Allergenicity and cross‐reactivity of Senecio pollen: identification of novel allergens using the immunoproteomics approach

Summary Background The genus Senecio is the largest genus of the family Asteraceae (Compositae). The allergenicity of Senecio has not been assessed previously. Objective The aim of this study was to investigate the allergens of Senecio jacobea pollen and to determine their immunological characteristics and clinical relevance. Methods Fifty patients with rhinoconjunctivitis and a positive skin prick test (SPT) to Senecio were recruited. The clinical relevance of this pollen was assessed by means of a nasal provocation test (NPT). Allergens were characterized by one-dimensional electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis and immunoblotting. Furthermore, characterization and identification of the allergens were performed by mass spectrometry (MS). In vitro inhibition tests were performed to evaluate cross-reactivity with other pollen. Results Three predominant allergens, both in the intensity of reaction and the frequency of recognition by human-allergic sera, were 59 (60%), 42 (50%) and 31 kDa (50%). The two-dimensional analysis allowed the identification of several allergens. One spot around 42 kDa was identified as a protein homologous to pectate lyase and three other spots were homologous to malate dehydrogenase by MS. S. jacobea proteins showed cross-reactivity with other proteins of the Asteraceae family and also with Parietaria judaica. This was demonstrated by immunoblotting and ELISA inhibition studies. Conclusion S. jacobea constitute a newly discovered allergenic source. It shows cross-reactivity with other members of the Asteraceae plant family as well as with P. judaica.