Viral vector and plasmid development for cell and gene therapy



As demand for cell and gene therapy continues to increase, so too does the demand for viral vectors and plasmid DNA development. Gene and cell therapies utilize a variety of viral vectors for gene transfer, including adeno-associated viruses (AAV), lentiviruses, retroviruses, herpes viruses, adenoviruses, and others. Among them, AAV-mediated gene therapy is garnering the most interest due to its safety profile since infection with the vector is not pathogenic, and AAV cannot replicate on its own.  The AAV viral vectors, as well as the messenger RNAs produced from plasmid DNA template, are the critical intermediates that produce and carry the chimeric antigen receptor (CAR) to T-cells enabling CAR-T therapies.

Accurately measuring viral titer in gene therapies

Controlling the concentration of a potential therapeutic is difficult since viral particles are produced in living cells and then purified.  The process of generating and purifying viral vectors is also susceptible to contamination by host cell DNA, mycoplasma, and other contaminants.  Viral titer must be measured accurately, precisely, and consistently to ensure correct formulation.  Harmful adventitious agents (virus, bacteria, and fungi) and contaminant DNA must be detected and screened out with the highest sensitivity to ensure product quality and safety.

While real-time PCR remains the gold-standard tool for the quantitation of therapeutic viral vectors such as AAV used in cell and gene therapies, digital PCR (dPCR) offers significant advantages for quantification of target DNA molecules in a range of analytical assays necessary for viral vector production and characterization.

Unlike real-time PCR, dPCR can provide an absolute count of nucleic acids, enabling the precise quantification of AAV vectors, bacterial contaminants, and residual host cell DNA. No reference standard is required, improving precision and removing a source of variation. The variability in the standard curve used for real-time PCR is often due, in part, to the different architectures of the relevant DNA species: circular, supercoiled, linear DNA, or viral particles.  dPCR is also less sensitive to contaminants that affect amplification, including those present in solutions used during the development of AAV-mediated gene therapies.

Absolute Q Viral Titer dPCR assays

Applied Biosystems Absolute Q Viral Titer dPCR assays enable easy and accurate quantification of viral vectors. The assays can be run individually or multiplexed using a custom assay with your target gene of interest to measure concentration and evaluate quality for biopharma and gene therapy research.

Absolute Q dPCR assays are:

  • Simple—streamlined workflow for ease-of-use with your digital PCR instrument
  • Fast—minimal hands-on time; results in 90 minutes when used with the QuantStudio Absolute Q Digital PCR System
  • Dependable—analyze your data with confidence using verified assays backed by a performance guarantee*

We stand behind every predesigned Absolute Q dPCR Assay that you buy from us

We guarantee the performance of all of our predesigned Absolute Q assays for dPCR experiments. Our application‑specific portfolio of assays enables you to obtain the highest quality and performance available. These assays are designed and verified using up-to-date annotations and gold-standard Applied Biosystems TaqMan chemistry.

If an Absolute Q Digital PCR Assay does not perform according to conformance documentation, we will replace it at no cost or credit your account.*

Learn more about the Absolute Q dPCR Assay guarantee ›


Figure 1. Quantification of AAV and CMV viral vector dilution series on the QuantStudio Absolute Q dPCR System.


Figure 2. Quantification of AAV and CMV viral vector dilution series across multiple digital PCR platforms using the Absolute Q(TM) AAV and Absolute Q(TM) CMV dPCR Assays.

Custom designed assays

Can’t find the assay you’re looking for? Contact us and our experts can help design a digital PCR assay formulated for success based on your target sequence of interest. Or submit the primer/probe sequences of your own design.

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Complementary master mix

Absolute Q DNA Digital PCR Master Mix (5X) is optimized for use with the QuantStudio Absolute Q Digital PCR System and Absolute Q digital PCR assays in a simple workflow with minimal processing steps.  The 5X formulation enables analysis of higher sample volume and delivers accurate quantification of DNA targets without using a standard curve.

Key product features:

  • Fast time-to-results—five minutes of hands-on time and results in ~90 minutes
  • High sensitivity—detect down to 0.1% mutant allele frequency
  • Optimized for multiplexing—detect up to four targets in a single reaction

Ordering information

Absolute Q Viral Titer assays


Adeno-associated virus (AAV) ITR-2



Cytomegalovirus (CMV) promoter region



Absolute Q DNA Digital PCR Master Mix

*Terms and conditions apply. For complete details of the guarantee, go to