'Most of the city is evacuating': Gridlock on Alberta highway after evacuation order in Fort McMurray
Four Fort McMurray neighbourhoods were ordered to evacuate on Tuesday as a wildfire gets closer to the city.
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
Four Fort McMurray neighbourhoods were ordered to evacuate on Tuesday as a wildfire gets closer to the city.
Saskatchewan RCMP have revealed that a historic sexual assault investigation has led to the discovery of alleged crimes against children dating back to 2005.
Less than a week after two public sculptures featuring a livestream between Dublin, Ireland, and New York City debuted, 'inappropriate behaviour' in real-time interactions between people in the two cities has prompted a temporary shutdown.
After a final frame that saw the visiting Vancouver Canucks claw their way back and tie the game late, a point shot by Oilers defenceman Evan Bouchard with 38 seconds left (until what seemed like certain overtime) iced the 3-2 victory for Edmonton to knot the series.
Kansas City Chiefs kicker Harrison Butker railed against Pride month, working women, President Biden's leadership during the COVID-19 pandemic and abortion during a commencement address at Benedictine College last weekend.
King Charles III has unveiled the first portrait of the monarch completed since he assumed the throne, a vivid image that depicts him in the bright red uniform of the Welsh Guards against a background of similar hues.
The annual list of Canada's top restaurants in the country was just released and here are the places that made the 2024 cut.
The province has released more information on its plan to break up Alberta Health Services and replace it with four sector-based health agencies.
The Biden administration has told key lawmakers it is sending a new package of more than US$1 billion in arms and ammunition to Israel, two congressional aides said Tuesday.
A team is ready to help an entangled North Atlantic right whale in the Gulf of St. Lawrence.
A $200 reward is being offered by a North Vancouver family for the safe return of their beloved chicken, Snowflake.
Two daughters and a mother were reunited online 40 years later thanks to a DNA kit and a Zoom connection despite living on three separate continents and speaking different languages.
Mother's Day can be a difficult occasion for those who have lost or are estranged from their mom.
YES Theatre Young Company opened its acclaimed kids’ show, One Small Step, at Sudbury Theatre Centre on Saturday.
An Ottawa pizzeria is being recognized as one of the top 20 deep-dish pizzas in the world.
A family of fifth generation farmers from Ituna, Sask. are trying to find answers after discovering several strange objects lying on their land.
A Listowel, Ont. man, drafted by the Hamilton Tigercats last week, is also getting looks from the NFL, despite only playing 27 games of football in his life.
The threat of zebra mussels has prompted the federal government to temporarily ban watercraft from a Manitoba lake popular with tourists.