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Effects of heat treatment and proteolytic enzymes on allergenicity

Explore how heat treatment and proteolytic enzymes affect the allergenicity of food, with implications on sensitization and immune responses. Case studies on cherry, peanut, and melon allergens shed light on the complex interplay between processing and allergenic potential.

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Effects of heat treatment and proteolytic enzymes on allergenicity

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  1. Effects of heat treatment and proteolytic enzymes on allergenicity Dr. Montserrat Fernández Rivas The GA2LEN/EAACI Allergy School

  2. Food allergens • In contrast to inhalant allergens (most) food allergens undergo considerable changes in structure and may form complex structures with other food components before they interact with the individual’s immune system. • Food processing and digestion modify the allergenicityof foods, in terms of potential to sensitise and/or induce symptoms. • Therefore it is of paramount importance to understand the molecular basis of the effects of food processing and digestion (and we have just begun). • Furthermore, the role of the food matrix in which an allergen is processed must also be evaluated. • Epitopes: • Linear or sequential: binding is not afected by the folding state of the protein • Conformational: binding is disrupted by changes in the protein folding.

  3. Effects of heat treatment • Thermolabile proteins: unfolding conformational epitopes • Bet v 1 homologues • Albumins • Thermostable proteins: • Limited unfolding and aggregation: 11S, 7S globulins • Resisting unfolding and refolding on cooling: 2S albumins, nsLTP, parvalbumin • Covalent modification of proteins: Maillard reactions • Bet v 1 homologues • Peanut allergens, Ara h 1 and 2 • nsLTP

  4. Thermolabile proteins: Bet v 1 homologues • Birch pollen-fruit-vegetable syndrome • Clinical finding: patients react to the fresh fruit but tolerate it cooked. • Patients sensitised to intact native Bet v 1 through the inhalant route recognise conformational epitopes on plant foods that are destroyed during cooking (unfolding) • Api g 1 and Gly m 4 are more thermostable than their equivalents in Rosaceae fruits: this is in line with reactions induced by cooked celery and soya-based food supplements

  5. Thermolabile proteins: Bet v 1 homologues • Fresh sweet cherries from the market • cherry fruit juice, 35% fruit content • preserved cherries, sweetened • cherry jam, 45% fruit content CD spectra of Pru av 1 at different temperatures Scheurer et al. JACI 2004; 114: 900-7

  6. Thermostable proteins: nsLTP • Clinical findings: • Patients allergic to peach/apple LTP react • with the fresh fruit and with processed products • (+) OFC with cooked apple • Patients allergic to hazelnut-Cor a 8 react after • ingestion of roasted hazelnuts • Patients allergic to maize LTP react with cooked • maize derivatives (polenta, roasted corn, popcorn) 1) fresh sweet cherries from the market 2) cherry fruit juice, 35% fruit content 3) preserved cherries, sweetened 4) cherry jam, 45% fruit content Scheurer et al. JACI 2004; 114: 900-7 CD spectra of Pru av 3 at different temperatures

  7. Maillard reactions and nsLTP Effect of heat treatment +/- glucose on Mal d 3 IgE binding potency SPT Mal d 3 heated 60 min 100ºC: no change 20 min 90oC 2 hr 100oC (+) (-) 2 hr 100oC Protection of Mal d 3 by the presence of glucose during heating Sancho AI. Allergy 2005;60:1262-8 The Maillard reaction is achemical reaction between an amino acid and a reducing sugar, usually requiring heat.

  8. Maillard reactions and peanut allergenicity Roasting peanuts: increased IgE-binding x90 Maleki SJ. JACI 2000;106:763-8

  9. Maillard reactions and peanut allergenicity Roasting peanuts: increased IgE-binding + stability to digestion Maleki SJ. JACI 2000;106:763-8 Ara h 2 trypsin inhibitor activity is 3.6 fold increased by roasting and protects Ara h 1 against trypsin digestion. Maleki SJ. JACI 2003; 112:190-5

  10. Effect of proteolytic enzymes on Bet v 1 homologues • Cherry extract digested with pepsin: • (A) Silver stained • (B) IgE immunoblot • 2 hr without pepsin • 30 sec • 1 min • 15 min • 30 min • 1 hour • 2 hours • BSA without pepsin • BSA 2 hours Scheurer et al. JACI 2004; 114: 900-7

  11. Pepsin digestion of purified cherry allergens Bet v 1 homologue nsLTP Profilin Scheurer S. JACI 2004; 114: 900-7

  12. Stability of profilin Melon profilin is completely digested in < 1 min Melon profilin is not affected After heating 100ºC 15 min López-Torrejón G. CEA 2005; 35:1065-72.

  13. Stability of profilin López-Torrejón G. CEA 2005; 35:1065-72.

  14. In summary • There are no clear rules regarding how different allergens respond to heat treatment and proteolytic enzymes, with some as the Bet v 1 homologues having their allergenicity destroyed, whereas for many others it is unaltered. • On the other hand, the allergenicity of some foods may even increase following food processing.

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