Naslov
Different allergenicity of different apples in birch-sensitive patients with oral allergy syndrome: in vivo study

Autori
Branko Pevec, Mira Radulović Pevec, Asja Stipić Marković

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Allergens for Diagnosis and Treatment of Allergic Disease / Mihaela Zidarn - Golnik, 2005, 9-10

Skup
Annual Meetinf of Allergy and Immunology Section of Slovene Medical Society and University Clinic of Respiratory and allergic Diseases Golnik, Slovenia

Mjesto i datum
Ljubljana, Slovenija, 12.11.2005

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Birch-sensitive; oral allergy syndrome; cross-reactivity; apples

Sažetak
Background. Oral allergy syndrome (OAS) to fruits and vegetables often coexists with pollen allergy. Pollen sensitive patients experience OAS symptoms shortly after ingestion of different plant foodstufs. The pathomechanism is explained by cross-reactivity of IgE antibodies induced by pollen allergens with structurally similar food allergens. Apple is the most frequent cause of OAS in patients sensitive to birch pollen. Major apple allergen, Mal d 1 (18-kDa protein), is responsible for majority of cross reactions due to its homology with major birch pollen allergen Bet v 1. Other apple proteins, Mal d 2 (31-kDa protein), Mal d 3 (9-kDa protein), Mal d 4 (14-kDa protein), etc. may also cross react in some patients. The amounts of apple allergens vary considerably in different strains of apples, and are influenced by maturation, ripening and storage conditions. In vitro studies revealed that the allergenicity of apple is related to the level of expressed Mal d 1. Strains with high relative amount of Mal d 1 (Granny Smith, Golden Delicious, Jonagold, Braeburn, etc.) showed greater allergenicity than those with medium (Sternrenette, Alkmene), low (Boskoop), and very low amount (Jamba, Gloster, Altländer, etc.). Apples purchased from stores contained higher amounts of Mal d 1 than freshly picked ones. Furthermore, the amount of Mal d 1 showed the tendency for the increase during prolonged storage at 4&ordm ; ; C. Instability of commercial apple allergen extracts created a persistent problem of false negative results of skin prick testing (SPT). For that matter, SPT with fresh fruits is considered a useful diagnostic tool. Oral challenge with apple is complicated by several factors: susceptibility of apple allergens to all types of processing, different allergenicity between apple strains and maturation stages, occasional development of tachyphylaxis, and a lack of a consistent standardized model. The aim of this study was to investigate the difference in allergenicity of fresh and ripe apples of five different strains, in a birch-sensitive patients with OAS to apple. We also wanted to develop a simple and accurate model for oral challenge. For that purpose we designed a special scoring system. Material and methods. Thirty patients with clinically manifested allergy and confirmed sensitization to birch pollen and a history of OAS to apple were included into the study. Twelve patients had previously received a birch pollen immunotherapy. Control group consisted of 15 nonatopic subjects. Five different apple strains (Granny Smith, Jonagold, Idared, Gloster, and Golden Delicious) were used for skin prick tests and oral challenge tests. Fresh (fully developed, mature apples, without signs of ripening), and ripe (stored, with signs of ripening) apples of each strain were purchased from local grocery stores. All patients and control subjects were tested with one fresh and one ripe apple of each strain. SPTs were performed with a drop of juice squeezed from an apple slice directly to the forearm. All tests were done in duplicate (a total of 10 SPTs at each forearm), and the mean wheal diameters were used for analyses. Patients were also tested with commercial SPT apple allergen. Oral challenge tests were performed with a slice of each apple chewed for a minute. Symptoms were recorded during the next 15 minutes, and the severity of reaction was evaluated. A scale from 6 to 10 was used to grade reactions from very mild to very strong. Each apple strain to which no symptoms occurred was retested with a whole apple eaten cautiously, bite for bite. Symptoms were recorded and severity of reactions evaluated, only this time a gradation from very mild to very strong reactions was marked 1 to 5. Finally, a scale from 0 (indicating no reaction to a greater amount of sample) to 10 (indicating the strongest reaction to a smaller amount of sample) was obtained, and used for analyses. Results. Our results showed that all ripe apples, regardless of the strain, produced significantly stronger reactions in SPT than fresh ones (mean wheal diameters: Granny Smith – 7.35 ; 5.63*, Jonagold – 7.93 ; 6.06*, Idared – 7.70 ; 6.02*, Gloster – 7.33 ; 5.59*, Golden Delicious – 7.32 ; 5.45*). As there was no significant difference between different strains, we conclude that degree of maturity is more important for skin reactivity than the apple strain itself. SPTs with a commercial apple allergen were negative in all subjects. Severity of reactions in oral challenge tests was also greater with ripe than with fresh apples, although significant difference was reached only for Granny Smith and Golden Delicious (mean score values: Granny Smith – 7.03 ; 5.53*, Jonagold – 6.83 ; 5.40, Idared – 6.53 ; 5.20, Gloster – 5.50 ; 4.17, Golden Delicious – 6.97 ; 5.37*). As opposed to SPT, different apple strains showed different allergenicity. Deduction revealed that the allergenicity decreased in the following order: Granny Smith > Golden Delicious > Jonagold > Idared > Gloster. This result is in full agreement with earlier in vitro studies. Control subjects had negative results in all performed tests. The issue of a birch pollen immunotherapy as the effective therapy for cross-reactive food allergies is still controversial. Symptom scores of our patients who have received a birch pollen immunotherapy were significantly lower in comparison with patients who have not. Contrary to oral challenges, there was no difference in SPTs between patients who have, and those who have not received a birch pollen immunotherapy. To improve the accuracy of evaluation of reaction severity in oral challenges, we designed a special scoring system, which we named PEACE score (PEroral Apple Challenge Evaluation score). Contrary to other scoring systems which mostly used scales from 0 to 3 or 0 to 4, our system uses a scale from 0 to 10, which makes it more sensitive. Other systems (including the VAS score) were based exclusively on a patient’ s judgment of the reaction severity, and thus highly subjective, whereas our system considers the intensity of symptoms, and their different combinations, which makes it more objective and final scores comparable between patients and between different time points in the same patient. Furthermore, our system considers the amount of sample used for challenge. Conclusion. We confirmed in vivo, earlier in vitro findings that some apple strains are more allergenic than others, and that ripe apples cause more severe reactions. This finding may help to advise patients to give priority to less allergenic apples. We also confirmed that a birch pollen specific immunotherapy may decrease symptoms of OAS to apple. SPT with apples is useful in confirmation of the OAS diagnosis, especially with ripe apples which elicit stronger reactions. Unfortunately, it poorly predicts a severity of reaction after ingestion of apple. In cases where reaction severity needs to be evaluated, like in monitoring the effect of immunotherapy, oral challenge test should be performed. Oral challenge started with less allergenic, fresh apple, and followed with ripe apple of the same strain, could be recommended to avoid severe reactions. Although not standardized, both SPT and oral challenge test are suitable for practice, as they reflect a real allergenicity of apples available to patients. Proposed scoring system could, with slight modifications, be used to asses the severity of reactions in challenges with other vegetable foodstufs.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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