Genetically engineered hybrid proteins from Parietaria judaica pollen for allergen-specific immunotherapy

Abstract

Despite the use of conventional allergen-specific immunotherapy in clinical practice, more defined, efficient, and safer allergy vaccines are required. The aim of the study was to obtain hypoallergenic molecules by deleting B-cell epitopes, which could potentially be applied to Parietaria judaica pollen allergy treatment. Three hybrid molecules (Q1, Q2, and Q3) derived from fragments of the 2 major P judaica pollen allergens, Par j 1 and Par j 2, were engineered by means of PCR. Hybrid structures were compared with their natural components by means of circular dichroism, and their biologic activities were compared by using T-cell proliferation assays. Their IgE-binding activity was determined with Western blotting, skin prick tests, and enzyme allergosorbent and ELISA inhibition tests. The hybrid proteins, especially Q2 and Q3, revealed significantly reduced IgE reactivity compared with the natural allergens, as well as with the whole P judaica extract. Furthermore, in vivo skin prick tests showed that the hybrid proteins had a significantly lower potency to induce cutaneous reactions than the whole P judaica extract. Two (Q1 and Q2) of the 3 hybrid proteins induced a comparable T-cell proliferation response as that produced by the whole extract and natural allergens. Considering its reduced anaphylactogenic potential, together with its conserved T-cell reactivity, the engineered Q2 protein could be used in safe and shortened schedules of allergen-specific immunotherapy against P judaica pollen allergy. Recombinant hybrid Q2 is able to induce T-cell proliferation, thus evidencing a potential therapeutic effect. Its reduced IgE-binding capacity envisages an excellent safety profile.