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A physical method for the quantification of viruses and viral particles (L-11622)


Project TitleA physical method for the quantification of viruses and viral particles (L-11622)
Track CodeNRC no. 11622
Short Description

Recombinant viruses carrying foreign genes are commonly used as delivery vectors in gene therapies to treat various kinds of diseases. Inactivated or attenuated viruses are also routinely used in vaccination of patients. Quantification of the number of viral particles has always been a critical issue when injecting viruses for therapeutic or prophylactic reasons. Current methods are semi quantitative as they only measure the effects of the virus in an infected cell. This technology allows for the direct, simple and rapid count of the effective number of viruses or viral particles present in a sample. It targets the viral vectors manufacturing processes market.

Tagsphysical method, viruses, quantification method, viral particles, viral load, gene therapy, viral inoculation, monitoring, improvement, manufacturing processes, viral vectors, viral vaccines, product qualification, vaccines, diagnostic tool
Posted DateSep 20, 2007 9:04 AM


Amine Kamen


Yves Quenneville


Viral vectors are the most popular gene delivery vehicles in gene therapy studies and represent 70 % of the total clinical trials conducted worldwide. A great deal of effort has been dedicated in the past years to the advancement of manufacturing processes whereby methods to quantify viral particles played a major role (e.g. HPLC, spectrometry, ELISA, PCR, etc.). These methods allowed results to be obtained in a matter of minutes or hours thus facilitating the process development in comparison to the traditional titration assays taking several days to deliver results. However, these methods suffer from either their lack of specificity, sensitivity or are too cumbersome or too expensive to be routinely used in a manufacturing process. Still, accurate quantification of vector particles is critical in the design and execution of successful pre-clinical and clinical gene therapy trials and in the production of vaccines. Without a reliable and rapid quantification assay, processes cannot be developed further and optimized. This technology provides a method for detecting viral particles. It combines the use of a dye emitting fluorescence when intercalated in the viral nucleic acid molecule and of an HPLC system to separate and detect the fluorescent particles (see Figure). The labeling of the virus provides a greater sensitivity to the method while the HPLC permits an unmatched selectivity.

Potential Applications

•Quantification of viral load in gene therapy or viral inoculation.

•Monitoring and improvement of manufacturing processes of viral vectors for gene therapy and of viral vaccines.

•QA/QC: product qualification of viral vectors and vaccines.

•Diagnostic tool.

Features and Benefits

Direct quantitative method

The technology allows for the physical count of viral particles present in a sample. It addresses the need of the industry for a reliable quantification method and becomes an essential tool in manufacturing process development.

Selectivity and sensitivity

The selectivity of the technology is achieved by using an Ion Exchange HPLC (IE-HPLC) which physically separates viral particles thus avoiding measuring contaminant particles. The fluorescent intercalating dye plays a key role in increasing the sensitivity of the technology. Detection limits are as low as 2.5 x 106 for the AdV5 virus and 2.05 x 107 for the HDAdV virus. Such a sensitivity and specificity makes it possible to use the technology reliably and routinely in a manufacturing process QA/QC environment.

Rapid turn-around time

With an assay time of about 30 minutes, the technology is perfectly amenable to routine use in the development and optimization of manufacturing processes. Titration assays can take up to 48 hours to generate results and therefore are ill-adapted for such a use. In one case, the team was able to monitor the manufacturing process of an oncolytic virus, identify the steps where virus production was deficient, address the issues and increase the overall yield from 2% to 40%.


The technology is fairly flexible and can be used with different types of viruses (enveloped, non-enveloped) and accommodate different experimental conditions (permeabilization or no-permeabilization). The technology can therefore be adapted to the monitoring and improvement of the main manufacturing processes currently used in the industry.


File Name Description
L-11622 A physical method for the quantification of viruses and viral particles Download

Intellectual Property

Patent Number Issue Date Type Country of Filing None Other Patent Canada


A physical method for the quantification of viruses and viral particles