Reduction of cross-reactive carbohydrate determinants in plant foodstuff: elucidation of clinical relevance and implications for allergy diagnosis

PLoS One. 2011 Mar 14;6(3):e17800. doi: 10.1371/journal.pone.0017800.

Abstract

Background: A longstanding debate in allergy is whether or not specific immunoglobulin-E antibodies (sIgE), recognizing cross-reactive carbohydrate determinants (CCD), are able to elicit clinical symptoms. In pollen and food allergy, ≥20% of patients display in-vitro CCD reactivity based on presence of α1,3-fucose and/or β1,2-xylose residues on N-glycans of plant (xylose/fucose) and insect (fucose) glycoproteins. Because the allergenicity of tomato glycoallergen Lyc e 2 was ascribed to N-glycan chains alone, this study aimed at evaluating clinical relevance of CCD-reduced foodstuff in patients with carbohydrate-specific IgE (CCD-sIgE).

Methodology/principal findings: Tomato and/or potato plants with stable reduction of Lyc e 2 (tomato) or CCD formation in general were obtained via RNA interference, and gene-silencing was confirmed by immunoblot analyses. Two different CCD-positive patient groups were compared: one with tomato and/or potato food allergy and another with hymenoptera-venom allergy (the latter to distinguish between CCD- and peptide-specific reactions in the food-allergic group). Non-allergic and CCD-negative food-allergic patients served as controls for immunoblot, basophil activation, and ImmunoCAP analyses. Basophil activation tests (BAT) revealed that Lyc e 2 is no key player among other tomato (glyco)allergens. CCD-positive patients showed decreased (re)activity with CCD-reduced foodstuff, most obvious in the hymenoptera venom-allergic but less in the food-allergic group, suggesting that in-vivo reactivity is primarily based on peptide- and not CCD-sIgE. Peptide epitopes remained unaffected in CCD-reduced plants, because CCD-negative patient sera showed reactivity similar to wild-type. In-house-made ImmunoCAPs, applied to investigate feasibility in routine diagnosis, confirmed BAT results at the sIgE level.

Conclusions/significance: CCD-positive hymenoptera venom-allergic patients (control group) showed basophil activation despite no allergic symptoms towards tomato and potato. Therefore, this proof-of-principle study demonstrates feasibility of CCD-reduced foodstuff to minimize 'false-positive results' in routine serum tests. Despite confirming low clinical relevance of CCD antibodies, we identified one patient with ambiguous in-vitro results, indicating need for further component-resolved diagnosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allergens / immunology
  • Basophils / immunology
  • Carbohydrates / immunology*
  • Cross Reactions / immunology*
  • Epitopes / immunology
  • Food Hypersensitivity / blood
  • Food Hypersensitivity / diagnosis*
  • Food Hypersensitivity / immunology*
  • Fruit / chemistry
  • Gene Silencing
  • Humans
  • Immunoglobulin E / blood
  • Immunoglobulin G / blood
  • Lycopersicon esculentum / immunology*
  • N-Acetylglucosaminyltransferases / metabolism
  • Plant Extracts
  • Plant Proteins / immunology
  • Reproducibility of Results
  • Solanum tuberosum / immunology*

Substances

  • Allergens
  • Carbohydrates
  • Epitopes
  • Immunoglobulin G
  • Plant Extracts
  • Plant Proteins
  • Immunoglobulin E
  • N-Acetylglucosaminyltransferases