AAV Physical Titer

In AAV vector production, one of the most essential steps is determining the physical titer — a key metric that reflects the quantity and quality of the viral preparation. There are two main types of physical titers.  At AAVnerGene, we help clients distinguish between and accurately measure both:

  • Genomic titer (vector genome titer)

  • Capsid titer (total particle count)

Understanding the difference is critical for gene therapy development, regulatory compliance, and dose optimization.

AAV Genomic Titer

Genomic titer refers to the number of AAV particles that actually carry the therapeutic DNA — the vector genome (VG). It tells you how many functional, genome-loaded particles are in your prep.

✅ Why it matters:

  • Reflects functional dosing of gene therapy vectors

  • Used to compare productivity across constructs or batches

  • Essential for calculating full-to-empty ratios

🔬 How we measure it:

  • qPCR (quantitative PCR) using a transgene-specific primer (e.g., WPRE, ITR, promoter)

  • ddPCR (droplet digital PCR) for absolute quantification and better precision

  • Primer sets are carefully validated to avoid false reads due to truncated or rearranged genomes

AAV Capsid Titer

Capsid titer quantifies total AAV particles, regardless of whether they contain a genome. It reflects the number of physical viral shells present in the solution.

✅ Why it matters:

  • Helps calculate full-to-empty ratios, a critical QC parameter

  • Useful for comparing packaging efficiency across serotypes

  • Required for determining immunogenic burden (especially in clinical settings)

🔬 How we measure it:

  • ELISA using antibodies against conserved AAV capsid proteins (e.g., VP1/2/3)

  • Can be applied to multiple AAV serotypes

  • Often paired with genomic titer to assess vector quality

Bringing Genomic and Capsid Titers Together

The full-to-empty ratio is derived by comparing genomic and capsid titers:

Full-to-Empty Ratio=Genomic Titer (vg/mL)/Capsid Titer (vp/mL)

This ratio reveals how efficiently your AAV particles are being packaged with the intended genome. A low ratio may indicate:

  • Packaging inefficiency

  • DNA toxicity

  • Incorrect plasmid ratios

  • Vector genome overloading

AAVnerGene's Expertise in Titering

At AAVnerGene, we provide end-to-end AAV quantification services:

🔹 Genomic Titering

  • qPCR and ddPCR platforms

  • Custom gene-specific primers

  • Internal controls and standard curves

🔹 Capsid Titering

  • AAV universal or serotype-specific ELISA kits

  • Cross-validated with reference AAV standards

🔹 Full/Empty Particle Analysis

  • Optional mass photometry or CD-MS available 

Whether you’re running small-scale tests or preparing for clinical translation, our titering services are designed for precision and scalability. We support a wide range of capsids, custom vectors, and assay formats — backed by years of AAV expertise.

Why Accurate Physical Titering Matters

Accurate and reproducible physical titers allow you to:

  • Dose precisely in animal models or clinical trials

  • Monitor vector quality across production lots

  • Troubleshoot low-yield constructs

  • Meet regulatory expectations for GMP and IND filings