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J Investig Allergol Clin Immunol 2019; Vol. 29(5): 378-398

© 2019 Esmon Publicidad

Allergy and Anaphylactic Reaction to Loquat


Eriobotrya japonica

) Are Induced by a Bet v 1


Takaoka Y


, KondoY


, Matsunaga K


, Aoki Y


, Hasegawa E



Tokuda R


, Fujisawa T


, Morikawa A


, Doi S



Department of Pediatrics, Osaka Habikino Medical Center,

Habikino, Japan


Department of Pediatrics, Fujita Health University, Bantane

Hospital, Nagoya, Japan


Department of Integrative Medical Science for Allergic Disease,

Fujita Health University School of Medicine, Nagoya, Japan


Department of Respiratory Medicine, Fujita Health University

School of Medicine, Nagoya, Japan


General Research and Development Institute, Hoyu Co., Ltd.,

Nagoya, Japan


Tokuda Family Clinic, Ise, Japan


National Hospital Organization Mie Hospital, Tsu, Japan


Kita Kanto Allergy Institute Kibounoie Hospital, Midori, Japan


Faculty of Education, Shitennoji University, Habikino, Japan

J Investig Allergol Clin Immunol 2019; Vol. 29(5): 382-383

doi: 10.18176/jiaci.0406

Key words:

Allergen. Anaphylaxis.

Eriobotrya japonica

. Mal d 1. Bet v 1


Palabras clave:

Alérgeno. Anafilaxia.

Eriobotrya japonica

. Mal d 1.

Bet v 1 homólogo.

Fruit allergens from plants belonging to the



family cross-react with pollen from plants of the Betulaceae

(birch) family [1]. The causative allergens include Bet v 1 [2].

Typically, the primary symptoms of allergic reactions to Bet v 1

homologs are oral, although there are reports of generalized

symptoms in the case of soybean allergies [3]. Loquat


Eriobotrya japonica

), which is grown inAsia and several other

locations, is also a member of the



Loquat allergy is diagnosed based on the clinical history

and skin prick test results [4]. However, the primary allergen

responsible for loquat allergy remains unidentified. In this

study, we collected the serum of individuals with loquat

allergy—including those who had experienced anaphylactic

responses—to identify the causative allergen. This approach

may lead to better prognostic and therapeutic options for the

treatment of loquat allergy.

Fifteen patients with positive results in prick-prick testing

with fresh loquat (wheal diameter of 3 mm or more) using a

bifurcated needle (Tokyo M.I CO. Inc) were selected for this

study (Supplementary Table 1). There were 13 complaints of

oral symptoms induced by loquat and 2 of systemic symptoms.

The titers of white birch pollen (Bet v 1) and Mal d 1–specific

IgE antibodies were positive in all the patients for whom

residual serum was available. Serum samples from 2 healthy

volunteers without food allergy and umbilical cord blood from

infants born at FujitaMedical University were used as controls.

The study was approved by the Research Ethics Committee

of Fujita Medical University (Approval Number 10-216), and

written informed consent was obtained from the patients and

parents of patients aged under 19 years of age.

We electrophoresed the loquat extract proteins as described

by Laemmli [5] using 4%-12% Bis-Tris gels (Thermo Fisher

Scientific). Following SDS-PAGE, loquat-extracted proteins

were transferred to an Immobilon-P polyvinylidene fluoride

membrane (pore size, 0.45-μm;Millipore) and reactedwith20-fold

diluted serum. Alkaline phosphatase–labeled polyclonal goat

antihuman IgE (ε) antibody (Kirkegaard & Perry Laboratories)

and 5-bromo-4-chloro-3-indolyl phosphate/nitroblue

tetrazolium phosphatase substrates (1-Component System;

Kirkegaard & Perry Laboratories) were used to detect IgE

antibodies bound to the antigen. Target protein analysis with

a mass spectrometer (TripleTOF; AB Sciex) was performed

following the method reported by Yagami et al [6]. Protein

analysis was performed using ProteinPilot software version

5.0 (AB Sciex), and proteins were identified using sequence

data from UniProt.

Several protein bands that reacted with patient IgE were

detected by immunoblotting; these bands ranged in size from

15 kDa to 50 kDa (Figure). The bands that reacted with more

than half of the samples had a molecular weight of 15 kDa

(93% positive) or 17 kDa (100% positive). In the immunoblot,

the 15-kDa band was thinner than the 17-kDa band.

The 15- and 17-kDa bands were identified by mass

spectrometry as Mal d 1.02 (accession number Q9S7M5).

Protein coverage for each band was 100% (159 aa/159 aa for

17 kDa) and 95.6% (152 aa/159 aa for 15 kDa). The N-termini

of the 15-kDa bands showed complete homology withMal d 1.

However, the degree of homology of the corresponding

C-termini of the 15-kDa bands indicated C-terminal deletions

after the 153rd amino acid sequence. We believe that the 15-

kDa proteins may be identical to the 17-kDa proteins, albeit

with C-terminal deletions. The binding capacity of 15-kDa

proteins may be lower than that of 17-kDa proteins because

the presence of epitopes has been reported at the C-terminus

of Mal d 1 [7].


Immunoblot assay of sera from patients with confirmed loquat

allergy and controls. More than half of the patients presented specific

IgE–binding bands with relative molecular weights (MW) of 15 and

17 kDa (indicated by arrows and

). The white circle indicates a specific

IgE–binding band. Lane a, loquat proteins stained with amido black.

MW (kDa)







a 1

1617 18

13 15

12 14

11 10









Patient serum

Control serum