Detection of Minute virus of mice strains in different cell lines: Implications for adventitious agent testing.

Minute virus of mice (MMV) has contaminated biotechnological processes in the past and specific MMV testing is therefore recommended, if the production cell line is known to be permissive for this virus. Testing is widely done using cell-culture-based adventitious virus assays, yet MMV strains may differ in their in vitro cell tropism. Here, we investigated the growth characteristics of different MMV strains on A9 and 324K cells and identified significant differences in susceptibility of these widely used indicator cell lines to infection by different strains of MMV, which has implications for MMV detectability during routine testing of biotechnology process harvests. An MMV-specific polymerase chain reaction was evaluated as a more encompassing method and was shown as suitable replacement for cell culture-based detection of the different MMV strains, with the additional benefit that detection is more rapid and can be extended to other rodent parvoviruses that might contaminate biotechnological processes. Although no MMV contamination event of human-derived cell lines has happened in the past, biotechnological processes that are based on these also need to consider MMV-specific testing, as, for example, HEK293, a human-derived cell line commonly used in biopharmaceutical manufacturing, was shown as susceptible to productive MMV infection in the current work.

Protection of biomanufacturing processes from virus contamination through upstream virus filtration of cell culture media.

Cell-based manufacturing processes have occasionally been exposed to adventitious viruses, leading to manufacturing interruptions and unstable supply situations. The rapid progress of advanced therapy medicinal products needs innovative approaches to avoid any unwelcome reminder of the universal presence of viruses. Here, we investigated upstream virus filtration as a clearance step for any product too complex for downstream interventions. Culture media virus filtration was investigated with respect to virus clearance capacities under extreme conditions such as high process feed loading (up to ~19,000 L/m²), long duration (up to 34 days), and multiple process interruptions (up to 21 h). The small nonenveloped Minute virus of mice was used as relevant target virus, and as worse-case challenge for the investigated virus filters with a stipulated pore-size of about 20 nm. Certain filters-especially of the newer second generation-were capable of effective virus clearance despite the harsh regimen they were subjected to. The biochemical parameters for un-spiked control runs showed the filters to have no measurable impact on the composition of the culture media. Based on these findings, this technology seems to be quite feasible for large volume premanufacturing process culture media preparations.

Historical evaluation of the in vivo adventitious virus test and its potential for replacement with next generation sequencing (NGS).

The Consortium on Adventitious Agent Contamination in Biomanufacturing (CAACB) collected historical data from 20 biopharmaceutical industry members on their experience with the in vivo adventitious virus test, the in vitro virus test, and the use of next generation sequencing (NGS) for viral safety. Over the past 20 years, only three positive in vivo adventitious virus test results were reported, and all were also detected in another concurrent assay. In more than three cases, data collected as a part of this study also found that the in vivo adventitious virus test had given a negative result for a sample that was later found to contain virus. Additionally, the in vivo adventitious virus test had experienced at least 21 false positives and had to be repeated an additional 21 times all while using more than 84,000 animals. These data support the consideration and need for alternative broad spectrum viral detection tests that are faster, more sensitive, more accurate, more specific, and more humane. NGS is one technology that may meet this need. Eighty one percent of survey respondents are either already actively using or exploring the use of NGS for viral safety. The risks and challenges of replacing in vivo adventitious virus testing with NGS are discussed. It is proposed to update the overall virus safety program for new biopharmaceutical products by replacing in vivo adventitious virus testing approaches with modern methodologies, such as NGS, that maintain or even improve the final safety of the product.

Virus disinfection for biotechnology applications: Different effectiveness on surface versus in suspension.

