Log10 Reduction Factors in Viral Clearance Studies

by Horst Ruppach, PhD
Volume 12, Issue 4 (Winter 2013/2014)

Viral clearance studies are required for pharmaceuticals derived from human and/or animal sources such as recombinant proteins produced in eukaryotic cell lines, human blood products and vaccines, and even for some critical class III medical devices. It is mandatory to demonstrate that steps in the manufacturing process are capable of inactivating or removing potential viral contaminants. For this, a laboratory-scale (downscale) of the process step is developed and challenged with different model virus solutions. The viral concentrations are quantitatively determined in the feed material and the relevant product fraction. The ratio of both defines the reduction in virus and specifies the viral inactivation or viral removal capacity of the investigated process step.

In general, cell line-based infectivity assays like the plaque forming units (PFU) assay or the tissue culture infective dose (TCID50) assay are used to quantify the virus infectivity in the process solutions of a viral clearance study. In some cases, the quantitative polymerase chain reaction (qPCR) may be used. The viral titer derived from the viral infectivity assays is represented by log10/mL values. For instance, viral stock solutions used to challenge a process step typically have a viral titer of >107 log10 PFU/mL or TCID50/mL. The calculated ratio of the viral titer in the starting material and in the relevant product fraction defines the viral reduction, called log10 reduction factor (LRF), log10 reduction value(LRV), or sometimes simply log10 clearance. The mode of the LRF calculation is outlined in the relevant guidelines for viral clearance studies. If possible, the 95% confidence limit is calculated based on the 95% confidence limits of the single viral titers (the 95% confidence interval of the viral infectivity in: [A] the starting material; and [B] the final product fraction using the formula √ a2+b2 )...

Citation:
Ruppach H. Log10 Reduction Factors in Viral Clearance Studies. BioProcess J, 2014; 12(4): 24-30. http://dx.doi.org/10.12665/J124.Ruppach.

Posted online January 7, 2014.