Characterization of Der p 21, a new important allergen derived from the gut of house dust mites.
BACKGROUND
The house dust mite (HDM) Dermatophagoides pteronyssinus is a major allergen source eliciting allergic asthma. The aim of the study was to identify new important HDM allergens associated with allergic asthma.


METHODS
A cDNA coding for a new mite allergen, designated Der p 21, was isolated using immunoglobulin E (IgE) antibodies from patients with allergic asthma out of a D. pteronyssinus expression cDNA library and expressed in Escherichia coli.


RESULTS
Circular dichroism analysis of the purified allergen showed that rDer p 21 (14 726 Da) is one of the few mite allergens with an alpha-helical secondary structure. The protein exhibited high thermal stability and refolding capacity, and, as determined by small angle X-ray scattering, formed a dimer consisting of two flat triangles. rDer p 21 bound high levels of patients' IgE antibodies and showed high allergenic activity in basophil activation experiments. Rabbit anti-Der p 21 IgG antibodies inhibited mite-allergic patients' IgE binding and allowed the ultrastructural localization of the allergen in the midgut (epithelium, lumen and faeces) of D. pteronyssinus by immunogold electron microscopy. Der p 21 revealed sequence homology with group 5 mite allergens, but IgE and IgG reactivity data and cross-inhibition studies identified it as a new mite allergen.


CONCLUSIONS
Der p 21 is a new important mite allergen which is liberated into the environment via faecal particles and hence may be associated with allergic asthma.
Weghofer
M
M
Division of Immunopathology, Department of Pathophysiology, Center for Physiology and Pathophysiology, Medical University of Vienna, Vienna, Austria.
Dall'Antonia
Y
Y
Grote
M
M
Stöcklinger
A
A
Kneidinger
M
M
Balic
N
N
Krauth
M-T
MT
Fernández-Caldas
E
E
Thomas
W R
WR
van Hage
M
M
Vieths
S
S
Spitzauer
S
S
Horak
F
F
Svergun
D I
DI
Konarev
P V
PV
Valent
P
P
Thalhamer
J
J
Keller
W
W
Valenta
R
R
Vrtala
S
S
D000485:Allergens / Q000737:chemistry* / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D000595:Amino Acid Sequence; D000818:Animals; D039741:Antigens, Dermatophagoides / Q000737:chemistry* / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D001249:Asthma / Q000276:immunology*; D001483:Base Sequence; D001491:Basophils / Q000276:immunology; D002942:Circular Dichroism; D018076:DNA, Complementary; D040002:Dermatophagoides pteronyssinus / Q000276:immunology* / Q000648:ultrastructure; D004391:Dust / Q000276:immunology; D004847:Epithelial Cells / Q000276:immunology / Q000648:ultrastructure; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007422:Intestines / Q000276:immunology / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data
D000485:Allergens; D039741:Antigens, Dermatophagoides; D018076:DNA, Complementary; D004391:Dust; D007073:Immunoglobulin E