Gliadin-specific CD8+ T cell responses restricted by HLA class I A*0101 and B*0801 molecules in celiac disease patients

Initial studies associated the HLA class I A*01 and B*08 alleles with celiac disease (CD) susceptibility. Subsequent analyses showed a primary association with HLA class II alleles encoding for the HLA DQ2.5 molecule. Due to the strong linkage disequilibrium of A*01 and B*08 alleles with the DR3-DQ2.5 haplotype, and a recent genome-wide association study (GWAS) indicating that B*08 and B*39 are predisposing genes, the etiologic role of HLA class I in CD pathogenesis needs to be addressed. We screened gliadin proteins (2?-, 2?-, and 2?-gliadin) using bioinformatic algorithms for the presence of peptides predicted to bind A*0101 and B*0801 molecules. The top 1% scoring 9- and 10-mer peptides (n=97, total) were synthesized and tested in binding assays using purified A*0101 and B*0801 molecules. Twenty/97 peptides bound B*0801, but only three/97 bound A*0101, with high affinity (IC50 < 500 nM). These 23 gliadin peptides were next assayed by IFN-? EliSpot for recognition in peripheral blood cells of CD patients and healthy controls carrying the A*0101 and/or B*0801 genes and in A*0101/B*0801 negative CD patients. Ten of the 23 peptides assayed recalled IFN-? responses mediated by CD8+ T cells in A*0101/B*0801 positive celiacs. Two peptides were restricted by A*0101, and eight by B*0801. Of note, 50% (5/10) of CD8+ T cell epitopes mapped within the ?-gliadins. Our results highlight the value of predicted binding to HLA molecules for identifying gliadin epitopes, and demonstrate that HLA class I molecules restrict the anti-gluten T cell response in CD patients.