Calcium-dependent immunoglobulin E recognition of the apo- and calcium-bound form of a cross-reactive two EF-hand timothy grass pollen allergen, Phl p 7.
Type I allergy, an immunodisorder that affects almost 20% of the population worldwide, is based on the immunoglobulin E (IgE) recognition of per se innocuous antigens (allergens). Pollen from wind-pollinated plants belong to the most potent allergen sources. We report the isolation of a cDNA coding for a 8.6 kDa two EF-hand calcium binding allergen, Phl p 7, from a timothy grass (Phleum pratense) pollen expression cDNA library, using serum IgE from a grass pollen allergic patient. Sequence analysis identified Phl p 7 as a member of a recently discovered subfamily of pollen-specific calcium binding proteins. Recombinant Phl p 7 was expressed in Escherichia coli and purified to homogeneity as determined by mass spectroscopy. Approximately 10% of pollen allergic patients displayed IgE reactivity to rPhl p 7 and Phl p 7-homologous allergens present in pollens of monocotyledonic and dicotyledonic plants. Circular dichroism analysis of the calcium-bound and apo-rPhl p 7 indicated that differences in IgE recognition may be due to calcium-induced changes in the protein conformation. The fact that patients mount IgE antibodies against different protein conformations is interpreted as a footprint of a preferential sensitization against either form. The biological activity of rPhl p 7 was demonstrated by its ability to induce basophil histamine release and immediate type skin reactions in sensitized individuals. In conclusion, IgE binding to Phl p 7 represents an example for the conformation-dependent IgE recognition of an allergen. Recombinant Phl p 7 may be used for diagnosis and perhaps treatment of a group of patients who suffer from allergy to pollens of many unrelated plant species.
Niederberger
V
V
Department of Otorhinolaryngology, Institute of Medical and Chemical Laboratory Diagnostics, University of Vienna, Austria.
Hayek
B
B
Vrtala
S
S
Laffer
S
S
Twardosz
A
A
Vangelista
L
L
Sperr
W R
WR
Valent
P
P
Rumpold
H
H
Kraft
D
D
Ehrenberger
K
K
Valenta
R
R
Spitzauer
S
S
D000485:Allergens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D003429:Cross Reactions; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D006636:Histamine Release; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000209:etiology; D007073:Immunoglobulin E / Q000378:metabolism*; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006109:Poaceae / Q000235:genetics / Q000276:immunology; D011058:Pollen / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D011487:Protein Conformation; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000485:Allergens; D001059:Apoproteins; D017931:DNA Primers; D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D011994:Recombinant Proteins; D007073:Immunoglobulin E; D002118:Calcium