A newly identified allergen in the celery root could be the previously unexplained link between celeriac allergy and mugwort pollen sensitisation.
Celery root (Apium graveolens) allergy is one of the most common food allergies in Northern Europe. Six celery allergens (Api g 1 to Api g 6) were previously known. They are a very diverse set of proteins, such as defence proteins or profilin, a small protein with regulatory properties.
A celeriac allergy is often associated with a respiratory allergy to mugwort pollen (Artemisia vulgaris), which could not previously be explained by the presence of a cross-allergy to known homologous allergens in celery root pollen. A cross-allergy is based on a phenomenon known as IgE cross-reactivity. This allergy occurs when immunoglobulin E antibodies (IgE), which react to a specific allergen from a single source, also recognise allergens from another source and lead to allergic reactions.
Researchers at the Paul-Ehrlich-Institut, together with international colleagues, investigated the possible presence of a defensin-related allergen in celeriac allergies and what role that allergen might play. Defensins are small polypeptides found in all animal organisms and higher forms of plant life to defend against microbial pathogens.
The researchers tested the binding capacity and allergenicity of celeriac defensin, known as Api g 7, using serum samples from eight celeriac allergy sufferers and an appropriate number of control subjects. Further tests conducted by the research team included an analysis of the allergen activity of the recombinant Api g 7. During those tests, it was found that celeriac with Api g 7 contains an IgE-reactive defensin, which demonstrated cross-reactivity with the main allergen from mugwort pollen. The presence of this defensin could most likely explain the known association between celeriac allergy and mugwort pollen sensitisation.
The newly identified celery allergen Api g 7 may help improve the sensitivity of in vitro diagnostic tests.
Prof Dr Stefan Vieths (Vice President of the Paul-Ehrlich-Institut)
Wangorsch A, Lidholm J, Mattsson LA, Larsson H, Reuter A, Gubesch M, Gadermaier G, Bures P, Scheurer S, Ballmer-Weber B, Vieths S (2022): Identification of a defensin as novel allergen in celery root: Api g 7 as a missing link in the diagnosis of celery allergy?.
Allergy 77: 1294-1296.