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Practitioner's Corner
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
Homolog
Takaoka Y
1
, KondoY
2
, Matsunaga K
3
, Aoki Y
3,4,5
, Hasegawa E
3,5
,
Tokuda R
6
, Fujisawa T
7
, Morikawa A
8
, Doi S
9
1
Department of Pediatrics, Osaka Habikino Medical Center,
Habikino, Japan
2
Department of Pediatrics, Fujita Health University, Bantane
Hospital, Nagoya, Japan
3
Department of Integrative Medical Science for Allergic Disease,
Fujita Health University School of Medicine, Nagoya, Japan
4
Department of Respiratory Medicine, Fujita Health University
School of Medicine, Nagoya, Japan
5
General Research and Development Institute, Hoyu Co., Ltd.,
Nagoya, Japan
6
Tokuda Family Clinic, Ise, Japan
7
National Hospital Organization Mie Hospital, Tsu, Japan
8
Kita Kanto Allergy Institute Kibounoie Hospital, Midori, Japan
9
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
homolog.
Palabras clave:
Alérgeno. Anafilaxia.
Eriobotrya japonica
. Mal d 1.
Bet v 1 homólogo.
Fruit allergens from plants belonging to the
Rosaceae
(rose)
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
Rosaceae
family.
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].
Figure.
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)
50
25
20
15
10
37
a 1
1617 18
13 15
12 14
11 10
7
4
9
6
3
8
5
2
Patient serum
Control serum
382