# Diabetogenic CD4 T Cell Recognition of Hybrid Peptide Ligands

> **NIH NIH R56** · UNIVERSITY OF COLORADO DENVER · 2020 · $512,702

## Abstract

PROJECT SUMMARY/ABSTRACT
The overall goal of this proposal is to understand how diabetogenic T cell receptors (TCRs) recognize the
MHCII and hybrid peptide complexes. Peptide ligands of CD4 and CD8 T cells are conventionally derived from
contiguous fragments of the parental proteins by the endocytic pathway and proteasome. We first suggested
insulin (Ins) B:9-23 and WE14, a natural cleavage product of chromogranin A (ChgA), peptides may be spliced
with other beta cell granule proteins and form neo-antigens. We also demonstrated that fusion peptides are the
true ligands for many diabetogenic T cells. Both C-terminal modification of the Ins B:9-23 peptide and N-
terminal additions to the WE14 peptide of ChgA can create superagonists for T cells. We proposed peptide
fusion by transpeptidation as a means of creating the required modifications to the peptides and explain how
the T cells driving autoimmunity escape negative selection in the thymus but find their antigen in the target
tissue. Our structural and biophysical data showed that the EALYLV portion of Ins B:9-23 and WXRM(D/E)
portion of WE14 may be common acceptors of these hybrid peptides. We determined the structures of two
different types of mouse TCRs and a human TCR, bound to their optimal versions of the MHCII-Ins peptide
ligands. All the Ins reactive TCRs engage the N-terminal portion (EALYL) of Ins B:9-23, indicating similarities in
how these ligands are formed in both human and mouse. The structures showed that the specificity differences
among mouse Type A and Type B T cells lies in how they interact with the amino acid at p8 (B:21) of the Ins
peptide. The structures also show how the peptide modifications were essential to the formation of the
complexes, bolstering a role for modification of the peptide in vivo to initiate the CD4 T cell response in T1D.
We hypothesize that EALYLV and WXRM(D/E) are the acceptors of the fusion peptides and form the common
diabetogenic TCR docking spots, in addition to being novel targets for T1D immunotherapy. Previously, we
have shown aromatic amino acids play important role in TCR cross-reactivity. The aromatic amino acids (Y
and W) may be the common epitopes for diabetogenic TCRs and critical to shape the broadness of hybrid
peptide reactive T cell repertories. Whereas, the donor peptides of hybrid peptides contribute to diversity the T
cell repertoire to both Ins and ChgA autoantigens. We will study the following specific aims: Determine how
diabetogenic CD4 TCRs recognize IAg7 and ChgA WE14 hybrid peptides; Define the nature of the human Ins
B:9-23 hybrid peptides presented to the diabetogenic CD4 TCRs; Test monoclonal antibodies (mAbs) specific
for the acceptor portions of the hybrid peptides bound to MHC in the development of T1D. These data may
guide therapeutic strategies towards specific modulation of TCR activation, which could be the basis for a
novel therapeutic approach in treatment of T1D.
Research Strategy Page 2

## Key facts

- **NIH application ID:** 10247154
- **Project number:** 1R56AI153488-01
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** SHAODONG DAI
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $512,702
- **Award type:** 1
- **Project period:** 2020-09-09 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10247154

## Citation

> US National Institutes of Health, RePORTER application 10247154, Diabetogenic CD4 T Cell Recognition of Hybrid Peptide Ligands (1R56AI153488-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10247154. Licensed CC0.

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