Cross-reactivity within the profilin panallergen family investigated by comparison of recombinant profilins from pear (Pyr c 4), cherry (Pru av 4) and celery (Api g 4) with birch pollen profilin Bet v 2

Profilin is a panallergen which is recognised by IgE From about 20% of birc h pollen- and plant food-allergic patients. Little is known about epitope d iversity among these homologous proteins, and about the correlation between IeE-cross-reactivity and allergenic reactivity. Plant food profilins from pear (Pyr c 4) and cherry (Pru av 4) were cloned by polymerase chain reacti on and produced in Escherichia coli BL21. The profilins were purified as no n-fusion proteins by affinity chromatography on poly-(L-proline)-Sepharose and characterized by immunoblotting, IgE-inhibition experiments and histami ne release assays. The coding regions of the cDNA of pear and cherry profil in were identified as a 393 bp open reading frame. The deduced amino acid s equences showed high identities with birch pollen profilin Bet v 2 (76-83%) and other allergenic plant profilins. Pyr c 4 and Pru av 4 were investigat ed for their immunological properties in comparison with profilins from cel ery (Api g 4) and birch pollen (Bet v 2). Forty-three of 49 patients (88%), preselected for an IgE-reactivity with Bet v 2 showed specific IgE-antibod ies to the recombinant pear protein, 92% of the sera were positive with the recombinant cherry allergen and 80% of the sera were reactive with the cel ery protein. Inhibition experiments showed a strong cross-reactivity of IgE with profilins from plant food and birch pollen. However, IgE binding prof iles also indicated the presence of epitope differences among related profi lins. All investigated profilins, Pyr c 4, Pru av 4, Api g 4 and Bet v 2, p resented almost identical allergenic properties in cellular mediator releas e tests. Therefore, cross-reactivities between related profilins may explai n pollen-related allergy to food in a minority of patients. The nucleotide sequences reported have been submitted to the Genbank database under access ion numbers AF129424 (Pyr c 4) and AF129425 (Pru av 4). (C) 2001 Elsevier S cience B.V. All rights reserved.