Microscopic visualization of virus removal by dedicated filters used in biopharmaceutical processing: Impact of membrane structure and localization of captured virus particles

Abstract

Virus filtration with nanometer size exclusion membranes (“nanofiltration”) is effective for removing infectious agents from biopharmaceuticals. While the virus removal capability of virus removal filters is typically evaluated based on calculation of logarithmic reduction value (LRV) of virus infectivity, knowledge of the exact mechanism(s) of virus retention remains limited. Here, human parvovirus B19 (B19V), a small virus (18–26 nm), was spiked into therapeutic plasma protein solutions and filtered through Planova™ 15N and 20N filters in scaled‐down manufacturing processes. Observation of the gross structure of the Planova hollow fiber membranes by transmission electron microscopy (TEM) revealed Planova filter microporous membranes to have a rough inner, a dense middle and a rough outer layer. Of these three layers, the dense middle layer was clearly identified as the most functionally critical for effective capture of B19V. Planova filtration of protein solution containing B19V resulted in a distribution peak in the dense middle layer with an LRV >4, demonstrating effectiveness of the filtration step. This is the first report to simultaneously analyze the gross structure of a virus removal filter and visualize virus entrapment during a filtration process conducted under actual manufacturing conditions. The methodologies developed in this study demonstrate that the virus removal capability of the filtration process can be linked to the gross physical filter structure, contributing to better understanding of virus trapping mechanisms and helping the development of more reliable and robust virus filtration processes in the manufacture of biologicals.

Neuroprotective activity of a virus‐safe nanofiltered human platelet lysate depleted of extracellular vesicles in Parkinson's disease and traumatic brain injury models

“… 30 The capacity of Planova 20N to robustly remove B19V has also been demonstrated by microscopic observations of the nanofilter. 47 Finally, another small blood‐borne non‐enveloped virus, hepatitis E virus (HEV), with a size of 27–34 nm, was also demonstrated to be removed by Planova 20N. 48 Therefore, all known blood‐borne viruses of clinical relevance are removed by Planova 20N, providing a large safety margin to NHPPL.…”

Particle‐based analysis elucidates the real retention capacities of virus filters and enables optimal virus clearance study design with evaluation systems of diverse virological characteristics

“…The different membrane structures of the Planova 20N and 15N hollow fibers have different numbers of retaining pore structures, 22 which presumably generates differences in virus retention capacity. The difference in the MVM capture distribution confirms that there are differences between the filters in the membrane pore structures that contribute to virus retention (Figures 4d , S4 B).…”

A review on recent trends of antiviral nanoparticles and airborne filters: special insight on COVID-19 virus

“…From the above, we can conclude that the parvovirus model cannot be used every time. A few works provided an image for the parvovirus retention mechanism in the filter using immune detection and SEM for PPV and B19V (Adan-Kubo et al 2019 ) (Hongo-Hirasaki et al 2011 ). Moreover, TEM technique is also used for detecting the viral particles in the filter membrane.…”