B cell epitopes of gliadin

Abstract

A phage displayed dodecapeptide library and synthetic octapeptides spanning the complete sequence of α‐ and γ‐type gliadin and overlapping in six amino acids (pepscan) were screened for binding to human gliadin antibodies (AGA). Phage display experiments led to four sequences recognized with significantly higher frequency by sera with raised IgA‐AGA titres than by control sera. All these peptides contained the core sequence PEQ. Pepscan experiments revealed binding of AGA to five prominent regions: (i) QXQPFP (binding to IgG and IgA, X representing P, Q, and L); (ii) IPEQ (IgG) and WQIPEQ (IgA); (iii) FFQP (IgG) and QGXFQP (IgA, X representing F and S); (iv) PQQLPQ (IgG and IgA), all in α‐type gliadin; and (v) QPQQPF (IgG and IgA) in γ‐type gliadin. In two of the sequences (QPQQPF and QQQPFP), substitution of Q by E resulting in QPEQPF and QEQPFP, respectively, increased significantly binding of AGA from sera of patients with biopsy‐proven or suspected coeliac disease (CoD), all positive for endomysium antibodies (EmA). In contrast, binding of sera with high AGA titre from EmA‐negative patients (CoD and dermatitis herpetiformis excluded) was not enhanced by this substitution. Thus, AGA directed against these modified epitopes can be regarded as specific for CoD. This is the first study demonstrating that deamidation of gliadin improves reactivity of AGA of CoD patients.

Serologic Assay Based on Gliadin-Related Nonapeptides as a Highly Sensitive and Specific Diagnostic Aid in Celiac Disease

“…According to our previous findings (19 ), the sequences QQQPFP, WQIPEQ, and PQQLPQ may also be targets of human AGAs. The hexapeptide QQQPFP occurs twice in ␣-type gliadin as the sequences QWPQQQPFP and FQGQQQPFP.…”

“…This deamidation reaction improves binding of gliadin peptides to MHC class II molecules and is important for subsequent stimulation of gliadin-specific T cells (17,18 ). Furthermore, deamidation of gliadin increases binding of AGAs in the serum of CD patients, but not control individuals, to gliadin (19,20 ). The tripeptide PEQ was discovered to be the core epitope of gliadin antibodies by screening of phage-displayed peptide libraries for binding to IgA of celiac patients (19 ).…”

“…Furthermore, deamidation of gliadin increases binding of AGAs in the serum of CD patients, but not control individuals, to gliadin (19,20 ). The tripeptide PEQ was discovered to be the core epitope of gliadin antibodies by screening of phage-displayed peptide libraries for binding to IgA of celiac patients (19 ). Using synthetic peptide libraries, we investigated the role of amino acid residues flanking the PEQ motif and searched for additional gliadin sequences specifically detected by AGAs of CD patients.…”

Gliadin T Cell Epitope Selection by Tissue Transglutaminase in Celiac Disease

“…Competition and T Cell Recognition of Overlapping Peptides from ␥-Gliadin M36999 -The established competition assay and the validated CE analysis was used to measure competition of a set of 23 20-mer peptides overlapping by 10 residues and covering nearly the complete sequence of the ␥-gliadin M36999 (19,20). F-␣I was used as reporter peptide, and its deamidation by TG2 was quantified by MEKC.…”

Analysis of Food Allergen Structures and Development of Foods for Allergic Patients

“…29) As other allergens, thioredoxin, 19) lipid transfer protein, 20) acyl-CoA oxidase, 30) peroxidase, 31) and fructose-bisphosphate aldolase 32) were identified. 8,21) In addition, the epitope structures of gliadin in patients with FDEIA 24) and celiac disease 33) have been recently reported.…”