title: Reversible NaCl-induced aggregation of a monoclonal antibody at low pH: Characterization of aggregates and factors affecting aggregation.
abstract: We investigated the influence of pH and sodium chloride concentration on aggregation kinetics of a monoclonal antibody. Aggregation was induced by sodium chloride addition at low pH. Protein conformation before and after salt addition was determined as well as the reversibility of aggregation. Aggregation was monitored at pH values between 2 and 7 with NaCl up to 1.5M by turbidity measurement and size-exclusion chromatography. Particle size distribution was assessed by using size-exclusion chromatography as well as nanoparticle tracking analysis and flow imaging microscopy. Structural changes were monitored by circular dichroism, Fourier transform infrared and fluorescence spectroscopy. Thermal stability was measured by differential scanning fluorimetry. Aggregation propensity was maximal at low pH and high ionic strength. While thermal stability decreased with pH, the secondary structure remained unchanged down to pH 3.5 and up to 1.5M NaCl. Precipitated protein could be largely reverted to monomers by dilution into salt-free buffer. The re-solubilized antibody was indistinguishable in structure, solubility and monodispersity from the unstressed protein. Also, binding to Protein A was steady. Aggregation could be reduced in the presence of trehalose. The results suggest a reversible aggregation mechanism characterized by a limited change in tertiary structure at low pH and a subsequent loss of colloidal stability resulting from electrostatic repulsion once salt is added to the sample. The experimental setup is robust and allows high-throughput quantification of the effect of additives on aggregation kinetics.
authors.affiliation: Institute of Applied Biotechnology, Biberach University of Applied Sciences, Hubertus-Liebrecht-Strasse 35, 88400 Biberach, Germany; Faculty of Medicine, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: bickel@hochschule-bc.de.
authors.forename: Fabian
authors.initials: F
authors.lastname: Bickel
authors.affiliation: Institute of Applied Biotechnology, Biberach University of Applied Sciences, Hubertus-Liebrecht-Strasse 35, 88400 Biberach, Germany.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Herold
authors.affiliation: Institute of Applied Biotechnology, Biberach University of Applied Sciences, Hubertus-Liebrecht-Strasse 35, 88400 Biberach, Germany.
authors.forename: Alba
authors.initials: A
authors.lastname: Signes
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, P.O. Box 2300, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: Romeijn
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, P.O. Box 2300, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: Jiskoot
authors.affiliation: Institute of Applied Biotechnology, Biberach University of Applied Sciences, Hubertus-Liebrecht-Strasse 35, 88400 Biberach, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Kiefer
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D009391:Nephelometry and Turbidimetry; D009994:Osmolar Concentration; D010316:Particle Size; D012965:Sodium Chloride / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014199:Trehalose / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D012965:Sodium Chloride; D014199:Trehalose
keywords: Acidic conditions; Aggregate; Downstream processing; IgG; MAb; Reversibility; Salt