title: Molecular and immunological characterization of a wheat serine proteinase inhibitor as a novel allergen in baker's asthma.
abstract: IgE-mediated sensitization to wheat flour belongs to the most frequent causes of occupational asthma. A cDNA library from wheat seeds was constructed and screened with serum IgE from baker's asthma patients. One IgE-reactive phage clone contained a full-length cDNA coding for an allergen with a molecular mass of 9.9 kDa and an isoelectric point of 6. According to sequence analysis it represents a member of the potato inhibitor I family, a group of serine proteinase inhibitors, and thus is the first allergen belonging to the group 6 pathogenesis-related proteins. The recombinant wheat seed proteinase inhibitor was expressed in Escherichia coli and purified to homogeneity. According to circular dichroism analysis, it represented a soluble and folded protein with high thermal stability containing mainly beta-sheets, random coils, and an alpha-helical element. The recombinant allergen showed allergenic activity in basophil histamine release assays and reacted specifically with IgE from 3 of 22 baker's asthma patients, but not with IgE from grass pollen allergic patients or patients suffering from food allergy to wheat. Allergen-specific Abs were raised to localize the allergen by immunogold electron microscopy in the starchy endosperm and the aleuron layer. The allergen is mainly expressed in mature wheat seeds and, despite an approximately 50% sequence identity, showed no relevant cross-reactivity with allergens from other plant-derived food sources such as maize, rice, beans, or potatoes. Recombinant wheat serine proteinase inhibitor, when used in combination with other specific allergens, may be useful for the diagnosis and therapy of IgE-mediated baker's asthma.
authors.affiliation: Division of Immunopathology, Department of Pathophysiology, Center of Physiology, Pathophysiology, and Immunology, Medical University of Vienna, Vienna, Austria.
authors.forename: Claudia
authors.initials: C
authors.lastname: Constantin
authors.forename: Santiago
authors.initials: S
authors.lastname: Quirce
authors.forename: Monika
authors.initials: M
authors.lastname: Grote
authors.forename: Alisher
authors.initials: A
authors.lastname: Touraev
authors.forename: Ines
authors.initials: I
authors.lastname: Swoboda
authors.forename: Angelika
authors.initials: A
authors.lastname: Stoecklinger
authors.forename: Adriano
authors.initials: A
authors.lastname: Mari
authors.forename: Josef
authors.initials: J
authors.lastname: Thalhamer
authors.forename: Erwin
authors.initials: E
authors.lastname: Heberle-Bors
authors.forename: Rudolf
authors.initials: R
authors.lastname: Valenta
mesh_terms: D000328:Adult; D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000595:Amino Acid Sequence; D001249:Asthma / Q000276:immunology*; D001483:Base Sequence; D005260:Female; D015723:Gene Library; D006801:Humans; D007073:Immunoglobulin E; D008297:Male; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D008969:Molecular Sequence Data; D009784:Occupational Diseases / Q000276:immunology*; D010802:Phylogeny; D012639:Seeds / Q000737:chemistry; D016415:Sequence Alignment; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D014908:Triticum / Q000737:chemistry / Q000276:immunology*; D021182:Wheat Hypersensitivity / Q000276:immunology*
chemical_list: D000485:Allergens; D015842:Serine Proteinase Inhibitors; D007073:Immunoglobulin E