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The Journal of Immunology, Vol 152, Issue 6 2882-2889, Copyright © 1994 by American Association of Immunologists
ARTICLES |
B Ghosh, T Rafnar, MP Perry, D Bassolino-Klimas, WJ Metzler, DG Klapper and DG Marsh
Johns Hopkins Asthma and Allergy Center, Johns Hopkins University School of Medicine, Baltimore, MD 21224.
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.
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