Background: Latex-fruit cross-sensitization has been fully demonstrated. However, the antigens responsible for this "latex-fruit syndrome" have not been identified. We have recently shown that class I chitinases are relevant chestnut and avocado allergens.
Objective: We sought to evaluate the in vivo and in vitro reactions of purified chestnut and avocado chitinases in relation to the latex-fruit syndrome.
Methods: From a latex-allergic population, eighteen patients allergic to chestnut, avocado, or both were selected. Skin prick tests (SPTs) were performed with crude chestnut and avocado extracts, chitinase-enriched preparations, and purified class I and II chitinases from both fruits. CAP-inhibition assays with the crude extracts and purified proteins were carried out. Immunodetection with sera from patients with latex-fruit allergy and immunoblot inhibition tests with a latex extract were also performed. Eighteen subjects paired with our patients and 15 patients allergic to latex but not food were used as control groups.
Results: The chestnut class I chitinase elicited positive SPT responses in 13 of 18 patients with latex-fruit allergy (72%), and the avocado class I chitinase elicited positive responses in 12 of 18 (67%) similarly allergic patients. By contrast, class II enzymes without a hevein-like domain did not show SPT responses in the same patient group. Each isolated class I chitinase reached inhibition values higher than 85% in CAP inhibition assays against the corresponding food extract in solid phase. Immunodetection of the crude extracts and the purified class I chitinases revealed a single 32-kd band for both chestnut and avocado. Preincubation with a natural latex extract fully inhibited the IgE binding to the crude extracts, as well as to the purified chestnut and avocado class I chitinases.
Conclusion: Chestnut and avocado class I chitinases with an N-terminal hevein-like domain are major allergens that cross-react with latex. Therefore they are probably the panallergens responsible for the latex-fruit syndrome.