Companies: Asahi kasei Bioprocess, Inc.; Asahi Kasei Medical; Millipore

See also Virus filtration during antibody purification under “antibodies” 

Types of Membranes  See outline    Conditions/Parameters See “operating conditions”

Since infection with an infectious virus among pathogenic agents may cause serious diseases, removal of contaminating viruses is highly required (EP 1552878A1). Regulatory guidelines require that recombinant DNA dervied protein products for human use meet a criterion of less than 1 virus particle per million doses. There is also a requirement to demonstrate that virus inactivation and clearance are accomplished using at least threee different mechanbisms. Common methds for removal of viruses include sized based filtration, affinity and anion exchange chromatography. Methods for inactviation often include low pH, heat, and use of solvents and detergents. (Van Reis, “Bioprocess membrane technology, Science 297 (2007) 16-50) 

Shukla, (J. Chromatogr. B 848 (2007) 28-39) discloses employing viral filtration in antibody purification scheme to complement a low pH viral inactivation step. 

Current virus retentive filters are ultrafilters or microfilters with very small pores. Virus filtration membranes are made from hydrophilic polyethersulfone (PES), hydrophilic polyvinylidene (PVDF) adn regenerated cellulose. (Liu, “Recovery and purification process development for monoclonal antibody production” mAbs,  2:5: 480-499 (2010)

Nanofiltration for Removing Viruses: 

Nanofiltraiton is a very effective method for removing viruses. In this respect, the pore size of the filter has to be smaller than the effective diameter of the virus which is to be removed. In addition, the temperature, the properties of the materials and the buffering conditions are of importance. Parvovirus can be reliably removed using filters having a pore diameter of 15 nm and nanofiltraiton has been used for separating hepatits A virus and parvovirus from factor IX preparations with filters such as Virsolve 70, Planova 15N and Pall Ultipor DV20. In contrast, blood coagulation factor IX has a low MW of 56kDa and is thus not retained by membranes employed for nanofiltration, Large proteins such as fibronogen, von Willebrand factor and factor VII are alos too big to be freed from viruses by filtering them through a nanofilter haivng a pore size of from 15-35 nm. (Lengsfeld US 2003/0232969). 

Size of Viruses Determine Diameter of Filter to Use

Types of viruses include smallest viruses, such as parvovirus, with a diameter of about 18-24 nm, medium-sized viruses, such as Japanese encephalitis virus, with a diameter of about 40-45 and relatively large viruses, such as HIV, with a diameter of about 80-100 nm. In order to remove these virus groups physically by the membrane filtration method, a microporous membrane having a pore size of about 10-100 nm is required.