title: Molecular characterization of Hor v 9. Conservation of a T-cell epitope among group IX pollen allergens and human VCAM and CD2.
abstract: We have cloned, sequenced and expressed a recombinant group IX pollen allergen from barley (Hordeum vulgare). Hor v 9 is a polypeptide of 313 amino acids. The Hor v 9 cDNA clone was engineered into the E. coli protein expression vector pMAL and expressed as a fusion of maltose binding protein and truncated Hor v 9. Polyclonal antibodies to the fusion protein were raised in mice. Cross-reactive proteins, RNA and DNA homologues were found in many agricultural species including wheat, rye, triticale, oats, maize, sunflower and flax. The presence of group IX-like proteins in a variety of agricultural crops may represent a previously uncharacterized aeroallergenic occupational hazard. Sequence comparisons of the barley allergen, Hor v 9, with Poa p 9 and other cloned group IX pollen allergens revealed putative structural domains common to all. These include a signal peptide, two conserved immunoglobulin-like motifs, a 150 amino acid highly conserved carboxyterminal domain and a carboxyterminal transmembrane helix. This structural arrangement is also found in cell adhesion molecules. The highly conserved T-cell epitope previously characterized and mapped in group IX allergens (and present in Hor v 9) was found in several human cell adhesion molecule sequences (VCAM, NCAM and CD2). This T-cell epitope corresponded to the most highly conserved amino acid residues common to all group IX homologues sequenced to date. CD2 and VCAM are known to play a role in allergic inflammation: VCAM is involved in the recruitment of lymphocytes to sites of inflammation, and cross-linking CD2 leads to T-cell activation. We anticipate that the similar structural arrangement of group IX allergens and human cell adhesion molecules, as well as the presence of a T-cell epitope common to group IX pollen allergens and cell adhesion molecules, will have important consequences in the natural history of the atopic immune response.
authors.affiliation: Monsanto Company, St. Louis, Missouri 63021, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Astwood
authors.forename: R D
authors.initials: RD
authors.lastname: Hill
mesh_terms: D000485:Allergens / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D052179:Antigens, Plant; D001666:Binding Sites, Antibody; D018801:CD2 Antigens / Q000737:chemistry; D015815:Cell Adhesion Molecules / Q000737:chemistry; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000378:metabolism; D015870:Gene Expression; D005822:Genetic Vectors; D001467:Hordeum / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology*; D011058:Pollen / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D018801:CD2 Antigens; D015815:Cell Adhesion Molecules; D018984:Epitopes, T-Lymphocyte; C106779:Hor v 9 protein, Hordeum vulgare; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins