Gliadin and Glutenin - Gluten Allergens

Wheat is the most widely consumed food grain in the world. Wheat proteins are categorized into four fractions based on their solubility in solvents: water (albumins), water containing salt (globulins), alcohol (gliadins), and alkali or acid solution (glutenin)(1).  Among these proteins, gliadin and glutenin contain highly antigenic repeated amino acid sequences which potentially activate both the innate and adaptive immune responses. These activated immune responses lead to immune-mediated injury to the intestines, such as intestinal permeability and inflammation due to infiltration of the lamina propria. Therefore, gliadin and glutenin have been implicated in triggering celiac disease (CD), an autoimmune disease, in genetically susceptible individuals (2), and in inducing mouse gluten allergy models (3) .

To study the pathogenesis of gluten allergens in mouse allergy models, Chondrex, Inc. offers hydrolyzed gliadin and hydrolyzed glutenin for use in both in-vitro and in-vivo research. These hydrolyzed allergens are more soluble in neutral buffers, making them easier to handle and use. Chondrex, Inc. also provides gliadin detection ELISA kits, mouse anti-gliadin antibody ELISA kits, as well as cytokine detection ELISA kits, and chemokine detection ELISA kits to measure immune responses in mouse gluten allergy studies.

For more details about mouse gluten allergy models, please refer to the Table of Contents below. If you have any questions regarding Chondrex, Inc.'s Mouse Allergic Disease Models, please contact us at support@chondrex.com.

What are Gliadin and Glutenin? (4-6)

Wheat contains 8%-15% protein, of which 10%-15% is albumin/globulin and 85%-90% is gluten. Gluten is mainly composed of gliadin and glutenin, which are classified as prolamins due to their high content of the amino acids glutamine (38%) and proline (20%) and their solubility in ethanol despite being insoluble in water.

Gliadin is further classified into alpha, beta, gamma, and omega gliadins based on differences in primary structure, with molecular weights (MW) ranging from 28 - 55kDa.  The proline-rich sequences of gliadin result in tightly packed structures that are highly resistant to proteolytic digestion in the gastrointestinal tract, which can trigger adverse immune reactions in individuals with celiac disease.

Glutenin is known for its insolubility in common solvents and ability to form aggregates. Glutenin, whose MW ranges from 30-140 kDa, is divided into two groups: high molecular weight (HMW) glutenin subunits (90-140 kDa), which play a critical role in gluten's functionality, and low molecular weight (LMW) glutenin subunits (30-75 kDa), which are partially soluble in 70% ethanol and share similarities with some gliadins.

Gliadin and Glutenin Related Diseases in Humans (4, 7-9)

Wheat is a factor which can cause gastrointestinal symptoms including wheat allergy, celiac disease (CD), and non-celiac gluten sensitivity. CD is an immune-mediated disorder triggered by dietary gluten, which induces an immune responses that cause mucosal inflammation and increase gut permeability. CD has appeared in susceptible patients carrying specific genetic dispositions of human leukocyte antigen (HLA)-DQ2 or DQ8.14. These patients often show high levels of serum antibodies against amino acid (AA) sequences (QQFPQQQ, QQIPQQQ, and QQLPQQQ) found in ω-5 gliadin and AA sequences (QQPGQ, QQPGQGQQ, and QQSGQGQ) in HMW-glutenin. 

Wheat allergy, on the other hand, occurs by an IgE-mediated reaction to gluten. Symptoms such as itching, swelling, skin rash, and life-threatening anaphylaxis typically appear within minutes to hours of gluten exposure. Long-term problems may include baker's asthma, rhinitis, atopic dermatitis, urticaria, and wheat-dependent exercise-induced anaphylaxis. Non-celiac gluten sensitivity is considered a syndrome that occurs in a heterogeneous group of patients with similar gastrointestinal and extra-intestinal symptoms, as well as clinical histories and characteristics.

Hydrolyzed Gliadin and Glutenin

Hydrochloric acid (HCl)-treated wheat protein (HWP) is commonly used in various consumer products, including food, cosmetics, and shampoos. However, recent reports have raised concerns about immediate allergic reactions, particularly in response to facial soaps containing HWP. Treating wheat protein with HCl induces hydrolysis, breaking down both the main-chain amide bonds (peptide-bond hydrolysis) and the side-chain bonds (deamidation). This alters the structure of the wheat protein (10).

Transdermal exposure to HWP can activate immune pathways, leading to sensitization and allergic reactions. Studies in mice suggest HWP has a similar potential to induce allergic reactions as gluten, although its allergenicity may vary. One notable effect of HCl treatment is the increased solubility of HWP which enhances its susceptibility to pepsin digestion (11). Additionally, hydrolyzed proteins like HWP exhibit enhanced transdermal permeability,  potentially triggering allergic and immune responses(12). These findings suggest that HWP in skin-applied products pose potential allergenic risk, especially for individuals sensitive to wheat or gluten.

Therefore, hydrolyzed gliadin and glutenin are valuable allergens that can be substituted with native forms in studies investigating allergic reactions to gluten, including baker's allergy.

3) Oral Immunization Only (16)
BALB/c mice are challenged with oral gavage with gliadin (5 mg/daily for 1 week, then 5 mg/daily thrice a week for 3 weeks) for 4 weeks. At the end of the fourth week, the mice are challenged with gliadin every day via oral gavage for another 2 weeks.

2) Immunization Only(18)

BALB/c mice are sensitized with 10 μg of Gliadin adsorbed with aluminum hydroxide by intraperitoneal injection at days 0, 14, 28, and 42.

Evaluating Wheat-Gluten Allergy Models

In a wheat-gluten allergy mouse model, serum histamine levels, a marker of mast cell degranulation, were significantly higher than controls. Serum IgG1 and IgE antibody levels against gliadin or glutenin were also significantly higher. In addition, serum cytokine levels showed increased IL-4 (Th2 cytokine), but not IFN-g, IL-12 (Th1 cytokine), IL-17 (Th17 cytokine), IL-10, and TGF-b (regulatory T cytokine) levels (13, 14). These results suggest that a Th2 response plays a dominant role in the development of the disease in mice.  In another gliadin model, intestinal permeability was evaluated by FITC-dextran 4kDa (16). Therefore, appropriate markers for evaluating mouse gluten allergy models should be selected according to induction protocols.

In addition to gluten allergen antibody assay kits, Chondrex, Inc. also provides several molecular sizes of fluorescein labeled dextran, cytokine detection ELISA kits, and chemokine detection ELISA kits to evaluate wheat-gluten allergy mouse models.