Characterization and Identification of Potential Allergenic Proteins in Sophora japonica L. Pollen

Sophora japonica L. pollen (SJP) is an emerging cause of urban seasonal allergies such as asthma and rhinitis. This study systematically evaluated the allergenicity of SJP using both in vivo and in vitro experiments. In vivo, a mouse model was employed in which SJP induced typical allergic symptoms, including sneezing and rubbing behavior, elevated serum IgE and IL-4 levels, and reduced IFN-γ levels. In vitro, IgE immunoblotting and ELISA using sera from allergic patients identified five potential allergenic protein bands separated by SDS-PAGE. LC-MS analysis further revealed a novel potential allergen, a 35 kDa protein belonging to the cytochrome f family, designated as Sop j 1. Structural comparison by CD spectroscopy and AlphaFold, combined with matching molecular weight and IgE reactivity profiles, confirmed that this cytochrome f protein is indeed Sop j 1. Recombinant Sop j 1 was produced and structurally validated. Western blot and inhibition ELISA demonstrated its specific binding to IgE in patient sera and its ability to inhibit IgE binding to native SJP. These findings indicate that Sop j 1 is a key allergenic protein in SJP with high IgE sensitization rates in the studied population, which will facilitate the development of precise diagnostics and treatments.