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Study pinpoints novel allergen in celery

By Nathan Gray , 05-Jan-2011
Last updated on 05-Jan-2011 at 17:37 GMT

A highly stable novel allergen that may lead to severe reactions has been identified in celery stalks.

In a study published in Molecular Nutrition & Food Research, researchers identified the novel allergen, known as Api g 2, and tested its allergenic effects; finding that the allergen is highly stable against digestion and heat.

Food allergies are caused by an adverse immune response, usually to a food protein, when the immune system identifies a protein as harmful. Estimates of incidence vary, but in recent years the sector of the food industry catering to allergy-sufferers – the ‘free-from’ market – has developed rapidly.

The most common food allergen ingredients and their derivatives are cereals containing gluten, fish, crustaceans, egg, peanut, soybeans, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.

According to new findings by Dr Gabriele Gadermaier and her co-workers from the University of Salzburg, Austria, allergy to celery may be more complex than previously thought.

“Our data clearly indicate that Api g 2-sensitized patients are at risk to develop adverse reactions upon consumption of cooked celery stalks. The remarkable stability to gastrointestinal proteolysis and thermal treatment makes Api g 2 a possible trigger of severe allergic reactions,” said the researchers. “The integration of Api g 2 in the current allergen panel could enhance the diagnostic sensitivity and specificity,” they said.

Dr Gadermaier and colleagues said that molecule-based identification of allergens using the growing panel of known allergens may help consumers avoid unnecessary diet restrictions and could assist formulators when producing processed products that contain potentially allergenic ingredients.

Diagnosis and formulation

“Based on our results, it can be anticipated that inclusion of recombinant Api g 2 in the current panel of allergens for molecule-based diagnosis will facilitate the evaluation of the clinical relevance of nsLTP sensitization in celery allergy and help clinicians in the management of food allergic patients,” said the researchers.

They added that the concentration of Api g 2 is very low from its natural source, and noted that it remains “unclear how processing as well as the celery food matrix influence allergenicity.”

Severe allergen

The authors said that lipid-transfer proteins are considered the most important food allergens in the Mediterranean area, and is used is in many herbs and spice mixes worldwide.

They noted that currently, 58 allergenic non-specific lipid transfer protein (nsLTPs) have been identified and characterized.

Celery (A. graveolens) ranks among the most important plant food allergen sources in the central European adult population, said Gadermaier and colleagues. They added that allergic reactions to celery and foods containing celery ingredients can have potentially severe consequences from a “broad spectrum of clinical symptoms ranging from mild oral allergy syndromes to life-threatening anaphylactic reactions.”

The authors also highlighted that celery is able to trigger severe reactions in some people, which they said suggests the involvement of highly stable allergens. They noted that so far, three celery allergens have been identified at the molecular level: Api g 1, Api g 4, and Api g 5.

Although research on allergens from celery tuber (celeriac) have been extensively carried out, the authors said that information on the allergenic potential of celery stalks – a vegetable consumed worldwide and an ingredient in several widely consumed spices – is nearly absent.

“In this study, we identified a novel allergen of celery stalks that belongs to the non-specific lipid-transfer protein (nsLTP) family 1 and was designated as Api g 2,” said the researchers.

Study details

“We found that Api g 2 was highly resistant to simulated gastrointestinal digestion and although the primary sequence contains 19 potential pepsin cleavage sites it displayed an enormous stability,” said the authors.

In addition they reported that Api g 2 appeared to be extremely resistant to thermal denaturation – as reflected by a high melting temperature.

The researchers added that detailed physicochemical and immunological characterization of Api g 2 revealed that the recombinant molecule displays similar properties as its natural counterpart.

Source: Molecular Nutrition & Food Research
Published online ahead of print, doi: 10.1002/mnfr.201000443
“Molecular characterization of Api g 2, a novel allergenic member of the lipid-transfer protein 1 family from celery stalks”
Authors: G. Gadermaier, M. Egger, T. Girbl, A. Erler, A. Harrer, E. Vejvar, M. Liso, K. Richter, L. Zuidmeer, A. Mari, F. Ferreira

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