Specific immunotherapy with pollen extract bears risks which may be overcome by using alternative strategies such as DNA vaccination.

BALB/c mice were immunized intradermally with a Phl p 5b-DNA-construct or the respective vector controls before subsequent intraperitoneal inoculations with recombinant Phl p 5b. Sera were analyzed to quantify Phl p 5b specific IgE, IgG₁ and IgG_2a immunoglobulin titers. After intranasal challenge with Phl p 5b lung sections were stained with periodic acid-Schiff (PAS) and Giemsa to rate airway inflammation as represented by goblet cell hyperplasia, peribronchial inflammation, eosinophilia and mucus production.

Pretreating the mice with Phl p 5b-DNA-construct or vector significantly inhibited the production of Phl p 5b specific IgE and Ig_G1 antibodies (p<0.01). The Phl p 5b-DNA-construct completely protected the animals from developing a lung pathology associated with inflammation and resembling the histopathology of chronic bronchitis whereas the vector alone gave only partial protection.

DNA vaccination inhibits the production of Th2-associated Phl p 5b specific IgE and IgG₁. This correlates with a protection of the mice against developing pathologic alterations in the lung after intranasal provocation. Partial protection was also obtained with the vector alone, implicating the involvement of CpG immunostimulatory motifs in the observed effects besides the specific effects of the Phl p 5b-DNA-construct.