGNAVEVLK) may potentially be a more effective antigen due to the generation of a more favourable HLA-DQ8 binding motif
HLA-DQ8 molecules were affinity purified with antiHLA-DQ immunoaffinity chromatography from the 9033 Epstein-Barr virus (EBV) transformed B lymphoblastoid cell line and HLA-DQ8 bound peptides were pre-fractionated by HPLC prior to mass spectrometry analysis[21]

Summary

Introduction

HLA-DQ8, a genetic risk factor in type I diabetes (T1D), presents hybrid insulin peptides (HIPs) to autoreactive CD4+ T cells. It has been reported that murine CD4+ T cells and human islet-infiltrating CD4+ T cells recognise β-cell derived epitopes formed by the fusion of proinsulin C-peptide with other β-cell granule proteins[5,6,7,8,9,10]. This type of post-translational modification (PTM) dramatically changes the peptide sequence by joining two ‘self’ peptides together to form a ‘non-self’ hybrid peptide. While some of the pancreatic islet-infiltrating CD4+ T cells responded to the proinsulin C-peptide, the C-peptide-IAPP2 HIP presented by HLA-DQ8 (GQVELGGGNAVEVLK) may potentially be a more effective antigen due to the generation of a more favourable HLA-DQ8 binding motif.

Methods

Results

Conclusion