Comparison of inflammatory responses to genetically engineered hypoallergenic derivatives of the major birch pollen allergen Bet v 1 and to recombinant Bet v 1 wild type in skin chamber fluids collected from birch pollen-allergic patients

Background: Nearly 60% of birth pollen-allergic patients react exclusively to Bet v 1, With use of the skin blister model, previously only established for installation of crude allergens, we have for the First time characteri zed the inflammatory response in vivo to recombinant birch pollen allergen, rBet v 1, molecules (rBet v 1 wild type, fragments and trimer), Objective: Our purpose was to examine whether challenge with rBet vl deriva tives (fragments and trimer) compared with rBet v 1 wild type differs with respect to influx of activated eosinophils and detectable levels of cytokin es/chemokines related to allergic inflammation in skin chambers applied to birch pollen-allergic patients. Methods: The skin blister chambers were filled for 2 hours with rBet v 1, t he derivatives or PBS and heparin (negative control), The fluids were analy zed after 2 and 8 hours. The number of eosinophils was determined and EG2 a nd CD69 expression measured by flow cytometry. Cytokines and mediators were analyzed by ELISA and RIA techniques. Results: Comparable numbers of eosinophils were recruited to the chambers c hallenged with rBet vl molecules, but the eosinophils from the rBet vl wild -type challenged chambers showed a significantly higher expression of CD69. The levels of eotaxin were similar in all 4 chambers, whereas rBet v 1 wil d type induced significantly higher levels of histamine, eosinophil cationi c protein, and GM-CSF than the derivatives did. Recombinant Bet v 1 trimer elicited significantly lower levels of IL-4 compared with rBet vl wild type . Conclusion: Genetically engineered hypoallergenic rBet v derivatives recrui ted eosinophils analogously with rBet v 1 wild type. However, the derivativ es exhibited a lower capacity to activate eosinophils and to release proinf lammatory mediators and T helper type 2-derived cytokines, The derivatives may therefore be candidate molecules for specific immunotherapy of birch po llen allergy with reduced risk of inducing allergenic or inflammatory side effects.