Frequently Asked Questions - Bioprocess Monitoring

For virus concentration, detection, and quantitation of large and small-volume test articles, the test article supernatant is concentrated by either ultracentrifugation and direct pelleting or by sucrose density gradient purification and ultracentrifugation.

The concentrated test article to be quantitated is prepared by mixing a known concentration of latex spheres and the unknown number of virus particles from the test article. This mixture is mounted onto grids, negatively stained, and examined in the transmission electron microscope. Both latex spheres and virus particles are enumerated, and the concentration of virus particles in the test article is determined by using ratio formulas.

Test articles from cell banks and production seed stocks are prepared for ultra-thin sectioning, following standard written protocols, and are then examined for the presence of virus or other microbial contaminants in the transmission electron microscope at high magnifications.

This assay allows for the determination and identification of viruses present within, or secreted from, the cells used to produce biopharmaceuticals.

The final results include six-to-eight high-magnification electron micrographs, which are photographed and labeled according to the final results obtained.

The final report includes complete documentation of all assays, techniques, procedures, references, and calculations utilized in performing these services. Also included in this report is a precise, interpretive summary of the final results obtained.