Identification of immunoreactive protein bands in Goji berries superfood by proteomic analysis

Background Goji berries belonging to the Solanaceae family were considered officinal plants because of their health benefits. More recently this fruit has been qualified as superfood for the high nutritional value, low fats and high antioxidant content, therefore its inclusion in the diet is highly recommended. Despite their health-promoting properties, Goji berries represent a threat for allergic consumers. Allergenicity of Goji berries has not been thoroughly studied due to the paucity of investigations performed and the little information available about allergenic proteins. It was reported that nearly 77% of individuals allergic to plant foods reacted towards Goji berries and two bands were recognized by most of allergic individuals putatively attributed to LTPs. Method We report a case of two female patients (mean age 50 ys old) that displayed a severe anaphylactic reaction after ingestion of Goji berries. Conventional in vitro test resulted negative. Prick to prick with fresh Goji berries resulted positive. In order to have more insights in the reactive Goji proteins, we performed a proteomic investigation aiming at identifying the proteins reacting towards allergic patients' sera. Goji berries were homogenized, extracted by adding TrisHCl/NaCl buffer enriched with Urea then purified by size exclusion chromatography and loaded onto SDS-PAGE for electrophorethic separation. Several proteins banding above 100 kDa, in the region of 50-30 kDa and below 25 kDa were displayed long the electrophoretic profile. In order to identify the immunoreactive proteins, immunoblot experiments were accomplished by using allergic sera. Each individual band was excised from the gel, in vitro digested and analyzed by LC-MS/MS followed by software-based protein identification. Online databases (Eudycotiledons and Viridiplantae) were interrogated for searching any match with Goji berries protein sequences (Lycium barbarum). Results Fibrillin proteins and proteins belonging to vicilin family were identified in the reactive bands comprised in the range 30-50Kda, whereas the band (below 25kDa) showing the highest reactivity was attributed to glutelin and legumin proteins. Conclusion These preliminary results could be a useful starting point for future investigation to deepen the knowledge on Goji allergenic proteins and its likely cross reactivity with other proteins of plant-related species.