Viral/TSE Clearance

Viral / TSE clearance by your manufacturing process is a critical aspect required by regulatory agencies worldwide to ensure the safety of biotherapeutic reagents.

Texcell helps to demonstrate the capacity of your manufacturing process in removal of and/or inactivation of adventitious agents.

All processes are performed in full compliance with GLP standards.

Texcell has experience working with many biological agents that include:

  • monoclonal antibodies
  • recombinant proteins
  • plasma-derived products
  • vaccines
  • medical devices
  • cell therapy products
  • animal-derived products (extracted from tissues or organs)
  • a host of other process products

Steps Associated with a Viral Clearance Process

Inactivation Steps

  • Low or High pH
  • Solvent/Detergent
  • Heat Treatments (HTST), Dry Lyophilization and Heat Treatment
  • UV Treatment
  • High Pressure
  • Enzymatic Digestion
  • Chemical Treatment (H2O2, Betapropiolactone, etc.)
  • Gamma Irradiation

Removal Steps

  • MabSelect/Protein A
  • Anion/Cation Exchange Chromatography
  • Mixed-Mode Chromatography
  • Hydrophobic Interaction Chromatography
  • Virus Removal Filtration
  • Ethanol Precipitation

Texcell has experience with all of these viral clearance processes.

Typical viruses used in viral clearance studies include:

  • RNA-enveloped (HIV-1, XMuLV, EMuLV & BVDV)
  • RNA-non-enveloped (Reo 3, HAV& Polio)
  • DNA-enveloped (Pseudorabies & HSV)
  • DNA-non-enveloped (PPV, MMV & SV40)

Texcell routinely provides these viruses in titers in excess of 108 pfu/mL or TCID50/mL. Below is the list of viruses available at Texcell. Since we currently increase the number of viruses, do not hesitate to ask for another.

List of available viruses:

Virus Family Origin size (nm) Genome Genome 2 Env Method
Adenovirus type 5 Adenoviridae Human 70-90 DNA Dble Naked Very high
Bovine viral diarrhea virus Flaviviridae Bovine 45-55 RNA Single Env Low
Encephalomyocarditis virus Picornaviridae Murine 28-30 RNA Single Naked Medium
Equine rhinovirus Picornaviridae Equine 28-30 RNA Single Naked Medium
Feline Calicivirus Caliciviridae Feline 30-40 RNA Single Naked Medium
Hepatitis A virus Picornaviridae Human 28-30 RNA Single Naked High
Human Immunodeficiency virus 1 Retroviridae Human 80-100 RNA Single Env Low
Influenza A virus (H1N1) Oorthomyxoviridae Human 80-120 RNA Single Env Medium
Influenza virus H3N8 Oorthomyxoviridae Equine 80-120 RNA Single Env Medium
Moloney Murine Leukemia virus Retroviridae Murine 80-100 RNA Single Env Low
Minute virus of mice Parvoviridae Murine 18-26 DNA Single Naked Very high
Parainfluenza 3 virus Paramyxoviridae Human 150-300 RNA Single Env Low
Poliovirus Sabin 1 Picornaviridae Human 28-30 RNA Single Naked Medium
Porcine parvovirus Parvoviridae Porcine 18-26 DNA Single Naked Very high
Pseudorabies (Aujeszky) HerpesViridae Porcine 150-200 DNA Dble Env Medium
reovirus type 3 Reoviridae Human 60-80 RNA Dble Naked Medium
Simian virus 40 Polyomaviridae Simian 45-100 DNA Dble Naked Very high
Transmissible gastroenteritis virus Ccoronaviridae Porcine 80-120 RNA Single Env Medium
West Nile Virus Flaviviridae Human 40-50 RNA Single Env Low

The virus stocks that we produce for spiking experiments are well characterized and optimized for each kind of step to be evaluated:

  • Particular care is taken with the protein concentration of the viral stocks used when validating nanofiltration steps; it must be as low as possible in order to avoid membrane clogging.
  • Aggregates must be removed prior to use of a virus stock for the validation of a nanofiltration step. We have developed a dedicated purification step to greatly reduce the contamination of cell DNA and HCP in the stock used for spiking experiments.
  • For strong inactivation steps (NaOH 1N, autoclaving, etc.), we select the viral stocks that have the highest titers. This allows achievement of a high LRV, provided that no infectious particles are recovered following the treatment.

Texcell uses a diverse array of assay end point detection methods to evaluate the efficiency of your viral clearance process. These methods include in vitro assays for infectious particle detections as plaque assay and TCID50, and moreover when it is important to distinguish between viral elimination and viral removal qPCR detection.

Furthermore, whenever we do not recover any viral particles following treatment of the fraction of interest, calculation of the Log Reduction Value (LRV) is performed using statistics based on Poisson’s Law. In such an event, it is possible to carry out a large volume titration (LVT) in order to lower the detection limit and hence increase the LRV. When possible, maximizing the LRV is our top priority.

Texcell follows all pertinent regulatory guidelines supported by ICH to perform these viral clearance studies.

Texcell notably uses the well-characterized 263K scrapie strain for TSE Clearance studies. The Western Blot assay is used in TSE detection.