Hanne Frøkiær - powerpoint presentation

Food Proteins: Allergens Hanne Frøkjær Department of Systems Biology

DTU

What is an allergen? ’A substance which provokes an allergic reaction in individuals sensitive to the substance’

Hanne Frøkiær

What is Allergy? ’Hypersensitivity’ ’Inappropriate immune responses against normally harmless antigens’

Hanne Frøkiær

What is an allergic reaction? An inappropriate immunological reaction against a usually harmless substance. -characterized by production of specific antibodies (IgE), and release of histamine and other bioactive substances. Hanne Frøkiær

Hanne Frøkiær

Food allergies and related symptoms

Most common food allergens Hanne Frøkiær

•Milk •Eggs •Peanuts (and other legumes) •Tree nuts (cashew, walnut) •Shellfish •Fish •Grain (wheat, rice)

Allergens: Properties of most food allergens
Heat stability
Resistance towards acid
Resistance towards proteolysis
Glycoproteins
Mw 10 kDa or more Hanne Frøkiær

Allergy: Endogeneous factors affecting sensitation
Genetic influence
Underlying disease
Diet
Commensal flora
Age
Gender Hanne Frøkiær

Hanne Frøkiær

Initiation of an allergic reaction Second and later encounter with the allergen

Mast cells Cross-linking of Fcε Receptors leads to degranulation Hanne Frøkiær

Kinetics of major biochemical events after IgE receptor cross linking in mast cells

Hanne Frøkiær

Hanne Frøkiær

Initiation of an allergic reaction Second and later encounter with the allergen

Allergy: Exogenous factors affecting sensitation


Exposure  Magnitude  Frequency  Route


Atmospheric pollution  Tobacco smoke  Geographical factors


Metals
Detergents Hanne Frøkiær

Prevalence of food allergy depends on the clima and agricultural tradition

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Allergic symptoms to food

Worst case: anaphylactic shock

How much is to much? much? Minimum dose of peanut protein that elicited an allergic reaction: 1-5 mg protein (DBPCFC) 100 µg protein (single case)

Hanne Frøkiær

Hanne Frøkiær

What is the problem? 1.How to avoid allergic reactions in sensitised individuals 2.Novel food

Hanne Frøkiær

How to avoid allergic reactions in sensitised individuals 1. Residual reactive allergens in processed food 2. Contamination from the processing plant 3. Cross-reactivity to other plant proteins

Hanne Frøkiær

Allergens in processed food: food:
Plant oils
polysaccharides, (plants, shellfish)
Emulsions
Extensively heated products
Hydrolysed products

Hanne Frøkiær

Allergen Example: Example: Ara hII Major allergen in peanuts
Protease resistant
Heat resistant
Digested allergen can still react

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Lehmann et al. 2006

Allergen Example : Ara hII Major allergen in peanuts
Protease resistant
Heat resistant
Digested allergen can still react

Hanne Frøkiær

Lehmann et al. 2006

How to avoid allergic reactions in sensitised individuals 1. Residual reactive allergens in processed food 2. Contamination from the processing plant 3. Cross-reactivity to other plant proteins

Hanne Frøkiær

How to avoid allergic reactions in sensitised individuals 1. Residual reactive allergens in processed food 2. Contamination from the processing plant 3. Cross-reactivity to other plant proteins

Hanne Frøkiær

Prerequisites for cross allergenicity of two proteins: More than one epitope in common

Hanne Frøkiær

Common foods provoking food allergy Food

Cross reacting foods

Cows' milk

Mares' milk, goats' milk, ewes' milk

Hens' eggs

Eggs from other birds

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Cod

Mackerel, herring, plaice, etc

Shrimps

Other crustaceans

Peanuts

Soy beans, green beans, green peas, lupin

Soy beans

Wheat Additives

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Cross reactivity of allergens

See above Other grains, most often rye Mostly unknown (both synthetic and naturally occurring)

How to handling the problems?

Hanne Frøkiær

1. Labeling 2. Risk assessment of novel foods 3. Improved knowledge on relevant cross-reacting proteins 4. Improved knowledge on factors increasing the prevalence of allergy