In Vitro Digestion and Characterization of 2S Albumin and Digestion-Resistant Peptides in Pecan

The 2S albumins are one of the major protein families involved in severe food allergic reactions to nuts, seeds, and legumes, thus potentially making these proteins clinically relevant for allergic sensitization and potential diagnostic markers. In this study, we sought to purify native 2S albumin protein from pecan to further characterize this putative allergen. The purified 2S albumin, Car i 1, from pecan was found to be resistant to digestion by pepsin in simulated gastric fluid (SGF) and comparatively stable to proteolysis by trypsin and pancreatin in simulated intestinal fluid (SIF). Digestion of purified Car i 1 in SGF and SIF resulted in formation of different digestion-resistant peptides that were capable of binding IgE antibodies from allergic individuals. Digestion stability of Car i 1 and formation of digestion-resistant antigenic peptides may explain why it is a potent sensitizing protein in pecan for susceptible individuals. The observation that digestion-resistant peptides are able to bind IgE implies that pecan can trigger systemic allergic reactions even after digestion in the stomach and small intestine

Assessment of allelic diversity in intron-containing Mal d 1 genes and their association to apple allergenicity

<p>Abstract</p> <p>Background</p> <p>Mal d 1 is a major apple allergen causing food allergic symptoms of the oral allergy syndrome (OAS) in birch-pollen sensitised patients. The <it>Mal d 1 </it>gene family is known to have at least 7 intron-containing and 11 intronless members that have been mapped in clusters on three linkage groups. In this study, the allelic diversity of the seven intron-containing <it>Mal d 1 </it>genes was assessed among a set of apple cultivars by sequencing or indirectly through pedigree genotyping. Protein variant constitutions were subsequently compared with <b>S</b>kin <b>P</b>rick <b>T</b>est (SPT) responses to study the association of deduced protein variants with allergenicity in a set of 14 cultivars.</p> <p>Results</p> <p>From the seven intron-containing <it>Mal d 1 </it>genes investigated, <it>Mal d 1.01 </it>and <it>Mal d 1.02 </it>were highly conserved, as nine out of ten cultivars coded for the same protein variant, while only one cultivar coded for a second variant. <it>Mal d 1.04</it>, <it>Mal d 1.05 </it>and <it>Mal d 1.06 A, B </it>and <it>C </it>were more variable, coding for three to six different protein variants. Comparison of <it>Mal d 1 </it>allelic composition between the high-allergenic cultivar Golden Delicious and the low-allergenic cultivars Santana and Priscilla, which are linked in pedigree, showed an association between the protein variants coded by the <it>Mal d 1.04 </it>and <it>-1.06A </it>genes (both located on linkage group 16) with allergenicity. This association was confirmed in 10 other cultivars. In addition, <it>Mal d 1.06A </it>allele dosage effects associated with the degree of allergenicity based on prick to prick testing. Conversely, no associations were observed for the protein variants coded by the <it>Mal d 1.01 </it>(on linkage group 13), -<it>1.02</it>, -<it>1.06B, -1.06C </it>genes (all on linkage group 16), nor by the <it>Mal d 1.05 </it>gene (on linkage group 6).</p> <p>Conclusion</p> <p>Protein variant compositions of Mal d 1.04 and -1.06A and, in case of <it>Mal d 1.06A</it>, allele doses are associated with the differences in allergenicity among fourteen apple cultivars. This information indicates the involvement of qualitative as well as quantitative factors in allergenicity and warrants further research in the relative importance of quantitative and qualitative aspects of <it>Mal d 1 </it>gene expression on allergenicity. Results from this study have implications for medical diagnostics, immunotherapy, clinical research and breeding schemes for new hypo-allergenic cultivars.</p

Thresholds of allergenic proteins in foods

Threshold doses or Estimated Eliciting Doses (EEDs) represent an important new field of research in food allergy. Clinicians and regulators have embraced some toxicological concepts such as LOAEL and NOAEL and applied them to an area of significant clinical uncertainty and interest. The impact of intrinsic human factors (e.g., asthma and exercise) and extrinsic event factors (e.g., season, location and especially dose of allergen) on a future allergic reaction in the community needs to be considered carefully when interpreting results of clinical and research low-dose food challenges. The ongoing cooperation of food allergy research groups in medicine, food science and government will surely deliver results of the highest importance to the wider communities of allergology, food science and technology and the increasing number of allergic consumers

In vitro digestion and characterisation of 2S albumin and digestion-resistant peptides in pecan

The 2S albumins are one of the major protein families involved in severe food allergic reactions to nuts, seeds and legumes, thus potentially making these proteins clinically relevant for allergic sensitisation and potential diagnostic markers. In this study, we sought to purify native 2S albumin protein from pecan to further characterise this putative allergen. The purified 2S albumin, Car i 1, from pecan was found to be resistant to digestion by pepsin in simulated gastric fluid (SGF) and comparatively stable to proteolysis by trypsin and pancreatin in simulated intestinal fluid (SIF). Digestion of purified Car i 1 in SGF and SIF resulted in formation of different digestion-resistant peptides that were capable of binding IgE antibodies from allergic individuals. Digestion stability of Car i 1 and formation of digestion-resistant antigenic peptides may explain why it is a potent sensitising protein in pecan for susceptible individuals. The observation that digestion-resistant peptides are able to bind IgE implies that pecan can trigger systemic allergic reactions even after digestion in the stomach and small intestine

High fat food increases gastric residence and thus thresholds for objective symptoms in allergic patients

SCOPE: We have tested the hypothesis that high fat foods such as chocolate induce reduced rates of gastric emptying in comparison to lower fat foods and that this can impact uptake of allergens and subsequent reactions in allergic patients. METHODS AND RESULTS: In four volunteers, magnetic resonance imaging was used to measure gastric emptying of a series of nine doses of either dark chocolate bars containing 35% fat or a chocolate dessert containing 8% fat. Analysis showed a mean rate of decrease in gastric volume with an 8% fat dessert was 0.33 ± 0.09 mL/min compared to an average rate of increase in gastric volume of 0.09 ± 0.10 mL/min for the chocolate bars. In parallel, eight allergic patients were challenged for either peanut or hazelnut in the same two matrices and doses using a standardized protocol. A statistical analysis of the objective symptoms in the allergic patients showed that the chocolate bars gave a significantly higher threshold for objective symptoms than the dessert. CONCLUSIONS: Chocolate bars induced lower gastric emptying rates and in food challenges with allergic patients gave a higher threshold of elicitation for objective reactions than a dessert