Gastric digestome of whole peanut grains from the aspect of immunoproteomics: Characterization of digested allergens in the real food matrix

Abstract

Objective: Major peanut allergens, Ara h 2 and Ara h 6, are known to be resistant to pepsindigestion, and they sensitize individual via the gastrointestinal tract. Mikenus et al. published astandardized static digestion method for food, based on physiological conditions emphasizing theimpact of food matrices. Immunoreactive proteins (large fragments) and peptides (short digestionresistant peptides SDRPs; <10 kDa), to which the immune system of the gastrointestinal tract isexposed during digestion of peanut proteins, has not been investigated under pure physiologicalconditions suggested by this protocol.Matherial and methods: Whole grain of grounded raw peanut was incubated with human α-amylase, and pepsin, mimicking the effects of oral and gastric digestion, in total duration of 2h.Bottom up proteomic approach, immunoblotting with allergen-specific antibodies from peanut-sensitized patients, enzyme-linked immunosorbent inhibition assay and ImmunoCAP tests, wereused to identify and characterize peanut digesta.Results: After 2h of oral/gastric phase we got, intact proteins, large, digestion resistant peptides(DRP) and SDRPs, as well. Ara h 2 and Ara h 6 remained mostly intact, and short DRPs from Ara h2 and Ara h 6 were more potent in inhibiting IgE binding than Ara h 1 and Ara 3. Ara h 1 and Ara h3 showed preserved allergenic capacity, as well. Almost all of identified short DRPs from Ara h 1,Ara h 2 and Ara h 3, with preserved allergenic potential, were constituents of continuous epitopesequences found via Immune Epitope Database (www.iedb.org).Conclusion: Processes of protein extraction from the matrix and their enzymatic digestion occursimultaneously. Oral and gastric phase digestion products of raw peanut are intact proteins, largeand short digestion resistant peptides. Under these conditions Ara h 2 and Ara h 6 are expectedly