Introducing a New Method for Purification of Human IL-4 by Substitution of a Single Amino Acid in IL-4 Protein Sequence

It is advantageous to develop an effective purification procedure to produce recombinant protein drugs (rPDs) without any tags. To remove N- or C-terminus tags from the rPDs, several cleavage site-based endopeptidases were used. Separating the endopeptidase enzyme from the rPDs is a time-consuming and costly process. To design and develop a new method for the purification of human interleukin (IL)-4 with potential application for other cytokines. Met-like amino acids were substituted at position 120 to reduce the possibility of alteration in the structure of IL-4 and its biological activity. Based on the in silico analysis, isoleucine was chosen as an alternative amino acid, and the M120I mutant IL-4 (mIL-4) model was selected for the downstream analysis. Recombinant mIL-4 was produced in the E.coli BL21 host and purified with CNBr. Then in vitro evaluations of the native and mutant IL-4 were performed. The results showed that both the native and mutant IL-4 had the same effect on TF-1 cell proliferation. On the other hand, there was no significant difference between the effects of native IL-4 (nIL-4) and mIL-4 on the expression of IL-4 and IL-10 in activated peripheral blood mononuclear cells. Native and mutant IL-4 have similar biological activities. Here, an efficient and straightforward system is introduced to purify IL-4 cytokine using CNBr, which could be applied to other rPDs.