Use of Pichia pastoris for Production of Recombinant Cytokines

An understanding of the structure and function of cytokines requires the availability of milligram to gram amounts of highly purified and biologically active cytokines. A variety of expression systems have been used to produce recombinant proteins, including Escherichia coli , Pichia pastoris , baculovirus, and poxvirus systems. The P . pastoris expression system is particularly well suited for the production of recombinant cytokines. The relative merits of the P. pastoris expression system compared with others have been reviewed elsewhere (1 –3 ). In summary, P. pastoris offers the potential for high yields of biologically active recombinant cytokines at relatively low production costs. In contrast to E. coli , with which folding problems often lead to inclusion body formation, the expressed proteins are properly folded and can be secreted into the media. In addition, unlike bacterial systems, P. pastoris is capable of high-mannose type N-linked glycosylation (without the hyperglycosylation problems of Saccharomyces cerevisiae ) (4 ,5 ). Another reason for choosing P. pastoris over bacterial expression systems is that the yeast cells are not a source of endogenous endotoxin, as is the case with E. coli . This is particularly important for recombinant cytokines: contaminating endotoxin could stimulate cells to produce inflammatory cytokines.