Class I chitinases as potential panallergens involved in the latex-fruit syndrome

Background: Latex-fruit cross-sensitization has been fully demonstrated, Ho wever, the antigens responsible for this "latex-fruit syndrome" have not be en 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 puri fied chestnut and avocado chitinases in relation to the latex-fruit syndrom e. Methods: From a latex-allergic population, eighteen patients allergic to ch estnut, avocado, or both were selected. Skin prick tests (SPTs) were perfor med with crude chestnut and avocado extracts, chitinase-enriched preparatio ns, and purified class I and II chitinases from both fruits. CAP-inhibition assays with the crude extracts and purified proteins were carried out. Imm unodetection with sera from patients with latex-fruit allergy and immunoblo t inhibition tests with a latex extract were also performed. Eighteen subje cts paired with our patients and 15 patients allergic to latex but not food mere 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 c hitinase elicited positive responses in 12 of 18 (67%) similarly allergic p atients. By contrast, class II enzymes without a hevein-like domain did not show SPT responses in the same patient group. Each isolated class I chitin ase reached inhibition values higher than 85% in CAP inhibition assays agai nst the corresponding food extract in solid phase, Immunodetection of the c rude extracts and the purified class I chitinases revealed a single 32-kd b and for both chestnut and avocado. Preincubation with a natural latex extra ct 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 heve in-like domain are major allergens that crossreact with latex, Therefore th ey are probably the panallergens responsible for the latex-fruit syndrome.