Induction of grass pollen allergen–specific IgG responses in rabbits by means of immunization with BM32, recombinant grass pollen allergens, and natural grass pollen AIT extracts. A, Scheme of rabbit immunizations. Rabbits were immunized with 3 monthly injections of BM32 or a mix of recombinant grass pollen allergens. In parallel, rabbits were immunized with registered grass pollen extract–based AIT vaccines (Allergovit, Alutard, Phostal, and Pollinex), as recommended by the manufacturer. Serum samples were collected from all rabbits shortly before the first immunization (Pre) and in monthly intervals (1.IS, 2.IS, 3.IS, and 4.IS). B, Comparisons and time courses of allergen-specific IgG responses of rabbits. Shown are mean OD values corresponding to allergen-specific IgG levels (y-axes) at different time points (x-axes). s.c, Subcutaneous.