Rules Established to Allow Direct Comparison of Viral Clearance by Naïve and Cycled Resins
| Rule | Rationale |
|---|---|
| Rule 1: Result must not use infectivity assay for determination of enveloped virus titer during protein A chromatography | Viral clearance by protein A chromatography can result from two components: virus inactivation by acidic elution, and virus removal by partitioning. The infectivity assay cannot differentiate between enveloped virus inactivation and virus removal, so qPCR should be used. |
| Rule 2: The difference in load viral challenge between the naïve and the cycled resins must be <1.0 log10 | The virus amount in the load affects the experimental viral clearance results. |