Viral Vector Downstream Processing

Viral vector purification processes have historically been based on systems used for monoclonal antibodies, which are not designed to deliver the necessary level of recovery.

The introduction of new technologies specifically designed for gene therapy viral vector downstream processing offers the opportunity to increase yield and throughput. Among the approaches that can be leveraged to optimize viral vector downstream processing include:

  • Ultrafiltration/diafiltration operations, particularly with the use of tangential flow filtration (TFF) for cell or viral harvesting and purification, downstream protein concentration and diafiltration, as well as in final formulation
  • Intensified chromatography processes that reduce the number and size of unit operations, via technologies such as high-productivity, single-use chromatography membrane adsorbers

These downstream technologies offer the potential to reduce viral vector purification times from hours to minutes, while improving recovery. In addition, they can facilitate scale-up, reduced the process footprint, and enable more efficient facility utilization.

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Primary Clarification

The crude medium containing viral vectors is depth filtration or a combination of both centrifugation and depth filtration to remove large cellular debris and other contaminants.

Secondary Clarification

Clarified medium from the primary clarification is further purified through additional steps.


Ultrafiltration and diafiltration are used for concentration and buffer exchange, respectively. The viral vector is separated from impurities using size-based filtration. Diafiltration removes salt and other molecules, replacing with the buffer of choice.


At least two chromatography methods are used to purify the viral vector including ion exchange, affinity and size exclusion.

Virus Filtration

The purified viral vector is subjected to nanofiltration with 15 nanometers pores to remove adventitious viruses, endotoxins, and any other remaining impurities and aggregates.

Sterile Filtration

Sterile filtration, or bioburden reduction, can be used multiple times in the process. The feed stream is passed through a 0.4 or 0.2 micron sterilizing grade filter to remove bacteria and other microorganisms that have been introduced during the processing.

Final Fill

The purified and sterile viral vector is filled into the final intended container. Careful considerations need to be given here for formulation, packaging materials, storage condition to ensure stability and integrity.

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