Transient transfection of CHO cells using linear polyethylenimine is a simple and effective means of producing rainbow trout recombinant IFN-γ protein.

A practical method was developed for the transient transfection of Chinese hamster ovary (CHO) cells with 25 kDa linear polyethylenimine (PEI) then optimal culture conditions determined for the production of rainbow trout (Oncorhynchus mykiss) IFN-γ recombinant protein. We found that culture temperature had a significant impact upon recombinant protein yield, with best results being obtained at 32 °C. However the amount of serum added to the culture medium had no effect upon recombinant IFN-γ (rIFN-γ) production. In this study maximal rIFN-γ yields and minimal PEI toxicity were achieved using a DNA/PEI ratio of 1:8, where the amount of PEI did not exceed 10 µg per 5 ml of RPMI1640 culture medium, with cells subsequently cultured at 32 °C for 7 days. Thus, linear PEI is a technically simple and cost-efficient method for the transient transfection of CHO cells and is compatible with serum-free operations.