B. Ghosh et al., IMMUNOLOGICAL AND MOLECULAR CHARACTERIZATION OF AMB P V ALLERGENS FROM AMBROSIA-PSILOSTACHYA (WESTERN RAGWEED) POLLEN, The Journal of immunology, 152(6), 1994, pp. 2882-2889
We have purified and characterized the Amb p V allergen (A1 variant) f
rom western ragweed (Ambrosia psilostachya) pollen. This allergen was
found to be highly cross-reactive with the Amb a VA1 allergen From sho
rt ragweed (A. artemisiifolia) pollen in a competitive double-Ab radio
immunoassay (DARIA) and the two allergens showed concordant allergenic
potency in histamine-release experiments. We cloned and sequenced sev
eral Amb p V genes from western ragweed pollen and flowers by direct P
CR of genomic DNA. The amino acid sequences deduced from the nucleotid
e sequences indicated the presence of multiple forms of Amb p V that c
ould be broadly classified into two groups: Amb p VA and Amb p VB vari
ants. 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 re
sidues 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 Am
b p VB2 variants. We have generated model structures of Amb p VA1, VA2
, VA3, and VB1 variants from the nuclear magnetic resonance-derived st
ructure of Amb a VA1 by homology modeling. Comparison of antigenic epi
topes predicted for the structures of Amb p V variants and Amb a VA1 e
xplains the observed crossreactivity of the two ragweed proteins and s
uggests the epitopes likely to be involved in Ab recognition.