Is Pichia pastoris a realistic platform for industrial production of recombinant human interferon gamma?

Human interferon gamma (hIFN gamma) is an important cytokine in the innate and adaptive immune system, produced commercially in Escherichia coli. Efficient expression of hIFN gamma has been reported once for Pichia pastoris (Wang et al., 2014) - a proven heterologous expression system. This study investigated hIFN gamma expression in P. pastoris replicating the previous study and expanding by using four different strains (X33: wild type; GS115: HIS(-)Mut(+); KM71H: Arg(+), Mut-and CBS7435: Mut(S)) and three different vectors (pPICZ alpha A, pPIC9 and pPpT4 alpha S). In addition, the native sequence (NS) and two codon-optimised sequences (COSI and COS2) for P. pastoris were used. Methanol induction yielded no expression/secretion of hIFN gamma in X33, highest levels were recorded for CBS7435: Mut(S) (similar to 16 mu g. L-1). mRNA copy number calculations acquired from RT-qPCR for GS115-pPIC9-COS1 proved low abundance of mRNA. A 10-fold increase in expression of hIFN gamma was achieved by lowering the minimal free energy of the mRNA and 100-fold by Mut(S) phenotypes, substantially lower than reported by Wang et al. (2014). We conclude that commercial production of low cost, eukaryotic recombinant hIFN gamma is not an economically viable in P. pastoris. Further research is required to unravel the cause of low expression in P. pastoris to achieve economic viability. (C) 2016 International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved