Enveloped viruses have tremendous potential in a number of areas of great interest to biotech and pharma firms including gene therapy and vaccination. These viruses, which are typically produced in animal cell systems, are expensive to manufacture. As a result, identification of biological and engineering strategies that are scalable and cost-effective is paramount.
The complexity of these biological products, however, has hampered the development of robust downstream processes. Obtaining the quantities required for preclinical and clinical trials is especially problematic.The labile lipid membrane layer that harbors glycoproteins (often critical for infection) over the viral capsid further increases the challenges inherent in the processing of enveloped viruses.
Scientists at the Animal Cell Technology Unit of iBET are using recombinant baculoviruses as an enveloped virus model in order to optimize this task. Recombinant baculoviruses are widely used as vectors for the production of recombinant proteins in insect cells.
More recently, these viruses have been gaining attention due to their emerging potential as gene-therapy vehicles. While their production in stirred bioreactors using insect cells is an established technology, downstream processing of baculoviruses intended for clinical applications is only now catching up.
This article will discuss the evaluation of a scalable, cost-effective downstream processing strategy based on membrane processes. The evaluated process comprised three steps—depth filtration, ultra/diafiltration, and membrane sorption (Figure 1). Global recovery yields of clinical-grade material reached 40% using easy-to-scale-up technologies under cGMP guidelines. This constituted a major advance over the much lower yield and nonscalable purification process based on ultracentrifugation density gradients (Figure 1).