Some adenovirus-vector-based COVID-19 vaccines, such as the AstraZeneca vaccine, have been associated with rare cases of vaccine-induced immune thrombotic thrombocytopenia (VITT). This blood-clotting issue can, for example, cause a cerebral venous sinus thrombosis. The causes of this rare adverse effect are still under investigation.
Stefan Kochanek, University of Ulm, Germany, and colleagues have analyzed three different lots of the AstraZeneca COVID-19 vaccine. The results have been published as a preprint and have not yet been peer-reviewed. The team used sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) to separate the proteins in the vaccine samples, followed by silver staining. Then they compared the protein bands of the vaccine samples with those of a purified adenovirus vector. The researchers found that the vaccine samples showed more protein bands than the adenovirus vector control. The protein content of a single vaccine dose was determined to be 32 µg, while only 12.5 µg of protein would be expected based on the molecular weight of the adenovirus vector.
The team performed mass-spectrometry (MS) analyses to determine the protein composition of the vaccine. They found that in one lot, about two-thirds of the detected protein were of human origin and one-third of viral origin, while the two other lots consisted of roughly equal amounts of human and viral proteins. The team found several non-structural viral proteins as well as different human proteins derived from the human cell line used in vector production. Heat shock proteins (HSPs), which can affect immune responses, and cytoskeletal proteins were particularly abundant.
According to the researchers, it cannot be ruled out that the detected protein contamination could have adverse effects and potentially promote autoimmune reactions. They propose that the quality control and purification processes for the vaccine should be improved.
- Process-related impurities in the ChAdOx1 nCov-19 vaccine,
Lea Krutzke, Reinhild Roesler, Sebastian Wiese, Stefan Kochanek,
Research Square 2021.
The research has been published as a preprint and has not yet been peer-reviewed. It should not be used to guide clinical practice or health-related behavior.
Also of Interest
- Collection: SARS-CoV-2 Virus
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