Enveloped virus-like particles purification using an all-filtration technology platform

Virus-like particles (VLPs) have become widely used as vaccine candidates because of their versatility, immunogenicity and safety profile. The diversity of surface epitopes contributes, however, to a variability in downstream purification that could ultimately affect manufacturability. For baculovirus expression systems in particular, the similarity between residual baculovirus and VLP particles causes significant problems. For that purpose, we have undertaken an effort to develop platform processes for purification of VLPs. Our initial approach focus on size exclusion as the key mechanism of separation, with the ultimate goal of an all filtration purification process, inserted in the “anything but chromatography” concept. The first step was to evaluate a legacy purification that was not robust or efficient and replace the ion exchange chromatography step with size exclusion chromatography (SEC). Performance of the SEC step will be described and the shortcomings of such a method for a scaled up, GMP process will be discussed. The proposed all-filtration process employs either normal or tangential flow filtration for the clarification stage, followed by a cascade of ultrafiltration steps with different pore sizes and a sterile filtration step to achieve the needed concentration and purity specifications. Efforts to clear nucleic acid without the use of an endonuclease digestion step and the impact on the downstream unitary operations will also be described. By optimizing the filtration mode of operation we were able to achieve product recoveries above 85%. Globally, we have about 90% of DNA and total protein removal and a baculovirus’ log reduction value of 6. Using this all-filtration platform we are able to speed up the process, to improve the scale-up and to reduce costs due to the removal of chromatographic steps. To show the potential for a universal, platform process, two cell systems producing two different VLPs were studied and preliminary results will be presented