Amino acids targeted by antibodies in the blood of some people who received AstraZeneca's COVID-19 vaccine offer clues to the source of the rare blood clots associated with the shot, according to a peer-reviewed study published July 7 in Nature.
For the study, researchers from McMaster University in Ontario, Canada, analyzed blood from five people ages 35 to 72 who developed vaccine-induced immune thrombotic thrombocytopenia, or VITT, after getting a dose of AstraZeneca's vaccine. They then compared the people's platelet and clotting responses to 10 people who had heparin-induced thrombocytopenia — low blood platelets caused by the blood-thinning drug heparin — and 10 healthy people.
VITT is an autoimmune reaction in which antibodies bind with unusual strength to a blood component called platelet factor 4, according to The Wall Street Journal. The researchers mapped out where VITT antibodies clung to the platelet factor 4 and found that they reliably targeted eight surface amino acids.
"That's where the forest fire starts. These amino acids are super important to VITT but not to [heparin-induced thrombocytopenia]," Ishac Nazy, PhD, a McMaster University researcher who was an author of the study, told the Journal.
Experts told the Journal the study findings could help physicians rapidly test for and treat the unusual blood-clotting.
The blood clots seen in rare instances after AstraZeneca's vaccine involve a rare combination of low blood platelets and blood clots. VITT has occurred in one to two people per 100,000 first doses of AstraZeneca's vaccine in the U.K., the Journal reported.
Find the full study here.