Gene gun immunization with clinically relevant allergens aggravates allergen induced pathology and is contraindicated for allergen immunotherapy

Abstract

Gene gun immunization has been associated with the induction of a heterologous type of immune response characterized by a T H1-like immune reaction on the cellular level, i.e. generation of IFN-γ secreting CD8 + T-cells, yet a T H2 biased serology as indicated by high IgG1:IgG2a ratios and induction of IgE. Nevertheless, gene gun immunization using the model molecule β-galactosidase has been argued to prevent IgE induction and to promote T H1 cells with respect to allergy DNA immunization. In our current study, we evaluated the potential of gene gun immunization to prevent type I allergic reactions comparing β-galactosidase with two clinically relevant allergens, and further investigated the effect of gene gun immunization on relevant lung parameters. BALB/c mice were immunized with plasmids encoding the birch pollen allergen Bet v 1, the grass pollen allergen Phl p 5, or the model molecule β-galactosidase, either by gene gun or intradermal injection followed by sensitization and intranasal provocation with the respective allergen. IgG1 and IgG2a antibody titers were determined by ELISA. IgE levels were evaluated in a rat basophil release assay. The severity of eosinophilia was determined in bronchoalveolar lavages, and the overall infiltrate was analyzed by histology on lung paraffin sections. Gene gun immunization induced a T H2-biased immune reaction, which did not prevent from production of IgE after subsequent sensitization. This T H2 effect was influenced by the nature of the antigen, with a more pronounced T H2-bias for the allergens Bet v 1 and Phl p 5 compared to β-galactosidase. Gene gun immunization with all three antigens promoted eosinophil influx into the lung and did not alleviate lung pathology after intranasal provocation. In contrast to needle injection of plasmid DNA, which triggers a clearly T H1-biased and allergy-preventing immune response, gene gun application fails to induce anti-allergic reactions with all tested antigens and is therefore contraindicated for allergen-specific immunotherapy.