Viral safety is a key concern in the growing field of biologics produced by mammalian cells as viral contamination could have serious clinical consequences. Viral contamination can arise from different sources including but not limited to cell bank with latent or persistent virus infection, viruses expressed endogenously by the cells, raw materials, contaminated reagent from an operation unit such as affinity chromatography and handling. To ensure the safety of human therapeutics, it is not only important to understand the sources of viral contamination but also required by regulatory agencies to ensure prevention, detection and removal of such contaminants.<br/><br/>Retrovirus-like particles (RVLPs) are expressed endogenously by Chinese hamster ovary cells and are considered as one of the sources for viral contamination. As so, it is integral to biologic manufacturing to investigate the life cycle and to quantify the level of RVLPs throughout bioprocessing unit operations. Considering today’s industrial trend toward continuous bioprocessing, there is a need to carry out studies into the life cycle of RVLPs in newly developed solutions/unit operations. One such area of interest is perfusion bioreactor processes. Compared to traditional fed-batch approaches, perfusion mode provides a favorable environment to the cells by continuous metabolite removal and nutrient addition. Rapid removal of toxic byproducts along with continuous supplement of fresh medium enable achievement of high cell density within perfusion bioreactors. However, the impact of increased cell density on RVLP expression has not been studied. In this poster, we present our investigation on evaluating the level of RVLPs measured by RT-qPCR as a function of cell density in fed-batch and perfusion bioreactors. To the best of our knowledge, our study is the first direct comparison of retrovirus content between the two different modes of bioreactor operation.  This has implications for differences in the risk from therapeutics produced by each mode.

Evaluation of retrovirus-like particle expression in fed-batch and perfusion as a function of cell density

ACS Fall 2020 Virtual Meeting

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