Induction of IgE antibodies in mice with recombinant grass pollen antigens

In this study, recombinant Poa pratensis (Poa p) IX allergens were examined for their in vivo allergenicity and antigenicity. Immunization of mice with a fusion protein (FP) comprising beta-galactosidase and recombinant KBG8.3 (rKBG8.3) allergen induced high titres of both IgG and IgE antibodies. By contrast, immunization with rKBG60.2, which represents the N-terminal fragment of rKBG8.3, induced only IgG antibodies. The IgE antibody titre specific to Kentucky Bluegrass (KBG) was significantly higher than that to beta-galactosidase. Moreover, KBG-specific IgE antibodies showed no apparent decrease in their titres until 60 days after immunization, whereas the beta-galactosidase-specific IgE antibodies disappeared after 40 days. The antibodies induced with rKBG8.3 in mice were capable of inhibiting the binding of human IgE antibodies to KBG pollen allergens, which indicated that rKBG8.3-specific murine antibodies recognized epitopes similar to those recognized by human IgE antibodies. Analysis of allergenic cross-reactivities of rKBG8.3 with components from five other species of grass pollens revealed that IgE antibodies induced by this allergen are capable of binding in vivo to components from other grass pollens. These results suggest that the mouse may serve as a model for the manipulation of IgE responses to recombinant allergens or their chemically modified derivatives.