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Allergy to freshly consumed apple fruits is often associated to pollinosis and manifested as oral allergy syndrome (OAS). The allergenic properties of apple varieties differ greatly, spanning from low allergenic to high allergenic varieties. The knowledge of the genetic determinants for allergenicity has been of great interest in scientific community for several years, but the molecular mechanisms involved are still little understood. Here, factors putatively involved in allergenicity were investigated at biochemical and molecular level in pollen and in fruits of apple varieties differing in their allergenic potential. Among putative sensitizing factors, transglutaminase (TGase) and phospholipase A 2 (PLA 2 ) were considered together with reactive oxygen species (ROS) and known apple allergen genes, with particular attention devoted to the Mal d 1 gene family, the most important one in sensitization. We found that the expression of some allergen genes and the activities of TGase, PLA 2 and ROS producing enzyme are lower in the hypo-allergenic variety ‘Durello di Forlì’ in comparison with the high-allergenic genotypes ‘Gala’ and ‘Florina’. These results highlight correlations among allergen expressions, enzymatic activities and apple cultivars; these data underline the possibility that some of them could be used in the future as markers for allergenicity. [ABSTRACT FROM AUTHOR]

Abstract: The most important apple allergen in Central Europe and North America is Mal d 1. Apples are a very important source of secondary plant metabolites like polyphenols in human nutrition. It is known that oxidised phenols can bind proteins. These irreversible bindings can lead to a reduced allergenicity. The most important phenols in apple are epicatechin, catechin and their polymeric structures, which have been identified as substrates of the polyphenoloxidase (PPO). The aim of this study was to analyse the influence of naturally occurring catechin and epicatechin contents in apple on the allergenicity of apple fruits. Fruits of the cultivars ‘Elstar’, ‘Diwa’ and ‘Boskoop’ were harvested and stored for 8 and 12weeks in a cold-chamber at 2°C. Mal d 1-, catechin-, epicatechin- and total phenol content as well as the activity of PPO were determined. Correlation analysis showed that naturally occurring catechin as well as epicatechin has no impact on the Mal d 1 content of the tested cultivars: correlation coefficient ranged from −0.203 to 0.501 for the correlation between Mal d 1 and catechin. The results further indicated that the activity of PPO is more important than the content of total phenols to reduce the Mal d 1 level. If there is a high PPO activity, Mal d 1 could be reduced even if the total phenol concentration is low. [Copyright &y& Elsevier]

Abstract: Lipid transfer protein (LTP) has been reported as an important allergen inducing severe systemic reactions in allergic subjects. The aim of the present study was to estimate the role of LTP in diagnosis of apple allergy in children allergic to birch pollen. The prospective study was carried out on a group of 21 children sensitized to birch pollen and apple allergens, confirmed by presence of specific IgE in the sera of patients. Allergens separated by electrophoresis were probed by Western blotting using hypersensitive patients’ sera. Food hypersensitivity to apple was verified by oral food challenge test. Six patients’ sera were hypersensitive to birch pollen and apple proteins. Almost all sera recognized specifically the main allergen of apple peal Mal d 3 with molecular weight <10kDa (LTP). Positive oral challenge to apple was found in 52.4% of investigated children. Children allergic to Mal d 1 presented different clinical symptoms. Sensitization to Mal d 3 is very common in children with apple allergy. No correlation between clinical symptoms and sensitization to recombinant apple allergens has been found, LTP may be useful in diagnosis of apple allergy. [Copyright &y& Elsevier]

• Apple allergy is a well-characterized fruit allergies linked to pollinosis. • Concerning type and amount of allergens apple cultivars show broad biodiversity. • Five Mal d 1 isoallergens were tested for the first time against allergic patient's sera. • Besides apple varieties, differences among isoallergens and patients were found. Apple-related allergy is increasing among European population. Avoidance of apple fruit consumption is the only strategy for sensitized people, with a subsequent shortage of healthy nutrients in the diet. Four different protein families, Mal d 1 to 4, determine the allergy to apple causing syndromes known as oral allergy syndrome (OAS) or gastro-intestinal/generalized syndrome (GS) in sensitized patients. With the aim to highlight the dissimilarities in the immunological response inside the Mal d 1 family, recognized as main determinant for OAS, single purified allergens were tested against sera of paediatric and adult patients suffering for both syndromes. Here, we found that Mal d 1 isoallergens showed a remarkable different allergenicity potential, thus indicating an individual pattern in each patient and a diverse sensitization between age groups. Moreover, two different allergens, Mald 2.01 and Mal d 4.01, were analyzed with the above sera. In addition to patients and allergens variability, differences in amount and localization of the allergens, detected by patient's sera, were revealed among hypo- and hyper allergenic apple varieties, confirming the complexity of this food allergy. [ABSTRACT FROM AUTHOR]