A quantitative, DNA-based, real-time PCR approach to determine the number of lentivirus particles that are present in vector preparations was reported. In this approach, the minus strong-stop cDNA fragment that is present in viral capsids serves as template for PCR. Using this technology, it was found that only 0.1%–1% of the virus particles that are present in vector preparations are infectious.  The approach is rapid, reliable, and simple in concept and can be used to estimate both vector particles in supernatants and the number of infectious particles.  Also, this approach can easily be adapted to a highthroughput system by using 96-well plates and a 2-h running time.

Refer to “Quantitative Determination of Lentiviral Vector Particle Numbers by Real-Time PCR” in BioTechniques 2001; 31:520-526