Virus contamination events in cell culture-based biotechnology processes have occurred and have had a dramatic impact on the supply of life-saving drugs, and thus on the wellbeing of patients. Cleanup requires effective and robust virucidal decontamination procedures for both the liquid reactor content before discharge, as well as facility surfaces to prevent recurrence. Beyond rare contamination events, it is important to implement virucidal disinfection for change-over procedures as effective preventive measure in routine biomanufacturing. Knowledge of the virus inactivation capacity of commonly used disinfectants is therefore important. However, available virus inactivation data often refer to studies performed in suspension only, and not, as often more relevant, to virus inactivation on surfaces. In this study three liquid disinfectants, based on sodium hypochlorite, glutaraldehyde, or hydrogen peroxide/peroxyacetic acid, as well as one gaseous hydrogen peroxide-based disinfectant were investigated for inactivation of lipid enveloped and non-lipid enveloped model viruses, using suspension (for the liquid disinfectants) and carrier assay designs for their virucidal efficacy on surface. The results of these side-by-side investigations demonstrate that depending on the type of application, i.e. routine surface disinfection or decontamination of e.g. a contaminated bioreactor content, the most effective choice of disinfectant may be remarkably different.

SARS-CoV-2 and the safety margins of cell-based biological medicinal products.

With the pandemic emergence of SARS-CoV-2, the exposure of cell substrates used for manufacturing of medicines has become a possibility. Cell lines used in biomanufacturing were thus evaluated for their SARS-CoV-2 susceptibility, and the detection of SARS-CoV-2 in culture supernatants by routine adventitious virus testing of fermenter harvest tested.

Continued use of poliovirus after eradication: hyper-attenuated strains as a safe alternative for release testing of human immunoglobulins.

BACKGROUND: Wild-type poliovirus may be eradicated soon and under WHO GAPIII guidance, laboratory use will be discontinued or subject to strict containment. Per US Code of Federal Regulations, however, immunoglobulin lot release testing will still require use of replicating poliovirus. The suitability of S19 hyper-attenuated and apathogenic poliovirus strains as alternatives to the currently used wild-type virus in such a release assay was investigated. STUDY DESIGN AND METHODS: S19 poliovirus strains were propagated in a commercial setting using good virological practices and maintenance of the S19 hyper-attenuated genotype was confirmed by massively parallel sequencing. RESULTS: The attenuated phenotype of the produced S19 stocks was confirmed in a highly sensitive mouse-model. Equivalency in performance was seen in the lot release assay for the S19 and wild-type polioviruses. CONCLUSION: The deployment of such hyper-attenuated and thoroughly characterized S19 stocks in these and other essential activities might reconcile final containment measures with continued safe use of poliovirus.

Measles Virus Neutralizing Antibodies in Intravenous Immunoglobulins: Is an Increase by Revaccination of Plasma Donors Possible?

We report a screen of plasma donors confirming that widespread use of childhood measles vaccination since 1963 resulted in a decrease in average measles virus antibody titers among plasma donors, which is reflected in intravenous immunoglobulins (IVIGs). The measles virus antibody titer, however, is a potency requirement for IVIGs, as defined in a Food and Drug Administration regulation. To mitigate the decline in measles virus antibody titers in IVIGs and to ensure consistent product release, revaccination of plasma donors was investigated as a means to boost titers. However, revaccination-induced titer increases were only about 2-fold and short-lived.

Hepatitis E virus and the safety of plasma products: investigations into the reduction capacity of manufacturing processes.

BACKGROUND: Hepatitis E virus (HEV) has been transmitted by transfusion of labile blood products and the occasional detection of HEV RNA in plasma pools indicates that HEV viremic donations might enter the manufacturing process of plasma products. To verify the safety margins of plasma products with respect to HEV, virus reduction steps commonly used in their manufacturing processes were investigated for their effectiveness to reduce HEV. STUDY DESIGN AND METHODS: Detection methods for HEV removal (by reverse transcription quantitative polymerase chain reaction) and inactivation (using an infectivity assay) were established. Immunoaffinity chromatography and 20-nm virus filtration for Factor (F)VIII, cold ethanol fractionation, and low-pH treatment for immunoglobulin, heat treatment for human albumin, and 35-nm nanofiltration for FVIII inhibitor-bypassing activity (FEIBA) were investigated for their capacity to reduce HEV or the physicochemically similar viruses feline calicivirus (FCV) and hepatitis A virus (HAV). RESULTS: For FVIII, HEV reduction of 3.9 and more than 3.9 log was demonstrated for immunoaffinity chromatography and 20-nm nanofiltration, respectively, and the cold ethanol fractionation for immunoglobulin removed more than 3.5 log of HEV, to below the limit of detection (LOD). Heat treatment of human albumin inactivated more than 3.1 log of HEV to below the LOD and 35-nm nanofiltration removed 4.0 log of HEV from the FEIBA intermediate. The results indicated HAV rather than FCV as the more relevant model virus for HEV. CONCLUSION: Substantial HEV reduction during processes commonly used in the manufacturing of plasma products was demonstrated, similar to that previously demonstrated for HAV.

