Digestion differently affects the ability of native and thermally aggregated ovalbumin to trigger basophil activation.

Ovalbumin (OVA), a major allergen from hen's egg albumen, tends to aggregate when heated. Depending on the balance of attractive and repulsive interactions, heat-induced OVA aggregates have various morphologies, which differ in digestibility. In the context of food allergy to egg, we investigated the ability of native and thermally aggregated OVA as well as their digests to induce the degranulation of a humanized rat basophil leukemia (RBL) cell line, which was sensitized with a pool of sera from egg-allergic children. Native and two thermally aggregated OVA forms were digested in vitro using a gastrointestinal digestion model based on the INFOGEST harmonized protocol including a final degradation with jejunal brush border membranes (BBM) enzymes. The course of digestion was monitored by the OPA method and by RP-HPLC. Digestibility was OVA small aggregates>OVA large aggregates>>native OVA and BBM peptidases only significantly hydrolyzed small-sized peptides from gastro-duodenal digests of the aggregates. The degranulation ability of the native OVA slightly changed during the gastric phase but mostly decreased during the duodenal digestion with no further change with BBM digestion. The degranulation ability of aggregates, which was significantly lower than the ability of native OVA, was not significantly affected by digestion. Digestibility and ability to induce basophil degranulation can thus not be straightforward linked.

Acid-Hydrolyzed Gliadins Worsen Food Allergies through Early Sensitization.

SCOPE: Food allergies result from a complex immune response involving both innate and adaptive immune cells. Major proteins of wheat flour, gliadins, appear to be important allergens, and their characteristics can influence the allergic response. This study investigates the immune reaction when developing a food allergy to gliadins in native, deamidated, or hydrolyzed forms. METHODS: The immune response after one or two intraperitoneal sensitizations and after oral challenge with each gliadin form is analyzed. RESULTS: Results demonstrate that deamidated gliadins induce a stronger allergic reaction compared to native gliadins. Moreover, deamidation induces an earlier increase in intestinal permeability associated with more pronounced Th2 and Th17 polarizations together with an influx of antigen-presenting cells, especially cDC2. CONCLUSION: Altogether, Results indicate that industrial processes such as deamidation or hydrolysis influences food allergenicity through immune modulation and helps us to develop tools to determine how these processes can influence this reaction and encourage or decrease allergic reactions.

How Proteins Aggregate Can Reduce Allergenicity: Comparison of Ovalbumins Heated under Opposite Electrostatic Conditions.

Heated foods are recommended for avoiding sensitization to food proteins, but depending on the physicochemical conditions during heating, more or less unfolded proteins aggregate differently. Whether the aggregation process could modulate allergenicity was investigated. Heating ovalbumin in opposite electrostatic conditions led to small (A-s, about 50 nm) and large (A-L, about 65 µm) aggregates that were used to sensitize mice. The symptoms upon oral challenge and rat basophil leukemia degranulation with native ovalbumin differed on the basis of which aggregates were used during the sensitization. Immunoglobulin-E (IgE) production was significantly lower with A-s than with A-L. Although two common linear IgE-epitopes were found, the aggregates bound and cross-linked IgE similarly or differently, depending on the sensitizing aggregate. The ovalbumin aggregates thus displayed a lower allergenic potential when formed under repulsive rather than nonrepulsive electrostatic conditions. This further demonstrates that food structure modulates the immune response during the sensitization phase with some effects on the elicitation phase of an allergic reaction and argues for the need to characterize the aggregation state of allergens.

Milk Polar Lipids Affect In Vitro Digestive Lipolysis and Postprandial Lipid Metabolism in Mice.

BACKGROUND: Polar lipid (PL) emulsifiers such as milk PLs (MPLs) may affect digestion and subsequent lipid metabolism, but focused studies on postprandial lipemia are lacking. OBJECTIVE: We evaluated the impact of MPLs on postprandial lipemia in mice and on lipid digestion in vitro. METHODS: Female Swiss mice were gavaged with 150 µL of an oil-in-water emulsion stabilized with 5.7 mg of either MPLs or soybean PLs (SPLs) and killed after 1, 2, or 4 h. Plasma lipids were quantified and in the small intestine, gene expression was analyzed by reverse transcriptase-quantitative polymerase chain reaction. Emulsions were lipolyzed in vitro using a static human digestion model; triglyceride (TG) disappearance was followed by thin-layer chromatography. RESULTS: In mice, after 1 h, plasma TGs tended to be higher in the MPL group than in the SPL group (141 µg/mL vs. 90 µg/mL; P = 0.07) and nonesterified fatty acids (NEFAs) were significantly higher (64 µg/mL vs. 44 µg/mL; P < 0.05). The opposite was observed after 4 h with lower TGs (21 µg/mL vs. 35 µg/mL; P < 0.01) and NEFAs (20 µg/mL vs. 32 µg/mL; P < 0.01) in the MPL group compared with the SPL group. This was associated at 4 h with a lower gene expression of apolipoprotein B (Apob) and Secretion Associated, Ras related GTPase 1 gene homolog B (Sar1b), in the duodenum of MPL mice compared with SPL mice (P < 0.05). In vitro, during the intestinal phase, TGs were hydrolyzed more in the MPL emulsion than in the SPL emulsion (decremental AUCs were 1750%/min vs. 180%/min; P < 0.01). MPLs enhance lipid intestinal hydrolysis and promote more rapid intestinal lipid absorption and sharper kinetics of lipemia. CONCLUSIONS: Postprandial lipemia in mice can be modulated by emulsifying with MPLs compared with SPLs, partly through differences in chylomicron assembly, and TG hydrolysis rate as observed in vitro. MPLs may thereby contribute to the long-term regulation of lipid metabolism.