![]() The team then used cryo-electron tomography on cells infected with the vaccine to understand the spike's structure on the cells. Testing using recombinant angiotensin-converting enzyme 2 (ACE2) and human monoclonal antibodies confirmed that the spike protein is present in the correct conformation, just like that on the wild-type virus. The cells selected for this study also do not express these receptors and so can act as a suitable substitute for in vitro studies. However, these receptors are generally not present in the types of cells targeted by the ChAdOx1 vaccine, which is administered intramuscularly. The presence of receptors such as ACE2, mainly in the nose, gastrointestinal tract, and lungs, can result in a change in the structure of the spike protein. How the spike protein is processed after vaccination depends both on the receptors and the enzymes produced by the spike-producing cells. Vaccinated mice sera showed about 60-70% of the cells expressed the spike protein. ![]() The researchers used HeLa S3 cells infected with the ChAdOx1 vaccine to detect the presence of spike protein on the cell surface. Image Credit: University of Southampton Characterizing spike protein produced by vaccination Graphic depicting how the protein spikes form on the surface of cells presented with the vaccine. In a recent study, researchers report the characteristics of the spike protein expressed by the vaccine. It has been shown to elicit a robust immune response as well as a T-cell response. The AstraZeneca ChAdOx1 vaccine uses a chimpanzee adenovirus and encodes the full-length spike protein. To enable this, many vaccines include mutations that ensure the spike protein is in the conformation before it fuses with the host cell. Most vaccines aim to elicit a robust immune response, mainly against the receptor-binding domain (RBD) of the spike protein that has several neutralizing epitopes. Sinovac's vaccine uses an inactivated virus that presents the wild-type spike protein. The Moderna and the Pfizer vaccines encode the full-length spike protein with two mutations for stability. The virus spike protein is the main target of vaccines, but vaccines use different methods to target the spike protein. The S1 subunit helps bind the virus to the angiotensin-converting enzyme 2 (ACE2), and the S2 subunit helps with membrane fusion with the host cell. The spike protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which protrudes from the virus envelope, is the key structure responsible for infecting host cells. Artist imaging of protein spike on the surface of cells exposed to the vaccine. ![]()
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