Virus removal robustness of ion exchange chromatography

Virus removal by ion exchange chromatography enhances the safety profile of therapeutic protein products. The robustness of virus removal depends on electrostatic binding between virus and oppositely charged chromatography media. However, model retrovirus Xenotropic Murine Leukemia Virus (XMuLV) binding remains robust even when virus and media are both positively charged. We investigated this counter-intuitive phenomenon using side-by-side comparison of virus-media binding behavior of XMuLV versus parvovirus, two viruses very different in size and structure but comparable in isoelectric point. When both viruses were negatively charged, XMuLV bound to positive anion exchange media with higher strength than parvovirus. When both viruses were positively charged, XMuLV remained tightly bound to positive media but parvovirus was dissociated. Likewise, XMuLV binding to media was much stronger than parvovirus under cation exchange conditions. These findings suggest that XMuLV binding could be enhanced by localized charge distribution not possessed by parvovirus, which is an important consideration for designing chromatography processes with robust virus removal capacity.