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Some cell lines, such as rodent cells, harbor endogenous retroviruses. The retroviral particles must be quantified on three lots of unprocessed bulk to establish levels of viral clearance that need to be achieved. Traditional methods for viral particle counting include transmission electron microscopy (TEM) evaluation of supernatants. BioReliance offers a Quantitative PCR approach to particle counting in unprocessed bulk fluids and cell banks, with advantages such as considerably shorter turnaround times and higher sensitivity.
The regulatory authorities have raised concerns over the risks that may be associated with residual host cell DNA. There is a possibility that residual host cell DNA, if present in sufficient amounts, could transmit genetic information to patients receiving the product. The associated risks include: malignant transformation by activated cellular and/or viral oncogenes, aberrant gene expression by insertion of sequences in sensitive control regions of genes, and the production of infectious viruses from viral DNA. As a consequence, the regulatory authorities state that manufacturers of biopharmaceuticals should quantify the amount of residual DNA in final products manufactured from continuous mammalian cell lines. Initially, the recommended amount was less than 100pg of host cellular DNA per dose, with testing procedures that can detect 10pg (FDA, 1997). However, a more recent assessment has concluded that levels of up to 10ng of host cellular DNA per dose can now be considered acceptable (WHO, 1998). In response to these concerns, and in accordance with the regulatory guidance, BioReliance has developed a range of Quantitative PCR (Q-PCR) assays for specific cell lines, which are designed to detect and quantify residual host cell DNA. The Q-PCR assays can accommodate a wide range of samples, including those that could contain inhibiting substances.
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