Human IgE-binding epitopes of the latex allergen Hev b 5

Background: Hev b 5 is an acidic protein (isoelectric point, 3.5) rich in g lutamic acid with 9 repeated amino acid (AA) sequences of XEEX or XEEEX, Al though its function in Hevea brasiliensis unknown, Hev b 5 has been identif ied as a major latex allergen. Immunoblot inhibition studies suggest Hev b 5 exists as multiple isoforms or contains a common epitope found in several other proteins. Objective: The purpose of this study was to further characterize Hev b 5 an d to identify linear IgE-binding epitopes. Methods: Octapeptides spanning the entire Hev b 5 protein were synthesized on a derivatized cellulose membrane, The membrane was reacted with sera poo led from health care workers allergic to latex or rabbits immunized with la tex proteins. B-cell epitopes were identified by subsequent incubations wit h the appropriate secondary antibodies and detected by using chemifluoresce nce. Results: Sera from patients allergic to latex recognized 6 IgE-binding regi ons located throughout the molecule. Two epitopes (2 and 4) had the common AA sequence of KTEEP. Epitopes 3 and 5 bad a similar AA sequence of EEXXA, where X was P, T, or K. Epitopes 1 and 6 appeared to be unrelated to the ot her epitopes, Database analysis could not identify other proteins with simi lar sequences. Neither of the XEEEX sequences bound IgE. Control sera faile d to react to any peptides. Conclusions: Hev b 5 exists as multiple isoforms, but only small amounts ar e present in the nonammoniated latex preparations, such as those used for d iagnostic tests, and this may help to explain the relatively poor sensitivi ty of some in vitro tests.