An allergen-independent therapeutic vaccine has been developed to reduce levels of IgE. The aim of this study was to characterize the immune response raised upon anti-IgE vaccination of rats.

The active vaccine component is a chimeric protein consisting of the constant domain 3 from rat IgE (Ce3) flanked by Ce2 and Ce4 domains from the American opossum. Wistar F rats were immunised subcutaneously at weeks 0, 3, 5 and 7 with vaccine adsorbed onto aluminum hydroxide or emulsified in the oil-based adjuvant Montanide ISA 51. The anti-IgE response and serum IgE concentrations were measured. The effect of concurrent ovalbumin (OVA) sensitization on IgE levels was also investigated. Furthermore, we evaluated potential crosslinking activity by anti-IgE from a number of rats on IgE bound to a mast cell line.

The vaccine induced a pronounced anti-IgE response and reduced IgE levels with more than 90% upon administration with aluminum hydroxide or Montanide ISA 51. The vaccine also prevents increased levels of serum IgE by OVA. No sign of crosslinking activity by anti-IgE on receptor-bound IgE could be detected.

The present study demonstrates that the vaccine generates high anti-IgE titres and strongly reduced IgE levels also with an aluminum-based adjuvant. Moreover, this immune response does not crosslink receptor-bound IgE. Thus, the present study supports the concept of therapeutic IgE vaccination.