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Title: Analysis of avocado allergen (Prs a 1) IgE-binding peptides generated by simulated gastric fluid digestion
Authors: Díaz-Perales, Araceli
Blanco, Carlos
Sánchez-Monge, Rosa
Varela, Javier
Carrillo, Teresa 
Salcedo, Gabriel
UNESCO Clasification: 32 Ciencias médicas
320701 Alergias
2412 Inmunología
Keywords: Allergen digestion
Simulated gastric fluid
Food allergy
Prs a 1
Hevein-like domain, et al
Issue Date: 2003
Journal: Journal of Allergy and Clinical Immunology 
Abstract: Background: Resistance to pepsin digestion has been claimed to be a characteristic of food allergens that can induce severe adverse reactions. Moreover, pepsin treatment is included in protocols to evaluate the potential allergenicity of transgenic foods. Allergenic plant class I chitinases, such as avocado Prs a 1, are the panallergens involved in the latex-fruit syndrome. Previous reports indicated their susceptibility to simulated gastric fluid (SGF) digestion. Objective: We sought to evaluate the IgE-binding capacity and the in vivo reactivity of the SGF products of the avocado allergen Prs a 1. Methods: Patients with a clinical history of latex-fruit allergy syndrome, a positive skin prick test (SPT) response to Prs a 1, and specific IgE to avocado were selected. Untreated and SGF-digested Prs a 1 samples were analyzed by means of IgE and IgG immunoblotting, IgE immunoblotting and ELISA-inhibition assays, and SPTs. Peptides from SGF-digested samples were fractionated by means of HPLC, characterized by N-terminal amino acid sequencing and matrix-assisted laser desorption/ionization analysis, and tested for in vivo reactivity with SPTs. Results: Neither protein staining nor IgE immunoblotting with a pool of sera from allergic patients resulted in the detection of any band after SDS-PAGE separation of an SGF-digested sample of Prs a 1. However, this sample showed a similar inhibitory potency to that of untreated Prs a 1 in both immunoblot- and ELISA-inhibition assays (up to 70% inhibition of the IgE binding to crude avocado extract) and induced positive SPT responses in 5 of 8 allergic patients. Peptides from SGF-digested Prs a 1 were separated by means of HPLC, and 4 of them reached more than 50% inhibition values when using avocado extract as the solid phase in ELISA-inhibition assays. Reactive peptides were located both in the N-terminal hevein-like domain and in the catalytic domain of Prs a 1. Those corresponding to the hevein-like domain (approximately 5100 d) produced positive SPT responses in 5 of 8 allergic patients, whereas 2 peptides located in the catalytic domain (approximately 1400 and 2500 d) were reactive in 2 or 3 of the 8 patients. Conclusion: Prs a 1 was extensively degradated when subjected to SGF digestion. However, the resulting peptides, particularly those corresponding to the hevein-like domain, were clearly reactive both in vitro and in vivo.
ISSN: 0091-6749
DOI: 10.1016/j.jaci.2003.07.006
Source: Journal of Allergy and Clinical Immunology[ISSN 0091-6749],v. 112, p. 1002-1007 (Noviembre 2003)
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