"A Novel and Rapid Technique for Virus Titer and Protein Aggregation Assessment"
NanoSight has developed a new technique which is gaining much interest in the area of viral vaccine development and phage therapeutics. The technique can image the light scattered from viruses in solution and can calculate their size by tracking their Brownian motion on a virus-by-virus basis, viruses as small as 25 nm can be imaged. This provides the accurate number/size distributions of a virus preparation that are essential information in understanding the efficiency of virus purification. Measurement of monomer vs. aggregates at each step of the purification process can be determined as well as a total viral count. Applications include:
- Measurement of total viral titer (live and inactivated) and state of aggregation in a viral vaccine, in real-time and directly in liquid suspension.
- Fluorescent labeling of viruses to allow discrimination of virus material from cell debris or growth medium.
- Measurement of the state of aggregation in recombinant protein vaccines.
- Measurement of size and concentration of a Virus Like Particle (VLP) preparation.
- Size determination of adjuvants.
In live attenuated vaccine the total viral count provided by NanoSight can be used in combination with information from infectivity assays to estimate the infectious viral titre vs. the total viral titre. It is often found that the infectious viral titre may be as little as 0.1% of the total viral count. This results from viruses becoming inactivated in the purification process, poor binding affinity in plaque assays or aggregation in the virus preparation. As such measurement of the infectious viral titre vs. total viral titre is value information; if this ratio can be improved then clearly you can more effectively produce a final product.
For inactivated vaccine, the total viral count as provided by NanoSight becomes essential when determining the immune response to the final product, where infectivity assays cannot be used. In addition the technique produces real time movie files of the viruses in solution and as such, time dependant phenomena can be studied both qualitatively and quantitatively. This may be important when trying to understand the stability of your product with changes in temperature, solution pH or time related changes in the product by addition of surfactant or dispersing agents. Particle count and size distribution are essential measurements when trying to study such events. Other potential applications include staining of viral DNA to discriminate between filled and empty capsids.