Fine characterization of immunological mechanisms mediated by the major allergens of Parietaria judaica and by a hypoallergenic hybrid, rPjEDcys.

Allergy is a hypersensitivity disease IgE-mediated, affecting more than 25% of the population. Actually the only curative treatment of allergies is Allergen-Specific Immunotherapy (SIT). Recombinant hypoallergenic allergen derivatives with reduced allergenic activity have been engineered to reduce side effects during SIT. Parietaria judaica (Pj) pollen contains two major allergens, Par j 1 and expressing disulphide bond variants of Par j 1 and Par j 2, was generated. The aim of this research project is to compare the immunological mechanisms activated by the major allergens of Pj and by rPjEDcys. In vitro analysis suggested that rPjEDcys has a reduced allergenity and maintains T cells reactivity. In particular we showed that PBMC of Pj allergic patients stimulated in vitro with the hybrid and the wild-type recombinant allergens scored a percentage of proliferating CD4+ and CD56+ cells higher than unstimulated samples. Furthermore, cytokine secretion assays on CD4+ cells demonstrated that rPjEDcys reduces the secretion of two Th2 cytokines that are critical in the development of allergy such as IL-5 and IL-13. Furthermore we observed the selection of a putative pTreg cell subset (defined as CD4+ CD25++ CD127-) in both the w.t. mixture and the rPjEDcys. We characterized these cells at molecular level by REAL-TIME PCR. Moreover, we addressed the kinetic of functional surface marker expression, such as GARP (Glycoprotein A Repetitions Predominant), LAP (Latency-Associated Peptide) and CD39 on CD4+ cells. Our analyses demonstrated that rPjEDcys induces a number of GARP-LAP-CD39 co-expressing cells higher than wild-type recombinant allergens. These results suggest that rPjEDcys represents a useful approach for immunotherapy of allergic disease.