Molecular characterization of Api g 2, a novel allergenic member of the lipid-transfer protein 1 family from celery stalks

Celery represents a relevant cross-reactive food allergen source in the adult population. As the currently known allergens are not typical elicitors of severe symptoms, we aimed to identify and characterize a non-specific lipid transfer protein (nsLTP). MS and cDNA cloning were applied to obtain the full-length sequence of a novel allergenic nsLTP from celery stalks. The purified natural molecule consisted of a single isoallergen designated as Api g 2.0101, which was recombinantly produced in Escherichia coli Rosetta-gami. The natural and recombinant molecules displayed equivalent physicochemical and immunological properties. Circular dichroism revealed a typical α-helical fold and high thermal stability. Moreover, Api g 2 was highly resistant to simulated gastrointestinal digestion. As assessed by ELISA, thermal denaturation did not affect the IgE binding of Api g 2. Natural and recombinant Api g 2 showed similar allergenic activity in mediator release assays. Api g 2-specific IgE antibodies cross-reacted with peach and mugwort pollen nsLTPs. 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