Rational design of a hypoallergenic Phl p 7 variant for immunotherapy of polcalcin-sensitized patients

• Main Authors: Marianne Raith, Doris Zach, Linda Sonnleitner, Konrad Woroszylo, Margarete Focke-Tejkl, Herbert Wank, Thorsten Graf, Annette Kuehn, Mariona Pascal, Rosa Maria Muñoz-Cano, Judith Wortmann, Philipp Aschauer, Walter Keller, Simone Braeuer, Walter Goessler, Ines Swoboda
• Format: Article
• Language: English
• Published: Nature Publishing Group 2019-05-01
• Series: Scientific Reports
• Online Access: https://doi.org/10.1038/s41598-019-44208-0

Abstract Polcalcins are important respiratory panallergens, whose IgE-binding capacity depends on the presence of calcium. Since specific immunotherapy is not yet available for the treatment of polcalcin-sensitized patients, we aimed to develop a molecule for efficient and safe immunotherapy. We generated a hypoallergenic variant of the grass pollen polcalcin Phl p 7 by introducing specific point mutations into the allergen’s calcium-binding regions. We thereby followed a mutation strategy that had previously resulted in a hypoallergenic mutant of a calcium-binding food allergen, the major fish allergen parvalbumin. Dot blot assays performed with sera from Phl p 7-sensitized patients showed a drastically reduced IgE reactivity of the Phl p 7 mutant in comparison to wildtype Phl p 7, and basophil activation assays indicated a significantly reduced allergenic activity. Rabbit IgG directed against mutant rPhl p 7 blocked patients’ IgE binding to wildtype Phl p 7, indicating the mutant’s potential applicability for immunotherapy. Mass spectrometry and circular dichroism experiments showed that the mutant had lost the calcium-binding capacity, but still represented a folded protein. In silico analyses revealed that the hypoallergenicity might be due to fewer negative charges on the molecule’s surface and an increased molecular flexibility. We thus generated a hypoallergenic Phl p 7 variant that could be used for immunotherapy of polcalcin-sensitized individuals.