Pyr c 1, the major allergen from pear (Pyrus communis), is a new member ofthe Bet v 1 allergen family

Pear is known as an allergenic food involved in the 'oral allergy syndrome' which affects a high percentage of patients allergic to birch pollen. The aim of this study was to clone the major allergen of this fruit, to express it as bacterial recombinant protein and to study its allergenic properties in relation to homologous proteins and natural allergen extracts. The codi ng region of the cDNA was obtained by a PCR strategy, cloned, and the aller gen was expressed as His-Tag fusion protein. The fusion peptide was removed by treatment with cyanogen bromide. Purified non-fusion protein was subjec ted to allergenicity testing by the enzyme allergosorbent test (EAST), West ern blotting, competitive inhibition assays, and basophil histamine release . The deduced protein sequence shared a high degree of identity with other major allergens from fruits, nuts, vegetables, and pollen, and with a famil y of PR-10 pathogenesis related proteins. The recombinant (r) protein was r ecognised by specific IgE from sera of all pear-allergic patients (n = 16) investigated in this study. Hence, the allergen was classified as a major a llergen and named Pyr c 1. The IgE binding characteristics of rPyr c 1 appe ared to be similar to the natural pear protein, as was demonstrated by EAST -inhibition and Western blot-inhibition experiments. Moreover, the biologic al activity of rPyr c 1 was equal to that of pear extract, as indicated by basophil histamine release in two patients allergic to pears. The related m ajor allergens Bet v 1 from birch pollen and Mal d 1 from apple inhibited t o a high degree the binding of IgE to Pyr c 1, whereas Api g 1 from celery, also belonging to this family, had little inhibitory effects, indicating e pitope differences between Bet v 1-related food allergens. Unlimited amount s of pure rPyr c 1 are now available for studies on the structure and epito pes of pollen-related food allergens. Moreover, the allergen may serve as s table and standardised diagnostic material. (C) 2001 Elsevier Science B.V. All rights reserved.