Real-Time Viral Infectivity Assays That Replace Plaque and TCID50 Methods
Modern vaccine production is generally accomplished using live viruses throughout the research, development, and manufacturing processes. At each of these stages, analytical monitoring of viral infection is important to help ensure predictable infection and expansion, maximum yield, and safety parameters, especially for cell culture based processes. Similar potency and infectivity monitoring is critical in AAV Transduction for gene therapy, where Radiance® provides real-time insights into viral vector production. The potency of a live virus vaccine (LVV) is one of the most critical measurements of efficacy. Existing methods to measure viral vaccine potency include plaque and TCID50 assays, both of which have very long lead times, variability due to subjectivity, and cannot provide real-time viral titers across large-scale vaccine manufacturing.
Traditional TCID50 assays can take up to 10 days to deliver results, delaying critical manufacturing decisions. Radiance® provides real-time potency insights, eliminating the need to rely on historical averages or overformulation due to delayed analytics. By delivering accurate and precise viral titer measurements at fill‑and‑finish, Radiance® enables manufacturers to establish reliable shelf life and often produce more product with the same cost of goods.
Setting up regulatory assurance and compliance from the start is essential in vaccine manufacturing. By adopting advanced viral titer analytics early in development, manufacturers establish alignment with regulatory expectations while ensuring consistent vaccine quality, efficacy, and patient safety. This proactive approach strengthens process control and supports reliable outcomes across clinical, scale‑up, and commercial production.
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Monitoring Viral Infectivity and Viral Titer with Radiance®
Some vaccines are manufactured using viral vectors such as adenovirus, vesicular stomatitis virus (VSV), or measles virus. Incorporating additional genes in these vectors can result in poor infectivity rendering them ineffective for drug or vaccine development. Therefore, it is important to rapidly screen the infectivity of candidate viruses, which can be a tedious and time-consuming task when relying on traditional infectivity assays. In contrast, Radiance® can quickly assess the infectivity of recombinant adenovirus after as little as 24 hours of incubation with the target cells. Production can be monitored using Radiance® via sequential aliquots or through continuous monitoring of the infection and production process.
Radiance® is also used to verify viral inactivation by demonstrating a lack of infectivity, supporting both R&D and manufacturing teams with rapid viral titer analysis. Radiance® applies across multiple viral platforms, including 50+ viruses, including adenovirus, VSV, measles, and influenza. This breadth ensures manufacturers can rapidly screen infectivity across diverse vaccine candidates, reducing risk of ineffective formulations.
For example, measles vaccine manufacturing highlights the importance of viral potency testing to ensure consistent immune response. A recent study on measles vaccine production underscores how accurate and precise viral potency assays are critical for reliable manufacturing outcomes. Radiance® provides a faster, real-time alternative to traditional potency assays, reducing delays and improving viral infectivity precision.
Radiance® as an Advanced Viral Potency Assay Solution
Rapid and Precise Viral Potency Assays
Faster viral infectivity and titer assays
Correlation with plaque and TCID50 assays
Absolute infectivity measurements without correlation requirements
Real-time bioreactor assay results in minutes
High-quality potency data with unmatched precision and reproducibility
Radiance® advances viral potency assays by combining speed with precision, delivering actionable results in minutes instead of days. This dual advantage enables manufacturers to scale efficiently, generate more product at the same cost of goods, and strengthen overall process reliability.
Accurate, precise potency assays also reinforce shelf life and stability testing. By avoiding overformulation, manufacturers reduce waste, improve efficiency, and lower cost of goods while ensuring consistent vaccine effectiveness and quality.
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Options for Viral Infectivity Assay Implementation
Relative Response Infectivity Assay
- Use existing knowledge or collect new data to establish a relationship between Radiance® response and viral infectivity (Radiance® Infection Metric)
- Use Radiance® Infection Metric moving forward to compare viral samples or conditions
- Immediate use for known virus/cell systems
- 1-2 experiments to finalize metric for new biological systems
Absolute Viral Titer Assay
- Standalone method for titering unknown viral sample
- Infect cells with 7-9 dilutions and analyze with Radiance®
- Can use dilution results to also establish calibration curve
- Immediate use for known virus/cell systems
- 1-2 experiments to finalize metric for new biological systems
Calibration Curve for Viral Potency Assays
- Correlation between infection metric and reference viral titer
- Uses minimal dilutions across a wide range of viral concentrations
- Measure reference same titer using Radiance® absolute titer method
- Use result to create calibration curve (MOI vs. infection metric)
- Curves are robust and can be used across viral strains, GOI, and process changes
- 3-5 experiments to establish curves and viral concentration range
Radiance® delivers real-time data insights as a cellular Process Analytical Technology (PAT), seamlessly integrating into robust manufacturing frameworks, enabling continuous monitoring and real-time decision support across vaccine clinical manufacturing and commercial scale up. Radiance® strengthens and adds to a robust process and quality control strategy ensuring regulatory expectations for modern biologics production are met.
Building Vaccine Reliability from the Cell Bank Up
Every vaccine begins with a robust cell bank qualification strategy. Strong, viable cells are the foundation for consistent viral yields, making cell bank analysis a critical step in reliable vaccine production. Traditional viability assays only confirm whether cells are alive at a single point in time—alive today but potentially non‑viable tomorrow.
Radiance® advances this process by offering predictive cell bank qualification, measuring forward‑looking vitality to ensure cells can sustain production over time. This predictive insight reduces batch failure risk, supports consistent viral potency outcomes across vaccine manufacturing runs, and strengthens overall process reliability.
By placing emphasis on robust cell bank qualification, manufacturers establish confidence in their starting material and safeguard downstream vaccine quality, scalability, and yields. Predictive cell vitality is fundamental to any cell based process or production workflow, ensuring that cell banks and cellular starting material are set up for success from the very start. Whether in vaccine manufacturing, CAR T, or stem cell–based therapies, success depends on cell banks capable of sustaining the yields necessary for both vaccine and advanced therapy development.
Harness Radiance® to Drive Speed and Precision into Vaccine Potency Testing and Manufacturing
Harness Radiance® for real-time viral potency testing, predictive cell bank qualification, and broad assay applications—accelerating vaccine development, improving accuracy, and increasing efficiency.
