Giving it its Best Shot: Quality Control of Antiviral Vaccines with the Litesizer
The particle size of a vaccine has a considerable influence on its half-life in vivo, as well as on its uptake by antigen-presenting cells. Here we use the Litesizer to characterize the particle size and the zeta potential of vaccines against COVID-19, tick-borne encephalitis and influenza.
The particle size of a vaccine has a significant impact on its immunogenicity. With few exceptions, viruses are nanoparticles ranging in size from 15 to 300 nm. Upon injection, particles in this size range are efficiently taken up by dendritic cells, a class of sentinel cells uniquely endowed with the ability to induce both antibody- and killer cell-mediated immunity (1). In contrast, particles in the micrometer range, such as aluminum salt particles (2), are preferentially taken up by monocytes and macrophages, which predominantly induce an antibody-mediated immune response.
Dynamic light scattering (DLS) is a fast and non-invasive measurement method which elucidates the size distribution of particles in the lower nanometer to lower micrometer size range. This makes DLS a method of choice for the quality control of antiviral vaccines (3).
Here we demonstrate the ability of the Litesizer to determine the particle size of three antiviral vaccines: an aluminum salt-adjuvanted, inactivated tick-borne encephalitis (TBE) vaccine; a cell-based, non-adjuvanted split influenza vaccine; and a SARS CoV 2 mRNA vaccine formulated in lipid nanoparticles. We simulated cold chain disruptions by comparing samples stored in optimal conditions to samples that were heat-treated or submitted to a freeze-thaw cycle.
In addition, ELS measurements were performed to assess the zeta potential of the vaccine particles, giving additional clues on the stability of the preparations.
1. Etchart N, et al. (2001). Dendritic cells recruitment and in vivo priming of CD8+ CTL induced by a single topical or transepithelial immunization via the buccal mucosa with measles virus nucleoprotein. Journal of Immunology 167:384-391.
2. Shardlow E, Mold M & Exley C (2017). From stock bottle to vaccine: elucidating the particle size distributions of aluminum adjuvants using dynamic light scattering. Frontiers in Chemistry 4:48.
3. Slütter B & Jiskoot W (2016). Sizing the optimal dimensions of a vaccine delivery: a particulate matter. Expert Opinion on Drug Delivery 13:167-170.
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