Limits in virus filtration capability? Impact of virus quality and spike level on virus removal with xenotropic murine leukemia virus

Abstract

Virus filtration (VF) is a key step in an overall viral clearance process since it has been demonstrated to effectively clear a wide range of mammalian viruses with a log reduction value (LRV) > 4. The potential to achieve higher LRV from virus retentive filters has historically been examined using bacteriophage surrogates, which commonly demonstrated a potential of > 9 LRV when using high titer spikes (e.g. 10(10) PFU/mL). However, as the filter loading increases, one typically experiences significant decreases in performance and LRV. The 9 LRV value is markedly higher than the current expected range of 4-5 LRV when utilizing mammalian retroviruses on virus removal filters (Miesegaes et al., Dev Biol (Basel) 2010;133:3-101). Recent values have been reported in the literature (Stuckey et al., Biotech Progr 2014;30:79-85) of LRV in excess of 6 for PPV and XMuLV although this result appears to be atypical. LRV for VF with therapeutic proteins could be limited by several factors including process limits (flux decay, load matrix), virus spike level and the analytical methods used for virus detection (i.e. the Limits of Quantitation), as well as the virus spike quality. Research was conducted using the Xenotropic-Murine Leukemia Virus (XMuLV) for its direct relevance to the most commonly cited document, the International Conference of Harmonization (ICH) Q5A (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use, Geneva, Switzerland, 1999) for viral safety evaluations. A unique aspect of this work is the independent evaluation of the impact of retrovirus quality and virus spike level on VF performance and LRV. The VF studies used XMuLV preparations purified by either ultracentrifugation (Ultra 1) or by chromatographic processes that yielded a more highly purified virus stock (Ultra 2). Two monoclonal antibodies (Mabs) with markedly different filtration characteristics and with similar levels of aggregate (<1.5%) were evaluated with the Ultra 1 and Ultra 2 virus preparations utilizing the Planova 20 N, a small virus removal filter. Impurities in the virus preparation ultimately limited filter loading as measured by determining the volumetric loading condition where 75% flux decay is observed versus initial conditions (V75). This observation occurred with both Mabs with the difference in virus purity more pronounced when very high spike levels were used (>5 vol/vol %). Significant differences were seen for the process performance over a number of lots of the less-pure Ultra 1 virus preparations. Experiments utilizing a developmental lot of the chromatographic purified XMuLV (Ultra 2 Development lot) that had elevated levels of host cell residuals (vs. the final Ultra 2 preparations) suggest that these contaminant residuals can impact virus filter fouling, even if the virus prep is essentially monodisperse. Process studies utilizing an Ultra 2 virus with substantially less host cell residuals and highly monodispersed virus particles demonstrated superior per...

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

“…Each process solution could interact with virus particles and/or with the membrane substrate. Roush et al reported that the impurity in the virus spike source affects virus removal capacity. Additionally, using three different monoclonal antibodies in comprehensive design space experiments, Strauss et al, demonstrated that solution conditions, as well as filtration pressure, could impact minute virus of mice LRV.…”

Defining the mechanistic binding of viral particles to a multi‐modal anion exchange resin

“…Host cell DNA levels had been previously linked to the breakthrough of viral particles, where it seemed to compete for resin binding potentially via competitive adsorption. Therefore, host cell DNA levels in load, and flow through samples were monitored using a hamster Alu‐like repeat sequence Q‐PCR assay described in detail in previous work for mAb containing experiments. The authors acknowledge that other in‐process impurities such as host cell proteins could contribute to the reduction of binding of virus, but it does not appear to be the same extent as DNA in this study.…”

Characterizing the impact of pressure on virus filtration processes and establishing design spaces to ensure effective parvovirus removal

“…Reduced performance has typically been associated with product aggregates clogging the filter membrane and reducing product throughput and, in some cases, reducing viral clearance . Impurities present in the virus spike also can play a significant role in filter fouling on certain filter types, although contract laboratories have made significant efforts to improve virus stock purity to lessen those effects …”