Researchers Use RNA-amplicon Sequencing to Spot Differences in Celiac Disease Epitopes in Durum Wheat Varieties

Celiac.com 02/04/2014 - According to a new article by a team of researchers, not all gluten protein is created equal. That is, not all gluten proteins trigger an immune response in people with celiac disease.

The research team included Elma M.J. Salentijn, Danny G. Esselink, Svetlana V. Goryunova, Ingrid M. van der Meer, Luud J.W.J. Gilissen, and Marinus J.M. Smulders. They are variously affiliated with the Plant Research International in Wageningen, The Netherlands, and the Vavilov Institute of General Genetics at the Russian Academy of Sciences in Moscow, Russia.

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Gluten proteins are the source of peptides that can trigger a T cell reaction in celiac disease patients, leading to inflammatory responses in the small intestine. Various peptides with three major T cell epitopes involved in celiac disease are derived from alpha-gliadin fraction of gluten. Numerous factors are known to influence the immunogenicity of individual gene family members, as alpha-gliadins are encoded by a large multi-gene family and amino acid variation in the celiac disease epitopes. That means that some wheat strains are more likely to trigger celiac disease, and other are less likely.

Current commercial methods of gluten detection cannot tell the difference between immunogenic and non-immunogenic celiac epitope variants, and thus cannot accurately measure the overall celiac epitope load of a given wheat strain. Being able to tell the difference between what types of wheat have a lower likelihood to cause or trigger celiac disease is important to commercial wheat growers and producers.

The team developed a 454 RNA-amplicon sequencing method for alpha-gliadin transcripts that includes the three major celiac disease epitopes and their variants. They used the method to screen 61 different durum wheat cultivars and accessions. They found a total of 304 unique alpha-gliadin transcripts, corresponding to a total of 171 ‘unique deduced protein fragments’ of alpha-gliadins.

They used the numbers of these fragments obtained in each plant to calculate quantitative and quantitative differences between the celiac epitopes expressed in the endosperm of these wheat plants. A small number of wheat plants showed a lower ratios of celiac epitope-encoding alpha-gliadin transcripts, though none were entirely free of celiac epitopes.

Dedicated 454 RNA-amplicon sequencing allows researchers to group wheat plants according to the genetic variation in alpha-gliadin transcripts, and to screen for plants which are potentially less likely to trigger or promote celiac disease.

The alpha-gliadin sequence database the team constructed will provide an important reference in proteomics analysis regarding the immunogenic potential of mature wheat grains.

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