Why is it necessary to test for exogenous viruses?
In the biopharmaceutical R&D and production chain, the cell matrix serves as the core starting material and is fundamentally critical to the safety of the final product and its clinical application. Any contamination by exogenous viral factors directly compromises product efficacy and patient health, representing an unacceptable quality risk. Therefore, establishing and implementing a comprehensive exogenous factor detection system-covering the cell matrix, harvested fluid, and ultimately the final product-is not only a scientific necessity but also a strict regulatory compliance requirement mandated by global authorities.
Core Techology: In vitro seeding and culture methods for different cells
Different in vitro cell culture methods, owing to their classical and broad-spectrum applicability, have been adopted as core screening approaches by global regulatory guidelines, including ICH Q5A(R2), the Chinese Pharmacopoeia (2025 edition), the United States Pharmacopoeia, and the European Pharmacopoeia. The principle of these methods is based on the cytopathic effect (CPE) induced by viral proliferation in susceptible cells, combined with endpoint assays for hemadsorption (HAd) and hemagglutination (HA). This combination enables systematic detection of exogenous viral factors with infectious activity.
As global regulatory frameworks continue to evolve, the application of these methods demands increasingly scientific and refined strategies, which center on three core requirements：
1. Multi‑lineage Sensitive Cell Panel
To ensure broad detection coverage for human and related animal viruses, regulatory guidelines require a sensitive cell panel that includes: cell lines derived from the source species (e.g., CHO-K1, HEK293), human diploid cells (e.g., MRC-5), and monkey kidney cells (e.g., Vero). For specific production systems (e.g., insect cells), additional sensitive cell types, such as BHK-21 and Drosophila embryonic cells, should be included based on risk assessment.
2. Extended and Optimized Culture Observation Periods
To effectively detect slow‑growing or low‑level viral infections, regulations specify extended culture durations and regular subculturing. For example, for critical materials such as the Master Cell Bank (MCB) and Working Cell Bank (WCB), a 28‑day permissive cell culture test is required, with subculturing performed at least every two weeks.
3. Systematic Endpoint Detection Methods
The detection system requires continuous monitoring of CPE throughout the culture period, followed by simultaneous HAd and HA assays at the end of the culture period. These three methods are complementary: HAd detects viral proteins expressed on the surface of infected cells, while HA detects viral particles via agglutination of red blood cells in the supernatant. Together, they form a multi‑layered and complementary active virus screening system. It is important to note that different pharmacopoeias have varying requirements regarding the source and quality of red blood cells used in HA assays; strict adherence to the respective standards is therefore essential.
Depicted below is the trajectory of in vitro culture observation period requirements as they have evolved within major regulations-a trend that offers crucial direction for the systematic development of testing strategies:
The professional services we provide to you
We are not just a provider of testing services, but also a partner in your virus security strategy. Choosing us means choosing a reliable, globally compliant solution.
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Professional Services |
Comprehensive protection for you |
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Global Compliance and Reporting Support |
The testing system is deeply integrated with the requirements of major international pharmacopoeias such as the Chinese Pharmacopoeia, USP, and EP, as well as ICH guidelines, and has the compliance foundation and successful experience to support simultaneous declarations in multiple regions such as China, the United States, and the European Union. |
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Extensive product and sample coverage |
Our services cover a diverse range of biological products, including antibodies/recombinant proteins, cell and gene therapy products, vaccines, and key raw materials, and we have experience in testing across categories and throughout the entire process. |
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A complete cell bank and scientific program |
The stock includes cell lines from common sources (CHO-K1, 324K, HEK293 (and its derivative HEK293T), HeLa, CV-1, etc.), which can be used for targeted testing based on product origin and risk assessment, achieving broad-spectrum and precise screening. |
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Sufficient culture period and high sensitivity |
By strictly adhering to a 28-day culture and observation period, the validated method exhibits excellent sensitivity, effectively detecting low-level viral contamination and addressing the challenges of detecting complex sample matrices, such as unprocessed harvested liquids and final products. |
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A comprehensive endpoint testing system |
The blood adsorption test covers multiple red blood cell sources, including human type O blood, chicken blood, and guinea pig blood, and fully complies with the different requirements of pharmacopoeias in various countries, ensuring the reliability and compliance of the test results. |
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Rigorous methodological verification |
We conduct comprehensive methodological validation, including specificity, detection limit, and robustness, strictly in accordance with ICH Q2(R2), Chinese Pharmacopoeia (2025 edition), and other regulatory requirements. We have successfully provided product specificity (PSQ) validation for multiple marketed products, supporting all stages of application from IND to BLA. |
We stay abreast of global regulatory updates and leverage cutting-edge technology platforms, rigorous quality systems, and a team of experienced experts to provide comprehensive viral safety solutions for your biopharmaceuticals. We safeguard innovation with science and ensure safety with professionalism.
For testing solutions or to learn about Product Specificity (PSQ) verification services, please feel free to contact us.