Cell-based immunological assay: complementary applications in evaluating the allergenicity of foods with FAO/WHO guidelines

Digestion-Resistant Linear Epitopes as Dominant Contributors to Strong Allergenicity of Tropomyosin in Antarctic Krill (Euphausia superba)

Although tropomyosin has been identified as a major allergen in Antarctic krill, the digestive fate of Antarctic krill tropomyosin and its relationship with allergenicity are unknown. In this study, Antarctic krill tropomyosin was administered to BALB/c mice via both gavage and intraperitoneal injection to explore its sensitizing and eliciting capacity, and its digestion products were analyzed for structural changes and digestion-resistant linear epitopes. Mice gavaged with tropomyosin exhibited lower levels of specific IgE and IgG1, mast cell degranulation, vascular permeability, and anaphylaxis symptoms than those in the intraperitoneal injection group. This may be due to the destruction of macromolecular aggregates, loose expansion of the tertiary structure, complete disappearance of α-helix, and significant changes in molecular force upon the digestion of tropomyosin. Nevertheless, the intragastric administration of Antarctic krill tropomyosin still triggered strong allergic reactions, which was attributed to the existence of seven digestion-resistant linear epitopes (Glu26-His44, Thr111-Arg125, Glu157-Glu164, Glu177-Gly186, Val209-Ile225, Arg244-Arg255, and Val261-Ile270).

Evaluation of the structure-activity relationship between allergenicity and spatial conformation of ovalbumin treated by pulsed electric field

The aim of the present study was to investigate the effect of pulsed electric field (PEF) treatment on ovalbumin (OVA) induced allergens and reveal potential allergy regulatory mechanisms. At 10 kV/cm, OVA-induced allergic symptoms were significantly reduced, and the capacity of OVA to bind with specific IgG1 and IgE was reduced by 10.32% and 3.61%, respectively. Furthermore, the degranulation of RBL-2H3 cells and allergen activity were also reduced by 4.63% and 22.15%, respectively. Interestingly, the α-helix content was reduced by 5.81% and the fluorescence intensity was increased by 6.90% with PEF treatment. At 10 kV/cm, water contact angle and surface hydrophobicity increased by 8.40% and 0.18%, respectively, indicating that PEF treatment increased the exposure of hydrophobic amino acid residues. PEF treatment alters the hydrogen bonding and hydrophobic interactions in the protein, which masks the binding sites of sensitized epitopes, and consequently reduces allergies.

Reducing the allergenicity of pea protein based on the enzyme action of alcalase

Enzymatic hydrolysis could be one of the crucial means to limit the allergenicity of allergens. The allergenicity of pea peptides was evaluated using indirect ELISA and RBL-2H3 cell assay, thereby obtaining hypoallergenic pea peptide sequences. Results indicated that pea protein-sensitized mice produced higher levels of total IgG1 and IgE antibodies than the mice in the control group (P < 0.05). Moreover, the allergenicity of hydrolysates decreased significantly after enzymolysis, and the allergenicity of ultrafiltration component F1 and purified component F1-2 was significantly lower than that of other isolated and purified components (P < 0.05). Furthermore, ADLYNPR identified from F1-2 had lower binding capacity to specific IgE and IgG1 and lower degree of cell degranulation with a higher EC50 value of 6.63 ng mL-1, which was about 36.83 times that of pea protein (P < 0.05). Based on the above results, ADLYNPR might be a potential source of hypoallergenic peptides.

Anti-allergic activity of glycyrrhizic acid on IgE-mediated allergic reaction by regulation of allergy-related immune cells

Glycyrrhizic acid (GA), the major bioactive triterpene glycoside of glycyrrhiza, has been shown to possess a wide range of pharmacological properties, including anti-inflammatory and anti-viral properties. However, few studies have examined the anti-allergic activity and exact mechanism of action of GA. In the present work, the anti-allergic activity and possible mechanisms of action of GA on an immunoglobulin (Ig) E-mediated allergic reaction has been studied using three models of allergic reaction in vivo and in vitro. Active systemic allergic reaction in Balb/c mice showed that GA can suppress the increased level of IL-4 to restore the immune balance of TH1/TH2 cells in a dose-dependent manner. Additionally, GA attenuated significantly the B cells producing allergen-specific IgE and IgG1 partly because of the low levels of TH2 cytokines. Both passive cutaneous anaphylaxis in vivo and an RBL-2H3 cell-based immunological assay in vitro indicated that GA acted as a "mast cell stabilizer", as it inhibited mast cell degranulation and decreased vascular permeability by inhibiting the expression of Orai1, STIM1 and TRPC1, which blocked extracellular Ca2+ influxes. The current study suggests that GA may serve as an effective anti-allergic agent derived from food for the prevention and treatment of IgE-mediated allergic reaction.

Potential allergenicity response to structural modification of irradiated bovine α-lactalbumin

Bovine α-lactalbumin (α-La) is a major food allergen found in milk and is characterized by high conformational stability because of its four disulfide bridges and being calcium bound.

A modified weight-of-evidence approach to evaluate the allergenic potential of food proteins

Schematic interpretation of a modified weight-of-evidence approach for evaluating the allergenic potential of food proteins.