Identification of four novel potato (Solanum tuberosum) allergens belonging to the family of soybean trypsin inhibitors

Background: We have previously identified patatin (Sol t 1) of potato tuber s as a major food allergen among atopic children. In addition to Sol t 1, c oncomitant ISE binding to other, then unidentified, potato proteins was obs erved. Methods: Purification and identification of the putative allergens were don e by both standard and advanced methods of protein chemistry. The patient s eries comprised 39 children with positive skin prick test (SPT) to raw pota to. Immunoblotting and ELISA were used to examine IgE-binding ability and s kin prick testing to assess in vivo reactivity of the purified potato prote ins. Results: Four IgE-binding potato proteins with molecular masses ranging fro m 16 to 20 kDa were purified and identified as cathepsin D-, cysteine-, and aspartic protease inhibitors belonging to the family of soybean trypsin in hibitors (Kunitz type). The proteins were designated Sol t 2, Sol t 3.0101, Sol t 3.0102, and Sol t 4. In ELISA, 51% of the sera of the 39 atopic chil dren showed specific IgE to Sol t 2, 43% to Sol t 3.0101, 58% to Sol t 3.01 02, and 67% to Sol t 4, respectively. All these four allergens were able to produce positive wheal-and-flare responses in SPT. Conclusions: In addition to Sol t 1, potato tubers contain several proteins belonging to the family of soybean trypsin inhibitors against which atopic children with positive SPT responses to raw potato have in vitro and in vi vo reactive IgE antibodies.