Adeno-associated virus (AAV) is a well-established platform for gene delivery. It is crucial to ensure that AAV formulations are free from impurities that can compromise the efficacy, safety, and immunogenicity of the product. One such impurity is the presence of empty capsids or capsids with incomplete DNA payloads.

Characterize Adeno-Associated Virus (AAV) with Automated Classification

Cryo-TEM imaging combined with quantitative image analysis tools can be used to directly assess the composition of AAV formulations. Automated particle classification analysis of cry-TEM images, performed with NIS's proprietary machine learning algorithm, enables precise characterization of full and empty capsids. Simultaneously, it is possible to visualize integrity, impurities, and the level of aggregation. Cryo-TEM is the ultimate tool to evaluate combined CQAs; for example, it can be used to assess whether it is empty or full capsids that are more prone to aggregation.

Example cryo-TEM images of full & empty AAV samples (left), and fully automated empty:full capsid analysis (middle, right) | adeno-asscuated virus cryo-TEM imaging
Example cryo-TEM images of full & empty AAV samples (left), and fully automated empty:full capsid analysis (middle, right)

Furthermore, cryo-TEM imaging can be used to obtain 2D class averages and create high resolution 3D reconstructions of AAV particles. This can help identify potential post-translational modifications on AAV capsids, decipher the structural impact of mutations on capsid structure, and help understand the molecular basis of receptor bound AAV or epitope mapping.

eAAV structural analysis with (A) 2.0 Å cryo-EM map and (B) AAV VP3 model | adeno-associated virus 3d structure reconstruction
eAAV structural analysis with (A) 2.0 Å cryo-EM map and (B) AAV VP3 model.

Further, we are able perform negative stain TEM imaging of AAV particles. The sample is stained with a heavy stain, such as uranyl formate, and results in high contrast images suitable for detecting impurities and the integrity of particles, including discreet capsomers.

graphic depicting differences between cryo-tem and negative stain transmission electron microscopy of AAV imaging and characterization
Example image of AAV imaged by cryo-TEM (top) and negative stain (bottom).

Related Viral & VLP Formulations

  • Adenovirus
  • Adenovirus
  • Human Papillomavirus (HPV)
  • Human Papillomavirus (HPV)
  • Lentivirus
  • Lentivirus
  • Vesicular Stomatitis Virus
  • Vesicular Stomatitis Virus

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Frequently Asked Questions

black and white image of adeno-associated virus with cryo-TEM imaging and and insert showing cryo-TEM automated analysis of empty and full capsids | nanoparticle characterization

How many particles do you count, or images do you analyze per sample or grid?

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Can I see an example report for your automated capsid ratio analysis?

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