Characterization of a recombinant adeno-associated virus type 2 Reference Standard Material

Area of Science:

• Biotechnology
• Gene Therapy
• Virology

Background:

• Accurate quantification of adeno-associated virus (AAV) vectors is crucial for gene therapy efficacy and safety.
• Existing methods for determining AAV vector titers exhibit significant interlaboratory variability.
• The development of standardized reference materials is essential to improve consistency in AAV vector characterization.

Purpose of the Study:

• To produce and characterize a recombinant adeno-associated virus serotype 2 Reference Standard Material (rAAV2 RSM).
• To establish reliable reference values for particle, vector genome, and infectious titers of AAV2 vectors.
• To assess interlaboratory variability in AAV vector quantification assays.

Main Methods:

• Production of rAAV2 RSM using helper virus-free transient transfection.
• Purification of the rAAV2 RSM via chromatographic methods.
• Distribution of the rAAV2 RSM to 16 international laboratories for characterization using standardized protocols and reagents.
• Statistical analysis of quantitative data to determine mean titers and confidence intervals.

Main Results:

• Characterization yielded mean titers for capsid particles (9.18 x 10¹¹ particles/ml), vector genomes (3.28 x 10¹⁰ vg/ml), transducing units (5.09 x 10⁸ TU/ml), and infectious units (4.37 x 10⁹ IU/ml).
• Purity of the rAAV2 RSM was confirmed to be greater than 94% for non-vector proteins.
• Significant interlaboratory variation was observed across all assays, despite standardization efforts.

Conclusions:

• The rAAV2 RSM provides a valuable tool for calibrating laboratory-specific standards and improving AAV2 vector quantification.
• The study highlights substantial interlaboratory variability, underscoring the urgent need for universally accepted reference standards in AAV research.
• The rAAV2 RSM is available through the American Type Culture Collection to support the scientific community.