Immunologic and molecular characterization of Amb p V allergens from Ambrosia psilostachya (western Ragweed) pollen.
We have purified and characterized the Amb p V allergen (A1 variant) from western ragweed (Ambrosia psilostachya) pollen. This allergen was found to be highly cross-reactive with the Amb a VA1 allergen from short ragweed (A. artemisiifolia) pollen in a competitive double-Ab radioimmunoassay (DARIA) and the two allergens showed concordant allergenic potency in histamine-release experiments. We cloned and sequenced several Amb p V genes from western ragweed pollen and flowers by direct PCR of genomic DNA. The amino acid sequences deduced from the nucleotide sequences indicated the presence of multiple forms of Amb p V that could be broadly classified into two groups: Amb p VA and Amb p VB variants. The sequences of the Amb p VA variants are highly homologous to Amb a V (about 90% identity) and very similar to the protein sequence that we obtained. The Amb p VB variants share approximately 65% amino acid homology with Amb a V and have five to seven cysteine residues as compared with the eight found in Amb a V and Amb t V. Two cysteine residues that form disulfide bonds in other Amb Vs (positions 19 and 43 in Amb a V) are replaced by serine and alanine in the Amb p VB1 and Amb p VB2 variants. We have generated model structures of Amb p VA1, VA2, VA3, and VB1 variants from the nuclear magnetic resonance-derived structure of Amb a VA1 by homology modeling. Comparison of antigenic epitopes predicted for the structures of Amb p V variants and Amb a VA1 explains the observed cross-reactivity of the two ragweed proteins and suggests the epitopes likely to be involved in Ab recognition.
Ghosh
B
B
Johns Hopkins Asthma and Allergy Center, Johns Hopkins University School of Medicine, Baltimore, MD 21224.
Rafnar
T
T
Perry
M P
MP
Bassolino-Klimas
D
D
Metzler
W J
WJ
Klapper
D G
DG
Marsh
D G
DG
D000485:Allergens / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D001483:Base Sequence; D001491:Basophils / Q000378:metabolism; D003001:Cloning, Molecular; D003429:Cross Reactions; D006636:Histamine Release; D006801:Humans; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000276:immunology; D011058:Pollen / Q000276:immunology*
D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; C069543:group 5 allergens, Ambrosia