Abstract
B-cell maturation antigen (BCMA) fused at the C-terminus to the Fc portion of human IgG1 (BCMA-Fc) blocks B-cell activating factor (BAFF) and proliferation-inducing ligand (APRIL)-mediated B-cell activation, leading to immune disorders. The fusion protein has been cloned and produced by several engineering cell lines. To reduce cost and enhance production, we attempted to express recombinant human BCMA-Fc (rhBCMA-Fc) in Pichia pastoris under the control of the AOX1 methanol-inducible promoter. To produce the target protein with uniform molecular weight and reduced immunogenicity, we mutated two predicted N-linked glycosylation sites. The secretory yield was improved by codon optimization of the target gene sequence. After fed-batch fermentation under optimized conditions, the highest yield (207 mg/L) of rhBCMA-Fc was obtained with high productivity (3.45 mg/L/h). The purified functional rhBCMA-Fc possessed high-binding affinity to APRIL and dose-dependent inhibition of APRIL-induced proliferative activity in vitro through three-step purification. Thus, this yeast-derived expression method could be a low-cost and effective alternative to the production of rhBCMA-Fc in mammalian cell lines.