Hypoallergenic Variants of the Parietaria judaica Major Allergen Par j 1: A Member of the Non-Specific Lipid Transfer Protein Plant Family

Abstract

Background: Par j 1 represents a major allergenic component of Parietaria judaica (Pj) pollen, since it is able to induce an immunoglobulin E (IgE) response in 95% of Pj-allergic patients. It belongs to the non-specific lipid transfer protein family, sharing with them a common three-dimensional structure. Methods: Disulphide bond variants of the recombinant Par j 1 (rPar j 1) allergen were generated by site-directed mutagenesis, and the immunological activity of rPar j 1 and its conformational mutants was compared with the use of the skin prick test (SPT). The ability to bind IgE antibodies was evaluated by Western blot, ELISA and ELISA inhibition. T cell reactivity was measured by peripheral blood mononuclear cell proliferation assay. Results: The disruption of Cys14–Cys29 and Cys30–Cys75 bridging (PjA mutant) caused the loss of the majority of specific IgE-binding activity. Additional disruption of the Cys4–Cys52 bridge (PjC mutant) and the latter Cys50–Cys91 bridge (PjD mutant) led to the abolition of IgE-binding activity. On the SPT, PjB (lacking the Cys4–Cys52 and Cys50–Cys91 bridges) was still capable of triggering a type I hypersensitive reaction in 9 out of 10 patients, and PjA in 3 out of 10 patients, while PjC and PjD did not show any SPT reactivity. All the mutants preserved their T cell reactivity. Conclusion: Recombinant hypoallergenic variants of the rPar j 1 allergen described herein may represent a useful tool for improved immunotherapy.