Measuring the effectiveness of gaseous virus disinfectants.

The efficacy of gaseous disinfection is critical for prevention and treatment of microbial contamination in biotechnological facilities. For an evaluation of gaseous disinfection efficacy, a down-scaled laboratory model was established, using currently available carrier tests and a custom-made dry fog box. A mixture of peroxyacetic acid and hydrogen peroxide (PAA/HP) was investigated as example, at concentrations between 0.4 and 2.9 mL/m(3) for up to 3 h for inactivation of a panel of lipid-enveloped and non-lipid-enveloped viruses. The influenza viruses were most sensitive to PAA/HP treatment and minute virus of mice was most resistant. Bovine viral diarrhea virus and reovirus III showed intermediate stability and similar inactivation kinetics. Use of the dry fog box circumvents dedicating an entire lab for the investigation, which renders the generation of data more cost-effective and allows for production of highly reproducible kinetic data.

Inactivation of hepatitis A variants during heat treatment (pasteurization) of human serum albumin.

BACKGROUND: Pasteurization of human serum albumin (HSA) is detailed in the US and European Pharmacopoeial monographs and therefore a process that allows for little variation in physiochemical variables. Nevertheless, differences of up to 3.9 log in hepatitis A virus (HAV) inactivation by pasteurization have been reported. Here, the hypothesis that the choice of HAV variant used in the pasteurization might contribute to this inactivation variability is evaluated experimentally. STUDY DESIGN AND METHODS: The identity of four widely used cytopathic variants of the original HAV HM175 strain was determined by partial sequencing. These variants were used in pasteurization studies conducted under the principles of good laboratory practice, for which HAV-spiked HSA of 5 or 25% protein content was kept at 58±1°C for 600±10 minutes, and the virus inactivation was assessed. In addition, data from previous pasteurization studies were included in the analysis. RESULTS: The four HAV variants could be divided into two subgroups, with significantly different (p≤0.0001) virus inactivation by pasteurization (4.7 and 4.8 log vs. 2.3 and 2.6 log, respectively). Also, the protein concentration of the HSA solution used for pasteurization had a significant effect on the achieved HAV inactivation, with reduction factors obtained in 5% HSA significantly lower than in 25% HSA (p<0.002). CONCLUSION: HAV variant and protein concentration of the HSA solution affect the overall HAV inactivation that is achieved during pasteurization. As the HAV inactivation capacity should not be overestimated, an HAV variant more resistant to heat inactivation should be used for studies investigating the viral safety profiles of plasma derivatives.

Chikungunya virus and the safety of plasma products.

BACKGROUND: Chikungunya virus (CHIKV) outbreaks were previously restricted to parts of Africa, Indian Ocean Islands, South Asia, and Southeast Asia. In 2007, however, the first autochthonous CHIKV transmission was reported in Europe. High-level viremia, a mosquito vector that is also present in large urban areas of Europe and America, and uncertainty around the resistance of this Alphavirus toward physiochemical inactivation processes raised concerns about the safety of plasma derivatives. To verify the safety margins of plasma products with respect to CHIKV, commonly used virus inactivation steps were investigated for their effectiveness to inactivate this newly emerging virus. STUDY DESIGN AND METHODS: Pasteurization for human serum albumin (HSA), vapor heating for Factor VIII inhibitor bypassing activity, solvent/detergent (S/D) treatment for intravenous immunoglobulin (IVIG), and incubation at low pH for IVIG were investigated for their capacity to inactivate CHIKV and the closely related Sindbis virus (SINV). The obtained results were compared to previous studies with West Nile virus and the commonly used model virus bovine viral diarrhea virus. RESULTS: The data generated demonstrate the effective inactivation of CHIKV as well as SINV by the inactivation steps investigated and thereby support results from earlier validation studies in which model viruses were used. CONCLUSION: High inactivation capacities with respect to CHIKV were demonstrated. This provides solid reassurance for the safety of plasma products and the results verify that the use of model viruses is appropriate to predict the inactivation characteristics of newly emerging viruses when their physicochemical properties are well characterized.

