Binding of Coxsackievirus A21 procapsids to immobilized glutathione depends on cell culture conditions during infection

A prototype strain of Coxsackievirus A21 (CVA21) is under clinical evaluation as an oncolytic virus immunotherapy. To improve scalability of the manufacturing process, an affinity chromatography purification method was developed using immobilized glutathione resin that captured infectious CVA21 virions from cell culture harvests with high recovery and impurity clearance. Unexpectedly, the binding of empty CVA21 procapsids depended on production cell culture conditions during infection including temperature, presence of serum in the media, and production cell line. At 37 °C and 2% serum during infection, procapsids flowed-through while infectious virions bound and were recovered at >95% yield in the chromatography elution. However, at sub-physiological temperature or after removal of serum at infection, both procapsids and mature virions bound and co-eluted from the immobilized glutathione ligand. This work may improve the understanding of CVA21 capsid assembly and presents an efficient purification method that may be applied to picornaviruses that interact with intracellular GSH.