Adventitious Virus Testing

What is Adventitious Virus testing and why is it important?

Adventitious agents such as viruses have the potential to contaminate and be amplified within the biomanufacturing processes. Such contamination has a number of entry points, from being introduced with raw materials, to events at final packaging. However, the highest risks come from raw materials of a biological origin (such as serum), and from amplification within the bioreactor. As there is the potential for these adventitious viruses to cause serious harm to patients, all manufacturers must adhere to strict GMP guidance and regulations to ensure that viral risk is mitigated.

Traditional adventitious virus detection strategies use assays such as cell-based in vitro detection as well as in vivo models. The perceived advantage of these tests is that they can screen for both known as well as unknown viruses. However, the assays depend on the contaminating virus being able to amplify and have a demonstrable effect to allow for detection. Unfortunately, many viruses do not amplify within these systems. Further, some do amplify but do not cause any measurable effect on the cells or animals. As these methods can take weeks, or even months, they are often the pacing item for a batch to be released to the patient.

Another major drawback of in vivo and in vitro based detection is the compatibility of the test with the biopharmaceutical itself. If the drug has some toxicity, this can usually be dealt with by using a neutralizing antibody. However, such antibodies take many months to generate. Sometimes it is not even possible to generate a neutralizing antibody, making in vivo and in vitro testing impossible.

Molecular detection methods are typically insensitive to toxicity from the biologic to be tested, avoiding the need for a neutralizing antibody. These methods also tend to consume a lot less of the precious product. PCR is a common and highly sensitive test which is used to detect known and well characterized viruses. However, PCR will not detect viruses which are unknown, and may also struggle to detect known viruses where a genetic alteration has occurred. Dozens of PCR tests may also be required, consuming a lot of your precious product.

Using NGS as an approach for the detection of adventitious virus has a number of advantages. Like PCR it is insensitive to any potential toxicity. However, unlike PCR, NGS can sensitively detect both known as well as unknown or variant viruses. NGS is therefore an ideal viral detection strategy if there is an issue with antibody neutralization, or if speed and sample volumes are of particular concern.