Example 8
The expression and purification of a recombinant antibody protein were conducted by following methods: HEK293E cells cultured in Freestyle 293 Expression Medium with 10% of Pluronic F-68 (Gibco) at 1×106 cell/ml were transfected with equal amount of heavy chain vector and light chain vector DNA at final concentration of 0.5 μg/ml and PEI (Polyethylenimine-linear, Polyscience) at 1.0 μg/ml. DNA to PEI ratio was 1:2. DNA and PEI complexes formed period with Optimal MEM should be 15 minutes at the room temperature. Transfected cells were cultured in the flasks with 5% CO2, 37° C. and 125 rpm shaking speed. 1% Peptone medium was added at 22 to 26 hours post transfection. Conditioned medium was harvested on day 6 and supernatant was centrifuged at 3,000 rpm for 30 minutes. The clarified conditioned medium were then loaded onto nProteinA column (G.E. Healthcare), washed with PBS plus 0.1% triton-X100 and finally the bound IgG was eluted with a solution containing 0.1M glycine at pH 3.5. The eluted antibody protein was dialyzed to PBS and stored at −80*C. To remove endotoxin, the purified protein was further processed by passing through Hitrap DEAE Sepharose F.F. column and the resulting antibody was analyzed to determine the level of purity using size exclusion chromatography (Superdex 200 5/150 GL, G.E. Healthcare).