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Analysis of avocado allergen (Prs a 1) IgE-binding peptides generated by simulated gastric fluid digestion.

AbstractBACKGROUND:
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.
AuthorsAraceli Díaz-Perales, Carlos Blanco, Rosa Sánchez-Monge, Javier Varela, Teresa Carrillo, Gabriel Salcedo
JournalThe Journal of allergy and clinical immunology (J Allergy Clin Immunol) Vol. 112 Issue 5 Pg. 1002-7 (Nov 2003) ISSN: 0091-6749 [Print] United States
PMID14610495 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Allergens
  • Antigens, Plant
  • Peptide Fragments
  • Plant Proteins
  • Immunoglobulin E
  • Chitinases
  • Prs a 1 allergen
Topics
  • Allergens (immunology, metabolism)
  • Antigens, Plant
  • Chitinases (immunology, metabolism)
  • Chromatography, High Pressure Liquid
  • Digestion (physiology)
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme-Linked Immunosorbent Assay
  • Gastric Juice (metabolism)
  • Humans
  • Immunoblotting
  • Immunoglobulin E (immunology)
  • Peptide Fragments (biosynthesis, immunology)
  • Persea (immunology)
  • Plant Proteins
  • Staining and Labeling

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