Towards reducing the immunogenic potential of wheat flour: Omega gliadins encoded by the D genome of hexaploid may also harbor epitopes for the serious food allergy WDEIA

Authors: Altenbach, Susan; Chang, Han-Chang; Simon-Buss, Annamaria; JANG, YOU-RAN - National Institute For Agricultural Science & Technology; DENERY-PAPINI, SANDRA - Institut National De La Recherche Agronomique (INRA); PINEAU, FLORENCE - Institut National De La Recherche Agronomique (INRA); Gu, Yong; HUO, NAXIN - University Of California, Davis; LIM, SUN-HYUNG - National Institute For Agricultural Engineering - Korea; KANG, CHON-SIK - Rural Development Administration - Korea; LEE, JONG-YEOL - Rural Development Administration - Korea

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2018
Publication Date: 11/21/2018
Citation: Altenbach, S.B., Chang, H., Simon-Buss, A., Jang, Y., Denery-Papini, S., Pineau, F., Gu, Y.Q., Huo, N., Lim, S., Kang, C., Lee, J. 2018. Towards reducing the immunogenic potential of wheat flour: Omega gliadins encoded by the D genome of hexaploid may also harbor epitopes for the serious food allergy WDEIA. Biomed Central (BMC) Plant Biology. 18:291. https://doi.org/10.1186/s12870-018-1506-z.
DOI: https://doi.org/10.1186/s12870-018-1506-z

Interpretive Summary: The gluten proteins are a complex group of proteins in wheat flour that are responsible for the unique viscoelastic properties that make it possible to produce a wide range of different food products from the flour. Some of these proteins are also responsible for human health problems, including food allergies and celiac disease. In this work, a mutant wheat line was identified that produced flour missing the omega-5 gliadins, a group of gluten proteins that trigger a severe form of food allergy. Detailed analysis of the proteins accumulated in the flour revealed that a number of other gluten proteins were also missing in the mutant line due to the deletion of a large portion of one of the wheat chromosomes. Flour from the mutant showed less reactivity with sera from patients with confirmed cases of wheat allergy, suggesting that the flour was less likely than the non-mutant lines to induce an allergic reaction. However, the sera also reacted with several minor proteins that weren’t readily apparent in the first analysis. These proteins were confirmed to be omega-5 gliadins encoded on a different chromosome. The work illustrates some of the challenges faced in using breeding approaches to reduce the allergenicity of wheat flour and highlights the importance of detailed knowledge about the major gluten protein genes in individual wheat cultivars for these research efforts.

Technical Abstract: Omega-5 gliadins are a group of highly repetitive gluten proteins in wheat flour encoded on the 1B chromosome of hexaploid wheat. These proteins are the major sensitizing allergens in a severe form of food allergy called wheat-dependent exercise-induced anaphylaxis (WDEIA). The elimination of omega-5 gliadins from wheat flour through biotechnology or breeding approaches could reduce the immunogenic potential and adverse heath effects of the flour. A mutant line missing low-molecular weight glutenin subunits encoded at the Glu-B3 locus was selected previously from a doubled haploid population generated from two Korean wheat cultivars. Analysis of flour from the mutant line by 2-dimensional gel electrophoresis coupled with tandem mass spectrometry revealed that the omega-5 gliadins and several gamma gliadins encoded by the closely linked Gli-B1 locus were also missing due to a deletion of at least 5.8 Mb of chromosome 1B. Two-dimensional immunoblot analysis of flour proteins using sera from WDEIA patients showed reduced IgE reactivity in the mutant relative to the parental lines due to the absence of the major omega-5 gliadins. However, two minor proteins showed strong reactivity to patient sera in both the parental and the mutant lines and also reacted with a monoclonal antibody against omega-5 gliadin. Analysis of the two minor reactive proteins by mass spectrometry revealed that both proteins correspond to omega-5 gliadins encoded on chromosome 1D. While breeding approaches can be used to reduce the levels of the highly immunogenic omega-5 gliadins in wheat flour, these approaches are complicated by the genetic linkage of different classes of gluten protein genes and the finding that omega-5 gliadins may be encoded on more than one chromosome. The work further illustrates the importance of detailed knowledge about the genomic regions harboring the major gluten protein genes in individual wheat cultivars for future efforts aimed at reducing the immunogenic potential of wheat flour.