McMaster researchers identify how VITT occurs

PICTURE: From left to right: Ishac Nazy, Angela Huynh, John Kelton, Donald Arnold, Mercy Daka view After

Credit: James Smith / McMaster University

Hamilton, ON (July 7, 2021) – A team of researchers from McMaster University recently discovered how, exactly, COVID-19 vaccines that use adenoviral vectors trigger a rare but sometimes fatal blood clotting reaction called immune-induced thrombotic thrombocytopenia by the vaccine or VITT.

The results will put scientists on the path to finding a way to better diagnose and treat VITT, possibly prevent it and potentially make vaccines safer.

The researchers’ article was expedited for publication today by the prestigious journal Nature in his expedited overview of the article due to the importance of research.

“Our work also answers important questions about the link between antibodies and coagulation,” said Ishac Nazy, principal investigator and corresponding author of the study. He added that this would have both diagnostic and therapeutic implications.

Nazy is the Scientific Director of the McMaster Platelet Immunology Laboratory and Associate Professor of Medicine at the Michael G. DeGroote School of Medicine at McMaster.

COVID-19 vaccines using adenoviral vectors, such as those from AstraZeneca and Johnson and Johnson, are associated with the bleeding disorder VITT caused by unusual antibodies to blood platelets that are triggered by the vaccine.

The study shows, at the molecular level, how these unusual antibodies adhere to components of blood platelets, causing them to trigger clots.

“The antibodies adhere to the platelet protein called platelet factor 4 (PF4) in a very unique and specific orientation, which allows them to align with other antibodies and platelets in the precise formation which leads to a vicious self-cycle. maintained from clotting events, “says Nazy.

“These pathogenic aggregates quickly activate platelets, creating a very intense clotting environment in patients,” he added.

The dangerous reaction to adenoviral vector vaccines has occurred in one in 60,000 people receiving the vaccine in Canada.

“The intention of our study was to gain a better understanding of how the severe clots that characterize VITT develop,” said Donald Arnold, study co-investigator and medical co-director of the McMaster Platelet Immunology Laboratory.

“A basic principle of medical care is to understand how the disorder occurs and in doing so, to develop better treatments.”

John Kelton, study co-investigator and McMaster Platelet Immunology Laboratory co-medical director, added: “We think this study is important because it clarifies how coagulation occurs, and because we were able to identify the molecules involved. .

“The next step is to develop a rapid diagnosis and an accurate test to diagnose VITT. Our major interest now is to get upstream of how clots occur to prevent them from occurring.”

Current rapid tests give false negative results, and testing relies on longer tests to confirm VITT. This study now explains why rapid tests frequently fail and enables new strategies to improve diagnostic testing.

The researchers altered the molecular composition of the PF4 protein and, using this technology, were able to identify the binding region on the protein.


The research team included Angela Huynh, a research scientist at the McMaster Platelet Immunology Lab, and Mercy Daka, a graduate student in the Department of Biochemistry and Biomedical Sciences at McMaster.

The researchers thanked organizations that support the research, including the Public Health Agency of Canada, the Canadian Institutes of Health Research (CIHR) and the Ontario Ministry of Health.


A link to the document can be found here: https: //fhs.mcmaster.California/platelet immunology /updates.html

An illustration of VITT, a photo of the authors and a b roll in the platelet lab are available for download at https: //macdrive.mcmaster.California/re/d7054b21b11a4829b4db /

For information, please contact:

Veronique mcguire

Media relations

Faculty of Health Sciences

McMaster University


[email protected]

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