Molecular allergology: How research on food allergens improves diagnosis and therapy of allergies
“May contain traces of peanuts” – Declarations on food packaging like these belong to our everyday life. This is an improvement, because allergens from many food products can trigger life-threatening symptoms in patients. A review article by Prof. Dr. Uta Jappe (Research Center Borstel and University of Lübeck, DZL Site ARCN) and Prof. Dr. Annette Kuehn (Luxembourg Institute of Health) has been published in the September edition of the German journal Allergologie. It describes the state of knowledge on allergens that are taken up as a part of nutrition.
Not just the usual suspects can trigger food allergies. The range of plant allergens that trigger severe symptoms goes from tree nuts to legumes as peanut, soy bean and lupin to cereals as wheat and fruit as banana, kiwi and apple. The main animal sources of allergens are milk, chicken egg, meat, fish and sea fruit.
Typical symptoms are vomiting, diarrhea and colic. In severe cases a systemic anaphylactic shock can occur. As pollen allergens, food allergen can also induce respiratory complications, e.g. swelling of the oral mucosa or asthma attacks. Sometimes just the opening of a packet of peanut snacks is sufficient for that. Some of these food allergens can also trigger asthma in an occupational context – as in ‘baker’s asthma’.
Molecular allergology, which is in the center of the recently published article, aims for the identification and isolation of the actual substances from food that trigger symptoms. This is more than just an academic concern: Actually, knowledge of the structure of a protein allergen can lead to conclusions about allergens in other food products. For example, this is true for the Bet v 1 allergen from birch pollen that is similar to proteins from fruit or vegetables. Allergists can raise patient’s awareness for these “cross-reactivities” – as between birch and apple – and test them for sensitization. In this field, molecular allergology offers a range of tools to complement and improve diagnostics. As a consequence, not just extracts from allergen sources (e.g. peanuts) can be used for skin testing for allergies, but the triggering molecule itself. Thus, the allergist gets more detailed information on the kind of allergy, because extracts have the disadvantage to be a mixture of many potential allergens of which just one might be relevant for a certain patient. Moreover, extracts hold the problem that some molecules are not contained in test solutions in a sufficient amount. Using the single allergen, these problems of extracts can be circumvented. Blood testing for allergen specific IgE antibodies strictly requires knowledge and availability of single allergens.
Also therapy benefits from the new findings: Custom-fit immunotherapies have been developed and applied by allergists in order to desensitize and heal patients. Moreover, they can provide their patients with much better directives concerning the uptake of specific foods. “But there’s a lot to do”, says Prof. Dr. Uta Jappe when looking at allergy warnings for allergens on food packing. “The difficult thing about ‘traces’ is that this word is by far too inaccurate. It has to be declared much more exactly which amount of allergen is really in a food product in order to give patients an indication, if she or he will get an allergic shock – or if it can be eaten without problems.” Moreover, the declaration of further allergens is a point where action by companies and politics is urgently needed.
Further information: Jappe U, Kuehn A, Neues zu diagnostisch relevanten Einzelallergenen aus pflanzlichen und tierischen Nahrungsmittelquellen (2016) Allergologie 38: 425-438. [in German]