Quebec nurse had to clean up after husband's death in Montreal hospital
On a night she should have been mourning, a nurse from Quebec's Laurentians region says she was forced to clean up her husband after he died at a hospital in Montreal.
Scientists in the U.K. believe they have discovered the reason why some people experienced the very rare side-effect of blood clots after receiving the AstraZeneca COVID-19 vaccine.
The findings, published in the journal Science Advances on Wednesday, reveal that a protein found in blood is drawn to a component of the vaccine, which triggers a reaction from the body’s immune system that can result in 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 vaccine recipient's cells so that they can build an immune response and create antibodies.
The AstraZeneca COVID-19 vaccine uses a cold virus from a chimpanzee, also known as a chimpanzee adenovirus, as the delivery system. This is because it cannot make humans sick – and, because they have not been exposed to it before, they will not have antibodies against it.
Viral vector vaccines modify the delivery virus so that it cannot spread, they simply delivers the instructions for the body’s cells.
By analyzing the chimpanzee adenovirus used by AstraZeneca with cryo-electron microscopy, which allows for molecular-level details to be seen, researchers found that the adenovirus attracts the blood protein known as “platelet factor 4” to it.
Cryo-electron microscopy involves flash-freezing the study subject and then bombarding them with electrons to produce microscope images of individual molecules. Those are then used to reconstruct the structure of the subject in minute detail.
The cryo-electron microscopy image of the chimpanzee adenovirus, which is less than 100 nanometres across, that delivers the Oxford-AstraZeneca vaccine. (Science Advances Journal)
The cryo-electron microscopy image of the chimpanzee adenovirus which delivers the Oxford-AstraZeneca vaccine. (Science Advances Journal)
Platelet factor 4 is implicated in the origins of another clotting event called heparin-induced thrombocytopenia (HIT), which causes changes to the blood that may cause a clot to form in the blood vessels.
Researchers posit that the body begins to attack the platelets that are attached to the adenovirus, after mistaking it as part of the foreign virus. Then, when antibodies are released into the bloodstream to attack, they clump together with the platelet factor 4 and can form a dangerous blood clot known as vaccine-induced thrombotic thrombocytopenia or VITT.
Because that sequence of events in the body is so specific, it may explain why the development of blood clots after receiving the vaccine is such a rare phenomenon.
The U.K. findings echo a Canadian study conducted by researchers at McMaster University in Hamilton, Ont., and published this July in the scientific journal Nature.
In the Canadian study, researchers analyzed blood samples from five patients with VITT and compared them to blood samples of 10 patients with HIT and 10 samples from healthy individuals.
Looking at the amino acids of the interaction between the VITT antibodies and platelet factor 4 protein, researchers found eight specific amino acids on the platelet protein that were identical to the binding site of HIT, which they believe could explain the similar patterns in how the blood clots form after vaccination.
However the U.K. study was able to render the highest resolution of the adenovirus used in the AstraZeneca COVID-19 vaccine to date, allowing them to better understand its primary cell attachment proteins and its structure.
VITT has been linked to at least one death in Canada after an Ontario man received the AstraZeneca vaccine in May, and to 73 deaths out of close to 50 million doses of AstraZeneca administered in the U.K.
The Public Health Agency of Canada’s National Advisory Committee of Immunization stopped recommending AstraZeneca’s COVID-19 vaccine as a second dose option after some Canadian recipients reported blood clots in the spring of 2021.
Researchers in the U.K. hope their study findings can be used to improve future vaccines and reduce the risk of blood clots.
-----
With files from CTVNews.ca writer Brooklyn Neustaeter
On a night she should have been mourning, a nurse from Quebec's Laurentians region says she was forced to clean up her husband after he died at a hospital in Montreal.
A North Bay, Ont., lawyer who abandoned 15 clients – many of them child protection cases – has lost his licence to practise law.
Members of the Bank of Canada's governing council were split on how long the central bank should wait before it starts cutting interest rates when they met earlier this month.
Brad Marchand scored twice, including the winner in the third period, and added an assist as the Boston Bruins downed the Toronto Maple Leafs 4-2 to take a 2-1 lead in their first-round playoff series Wednesday
Cuba's foreign affairs minister has apologized to a Montreal-area family after they were sent the wrong body following the death of a loved one.
Mounties in Nanaimo, B.C., say two late-night revellers are lucky their allegedly drunken antics weren't reported to police after security cameras captured the men trying to steal a heavy sign from a downtown business.
The federal government's proposed change to capital gains taxation is expected to increase taxes on investments and mainly affect wealthy Canadians and businesses. Here's what you need to know about the move.
Canada's Deputy Prime Minister Chrystia Freeland was among the 1,700 delegates attending the two-day First Nations Major Projects Coalition (FNMPC) conference that concluded Tuesday in Toronto.
The daughter of a New Brunswick man recently exonerated from murder, is remembering her father as somebody who, despite a wrongful conviction, never became bitter or angry.
A property tax bill is perplexing a small townhouse community in Fergus, Ont.
When identical twin sisters Kim and Michelle Krezonoski were invited to compete against some of the world’s most elite female runners at last week’s Boston Marathon, they were in disbelief.
The giant stone statues guarding the Lions Gate Bridge have been dressed in custom Vancouver Canucks jerseys as the NHL playoffs get underway.
A local Oilers fan is hoping to see his team cut through the postseason, so he can cut his hair.
A family from Laval, Que. is looking for answers... and their father's body. He died on vacation in Cuba and authorities sent someone else's body back to Canada.
A former educational assistant is calling attention to the rising violence in Alberta's classrooms.
The federal government says its plan to increase taxes on capital gains is aimed at wealthy Canadians to achieve “tax fairness.”
At 6'8" and 350 pounds, there is nothing typical about UBC offensive lineman Giovanni Manu, who was born in Tonga and went to high school in Pitt Meadows.
Kevin the cat has been reunited with his family after enduring a harrowing three-day ordeal while lost at Toronto Pearson International Airport earlier this week.