Recombinant allergens Pro av 1 and Pru av 4 and a newly identified lipid transfer protein in the in vitro diagnosis of cherry allergy

Background: In central and northern Europe food allergy to fruits of the Ro saceae family is strongly associated with birch pollinosis because of the e xistence of IgE cross-reactive homologous allergens in birch pollen and foo d. By contrast, in the Mediterranean population allergic reactions to these fruits frequently are not related to birch pollen allergy and are predomin antly elicited by lipid transfer proteins (LTPs), Objective: We sought to determine the prevalence of IgE sensitization to th e recombinant cherry allergens Pru av 1 and Pru av 4 in comparison with che rry extract within a representative group of patients who were allergic to cherries recruited in Germany and to compare the relevance of IgE to cherry LTPs in Italian patients. Methods: Recombinant Pru av 1 and rPru av 4 were available from earlier stu dies. The cDNA of the cherry LTPs was obtained by using a PCR-cloning strat egy. The protein was expressed in Escherichia coli and purified by means of metal chelate affinity chromatography. Sera from 101 German patients with birch pollinosis and oral allergy syndrome to cherry and sera from 7 Italia n patients with cherry allergy were investigated by using enzyme allergosor bent tests for IgE reactivity with cherry extract, rPru av 1, rPru av 4, an d the recombinant cherry LTP. Inhibition experiments were performed to comp are the IgE reactivity of natural and recombinant cherry LTPs and to invest igate potential cross-reactivity with birch pollen allergens, Results: The LTP from cherry comprises 91 amino acids and a 26 amino acid s ignal peptide, The mature cherry LTP shows high amino acid sequence identit y with allergenic LTPs from peach (Pru p 3, 88%), apricot (Pru ar 3, 86%), and maize (Zea m 14, 59%) and displays no IgE cross-reactivity with birch p ollen. The IgE prevalences in the German patients were as follows: LTP, 3 o f 101 (3%); rPru av 1, 97 of 101 (96.0%); rPru av 4, 16 of 101 (16.2%); and cherry extract, 98 of 101 (97%), All 7 Italian patients had IgE against th e cherry LTP. Conclusions: Recombinant allergens are useful tools for a more accurate in vitro IgE-based diagnosis of cherry allergy, Taken together, they mimic the allergenic activity of cherry extract, having slightly higher biologic act ivity. Sensitization to the cherry LTP is relevant for a minority of patien ts recruited in Germany, but our data indicate that it may be a major aller gen in Italy.