Advance chromatin extraction improves capture performance of protein A affinity chromatography

Practical effects of advance chromatin removal on performance of protein A affinity chromatography were evaluated using a caprylic acid-allantoin-based extraction method. Lacking this treatment, the practice of increasing loading residence time to increase capacity was shown to increase host protein contamination of the eluted IgG. Advance chromatin extraction suspended that compromise. Protein A ligand leakage from columns loaded with chromatin-extracted harvest was half the level observed on protein A columns loaded with non-extracted harvest. Columns loaded with chromatin-extracted harvest were cleaned more effectively by 50-100 mM NaOH than columns loaded with non-extracted harvest that were cleaned with 250-500 mM NaOH. Two protein A media with IgG capacities in excess of 50 g/L were loaded with chromatin-extracted harvest, washed with 2.0 M NaCl before elution, and the eluted IgG fraction titrated to pH 5.5 before microfiltration. Host protein contamination in the filtrate was reduced to <1 ppm, DNA to <1 ppb, protein A leakage to 0.5 ppm, and aggregates to 1.0%. Caprylic acid and allantoin were both reduced below 5 ppm. Step recovery of IgG was 99.4%. Addition of a single polishing step reduced residual protein A beneath the level of detection and aggregates to <0.1%. Overall process recovery including chromatin extraction was 90%.