The ligand of the major allergen protein from peach is the main player in the induction of allergic sensitization

While evidence accumulated in recent years pointed to a key role played by molecules transported by allergen proteins in the sensitization phase of allergy, no direct results demonstrating that role were available. Peach allergy is the most prevalent plant food allergy in Mediterranean countries and Pru p 3, the major peach allergen, is a model protein in food allergy research. The long-sought ligand of this lipid transfer protein was recently identified by our CBGP group as a molecule consisting of a derivative of the alkaloid camptothecin and a lipidic phytosphingosine tail. The characterization of this ligand allowed us to provide invaluable information on the physiological function of Pru p 3 in plant (Cubells-Baeza et al., Plant. Mol. Biol. 2017; 94:33-44, doi: 10.1007/s11103-017-0590-z).

The CBGP group “Molecular basis of allergenicity and cross-reactivity in plant food”, in collaboration with researchers from the Icahn School of Medicine at Mount Sinai (New York, USA), the Swiss Institute of Allergy and Asthma (Zurich, Switzerland), and the Institute of Applied Molecular Medicine (CEU San Pablo University, Madrid) has found direct evidence on the immunological activity of the ligand of Pru p 3 in the triggering of antigen-presenting cells. Our results revealed that this activity is mediated by CD1d receptors and that the ligand, presented by CD1d, is able to interact with invariant natural killer T (iNKT) cells. Pru p 3 protein would thus to be targeted by innate immune response because of its auto-adjuvant lipidic ligand. Moreover, striking structural similarities between Pru p 3 and saposins (small proteins that assist in trafficking and loading of lipids onto CD1 receptors), support the involvement of peach allergen protein in the immunological processes triggered by these receptors.