Effects of solution conditions on virus retention by the Viresolve^®NFP filter

Abstract

Virus filtration can provide a robust method for removal of adventitious parvoviruses in the production of biotherapeutics. Although virus filtration is typically thought to function by a purely size-based removal mechanism, there is limited data in the literature indicating that virus retention is a function of solution conditions. The objective of this work was to examine the effect of solution pH and ionic strength on virus retention by the Viresolve(®) NFP membrane. Data were obtained using the bacteriophage ϕX174 as a model virus, with retention data complemented by the use of confocal microscopy to directly visualize capture of fluorescently labeled ϕX174 within the filter. Virus retention was greatest at low pH and low ionic strength, conditions under which there was an attractive electrostatic interaction between the negatively charged membrane and the positively charged phage. In addition, the transient increase in virus transmission seen in response to a pressure disruption at pH 7.8 and 10 was completely absent at pH 4.9, suggesting that the trapped virus are unable to overcome the electrostatic attraction and diffuse out of the pores when the pressure is released. Further confirmation of this physical picture was provided by confocal microscopy. Images obtained at pH 10 showed the migration of previously captured phage; this phenomenon was absent at pH 4.9. These results provide important new insights into the factors governing virus retention using virus filtration membranes.

The effects of buffer condition on the fouling behavior of MVM virus filtration of an Fc‐fusion protein

“…Previous studies (Bakhshayeshi & Zydney, 2008; G. R. Bolton, Spector, & LaCasse, 2006;Dishari et al, 2015;Hongo-Hirasaki, Komuro, & Ide, 2010;Rayfield et al, 2015;Wickramasinghe, Stump, Grzenia, Husson, & Pellegrino, 2010) show that buffer conditions, including pH, buffer type, and ionic strength could affect the filtration performance of the virus filters. In addition, earlier studies have shown that the performance of virus filters is also dependent on the specific protein in the feed (Stuckey et al, 2014).…”

“…Early studies (G. R. Bolton et al, 2010; G. R. Bolton, LaCasse, & Kuriyel, 2006) observed that a prefiltration membrane with entrapped diatomaceous earth could greatly increase the capacity of parvovirus retentive filters and concluded that the major fouling species are a subset of oxidized or degraded IgG molecules with more hydrophobic surface properties. Many previous studies have investigated the effect of pH and types of fouling species on the virus filter capacity and proposed various strategies such as using adsorptive prefilters to achieve higher throughput (Bakhshayeshi & Zydney, 2008; G. R. Dishari et al, 2015;Hongo-Hirasaki et al, 2010;Wickramasinghe et al, 2010). However, up to now, there is still little understanding on the effects of ionic strength, pH, and buffer type on the fouling behavior of virus filters and subsequently their performances including both throughout and virus retention.…”

Interactions between protein molecules and the virus removal membrane surface: Effects of immunoglobulin G adsorption and conformational changes on filter performance

“…Recent virus filtration studies have focused on the effects of process parameters on throughput and viral retention. Operating pressure and solution conditions have been identified as crucial parameters for virus retention. Dishari et al indicated that solution pH and ionic strength can alter the electrostatic interactions between viruses and membranes, affecting virus retention .…”

Adapting viral safety assurance strategies to continuous processing of biological products

“…Therefore, when designing any viral filtration into a continuous flow‐through process, product specific factors, such as buffer pH, conductivity, pressure, or flow rates and their effect on viral filter retention must be considered. Potential frameworks for these considerations exist for batch processing (Bolton et al, ; Dishari et al, ; Hongo‐Hirasaki et al, ) that may be utilized in designing continuous viral filtration methods or when performing validation studies. As with batch processing methods, integrating any novel or adapted viral filtration into a continuous flow‐through polishing process will require validation of clearance, but often this can be performed as an isolated unit in batch mode.…”