Isolation and characterization of major banana allergens: identification as fruit class I chitinases

Background Banana allergy has been associated with the latex-fruit syndrome . Several IgE-binding components, the relevant ones being proteins of 30-37 -kDa, have been detected in banana fruit, but none of them have been isolat ed and characterized yet. Objective To purify and characterize the 30-37 lkDa banana allergens. Methods Fifteen patients allergic to banana were selected on the grounds of a latex-allergic population. Prick by prick tests to this fruit were perfo rmed. Total and specific IgE to banana were determined. Banana allergens we re isolated by affinity chromatography, followed by cation-exchange chromat ography. Their characterization includes N-terminal sequencing, enzymatic a ctivity assays, immunodetection with sera from allergic patients and with a ntichitinase antibodies, and CAP and immunoblot inhibition tests. Skin pric k tests with banana extracts and with the purified allergens were also carr ied out. Results Two major IgE-binding proteins of 34 and 32 kDa, also recognized by polyclonal antibodies against chestnut chitinases, were immunodetected in crude banana extracts. Purification and characterization of both proteins h ave allowed their identification as class I chitinases with an hevein-like domain. Each isolated allergen reached inhibition values higher than 90% in CAP inhibition assays, and fully inhibited the IgE-binding by the crude ba nana extract when tested by an immunoblot inhibition method. The two purifi ed allergens provoked positive skin prick test responses in more than 50% o f the banana-allergic patients. Conclusions Class I chitinases with an hevein-like domain are major allerge ns in banana fruit. Their presence in other fruits and nuts, such as avocad o and chestnut, could explain the cross-sensitization among these foods.