Cryo-TEM is a powerful analytical tool for any viral vector-based gene therapy or vaccine in all phases of the drug and vaccine development process.
Viral vectors, including prominent ones such as vesicular stomatitis virus (VSV), Newcastle disease virus (NDV), influenza virus (IFV), adenovirus (AdV), and poxvirus, can be used for gene replacement, as well as their genomes can be modified to contain one or more foreign genes encoding the targeted antigens of interest, which in turn induces a robust humoral and cellular immunity against human diseases. This approach has gained significant attention in recent years, especially with the development of COVID-19 vaccines like those from AstraZeneca and Janssen, both AdVs.
Viral vector-based therapeutics and vaccines are generally grown in cell culture and subsequently purified to ensure that the product is free of contaminants. Adjustments to the production process, addition of excipients, scale-up procedures, and storage conditions can significantly impact the efficacy, stability, and overall success of viral vector-based vaccines. During cryo-TEM, virus particles are preserved in a near-native hydrated state. Cryo-TEM is an important tool to assess size, morphology, aggregation status, purity, and structural integrity of a modified viral vector and is therefore crucial not only in development but also in quality control and stability assessments.
Visualizing viral vector formulations on a per-particle basis, from cryo-TEM images to 3D structure determination.
Whether your viral particle is icosahedral, enveloped, or non-enveloped, NIS offers multiple analyses to better understand your virus-based formulation beyond purely visualizing the particles.
Fraction counting analysis can be used to categorize and quantify morphological features in and between formulations; it helps researchers better understand the efficacy, safety, and immunogenicity of their formulation. To optimize virus-based vaccine design, cryo-TEM or TEM images can be used for example to quantify the fraction of non-intact versus intact virus particles in a sample, or the number of full, empty, and partially filled capsids, or help evaluate antigen distribution on the particle surface by categorizing particles that are densely decorated, sparsely decorated, or not decorated with surface glycoprotein spikes.
NIS also offers semi-automated tracing and size distribution analysis of particles in cryo-TEM or TEM images, a quality attribute important for assessing batch-to-batch variability, formulation and process development, and process validation.
Another analytical tool NIS provides is 2D class averaging analysis. For viral vectors that are homogeneous in size and shape, cryo-TEM and TEM images of virus particles can be aligned and class averaged in order to better understand structural details of the capsid, including domain structures, in 2D.
For virus particles that are homogeneous in size and morphology, cryo-TEM images can also be used to determine the full 3D structure of a virus at high resolution. A 3D structure can provide information on for example antibody binding sites (epitope mapping), if and how mutations affect the capsid structure, receptor binding sites, and possibly post-translational modifications.
When obtaining a high resolution 3D reconstruction is challenging due to structural and compositional variation from one viral particle to another, NIS offers cryo-electron tomography (cryo-ET). In this technique, a low resolution 3D structure is reconstructed from a series of 2D projection images, which can then provide information on for example native states of viruses without intrinsic symmetry (eg retroviruses), or can be used to assess possible interactions between viral vectors and adjuvant, if present.
NIS can work with viral vectors that require safety level BSL-1 or BSL-2.