One example of human-derived material is plasma. Despite the screening of blood donations, when a product is being manufactured from human plasma, there is potential for contamination by pathogens such as hepatitis and human immunodeficiency virus (HIV).Additionally, many biological drugs are manufactured in Chinese hamster ovary (CHO) or murine cell lines. With these cell lines, it is rare for viruses to be absent. While these materials are well characterized and screened for viruses in advance, the cells commonly contain endogenous viral contamination, typically in the form of a retrovirus. This virus is detected and quantified using transmission electron microscopy as part of the bulk-harvest testing.
This risk is not limited to biopharmaceutical materials. Even products falling into the medical-device category can be affected, such as collagen preparations. Collagen is derived from animal tissues; therefore, there is a high probability that a viral pathogen may be present.
Viruses may also enter the process or product by adventitious means. For instance, a contaminated raw material may be introduced into the process, or viral contamination could have entered the cell culture from a human operator.