Research Summary: Reduction of Cross-Reactive Carbohydrate Determinants in Plant Foodstuff: Elucidation of Clinical Relevance and Implications for Allergy Diagnosis



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.


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.


Publisher: Public Library of Science

Date Published: 14-March-2011

Author(s): Kaulfürst-Soboll H., Mertens M., Brehler R., von Schaewen A.


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