Comparison of Physiological and in vitroPorcine Gastric Fluid Digestion

Abstract

Background: In previous studies, the major peanut allergen Ara h 1 was digested in vitro using pepsin and porcine gastric fluid. The results suggested that in vivo gastric digestion of allergen protein can be modeled accurately by peptic hydrolysis in vitro. In the current investigation, studies were designed to follow the gastrointestinal (GI) digestion of peanut allergens under true physiological conditions. In vitro digestion with porcine gastric fluid was compared with actual physiological digestion of peanut allergens in the porcine digestive tract in vivo. Methods: Analysis of physiologic digestion was performed in piglets administered a 20-gram bolus of peanut meal followed by periodic sampling and analysis of GI contents. The pH was monitored, and digesta were analyzed by SDS-PAGE and immunoblot analysis. Results: Peanut meal initially neutralized stomach contents to a pH of approximately 7, which was subsequently acidified by HCl secretion within 30 min. Acidification to pH 2–4 resulted in active pepsin digestion of soluble protein in the stomach. Soluble intact protein/allergens were rapidly degraded to pepsin-resistant peptides in the stomach followed by hydrolysis of these fragments in the small intestine. Particulate material was evident in both the stomach and small intestine that could contribute to continued release of peanut allergens Ara h 1, 2 and 3. Conclusions: Porcine gastric digestion of peanut proteins resembles true physiological digestion only under optimal physiologic conditions. Soluble proteins are rapidly digested and insoluble material continues to release IgE-reactive proteins throughout the GI tract. GI digestion of food allergens can play a prominent role when assessing allergens within the context of a food matrix or meal and during the sensitization phase of IgE-mediated allergy.

Adsorption of Peanut (Arachis hypogaea, Leguminosae) Proteins by Activated Charcoal

“…Effect of pH on Protein Binding to AC. To determine whether peanut protein adsorption onto AC is affected by pH, proteinbinding experiments were conducted at two physiologically relevant pH values: pH 7 (oral and intestinal pH) and pH 2 (gastric pH) (14). CPE was adjusted to the appropriate pH with HCl and incubated with increasing amounts of AC in separate microcentrifuge tubes at 37 °C for 2 min.…”

“…The presence of peanut allergens in the insoluble roasted peanut material provides a continuous source of major allergens to the gastrointestinal mucosal immune system. A related study (14) showed that insoluble particulate material, present in both the stomach and small intestine, continuously released IgE-reactive peanut allergens as a peanut meal passed through the gastrointestinal tract. This extended release could provide a prolonged source of allergen and be largely responsible for the biphasic anaphylactic reactions observed in some patients.…”

Digestion of peanut allergens Ara h 1, Ara h 2, Ara h 3, and Ara h 6: A comparative in vitro study and partial characterization of digestion‐resistant peptides

“…Interestingly, digestion of a peanut extract with pepsin did not affect the IgE‐binding properties, although substantial proteolytic breakdown was observed 32. Digestion of peanut extracts consisting of various allergens and nonallergens results in a pool of peptides that is difficult to interpret 33. Purified allergens can be used to circumvent this.…”

Birch Pollen-Related Food Allergy: An Excellent Disease Model to Understand the Relevance of Immunological Cross-Reactivity for Allergy

“…We observed that the pH value in the stomach of rats rises to 5 after allergen administration. Similarly, administration of a peanut-based meal initially neutralized the gastric pH value of piglets to approximately 7, which was subsequently acidified by HCl secretion (Kopper et al, 2006). The high pH value renders pepsin inactive.…”