Materials for virial inactivation
The IgG4-N1 used in this study was a proprietary engineered mAb from Bristol-Myers Squibb Company. The IgG4-N1 was produced from a Chinese hamster ovary (CHO) cell culture process in XDR-500 bioreactors (Xcellerex, Inc., Marlborough, MA), harvested by depth filtration, sterilized by 0.2 µm membrane filtration, and purified by Protein A affinity chromatography. The IgG4-N1 was eluted from Protein A with PAE materials in the buffer condition of 25 mM Glycine, 10 mM Succinic acid at pH 4.6. The stock PAE contained 99% of monomer and had density and viscosity of 1.0067 g ml-1 and 1.297 mPa s-1, respectively. Different concentration of PAE solutions were obtained via either ultrafiltration/diafiltration or dilution of the stock material. All chemicals were purchased from VWR (Radnor, PA).