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Effects of heat treatment and proteolytic enzymes on allergenicity

Effects of heat treatment and proteolytic enzymes on allergenicity. Dr. Montserrat Fernández Rivas. Food allergens.

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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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