Hepatitis A virus antibodies in immunoglobulin preparations.

BACKGROUND: Persons with primary immune deficiency receive intravenous immunoglobulin (IVIG) as antibody replacement therapy. These patients depend on the presence of protective antibody levels against circulating pathogens in IVIG. OBJECTIVES: The incidence of hepatitis A virus (HAV) infections has been decreasing globally. We investigated whether this decrease in HAV incidence is reflected in human plasma pools and evaluated whether HAV antibody titers in IVIG preparations are still adequate for antibody replacement. METHODS: By using ELISA, the HAV antibody titer of 3,953 plasma pools sourced from March 2003 through September 2008 in the European Union (EU) or United States (US) and of 169 IVIG lots manufactured from 2005 through 2007 was determined. The functionality of the HAV antibodies contained in IVIG was assessed by using a microneutralization assay. RESULTS: The results confirm a decrease in HAV antibody titers in EU (-28%) and US (-41%) plasma. Furthermore, the mean HAV antibody content in EU (1.70 +/- 0.12 IU/mL) and US (0.82 +/- 0.09 IU/mL [mean +/- SEM]) plasma was significantly different (P = .0001). A significant difference (P < .0001) was also evident in the IVIG preparations KIOVIG (22.91 +/- 0.68 IU/mL) and Gammagard Liquid (14.60 +/- 0.48 IU/mL), respectively, made from EU or US plasma. In accordance with the ELISA results, there was a significant difference (P < .0001) in HAV neutralization titer 50% (NT(50)) values between IVIG produced from EU-sourced (2,477 +/- 265 NT(50) [1:X]) or US-sourced (844 +/- 82 NT(50) [1:X]) plasma. CONCLUSION: Although HAV antibody seroprevalence continues to decrease in Europe and the US, HAV antibody titers in IVIG lots appear to remain adequate for antibody replacement therapy.

West Nile virus infection in plasma of blood and plasma donors, United States.

This study investigated the association of ongoing West Nile virus (WNV) infections with neutralizing antibody titers in US plasma-derived intravenous immune globulin released during 2003-2008. Titers correlated closely with the prevalence of past WNV infection in blood donors, with 2008 lots indicating a prevalence of 1%.

Virus inactivation during the freeze-drying processes as used for the manufacture of plasma-derived medicinal products.

BACKGROUND: Freeze-drying is a technology widely used during the production of plasma-derived medicinal products. Several studies have shown that freeze-drying can also result in virus inactivation and particularly of hepatitis A virus (HAV). To date, however, the variables critical for virus inactivation during freeze-drying have not been investigated systematically. STUDY DESIGN AND METHODS: Five different lyophilization processes covering the range used for different plasma-derived medicinal products (Factor [F]VII, FVIII, F IX, FVIII inhibitor bypassing activity, and fibrin sealer protein [FSP]) were investigated for their potential to inactivate HAV as well as bovine viral diarrhea virus (BVDV) and pseudorabies virus (PRV). RESULTS: Our investigation demonstrates that freeze-drying results in significant inactivation of HAV, with reduction factors between 2.5 and 5.9 log [TCID(50)]. Also, BVDV and PRV were inactivated, although to a lesser extent. While the specific details of the freeze-drying processes investigated only had a minor influence on virus inactivation, the different compositions of product intermediates had a rather pronounced impact. CONCLUSION: Lyophilization contributes to the safety of plasma derivatives, in particular with the inactivation of HAV. The extent of HAV inactivation is strongly influenced by the respective product matrix rather than the design of the lyophilization cycle, which will require a case-to-case assessment for each product intermediate.

Parallel evaluation of broad virus detection methods.

