Viral Physical Titer Test

Viral titer is an important indicator of the product and technical services of virus-related products. In this context, physical titer is the concentration of viral particles that contain the viral genome. Creative Biogene has developed accurate and reproducible analytical tools to monitor the physical titer of viral vectors in its production strategy, ensuring safe, high-quality, consistent and effective products.

Introduction to Physical Titer

Physical titers include viral particle titer (or capsid titer) and genomic titer. Physical titers calculate the total number of live and dead viral particles present and are expressed as the number of viral particles per milliliter (VP/mL) and, for AAV, as the number of genomic copies per milliliter (GC/mL). AAV therapy clinical doses are often based on physical titer, so it is important to use accurate quality control methods to determine the amount of vector being administered. There are several methods for determining the physical titer of the virus based on viral genome or viral protein concentration.

Physical Titer Test at Creative Biogene

Physical titer can be measured by quantitative PCR for genomic copy number of viral particles or by measuring specific proteins in viral particles. Creative Biogene has integrated several advanced technologies for titer testing in the production of viral vectors. These methods have good specificity, sensitivity and rapid detection and are currently used in our laboratories to detect viral content, viral gene transcript levels or genomic copy number, and to calculate the titer of a sample based on a viral titer reference.

Physical Titer	Method
Viral particle titer	ELISA: Determination of AAV particle titers by color development through enzyme-catalyzed substrate reactions attached to AAV capsid-specific binding antibodies.
	TEM: The appearance of virus particles is more visually observed by transmission electron microscopy, and virus particles are quantified by direct counting.
	HPLC: This method can be used for quantitative analysis of viral vectors and can distinguish the content of empty and intact capsids in AAV products, and is applicable to various serotypes with high throughput of detection. It can accurately quantify several key quality attributes of viral vector products, such as titer, total protein concentration (Cp), purity/aggregation ratio, etc., in 15-30 min with a single injection, which is highly efficient, rapid and accurate.
	AUC: It has high reproducibility in quantifying different particle titer ratios and can effectively differentiate between intact and empty coat particles.
Genomic titer	Real-time PCR (qPCR, ddPCR): The most widely available method for detecting viral genomic titer. It is simple and convenient to operate, and has significant advantages in quantitative accuracy, sensitivity and stability.
Genomic titer	Spectrophotometry: The method is based on the selective absorption of light by substances and measures the light absorption of nucleic acids and proteins at 260 nm and 280 nm to quantify viral genome titer and capsid titer in a simple manner.

Creative Biogene is committed to establishing accurate and rapid physical titer tests during the production of viral vectors to optimize process development while ensuring the quality of gene therapy products. Please feel free to contact us if you have a need, and our experienced specialists will be happy to assist you.

* For research use only. Not intended for any clinical use.

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