Background: The rubber elongation factor in Hevea rubber (Hev b 1) is one of the most important latex allergen and is leading cause of latex type 1 hypersensitivity in children with spina bifida.
Objective: The aim of this study was to define the allergenic and antigenic epitopes of Hev b 1.
Methods: The immunoglobulin- (Ig)E and IgG antibody binding sites on Hev b 1 allergen were delineated by enzyme linked immunosorbent assay (ELISA) using synthetic overlapping peptides covering the whole Hev b 1 sequence. In order to improve the binding capacity and specificity all peptides were biotinylated at the N-terminal end via a 6-aminohexanoic acid as spacer and then adsorbed to streptavidin pre-coated microtitre plates. Fine mapping to define the essential amino acid residues for the antibody binding was achieved by using overlapping peptides with one amino acid offset.
Results: It was demonstrated that the IgE epitopes were located in different regions of Hev b 1 including the C-terminal segment (121-137) and the segments with amino acid residues of 30-49 and 46-64. Two monoclonal antibodies (MoAbs) II2F3 and II4G9 raised against purified Hev b 1 recognized the C-terminal segment only. The results of epitope mapping with three rabbit antisera revealed that five positive peptides, including the epitope peptides 31-49, 46-64 and 121-137, were involved in the antibody-binding sites. Fine mapping on the segments 46-64 and 121-137 showed that the two MoAbs reacted with the peptide 125-134 in the C-terminal region, whereas the peptide with amino acids 124-134 was essential for recognition by human IgE antibodies. Epitopes to rabbit polyclonal IgG and human IgE were also found to be involved in the amino acid residues of 47-59.
Conclusion: Our results indicate that the most allergenic/antigenic portions of Hev b 1 allergen are the C-terminal region and the region with amino acid residues of 31-64. In both regions, the minimal IgE-binding epitope is almost identical with the IgG-binding epitope.