Comparing wheat allergenicity in ancient and modern wheats
To characterize the wheat gluten protein complex from a historical set of 37 CWRS wheat varieties to study changes in glutenin and gliadin subunits over time.
Wheat is an important Canadian crop, that is consumed around the world in a culturally and ethically
determined products. The diversity of products from wheat flour is due to the viscoelastic gluten complex that is formed during the dough making process. Gluten is made up of glutenins and gliadins, the later also being responsible for Celiac disease that occurs in the population that is genetically predisposed. However, in the recent past, it has been suggested that the wheat grain composition, especially the gluten concentration has increased and it is responsible for the increased incidence of Celiac disease and/ or wheat sensitivity. The main objective of the study was to scientifically address the question, by studying changes in wheat grain protein concentration, glutenin and gliadin composition over one and half century of wheat improvement in Canada.
The second objective was to analyze any changes in the reactivity of wheat grain glutenin and gliadin that causes the Celiac disease, in wheat cultivars released over the years. The third objective was to analyze the differences in the grain gluten polypeptides in the current market classes of wheat with special emphasis ontheir reactivity to antibodies present in the serum of celiac patients. The last objective was to screen the immunogenic reactivity of gluten proteins in the representatives of ancient wheat.
To achieve these objectives a set of 37 wheat genotypes that included representative cultivars released from 1860 to 2007. Samples from four years of trials (2013, 2014, 2016 and 2017) were analyzed in this study. For the representatives of modern cultivars, 107 cultivars belonging to the seven market classes were analyzed from the 2017 harvest. Twelve subjects with different degree of Celiac diseases staged by the Marsh score were selected from the database maintained at the Centre of Excellence for Gastrointestinal Inflammation and Immunity Research (CEGIIR) at the University of Alberta, Edmonton.
The grain polypeptides from the historical wheat set were extracted and analyzed for total proteins,
monomeric, polymeric and the ratio of monomeric to polymeric proteins. These affect the baking quality of the flour. The grain polypeptides were analyzed by SDS-PAGE to characterize the subunit structures of glutenins and gliadins. Phylogenetic analysis by constructing a dendrogram revealed that the 37 genotypes were intermixed and did not follow a set pattern dependent upon the year of release. Immunoblot analyses, using a commercial antigliadin serum or serum from the different Celiac patients, also showed no definite trends of immunoreactivity with years or Celiac disease severity. Although the immunoblots showed some background, but the results do not show any trends that Celiac causing wheat grain polypeptides have increased over the years. We also could not detect any wheat grain polypeptide that could be associated with increased Celiac disease severity. No significant variation in Celiac disease- causing polypeptides could be observed in the different market classes of wheat. Celiac causing wheat polypeptides were also observed in the three ancient wheats tested in this study. In conclusion, the results suggest that the Celiac causing wheat proteins have been present in wheat and the results do not show that there has been an increase in the Celiac causing polypeptides due to wheat improvement over the years. This study has shown the feasibility of using Celiac patient’s serum to characterize the wheat gluten polypeptides. More precise studies need to be done to completely characterize the relationship between wheat gluten polypeptides and Celiac disease.
- Analysis of wheat gluten proteins did not separate wheat genotypes based on the year of
- Wheat gluten proteins recognized antibodies present in Celiac patient serum.
- No specific wheat gluten protein could be associated with Celiac disease severity.
- Celiac immunoreactive proteins were also found in ancient wheats such as emmer, einkorn or