AUTHOR=Hellesen Alexander , Aslaksen Sigrid , Breivik Lars , Røyrvik Ellen Christine , Bruserud Øyvind , Edvardsen Kine , Brokstad Karl Albert , Wolff Anette Susanne Bøe , Husebye Eystein Sverre , Bratland Eirik 

TITLE=21-Hydroxylase-Specific CD8+ T Cells in Autoimmune Addison’s Disease Are Restricted by HLA-A2 and HLA-C7 Molecules

JOURNAL=Frontiers in Immunology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.742848

DOI=10.3389/fimmu.2021.742848

ISSN=1664-3224

ABSTRACT=<sec><title>Objectives</title><p>CD8+ T cells targeting 21-hydroxylase (21OH) are presumed to play a central role in the destruction of adrenocortical cells in autoimmune Addison’s disease (AAD). Earlier reports have suggested two immunodominant CD8+ T cell epitopes within 21OH: LLNATIAEV (21OH<sub>342-350</sub>), restricted by HLA-A2, and EPLARLEL (21OH<sub>431-438</sub>), restricted by HLA-B8. We aimed to characterize polyclonal CD8+ T cell responses to the proposed epitopes in a larger patient cohort with AAD.</p></sec><sec><title>Methods</title><p>Recombinant fluorescent HLA-peptide multimer reagents were used to quantify antigen-specific CD8+ T cells by flow cytometry. Interferon-gamma (IFNγ) Elispot and biochemical assays were used to functionally investigate the 21OH-specific T cells, and to map the exactly defined epitopes of 21OH.</p></sec><sec><title>Results</title><p>We found a significantly higher frequency of HLA-A2 restricted LLNATIAEV-specific cells in patients with AAD than in controls. These cells could also be expanded <italic>in vitro</italic> in an antigen specific manner and displayed a robust antigen-specific IFNγ production. In contrast, only negligible frequencies of EPLARLEL-specific T cells were detected in both patients and controls with limited IFNγ response. However, significant IFNγ production was observed in response to a longer peptide encompassing EPLARLEL, 21OH<sub>430-447</sub>, suggesting alternative dominant epitopes. Accordingly, we discovered that the slightly offset ARLELFVVL (21OH<sub>434-442</sub>) peptide is a novel dominant epitope restricted by HLA-C7 and not by HLA-B8 as initially postulated.</p></sec><sec><title>Conclusion</title><p>We have identified two dominant 21OH epitopes targeted by CD8+ T cells in AAD, restricted by HLA-A2 and HLA-C7, respectively. To our knowledge, this is the first HLA-C7 restricted epitope described for an autoimmune disease.</p></sec>