Lipid ligand binding and membrane interactions of a novel food-derived lipid transfer protein enhance basophil allergic responses

Abstract Non-specific (ns) lipid transfer proteins (LTPs) are lipid-binding allergens whose natural ligands are not fully known. To elucidate the function and allergenic relevance of nsLTP-lipid complexes, purified natural Lupinus luteus ( L. luteus ) nLTP and recombinant peach LTP, rPru p 3, were tested for membrane interaction and lipid transport activity using liposome assays and Förster-resonance-energy-transfer (FRET) in a case-level proof-of-principle investigation. Allergenic relevance of the LTP-lipid interaction was evaluated in the presence of oleic acid (OA), phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylserine (PS) in a basophil activation test (BAT) with effector cells from an LTP-allergic patient. Both LTPs interacted with neutral PC and negatively charged PS liposomal membranes. A novel transport activity for anionic PG species was identified for both proteins, indicating a shared functional preference for the glycerol headgroup. LTP-dependent lipid exchange/mixing were consistent with transfer. However, fusion/mixing mechanisms cannot be excluded with the current readout. In BAT, both LTPs showed enhanced activation in combination with OA, PC, PG, and PS. As PG is a key component of bacterial membranes, the PG specificity of the lipid interaction of L. luteus nLTP and rPru p 3 is likely of relevance in allergen interaction with the gut microbiome and for enhancement of allergic symptoms. These findings highlight lipid-specific functional properties and lipid-dependent modulation of allergenic activity in plant nsLTPs.