Process development for the control of solubility of Affibody® molecules

Abstract: In this study the aim was to optimize the production of the Affibody fusion-protein Z03358- ABD094-(S4G)3-IL2 with regard to the amount of soluble protein produced. However, problems with reproducibility with this protein and the chosen expression system were encountered. Therefore, expression of the His-tagged Affibody His6-(Z05477)2 was evaluated using the same expression system as well as expression in another well characterized expression system. Both target proteins are of therapeutic interest. One of the proteins is an IL2 fusion protein (Z03358-ABD094-(S4G)3-IL2) that bind the platelet-derived growth factor receptor β (PDGFR-β). PDGF signaling is of interest in cancer treatment where, among other things, the effects of PDGF on tumor angiogenesis is researched. The His6-(Z05477)2 protein has a classified target but is developed as a therapeutic in the area of inflammation and autoimmune disease. Both model proteins are known to be difficult to purify due to low solubility. The two E. coli expression systems investigated and compared were BL21(DE3) and Lemo21(DE3). The fusion protein Z03358-ABD094-(S4G)3-IL2 was produced in BL21(DE3) in inclusion bodies with a yield of 4.95 g/l. An optimized process for the expression of His6-(Z05477)2 using BL21(DE3) was developed with a yield of 6.6 g/l soluble protein after expression at 30°C for 6 h.