The testing for adventitious viruses is of critical importance during development and production of biological products. The recent emergence and ongoing development of broad virus detection methods calls for an evaluation of whether these methods can appropriately be implemented into current adventitious agent testing procedures. To assess the suitability of several broad virus detection methods, a comparative experimental study was conducted: four virus preparations, which were spiked at two different concentrations each into two different cell culture media, were sent to four investigators in a blinded fashion for analysis with broad virus detection methods such as polymerase chain reaction-electrospray ionization mass spectrometry (PCR-ESI/MS), microarray, and two approaches utilizing massively parallel sequencing. The results that were reported by the investigators revealed that all methods were able to identify the majority of samples correctly (mean 83%), with a surprisingly narrow range among the methods, that is, between 72% (PCR-ESI/MS) and 95% (microarray). In addition to the correct results, a variety of unexpected assignments were reported for a minority of samples, again with little variation regarding the methods used (range 20-45%), while false negatives were reported for 0-25% of the samples. Regarding assay sensitivity, the viruses were detected by all methods included in this study at concentrations of about 4-5 log10 quantitative PCR copies/mL, and probably with higher sensitivity in some cases. In summary, the broad virus detection methods investigated were shown to be suitable even for detection of relatively low virus concentrations. However, there is also some potential for the production of false-positive as well as false-negative assignments, which indicates the requirement for further improvements before these methods can be considered for routine use.

Reduction of spiked porcine circovirus during the manufacture of a Vero cell-derived vaccine.

Porcine circovirus-1 (PCV1) was recently identified as a contaminant in live Rotavirus vaccines, which was likely caused by contaminated porcine trypsin. The event triggered the development of new regulatory guidance on the use of porcine trypsin which shall ensure that cell lines and porcine trypsin in use are free from PCV1. In addition, manufacturing processes of biologicals other than live vaccines include virus clearance steps that may prevent and mitigate any potential virus contamination of product. In this work, artificial spiking of down-scaled models for the manufacturing process of an inactivated pandemic influenza virus vaccine were used to investigate inactivation of PCV1 and the physico-chemically related porcine parvovirus (PPV) by formalin and ultraviolet-C (UV-C) treatment as well as removal by the purification step sucrose gradient ultracentrifugation. A PCV1 infectivity assay, using a real-time PCR infectivity readout was established. The formalin treatment (0.05% for 48h) showed substantial inactivation for both PCV1 and PPV with reduction factors of 3.0log10 and 6.8log10, respectively, whereas UV-C treatment resulted in complete PPV (≥5.9log10) inactivation already at a dose of 13mJ/cm but merely 1.7log10 at 24mJ/cm(2) for PCV1. The UV-C inactivation results with PPV were confirmed using minute virus of mice (MVM), indicating that parvoviruses are far more sensitive to UV-C than PCV1. The sucrose density gradient ultracentrifugation also contributed to PCV1 clearance with a reduction factor of 2log10. The low pH treatment during the production of procine trypsin was investigated and showed effective inactivation for both PCV1 (4.5log10) and PPV (6.4log10). In conclusion, PCV1 in general appears to be more resistant to virus inactivation than PPV. Still, the inactivated pandemic influenza vaccine manufacturing process provides for robust virus reduction, in addition to the already implemented testing for PCV1 to avoid any contaminations.

Inactivation of parvovirus B19 during STIM-4 vapor heat treatment of three coagulation factor concentrates.

BACKGROUND: To enhance the viral safety margins, nanofiltration has been widely integrated into the manufacturing process of plasma-derived medicinal products. Removal of smaller agents such as parvovirus B19 (B19V) by filtration, however, is typically less efficient. Because recent investigations have demonstrated that B19V may be more heat sensitive than animal parvoviruses, the potential B19V inactivation by a proprietary vapor heating procedure (STIM-4) as incorporated into the manufacturing processes of several nanofiltered coagulation factor concentrates was investigated. STUDY DESIGN AND METHODS: An infectivity assay based on quantitative reverse transcription-polymerase chain reaction (TaqMan, Applied Biosystems) detection of B19V mRNA after inoculation of a permissive cell line (UT7 Epo S1 cells) was used to investigate the virus inactivation capacity of the STIM-4 vapor heat treatment as used during the manufacture of nanofiltered second-generation Factor VIII inhibitor-bypassing activity (FEIBA), F IX complex, and FVII products. RESULTS: In contrast to animal parvoviruses, both B19V genotypes investigated, that is, 1 and 2, were shown to be surprisingly effectively inactivated by the STIM-4 vapor heat treatment process, with mean log reduction factors of 3.5 to 4.8, irrespective of the product intermediate tested. CONCLUSION: The newly demonstrated effective inactivation of B19V by vapor heating, in contrast to the earlier used animal parvoviruses, results in significant B19V safety margins for STIM-4-treated coagulation factor concentrates.

