Improving the Expression of a Soluble Receptor:Fc fusion Protein in CHO Cells by Coexpression with the Receptor Ligand

Abstract

A novel soluble receptor:Fc fusion protein was designed as a recombinant therapeutic targeting human IL-13, a central mediator of asthma. This protein, sIL-13R, was expressed in stable CHO cell lines for the purpose of producing sufficient amounts of material to support early clinical trials. However, expression levels of sIL-13R were poor, and the protein was prone to misfolding and aggregation. Culturing the recombinant CHO cell lines at reduced temperatures significantly enhanced expression levels and lowered the levels of aggregated material. An even more dramatic improvement was observed when sIL-13R was coexpressed with its natural ligand, IL-13, in CHO cells. Protein expression was enhanced at both 37{\textdegree}C and 31{\textdegree}C, and product aggregation was significantly reduced. The sIL-13R protein secreted by the coexpressing cell line adopted a conformation that remained stable even after removal of the ligand during purification. Together, these results suggest a possible strategy for improving the expression of other difficult to express soluble proteins.