Immunological characterization and engineering of the major latex allergen, hevein (Hev b 6.02)

Abstract

Piia Karisola tutki luonnonkumiallergiaa välittömän (tyyppi I) allergian mallina. Hän keskittyi työssään luonnonkumiallergian pääallergeeniin, heveiiniin (Hev b 6.02), jota vastaan 70 %:lla luonnonkumiallergisista potilaista on IgE-luokan vasta-aineita. Vuorovaikutus näiden vasta-aineiden ja heveiinin välillä aiheuttaa erilaisia kliinisiä oireita, kuten ihottuma, allergista nuhaa, nokkosrokkoa ja jopa anafylaksiaa. Joskus nämä IgE-luokan vasta-aineet tunnistavat ”vahingossa” samankaltaisia valkuaisaineita eri kasveista. Noin puolet luonnonkumiallergiaa sairastavista potilaista saakin oireita syötyään trooppisia hedelmiä, jota kutsutaan luonnonkumi-hedelmä -oireyhtymäksi.Karisolan väitöskirjan tulokset antavat lisätietoa allergian perusmekanismeista. Niiden perusteella on jo suunniteltu ja tuotettu sarja uudenlaisia siedätyshoitoihin tarkoitettuja molekyylejä, joiden tehoa arvioidaan ja testataan luonnonkumiallergiaa varten kehitetyssä hiirimallissa.

In IgE-mediated natural rubber latex (NRL) allergy, hevein (Hev b 6.02) is a major allergen, which is recognized by 70% of latex allergic patients. Hevein, which is extraordinarily stable, has an antifungal function in the rubber tree (Hevea brasiliensis). Homologous proteins with conserved hevein-like domains (HLD) are found in several plants and some of them are believed to participate in allergic cross-reactions in patients who suffer from so-called latex-fruit syndrome.In this study, NRL allergy and hevein were used as a model pair to clarify the molecular mechanisms of an allergic reaction. In order to detect the conformational IgE-binding areas of hevein, parts of hevein and an immunologically non-reactive antimicrobial protein (AMP) of the amaranth (Amaranthus caudatus) were genetically combined using the evolutionary approach, which is based on the comparison of structural relatives. In addition, the potential IgE-binding amino acids were scanned with the guidance of sequential relatives and a total of 29 site-specific single-mutants of hevein were produced. Immunological tests with the sera from NRL-allergic patients identified six of the most important substitutions, and on the basis of this information three pilot molecules for immunotherapy in NRL allergy were constructed. Studies on the molecular reasons behind the IgE-cross-reactivity that exists between different HLDs in fresh fruits showed directly, for the first time, that isolated hevein (4.3 kDa) and homologous HLDs themselves, instead of whole endochitinases (31 kDa), are responsible of this allergic cross-reactivity.