(46g) Virus Flocculation and Removal in the Presence of Osmolytes
In this age of modern medicine, viral diseases continue to take the lives of millions of people. The most effective method to prevent viral infections is vaccines. However, there needs to be an improvement in current manufacturing virus purification processes to efficiently produce new viral vaccines. In this study, we use virus flocculation in the presence of osmolytes, followed by microfiltration as an alternative purification method to chromatography. Osmolyte flocculants are natural compounds found in cells, with their main functions being to stabilize intracellular proteins and maintain cell volume. They accomplish these functions by preferential interactions with water molecules. We hypothesize that osmolytes are able to specifically flocculate hydrophobic virus particles by depleting the hydration layer around the particles and subsequent virus aggregation. Using high throughput screening, we have discovered that a variety of osmolytes, including sugars, sugar alcohols and amino acids, flocculate the non-enveloped porcine parvovirus (PPV) and the enveloped Sindbis virus, and demonstrate a >80% removal with a 0.2 μm filter. Removal and purification of a virus with a micropore filter, which is usually used for bacteria removal and not for small viruses, will increase the flux and decrease the transmembrane pressure found in traditional virus filters.
The osmolytes that achieved the highest percent removal were tested for their ability to aggregate and flocculate virus particles at different concentrations, pH, ionic strengths and temperatures, and optimal conditions within our system were determined. We were able to remove 96% of PPV in 3.0 M glycine at a pH of 5 and 85% of SINV in 0.3 M glycine at a pH of 6. Removal of bovine serum albumin (BSA) and lysozyme was very low in the presence of alanine and mannitol, indicating that osmolytes will likely not flocculate host cell proteins. Osmolyte flocculation is specific to virus particles, making this a method to purify virus particles. We propose to use virus flocculation with osmolytes, followed by microfiltration, as a potential platform approach for virus purification that can be applied to many types of viruses with minor modifications per strain. Many of the osmolytes used are known adjuvants for vaccine products, and therefore may not need to be removed from the final product. Osmolyte flocculation is an improvement in viral vaccine purification that could greatly reduce the time to market and cost of development of future vaccine products.