Background: Wheat gluten comprises gliadins and glutenins. The high-molecular-weight (HMW) glutenin subunits (GS)-1Dy10 are toxic for patients with celiac disease (CD). This study aimed to assess whether CD patients mount a serological response to HMW-GS-1Dy10. Methods: Recombinant HMW-GS-1Dy10 was deamidated using human recombinant tissue transglutaminase. MALDI-TOF was performed to compare the level of deamidation of glutamine residues between material before and after treatment. Enzyme-linked immunosorbent assays were developed. Sera from patients with untreated CD and gastrointestinal disease controls were tested and receiver operator characteristics were used to calculate cutoffs. Results: MALDI-TOF revealed a number of fragments matching known HMW-GS-1Dy10 sequences within both the deamidated and non-deamidated material. Evidence of deamidation of glutamine residues was found only within the human transglutaminase-treated material. Patients with untreated CD had significantly increased levels of serum antibodies to HMW-GS-1Dy10 compared to controls. Undeamidated HMW-GS-1Dy10 IgA antibodies had sensitivities and specificities of 72.5 and 78.26%, respectively. Deamidated HMW-GS-1Dy10 IgA antibodies had sensitivities and specificities of 76.8 and 65.2%. Undeamidated HMW-GS-1Dy10 IgG antibodies had sensitivities and specificities of 75.3 and 68.1%. Deamidated HMW-GS-1Dy10 IgG antibodies had sensitivities and specificities of 36.2 and 92.8%. Conclusion: Patients with untreated CD have raised antibody levels to HMW-GS-1Dy10, indicating the participation of these proteins in the adaptive immune response to gluten. Discrimination between CD patients and controls is not enhanced by deamidation of HMW-GS-1Dy10. Thus antibodies to these proteins are not useful markers for CD detection.

Coeliac disease is an inflammatory disease of the upper small intestine and results from gluten ingestion in genetically susceptible individuals, and is the only life-long nutrient-induced enteropathy. The only treatment is a strict gluten-free diet and the longer the individual fails to adhere to this diet, the greater the chance of developing malnutrition and other complications. The existence of reliable gluten free food is crucial to the well-being of the population. Here we report on a microfluorimeter device for the in situ detection of gliadin in foodstuffs, which could be used for a rapid control of raw materials in food processing, as well as for process control of gliadin contamination. The microfluorimeter is based on a reflector that is used inside a microfluidic chip, exploiting various strategically placed reflective or totally metallised mirrors for efficient collection of the fluorescent light emitted in a large solid angle. The chip is capable of executing five assays in parallel and has been demonstrated to possess detection sensitivity applicable to fluoroimmunoassays. Various immunoassay formats exploiting fluorescence detection, using enzyme/fluorophore labels were developed and compared in terms of sensitivity, ease of assay, assay time and compatibility with buffer used to extract gliadin from raw and cooked foodstuffs, with the best performance observed with an indirect competition assay using a fluorophore-labelled anti-mouse antibody. This assay was exploited within the microfluorimeter device, and a very low detection limit of 4.1 ng/mL was obtained. The system was observed to be highly reproducible, with an RSD of 5.9%, for a concentration of 50 ng/mL of gliadin applied to each of the five channels of the microfluorimeter. Biofunctionalised disposable strips incorporated into the microfluorimeter were subjected to accelerated Arrhenius thermal stability studies and it was demonstrated that strips pre-coated with gliadin could be stored for approximately 2 years at 4 degrees C, with no discernable loss in sensitivity or detectability of the assay. Finally, the microfluorimeter was applied to the analysis of commercial gluten-free food samples, and an excellent correlation with routine ELISA measurements was obtained. The developed microfluorimeter should find widespread application for on-site execution of fluoroimmunoassays.

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