Identification and characterization of cross-reactive natural rubber latexand Ficus benjamina allergens

Background: An association between allergy to Ficus benjamina and natural r ubber latex (NRL) has been suspected based on clinical and immunological ob servations. The responsible cross-reactive allergens have not been identifi ed yet. This study was undertaken to investigate the cross-reactivity betwe en hevein (Hev b 6.02, 4.7 kD), a major allergen of NRL, and F. benjamina a nd identify its counterpart in F. benjamina. Methods: 89 serum samples from subjects allergic to NRL were used in the study. Skin prick tests were per formed with highly purified hevein and sap extract of F. benjamina. Specifi c IgE antibodies to NRL, F. benjamina and Hev b 6.02 were determined by the Pharmacia CAP method. Cross-reactivity among these allergens was investiga ted by means of CAP and immunoblot inhibition experiments. Two-dimensional gel electrophoresis separation and protein microsequencing were performed t o identify the crossreactive allergens in F. benjamina. Results: 67 out of 89 (75%) sera showed elevated IgE to hevein. Specific IgE to Ficus were fou nd in 22 (24.7%) sera, and with 1 exception, all these sera also had IgE to Hev b 6.02. Results of CAP inhibition assays using 11 sera showing IgE to both Hev b 6.02 and Ficus demonstrated that the IgE to Ficus could be compl etely inhibited by Hev b 6.02 in 6 of 11 sera. Immunoblots and immunoblot i nhibition assays revealed that a protein of about 45 kD in F. benjamina is strongly recognized by serum IgE. In addition, the IgE-binding reactivity t o this 45-kD protein could be completely inhibited by preincubation of the sera with Hev b 6.02. N-terminal protein sequencing of 14 amino acids indic ated that this 45-kD protein has a hevein-like domain at the N-terminal reg ion and may belong to the endochitinase family. Conclusion: Latex-allergic patients are at higher risk of becoming sensitized to Ficus. Hev b 6.02 in latex is a major cross-reactive allergen and its counterpart in F. benjamin a is an acidic protein with a molecular weight of about 45 kD and a hevein- like N-terminal domain. Copyright (C) 2000 S. Karger AG, Basel.