D1.222 - Production of Bet v 1-specific IgG antibodies in mice immunized with the recombinant vaccine ABP-Vax

Recently, vaccine ABP-Vax against birch pollen allergy, containing recombinant hypoallergenic polyprotein AB-PreS absorbed on aluminum hydroxide was developed. AB-PreS represent fusion protein carrying peptides derived from Bet v 1 and Mal d 1 allergens fused with HBV surface protein PreS. Previously, we have established that 1 month after 5 monthly immunizations with ABP-Vax in a total dose 80 µg induced protective IgG against Bet v 1 and Mal d 1. The present study aims to investigate the long‑term dynamics of Bet v 1‑specific IgG in mice that have been immunized with ABP‑Vax.

The mice were immunized subcutaneously with 80 μg of AB-PreS absorbed on 0.25 ml of a 1.3% aluminum adjuvant solution. Mice were given 5 or 3 monthly subcutaneous immunizations in a dose 80 μg (5x80 and 3x80 groups) with the vaccine. Control group was immunized with PBS (Int group). 9 months after the immunotherapy mice received a boost injection. The levels of Bet v 1-specific IgG and IgG2a antibodies were estimated via ELISA from 1^st to the 10^th month after final immunization.

The levels of Bet v 1‑specific IgG and IgG2a (Fig. 1) were significantly elevated in mice that received 5 immunizations, compared to those that received only 3 monthly treatments. In both groups, Bet v 1‑specific IgG levels (Fig. 1A) peaked from month 1 to 3 after the final injection. Subsequently, over the following 6 months (up to 9^th month), a gradual decline in antibody levels was observed. A booster injection effectively restored IgG level to their maximum within 1 month. Throughout the observation period (from 1^st to 9^th month post‑final immunization), both experimental groups maintained an elevated level of IgG2a without gradual decline(Fig. 1B). A booster dose substantially increased neutralizing IgG2a production by 1.96 and 2.63 times in the groups 3x80 and 5x80, respectively, comparing to the 9^th month.

The recombinant vaccine ABP‑Vax, administered at a dose of 80 µg, induced more stronger IgG and IgG2a response in 5x80 compared to 3x80 group. Allergen‑specific IgG levels reached their peak within the first 3 months after the final dose, and then gradually decreased over the next 6 months. In contrast, IgG2a levels remained elevated throughout the entire 9‑month observation period without decline. A single booster injection of ABP‑Vax, administered 9 months after the completion of the AIT course, led to a significant increase in both IgG and IgG2a antibody levels.