The Use of dPCR Assays for VCN and Ratio of Full to Empty Capsids and Viral Titer in Lentiviral Gene Therapy Products
Precision and accuracy are paramount in the rapidly evolving field of gene therapy. A biotech company recently developed a gene therapy product using a Lentivirus Vector. To ensure the effectiveness of this product, it was crucial to determine the transfection efficiency and the quantity of viral vectors used for gene therapy delivery. This required the development of assays for vector copy number (VCN) and viral titer and determining the total to empty capsid ratio.
One of the significant challenges faced during this research was the development of sensitive and accurate viral titration and VCN assays. Traditional qPCR methods often fell short due to their susceptibility to inhibitors and lower sensitivity. This led the research team to explore digital PCR (dPCR) as a potential solution, offering a promising path forward in gene therapy research.
Development of dPCR Assay for Viral Titer
Developing a dPCR assay for Viral Titer was a pivotal aspect of the research. This assay enabled the precise determination of the concentration of infectious particles in samples, which is critical for optimizing the viral dose for gene therapy. The assay utilized primers and probes targeting integrated copies of the Reverse Response Element (RRE) in the target, with primers and probes for RNase P serving as a control for normalization.
Development of dPCR Genotyping Assay for Vector Copy Number
Another significant achievement was the development of a dPCR genotyping assay for Vector Copy Number. This assay allowed the quantification of viral vectors and the assessment of the total to empty capsid ratio. The assay employed multiple primers and probes specific to the vector and insert (FAM and VIC), with primers and probes for RNase P used as endogenous reference targets. Each reaction was designed with 100-200 ng of genomic DNA, and the endogenous reference target measured the number of diploid genomes. The outcome was determining the number of copies per microgram of genomic DNA and the ratio of total to empty capsids.
The successful development of these dPCR assays represents a significant advancement in gene therapy. By overcoming the limitations of traditional qPCR methods, these assays provide a more accurate and sensitive means of determining viral titers and vector copy numbers. This, in turn, enhances the ability to optimize viral doses for gene therapy, ultimately contributing to more effective and reliable treatments.