Viral removal

An overview of the general principles of filtration having specific appHcation to bacterial and viral removal is given herein. The emphasis is on ensuring that the sterility and/or safety of biologicals and biopharmaceuticals be maintained. 

Methods to Detect and Quantitate Viral Agents in Fluids. In order to assess the effectiveness of membrane filtration the abihty to quantitate the amount of vims present pre- and post-filtration is critical. There are a number of techniques used. The method of choice for filter challenge studies is the plaque assay which utilizes the formation of plaques, localized areas in the cell monolayer where cell death caused by viral infection in the cell has occurred on the cell monolayer. Each plaque represents the presence of a single infectious vims. Vims quantity in a sample can be determined by serial dilution until the number of plaques can be accurately counted. The effectiveness of viral removal may be determined, as in the case of bacterial removal, by comparing the vims concentration in the input suspension to the concentration of vims in the effluent. 

Cell Bank Maintenance and Record Keeping Cell Culture/Fermentation Harvesting, Isolation, and Purification Viral Removal/Inactivation Steps APIs for Use in Clinical Trials General Quality... 

Specific virus reduction values achieved with each individual viral removal/inactiva-tion step are cumulative, so that the final viral reduction value attained reflects multiple removal and/or inactivation procedures occurring throughout the process. In summary, the processing of rAHF-PFM is associated with a significant viral reduction capacity for both lipid-enveloped and non-lipid-enveloped viruses and provides additional assurances of reliability with respect to pathogen safety. 

The eluate is then filtered through a PaU DV-20 viral removal filter (Step 3), concentrated, and diafiltered by membrane filtration to adjust the ionic strength for the application of the rhAT onto the ANX-Se-pharose column. After loading, the ANX-Sepharose column is washed and the rhAT is eluted with 0.32 M buffer (Step 4). The ANX-Sepharose eluate is conditioned with sodium citrate and applied to the Methyl HyperD column (Step 5). The Methyl Hy-perD column is washed and the rhAT eluted from the resin with a lower concentration sodium citrate buffer. 

Table 11.2 Validation of log,o viral removal or inactivation by the RhAT process...

Therefore, E. coli is one of the preferred hosts for the expression of antibody fragments [5]. Genetic modification of bacterial cell Hnes - especially E. coli - is rapid and trouble-free, and the media and nutrient supply is simple. The metaboHc potential of microbial cell Hnes allows the use of se-mm-free, chemically defined and cheap media. Expensive viral removal steps can be avoided, whilst the removal of pyrogens does not usually cause any problems. 

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