Inflammation of intestinal tissue in patients affected by celiac disease (CD) originates from the adaptive and innate immune responses elicited by the undigested gliadin fragments through molecular mechanisms not yet completely described. Undigested A-gliadin peptide P31-43 is central to CD pathogenesis, entering enterocytes in vesicular compartments by endocytosis and inducing an innate immune response in CD intestinal mucosa. This study focused on the reasons why P31-43 does not behave as adaptive immunogenic agent. Once obtained by NMR analysis, the three-dimensional model of P31-43 was used to implement a series of in silico experiments aimed to explore the ability of the peptide to interact with HLA-DQ2 and the corresponding receptor onto T cells. Our results show that P31-43 is a poor ligand for DQ2 and/or T-cell receptor. This study was also aimed to investigate, from a structural point of view, the previous experimental findings by which P31-43 is able to enhance the phosphorylation level of the protein ERK2, while some P31-43 Ala-mutants decrease or totally inhibit that process. The molecular models of P31-43, P31-43 P36A, and F37A mutants were used for in silico docking experiments onto the ERK2 structure. The experiments support the hypothesis that P31-43 F37A works as an ERK2 phosphorylation inhibitor because it binds to the ERK2 phosphorylation site. This study reports on the structural properties of so far never NMR characterized gliadin peptides relevant in CD and explores details about their mechanisms of action.

Wheat, milk, peanuts, soy, egg and corn are among the most major sources of immunoreactive proteins. The first goal of this study was to examine the reactivity of food-specific antibodies with human tissue antigens. Affinity-purified rabbit anti-food antibodies were applied to sixty-five tissue antigens. Anti-peanut antibody had the most reactions with twenty-four out of the sixty-five antigens, followed by anti-alpha-gliadin with twenty, anti-egg with seventeen, anti-wheat with fifteen, anti-milk with fourteen, and both anti-corn and anti-soy with ten each tissue antigens. Serial dilutions and inhibition study confirmed that these reactions were specific. The second goal was to determine the percentage of blood donors with elevations in IgG, IgA, IgM and IgE antibodies against these food antigens. A significant percentage of the tested blood samples showed elevations in antibodies against different food antigens. This reaction of food-specific antibodies with different tissue antigens indicates that cross-reactivity between food and human tissue antigens exists, and these antibodies, if detected in blood, may contribute to different autoimmune diseases.