An Innovative Immunotoxin Design Against Allergy Based on the IL-33 Cytokine and the Ribotoxin α-Sarcin

Allergies constitute one of the major health problems worldwide, increasing their prevalence in developed countries. To overcome this multifactorial disease, immunotherapy and the use of immune molecules, such as immunotoxins, have arisen as promising therapeutic tools. We have designed, produced, and characterized a new immunotoxin called IL-33αS, encompassing the murine IL-33 (mIL-33) as the target domain and the ribotoxin α-sarcin as the toxic domain. IL-33 is a widely described alarmin that binds to the ST2 receptor of a variety of immune cells, including ILC2s, leading to Th2-derived inflammatory response, as occurs in allergic reactions. Both IL-33αS and mIL-33 were successfully produced in the methylotrophic yeast <i>Pichia pastoris</i> and purified to homogeneity through affinity chromatography for their characterization. Both IL-33αS and mIL-33 were able to specifically bind to ST2⁺ Raw 264.7 cells, and IL-33αS kept the ribonucleolytic activity of α-sarcin, allowing IL-33αS to exhibit cytotoxic effects against ST2⁺-targeted cells. In addition, IL-33αS induced significantly less secretion of the Th2-linked cytokine IL-13 in comparison to mIL-33, suggesting steric interference produced by the presence of the α-sarcin. These results assess the potential therapeutic effect of this new immunotoxin against allergies, causing ST2-targeted cytotoxicity while avoiding the Th2 cytokine secretion.