Table of Contents

Whole Allergen

f79 Gluten

f79 Gluten Scientific Information

Type:

Whole Allergen

Display Name:

Gluten

Route of Exposure:

Ingestion

Family:

Poaceae

Species:

Triticum aestivum

Other Names:

Gluten from wheat (Triticum aestivum)

Summary

Wheat is the most widely consumed food grain in the world. The wheat kernel contains approximately 8-15% protein content of which 85%–90% is gluten. Gluten is made up of insoluble gliadins as well as high and low molecular weight glutenins, which are responsible for IgE-mediated reactions in wheat allergy, affecting an estimated 0.4% of the world’s population. Symptoms of wheat allergy usually develop within minutes to hours after ingestion and affect the GI tract (vomiting, colic, diarrhea), skin (urticaria, eczema), respiratory tract (upper respiratory, asthma), or include systemic anaphylactic reactions. Symptoms can also manifest as baker’s asthma (from inhaled flour), atopic dermatitis (from skin exposure), urticaria (forming hives after skin exposure), or wheat-dependent exercise-induced anaphylaxis).

Allergen

Nature

Gluten is the main storage protein in wheat (Triticum aestivum) and is the most widely consumed food grain in the world. It is cultivated worldwide due to its ability to grow in many different climatic areas (1) (2).

The wheat kernel contains 8–15% protein, of which 10–15% is albumin/globulin 85%–90 % is gluten. Gluten is a mixture of hundreds of related but distinct proteins, consisting mainly of gliadin and glutenin. Gluten is heat stable and can act as a binding and extending agent, and is therefore commonly used as an additive in processed foods to improve texture, flavor, and moisture retention. As a result, gluten can be found in many other food types, including processed meat, reconstituted seafood, vegetarian meat substitutes, candies, ice cream, butter, seasonings, stuffings, marinades and dressings, as well as coatings in medications and confectionary (1).

Proteins similar to gliadin in wheat are found in other grains, existing as secalin in rye, hordein in barley, and avenins in oats, where they are collectively referred to as “gluten.” Additionally, the derivatives of these grains such as triticale and malt also contain gluten. The gluten found in all of these grains has been identified as the component capable of triggering the immune-mediated disorder, celiac disease (1). The albumin/globulin protein group in wheat is mostly responsible for allergic reactions including wheat allergy and occupational Baker’s asthma/rhinitis. Wheat allergic subjects can also be sensitized to high and low molecular weight glutenins (2). The (omega-5) gliadin fraction of gluten is the most common allergen implicated in food-dependent, exercise-induced anaphylaxis (3).

Taxonomy

Taxonomic tree of Wheat (4)
Domain	Eukaryota
Kingdom	Plantae
Phylum	Tracheophyta
Subphylum	Spermatophytina
Class	Magnoliopsida
Order	Poales
Family	Poaceae
Genus	Triticum

Epidemiology

Worldwide distribution

An estimated 0.4% of the world’s population are allergic to wheat proteins, where the majority of cases are children, where most (45-69%) become tolerant to wheat by age 6. Omega-5 gliadin is implicated in severe immediate-type reactions in children and wheat-dependent, exercise-induced anaphylaxis (2, 3, 5). The prevalence of wheat allergy does vary according to age and location. It has been cited as the third most common allergen in Germany, Japan, Finland, and in preschool children in the USA. In Europe overall, the prevalence is estimated to be less than 1 % (2).

Pediatric issues

In children with wheat allergy, atopic disorders often coexist with atopic dermatitis (53–87%), asthma (48–75%), and allergic rhinitis (34–62%) is often present. About 90% of infants are also allergic to other foods, most commonly cow’s milk and/or egg, and less frequently fish, soya, and nuts. Grass sensitization is associated with an increased risk for wheat sensitization over time. In children with specific IgE to Phl p12 (profilin) and to MUXF3 CCD (Cross-reactive Carbohydrate Determinant), cross-reactivity to grass–wheat appears to be more common. Additional studies have hypothesized a number of possible environmental factors that may affect the risk of developing wheat allergy, such as delaying exposure to wheat and breastfeeding, with inconclusive results (2).

Route of Exposure

Main

Ingestion.

Secondary

Inhalation and skin exposure (1).

