Background Hev b 1 represents one of the most important allergens in Hevea
brasiliensis latex. It is difficult to get an appropriate amount of native
Hev b 1 (nHev b 1) for research purposes.
Objective The aim of this study was to produce sufficient amounts of Hev b
1 by recombinant methods to prove its suitability for latex allergy diagnos
tics.
Methods We isolated total RNA of Hevea brasiliensis leaves and synthesized
cDNA by RT PCR. Recombinant Hev b 1 (rHev b 1) as well as three fragments (
amino acid residues 29-137, 48-137, 78-137) were subcloned and expressed as
fusion proteins with Maltose-binding protein (MBP) in Escherichia coli. Th
e MBP-rHev b 1 fusion protein was examined by RAST with the CAP method, his
tamine release test and immunoblots with human sera from spina bifida patie
nts as well as from health care workers with latex allergy and monoclonal a
ntibodies.
Results Histamine release test and immunoblots revealed the high allergenic
ity of the MBP-rHev b 1 construct. By the CAP method, 54 out of 58 serum sa
mples (93%) from latex-sensitized spina bifida patients previously showing
immunoglobulin (Ig) E to nHev b 1 exhibited IgE-binding to rHev b 1. Among
71 latex-allergic health care workers tested, 16 (22.5%) had IgE antibodies
to rHev b 1. The analysis of the fusion proteins carrying rHev b 1 fragmen
ts revealed that the loss of the N-terminal 28 amino acid residues did not
affect IgE-binding. In contrast, the lack of the first 47 amino acid residu
es led to decreased IgE-binding reactivity in two out of four sera tested,
whereas the;absence of the N-terminal 77 residues abolished IgE-binding in
these two sera.
Conclusion The MBP-rHev b 1 fusion protein exhibits a corresponding IgE-bin
ding reactivity to nHev b 1 and may therefore substitute natural Hev b 1 fo
r both in vitro diagnostics and research purposes.