Cloning and Molecular and Immunological Characterisation of Two New Food Allergens, Cap a 2 and Lyc e 1, Profilins from Bell Pepper (Capsicum annuum) and Tomato (Lycopersicon esculentum).

Background: Profilins are recognised by IgE of about 20% of patients allergic to birch pollen and plant foods. They are ubiquitous intracellular proteins highly cross-reactive among plant species. Therefore, they were called panallergens and are made responsible for cross-sensitisation between plant pollen and food. Objectives: The aim of the present study was to clone the cDNAs encoding profilins from bell pepper and tomato, to produce and purify the recombinant proteins and to compare their IgE-binding capacities to those of the natural proteins. Methods: cDNA clones coding for profilin were obtained by RT-PCR from total RNA of tomato and bell pepper fruits, sequenced and expressed as non-fusion proteins in Escherichia coli. The recombinant profilins were subsequently purified and tested for IgE-binding and inhibition capacity with sera from 34 food-allergic patients. Possible oligomerisation of recombinant profilins was investigated by HPLC analysis and its influence on IgE binding assayed by ELISA. Results: The open reading frame from both profilins encompasses 393 bp with a predicted molecular mass of 14, 184 kD and a pl of 4.44 for bell pepper profilin (Capa 2) and 14, 257 kD and a pl of 4.46 for the profilin from tomato (Lyc e 1). The two protein sequences display 91% identity, whereas tomato profilin from pollen shares only 75% identity with tomato fruit profilin. Eleven out of 34 food-allergic patients (32%) display IgE binding to both purified profilins. Preincubation of a serum pool with either purified rCap a 2 or rLyc e 1 nearly abolished IgE binding to natural Cap a 2 and Lyc e 1, respectively. In addition,... [ABSTRACT FROM AUTHOR]