Clinical Relevance

Gluten-related disorders typically include wheat allergy, celiac disease and the suggested condition of non-celiac gluten sensitivity (Biesiekierski, 2017).

Wheat allergy is an IgE-mediated reaction to the insoluble gliadins that make up gluten in wheat (Biesiekierski 2017). Wheat allergic subjects can also be sensitized to high and low molecular weight glutenins (Ricci et al, 2019).

The symptoms usually develop within minutes to hours after ingestion and usually affect the GI tract (vomiting, colic, diarrhea), skin (urticaria, eczema), respiratory tract (upper respiratory, asthma), or multiple systems (anaphylaxis) (1, 3). Symptoms can also manifest as Baker’s asthma and rhinitis (from inhaled flour), atopic dermatitis (from skin exposure), urticaria (forming hives after skin exposure), or wheat-dependent exercise-induced anaphylaxis (when wheat is consumed before vigorous physical activity) (1).

Prevention and Therapy

Allergen immunotherapy

The efficacy and safety of vital wheat gluten (gluten separated from wheat) oral immunotherapy was assessed in a randomized controlled trial in 46 patients with wheat allergy aged 4.2–22.3 years. Both low and high-dose immunotherapy induced desensitization in about 50 % of the subjects after 1 year of treatment. After two years, low-dose immunotherapy resulted in 30 % desensitization, and 13 % of patients had sustained unresponsiveness. Among 7822 treatments with low-dose immunotherapy in the first year, 15.4 % were associated with adverse reactions, of which 0.04% were classed as severe. Amongst 7921 placebo doses, 5.8 % were associated with adverse reactions with no severe reactions (6).

Prevention strategies

Avoidance

The mainstay of management for wheat allergy is dietary avoidance (2).

Molecular Aspects

Allergenic molecules

Table adapted from Allergome.org (7):

Allergen	Type	Mass (kDa)
Tri a 19	Gliadin	65
Tri a 21	α/β Gliadin	32.7
Tri a α gliadin	Gliadin	33
Tri a β gliadin	Gliadin	32.9
Tri a Gliadin	Gliadin	65
Tri a ω2 gliadin	Gliadin	30

Gliadin contains epitopes that are highly resistant to proteolytic digestion in the gastrointestinal tract, due to the high content of the amino acids, proline and glutamine, which many proteases are unable to cleave (1).

Wheat-allergic patients have been shown to be sensitized to alpha, beta, gamma and/or omega globulins and to high- and low-molecular-weight glutenins, which are constituents of gluten (2).

Tri a 19 is a water-insoluble omega-5-gliadin, which has been identified as a major allergen in subjects with wheat-dependent exercise-induced anaphylaxis (2).

Cross-reactivity

At the time of writing, there is limited information on gluten (either gliadin or glutenin) cross-reactivity.

Compiled By

Author: RubyDuke Communications

Reviewer: Dr.Michael Thorpe

Last reviewed: May 2022

References

Biesiekierski JR. What is gluten? J Gastroenterol Hepatol. 2017;32 Suppl 1:78-81.
Ricci G, Andreozzi L, Cipriani F, Giannetti A, Gallucci M, Caffarelli C. Wheat Allergy in Children: A Comprehensive Update. Medicina (Kaunas). 2019;55(7).
Burkhardt JG, Chapa-Rodriguez A, Bahna SL. Gluten sensitivities and the allergist: Threshing the grain from the husks. Allergy. 2018;73(7):1359-68.
ITIS. Triticum L. 2021 [cited 2021 13.12.21]. Available from: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=42236#null.
Kucek LK, Veenstra LD, Amnuaycheewa P, Sorrells ME. A Grounded Guide to Gluten: How Modern Genotypes and Processing Impact Wheat Sensitivity. Comprehensive Reviews in Food Science and Food Safety. 2015;14(3):285-302.
Nowak-Węgrzyn A, Wood RA, Nadeau KC, Pongracic JA, Henning AK, Lindblad RW, et al. Multicenter, randomized, double-blind, placebo-controlled clinical trial of vital wheat gluten oral immunotherapy. J Allergy Clin Immunol. 2019;143(2):651-61.e9.
Allergome.org. Gluten 2021 [cited 2021 13.12.21]. Available from: http://www.allergome.org/script/search_step2.php.