Class I Chitinases and the Latex-Fruit Syndrome

The prevalence of sensitization to natural rubber latex in the general population is around 1%. However, occupational latex allergy is considerably higher in people who work wearing latex gloves. Furthermore, almost 50% of these allergic patients also show hypersensitivity to some plant foods, especially chestnut, banana, and avocado, but also to kiwi, papaya, tomato and others. The name "latexfruit syndrome" has been proposed to describe this type of cross-reactivity. We review here the role of class I chitinases of chestnut, avocado and banana, as major allergens implicated in the latex-fruit syndrome. These enzymes have an N-terminal domain homologous to hevein, one of the major allergens of latex. Thus, there should be common IgE-binding epitopes in latex hevein and the hevein-like domain of class I chitinases. Homologous class II enzymes lacking the hevein domain are not reactive either in vitro or in vivo. This type of protein is widely distributed in plants and it has been demonstrated that in many other foods, like fruits and legumes, there are also IgE-binding class I chitinases. We propose them as panallergens responsible for the latex-fruit syndrome. They are inactivated by heat treatment, which probably explains why only fresh consumed foods are associated with the syndrome. The amount of these allergens may vary dramatically because class I chitinases are induced by ethylene. This plant hormone acts during the ripening of climacteric fruits and is commercially used to hasten ripening of fruits and vegetables. The increase in the allergenicity of these fruits due to ethylene treatment could explain in part the rise in the prevalence of latex-fruit allergy. (Internet Symposium on Food Allergens 2000, 2(3):137-144) class I chitinases fruit panallergens latex-fruit syndrome latex allergy ethylene induction allergen heat inactivation