Spreading of Wheat Protein Allergens During Natural Evolution and Human Selection of Wheat Species.

Background. Wheat genomes from different relatives naturally summed to originate new species; furthermore, over the last 12,000 years the natural evolution of wheat has been heavily perturbed by the activity of humans striving for more productive and resistant plants. As a consequence, the evolution of wheat species is highly discontinuous, being characterized by interspecific crosses and amphidiploids development; in particular, for Triticum aestivum (breadwheat) this process was carried out within a relatively small time period. Wheat proteins may lead to different allergic diseases like food allergy, exercise-induced anaphylaxis (WDEIA) and baker’s asthma. In particular we focused on the latter inhalatory disease as a model of a typical IgE mediated allergy in which allergens are well characterized. Method. Sera from 7 allergic bakers (group 1), 7 healthy exposed workers (group 2) and 7 non-exposed volunteers (group 3), were pooled and utilized to carry out IgE-blots on salt-soluble protein fraction from modern wheats and their ancestors. In order to minimize experimental variability the protein fractions were obtained from the seeds of various accessions from different countries for each wheat species. Data were quantified by densitometric analysis. Results. Sera from groups 2 and 3 showed no IgE reactivity against salt soluble proteins. A different pattern of IgE reactivity was observed for group 1 when protein extracts were separated under reducing or non reducing conditions, especially for amylase inhibitors, that are considered the major wheat allergens. Under non reducing conditions, that better approximate the environmental conditions in human lungs, most proteins recognized by IgE appear to derive from a graminaceous plant, the wild Triticum tauschii, which is the acknowledged donor of the D genome to the modern hexaploid Triticum aestivum (AABBDD). An evolutionary tree, drawn on the basis of densitometric data, shows the allergenic potential of all considered species. Conclusion. Our “allergomic” approach demonstrates that human selection has influenced the spreading of allergens in modern wheat species. Specific IgE were detected in allergic bakers only, whereas no specific IgE were detected in healthy exposed bakers and non-exposed volunteers. This data needs confirm in a large cohort of wheat exposed workers.