Humoral immune responses to recombinant tree pollen allergens (Bet v I and Bet v II) in mice: construction of a live oral allergy vaccine.

Recombinant tree pollen allergens (recombinant Bet v I and recombinant birch profilin, Bet v II) were purified and used to immunize BALB/c and B6D2F1 mice with Al(OH)3 to elicit a specific IgE response. Serum from immunized mice was then used to detect immunoblotted natural tree pollen allergens. The onset of the humoral immune response was monitored using antimouse IgE, IgG1, IgG2a/b, IgG3 and IgA. In both strains, a specific and long-lasting IgE response could be elicited with both recombinant allergens. Mice immunized continuously with recombinant Bet v I + Al(OH)3 showed a significant decrease of specific IgE antibodies indicating that continuous application of allergens can reduce specific IgE responses. The possibility of inducing a different type of immune responses is indicated by the fact that mice fed with Bet v I expressed in apathogenic Salmonella strains showed a Th1 immune response to Bet v I accompanied by specific IgG2a/b without detectable IgG1 or IgE. Recombinant allergens can hence be used to decrease or even modulate specific IgE responses in vivo.