A robust and efficient alluvial filtration method for the clarification of adeno-associated viruses from crude cell lysates

Adeno-associated virus (AAV) based vectors have recently been gaining importance as DNA delivery systems. Efficient downstream processing of AAV remains a major challenge as serotypes differ in physicochemical properties, making it difficult to design uniform purification processes. Clarification of AAV is an especially critical step. Harvesting of AAV, like other viruses, often requires cell lysis, resulting in a difficult-to-filter cell lysate. In this study, we evaluated the applicability of diatomaceous earth (DE) as a filter aid for clarification of AAV crude cell lysates. DE filtration proved to be a viable clarification method for AAV2, AAV5 and AAV8. Based on a design of experiment approach, the DE concentration was identified as the main factor influencing AAV particle loss. The loss of AAV during DE filtration was limited to < 2% by maintaining the DE quantity below 0.181 mg DE/1010 AAV. Use of DE reduced manual handling time 3-fold and increased the filter capacity 3.5-fold compared to filtration combined with a prior centrifugation step. Moreover, we showed that the DE type had only a minor influence on the filtration performance. This study demonstrated that filtration with DE as a filter aid is an efficient clarification method for different AAV serotypes.