Reduction of chromatin heteroaggregates by acid precipitation of mammalian cell culture and ramification in protein A chromatography for recombinant immunoglobulin G purification

Abstract Acid precipitation has been demonstrated as a clarification method for cell culture supernatant (CCS) pretreatment during Immunoglobulin G (IgG) purification. In this study, the responses of IgG, non-histone host cell protein (n-hHCP), histone, and DNA to different pHs in the presence of salt (NaCl) at various concentrations were systematically studied. IgG loss was closely associated with the precipitation of chromatin heteroaggregates, in which DNA/histone showed significant decreases along with the acidification of buffer environment. In addition, DNA showed full recovery after pH neutralization, while the low pH treatment induced histone precipitation was permanent and could not be reverted upon pH increase. Analytical size exclusion chromatography (SEC) profiles further indicated the agglomeration and reduction of chromatin heteroaggregates along with lower pH. Protein A chromatography benefited from the reduction of chromatin heteroaggregates and showed significant enhancement of the removal of impurities as well as for IgG recovery. For the first time, this study correlated CCS acidification with chromatin heteroaggregate removal and illustrated its ramification for the subsequent purification process.