Biosensor‐based characterisation of a single chain variable fragment with specificity to IgE as a candidate molecule for the therapy of IgE‐mediated diseases

Abstract

Aim of our project is the development of an adsorber based on mAb12, a murine monoclonal anti-IgE antibody, for the selective depletion of IgE by immunoadsorption to treat patients with severe manifestations of type I allergy. As the serum concentration of IgE (100ng/ml) is very low (100.000fold lower than IgG), adsorption of IgE requires rapid binding with high stability and affinity. MAb12, ScFv12 (a mAb12-derived non-anaphylactic single chain variable fragment) and recombinant α-chain of the human high-affinity IgE-receptor, FcεRI, were immobilised on a BIACore C1 chip. Monoclonal human IgE was injected to determine affinities and rate constants. To investigate the impact of mAb12 and ScFv12 on the interaction of IgE with FcεRI, sequential injection of IgE and mAb12 or ScFv12 as well as injection after preincubation of IgE with mAb12 or ScFv12 into the cell containing immobilised α-chain were carried out. 1 IgE associates with mAb12, ScFv12 and α-chain with equally high affinities. Both mAb12 and ScFv12 stably bind to α-chain-bound IgE without actively detaching it from the receptor and either molecule prevents binding of IgE to immobilised α-chain almost completely. Due to its highly affine and stable interaction with human IgE, we consider ScFv12 a candidate for the construction of an adsorber for the specific extracorporeal depletion of IgE. Supported by grant F1815 of the Austrian Science Fund (FWF). 1