Wednesday, 21 May 2014

Molecular and Immunological Characterization of Gluten Proteins Isolated from Oat Cultivars That Differ in Toxicity for Celiac Disease

Molecular and Immunological Characterization of Gluten Proteins Isolated from Oat Cultivars That Differ in Toxicity for Celiac Disease

This is an exert from the US National Library of Medicine – National Institute of Health published Dec 2012

Cultivated oats are hexaploid cereals belonging to the genus Avena L., which is found worldwide in almost all agricultural environments (reviewed by [11]). Recently, oats have been receiving increasing interest as human food, mainly because the cereal could be suitable for consumptions by celiac patients[12]. Oats have other nutritional attributes such as those derived from β-glucan content [13], or the protein amino acid composition [14].

The inclusion of oats in “gluten-free” foods is controversial, as previous studies have shown contradictory results on its toxicity. Some researchers claim that celiac patients can tolerate oats without signs of intestinal inflammation [12]. However, other studies confirm the toxicity of oats in certain types of celiac patients [15], [16]. More recently, the utility of the G12 antibody to identify potentially toxic oat varieties for celiac patients has been reported [17]. This finding allowed classification of oat varieties into three groups based in their degree of affinity for the G12 antibody: a highly recognized group, one of moderate recognition, and one with no reactivity [17]. The reactivity that T-cells isolated from celiac patients exhibited with three oat varieties (one from each of the classified groups) correlated directly with the moAb G12 reactivity. The diversity observed in the reactivity to the different oat cultivars suggests variations in the avenin composition, and therefore in the amount of immunotoxic epitopes similar to the 33-mer present in these varieties.

In comparison with wheat gliadins, the avenins have been little studied, and the number of full avenin genes present at the moment in the databases is limited and from few genotypes, so that the variability of avenin genes in oats is not well represented. With this background, the aim of the present work was to obtain further gene sequences from different toxic and non-toxic varieties of oats in order to provide more information on the structure of avenin genes and on the evolutionary relationships with the prolamins and glutenins of wheat and other cereals. It also would facilitate the identification of toxic epitopes described in other cereals that might be present in oats. Furthermore, these sequences could lead to the discovery of new undescribed toxic epitopes in cereals and explain why certain varieties of oats are toxic for celiac patients and others are not. In this work we demonstrate that oat grains have both monomeric and polymeric avenins, designated in this paper gliadin- and glutenin-like avenins. We found a direct correlation between the immunogenicity of the different varieties of oats and the presence of the specific peptides with a higher/lower potential immunotoxicity. Our results suggest that there is a wide range of variation in the potential immunotoxicity of oat cultivars that could be due to differences in the degree of immunogenicity in their sequences.

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