Adeno-associated viruses (AAVs)

Significance of the Topic

Adeno-associated viruses (AAVs) represent a critical vector platform in gene therapy, offering targeted delivery of genetic material to correct monogenic disorders and develop novel vaccines. Their biophysical stability, low immunogenicity, and safety profile make comprehensive analytical characterization essential to ensure product quality, efficacy, and regulatory compliance.

Objectives and Article Overview

This application note outlines a complete workflow for AAV analytics, focusing on separation of empty and full capsids, aggregate determination, viral titer assessment, and peptide mapping. It demonstrates how different chromatographic modalities—strong anion-exchange (SAX), size-exclusion (SEC), and reversed-phase liquid chromatography (RPLC)—address critical quality attributes in AAV manufacturing.

Methodology

• SAX Chromatography: Utilizes a 3 µm ProPac 3R SAX column (2×50 mm) with linear salt gradients to resolve empty and genome-filled capsids. Fluorescence detection (Ex 280 nm/Em 330 nm) quantifies capsid ratios for AAV1, AAV6, and AAV8 samples spiked at defined empty:full ratios.
• Size-Exclusion Chromatography: Employs SurePac Bio 550 SEC MDi columns packed with 3 µm monodisperse silica particles to separate monomeric AAV from high-molecular-weight species and determine viral titer reproducibly using UV and fluorescence detection.
• Reversed-Phase Peptide Mapping: Implements Hypersil GOLD Peptide columns (1.9 µm, C18) for high-resolution peptide separations, enabling post-translational modification analysis and host-cell protein profiling when coupled with high-resolution mass spectrometry.

Used Instrumentation

• Vanquish Flex Quaternary UHPLC System
• Vanquish Fluorescence Detector (Ex 280/Em 330 nm)
• Vanquish Variable Wavelength Detector
• Orbitrap Exploris 240 Mass Spectrometer

Main Results and Discussion

The ProPac SAX column achieved baseline separation of empty and full AAV capsids with high resolution and reproducibility across serotypes. The SEC MDi column distinguished monomers from aggregates and impurities, facilitating accurate titer measurements. Peptide mapping workflows delivered consistent retention and resolution of hydrophilic and deamidated peptides, supporting in-depth viral protein characterization.

Benefits and Practical Applications

• Robust separation of empty/full capsids ensures dosage accuracy and efficacy.
• Accurate aggregate and impurity profiling supports safety assessments.
• High-resolution peptide mapping enables critical quality attribute monitoring and immunogenicity risk mitigation.

Future Trends and Potential Applications

Advances in particle technology and chromatographic media are expected to further enhance throughput and sensitivity. Integration with microfluidic platforms and automation, as well as coupling with advanced mass spectrometry, will drive deeper insights into AAV heterogeneity and host-cell protein contaminants.

Conclusion

This workflow demonstrates a unified analytical strategy for comprehensive AAV characterization. By combining SAX, SEC, and RPLC-MS approaches on monodisperse particle-based columns and high-performance instrumentation, the platform meets the stringent requirements for gene therapy product development and quality control.