A hybrid expressing genetically engineered major allergens of the Parietaria pollen as a tool for specific allergy vaccination.

Background: Allergy is an immunological disorder affecting about 25% of the population living in the industrialized countries. Specific immunotherapy is the only treatment with a long-lasting relief of allergic symptoms and able to reduce the risk of developing new allergic sensitizations and inhibiting the development of clinical asthma in children treated for allergic rhinitis.
Methods: By means of DNA recombinant technology, we were able to design a head to tail dimer expressing disulphide bond variants of the major allergen of the Parietaria pollen. IgE binding activity was studied by Western blot, ELISA inhibition assays and the skin prick test. T cell recognition was studied by peripheral blood mononuclear cell proliferation. The immunogenicity of the hybrid was studied in a mouse model of sensitization.
Results: In vitro and in vivo analysis showed that the disruption of specific cysteine residues in both allergens caused a strong reduction in IgE binding activity of the PjEDcys hybrid. In addition,we were able to show that a reduction in the IgE epitope content profoundly reduced the anaphylactic activity of the hybrid (from 100 to 1,000 times less than wild-type allergens) without interfering with the T cell recognition. Sera from BALB/c mice immunized with the hybrid were able to bind the natural Parietaria allergens and to inhibit the binding of human IgE to wild-type Par j 1 and Par j 2 allergens up to 90%.
Conclusion: Our results demonstrate that hybrid-expressing disulphide bond variants of the major allergens of the Parietaria pollen displayed reduced allergenicity and maintained T cell reactivity for induction of protective antibodies.