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Clin Exp Allergy. 2018 Sep;48(9):1206-1213. doi: 10.1111/cea.13208. Epub 2018 Jul 12.

A subset of walnut allergic adults is sensitized to walnut 11S globulin Jug r 4.

Author information

1
Department of Dermatology/Allergology, University Medical Center Utrecht, Utrecht, The Netherlands.
2
The Netherlands Organization for Applied Scientific Research (TNO), Zeist, The Netherlands.
3
Laboratory of Translational Immunology, University Medical Center Utrecht, Utrecht, The Netherlands.
4
Department of Experimental and Clinical Medicine, Magna Graecia University of Catanzaro, Catanzaro, Italy.

Abstract

BACKGROUND:

The role of sensitization to commercially available allergens of English walnut (Juglans regia) Jug r 1, 2 and 3 in walnut allergy has been previously investigated in walnut allergic adults and was unable to explain all cases of walnut allergy.

OBJECTIVES:

Identify recognized walnut allergens, other than the ones previously investigated (Jug r 1-3), in walnut allergic adults and determine the sensitization frequency and diagnostic value.

METHODS:

Three different in-house walnut extracts were prepared and analysed on SDS-PAGE blots to identify allergenic walnut proteins. Immunoblots and immunoprecipitation, followed by LC-MS analysis, were performed to screen for, and confirm, IgE binding to walnut allergens in selected walnut allergic adults. In a cohort of 55 walnut challenged adults, including 33 allergic and 22 tolerant, sensitization to native and recombinant walnut allergen Jug r 4 was assessed using immunoblotting and immuno-line blot (EUROLINE), respectively.

RESULTS:

Screening of sera of 8 walnut allergic adults identified Jug r 4 as an allergen in our population. In the total cohort of 55 subjects, 5 were positive for Jug r 4 on immunoblot and 10 on EUROLINE. All but one EUROLINE positive subject had a positive food challenge (sensitivity 27%, specificity 95%, PPV 90%, NPV 47%). All 5 subjects positive on immunoblot were also positive on EUROLINE. LC-MS analysis showed a lack of Jug r 4 in the ImmunoCAP extract. Co-sensitization to other 11S albumins (eg hazelnut Cor a 9) was common in Jug r 4 sensitized subjects, potentially due to cross-reactivity.

CONCLUSIONS:

Walnut 11S globulin Jug r 4 is a relevant minor allergen, recognized by 27% of walnut allergic adults. It has a high positive predictive value of 90% for walnut allergy. Specific IgE against Jug r 4 occurred mostly with concomitant sensitization to other walnut components, mainly Jug r 1.

KEYWORDS:

11s globulin; Jug r 4; double blind placebo controlled food challenge; immunoblot; walnut allergy

PMID:
29904971
DOI:
10.1111/cea.13208

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