Identification, cloning, and immunological studies on a major eggplant (Solanum melongena L.) allergen Sola m 1: A new member of profilin allergen family

Abstract

Eggplant or brinjal (Solanum melongena L.) is widely consumed worldwide and thought to trigger allergic reactions in sensitive individuals. So far, no molecular information is available on the allergy-eliciting components of eggplant. In this study, a 17 kDa profilin, Sola m 1, was identified from eggplant by employing an immunoproteomic approach. Based on MALDI-TOF/TOF derived sequences, the full-length cDNA of Sola m 1 was PCR amplified and then cloned. Recombinant (r) Sola m 1 was expressed in E. coli and then purified by metal affinity and gel filtration. rSola m 1 reacted with IgE-antibodies in the sera from all eggplant allergic patients. rSola m 1 also displayed allergenic activity by stimulating histamine release. rSola m 1 was monomeric, and the CD spectra revealed it to be folded with a mixture of α-helices and β-strands. In the melting curve, rSola m 1 exhibited an irreversible denaturation where no refolding took place. Sola m 1 was found to share >80 % sequence identity with Bet v 2, which was further validated by confirming the presence of significant cross-reactivity with Bet v 2 in IgE-inhibition assay. IgE-cross reactivity was also observed between rSola m 1 and profilins from six other foods. In SGF assay, no rSola m 1-derived fragments exhibited IgE-reactivity after prolonged digestion suggesting the association of rSola m 1 with the oral allergy syndromes. Immunofluorescence localization revealed a high abundance of Sola m 1 allergen in eggplant seeds as compared to other edible parts. Taken together, Sola m 1 is the first major eggplant allergen reported in this study, which has the potential of being used as a candidate antigen in component-resolved diagnosis and immunotherapy.

Keywords: (Solanum melongena L.); Allergen; Cross-reactivity; Eggplant; Food allergy; IgE; Profilin; Sola m 1.