INDUCTION OF IGE ANTIBODIES IN MICE AND RHESUS-MONKEYS WITH RECOMBINANT BIRCH POLLEN ALLERGENS - DIFFERENT ALLERGENICITY OF BET-V-1 AND BET-V-2

Background: Serologic measurements with recombinant birch pollen aller gens, rBet nu 1 and rBet nu 2 (birch profilin), have shown that more t han 95% of patients allergic to tree pollen mount high levels of IgE a gainst rBet nu 1, whereas only approximately 10% of the patients displ ay rather low levels of IgE against rBet nu 2. Objective: In this stud y an attempt was made to determine whether the different allergenicity of the major birch pollen allergen, rBet nu 1, and a minor birch poll en allergen, rBet nu 2, might be related to a different immunogenicity of the proteins as evaluated in experimental animal systems (mice and rhesus monkeys). Methods: Purified recombinant allergens were injecte d into mice and rhesus monkeys with aluminum hydroxide as adjuvant for elicitation of specific IgE responses. Antibody responses to the alle rgens were detected by immunoblotting, and time courses of immune resp onses were measured by ELISA. Results: In both animal models more than the 10-fold dose of rBet nu 2 was required to induce IgE antibodies, and even then, the amount of specific IgE antibodies elicited with rBe t nu 1 was substantially higher than that induced by rBet nu 2. It was noted that rBet nu 2 formed stable polymers through disulfide bonds. Conclusion: In two different animal models (mice and rhesus monkeys) t he major birch pollen allergen rBet nu 1, induced substantially higher levels of IgE than rBet nu 2. A reduced allergenicity of Bet nu 2 cau sed by polymer formation would be in agreement with previous studies i ndicating reduced allergenicity of proteins on chemical polymerization .