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TCR/HLA Humanized Mice Reveal Reduced Tolerance and Increased Immunogenicity of Post-translationally Modified GAD65 Epitope

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posted on 2022-02-18, 16:59 authored by Yi Jing, Yuelin Kong, John McGinty, Gabriele Blahnik-Fagan, Thomas Lee, Stephanie Orozco-Figueroa, Matthew L. Bettini, Eddie A. James, Maria Bettini

Accumulating evidence supports a critical role for post-translationally modified (PTM) islet neoantigens in type 1 diabetes. However, our understanding regarding thymic development and peripheral activation of PTM autoantigen reactive T cells is still limited. Using HLA-DR4 humanized mice, we observed that deamidation of GAD65_115-127generates a more immunogenic epitope that recruits T cells with promiscuous recognition of both the deamidated and native epitopes, and reduced frequency of regulatory T cells. Using humanized HLA/TCR mice we observed that TCRs reactive to the native or deamidated GAD65_115-127led to efficient development of CD4+ effector T cells; however, regulatory T cell development was reduced in mice expressing the PTM reactive TCR, which was partially restored with exogenous PTM peptide. Upon priming, both the native specific and the deamidated specific T cells accumulated in pancreatic islets, suggesting that both specificities can recognize endogenous GAD65 and contribute to anti-beta-cell responses. Collectively, our observations in polyclonal and single TCR systems suggest that while effector T cell responses can exhibit cross-reactivity between native and deamidated GAD65 epitopes, regulatory T cell development is reduced in response to the deamidated epitope, pointing to Treg development as a key mechanism for loss of tolerance to PTM antigenic targets.

Funding

This work was supported by the NIH (AI125301 to M.Be. and DK114456 to M.L.B.), and The Robert and Janice McNair Foundation.

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Post-Translational Modifications Glutamic Acid Decarboxylase (GAD)Type 1 Diabetes Regulatory T Cells T Lymphocyte(s)Biological Sciences not elsewhere classified

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CC BY-NC-SA 4.0

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