Neutralization of human parvovirus B19 by plasma and intravenous immunoglobulins.

BACKGROUND: Human parvovirus B19 (B19V) is a highly prevalent pathogen, and plasma pools for manufacturing of plasma-derived products have been shown to contain antibodies against B19V (B19V immunoglobulin G [IgG]). STUDY DESIGN AND METHODS: The megakaryoblastic cell line UT7/Epo-S1 can be infected with B19V Genotype 1 and as demonstrated here by immunocytochemistry, Western blot, and reverse transcription-polymerase chain reaction (RT-PCR) of B19V-specific mRNA, also with the more recently discovered Genotype 2. Based on B19V RT-PCR analysis of infected UT7/Epo-S1 cells, an infectivity assay was established and implemented for a B19V neutralization assay. To investigate the role of B19V neutralization in relation to B19V IgG titers, more than 1,000 manufacturing plasma pools were tested by enzyme-linked immunosorbent assay. RESULTS: Plasma pools were found to contain a mean B19V IgG titer of 33 +/- 9 IU per mL, with the lowest titer at 11 IU per mL. These 11 IU per mL B19V IgG neutralized 4.6 log B19V Genotype 1 and greater than 3.9 log Genotype 2 infectivity. Accordingly, a 10 percent intravenous immunoglobulin (IVIG) product prepared from such pools was found to contain an even higher B19V neutralization capacity. CONCLUSION: A high capacity of B19V Genotypes 1 and 2 neutralization was demonstrated in plasma pools for fractionation, an inherent feature based on the constantly high titer of B19V IgG in these pools. The neutralizing activity of B19V IgG was shown to be maintained in the 10 percent IVIG product tested.

West Nile virus neutralization by US plasma-derived immunoglobulin products.

The 1999 introduction of West Nile virus (WNV) into the United States has resulted in the largest epidemic of arboviral illness in the Western Hemisphere, with an estimated 2.5 million cases of mostly asymptomatic human infections since then. As a consequence, an increasing occurrence of WNV antibodies in plasma collected in the United States, and thus in intravenous immunoglobulin (IVIG) products, can be expected. Using an in vitro assay to investigate antibody function, rather then presence, almost 1000-fold differences in neutralization capacity were demonstrated between individual IVIG lots. In a mouse model of lethal WNV infection, treatment with IVIG of a higher WNV antibody titer protected recipients, whereas mice treated with control IVIG died. IVIG lots with higher WNV antibody titers would seem to be desirable for substitution therapy for people with immunodeficiencies.

Phosphorylation of bluetongue virus nonstructural protein 2 is essential for formation of viral inclusion bodies.

In bluetongue virus (BTV)-infected cells, large cytoplasmic aggregates are formed, termed viral inclusion bodies (VIBs), which are believed to be the sites of viral replication and morphogenesis. The BTV nonstructural protein NS2 is the major component of VIBs. NS2 undergoes intracellular phosphorylation and possesses a strong single-stranded RNA binding activity. By changing phosphorylated amino acids to alanines and aspartates, we have mapped the phosphorylated sites of NS2 to two serine residues at positions 249 and 259. Since both of these serines are within the context of protein kinase CK2 recognition signals, we have further examined if CK2 is involved in NS2 phosphorylation by both intracellular colocalization and an in vitro phosphorylation assay. In addition, we have utilized the NS2 mutants to determine the role of phosphorylation on NS2 activities. The data obtained demonstrate that NS2 phosphorylation is not necessary either for its RNA binding properties or for its ability to interact with the viral polymerase VP1. However, phosphorylated NS2 exhibited VIB formation while unmodified NS2 failed to assemble as VIBs although smaller oligomeric forms of NS2 were readily formed. Our data reveal that NS2 phosphorylation controls VIBs formation consistent with a model in which NS2 provides the matrix for viral assembly.