Factors Affecting Virus Removal Effect

Factors Affecting Virus Removal Effect

The virus removal filtration can significantly remove viruses in solutions, and its removal effect is related to where virus removal filtration takes place, protein concentration of the feed liquid, filtration pressure, storage time and cryopreservation, etc.

1. Where virus removal filtration takes place

Virus removal filtration can occur anywhere in the downstream purification, but it usually takes place after low pH virus inactivation, intermediate chromatography steps or final chromatography steps. Overall, throughout the downstream process, actual filtration requirements are highly dependent on where in the process the virus filtration step resides, as protein concentration, purity and process volumes can vary.

2. Protein concentration of the feed liquid

The protein concentration of the sample will affect the flux of the virus removal filtration through the interaction between the feed solution and the membrane bag. A higher protein concentration will reduce the rate of the virus removal filtration process. It is also related to the properties of the protein itself and the membrane itself. Usually, the product concentration is reduced during the continuous dilution of the product to increase the capacity and flow rate of the virus removal filter membrane.

3. Filtration pressure

The process of virus removal filtration generally needs to ensure continuous filtration. Because the pressure interruption may lead to virus penetration. The principle is: the convective effect of the feed liquid flowing through the filter causes the virus particles to be trapped on the surface of the membrane or trapped in the smaller pore size due to molecular size exclusion. When the pressure drops, the flow rate and the convection effect decreases. The virus will escape and release from small pores, and diffuse to large pores with a high probability to penetrate.

4. Storage time and cryopreservation

Some proteins form aggregates during storage process, especially during cryopreservation. These aggregates can have an impact on virus removal filtration. Therefore, it needs to be evaluated if there is a long period of storage in the production process or when is cryopreservation required.