Measurement of lipid transfer protein in 88 apple cultivars

Background: Fruits are a major cause of food allergy in adults. Lipid transfer proteins (LTP) are implicated in severe allergic reactions to fruits, but little is known about LTP content in different cultivars. Objective: Determination of the levels of LTP in a wide range of apple cultivars. Methods: LTP was measured in apples from 53 cultivars grown in Italy and 35 grown in The Netherlands, using three different immunoassays: a competitive ELISA (cELISA), a sandwich ELISA (sELISA) and a RAST inhibition (RI). Selected cultivars were evaluated using the basophil histamine release test (BHR), skin prick test (SPT) and double-blind, placebo-controlled food challenge (DBPCFC). Results: LTP levels measured with the three immunoassays were significantly correlated, as judged by Pearson's correlation (0.61 <Rp <0.65; p <0.0001), but differed with respect to the actual quantities: 3.4-253.2 (sELISA), 2.7-120.2 (cELISA) and 0.4-47.3 µg/g tissue (RI). Between cultivars, LTP titers varied over about a two-log range. Pilot in vitro and in vivo biological testing (BHR, SPT and DBPCFC) with selected cultivars supported the observed differences in LTP levels. Conclusions: Around 100-fold differences in LTP levels exist between apple cultivars. Whether the lowest observed levels of LTP warrant designation as hypo-allergenic requires more extensive confirmation by oral challenges. Determination of cultivar variation in LTP levels provides important information for growers and consumers. Comparison to earlier reported Mal d 1 levels in the same cultivars reveals that a designation as low allergenic does not always coincide for both allergens.