Why do blood clots form after the AstraZeneca vaccine?

Toronto-British scientists believe that after vaccination with the AstraZeneca COVID-19 vaccine, some people have discovered why they experienced the very rare side effects of blood clots.

Investigation result, Published in the journal Science Advances On Wednesday, proteins found in the blood are attracted to the components of the vaccine, which causes a reaction from the body’s immune system, revealing that it can cause blood clots.

The AstraZeneca vaccine, like other viral vector vaccines, uses a safe virus as a “host” to deliver genetic information about the COVID-19 spike protein to the cells of the vaccine recipient and build an immune response. Allows you to make antibodies.

The AstraZeneca COVID-19 vaccine uses a cold virus from chimpanzees (also known as chimpanzee adenovirus) as a delivery system. This is because it can’t make humans sick – and they don’t have antibodies to it because they haven’t been exposed to it before.

Viral vector vaccines simply modify the delivery virus to prevent it from spreading and deliver instructions to the cells of the body.

By analyzing the chimpanzee adenovirus used by AstraZeneca with a cryo-electron microscope and confirming molecular details, we discovered that adenovirus attracts a blood protein known as “platelet factor 4”. ..

Cryogenic electron microscopy involves flash freezing the subject and irradiating it with electrons to create microscopic images of individual molecules. Then use them to reconstruct the structure of interest in detail.

Cryogenic electron micrographs of chimpanzee adenovirus delivering the Oxford-AstraZeneca vaccine. (Science Advances Journal)

Platelet factor 4 is involved in the cause of another coagulation event called heparin-induced thrombocytopenia (HIT). This can cause changes in the blood and form blood clots in the blood vessels.

Researchers believe that after mistaken adenovirus for part of a foreign virus, the body begins to attack the platelets attached to the adenovirus. Then, as the antibodies are released into the bloodstream and attack, they can aggregate with platelet factor 4 and form a dangerous thrombus known as vaccine-induced thrombocytopenia or VITT.

The sequence of events in the body is so specific that it may explain why the development of blood clots after vaccination is a very rare phenomenon.

UK survey results Echo Canadian studies Conducted by researchers at McMaster University in Hamilton, Ontario, in July this year Scientific journal nature..

In a Canadian study, researchers analyzed blood samples from 5 patients with VITT and compared them with blood samples from 10 patients with HIT and 10 samples from healthy individuals.

By examining the amino acids in the interaction of the VITT antibody with the platelet factor 4 protein, researchers found eight specific amino acids on the platelet protein that were identical to the HIT binding site. Platelets are formed after vaccination.

However, a British study provided the highest resolution of adenovirus previously used in the AstraZeneca COVID-19 vaccine, providing a better understanding of primary cell-attached proteins and their structure.

VITT is linked to at least One person died in Canada After a man in Ontario was vaccinated with AstraZeneca in May, 73 of the nearly 50 million doses of AstraZeneca given in the UK died.

Public Health Agency of Canada National Advisory Board on Immunization I stopped recommending AstraZeneca’s COVID-19 vaccine as a second dose option after some Canadian recipients reported thrombosis in the spring of 2021.

British researchers hope that their findings can be used to improve future vaccines and reduce the risk of blood clots.

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Using files from Brooklyn Neustaeter, writer for CTVNews.ca