Coeliac disease (CeD) is an intestinal autoimmune disorder, triggered by an aberrant immune reaction to gluten peptides in genetically predisposed HLA-DQ2/DQ8+ individuals. In active CeD, tissue damage is partly driven by cytotoxic intra-epithelial CD8+ T cells. The innate-like role of these CD8+ T cells is well characterised, where the IL-15 upregulated CD94/NKG2C heterodimer engages with non-classical HLA-E, which is upregulated on stressed intestinal epithelial cells in active CeD. However, the adaptive TCR-dependent role of CD8+ T cells in CeD remains elusive.
In this study, we sought to identify and validate coeliac-related antigens that could potentially bind non-classical HLA-E.
From an in silico peptide screen, we shortlisted candidate HLA-restricted gluten-derived peptides based on canonical motifs. We validated that six of these native gliadin candidates and one partially deamidated version could bind the HLA-E protein using both differential-scanning fluorimetry and HLA-E-K562 cellular-based assays. We subsequently performed flow cytometric proliferation assays using PBMCs derived from active and treated (on a gluten-free diet) patients with CeD (n=24) incubated with candidate peptides for 7 days, and identified donors who had convincing gluten-peptide reactive CD8+ T cells. Following expansion of these polyclonal CD8+ T cells in culture, we found that tetramers of HLA-E presenting a gluten-derived peptide could specifically bind CD8+ T cells.
Taken together, these results reveal the potential for gluten-derived peptides to bind HLA-E and for recognition by the TCR of CD8+ T cells in patients with CeD. The functional impact of such triggering is under further study.